Nanoengineered Enzyme Immobilization: Toward Biomedical, Orthopedic, and Biofuel Applications

Abstract

Enzyme immobilization is vital for enhancing catalytic stability, reusability, and efficiency in both industrial bioprocesses and medical therapies. Integrating nanotechnology into immobilization strategies offers unique advantages, including high surface area, tunable surface chemistry, and biocompatibility, which collectively improve enzyme performance. This review summarizes recent progress in nanoengineered immobilization using materials such as silica, gold nanoparticles, polymers, magnetic nanoparticles, carbon-based structures, and hydrogels. It highlights their roles in enabling functional enhancementsthermal and pH stability, substrate specificity, and long-term activitythrough diverse designs like core–shell structures and mesoporous networks. Biomedical applications span biosensors, diagnostics, and enzyme delivery, with growing interest in orthopedic uses, such as enzyme-functionalized scaffolds for bone regeneration. In parallel, nanomaterial-based systems are advancing biofuel production by improving enzyme efficiency and sustainability. Remaining challenges include cost, scalability, and enzyme leaching. Future work should focus on AI-driven support selection, green material design, and robust nanobiocatalyst systems for next-generation applications.

1. Introduction

In the field of enzyme catalysis, nanoengineered enzyme immobilization has emerged as a transformative research direction, significantly advancing biocatalysis in various fields such as biomedicine and biofuel production. Enzymes, as highly efficient biological catalysts, hold immense potential in various industrial and biotechnological applications. However, their inherent sensitivityinstability to changes in operational conditions such as temperature, pH, and organic solventsalong with challenges in recovery and reuse, severely limit their widespread application. Traditional enzyme usage methods (i.e., free enzymes) are typically confined to batch processes and have limitations in terms of reusability, leading to high operational costs. To overcome these limitations and fully harness the catalytic potential of enzymes, the technology of immobilizing enzymes on solid carriers has emerged. This strategy enhances enzyme stability, catalytic efficiency, and reusability by providing a protected microenvironment. In recent years, the emergence of nanomaterials has opened up unprecedented opportunities for enzyme immobilization, as they possess unique size effects and surface properties, such as high specific surface area, good biocompatibility, and tunable functionality. These properties enable nanomaterials to optimize enzyme performance, paving the way for the development of more robust and cost-effective biocatalytic systems.

This review aims to provide a comprehensive overview of the latest advancements in the field of nanoengineered enzyme immobilization, with a particular focus on its transformative impact in biomedical applications and biofuel production. We will systematically explore various nanomaterials used for enzyme immobilization, including silica nanoparticles, gold nanoparticles, polymers, magnetic nanoparticles, carbon-based materials (such as graphene and carbon nanotubes), and hydrogels. These materials are favored for their unique properties, such as high surface area, biocompatibility, and tunable functionality, which can optimize enzyme performance. Additionally, we will delve into various structural designs, such as core–shell nanoparticles, mesoporous materials, and nanofiber networks, emphasizing their critical role in enhancing enzyme stability, catalytic efficiency, and reusability through optimized microenvironments and controlled spatial configurations. This review will also provide a detailed overview of common immobilization methods, including physical adsorption, covalent bonding, encapsulation, cross-linking, and affinity binding, and analyze their respective impacts on enzyme function and stability.

The significant functional enhancements achieved through nanoengineered enzyme immobilization are a key focus of this review, including improved thermal and pH stability, enhanced reusability, greater substrate specificity, and overall increased catalytic efficiency. These advancements have driven numerous applications in the biomedical field, such as high-sensitivity biosensors, advanced diagnostic devices, precise therapeutic enzyme delivery systems, and wearable monitoring devices (Figure ). Additionally, this technology has greatly benefited biofuel production by enhancing the efficiency and sustainability of bioethanol and biodiesel synthesis. Despite these breakthroughs, challenges such as cost-effectiveness, potential enzyme leakage, and the complexity of scaling up remain. Future research should focus on developing novel nanocomposites, integrating artificial intelligence and green design principles, and leveraging advanced computational modeling to overcome current limitations. By addressing these challenges and employing interdisciplinary approaches, nanoengineered enzyme immobilization holds promise for sustainable development, driving innovation across various industrial and biomedical fields by providing more efficient, stable, and multifunctional biocatalysts.

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Nanoengineered enzyme immobilization: enhancing multifunctional applications of biocatalysis.

1.1. Materials for Nanoengineered Enzyme Immobilization

The selection of enzyme immobilization carriers has a decisive impact on the performance of immobilized enzyme systems. , Ideal carrier materials must possess key characteristics such as high specific surface area, good biocompatibility, excellent stability, and functionalizable surfaces. In recent years, nanomaterials have demonstrated significant advantages in the field of enzyme immobilization due to their unique size effects and surface properties. − These materials include inorganic nanoparticles (such as silica, magnetic iron oxide), carbon-based materials (such as graphene, carbon nanotubes), and polymeric nanocarriers (such as chitosan nanoparticles) (Figure ), which not only provide high enzyme loading capacity but also enable directed enzyme immobilization through surface modification. Magnetic nanoparticles, in particular, are convenient for separation and recovery. These nanocarriers not only significantly enhance enzyme stability and reusability but also optimize enzyme–substrate interactions through precise interface engineering design, thereby improving catalytic efficiency. Current research efforts are increasingly focused on developing novel nanocomposites with multilevel pore structures, core–shell configurations, and stimulus-responsive properties to further expand the application potential of immobilized enzymes in fields such as biomanufacturing and biosensing.

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Six advanced materials used in nanotechnology and biomedicine.

1.2. Silica Nanoparticles

Silica nanoparticles are the most frequently used immobilization material due to their chemical stability, high surface area, and functionalizability. Compared with other materials, silica nanoparticles are biocompatible, nontoxic, and less costly. A high surface area of silica nanoparticles has the potential to increase the loading of enzymes, resulting in increased enzyme activity and stability. In addition, their surface can be easily functionalized with various functional groups, such as amino, carboxyl, or epoxy groups, that enhance the covalent attachment of the enzyme and support, stabilizing the enzyme under various conditions. The mesoporous property of silica nanoparticles is particularly beneficial for enzyme immobilization in a confined environment, which protects them from environmental stress factors such as high pH or temperature. − Moreover, silica nanoparticles can be easily integrated into a bioreactor system for continuous catalysis, where enzyme recyclability and recovery are of paramount concern.

1.3. Gold Nanoparticles

Gold nanoparticles (AuNPs) have become one of the most attractive carrier materials in the field of enzyme immobilization due to their excellent physical and chemical properties. , First, AuNPs exhibit good biocompatibility, demonstrating broad potential in various applications such as biosensing, catalysis, and biomedicine. Second, the ease of functionalizing the AuNP surface is one of its core advantages, particularly through the use of thiol (−SH) groups to achieve stable surface modification. The thiol groups present in enzyme molecules can form stable covalent bonds with thiol-modified AuNPs, thereby achieving robust enzyme immobilization and significantly reducing the risk of enzyme desorption and inactivation. Additionally, the excellent electrical conductivity of AuNPs provides an ideal immobilization microenvironment for enzymes involved in electron transfer processes, helping to maintain or even enhance their catalytic activity.

More importantly, AuNPs typically possess extremely high specific surface areas, enabling them to load more enzyme molecules per unit volume and significantly enhance the catalytic efficiency and yield of enzyme systems. − Their structural diversity also provides broader design and control possibilities for enzyme immobilization. AuNPs with different morphologies exhibit distinct optical and physical properties, which significantly influence their performance in enzyme carrier applications. For example, traditional spherical AuNPs are widely used as basic carrier materials due to their simple synthesis and size stability. Gold nanorods, with their tunable plasmonic resonance properties, exhibit outstanding performance in enhancing optical signals and charge transfer; while anisotropic structures such as gold nanodiamonds provide more possibilities for regulating the spatial conformation of enzyme molecules.

In terms of structural design, AuNPs can be functionalized through surface coating or composite formation to create multifunctional nanostructures. For instance, gold nanorods coated with a silver layer can further modulate their optical and electronic properties; iron oxide core–gold shell structures combine the dual advantages of magnetic properties and noble metal activity, facilitating recovery while maintaining excellent catalytic capability; and silica–gold composite nanostructures integrate the high stability of an inorganic core with superior surface functionality. Additionally, gold nanowell structures and “spiky ball-shaped” nanocap structures with unique surface roughness can significantly increase enzyme binding sites and may regulate enzyme conformation through spatial confinement, thereby enhancing functional stability and catalytic selectivity.

Highly symmetrical gold nanocrystal structures, such as tetrahedra, octahedra, cuboctahedra, and cubic nanoparticles, offer the potential for precise enzyme arrangement and directed immobilization due to their regular crystal faces and controllable sizes. Novel morphologies such as gold–silver nanocages, silver cubes, and ring-shaped nanostructures prepared using silver nanotemplates further expand the application scope of metal nanocomposites in enzyme immobilization. These diverse morphologies not only determine the physicochemical properties of gold nanoparticles themselves but also exert a profound influence on enzyme loading capacity, stability, and catalytic performance, enabling researchers to flexibly design and optimize the most suitable nanocarrier platforms based on the target enzyme type and specific application requirements.

1.4. Polymers

Polymers such as chitosan, polyethylene glycol (PEG), and poly­(vinyl alcohol) (PVA) have also been explored for enzyme immobilization. − Polymers are extremely versatile since they can be made to possess tailor-made properties such as biodegradability, flexibility, and modifiability. They are often blended with other nanomaterials to improve the stability and functionality of immobilized enzymes. Chitosan, a chitin-derived biopolymer, is widely used since it is nontoxic, biocompatible, and has strong physical interactions with enzymes. The synthetic polymer PEG is also widely used to improve the stability and solubility of enzymes and prevent enzyme aggregation. Because they are biodegradable, these polymers are widely utilized in biomedical applications as drug delivery systems or as enzyme-based therapeutic interventions.

1.5. Magnetic Nanoparticles

Magnetic nanoparticles (MNPs) demonstrate unique advantages in the field of enzyme immobilization, particularly due to their ease of manipulation via external magnetic fields, which greatly facilitates the recovery and reuse of immobilized enzymes. − This magnetic responsiveness enables depleted or spent immobilized enzymes to be rapidly and efficiently separated from the reaction system, significantly simplifying the enzyme recovery process and effectively promoting enzyme reuse, thereby greatly enhancing the sustainability and economic benefits of the biocatalytic process. To further optimize their performance as enzyme carriers, magnetic nanoparticles are typically composite with other materials, such as silica or polymers. This composite strategy not only fully utilizes the high specific surface area provided by these auxiliary materials to effectively increase enzyme loading capacity but also retains the inherent ease of separation of magnetic nanoparticles. In large-scale industrial biocatalytic applications, the ability to recover enzymes from the reaction medium using a magnetic field is particularly important, as it significantly reduces the costs and time associated with enzyme recovery and separation, thereby greatly improving industrial production efficiency. Additionally, the surface of magnetic nanoparticles can be conveniently functionalized with various active functional groups, which promote stable binding between enzymes and carriers, thereby effectively enhancing the stability of immobilized enzymes under actual working conditions. Therefore, magnetic nanoparticles and their composite materials provide a robust solution for constructing efficient, recyclable, and sustainable enzyme biocatalytic systems.

1.6. Carbon-Based Materials: Graphene and Carbon Nanotubes (CNTs)

Carbon nanomaterials, particularly graphene and carbon nanotubes (CNTs), are highly sought after due to their unique superior properties. − These materials are primarily valued for their exceptional conductivity, large specific surface area, and outstanding mechanical stability, making them ideal carriers for enzyme immobilization. Graphene, a two-dimensional lattice sheet composed of carbon atoms, provides an extremely conductive surface. This high conductivity is crucial for maximizing electron transfer rates in enzyme-based bioelectrochemical devices (such as biosensors and biofuel cells), ensuring efficient signal response or energy conversion. Carbon nanotubes, which can be viewed as rolled-up graphene sheets, also possess an extremely high surface area-to-volume ratio, making them excellent candidates for enzyme immobilization. The tubular structure of carbon nanotubes offers a unique advantage: the possibility of enzyme encapsulation. This encapsulation method not only effectively protects enzymes from external environmental influences, enhancing their stability, but the inherent high conductivity of carbon nanotubes also facilitates electron transfer between the enzyme active site and the electrode, maintaining or even enhancing the enzyme’s catalytic activity. These characteristics of carbon-based materials, including their inherent flexibility, make them highly promising in a wide range of applications, such as in the production of biofuels and environmental pollution control, where they demonstrate significant potential as enzyme immobilization carriers.

1.7. Hydrogels

Hydrogels are cross-linked polymer networks that are water swollen and can retain a large amount of water without compromising their structure. − Hydrogels are extremely useful for enzyme immobilization because they provide a humid environment that mimics the natural environment in which enzymes typically function. This is particularly beneficial for dehydrating or osmotically sensitive enzymes. In addition to their ability to hold moisture, hydrogels are customized for the controlled delivery of enzymes and thus have suitable applications as potential candidates for use in enzyme delivery systems. Hydrogels can, for example, be programmed to discharge enzymes on demand through external signals such as variations in pH or temperature. This versatility enhances the efficacy and specificity of therapies involving enzymes.

2. Nanoimmobilized Structure

The structural organization of enzymes on nanomaterial supports plays a pivotal role in determining their catalytic efficiency, stability, and reusability. − The spatial configuration and surface architecture of the immobilized enzyme system can profoundly influence enzyme–substrate interactions, thereby modulating enzymatic activity and overall biocatalytic performance. To optimize these functional parameters, a wide range of nanostructured materials have been engineered. The selection of an appropriate immobilization architecture is typically guided by the specific demands of the intended applicationincluding the nature of the catalytic reaction, operational environment, and desired product characteristics. Several representative nanoimmobilization strategies have been developed, each imparting distinct effects on enzyme conformation, accessibility, and turnover rates.

2.1. Core–Shell Nanoparticles

Core–shell nanoparticles consist of a central “core” material, typically a metal or semiconductor, encapsulated with an exterior “shell” of a biocompatible material, usually silica or polymers (Figure a). − Core–shell design offers a unique advantage in immobilizing enzymes in that it benefits from the core material’s stability and functionality as well as the shell’s biocompatibility and ability to bind enzymes. The core of these nanoparticles can increase the mechanical strength and stability of the immobilized enzyme, and the surface can be designed to facilitate enzyme attachment through covalent bonding, electrostatic attraction, or entrapment. Core–shell nanoparticles also provide a protected environment for enzymes, which shields them from harsh reaction conditions, such as high temperature, pH fluctuations, and oxidative stress, that can lead to enzyme denaturation. In addition, the core–shell structural design allows for the customization of the properties of the core and shell materials. The core, for example, can be chosen to provide specific optical or magnetic properties, whereas the shell can be designed for increased enzyme loading and activity in catalysis. This offers the flexibility of making core–shell nanoparticles particularly adaptable for application in diagnostics, biosensors, and therapeutic release of enzymes.

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(a) Preparation process of magnetic microspheres with a multilayer encapsulation structure. Reprinted with permission from ref . Copyright 2021 Elsevier. (b) Composite structure with mesoporous material loaded onto the surface of magnetic nanoparticles (MNPs). Reprinted with permission from ref . Copyright 2021 Instituto Internacional de Ecologia. (c) Stepwise layer-by-layer (LBL) process for enzyme immobilization in a “fully liquid microfluidic chip”. Reprinted with permission from ref . Copyright 2022 Wiley. (d) Schematic diagram of an electrospinning system. Reprinted with permission from ref . Copyright 2023 Wiley.

2.2. Mesoporous Nanomaterials

Mesoporous materials are defined by their ordered pore structure, with pore sizes usually in the range of 2–50 nm (Figure b). ,− These materials, for example, mesoporous silica, have a high surface area combined with porosity so that they facilitate the effective encapsulation and immobilization of enzymes. The ordered porosity also facilitates the controlled release of enzymes, with the enzymes trapped inside pores whose size restricts their movement, preventing premature breakdown. Mesoporous nanomaterials are particularly applicable for high-density enzyme loading. The wide surface area of these materials can immobilize a relatively high density of enzymes, leading to increased catalytic efficiency. Their uniform pore architecture also ensures a more homogeneous distribution of enzymes, inhibiting uneven activity within the system. − Mesoporous silica nanoparticles, for example, have been widely used to immobilize enzymes for the synthesis of biofuel and bioremediation purposes, where high stability and optimal enzyme activity under harsh conditions are needed. Mesoporous materials are very versatile, with surface functionalization that can also optimize enzyme attachment, stability, and catalytic activity.

2.3. Layer-By-Layer (LBL) Assemblies

Layer-by-layer (LBL) assembly is a versatile and widely adopted technique for the sequential deposition of oppositely charged speciestypically polyelectrolytes, nanoparticles, and biomoleculesonto a substrate, such as nanoparticles or planar surfaces (Figure c). − This approach enables precise control over the architecture, composition, and thickness of the resulting multilayered structures, making it particularly attractive for enzyme immobilization. LBL-based immobilization affords several advantages. It facilitates the formation of highly ordered, self-assembled thin films capable of encapsulating multiple enzyme layers, while also providing tunable microenvironments that can enhance enzyme stability and activity. The incorporation of protective polymeric barriers within the multilayer architecture can shield enzymes from external stressors such as extreme pH or temperature, thereby extending their operational lifespan. Moreover, the modularity of the LBL process allows for the integration of various functional componentsincluding nanomaterials and responsive polymerstailored to specific catalytic or sensing needs. Importantly, LBL assemblies are also amenable to the design of stimuli-responsive systems for controlled enzyme release. By engineering degradable or dissociable layers, enzymes can be released in a temporally and environmentally regulated manner, which is particularly beneficial in applications such as biosensing, targeted drug delivery, and enzyme-based therapeutics. −

2.4. Nanostructured Films and Membranes

Nanostructured membranes and films are also possible structures for immobilizing enzymes. Nanostructured films are thin films of nanomaterials such as carbon nanotubes (CNTs), graphene, or polymers that serve as substrates for enzyme binding. ,− The surface space supplied by the nanostructured surface is large enough for enzyme immobilization, and the physical properties of the films can be regulated to tailor enzyme stability and activity. Nanostructured films are particularly useful in continuous flow systems, such as bioreactors or biosensors, where the immobilized enzymes are exposed to continuous substrate or reactant flow. The high surface area of the films can facilitate the smooth interaction of enzymes with the substrate, leading to increased catalytic rates. Films can be rendered flexible and lightweight, which means that films can be used in wearable devices or portable biosensors. The combination of nanostructured films with other nanomaterials, such as gold or silver nanoparticles, can also enhance the stability and functionality of immobilized enzymes. For example, gold nanoparticles have the ability to introduce a more conductive nature to the film, allowing better electron transfer in bioelectrochemical applications.

2.5. Nanofiber Networks

Nanofiber networks, be they derived through electrospinning or otherwise, are web-like networks of nanofibers (Figure d). − The networks are open pore materials with large surface areas and are ideal for enzyme immobilization. Nanofibers can be made of extremely diverse materials, including polymers, carbon materials, and silica. The fibrous network architecture is able to encapsulate enzymes in a more efficient way without sacrificing flexibility and scalability for process suitability at an industrial scale. Cross-linked fibers facilitate enzyme–substrate interactions, making the catalytic efficiency even better. The network porosity also allows the substrates and products to diffuse easily, resulting in high reaction rates. Nanofiber networks are used for certain applications in tissue engineering, drug delivery, and biosensing where immobilization of the enzyme in three-dimensional space is needed. Nanofibers are biocompatible and possess a high loading capacity for enzymes; hence, such networks can be used for various applications in biomedicine. −

3. Methods of Enzyme Immobilization

The immobilization of enzymes on solid supports is an important step toward enhancing their stability, reusability, and overall catalytic efficiency. The method of immobilization can also significantly influence the orientation of the enzyme, its activity, and its reusability. Several methods have been developed for enzyme immobilization, each with specific advantages and limitations depending on the nature of the enzyme, the support material, and the intended application. Here, we will outline the most common methods of enzyme immobilization, describing the principles, advantages, disadvantages, and impacts on enzyme activity.

3.1. Physical Adsorption

Physical adsorption is one of the most straightforward and widely employed techniques for enzyme immobilization, relying on noncovalent interactionssuch as van der Waals forces, hydrogen bonding, and electrostatic attractionsbetween the enzyme and the surface of a support material (Figure a). This method does not involve chemical modification of the enzyme or the support, making it a simple, cost-effective, and broadly applicable approach. Among its key advantages, physical adsorption offers high procedural simplicity and versatility, allowing a wide range of enzymes and support materials to be used without the need for complex chemistry. Furthermore, because the enzyme retains its native conformation, there is minimal risk of structural denaturation, thereby preserving its catalytic activity. The immobilization process is typically conducted under mild conditions (e.g., near-neutral pH, ambient or low temperatures), which helps to maintain enzyme stability. −

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(a) A method for immobilizing lipase on the surface of a solid carrier via physical adsorption. Reprinted with permission from ref . Copyright 2024 ACS. (b) The covalent immobilization process of d-allulose 3-epimerase (DAE). Reprinted with permission from ref . Copyright 2024 Elsevier. (c) Schematic diagram of enzyme encapsulation confined within a semipermeable matrix or membrane. (d) The process of oxidizing cyclohexanol (CHL) to ε-caprolactone (ECL) in a microaqueous medium using enzyme immobilization and enzyme coupling technology. Reprinted with permission from ref . Copyright 2024 ACS.

However, physical adsorption also presents several limitations. The weak and reversible nature of the binding interactions can result in enzyme desorption, particularly under harsh operational conditions such as elevated temperature, extreme pH, or high ionic strength. Additionally, this method provides little control over enzyme orientation on the support surface, which can lead to suboptimal active site accessibility and reduced catalytic performance. Despite these drawbacks, physical adsorption remains a useful method for applications where ease of preparation and moderate stability are sufficientsuch as in batch bioreactors, disposable biosensors, or preliminary screening studies.

3.2. Covalent Bonding

Covalent bonding involves the formation of stable chemical bonds between the enzyme and support material, typically through surface functional groups (e.g., amino, carboxyl, or epoxy) (Figure b). The immobilization process results in more robust immobilization than physical adsorption since the covalent bonds are far more stable and less likely to break under extreme conditions. Strong stable attachment: Stable strong covalent attachment provides a firm, stable enzyme–support interaction appropriate for repeated use applications or use under harsh conditions. Increased stability of the enzyme: Stable attachment increases the resistance of the enzyme to denaturation, which is beneficial for use in industry under high-temperature or harsh solvent conditions. Controlled orientation: Covalent attachment has a preference for orienting the enzyme such that it might be made more catalytically efficient by placing the enzyme in an active conformation suitable for substrate binding. Disadvantages: Potential denaturation of the enzyme: Chemical activation to create covalent links at times distorts the shape of the enzyme, producing partial activity or a loss of stability. More complex procedures: The requirement of certain functional groups on the support and enzyme and the use of chemical reagents make the procedure more time-consuming and expensive than physical adsorption. Covalent bonding is used most frequently in situations where enzyme stability and reusability are issues, such as in continuous-flow bioreactors, biosensors, and diagnostic devices. ,

3.3. Entrapment

Entrapment, also referred to as encapsulation, is a physical immobilization strategy wherein enzymes are confined within a semipermeable matrix or membranesuch as hydrogels, polymeric membranes, or mesoporous nanoparticleswithout forming covalent bonds with the support (Figure c). In this configuration, the enzyme remains spatially restricted within the support structure, while substrates and products are able to diffuse freely in and out through the porous network. This approach offers a microenvironment that can protect the enzyme from external stresses, including extreme pH, temperature fluctuations, and the presence of denaturing agents. −

One of the primary strengths of encapsulation is the physical protection it offers to the enzyme, which helps to preserve its structural integrity and catalytic function even under harsh reaction conditions. Because the enzyme is not chemically modified during immobilization, the risk of activity loss due to conformational changes is minimal. Additionally, the immobilized enzyme system is generally recoverable and reusable, which contributes to cost-effectiveness in large-scale or continuous biocatalytic processes.

Despite these benefits, entrapment methods also face certain challenges. Diffusional limitations within the encapsulating matrix can restrict substrate accessibility to the enzyme’s active site, potentially leading to reduced reaction ratesparticularly in systems with high viscosity or when processing large molecular substrates. Furthermore, enzyme leakage may occur if the encapsulation matrix lacks sufficient mechanical integrity or is subject to degradation, which can compromise both the activity and purity of the final product.

3.4. Cross-Linking

Cross-linking is a widely adopted enzyme immobilization strategy that involves the formation of covalent bonds either between enzyme molecules themselves or between enzyme molecules and a support matrix. − This technique typically employs bifunctional cross-linking agentssuch as glutaraldehyde or carbodiimidesthat react with amino or carboxyl groups on the enzyme surface, leading to the generation of insoluble enzyme aggregates or networks. Among the most prominent outcomes of this approach are cross-linked enzyme aggregates (CLEAs), which have gained significant attention due to their operational robustness and ease of recovery. Cross-linking confers enhanced structural rigidity to enzyme molecules, thereby improving their thermal stability, resistance to denaturation, and tolerance to harsh reaction conditions. This stabilization is particularly valuable in industrial biocatalysis, where prolonged enzyme activity under nonphysiological environments is essential. Furthermore, cross-linked enzyme systems offer high reusability and operational longevity, which contributes to cost efficiency in large-scale or continuous processes. The degree of cross-linking can also be modulated to optimize specific parameters such as enzyme loading, mechanical strength, and catalytic performance.

Despite its advantages, cross-linking is not without limitations. Excessive cross-linking can lead to conformational constraints or steric hindrance, diminishing the flexibility of the enzyme and thereby reducing its catalytic activity. Moreover, the immobilization procedure requires precise control over reaction conditionssuch as cross-linker concentration, reaction time, and pHto prevent enzyme inactivation and aggregation. This added complexity can increase both the technical demands and the cost of implementation compared to simpler immobilization methods.

3.5. Affinity Binding

Affinity binding is a highly selective method for enzyme immobilization that harnesses specific molecular recognition between an enzyme and a complementary ligand preattached to a solid support (Figure d). Typical examples include biotin–streptavidin and antibody–antigen systems. These biologically inspired interactions allow for the targeted and oriented immobilization of enzymes under mild, nondenaturing conditions. Since the binding process is based on natural, noncovalent forces, the immobilized enzymes often retain their native structure and catalytic activity, making this method especially suitable for applications where enzyme functionality must be preserved.

One of the principal benefits of affinity immobilization lies in its exceptional specificity. Only the desired enzyme binds selectively to the immobilized ligand, thereby reducing nonspecific adsorption and enhancing immobilization efficiency. Furthermore, the noncovalent nature of the interaction ensures minimal conformational disturbance, thus maintaining high enzymatic activity. Another significant advantage is the reversibility of the binding, allowing for controlled release or recovery of the enzyme by introducing competitive ligands or by altering environmental parameters such as pH or ionic strength. This dynamic controllability is particularly valuable in applications that require enzyme replacement, regeneration of the support surface, or temporary immobilization. −

Despite these strengths, affinity-based immobilization is associated with several limitations. The need for specific ligand–receptor pairs increases both the cost and the technical complexity of the system, often necessitating prior knowledge of enzyme-ligand compatibility and additional steps for ligand functionalization. Moreover, this approach is limited to enzymes for which suitable affinity ligands are known and can be practically immobilized. Nonetheless, due to its precision, biocompatibility, and reversibility, affinity immobilization has been widely adopted in high-value and specialized fields such as biosensing, diagnostics, affinity chromatography, and bioanalytical platforms where retention of enzyme activity and selectivity is paramount.

4. Functional Enhancement through Immobilization

Immobilizing enzymes onto solid supports offers a range of functional advantages that substantially enhance their catalytic performance, operational stability, and reusability. These improvements make immobilized enzymes highly attractive for a broad spectrum of applications spanning industrial biocatalysis, biomedical engineering, and environmental remediation. By modifying the microenvironment surrounding the enzymesuch as surface characteristics, structural rigidity, and substrate accessibilityimmobilization strategies can extend enzyme performance beyond the limitations observed in their free (soluble) form. This chapter discusses the key functional enhancements enabled by enzyme immobilization, including improved thermal and pH stability, enhanced reusability, refined substrate specificity, and increased catalytic efficiency, which together contribute to the development of more robust and economically viable biocatalytic systems.

4.1. Thermal and pH Stability

One of the primary benefits of enzyme immobilization is the significant enhancement of both thermal and pH stability. Free enzymes are inherently sensitive to changes in temperature and pH, which can lead to denaturation and loss of catalytic activity. Immobilization on solid supports restricts the conformational flexibility of enzymes, thereby reducing their vulnerability to adverse environmental conditions such as elevated temperatures and extreme pH values. ,

Immobilized enzymes generally exhibit superior thermal stability compared to their free counterparts. The immobilization matrix creates a protective microenvironment that helps maintain the native enzyme conformation under elevated temperatures. This stabilization is particularly advantageous for industrial processes that require biocatalysts to function efficiently at high temperatures, including biofuel production, food processing, and pharmaceutical manufacturing. The increased thermal resistance arises from the physical constraint imposed by the support material, which limits enzyme unfolding. Additionally, matrices such as silica nanoparticles, polymers, and hydrogels contribute to enhanced thermal protection by providing a thermally stable microenvironment that further guards against enzyme denaturation.

Enzyme immobilization also improves stability across a broader pH range. The support matrix can act as a buffer, moderating the local microenvironment around the enzyme and shielding it from pH-induced conformational changes. For instance, hydrogels and silica-based supports have demonstrated the ability to preserve enzymatic activity under both acidic and alkaline conditions. Such improvements in pH tolerance make immobilized enzymes particularly suitable for applications in variable pH environments, such as wastewater treatment and biofuel production.

4.2. Increased Reusability and Recovery

One of the principal advantages of enzyme immobilization, especially in industrial and large-scale applications, is the enhanced reusability of the biocatalyst. − Free enzymes are typically employed in batch processes, exhibiting limited reusability and incurring high operational costs. In contrast, immobilized enzymes can be readily separated from the reaction mixture and reused with minimal loss of catalytic activity. This characteristic is particularly beneficial for continuous-flow bioreactors, biosensors, and other enzyme-catalyzed systems requiring prolonged operation times.

The ease of enzyme recovery is largely determined by the immobilization strategy and the nature of the support material. For instance, enzymes immobilized on magnetic nanoparticles can be efficiently separated using an external magnetic field, whereas those immobilized within mesoporous materials or hydrogels can be recovered through conventional filtration or centrifugation methods. Efficient recovery of immobilized enzymes not only reduces operational costs but also contributes to more sustainable and environmentally friendly industrial processes.

Moreover, immobilization significantly extends the operational lifespan of enzymes. Unlike free enzymes, which often lose activity after only a few reaction cycles, immobilized enzymes retain catalytic function over extended periods, especially when stabilization techniques such as covalent bonding or encapsulation are employed. This enhanced stability mitigates enzyme degradation and enables sustained operation under consistent reaction conditions.

4.3. Increased Substrate Specificity

Enzyme immobilization can significantly influence substrate specificity and catalytic efficiency, often enhancing enzymatic performance for targeted reactions. The nature of the support material plays a crucial role in modulating the enzyme’s active site conformation, frequently inducing a more favorable structural arrangement that increases substrate binding affinity. Such conformational stabilization can reduce the enzyme’s flexibility, thereby promoting a more precise and efficient catalytic interaction with the substrate. For example, glucose oxidase immobilized on silica nanoparticles exhibited enhanced affinity toward glucose due to the stabilization of its active site conformation, leading to improved catalytic efficiency in glucose sensing applications. −

In certain cases, the support material itself may contribute catalytically, acting as a cocatalyst or facilitating substrate recognition and orientation. Nanomaterials such as gold nanoparticles and carbon nanotubes possess unique surface chemistries and electronic properties that interact synergistically with immobilized enzymes. For instance, horseradish peroxidase immobilized on gold nanoparticle-modified electrodes showed increased catalytic activity, attributed to improved electron transfer and favorable orientation of the enzyme active site toward the substrate. Similarly, carbon nanotubes have been demonstrated to enhance the catalytic efficiency of lipase by promoting substrate binding through hydrophobic interactions and spatial alignment.

Moreover, immobilization within confined environments, such as mesoporous materials, imposes spatial restrictions that selectively limit substrate access based on size and shape. This selective substrate diffusion through the pore architecture enhances the overall selectivity of the biocatalyst by favoring substrates compatible with the pore dimensions while excluding larger or structurally incompatible molecules. An illustrative example is the immobilization of lipase within mesoporous silica, which selectively enhanced the hydrolysis of short-chain esters due to size exclusion effects within the pores. Such steric constraints not only improve catalytic specificity but also reduce side reactions, increasing the overall efficiency of the enzymatic process.

Collectively, these factors demonstrate that enzyme immobilization strategies can be optimized by leveraging conformational effects, support material properties, and spatial constraints. This enables tailored enhancement of enzyme–substrate interactions, resulting in improved catalytic performance and selectivity for various industrial and biomedical applications.

4.4. Catalytic Efficiency

Compared to free enzymes, immobilized enzymes generally exhibit enhanced catalytic activity due to increased stability, improved substrate accessibility, and the ability to operate under more controlled and stable reaction conditions. The immobilization support plays a critical role in preventing enzyme aggregation, thereby maximizing the proportion of active enzyme molecules available for catalysis. Furthermore, immobilization can regulate enzyme–substrate interactions by controlling enzyme orientation on the support surface and minimizing diffusion limitations, which often hinder reaction rates in free enzyme systems. ,

A key factor contributing to the enhanced catalytic performance of immobilized enzymes is the capacity for high enzyme loading on supports with large specific surface areas. Materials such as mesoporous silica, graphene, and carbon nanotubes provide extensive surface area and favorable physicochemical properties that facilitate dense enzyme immobilization without compromising enzymatic activity. This high enzyme loading is particularly advantageous in high-throughput or continuous-flow bioreactors, where maintaining elevated enzyme concentrations is essential to sustain efficient reaction rates.

Additionally, immobilization can mitigate product inhibition, a common issue in free enzyme catalysis where accumulated reaction products interfere with enzyme activity. By confining the enzyme within specific microenvironments or enabling rapid product diffusion away from the active site, immobilization reduces local product accumulation. Techniques such as enzyme entrapment further protect enzymes from exposure to inhibitory compounds, thereby preserving catalytic efficiency. This reduction in product inhibition contributes to sustained enzyme activity over extended operational periods, enhancing process productivity.

5. Biomedical Applications

The discipline of biomedicine has greatly advanced through advancements in enzyme immobilization, particularly through the use of nanoengineered materials. Immobilized enzymes offer numerous advantages in biomedical applications, including enhanced stability, enhanced specificity, and the ability to function within more controlled or targeted environments. In this section, we elaborate on the different biomedical uses of nanoimmobilized enzymes, such as biosensors, diagnostic devices, therapeutic enzyme delivery, and wearable monitoring systems.

5.1. Biosensors

Biosensors are analytical devices that employ enzymes or other biological recognition elements to selectively detect target molecules by transducing biochemical interactions into measurable electrical, optical, or thermal signals (Figure a). − Immobilization of enzymes on nanomaterials has emerged as a powerful strategy to enhance biosensor performance, notably improving sensitivity, specificity, and operational stability. Nanoengineered supports, including gold nanoparticles, carbon nanotubes, and graphene, are commonly utilized in enzyme-based biosensors due to their high surface area and excellent electrical conductivity, which facilitate efficient electron transfer between the enzyme’s active site and the electrode surface.

5.

(a) A biosensor utilizing inkjet printing technology for enzyme immobilization via cross-linking. Reprinted with permission from ref . Copyright 2024 MDPI. (b) The integrated development of biosensors and self-powered devices for human health monitoring. Reprinted with permission from ref . Copyright 2024 Springer Nature. (c) The introduction of nanoenzymes with enzyme-like activity to assist in bone defect repair. Reprinted with permission from ref . Copyright 2024 Elsevier. (d) Production of bioethanol from rice straw (RS) biomass and its further use as a substrate in an enzyme-catalyzed cascade reaction system for acetoin production. Reprinted with permission from ref . Copyright 2024 Elsevier. (e) Schematic illustration of the synthesis process of CDST-M. (f) Schematic illustration of the process of fixing lipase via “cavity capture”. Reprinted with permission from ref . Copyright 2024 Elsevier.

One of the most prevalent biosensor technologies is the Enzyme-Linked Immunosorbent Assay (ELISA), which relies on immobilized enzymes to capture and quantify specific antigens or antibodies. Enzymes such as horseradish peroxidase (HRP) and alkaline phosphatase (AP) are conjugated with antibody molecules, enabling sensitive detection of biomarkers in biological samples through catalytic signal amplification.

Glucose sensors represent a widely recognized application of enzyme-based biosensors, particularly in diabetes management. These devices commonly utilize glucose oxidase (GOx) to catalyze the oxidation of glucose into gluconolactone and hydrogen peroxide. Immobilizing GOx onto conductive nanomaterials, such as gold nanoparticles or carbon nanotubes, significantly enhances sensor sensitivity and reproducibility. Moreover, these nanomaterials accelerate electron transfer and increase the response rate, which is critical for real-time glucose monitoring in clinical settings.

Beyond medical diagnostics, enzyme-based biosensors play a vital role in environmental and food safety monitoring. Enzymes capable of degrading pesticides or organophosphates can be immobilized on nanostructured supports to develop highly sensitive detectors for toxic substances in water and food matrices. The combination of high surface area and the intrinsic specificity of nanoengineered materials enables the detection of trace levels of pollutants, contributing to improved environmental surveillance and public health protection. ,

5.2. Diagnostic Devices

Immobilized enzymes play a pivotal role in the development of advanced diagnostic devices, particularly those designed for the detection of disease-related biomarkers. The improved stability, reusability, and prolonged shelf life conferred by immobilization are especially advantageous in point-of-care (POC) diagnostic platforms and portable detection systems, where reliability and rapid response are essential. Nanoengineered supports not only enhance enzyme stability but also enable high enzyme loading and accelerated reaction kinetics, thereby facilitating faster and more sensitive diagnostic readouts (Figure b). −

In point-of-care diagnostics, immobilized enzymes are extensively employed for the rapid detection of various pathological conditions, including cancer, infectious diseases, and metabolic disorders. These diagnostic systems often utilize enzyme-linked immunoassays (ELISAs) or enzyme-mediated signal amplification strategies to detect low-abundance biomarkers in biological fluids such as blood, saliva, or urine. The incorporation of nanomaterials, such as gold nanoparticles and silica nanoparticles, significantly enhances assay performance by increasing the surface area for enzyme attachment and amplifying the detection signal through improved electron or energy transfer mechanisms. Such enhancements are critical for ensuring diagnostic sensitivity and specificity, particularly in resource-limited or decentralized clinical environments.

In conventional clinical diagnostics, enzyme assays remain a mainstay for the assessment of disease states and organ function. Enzymes such as lactate dehydrogenase (LDH), creatine kinase (CK), and alkaline phosphatase are routinely measured as indicators of myocardial infarction, liver dysfunction, and tissue damage. The immobilization of these enzymes on functionalized nanostructured materialssuch as magnetic nanoparticles, carbon-based substrates, or mesoporous silicaenables the construction of highly sensitive and miniaturized biosensing platforms. These platforms offer real-time monitoring capabilities, reduced reagent consumption, and the potential for integration into lab-on-a-chip or microfluidic systems, greatly advancing personalized diagnostics and therapeutic monitoring.

5.3. Therapeutic Enzyme Delivery

Therapeutic enzyme delivery involves the administration of enzymes as bioactive agents to restore deficient enzymatic functions or to catalyze specific biochemical reactions within target tissues. Immobilization of therapeutic enzymes onto or within nanostructured carriers offers several distinct advantages, including improved enzyme stability, targeted delivery, and controlled release profiles. These properties are particularly beneficial for enhancing therapeutic efficacy while minimizing systemic toxicity and side effects. −

Enzyme replacement therapy (ERT) is a prominent application of this approach, commonly used to treat inherited metabolic disorders characterized by specific enzyme deficiencies, such as Gaucher disease and Fabry disease. In such cases, therapeutic enzymes can be immobilized within hydrogels or attached to nanoparticles to protect them from degradation and enable site-specific delivery. For example, the delivery of glucocerebrosidase for Gaucher disease or alpha-galactosidase A for Fabry disease can be achieved through nanoparticle-based carriers that enhance the retention and activity of the enzyme at the diseased tissue site.

Immobilized enzymes have also been employed in cancer therapy, particularly in enzyme-prodrug systems. In this strategy, an inactive prodrug is converted into an active cytotoxic drug by an enzyme that is selectively delivered to the tumor site. Immobilizing enzymes such as cytosine deaminase onto biocompatible nanoparticles enables localized conversion of prodrugs within the tumor microenvironment, significantly improving drug specificity while reducing damage to healthy tissues.

Controlled release systems based on immobilized enzymes offer an additional therapeutic advantage. Enzymes encapsulated within hydrogels, liposomes, or polymeric nanocarriers can be designed to respond to physiological stimuli such as pH, temperature, or redox conditions. These systems enable sustained and regulated enzyme release over extended durations, which is particularly valuable for chronic diseases requiring long-term management or for localized enzyme therapies. For instance, pH-sensitive hydrogel systems can be engineered to release therapeutic enzymes specifically in inflamed or diseased tissues, improving treatment precision and patient compliance.

5.4. Wearable Monitoring Devices

Wearable monitoring devices incorporating enzyme-based sensors represent a rapidly evolving frontier in healthcare technology, offering the potential for continuous, noninvasive monitoring of key physiological and biochemical markers. These systems are designed to provide real-time feedback for health management, disease monitoring, and personalized diagnostics. The incorporation of nanoimmobilized enzymes is central to the performance of such devices, owing to their enhanced sensitivity, operational stability, and compatibility with miniaturized platforms. −

Wearable biosensors targeting body fluids such as sweat and saliva are particularly promising due to their noninvasive nature. Biomarkers such as glucose, lactate, and uric acid can be monitored using enzyme-based sensors that employ nanoimmobilized enzymes to ensure high selectivity and signal fidelity. For instance, sweat-based glucose sensors utilizing glucose oxidase immobilized on conductive nanomaterials can detect glucose concentrations at low levels, making them suitable for diabetic patient monitoring without the need for blood sampling. The high surface area and electron transfer capabilities of nanomaterials significantly amplify the sensor response, enabling more accurate and reliable biomarker quantification.

In the context of continuous glucose monitoring (CGM), which is essential for effective diabetes management, nanoimmobilized glucose oxidase is commonly used to catalyze the oxidation of glucose in interstitial fluids. The use of nanostructured materials such as carbon nanotubes, gold nanoparticles, or graphene not only enhances sensor sensitivity but also supports device miniaturization and integration into compact, wearable formats. These systems provide real-time glucose data to patients and healthcare providers, facilitating improved glycemic control and reducing the risk of long-term complications.

Beyond disease management, enzyme-based wearable sensors are increasingly being integrated into fitness and wellness devices. Wearables such as smartwatches and fitness trackers can incorporate immobilized lactate dehydrogenase (LDH) to monitor lactate levels in sweat, offering insights into muscle metabolism and physical exertion. This enables users to receive personalized physiological feedback during exercise, optimize their training routines, and monitor fatigue or recovery status. The use of nanoimmobilized enzymes in these platforms improves enzyme retention, extends sensor lifespan, and ensures consistent performance under dynamic physiological conditions.

5.5. Enhancing Bone Tissue Repair

Enzyme immobilization technology significantly enhances the functional performance of enzymes in orthopedic medicine by stabilizing enzyme activity and extending their duration of action, thereby advancing bone repair and tissue engineering. First, key immobilized enzymes such as alkaline phosphatase (ALP) promote the mineralization process of osteocytes, enhance the formation of bone matrix, thereby accelerating the healing of bone defects and bone tissue regeneration. Additionally, immobilizing enzymes on the surface of bone graft materials not only endows the materials with excellent biological activity but also promotes the integration of graft materials with host bone tissue by regulating the degradation and remodeling of bone matrix, thereby improving graft outcomes (Figure c). −

In terms of anti-infection and anti-inflammatory effects, immobilized enzymes (such as lysozyme and catalase) serve as antimicrobial coatings on the surfaces of orthopedic implants, significantly reducing the incidence of postoperative infections and improving the biocompatibility and long-term stability of the implants. Enzyme immobilization technology is also widely applied in targeted drug delivery systems, achieving local sustained release of orthopedic drugs through enzymatic reactions, thereby enhancing therapeutic efficacy while reducing systemic side effects, particularly suitable for the treatment of conditions such as osteoporosis and bone tumors.

Additionally, enzyme immobilization participates in the regulation of bone metabolism by influencing the signaling pathways of bone formation and resorption, offering new therapeutic strategies for metabolic bone diseases. Finally, enzyme immobilization plays a crucial role in the construction of bone biosensors, enabling highly sensitive detection of bone metabolism-related biomarkers to assist in real-time clinical monitoring of disease progression and efficacy assessment.

6. Biofuel Applications

The use of enzyme immobilization has become widespread in the biofuel industry as a method to increase the efficiency, stability, and reusability of biocatalysts used in the process of converting biomass into biofuels. Immobilized enzymes are better than free enzymes, particularly in large-scale applications such as the production of bioethanol and biodiesel. Nanoengineered materials, with their high surface area, functionalization capability, and enhanced stability, are promising platforms for enzyme immobilization in the case of biofuels. This section discusses the use of nanoimmobilized enzymes in the production of bioethanol and biodiesel and how these enzymes enhance the sustainability and efficiency of the biofuel industry.

6.1. Production of Bioethanol

Bioethanol, a sustainable biofuel derived from lignocellulosic biomass, is primarily produced through the enzymatic hydrolysis of cellulose and hemicellulose into fermentable sugars, followed by microbial fermentation (Figure d). The enzymes cellulase and hemicellulase play a central role in breaking down the recalcitrant carbohydrate structures within plant biomass, converting them into monosaccharides such as glucose, which are subsequently fermented to yield ethanol. The immobilization of these enzymes onto nanoengineered supports has emerged as a highly effective strategy to enhance their catalytic performance, especially under the demanding conditions typically encountered in large-scale bioethanol production. −

Immobilization significantly improves the stability and operational robustness of cellulase enzymes. Compared to their free counterparts, immobilized enzymes exhibit superior thermal and pH tolerance, which is critical for maintaining enzyme activity in industrial hydrolysis processes. Nanoengineered materials such as mesoporous silica, magnetic nanoparticles, and carbon-based nanomaterials provide high surface areas and functionalized surfaces that facilitate dense and stable enzyme loading. This enhances not only the activity but also the durability of the enzymes throughout multiple hydrolysis cycles, reducing the need for frequent enzyme replenishment and contributing to process cost-efficiency.

The enzymatic hydrolysis of cellulose is a rate-limiting step in bioethanol production, and immobilized enzymes offer considerable advantages in this context. Immobilized cellulases can be employed in continuous-flow bioreactor systems, enabling prolonged enzymatic reactions without significant loss in performance. The sustained release and high local concentration of the immobilized enzymes at the substrate interface improve the hydrolysis rate, ensuring consistent conversion of cellulose into glucose. Furthermore, nanoimmobilization strategies can be tailored to optimize enzyme orientation and substrate accessibility, both of which are critical for maximizing hydrolytic efficiency.

Beyond standalone enzyme applications, nanoimmobilized cellulases can be coimmobilized or integrated into multienzyme systems that include complementary enzymes such as xylanases and amylases. This cooperative arrangement enables the efficient breakdown of a wide range of plant-derived polysaccharides into fermentable sugars. Additionally, such enzyme systems can be designed to overcome the inhibitory effects of lignin and other complex biomass constituents, which often hinder enzymatic activity during biomass conversion. By improving enzyme synergy and reducing enzyme deactivation, nanoimmobilized enzyme complexes

6.2. Biodiesel Production

Biodiesel, a renewable and environmentally friendly alternative to petroleum-based diesel, is primarily synthesized through the transesterification of triglyceridesderived from plant oils or animal fatswith short-chain alcohols such as methanol or ethanol (Figure e,f). − This process, traditionally catalyzed by chemical bases or acids, has increasingly adopted biocatalytic approaches involving lipase enzymes due to their selectivity, mild operating conditions, and reduced byproduct formation. Among these, nanoimmobilized lipases have garnered considerable attention for enhancing the efficiency, sustainability, and scalability of biodiesel production.

Immobilization of lipases on nanostructured supports significantly improves their catalytic performance, particularly in terms of stability, reusability, and reaction rate. Nanomaterials such as magnetic nanoparticles, mesoporous silica, carbon nanotubes, and functionalized polymers offer large surface areas and versatile surface chemistries, enabling high enzyme loading and favorable enzyme orientation. These properties contribute to enhanced catalytic activity and prolonged operational lifespans, even under the harsh processing conditions of biodiesel synthesis, which often include elevated temperatures, alkaline environments, and exposure to hydrophobic solvents.

The stability and reusability of immobilized lipases are critical for the economic viability of enzymatic biodiesel production. For example, lipases immobilized on magnetic nanoparticles not only demonstrate improved structural integrity under reaction conditions but also enable facile magnetic separation, allowing for repeated cycles of use without significant activity loss. This recyclability markedly reduces the cost associated with enzyme replenishment and minimizes waste generation, thereby aligning with the principles of green chemistry and sustainable manufacturing.

In terms of reaction efficiency, nanoimmobilized lipases facilitate faster and more complete transesterification by improving substrate accessibility and reducing mass transfer limitations. The nanostructured support materials can also mitigate the inhibitory effects of byproducts such as glycerol and free fatty acids, which often hinder the activity of free enzymes in conventional systems. For instance, immobilized lipases have been shown to retain high catalytic activity in the presence of high concentrations of free fatty acids, enabling the direct conversion of low-quality or waste oilspreviously unsuitable for chemical catalysisinto biodiesel. This expands the range of usable feedstocks and improves the overall resource efficiency of the process.

Moreover, the application of nanoimmobilized lipases in continuous-flow bioreactor systems further enhances the scalability and industrial applicability of enzymatic biodiesel production. In such systems, the immobilized enzymes are continuously exposed to the substrate, maintaining steady catalytic turnover over extended periods. The high mechanical and chemical stability of nanoimmobilized lipases ensures consistent conversion rates with minimal downtime. Magnetic nanoparticle-supported lipases, for example, are particularly well-suited for these configurations, as they can be easily recovered and redeployed using external magnetic fields, thus streamlining the separation and purification stages.

7. Conclusions and Perspective

This review provides a comprehensive overview of the significant advancements in nanoengineered enzyme immobilization, highlighting how the integration of nanotechnology has revolutionized biocatalysis for various applications, particularly in biomedicine and biofuel production. We have systematically examined the diverse nanomaterials utilized as immobilization supports, including silica, gold nanoparticles, polymers, magnetic nanoparticles, carbon-based materials, and hydrogels, each offering unique properties such as high surface area, biocompatibility, and functional tunability that profoundly influence enzyme performance. The exploration of various structural designs, such as core–shell nanoparticles, mesoporous materials, and nanofiber networks, has further underscored the versatility of nanoimmobilization in enhancing enzyme stability, catalytic efficiency, and reusability by providing optimized microenvironments and controlled spatial configurations. Furthermore, the review has detailed the prevalent immobilization methodsphysical adsorption, covalent bonding, entrapment, cross-linking, and affinity bindingand their respective impacts on enzyme functionality and stability.

The functional enhancements achieved through nanoengineered enzyme immobilization are remarkable, extending to improved thermal and pH stability, increased reusability, refined substrate specificity, and overall enhanced catalytic efficiency. These improvements have paved the way for numerous biomedical applications, including highly sensitive biosensors for glucose and other biomarkers, advanced diagnostic devices for various pathologies, and precise therapeutic enzyme delivery systems. The emergence of wearable monitoring devices leveraging nanoimmobilized enzymes for continuous, noninvasive health tracking further exemplifies the transformative potential in personalized healthcare. Beyond biomedicine, the technology’s utility is powerfully demonstrated in biofuel production, where immobilized enzymes significantly boost the efficiency and sustainability of bioethanol and biodiesel synthesis by enhancing enzyme stability and reusability in demanding industrial processes.

Despite these significant breakthroughs, challenges remain, notably in cost-effectiveness, enzyme leaching, and the complexity of scaling up nanoimmobilization techniques. Future advances will likely involve smart nanomaterials integrated with artificial intelligence (AI) to overcome these limitations. In particular, machine learning (ML) can analyze large data sets of enzyme structures, surface chemistries, and performance metrics to predict optimal enzyme–nanomaterial pairings, reducing experimental workload and enhancing efficiency. Combined with high-throughput screening and computational modeling, ML-guided design enables faster discovery of stable, responsive immobilization platforms. Such interdisciplinary strategies will drive the development of advanced nanocomposites and unlock broader industrial and biomedical applications.

Writingoriginal draft preparation: X.M. and T.S.P.; writingreview and editing: B.G. and J.Z. All the authors have read and agreed to the published version of the manuscript.

The authors declare no competing financial interest.