Enzyme-Embedded Degradation of Poly(ε-caprolactone) using Lipase-Derived from Probiotic Lactobacillus plantarum

Programming aliphatic polyester degradation by engineered bacterial spores

Enzymatic degradation of plastics is a sustainable approach to addressing the growing issue of plastic accumulation. The primary challenges for using enzymes as catalysts are issues with their stability and recyclability, further exacerbated by their costly production and delicate structures. Here, we demonstrate an approach that leverages engineered spores that display target enzymes in high density on their surface to catalyze aliphatic polyester degradation and create self-degradable materials. Engineered spores display recombinant enzymes on their surface, eliminating the need for costly purification processes. The intrinsic physical and biological characteristics of spores enable easy separation from the reaction mixture, repeated reuse, and renewal. Engineered spores displaying lipases completely degrade aliphatic polyesters and retain activity through four cycles, with full activity recovered through germination and sporulation. Directly incorporating spores into polyesters results in robust materials that are completely degradable. Our study offers a straightforward and sustainable biocatalytic approach to plastic degradation.

An engineered enzyme embedded into PLA to make self-biodegradable plastic

Plastic production reached 400 million tons in 2022 (ref. 1), with packaging and single-use plastics accounting for a substantial amount of this2. The resulting waste ends up in landfills, incineration or the environment, contributing to environmental pollution3. Shifting to biodegradable and compostable plastics is increasingly being considered as an efficient waste-management alternative4. Although polylactide (PLA) is the most widely used biosourced polymer5, its biodegradation rate under home-compost and soil conditions remains low6-8. Here we present a PLA-based plastic in which an optimized enzyme is embedded to ensure rapid biodegradation and compostability at room temperature, using a scalable industrial process. First, an 80-fold activity enhancement was achieved through structure-based rational engineering of a new hyperthermostable PLA hydrolase. Second, the enzyme was uniformly dispersed within the PLA matrix by means of a masterbatch-based melt extrusion process. The liquid enzyme formulation was incorporated in polycaprolactone, a low-melting-temperature polymer, through melt extrusion at 70 °C, forming an 'enzymated' polycaprolactone masterbatch. Masterbatch pellets were integrated into PLA by melt extrusion at 160 °C, producing an enzymated PLA film (0.02% w/w enzyme) that fully disintegrated under home-compost conditions within 20-24 weeks, meeting home-composting standards. The mechanical and degradation properties of the enzymated film were compatible with industrial packaging applications, and they remained intact during long-term storage. This innovative material not only opens new avenues for composters and biomethane production but also provides a feasible industrial solution for PLA degradation.

Enzyme modified biodegradable plastic preparation and performance in anaerobic co-digestion with food waste

A modified biodegradable plastic (PLA/PBAT) was developed by through covalent bonding with proteinase K, porcine pancreatic lipase, or amylase, and was then investigated in anaerobic co-digestion mixed with food waste. Fluorescence microscope validated that enzymes could remain stable in modified the plastic, even after co-digestion. The results of thermophilic anaerobic co-digestion showed that, degradation of the plastic modified with Proteinase K increased from 5.21 ± 0.63 % to 29.70 ± 1.86 % within 30 days compare to blank. Additionally, it was observed that the cumulative methane production increased from 240.9 ± 0.5 to 265.4 ± 1.8 mL/gVS, and the methane production cycle was shortened from 24 to 20 days. Interestingly, the kinetic model suggested that the modified the plastic promoted the overall hydrolysis progression of anaerobic co-digestion, possibly as a result of the enhanced activities of Bacteroidota and Thermotogota. In conclusion, under anaerobic co-digestion, the modified the plastic not only achieved effective degradation but also facilitated the co-digestion process.

Tuning the Biodegradation Rate of Silk Materials via Embedded Enzymes

Conventional thinking when designing biodegradable materials and devices is to tune the intrinsic properties and morphological features of the material to regulate their degradation rate, modulating traditional factors such as molecular weight and crystallinity. Since regenerated silk protein can be directly thermoplastically molded to generate robust dense silk plastic-like materials, this approach afforded a new tool to control silk degradation by enabling the mixing of a silk-degrading protease into bulk silk material prior to thermoplastic processing. Here we demonstrate the preparation of these silk-based devices with embedded silk-degrading protease to modulate the degradation based on the internal presence of the enzyme to support silk degradation, as opposed to the traditional surface degradation for silk materials. The degradability of these silk devices with and without embedded protease XIV was assessed both in vitro and in vivo. Ultimately, this new process approach provides direct control of the degradation lifetime of the devices, empowered through internal digestion via water-activated proteases entrained and stabilized during the thermoplastic process.

Biodegradation of microplastics: Advancement in the strategic approaches towards prevention of its accumulation and harmful effects

Microplastics (MPs) are plastic particles in a size ranging from 1 mm to 5 mm in diameter, and are formed by the breakdown of plastics from different sources. They are emerging environmental pollutants, and pose a great threat to living organisms. Improper disposal, inadequate recycling, and excessive use of plastic led to the accumulation of MP in the environment. The degradation of MP can be done either biotically or abiotically. In view of that, this article discusses the molecular mechanisms that involve bacteria, fungi, and enzymes to degrade the MP polymers as the primary objective. As per as abiotic degradation is concerned, two different modes of MP degradation were discussed in order to justify the effectiveness of biotic degradation. Finally, this review is concluded with the challenges and future perspectives of MP biodegradation based on the existing research gaps. The main objective of this article is to provide the readers with clear insight, and ideas about the recent advancements in MP biodegradation.

Engineered Geobacillus lipolytic enzymes - Attractive polyesterases that degrade polycaprolactones and simultaneously produce esters

Plastic pollution is one of the biggest environmental problems plaguing the modern world. Polyester-based plastics contribute significantly to this ecological safety concern. In this study, lipolytic biocatalysts GD-95RM and GDEst-lip developed based on lipase/esterase produced by Geobacillus sp. 95 strain were applied for the degradation of polycaprolactone films (Mn 45.000 (PCL45000) and Mn 80.000 (PCL80000)). The degradation efficiency was significantly enhanced by the addition of short chain alcohols. Lipase GD-95RM (1 mg) can depolymerize 264.0 mg and 280.7 mg of PCL45000 and PCL80000, films respectively, in a 24 h period at 30 °C, while the fused enzyme GDEst-lip (1 mg) is capable of degrading 145.5 mg PCL45000 and 134.0 mg of PCL80000 films in 24 h. The addition of ethanol (25 %) improves the degradation efficiency ~2.5 fold in the case of GD-95RM. In the case of GDEst-lip, 50 % methanol was found to be the optimal alcohol solution and the degradation efficiency was increased by ~3.25 times. The addition of alcohols not only increased degradation speeds but also allowed for simultaneous synthesis of industrially valuable 6-hydroxyhexonic acid esters. The suggested system is an attractive approach for removing of plastic waste and supports the principles of bioeconomics.

Probing the Effects of Antimicrobial-Lysozyme Derivatization on Enzymatic Degradation of Poly(ε-caprolactone) Film and Fiber

Surface derivatization is essential for incorporating unique functionalities into biodegradable polymers. Nonetheless, its precise effects on enzymatic biodegradation still lack comprehensive understanding. In this study, a facile solution-based method is employed to surface derivatize poly(ε-caprolactone) films and electrospun fibers with lysozyme, aiming to impart antimicrobial properties and examine the impact on enzymatic degradation. The derivatized films and fibers have shown high antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Through gravimetric analysis, it is observed that the degradation rate experiences a slight decrease upon lysozyme derivatization. However, this reduction is effectively countered by the inclusion of Tween-20, as affirmed by isothermal titration calorimetry. Comparing films and fibers, the latter undergoes degradation at a more accelerated pace, coupled with a rapid decline in molecular weight. This study provides valuable insights into the factors influencing the degradation of surface-derivatized biopolymers through electrospinning, offering a simple strategy to mitigate biomaterial-associated infections.

Antimicrobial and Biodegradable 3D Printed Scaffolds for Orthopedic Infections

In bone tissue engineering, the performance of scaffolds underpins the success of the healing of bone. Microbial infection is the most challenging issue for orthopedists. The application of scaffolds for healing bone defects is prone to microbial infection. To address this challenge, scaffolds with a desirable shape and significant mechanical, physical, and biological characteristics are crucial. 3D printing of antibacterial scaffolds with suitable mechanical strength and excellent biocompatibility is an appealing strategy to surmount issues of microbial infection. The spectacular progress in developing antimicrobial scaffolds, along with beneficial mechanical and biological properties, has sparked further research for possible clinical applications. Herein, the significance of antibacterial scaffolds designed by 3D, 4D, and 5D printing technologies for bone tissue engineering is critically investigated. Materials such as antibiotics, polymers, peptides, graphene, metals/ceramics/glass, and antibacterial coatings are used to impart the antimicrobial features for the 3D scaffolds. Polymeric or metallic biodegradable and antibacterial 3D-printed scaffolds in orthopedics disclose exceptional mechanical and degradation behavior, biocompatibility, osteogenesis, and long-term antibacterial efficiency. The commercialization aspect of antibacterial 3D-printed scaffolds and technical challenges are also discussed briefly. Finally, the discussion on the unmet demands and prevailing challenges for ideal scaffold materials for fighting against bone infections is included along with a highlight of emerging strategies in this field.

Bacterial degradation kinetics of poly(Ɛ-caprolactone) (PCL) film by Aquabacterium sp. CY2-9 isolated from plastic-contaminated landfill

Despite the identification of numerous bioplastic-degrading bacteria, the inconsistent rate of bioplastic degradation under differing cultivation conditions limits the intercomparison of results on biodegradation kinetics. In this study, we isolated a poly (Ɛ-caprolactone) (PCL)-degrading bacterium from a plastic-contaminated landfill and determined the principle-based biodegradation kinetics in a confined model system of varying cultivation conditions. Bacterial degradation of PCL films synthesized by different polymer number average molecular weights (M_n) and concentrations (% w/v) was investigated using both solid and liquid media at various temperatures. As a result, the most active gram-negative bacterial strain at ambient temperature (28 °C), designated CY2-9, was identified as Aquabacterium sp. Based on 16 S rRNA gene analysis. A clear zone around the bacterial colony was apparently exhibited during solid cultivation, and the diameter sizes increased with incubation time. During biodegradation processes in the PCL film, the thermal stability declined (determined by TGA; weight changes at critical temperature), whereas the crystalline proportion increased (determined by DSC; phase transition with temperature increment), implying preferential degradation of the amorphous region in the polymer structure. The surface morphologies (determined by SEM; electron optical system) were gradually hydrolyzed, creating destruction patterns as well as alterations in functional groups on film surfaces (determined by FT-IR; infrared spectrum of absorption or emission). In the kinetic study based on the weight loss of the PCL film (4.5 × 10⁴ Da, 1% w/v), ∼1.5 (>±0.1) × 10^-1 day^-1 was obtained from linear regression for both solid and liquid media cultivation at 28 °C. The biodegradation efficiencies increased proportionally by a factor of 2.6-7.9, depending on the lower polymer number average molecular weight and lower concentration. Overall, our results are useful for measuring and/or predicting the degradation rates of PCL films by microorganisms in natural environments.

Biomedical applications of biodegradable polycaprolactone-functionalized magnetic iron oxides nanoparticles and their polymer nanocomposites

Magnetic nanoparticles (MNPs) have gained significant attention among several nanoscale materials during the last decade due to their unique properties. These properties make them successful nanofillers for drug delivery and a number of new biomedical applications. MNPs are more useful when combined with biodegradable polymers. In this review, we discussed the synthesis of polycaprolactones (PCL) and the various methods of synthesizing magnetic iron oxide nanoparticles. Then, the synthesis of composites that is made of PCL and magnetic materials (with special focus on iron oxide nanoparticles) were highlighted. In addition, we comprehensively reviewed their application in drug delivery, cancer treatment, wound healing, hyperthermia, and bone tissue engineering. Other biomedical applications of the magnetic PCL such as mitochondria targeting are highlighted. Moreover, biomedical applications of magnetic nanoparticles incorporated into other synthetic polymers apart from PCL are also discussed. Thus, great progress and better outcome with functionalized MNPs enhanced with polycaprolactone has been recorded with the biomedical applications of drug delivery and recovery of bone tissues.

Characterization Techniques of Polymer Aging: From Beginning to End

Polymers have been widely applied in various fields in the daily routines and the manufacturing. Despite the awareness of the aggressive and inevitable aging for the polymers, it still remains a challenge to choose an appropriate characterization strategy for evaluating the aging behaviors. The difficulties lie in the fact that the polymer features from the different aging stages require different characterization methods. In this review, we present an overview of the characterization strategies preferable for the initial, accelerated, and late stages during polymer aging. The optimum strategies have been discussed to characterize the generation of radicals, variation of functional groups, substantial chain scission, formation of low-molecular products, and deterioration in the polymers' macro-performances. In view of the advantages and the limitations of these characterization techniques, their utilization in a strategic approach is considered. In addition, we highlight the structure-property relationship for the aged polymers and provide available guidance for lifetime prediction. This review could allow the readers to be knowledgeable of the features for the polymers in the different aging stages and provide access to choose the optimum characterization techniques. We believe that this review will attract the communities dedicated to materials science and chemistry.

Polycaprolactone-collagen nanofibers loaded with dexamethasone and simvastatin as an osteoinductive and immunocompatible scaffold for bone regeneration applications

Physiological inflammation has been shown to promote bone regeneration; however, prolonged inflammation impedes the osteogenesis and bone repair process. To overcome the latter we aimed to develop a dual drug delivering nanofibrous scaffold to promote osteogenic differentiation of mesenchymal stromal cells (MSCs) and modulate the pro-inflammatory response of macrophages. The polycaprolactone (PCL)-collagen nanofibrous delivery system incorporating dexamethasone and simvastatin was fabricated by electrospinning process. The morphological analysis and mRNA, as well as protein expression of proinflammatory and anti-inflammatory cytokines in human monocytes (U937 cells), demonstrated the immunocompatibility effect of dual drug-releasing nanofibrous scaffolds. Nitric oxide estimation also demonstrated the anti-inflammatory effect of dual drug releasing scaffolds. The scaffolds demonstrated the osteogenic differentiation of adipose-derived MSCs by enhancing the alkaline phosphatase (ALP) activity and mineral deposition after 17 days of cell culture. The increased expression of Runt-related transcription factor-2 (RUNX-2) and osteocalcin at mRNA and protein levels supported the osteogenic potential of dual drug-loaded fibrous scaffolds. Hence, the results indicate that our fabricated nanofibrous scaffolds exhibit immunomodulatory properties and could be employed for bone regeneration applications after further in-vivo validation.

Biobased and compostable trilayer thermoplastic films based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and thermoplastic starch (TPS)

Food preservation is crucial in safeguarding the global food supply and security. Current regulations do not encourage the use of chemical food preservatives. Therefore, creating a physical barrier in the form of packaging remains a necessary measure to prevent food contact with biological and physical contaminants. This work presents a novel biodegradable thin trilayer assembly of two sandwiching layers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and a core layer composed of thermoplastic starch (TPS), maleated TPS, or their blends with PHBV (80/20). Scanning electron microscope (SEM), and optical microscopy images showed the samples' consistent film formation. The tensile test revealed that the sample with a core layer of a blend of maleated TPS and PHBV was the strongest, with a modulus of 178 MPa. The water vapor transmission rates were as low as 20.2 g/(m²·d). The oxygen permeation rate was below the detection limit of the test. Most importantly, the samples pass the biodegradation (28 °C) disintegration test in less than six weeks. The study confirmed that a trilayer structure with two outer layers of PHBV, and a middle layer of TPS-PHBV blend provides excellent barrier properties in conjuncture with its biodegradability making it an appealing, sustainable food packaging material option.

Links among Microbial Communities, Soil Properties and Functions: Are Fungi the Sole Players in Decomposition of Bio-Based and Biodegradable Plastic?

The incomplete degradation of bio-based and biodegradable plastics (BBPs) in soils causes multiple threats to soil quality, human health, and food security. Plastic residuals can interact with soil microbial communities. We aimed to link the structure and enzyme-mediated functional traits of a microbial community composition that were present during poly (butylene succinate-co-butylene adipate (PBSA) decomposition in soil with (PSN) and without (PS) the addition of nitrogen fertilizer ((NH₄)₂SO₄). We identified bacterial (Achromobacter, Luteimonas, Rhodanobacter, and Lysobacter) and fungal (Fusarium, Chaetomium, Clonostachys, Fusicolla, and Acremonium) taxa that were linked to the activities of ß-glucosidase, chitinase, phosphatase, and lipase in plastic-amended soils. Fungal biomass increased by 1.7 and 4 times in PS and PSN treatment, respectively, as compared to non-plastic amended soil. PBSA significantly changed the relationships between soil properties (C: N ratio, TN, and pH) and microbial community structure; however, the relationships between fungal biomass and soil enzyme activities remained constant. PBSA significantly altered the relationship between fungal biomass and acid phosphatase. We demonstrated that although the soil functions related to nutrient cycling were not negatively affected in PSN treatment, potential negative effects are reasoned by the enrichment of plant pathogens. We concluded that in comparison to fungi, the bacteria demonstrated a broader functional spectrum in the BBP degradation process.

3D printed bioresorbable scaffolds for articular cartilage tissue engineering: a comparative study between neat polycaprolactone (PCL) and poly(lactide-b-ethylene glycol) (PLA-PEG) block copolymer

This work identifies and describes different material-scaffold geometry combinations for cartilage tissue engineering (CTE). Previously reported potentially interesting scaffold geometries were tuned and printed using bioresorbable polycaprolactone and poly(lactide-b-ethylene) block copolymer. Medical grades of both polymers were 3D printed with fused filament fabrication technology within an ISO 7 classified cleanroom. Resulting scaffolds were then optically, mechanically and biologically tested. Results indicated that a few material-scaffold geometry combinations present potential for excellent cell viability as well as for an enhance of the chondrogenic properties of the cells, hence suggesting their suitability for CTE applications.

Injectable electrospun fiber-hydrogel composite sequentially releasing clonidine and ropivacaine for prolonged and walking regional analgesia

Rationale: Peripheral nerve block is a traditional perioperative analgesic method for its precise pain control and low systemic toxicity. However, a single low dose of local anesthetic merely provides a few hours of analgesia, and high dose results in irreversible toxicity, whereas continuous infusion of anesthetics is expensive and complicated. Therefore, it is necessary to develop a long-acting and sensory-selective local anesthetic for safe perioperative analgesia. Methods: An injectable composite comprising ropivacaine-loaded poly (ε-caprolactone) electrospun fiber and clonidine-loaded F127 hydrogel (Fiber-Rop/Gel-Clo composite) was developed for long-acting and walking regional analgesia with barely one dose. The peripheral nerve blockade effect of the composite was evaluated in a rat sciatic nerve block model. Also, the biodegradability and biosafety of the composite was evaluated. Results: The preferentially released Clo from the hydrogel rapidly constricted the peripheral arterial vessels, reducing the blood absorption of Rop and thus enhancing the local Rop accumulation at the injection site. The subsequently sustainable release of Rop from the fiber, significantly prolonged the sciatic nerve block of rats. Remarkably, an amazing sensorimotor segregation effect was achieved, as the sensory blockade (32.0 ± 1.4 h) lasted significantly longer than the motor blockade (20.3 ± 0.9 h). Additionally, the Fiber-Rop/Gel-Clo composite presented good biodegradability and biosafety in vivo. Conclusions: Our designed Fiber-Rop/Gel-Clo composite with minimal invasion, prolonged synergistic analgesia, and strikingly sensorimotor segregation effect, posted a promising prospect for regional long-term walking analgesia in clinical treatment.

3D Culture Platform for Enabling Large-Scale Imaging and Control of Cell Distribution into Complex Shapes by Combining 3D Printing with a Cube Device

While organoid differentiation protocols have been widely developed, local control of initial cell seeding position and imaging of large-scale organoid samples with high resolution remain challenging. 3D bioprinting is an effective method to achieve control of cell positioning, but existing methods mainly rely on the use of synthetic hydrogels that could compromise the native morphogenesis of organoids. To address this problem, we developed a 3D culture platform that combines 3D printing with a cube device to enable an unrestricted range of designs to be formed in biological hydrogels. We demonstrated the formation of channels in collagen hydrogel in the cube device via a molding process using a 3D-printed water-soluble mold. The mold is first placed in uncured hydrogel solution, then easily removed by immersion in water after the gel around it has cured, thus creating a mold-shaped gap in the hydrogel. At the same time, the difficulty in obtaining high-resolution imaging on a large scale can also be solved as the cube device allows us to scan the tissue sample from multiple directions, so that the imaging quality can be enhanced without having to rely on higher-end microscopes. Using this developed technology, we demonstrated (1) mimicking vascular structure by seeding HUVEC on the inner walls of helix-shaped channels in collagen gels, and (2) multi-directional imaging of the vascular structure in the cube device. Thus, this paper describes a concerted method that simultaneously allows for the precise control of cell positioning in hydrogels for organoid morphogenesis, and the imaging of large-sized organoid samples. It is expected that the platform developed here can lead to advancements in organoid technology to generate organoids with more sophisticated structures.

Scaffolding Biomaterials for 3D Cultivated Meat: Prospects and Challenges

Cultivating meat from stem cells rather than by raising animals is a promising solution to concerns about the negative externalities of meat production. For cultivated meat to fully mimic conventional meat's organoleptic and nutritional properties, innovations in scaffolding technology are required. Many scaffolding technologies are already developed for use in biomedical tissue engineering. However, cultivated meat production comes with a unique set of constraints related to the scale and cost of production as well as the necessary attributes of the final product, such as texture and food safety. This review discusses the properties of vertebrate skeletal muscle that will need to be replicated in a successful product and the current state of scaffolding innovation within the cultivated meat industry, highlighting promising scaffold materials and techniques that can be applied to cultivated meat development. Recommendations are provided for future research into scaffolds capable of supporting the growth of high-quality meat while minimizing production costs. Although the development of appropriate scaffolds for cultivated meat is challenging, it is also tractable and provides novel opportunities to customize meat properties.

Three-Dimensional Printable Enzymatically Active Plastics

Here, we describe a facile route to the synthesis of enzymatically active highly fabricable plastics, where the enzyme is an intrinsic component of the material. This is facilitated by the formation of an electrostatically stabilized enzyme-polymer surfactant nanoconstruct, which, after lyophilization and melting, affords stable macromolecular dispersions in a wide range of organic solvents. A selection of plastics can then be co-dissolved in the dispersions, which provides a route to bespoke 3D enzyme plastic nanocomposite structures using a wide range of fabrication techniques, including melt electrowriting, casting, and piston-driven 3D printing. The resulting constructs comprising active phosphotriesterase (arPTE) readily detoxify organophosphates with persistent activity over repeated cycles and for long time periods. Moreover, we show that the protein guest molecules, such as arPTE or sfGFP, increase the compressive Young's modulus of the plastics and that the identity of the biomolecule influences the nanomorphology and mechanical properties of the resulting materials. Overall, we demonstrate that these biologically active nanocomposite plastics are compatible with state-of-the-art 3D fabrication techniques and that the methodology could be readily applied to produce robust and on-demand smart nanomaterial structures.

Synergistic Enzyme Mixtures to Realize Near-Complete Depolymerization in Biodegradable Polymer/Additive Blends

Embedding catalysts inside of plastics affords accelerated chemical modification with programmable latency and pathways. Nanoscopically embedded enzymes can lead to near-complete degradation of polyesters via chain-end mediated processive depolymerization. The overall degradation rate and pathways have a strong dependence on the morphology of semicrystalline polyesters. Yet, most studies to date focus on pristine polymers instead of mixtures that contain additives and other components despite their nearly universal use in plastic production. Here, additives are introduced to purposely change the morphology of polycaprolactone (PCL) by increasing the bending and twisting of crystalline lamellae. These morphological changes immobilize chain ends preferentially at the crystalline/amorphous interfaces and limit chain-end accessibility by the embedded processive enzyme. This chain-end redistribution reduces the polymer-to-monomer conversion from >95% to less than 50%, causing formation of highly crystalline plastic pieces, including microplastics. By synergizing both random chain scission and processive depolymerization, it is feasible to navigate morphological changes in polymer/additive blends and to achieve near-complete depolymerization. The random scission enzymes in the amorphous domains create new chain ends that are subsequently bound and depolymerized by processive enzymes. Present studies further highlight the importance to consider how the host polymer's morphologies affect the reactions catalyzed by embedded catalytic species.

Bioremediation: an alternative approach for detoxification of polymers from the contaminated environment

The industries and metropolitan wastes produced by anthropogenic activities are of great concern for nature as it causes soil contamination and deteriorate the environment. Plastic utilization is rapidly enhancing globally with passing days that last for a more extended period in the environment due to slow decomposition and natural degradation. Excessive use of polymer has risked the life of both marine, freshwater and terrestrial organisms. Lack of proper waste management and inappropriate disposal leads to environmental threats. Bioremediation processes involve microbes such as fungi, bacteria, etc. which contribute a crucial role in the breakdown of plastics. Extremophiles secrete extremozymes that are functionally active in extreme conditions and are highly crucial for polymer disaggregation in those conditions.

Experimental Analysis of the Enzymatic Degradation of Polycaprolactone: Microcrystalline Cellulose Composites and Numerical Method for the Prediction of the Degraded Geometry

The degradation rate of polycaprolactone (PCL) is a key issue when using this material in Tissue Engineering or eco-friendly packaging sectors. Although different PCL-based composite materials have been suggested in the literature and extensively tested in terms of processability by material extrusion additive manufacturing, little attention has been paid to the influence of the fillers on the mechanical properties of the material during degradation. This work analyses the possibility of tuning the degradation rate of PCL-based filaments by the introduction of microcrystalline cellulose into the polymer matrix. The enzymatic degradation of the composite and pure PCL materials were compared in terms of mass loss, mechanical properties, morphology and infrared spectra. The results showed an increased degradation rate of the composite material due to the presence of the filler (enhanced interaction with the enzymes). Additionally, a new numerical method for the prediction of the degraded geometry was developed. The method, based on the Monte Carlo Method in an iterative process, adjusts the degradation probability according to the exposure of each discretized element to the degradation media. This probability is also amplified depending on the corresponding experimental mass loss, thus allowing a good fit to the experimental data in relatively few iterations.

3D-Printed Enzyme-Embedded Plastics

A simple and environmentally friendly approach toward the thermoplastic processing of rapidly degradable plastic-enzyme composites using three-dimensional (3D) printing techniques is described. Polycaprolactone/Amano lipase (PCL/AL) composite films (10 mm × 10 mm; height [h] = ∼400 μm) with an AL loading of 0.1, 1.0, and 5.0% were prepared via 3D printing techniques that entail direct mixing in the solid state and thermal layer-by-layer extrusion. It was found that AL can tolerate in situ processing temperatures up to 130 °C in the solid-state for 60 min without loss of enzymatic activity. The composites were degraded in phosphate buffer (8 mg/mL, composite to buffer) for 7 days at 37 °C and the resulting average percent total weight loss (WL_avg %) was found to be 5.2, 92.9, and 100%, for the 0.1, 1.0, and 5.0% films, respectively. The degradation rates of PCL/AL composites were found to be faster than AL applied externally in the buffer. Thicker PCL/AL 1.0% films (10 mm × 10 mm; h = ∼500 μm) were also degraded over a 7 day period to examine how the weight loss occurs over time with 3.0, 18.1, 36.4, 46.4, and 70.2% weight loss for days 1, 2, 3, 4, and 7, respectively. Differential scanning calorimetry (DSC) analysis shows that the film's percent crystallinity (D_xtal%) increases over time with D_xtal% = 46.5 for day 0 and 53.1% for day 7. Scanning electron microscopy (SEM) analysis found that film erosion begins at the surface and that water can penetrate the interior via surface pores activating the enzymes embedded in the film. Controlled release experiments utilizing dye-loaded PCL/AL/dye (AL = 1.0%; dye = 0.1%) composites were degraded over a 7 day period with the bulk of the dye released by the fourth day. The PCL/AL multimaterial objects containing AL-resistant polylactic acid (PLA) were also printed and degraded to demonstrate the application of this material on more complex structures.

High-precision, gelatin-based, hybrid, bilayer scaffolds using melt electro-writing to repair cartilage injury

Articular cartilage injury is a common disease in the field of orthopedics. Because cartilage has poor self-repairing ability, medical intervention is needed. Using melt electro-writing (MEW) technology, tissue engineering scaffolds with high porosity and high precision can be prepared. However, ordinary materials, especially natural polymer materials, are difficult to print. In this study, gelatin was mixed with poly (lactic-co-glycolic acid) to prepare high-concentration and high-viscosity printer ink, which had good printability and formability. A composite scaffold with full-layer TGF-β1 loading mixed with hydroxyapatite was prepared, and the scaffold was implanted at the cartilage injury site; microfracture surgery was conducted to induce the mesenchyme in the bone marrow. Quality stem cells thereby promoted the repair of damaged cartilage. In summary, this study developed a novel printing method, explored the molding conditions based on MEW printing ink, and constructed a bioactive cartilage repair scaffold. The scaffold can use autologous bone marrow mesenchymal stem cells and induce their differentiation to promote cartilage repair.

Fabrication of 3D printed antimicrobial polycaprolactone scaffolds for tissue engineering applications

Synthetic polymers are widely employed for bone tissue engineering due to their tunable physical properties and biocompatibility. Inherently, most of these polymers display poor antimicrobial properties. Infection at the site of implantation is a major cause for failure or delay in bone healing process and the development of antimicrobial polymers is highly desired. In this study, silver nanoparticles (AgNps) were synthesized in polycaprolactone (PCL) solution by in-situ reduction and further extruded into PCL/AgNps filaments. Customized 3D structures were fabricated using the PCL/AgNps filaments through 3D printing technique. As demonstrated by scanning electron microscopy, the 3D printed scaffolds exhibited interconnected porous structures. Furthermore, X-ray photoelectron spectroscopy analysis revealed the reduction of silver ions. Transmission electron microscopy along with energy-dispersive X-ray spectroscopy analysis confirmed the formation of silver nanoparticles throughout the PCL matrix. In vitro enzymatic degradation studies showed that the PCL/AgNps scaffolds displayed 80% degradation in 20 days. The scaffolds were cytocompatible, as assessed using hFOB cells and their antibacterial activity was demonstrated on Escherichia coli. Due to their interconnected porous structure, mechanical and antibacterial properties, these cytocompatible multifunctional 3D printed PCL/AgNps scaffolds appear highly suitable for bone tissue engineering.

Monodisperse oligo(δ-valerolactones) and oligo(ε-caprolactones) with docosyl (C22) end-groups

Two different families of monodisperse oligoesters with α-hydroxyl-ω-docosyl (C₂₂) terminal groups [oligo(δ-valerolactone) and oligo(ϵ-caprolactone)] were isolated by flash column chromatography (FCC).