Degradation Of PCL Research Articles

Fabrication of Vascular Grafts Using Poly(ε-Caprolactone) and Collagen-Encapsuled ADSCs for Interposition Implantation of Abdominal Aorta in Rhesus Monkeys.

The production of small-diameter artificial vascular grafts continues to encounter numerous challenges, with concerns regarding the degradation rate and endothelialization being particularly critical. In this study, porous PCL scaffolds were prepared, and PCL vascular grafts were fabricated by 3D bioprinting of collagen materials containing adipose-derived mesenchymal stem cells (ADSCs) on the internal wall of the porous PCL scaffold. The PCL vascular grafts were then implanted in the abdominal aorta of Rhesus monkeys for up to 640 days to analyze the degradation of the scaffolds and regeneration of the aorta. Changes in surface morphology, mechanical properties, crystallization property, and molecular weight of porous PCL revealed a similar degradation process of PCL in PBS at pH 7.4 containing Thermomyces lanuginosus lipase and in situ in the abdominal aorta of rhesus monkeys. The contrast of in vitro and in vivo degradation provided valuable reference data for predicting in vivo degradation based on in vitro enzymatic degradation of PCL for further optimization of PCL vascular graft fabrication. Histological analysis through hematoxylin and eosin (HE) staining and fluorescence immunostaining demonstrated that the PCL vascular grafts successfully induced vascular regeneration in the abdominal aorta over the 640-day period. These findings provided valuable insights into the regeneration processes of the implanted vascular grafts. Overall, this study highlights the significant potential of PCL vascular grafts for the regeneration of small-diameter blood vessels.

Exploring the substrate spectrum of phylogenetically distinct bacterial polyesterases.

The rapid escalation of plastic waste accumulation presents a significant threat of the modern world, demanding an immediate solution. Over the last years, utilization of the enzymatic machinery of various microorganisms has emerged as an environmentally friendly asset in tackling this pressing global challenge. Thus, various hydrolases have been demonstrated to effectively degrade polyesters. Plastic waste streams often consist of a variety of different polyesters, as impurities, mainly due to wrong disposal practices, rendering recycling process challenging. The elucidation of the selective degradation of polyesters by hydrolases could offer a proper solution to this problem, enhancing the recyclability performance. Towards this, our study focused on the investigation of four bacterial polyesterases, including DaPUase, IsPETase, PfPHOase, and Se1JFR, a novel PETase-like lipase. The enzymes, which were biochemically characterized and structurally analyzed, demonstrated degradation ability of synthetic plastics. While a consistent pattern of polyesters' degradation was observed across all enzymes, Se1JFR stood out in the degradation of PBS, PLA, and polyether PU. Additionally, it exhibited comparable results to IsPETase, a benchmark mesophilic PETase, in the degradation of PCL and semi-crystalline PET. Our results point out the wide substrate spectrum of bacterial hydrolases and underscore the significant potential of PETase-like enzymes in polyesters degradation.

Degradation of Poly(ε-caprolactone) Resorbable Multifilament Yarn under Physiological Conditions.

Poly(ε-caprolactone) (PCL) is a hydrophobic, resorbable aliphatic polymer recognized for its low tenacity and extensive elongation at break, making it a popular choice for fabricating biodegradable tissue engineering scaffolds. PCL's slow degradation rate typically results in a complete resorption period of 2 to 3 years. While numerous studies have examined the degradation of PCL in various forms such as films and webs, no study to date has investigated its physiological degradation in multifilament yarn form. In this study, we subjected PCL multifilament yarn samples to physiological conditions in phosphate-buffered saline (PBS) maintained at a consistent temperature of 37 ± 2 °C and agitated at 45 rpm for a period of 32 weeks. We retrieved samples at five different intervals to analyze the degradation profile of the multifilament yarn. This allowed us to estimate the complete resorption time and rate under these in vitro conditions. Over the 32-week period, the multifilament yarn's mass decreased by 4.8%, its elongation at break declined by 42%, the tenacity dropped by 40%, and the peak load at break fell by 46.5%. Based on these findings, we predict that a scaffold structure incorporating PCL multifilament yarn would undergo complete resorption in approximately 14 months under physiological conditions, such as in PBS solution at a pH of approximately 7 and a temperature of 37 °C.

A Thermostable Lipase Isolated from Brevibacillus thermoruber Strain 7 Degrades Ɛ-Polycaprolactone.

The tremendous problem with plastic waste accumulation has determined an interest in biodegradation by effective degraders and their enzymes, such as thermophilic enzymes, which are characterized by high catalytic rates, thermostability, and optimum temperatures close to the melting points of some plastics. In the present work, we report on the ability of a thermophilic lipase, by Brevibacillus thermoruber strain 7, to degrade Ɛ-polycaprolactone (PCL), as well as the enzyme purification, the characterization of its physicochemical properties, the product degradation, and its disruptive effect on the PCL surface. The pure enzyme showed the highest reported optimum temperature at 55 °C and a pH of 7.5, while its half-life at 60 °C was more than five hours. Its substrate specificity referred the enzyme to the subgroup of lipases in the esterase group. A strong inhibitory effect was observed by detergents, inhibitors, and Fe3+ while Ca2+ enhanced its activity. The monomer Ɛ-caprolactone was a main product of the enzyme degradation. Similar elution profiles of the products received after treatment with ultra-concentrate and pure enzyme were observed. The significant changes in PCL appearance comprising the formation of shallower or deeper in-folds were observed after a week of incubation. The valuable enzyme properties of the lipase from Brevibacillus thermoruber strain 7, which caused a comparatively quick degradation of PCL, suggests further possible exploration of the enzyme for effective and environment-friendly degradation of PCL wastes in the area of thermal basins, or in thermophilic remediation processes.

The Stability Consequences Promoted by Doping Metallic Atoms on the Degradation of Poly (ε-Caprolactone)

The stability of polymer materials is essentially determined by the molecular structure and the presence of additives and impurities. When a polymer substrate is subjected to vigorous damage by an energetic treatment, the molecular scission generates fragments, which may be oxidized by the diffused oxygen. The traces of oxide catalysts that may be accidentally incorporated into the polymer materials initiate a faster oxidation that influences the material durability. This study presents the behavior of poly (ε-caprolactone) (PCL) loaded with 2 wt% PbZrO3 previously doped with foreign atoms (Cr, Nd, Mg, Mn, Ti) at the concentration of 0.1 mol%. The investigation procedure, chemiluminescence, reveals the acceleration of the degradation of PCL. The contribution of the metallic traces existing in the structure of PbTiO3 powder is characterized by the activation energies (Ea) involved in the propagation of oxidation. The free radicals are involved in a faster oxidation, when the polymer substrate is heated at superior rates. The comparison of the oxidation levels at the extended period of heating and irradiation indicates the sustained activities of metallic traces acting in oxide powder fillers, especially at temperatures exceeding 150 °C. The essential considerations on material strength against oxidation are presented.

Macrophage-Targeting and Complete Lysosomal Degradation of Self-assembled Two-Dimensional Poly(ε-caprolactone) Platelet Particles.

Understanding cellular uptake and particle trafficking within the cells is essential for targeted drug delivery applications. Existing studies reveal that the geometrical aspects of nanocarriers, for example, shape and size, determine their cell uptake and sub-cellular transport pathways. However, considerable efforts have been directed toward understanding the cell uptake mechanism and trafficking of spherical particles. Detailed analysis on the uptake mechanism and downstream intracellular processing of non-spherical particles remains elusive. Here, we used polymeric two-dimensional platelets based on poly(ε-caprolactone) (PCL) prepared by living crystallization-driven self-assembly as a platform to investigate the cell uptake and intracellular transport of non-spherical particles in vitro. PCL is known to degrade only slowly, and these platelets were still stable after 2 days of incubation in artificial lysosomal media. Upon cell uptake, the platelets were transported through an endo/lysosomal pathway and were found to degrade completely in the lysosome at the end of the cell uptake cycle. We observed a morphological transformation of the lysosomes, which correlates with the stages of platelet degradation in the lysosome. Overall, we found an accelerated degradation of PCL, which was likely caused by mechanical forces inside the highly stretched endosomes.

Biochar as a sustainable and renewable additive for the production of Poly(ε-caprolactone) composites

Sustainable poly(ε-caprolactone) (PCL) composites can be produced via initiation of polymerization using the surface hydroxyl groups of oxidized biochar nanostructures obtained after liquid-phase exfoliation of biochar. Biochars are stable, renewable, and sustainable carbon-based materials, which in large-scale applications have the potential to mitigate climate change. The biochar used herein is produced by pyrolysis of hardwood waste biomass (e.g. sawdust, branches, bark) and then converted using nitric acid to oxidized biochar (oxbc). Oxbc is directly sonicated in ε-caprolactone to produce the exfoliated analogue (Eoxbc), which is used to promote the ring-opening polymerization of ε-caprolactone. Eoxbc is highly dispersible in this monomer, and thus reactions can be performed under neat conditions. Eoxbc presents sufficient surface hydroxyl groups (−OH) to initiate and facilitate the ring-opening polymerization of ε-caprolactone using tin octoate, organic bases or lipase enzymes as catalysts. The PCL/Eoxbc composites produced present higher crystallinity and increased stiffness when compared to pure PCL. In preliminary studies, Eoxbc also shows a positive effect upon the degradation of PCL under various conditions.

Effect of poly(ε‐caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε‐caprolactone) blends

AbstractThe effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε‐caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO2) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO2 in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO2 nanocomposites. The X‐ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO2 retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO2 played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO2 were significantly reduced through weathering exposure and the incorporation of TiO2.

Electrohydrodynamic 3D Printing Scaffolds for Repair of Achilles Tendon Defect in Rats.

Tissue engineering (TE) studies for Achilles tendon (AT) defects are a difficult and popular field in orthopedic medical practice. In this study, we applied electrohydrodynamic three-dimensional (3D) printing technology to construct scaffolds made of poly-(ɛ-ɛ-caprolactone) (PCL) and Pluronic F127 (F127) with different mass-volume ratios. The fibers and porous capabilities of the scaffolds were controlled using this technology. We found that F127 improved the hydrophilicity and degradation of PCL in vitro. The PCL scaffolds with 5% F127 were mostly favorable for cell adhesion and growth, suggesting that the scaffolds had good biocompatibility in vitro. Scaffolds with 5% F127 seeded with C3H10T1/2 cells were transplanted into AT defects in rats. A histological analysis indicated that the TE scaffolds were beneficial for the accumulation and arrangement of collagen fibers. Thus, this study provides fundamental experimental data for future clinical applications regarding TE for ATs. Impact statement Electrohydrodynamic three-dimensional (3D) printing can be used to construct tissue-engineered scaffolds with controllable fibers and good porosity. Pluronic-F127 (F127) improved the hydrophilicity and degradation of the poly-(ɛ-ɛ-caprolactone) (PCL), and a better microscale structure was obtained. The scaffolds with 5% F127, with good pore structures, were favorable for C3H10T1/2 cell growth and cellular morphology, indicating that they had good biocompatibility. In vivo transplantation experiments showed that scaffolds with 5% F127 improved the arrangement of collagen fibers, encouraging their potential application in the construction of future tissue-engineered tendons.

Poly(ε-caprolactone)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Blend from Fused Deposition Modeling as Potential Cartilage Scaffolds

The scaffolds of poly(ε-caprolactone)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PCL/PHBV) blends were fabricated from fused deposition modeling. From indirect cytotoxicity testing based on mouse fibroblasts, all scaffolds with various blend ratios were nontoxic to cells. The surface-treated scaffold with a blend ratio of 25/75 PCL/PHBV exhibited the highest proliferation of porcine chondrocytes and total glycosaminoglycans (GAGs) after 21 days of culture. The scaffolds with a blend ratio of 25/75 with local pores (LP) were prepared from FDM along with a salt leaching technique using NaCl as porogens. The effect of NaOH in surface treatment on the biological property of scaffolds was investigated. The scaffolds with LP and with 1 M NaOH surface treatment exhibited the highest proliferation of cells and total GAGs after 28 days of culture. The degradation behaviors of the scaffolds were studied. The nonsurface treated, surface treated without LP, and surface treated with LP scaffolds were degraded in phosphate buffer (pH 7.4) for 30 days at 37°C and 50°C for nonenzymatic condition and at 37°C for enzymatic condition. The surface treated with LP scaffold showed the highest amount of weight loss, followed by the surface treated without LP, and the nonsurface-treated scaffolds without LP, respectively. The results from Fourier-transform infrared spectroscopy indicated degradation of PCL and PHBV through hydrolysis of the ester functional group. The compressive strengths of all scaffolds were sufficiently high. The results suggested that the scaffolds with the existence of LP and with surface treatment showed the highest potential for use as cartilage scaffolds.

Confined crystallization and degradation of six-arm star PCL with core of cyclotriphosphazene in epoxy thermosets

Six-arm star polycaprolactone with core of cyclotriphosphazene (s-PCL) was synthesized via ring-opening polymerization and characterized by NMR and GPC. Epoxy thermosets incorporating 10–40 wt% of this copolymer were cured with 4,4′-methylenebis(2-chloroaniline) (MOCA) and 4,4′-diaminodiphenyl sulfone (DDS), respectively. In these thermosets, intermolecular specific interactions had a significant impact on their morphologies. Specifically, no discernable macroscopic phase separation was found in FESEM images of MOCA-cured epoxy resins. However, for the DDS-cured system, s-PCL was partially miscible with the epoxy thermosets, as evidenced with FTIR and DMA. This is may be owning to enriched concentration of hydroxyl groups in the s-PCL favored the miscibility between PCL subchains of carbonyl and the epoxy matrix. Dispersed phase, further confirmed by XRD to be amorphous, with a diameter of 0.34–0.44 μm could be observed (s-PCL’ content ≤ 20 wt%) in this system. Nevertheless, crystallization of PCL could not be suppressed completely (s-PCL’ content > 30 wt%). Besides, epoxy thermosets containing crystalline PCL were found to be more resistant to thermal degradation but sensitive to alkaline degradation (10% NaOH aqueous solution) according to TGA and FESEM results. This work presented here is a meaningful report on the presence of alkaline-labile crosslinking points through the whole networks.

The highly cross-linked poly(ε-caprolactone) as biodegradable implants for prostate cancer treatment-part I: Synthesis and in vivo degradation

Highly cross-linked poly(ε-caprolactone) (PCL) was fabricated via the ring-opening (co)polymerization of ε-caprolactone with/without 30 mol% trimethylene carbonate (TMC), using 4~6mol% bis-CL or bis-TMC as the cross-linker. The in vivo degradation behavior of the obtained cross-linked PCL implants was investigated via the subcutaneous implantation into the back of rats to evaluate the possibility of the cross-linked PCL as the carrier material of the biodegradable implants. The results showed that the obtained cross-linked PCL implants had a slow degradation rate with mass loss of less than 13% after 48 weeks of degradation in vivo. The introduction of 30 mol% TMC endowed a faster degradation rate to the cross-linked PCL with a mass loss of 19.69% after 48 weeks. Furthermore, the cross-linked PCL implants presented good form-stability with no observation of deformation was found during the in vivo degradation. The SEM observation indicated that the degradation of cross-linked PCL in vivo occurred via the surface erosion mechanism. The cross-linked PCL had great potential application as the carrier material for the long-term biodegradable implants.

Development of double porous poly (ε - caprolactone)/chitosan polymer as tissue engineering scaffold.

Polymer blend made from poly(ε - caprolactone)/chitosan (PCL/CHT) offers interesting opportunities for biological applications. The paper presents a new way to fabricate PCL/CHT double-porosity (macrovoids with interconnected microporosity) membrane materials from a chemical optimization of the solvent and non-solvent phases and from a modified phase inversion technique. By varying the PCL/CHT proportion, it is shown that it is possible to improve the chemical and physical properties of the CHT carbohydrate polymer. The PCL/CHT membranes are fully characterized in term of physico-chemical properties (ATR-FTIR, XRD and DSC) to understand the miscibility of the two-polymer blend. Morphological characterization by SEM shows that by increasing CHT wt% in the blend, the size of the macrovoids was increasing. Rapid enzymatic degradation of PCL from all the blend was found by using lipase (from P. cepacia). The mechanisms at the origin of the morphological structuration of the material is also discussed. To test the ability to operate these materials as small diameter vascular scaffolds, cell culture with human umbilical vein endothelial cells (HUVECs) were carried out on the membrane and the results analyzed with laser scanning confocal microscopy (LSCM). Data suggest that the blend membrane with higher concentration of CHT polymer wt% have suitable properties that promote high number of cells on the surface by maintaining cellular cytoskeleton integrity within 3 days. The blend membrane with a double porous morphology could be potentially applicable in future for small diameter vascular graft application. The surface macrovoids (20-90 μm) could be useful for three-dimensional cellular adhesion and proliferation and interconnected microporous spongy network (7-20 μm) is expected to transfer essential nutrients, oxygen, growth factor between the macrovoids and the supernatant.

In-vitro biodegradation study of poly(ε-caprolactone) films using a 3D printed helical flow prototype to simulate the physiological conditions for cardiovascular implanted devices

Current in-vitro biodegradation test methods for characterizing bioabsorbable polymer implants including ASTM F1635-11, focus on testing mechanical and chemical properties of samples under static conditions. These tests oversimplify the implant service environment and yield limited data due to the lack of fluid flow, stresses, and pressures. The effects of the helical or spiral blood flow observed in arterial vessels are of particular interest for biodegradable polymer cardiovascular stents due to its promising biomedical uses and relatively recent discovery. In this study, a novel 3D printed prototype flow device was designed and developed to simulate in-vivo conditions including flow rates, flow characteristics, pressures, temperatures, and chemical environment. The in-vitro biodegradation behavior of poly(ε-caprolactone) (PCL), in phosphate buffer solution (PBS) was used to study the influence of flow conditions compared to a standard static ASTM method over 5 weeks. Characterization of the polymer degradation was performed by evaluating changes in weight loss, molecular weight and the degree of crystallinity as a function of time. The number average molecular weight of the polymer showed the largest decline, decreasing linearly with time by 22% and 5% for the samples tested using the flow device and ASTM method, respectively. Similarly, the degree of crystallinity was found to increase linearly by 16% and 6% for the flow device and ASTM method, respectively. Helical/spiral flow at the flow rates as low as 1 cm3 s−1 were found to enhance the bulk degradation of PCL by up to 80% when compared to the static ASTM method. A combination of bulk and surface erosion mechanisms were proposed for the degradation behavior of the PCL in the flow prototype. This indicates that by more accurately mimicking physiological conditions, including blood dynamics, this 3D printed prototype can serve as an improved method for testing bioabsorbable and biodegradable polymers for implanted devices.

Enzymatic degradation of fluorinated Poly(ε-caprolactone) (PCL) block copolymer films with improved hydrophobicity

Fluorinated Poly(ε-caprolactone) (PCL) block copolymers PCL-PTFOA(2 h), PCL-PTFOA(4 h), PCL-PTFOA(6 h), PCL-PTFOA(8 h) were prepared via esterification by using poly(1H,1H,2H,2H-perfluorooctylacrylate) (PTFOA) with different molecular weights as reactants. It was found that PCL-PTFOA(6 h) and PCL-PTFOA(8 h) possessed the similar molecular weight via GPC analysis. PCL and fluorinated PCL block copolymers films were prepared by solution casting method. The structure and properties of film surface of the fluorinated PCL block copolymers were analyzed by energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), Differential scanning calorimetry (DSC), water contact angles (WCAs) and the surface free energy. The results showed that the fluorinated PCL films possessed improved hydrophobicity because of the microphase separation between fluoropolymer chain and PCL chain. The enzymatic degradation of PCL, PCL-PTFOA(2 h), PCL-PTFOA(4 h) and PCL-PTFOA(6 h) films were performed at 37 °C in a phosphate buffer solution (PBS, 0.1 M, with a pH of 7.2–7.4) with lipase and analyzed by weight loss, SEM and EDS. It was found that the introduction of fluorine-containing segment reduced the rate of enzymatic degradation of the copolymer film in the early period, while increased the finally weight loss rate with a prolonged time. In addition, the enzymatic degradation rate of PCL-PTFOA(2 h) film and PCL-PTFOA(4 h) film was faster than that of PCL-PTFOA(6 h) film.

Lightweight Poly(ε-Caprolactone) Composites with Surface Modified Hollow Glass Microspheres for Use in Rotational Molding: Thermal, Rheological and Mechanical Properties.

In this work, novel composites based on poly(ε-caprolactone) (PCL) were prepared and characterized in terms of morphological, thermal, rheological and mechanical properties. Hollow glass microspheres (HGM), alone or surface modified by treatment with (3-aminopropyl)triethoxysilane (APTES) in order to enhance the compatibility between the inorganic particles and the polymer matrix, were used to obtain lightweight composites with improved properties. The silanization treatment implies a good dispersion of filler particles in the matrix and an enhanced filler–polymer adhesion. The addition of HGM to PCL has relevant implications on the rheological and mechanical properties enhancing the stiffness of the material. Furthermore, the presence of HGM strongly interferes with the crystallization behavior and thermo-oxidative degradation of PCL. The increase of PCL crystallization rate was observed as a function of the HGM amount in the composites. Finally, rotational molding tests demonstrated the possibility of successfully producing manufactured goods in PCL and PCL-based composites on both a laboratory and industrial scale.

Non-isothermal Crystallization and Degradation Kinetics of Fe3O4–Thymolblue Functionalized Poly(ε-caprolactone)

The Fe3O4–thymolblue (TB) functionalized or end capped poly(e-caprolactone) (PCL) was synthesized by ring opening polymerization (ROP) of e-caprolactone (CL) with Fe3O4–TB nanohybrid as an effective initiator in the presence of stannous octoate (SO) as a catalyst. The main aim of the present work is to analyze the influence of polymer chain end capping agent or functionalization agent on the structure–property relationship particularly, crystallization and thermal degradation behavior of PCL under non-isothermal condition. The structure of the polymer was analyzed using FTIR and NMR spectra. The particle size of the incorporated Fe3O4–TB nanohybrid in PCL matrix was found to be less than 20 nm by TEM. The surface morphology, skewness moment and surface roughness were analysed by AFM. The spherulitic growth of the nucleated polymer crystals was confirmed by POM. The spherulitic growth was further verified with various kinetic models. The melting and crystallization behaviors under non-isothermal condition were assessed by DSC. Various kinetic models were employed to comprehend the degradation behavior of Fe3O4–TB functionalized PCL and its associated kinetic parameters under non-isothermal condition. The energy of activation (Ea) for the crystallization and thermal degradation of PCL were found to be 132 and nearly 140 kJ/mol respectively.

Effect of benign solvents composition on poly(ε-caprolactone) electrospun fiber properties

Green electrospinning is a flourishing trend in the field of electrospinning (ES) of polymeric/composite materials for biomedical applications. The use of non-toxic solvents instead of the most commonly used solvents in electrospinning is needed to avoid the possible presence toxic solvents traces in the electrospun mats, enhancing their cytocompatibility. It was found that a single solvent or solvent mixtures have a critical role in fiber formation and properties. In this work, fibers in the micro/nanoscale were obtained by electrospinning technique from different poly(ε-caprolactone) (PCL) solutions. Benign solvents (i.e. acetic and formic acids, water and their mixtures) and standard organic solvents for ES (i.e. chloroform) were explored in order to compare the fiber characteristics and properties. Morphology, size, crystallinity, thermal and polymer stability of fibers were analyzed. The obtained results showed the suitability of the use of benign solvents for ES, highlighting that for the use of formic acid the degradation of PCL should be taken into consideration.

Efficient enzymatic degradation of poly (ɛ-caprolactone) by an engineered bifunctional lipase-cutinase

Lipases and cutinases belong to esterase family and can be used as biocatalysts for poly (ɛ-caprolactone) (PCL) degradation and recycling. A number of synthetic fusion enzymes with two or more catalytic domains were reported to be superior to the parental enzymes or their mixture for many biotechnological applications but rarely for the polyester biodegradation. To develop a more efficient biocatalyst for poly (ɛ-caprolactone) (PCL) degradation and recycling, a bifunctional lipase-cutinase (Lip-Cut) constructed by end-to-end fusion was successfully overexpressed in Pichia pastoris with 0.9% of methanol induction at pH 6.0 and temperature 27 °C. Lip-Cut displayed more efficient poly (ɛ-caprolactone) degradation capability, and the weight loss of PCL film by Lip-Cut at 6 h was 13.3, 11.8 and 5.7 times higher than that by Lip, Cut and Lip/Cut mixture, respectively. GC-MS analysis of the degraded products of PCL revealed that the mainly degraded product was 6-hydroxyhexanoic acid and small ratio of ɛ-caprolactone. Our results demonstrated that the proper construction of bifunctional lipase-cutinase could enhance the synergistic action of two moieties due to the complementary properties of both enzymes in substrate specificity and hydrolysis pattern. The method provided an effective approach to engineer more efficient biocatalyst for bio-application in degradation and recycling of PCL.

Micro structural and non‐isothermal crystallization and degradation kinetics studies on manganese thioglycolate end capped poly(ε‐caprolactone)

The Manganese thioglycolate (Mn‐TG) end capped poly(ε‐caprolactone) (PCL) was prepared by ring opening polymerization at 160°C under inert atmosphere in the presence of Mn‐TG as an initiator and stannous octoate as a catalyst by bulk polymerization technique. The prepared PCL was investigated using various analytical tools to assess its physico‐chemical properties. The chemical structure of PCL was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopic techniques. The particle size and morphology of the sample was examined by atomic force microscopy and TEM. The melting and crystallization behavior of PCL was analyzed using differential scanning calorimetry. The thermal property of PCL was assessed with the help of thermogravimetric analysis (TGA). The non‐isothermal crystallization kinetics was carried out to understand the nucleation type and crystal growth for the prepared PCL. The energy of activation (Ea) for crystallization process of PCL was determined. The thermal degradation of PCL and its Ea was determined under non‐isothermal condition using important kinetic models. POLYM. ENG. SCI., 59:633–642, 2019. © 2018 Society of Plastics Engineers