Renal tissue engineering for regenerative medicine using polymers and hydrogels

Chronic Kidney Disease (CKD) is a growing worldwide problem, leading to end-stage renal disease (ESRD). Current treatments for ESRD include haemodialysis and kidney transplantation, but both are deemed inadequate since haemodialysis does not address all other kidney functions, and there is a shortage of suitable donor organs for transplantation. Research in kidney tissue engineering has been initiated to take a regenerative medicine approach as a potential treatment alternative, either to develop effective cell therapy for reconstruction or engineer a functioning bioartificial kidney. Currently, renal tissue engineering encompasses various materials, mainly polymers and hydrogels, which have been chosen to recreate the sophisticated kidney architecture. It is essential to address the chemical and mechanical aspects of the materials to ensure they can support cell development to restore functionality and feasibility. This paper reviews the types of polymers and hydrogels that have been used in kidney tissue engineering applications, both natural and synthetic, focusing on the processing and formulation used in creating bioactive substrates and how these biomaterials affect the cell biology of the kidney cells used

Biomedical applications of bacteria-derived polymers

Plastics have found widespread use in the fields of cosmetic, engineering, and medical sciences due to their wide-ranging mechanical and physical properties, as well as suitability in biomedical applications. However, in the light of the environmental cost of further upscaling current methods of synthesizing many plastics, work has recently focused on the manufacture of these polymers using biological methods (often bacterial fermentation), which brings with them the advantages of both low temperature synthesis and a reduced reliance on potentially toxic and non-eco-friendly compounds. This can be seen as a boon in the biomaterials industry, where there is a need for highly bespoke, biocompatible, processable polymers with unique biological properties, for the regeneration and replacement of a large number of tissue types, following disease. However, barriers still remain to the mass-production of some of these polymers, necessitating new research. This review attempts a critical analysis of the contemporary literature concerning the use of a number of bacteria-derived polymers in the context of biomedical applications, including the biosynthetic pathways and organisms involved, as well as the challenges surrounding their mass production. This review will also consider the unique properties of these bacteria-derived polymers, contributing to bioactivity, including antibacterial properties, oxygen permittivity, and properties pertaining to cell adhesion, proliferation, and differentiation. Finally, the review will select notable examples in literature to indicate future directions, should the aforementioned barriers be addressed, as well as improvements to current bacterial fermentation methods that could help to address these barriers

Porous amphiphilic biogel from facile chemo-biosynthetic route

Grafting of medium-chain-length poly-3-hydroxyalkanoates (mcl- -PHA) with glycerol 1,3-diglycerolate diacrylate (GDD) in acetone was performed using benzoyl peroxide as the initiator. A detailed mechanism scheme provides significant improvement to previous literature. Radical-mediated grafting generated –carbon inter-linking of mcl-PHA and GDD, resulting in a macromolecular structure with gel properties. The thermal properties of the copolymer for different graft yields were investigated as a function of initiator concentration, GDD monomer concentration, incubation period and temperature. The water absorption and porosity of the gel were significantly improved relative to neat mcl-PHA

Medium-chain-length poly-3-hydroxyalkanoates-carbon nanotubes composite as proton exchange membrane in microbial fuel cell

Medium-chain-length poly-3-hydroxyalkanoates (PHA) and carboxyl group-functionalized multiwalled carbon nanotubes (MC) were used to fabricate a composite membrane for application in a double-chambered microbial fuel cell (MFC). MC was composited into PHA at 5%, 10%, and 20% w/w via ultrasound dispersion blending method. PHA-MC composite was compared with Nafion 117 as proton exchange membrane in MFC operated with palm oil mill effluent (POME) wastewater. The composite exhibited prerequisite separator membrane characteristics. The dispersion of MC in the polymer matrix increased its interfacial surface area and water uptake properties. PHA-MC10% membrane in MFC showed maximum power density of 361 mW/m2, which was comparable with Nafion 117 (372 mW/m2). Internal resistance decrease, chemical oxygen demand (COD) removal, coulombic efficiency (CE), and conductivity of the PHA-MC10% were superior to Nafion 117. The environmental-friendly material could provide an alternative towards realizing practical MFC application

Synthesis and characterization of methyl acrylate-copolymerized medium-chain-length poly-3-hydroxyalkanoates

Methyl acrylate (MA) and medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA) underwent “grafting through” copolymerization in an inert atmosphere with benzoyl peroxide as sole radical initiator. The effects of different concentrations of MA on the yield and properties of the graft copolymers (PHA-g-MA) were investigated. Successful grafting of mcl-PHA and poly-methyl acrylate (PMA) was validated from the increase in molecular weight (Mw) of starting mcl-PHA and the presence of methyl acrylate backbone indicated by two additional peaks in proton nuclear magnetic resonance (1H-NMR) spectrum. The hydrophobic graft materials were more resistant to strong alkali condition than neat mcl-PHA in addition to strong acid resistivity. Copolymerization affects the amorphous character of mcl-PHA, as evidenced by a significant reduction in glass transition temperature (Tg). Nonetheless, the degradation temperature (Td) of mcl-PHA was increased about 20 °C higher after copolymerization which indicates excellent thermal stability of grafted mcl-PHA. The graft copolymers also displayed increased dielectric constant (ε′) value except for PHA-g-MA synthesized from the highest concentration of MA (0.12 M) whereby it showed similar glass-to-rubbery transition and dielectric behavior to the neat mcl-PHA. Based on the results, the mechanism of the copolymerization is proposed

Polyhydroxyalkanoates (PHA)-based responsive polymers

Polyhydroxyalkanoates (PHA) envisage a potential biomaterial alternative to replacing synthetic polymers for their biodegradability and biocompatibility. Modification approaches exploit the attributes and adjust the intrinsic hydrophobic properties, such as blending to produce a new polymer mix with novel properties. Functionalization of PHA, especially chemical grafting, perform to introduce additional compounds covalently to PHA. As these methods address PHA potential and enable extensive utilization as a responsive material, reports are readily available in academia as confirmation. There are also substantial responsive PHA-based material applications in the biomedical area and agriculture materials, packaging materials, and nanocomposite materials