Synthetic biology integrated with material science paves the way for next-generation smart cell therapies

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Pulmonary metastasis represents a major bottleneck in cancer survival, responsible for nearly one-third of solid tumor deaths.¹ The eradication of these lesions is hindered by the lung’s complex vascular architecture,² which restricts drug access, and the insidious nature of micrometastases, which evade surgical clearance. Current systemic therapies thus face a steep therapeutic index, where the dose required to penetrate the alveolar barrier inevitably triggers severe off-target toxicity.

In recent years, immunotherapy has emerged as a beacon of hope, harnessing the body’s own defenses to track down and eliminate cancer cells.³ However, this power comes with a significant risk. The “paradox of potency” in immunotherapy signifies that uncontrolled immune activation can be as lethal as the target disease itself. This is vividly illustrated by cytokine release syndrome, a frequent and severe complication observed in chimeric antigen receptor-T cell therapies.⁴ How can we deliver potent immunotherapeutics directly to the tumor site while maintaining precise control to prevent life-threatening toxicity?

In a recent study published in Science Advances,⁵ we describe a strategy that merges synthetic biology with material science to address this challenge. We developed a “living medicine” platform termed the RL/FRL-EnE system (red/far-red light-regulated individual encapsulated cell). This system transforms mammalian cells into programmable biological factories that can be remotely toggled “on” and “off” using specific wavelengths of light, offering a solution to the long-standing problem of uncontrollability in cell therapies.

A cornerstone of our design is the use of pH-low insertion peptide (pHLIP)-mediated reversible anchoring for cell surface engineering (Figure 1A). Unlike layer-by-layer deposition techniques, which often rely on covalent bonding or strong electrostatic interactions, our approach exploits the unique, pH-dependent insertion mechanism of pHLIP peptides.⁶ This allows for the assembly of a protective shield under mild physiological conditions without permanently perturbing the plasma membrane structure.⁷ This creates a protective shield robust enough to evade immune clearance yet compliant enough to preserve the cell’s intrinsic fluidity. Consequently, our living drugs can navigate the complex pulmonary capillary network without obstruction, effectively resolving the trade-off between immunoprotection and circulation efficiency (Figure 1B).

Figure 1.

Schematic illustration of the design and functional mechanism of EnE cells

(A) Mechanism of pHLIP-mediated membrane display. At physiological pH (7.4), the pHLIP peptide associates with the cell membrane surface. Upon acidification (pH 6.5), the peptide undergoes a conformational transition into a transmembrane α-helix, anchoring horseradish peroxidase (HRP) to the extracellular surface. (B) The hydrogel layer provides mechanical stability and physically isolates cells from immune surveillance (e.g., macrophages and dendritic cells), thereby mitigating immune rejection. Its porous structure permits the diffusion of small molecules to sustain cell viability. The hyaluronic acid backbone actively targets CD44 receptors overexpressed on tumor cells, facilitating tumor-specific delivery. (C) Engineering of optogenetic control and cell encapsulation. HEK293T cells serve as the chassis for a genetic circuit composed of FHY1-ΔPhyA and Gal4-VP64. Gene expression is activated by red light (660 nm) and rapidly terminated by far-red light (730 nm). Following the surface display of HRP, an enzymatic cross-linking reaction with H₂O₂ and dopamine- modified hyaluronic acid (HA-DA) forms a hydrogel shell around the cells.

We engineered mammalian cells with a bistable phytochrome A (ΔPhyA)⁸ optogenetic circuit to enable precise, bidirectional control (Figure 1C). Mechanistically, illumination with 660 nm (red) light triggers the assembly of split photoreceptors, driving the expression of interferon-γ, anti-CD47 antibodies, andinterleukin-6. Conversely, exposure to 730 nm (far-red) light causes immediate dissociation, halting protein secretion. These wavelengths were specifically selected for their superior penetration within the tissue “optical window” compared to the blue or green spectrum. While external illumination suffices for murine models, clinical translation necessitates overcoming the barrier of tissue depth. We propose integrating the system with fiber-optic bronchoscopy or thoracoscopy to deliver therapeutic light directly to deep-seated intrapulmonary or pleural lesions. This strategy ensures robust activation by circumventing the penetration limitations associated with external irradiation.

To advance the RL/FRL-EnE system from a proof of concept to a versatile clinical modality, future efforts must address the complexity of diverse tumor microenvironments. Key priorities include optimizing synthetic circuits for multi-input antigen discrimination,⁹ reconciling the trade-off between long-term immune evasion and rapid mass transport, and extending non-invasive optical control to deep-seated malignancies. Progress in these domains will drive the transition toward precision medicine, where treatment ceases to be a blunt instrument and becomes a precise, controllable dialog between the clinician and the patient’s intrinsic physiology.

Cell-based cancer immunotherapy is undergoing a paradigm shift, driven by the emergence of programmable, spatiotemporally controlled living therapeutics.¹⁰ In models of pulmonary metastasis, the RL/FRL-EnE system demonstrates that integrating synthetic logic-gating with encapsulation effectively decouples therapeutic efficacy from systemic toxicity. This “optogenetic living factory” represents a pivotal innovation, initiating a transition from static drug delivery to dynamic biological intervention. As the platform’s versatility is validated across diverse pathologies, focus will shift to optimizing the clinician-physiology interface, advancing the field toward precise, controllable cancer medicine.

Acknowledgments

This work was supported by the Natural Science Foundation of China (grant no. 82102219) and the International Postdoctoral Exchange Fellowship Program (talent-introduction program, grant no. YJ20220182).

Declaration of interests

The authors declare no competing interests.