Tailoring the Nucleation and Crystallization Rate of Polyhydroxybutyrate by Copolymerization

Synergistic enhancement of toughness and biocompatibility in poly(l-lactide) via copolymerization with poly(ε-caprolactone) and multi-arm branched strategy for aortic stent applications

Poly(lactide) has demonstrated significant potential in small-diameter vascular stents, particularly in coronary artery applications. However, its limited toughness and suboptimal biocompatibility hinder its use in high-stress regions such as the aorta. To overcome these limitations, we have designed and synthesized multi-arm poly(l-lactide-b-ε-caprolactone) (PLCL) copolymers with enhanced toughness and biocompatibility through copolymerization with polycaprolactone and multi-arm branching strategies. This study comprehensively evaluates the chemical structure, crystallization properties, mechanical properties, adhesion properties, biocompatibility and in vivo degradation profiles of multi-armed PLCLs. Results show that PLCLs exhibit substantial tensile strength and toughness, with tensile strength ranging from 1.43 MPa (2a-PLCL) to 42.45 MPa (6a-PLCL), and elongation at break from 3.07 % (2a-PLCL) to 31.49 % (6a-PLCL). Both of them were positively correlated with the number of arms. In vitro studies revealed enhanced cell adhesion and proliferation for multi-armed PLCLs. Animal model evaluations confirmed excellent histocompatibility and as the number of polymer arms increased, inflammation decreased, and the degradation rate accelerated. Notably, the 6a-PLCL exhibited the best overall performance, making it more favorable for promoting aortic remodeling. In summary, this study suggests that multi-armed PLCLs are promising candidates for cardiovascular tissue engineering and absorbable medical devices due to their enhanced mechanical properties and biocompatibility.

Electrospinning of Poly-3-Hydroxybutyrate Fibers Loaded with Chlorophyll for Antibacterial Purposes

This work is devoted to the creation of biocompatible fibrous materials with a high antimicrobial effect based on poly-3-hydroxybutyrate (PHB) and chlorophyll (Chl). The data obtained show the possibility of obtaining fibrous materials from PHB and Chl by electrospinning methods. The obtained electrospun matrices were investigated by the SEM, DSC and FTIR methods. Various key properties of the matrices were evaluated, including hydrophilicity and mechanical strength, as well as photodynamic and light-dependent antimicrobial effects against the conditionally pathogenic microorganism Staphylococcus aureus. The results demonstrate a significant improvement in electrospinning properties for a concentration of 0.5% Chl and a reduction in fiber formation defects, as well as an increase in the strength of nonwovens. It was found that the antimicrobial potential of Chl-PHB (with concentrations of Chl of 1.25 and 1.5%) is higher than that of Chl in free form. It was also determined that irradiation increases the inhibitory effect of Chl, both in free form and in the form of a complex with a polymer.

Innovative biomaterials for food packaging: Unlocking the potential of polyhydroxyalkanoate (PHA) biopolymers

Polyhydroxyalkanoate (PHA) biopolyesters show a good balance between sustainability and performance, making them a competitive alternative to conventional plastics for ecofriendly food packaging. With an emphasis on developments over the last decade (2014-2024), this review examines the revolutionary potential of PHAs as a sustainable food packaging material option. It also delves into the current state of commercial development, competitiveness, and the carbon footprint associated with PHA-based products. First, a critical examination of the challenges experienced by PHAs in terms of food packaging requirements is undertaken, followed by an assessment of contemporary strategies addressing permeability, mechanical properties, and processing considerations. The various PHA packaging end-of-life options, including a comprehensive overview of the environmental impact and potential solutions will also be discussed. Finally, conclusions and future perspectives are elucidated with a view of prospecting PHAs as future green materials, with a blend of performance and sustainability of food packaging solutions.

Engineering of the Long-Main-Chain Monomer-Incorporating Polyhydroxyalkanoate Synthase PhaCAR for the Biosynthesis of Poly[(R)-3-hydroxybutyrate-co-6-hydroxyhexanoate]

Polyhydroxyalkanoate (PHA) synthases (PhaCs) are useful and versatile tools for the production of aliphatic polyesters. Here, the chimeric PHA synthase PhaCAR was engineered to increase its capacity to incorporate unusual 6-hydroxyhexanoate (6HHx) units. Mutations at positions 149 and 314 in PhaCAR were previously found to increase the incorporation of an analogous natural monomer, 3-hydroxyhexanoate (3HHx). We attempted to repurpose the mutations to produce 6HHx-containing polymers. Site-directed saturation mutants at these positions were applied for P(3HB-co-6HHx) synthesis in Escherichia coli. As a result, the N149D and F314Y mutants effectively increased the 6HHx fraction. Moreover, the pairwise NDFY mutation further increased the 6HHx fraction, which reached 22 mol %. This increase was presumably caused by altered enzyme activity rather than altered expression levels, as assessed based on immunoblot analysis. The glass transition temperature and crystallinity of P(3HB-co-6HHx) decreased as the 6HHx fraction increased.

Synthesis and physical properties of polyhydroxyalkanoate (PHA)-based block copolymers: A review

Polyhydroxyalkanoates (PHAs) are a group of natural polyesters that are synthesised by microorganisms. In general, their thermoplasticity and (in some forms) their elasticity makes them attractive alternatives to petrochemical-derived polymers. However, the high crystallinity of some PHAs - such as poly(3-hydroxybutyrate) (P3HB) - results in brittleness and a narrow processing window for applications such as packaging. The production of copolymeric PHA materials is one approach to improving the mechanical and thermal properties of PHAs. Another solution is the manufacture of PHA-based block copolymers. The incorporation of different polymer and copolymer blocks coupled to PHA, and the resulting tailorable microstructure of these block copolymers, can result in a step-change improvement in PHA-based material properties. A range of production strategies for PHA-based block copolymers has been reported in the literature, including biological production and chemical synthesis. Biological production is typically less controllable, with products of a broad molecular weight and compositional distribution, unless finely controlled using genetically modified organisms. By contrast, chemical synthesis delivers relatively controllable block structures and narrowly defined compositions. This paper reviews current knowledge in the areas of the production and properties of PHA-based block copolymers, and highlights knowledge gaps and future potential areas of research.