Dynamic Aliphatic Polyester Elastomers Crosslinked with Aliphatic Dianhydrides
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PROVIDER: S-EPMC10571103 | biostudies-literature | 2023 May
REPOSITORIES: biostudies-literature
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Project description: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.
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Project description:The study of biomaterials for gene delivery in tissue engineering and regenerative medicine is a growing area, necessitating the investigation of new biomaterials and gene delivery vectors. Poly(1,8-octanediol citrate) (POC) and poly(glycerol-sebacate) (PGS) are biodegradable, biocompatible elastomers that have tunable mechanical properties, surface characteristics, and degradation rate. The objective of this work was to investigate whether POC and PGS would support the immobilization and release of lentivirus to allow sustained and localized transgene expression. Porous biomaterials were prepared using salt as a porogen, and in vitro and in vivo transgene expression from immobilized and released lentiviruses were assessed. Cells seeded onto biomaterials loaded with lentiviruses yielded titer-dependent transgene expression in vitro. Lentivirus activity on both biomaterials was maintained for at least 5 days. When implanted subcutaneously in rats, POC and PGS with immobilized lentivirus exhibited sustained and localized transgene expression for at least 5 weeks. This research demonstrates that lentivirus immobilization on POC and PGS is feasible and potentially useful for a variety of tissue engineering and regenerative medicine applications.
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Project description:Polyethylene terephthalate (PET) is one of the most widely used synthetic plastics in the packaging industry, and consequently has become one of the main components of plastic waste found in the environment. However, several microorganisms have been described to encode enzymes that catalyze the depolymerization of PET. While most known PET hydrolases are thermophilic and require reaction temperatures between 60°C and 70°C for an efficient hydrolysis of PET, a partial hydrolysis of amorphous PET at lower temperatures by the polyester hydrolase IsPETase from the mesophilic bacterium Ideonella sakaiensis has also been reported. We show that polyester hydrolases from the Antarctic bacteria Moraxella sp. strain TA144 (Mors1) and Oleispira antarctica RB-8 (OaCut) were able to hydrolyze the aliphatic polyester polycaprolactone as well as the aromatic polyester PET at a reaction temperature of 25°C. Mors1 caused a weight loss of amorphous PET films and thus constitutes a PET-degrading psychrophilic enzyme. Comparative modeling of Mors1 showed that the amino acid composition of its active site resembled both thermophilic and mesophilic PET hydrolases. Lastly, bioinformatic analysis of Antarctic metagenomic samples demonstrated that members of the Moraxellaceae family carry candidate genes coding for further potential psychrophilic PET hydrolases. IMPORTANCE A myriad of consumer products contains polyethylene terephthalate (PET), a plastic that has accumulated as waste in the environment due to its long-term stability and poor waste management. One promising solution is the enzymatic biodegradation of PET, with most known enzymes only catalyzing this process at high temperatures. Here, we bioinformatically identified and biochemically characterized an enzyme from an Antarctic organism that degrades PET at 25°C with similar efficiency to the few PET-degrading enzymes active at moderate temperatures. Reasoning that Antarctica harbors other PET-degrading enzymes, we analyzed available data from Antarctic metagenomic samples and successfully identified other potential enzymes. Our findings contribute to increasing the repertoire of known PET-degrading enzymes that are currently being considered as biocatalysts for the biological recycling of plastic waste.
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Project description:Oxidative stress plays an important role in the limited biological compatibility of many biomaterials due to inflammation, as well as in various pathologies including atherosclerosis and restenosis as a result of vascular interventions. Engineering antioxidant properties into a material is therefore a potential avenue to improve the biocompatibility of materials, as well as to locally attenuate oxidative stress-related pathologies. Moreover, biodegradable polymers that have antioxidant properties built into their backbone structure have high relative antioxidant content and may provide prolonged, continuous attenuation of oxidative stress while the polymer or its degradation products are present. In this report, we describe the synthesis of poly(1,8-octanediol-co-citrate-co-ascorbate) (POCA), a citric-acid based biodegradable elastomer with native, intrinsic antioxidant properties. The in vitro antioxidant activity of POCA as well as its effects on vascular cells in vitro and in vivo were studied. Antioxidant properties investigated included scavenging of free radicals, iron chelation and the inhibition of lipid peroxidation. POCA reduced reactive oxygen species generation in cells after an oxidative challenge and protected cells from oxidative stress-induced cell death. Importantly, POCA antioxidant properties remained present upon degradation. Vascular cells cultured on POCA showed high viability, and POCA selectively inhibited smooth muscle cell proliferation, while supporting endothelial cell proliferation. Finally, preliminary data on POCA-coated ePTFE grafts showed reduced intimal hyperplasia when compared to standard ePTFE grafts. This biodegradable, intrinsically antioxidant polymer may be useful for tissue engineering application where oxidative stress is a concern.
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Project description:Studies focused on understanding the role of matrix biophysical signals on cells, especially those when cells are encapsulated in hydrogels that are locally remodelled, are often complicated by appropriate methods to measure differences between the bulk and local material properties. From this perspective, stress-relaxing materials that allow long-term culture of embedded cells provide an opportunity to elucidate aspects of this biophysical signalling. In particular, rheological characterization of the stress relaxation properties allows one to link a bulk material measurement to local aspects of cellular functions by quantifying the corresponding cellular forces that must be applied locally. Here, embryonic stem cell-derived motor neurons were encapsulated in a well-characterized covalently adaptable bis-aliphatic hydrazone crosslinked PEG hydrogel, and neurite outgrowth was observed over time. Using fundamental physical relationships describing classical mechanics and viscoelastic materials, we calculated the forces and energies involved in neurite extension, the results of which provide insight to the role of biophysical cues on this process.
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Project description:Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene-alt-phthalate)-b-poly(ε-decalactone)-b-poly(cyclohexene-alt-phthalate) {PE-PDL-PE}. The synthesis is accomplished using a zinc(ii)/magnesium(ii) catalyst, in a one-pot procedure where ε-decalactone ring-opening polymerization yielding dihydroxyl telechelic poly(ε-decalatone) (PDL, soft-block) occurs first and, then, addition of phthalic anhydride/cyclohexene oxide ring-opening copolymerization delivers semi-aromatic polyester (PE, hard-block) end-blocks. The block compositions are straightforward to control, from the initial monomer stoichiometry, and conversions are high (85-98%). Two series of polyesters are prepared: (1) TBPE-1 to TBPE-5 feature an equivalent hard-block volume fraction (f hard = 0.4) and variable molar masses 40-100 kg mol-1; (2) TBPE-5 to TBPE-9 feature equivalent molar masses (∼100 kg mol-1) and variable hard-block volume fractions (0.12 < f hard < 0.4). Polymers are characterized using spectroscopies, size-exclusion chromatography (SEC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). They are amorphous, with two glass transition temperatures (∼-51 °C for PDL; +138 °C for PE), and block phase separation is confirmed using small angle X-ray scattering (SAXS). Tensile mechanical performances reveal thermoplastic elastomers (f hard < 0.4 and N > 1300) with linear stress-strain relationships, high ultimate tensile strengths (σ b = 1-5 MPa), very high elongations at break (ε b = 1000-1900%) and excellent elastic recoveries (98%). There is a wide operating temperature range (-51 to +138 °C), an operable processing temperature range (+100 to +200 °C) and excellent thermal stability (T d,5% ∼ 300 °C). The polymers are stable in aqueous environments, at room temperature, but are hydrolyzed upon gentle heating (60 °C) and treatment with an organic acid (para-toluene sulfonic acid) or a common lipase (Novozyme® 51032). The new block polyesters show significant potential as sustainable thermoplastic elastomers with better properties than well-known styrenic block copolymers or polylactide-derived elastomers. The straightforward synthesis allows for other commercially available and/or bio-derived lactones, epoxides and anhydrides to be developed in the future.
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