Recent developments in short- and medium-chain- length Polyhydroxyalkanoates: Production, properties, and applications.

Developing renewable resource-based plastics with complete biodegradability and a minimal carbon footprint can open new opportunities to effectively manage the end-of-life plastics waste and achieve a low carbon society. Polyhydroxyalkanoates (PHAs) are biobased and biodegradable thermoplastic polyesters that accumulate in microorganisms (e.g., bacterial, microalgal, and fungal species) as insoluble and inert intracellular inclusion. The PHAs recovery from microorganisms, which typically involves cell lysis, extraction, and purification, provides high molecular weight and purified polyesters that can be compounded and processed using conventional plastics converting equipment. The physio-chemical, thermal, and mechanical properties of the PHAs are comparable to traditional synthetic polymers such as polypropylene and polyethylene. As a result, it has attracted substantial applications interest in packaging, personal care, coatings, agricultural and biomedical uses. However, PHAs have certain performance limitations (e.g. slow crystallization), and substantially more expensive than many other polymers. As such, more research and development is required to enable them for extensive use. This review provides a critical review of the recent progress achieved in PHAs production using different microorganisms, downstream processing, material properties, processing avenues, recycling, aerobic and anaerobic biodegradation, and applications.

Crosslinked porous three-dimensional cellulose nanofibers-gelatine biocomposite scaffolds for tissue regeneration.

Gelatine is a biocompatible and natural polymer with chemical properties similar to the extracellular matrix. However, it has poor mechanical properties and sensitive to enzymatic biodegradation that limits its application in 3D scaffold fabrication. Cellulose nanofibrous (CNF) offers biocompatibility, high surface area and excellent mechanical properties with slow in-vivo degradation. To fine tune their properties, CNF, and gelatine (CNF-GEL) were blended to form biocomposite aerogels. Epichlorohydrin (EPH) was incorporated into CNF-GEL as a chemical crosslinker to investigate its effect on the physiochemical, mechanical, and biological properties of the biocomposite aerogels both in-vitro and in-vivo. Regardless of the composition of the prepared aerogels, they possessed porosity of >90% with the pore size of 7-135 µm, which was confirmed in the morphological analysis. The presence of EPH improved the chemical interaction between CNF and gelatine, hence enhanced the compressive strength compared to uncrosslinked samples. The formulation of crosslinked CNF-GEL 90:10 offered the highest compressive strength of 61.35 kPa. The in-vitro and in-vivo studies showed adequate cytocompatibility, cell viability and cell attachment in the optimal crosslinked formulation with tuned enzymatic degradation. Antimicrobial property was also achieved in the optimal scaffold by incorporating curcumin as an antimicrobial agent.