Table 3.
Comparison of biodegradable piezoelectric organic micro‐ and nanomaterials in terms of type of material synthesis approach, size and shape, biodegradation time, and biodegradation mechanism in physiological conditions.
Material | Fabrication approach | Shape and size | Biodegradation medium | Biodegradation time | Biodegradation mechanism/byproducts and immune reaction | References |
---|---|---|---|---|---|---|
Poly‐L‐lactic acid (PLLA) | Solvent‐casting | Thin film, thickness: 100 nm (size: 18 × 18 mm2) | Degradation test at 37 °C in 50 mM Tris‐HCl buffer (pH: 8.5) with 0.2 mg mL−1 of proteinase K | Amorphous regions completely degraded after 120 min, and only the crystalline regions remained intact | Enzymatic degradation | [239] |
Dip coating | Thin film, 50–150 μm (Eco‐PLLA 520) | Degradation test at 37 °C in Sorensen's phosphate buffer (pH 7.4) | Molecular weight almost halved over time, while the weight loss over 23 weeks was lower 10% | Hydrolytic degradation | [240] | |
Compression molding | Thin film, thickness: ≈35 μm |
Degradation test at 37 °C in PBS for 14 days, then switched to 74 °C. Implantation in the backs of mice (C57BL/6J model) |
No significant degradation of the PLLA sensors after 14 days. The sensor completely degraded at 74 °C after 56 days In vivo, the sensor did not degrade |
Hydrolytic degradation Mild immune reaction without significant presence of inflammation, multinucleated giant cells, and fibrous capsules |
[241] | |
Electrospinning | Electrospun mat, thickness: 19–28 μm (size: 5 × 5 mm2) | Implantation on a craniotomy defect in the mouse's skull (C57BL/6J model) | Degradation after 4 weeks of implantation |
Hydrolytic degradation of the ester‐bond backbone The device elicits minimal fibrosis and immuneresponse |
[225] | |
Polyhydroxybutyrate (PHB) | Electrospinning | Electrospun mat, thickness: 250 μm | Degradation test at 37 °C in PBS | PHB showed a 6 % mass loss after 4 weeks | Hydrolytic degradation | [242] |
Electrospinning |
Electrospun mat, size 50 × 50 mm2 Fiber diameter: 196 ± 65 nm |
Degradation test at 37 °C in simulated body fluid with and without lysozyme (concentration not reported) | Weight loss is about 1.8% after 30 days. In the presence of lysozyme, weight loss increases to 14.4% in 30 days | Hydrolytic or enzymatic degradation | [243] | |
Dip coating | Thin film, thickness: ≈100 μm (size: 10 × 10 mm2) |
Degradation test at 37 and 70 °C in Sorensen's buffer (0.1 m, pH 7.4), with and without pancreatin (concentration not reported) Implantation in a defect (6 mm in diameter) in the abdomen of male Wistar rats |
Molecular weight decreased by 10, 25, and 45% after 3, 6, and 12 months. Accelerated degradation induced by pancreatin (molecular weight decrease of 30% after 3 months). Absence of changes in film mass over 52 weeks In vivo, the material had a molecular weight of about 38% of the initial value after 26 weeks |
Hydrolytic degradation. Enzymatic catalysis is unclear as the degradation behavior consists of molecular weight loss but constant mass | [244] | |
γ‐Glycine | Casting with solvent evaporation | Thin film, thickness: ≈70 μm (with Mb electrodes and PLA encapsulation) |
Degradation test at 37 °C in PBS Implantation in the back of the mice (C57 model) |
Dissolution of PLA‐encapsulated γ‐glycine/PVA film within 2 weeks In vivo, the material was gradually absorbed within 10 days. |
Degradation mechanism not reported No evidence of tissue damage, immune response, or recognizable material byproduct |
[186] |
Casting with solvent evaporation | Thin film, thickness: 30 μm (with Mb electrodes) | Implantation under the skin in the dorsal region of rat (Sprague Dawley rat model) | The device completely disappeared after 1 day |
Degradation mechanism not reported. Absence of any significant reference to immunorespoinse |
[245] | |
β‐Glycine | Drop casting and solvent evaporation | Thin film, thickness: 38 μm | Degradation test at room temperature in PBS | The glycine/chitosan film dissolved after 2 days | Not reported | [156] |
Poly‐γ‐methyl‐L‐glutamate (PMLG) | Dry spinning | Spun fibers, thickness not reported | Degradation test at 37 °C in PBS with the pronase E (concentration not reported) | Dissolution within 15 h, depending on the concentration of pronase E | Hydrolytic and enzymatic degradation | [246] |
Poly‐γ‐benzyl‐L‐glutamate (PBLG) | Not reported | Thin film, thickness not reported | Degradation test at 37 °C in PBS with a protease (type IV, activity: 1.0 unit mg−1). | Degradation lower than 3% after 40 days | Hydrolytic degradation | [247] |
Diphenylalanine (FF) | Self‐assembly by dip coating | Self‐assembled monolayer of fibers, thickness not reported | Degradation test at 37 °C in PBS | Dissolution after 10 min | Hydrolytic degradation | [248] |
Self‐assembly and spin coating | FF microrods (diameter: 2–15 μm; length: ≈21 μm) in a PLA matrix (thickness: ≈51 μm) | Degradation test at 60 °C in PBS, 0.6 M NaOH, or 0.6 M HCl solutions | Complete dissolution in all media after 25 days. The degradation rate is in the order of alkaline solution > acidic solution > phosphate‐buffered saline | Hydrolytic degradation | [236] | |
Collagen | Not reported | Film thickness: ≈40 μm (noncrosslinked fibrillar bovine collagen I) | Subcutaneous implantation in adult male Lewis rats | Decrement in the film thickness of ≈75% in 21 days | Enzymatic degradation | [249] |
Not reported | Film thickness: 400 μm (porcine skin‐derived collagen: DHT and DHT/EDC cross‐linked membrane) |
Degradation test at 37 °C in a 0.25% porcine trypsin solution. Subcutaneous implantation in albino male Wistar rats |
Decrease in the thickness of the DHT and DHT/EDC membranes in 4 weeks after implantation (≈halved their thickness). In all cases, the thickness was close to 100 μm after 12 weeks | Enzymatic degradation | [250] | |
Commercial material | Geislich Bio‐Gide (Geistlich Biomaterials), thickness: 400 μm (25 × 25 mm2) | Implanted under the skin of the dorsal part of the cranium in Wistar‐derived rats | Degradation of 60% after 4 weeks, and of 80% after 9 weeks | Enzymatic degradation | [251] | |
Commercial material | Geislich Bio‐Gide (Geistlich Biomaterials), thickness: 400 μm | Implantation on intracranial defects of Wistar rats | The membrane thickness halved after 30 days | Enzymatic degradation | [252] | |
Chitin | Casting | Thin films of chitin with different degrees of deacetylation (from 0% to 100%), thickness: 150 μm |
Degradation in PBS with lysozyme (4 mg mL−1). Implanted in the subdermal tissue of Wistar rats back |
Pure chitin: 20% remaining weight after 30 h. Other deacetylated derivatives: weight remaining from 50% to 90% after 30 h In vivo, chitin and chitin with 69% degree degraded quite rapidly (50% after 2 weeks). while other deacetylated derivatives resisted up to 12 weeks, (weight remaining higher than 50%) |
Enzymatic degradation | [157] |
Casting | Thin film, thickness: ≈35 μm, β‐chitin | Degradation at room temperature in 1 UN/10 mL chitinase, in deionized water | Chitin film completely degraded after 8 days. The degradation time decreased to ≈4 days with 5 UN/10 mL of chitinase |
Enzymatic degradation The material might generate natural by‐products during biodegradation, such as CO2 gas |
[253] | |
Chitosan | Drop casting and solvent evaporation, crosslinked with NaOH | Thin film, thickness: 38 μm | Degradation at room temperature in PBS | Mg electrodes degraded within the first minutes in PBS, while glycine/chitosan completely dissolved after 2 days | Not reported | [156] |
Casting | Thin films, thickness: 150 μm |
Degradation in PBS with lysozyme (4 mg mL−1) Implanted in the subdermal tissue of Wistar rats back |
Pure chitosan lost less than 10% of its mass after 30 h In vivo, chitosan resisted with a negligible mass loss over 12 weeks |
Enzymatic degradation | [157] | |
Keratin | Self‐assembly | Thin film, thickness: 30–40 μm (size: 1 × 1 cm2) |
Degradation at 37 °C in a solution with trypsin Subcutaneous implantation in the back of a male mouse (Nippon Clare, Jcl:ICR 10 W) |
Degradation achieved 40–50% within 2 weeks, then leveled off at 50–60% in the following 18 weeks In vivo, slower degradation kinetics, with a linear tendency that extent up to 60% over 18 weeks |
Enzymatic degradation | [254] |
Silk | Spinning | Spun fiber, thickness not reported | Degradation at 37 °C in PBS with and without Protease XIV (1.0 mg mL−1) | Mass loss higher than 50% after 42 days with protease XIV. In PBS, the fibers did not degrade | Proteolytic degradation (enzymatic degradation) | [255] |
Casting | Thin film, thickness: ≈0.5 mm (size: 3 × 3 cm2) | Degradation at 37 °C in 0.05 M sodium phosphate buffer (pH 7.0), with ant without α‐chymotrypsin, collagenase IA, and protease XIV (1.0 U mL−1) | Weight rapidly decreased to 70% in 1 day in all cases. After 15 days, the weight of the sheet was 68, 48, 30, and 68% of the initial mass in α‐chymotrypsin, collagenase IA, protease XIV, and phosphate buffer, respectively |
Proteolytic degradation (enzymatic degradation) Degradation products from collagenase IA protease XIV reported a molecular weight lower than 2.4 kDa, while those in the buffer without enzymes ranged from 20.0 to 70.0 kDa |
[256] | |
Forming | Thin film, thickness: 100 nm | Degradation at 37 °C in PBS with protease XIV and α‐chymotrypsin (enzyme concentration: 300 μg mL−1) | α‐chymotrypsin did not contribute to significantly degrading the silk crystals over 24 h. Protease XIV formed nanofibrils, and decreased the thickness of silk crystals from 5 to 2 nm over 24 h |
Proteolytic degradation (enzymatic degradation) Degradation products from protease XIV contained several low molecular weight fragments (less than 50 kDa) with respect to the α‐chymotrypsin |
[257] | |
Cellulose | Not reported | Thin film, thickness 3 mm | Implanted subcutaneously in female Wistar rats | No evidence of degradation in vivo up to 12 weeks | Nonbiodegradable in physiological conditions | [258] |
M13 bacteriophage | Enforced infiltration | M13 phage with a rod shape, diameter: 6.6 nm; length: 880 nm | Degradation in human blood, saliva, urine, artificial gastric juice (AGJ) | Decrease of phages in human blood, saliva, and urine by 44, 88, and 66% after 45 min, respectively. No phage resists after 5 min in AGJ. PBS do not show significant decrease over time | Proteolytic degradation (enzymatic degradation) | [165] |