Abstract
Injectable polymer/cell dispersions have emerged as a superior, non-surgical alternative for tissue regeneration. We have previously explored novel types of pH and redox-responsive poly(methyl methacrylate-co-methacrylic acid)- (PMMA-MAA) and poly(ethyl acrylate-co-methacrylic acid) (PEA-MAA)-based hollow particle gels. The gels had micrometer-scale interconnected porosity, high elasticity and ductility values and are potentially suitable for future use in minimally-invasive tissue repair. Herein we extend considerably our earlier studies with the aim of identifying a system which meets all necessary requirements for soft tissue repair – i.e., high porosity, biocompatibility, biodegradability and adequate mechanical strength. To investigate the effect of tuning hydrophobicity of the copolymer, the glass transition temperature and the pKa of the particles upon the gel morphology, mechanical properties and performance, we studied the structurally related poly(n-butyl acrylate-co-methacrylic acid) (PBA-MAA), poly(methyl acrylate-co-methacrylic acid) (PMA-MAA) and poly(methyl methacrylate-co-acrylic acid) (PMMA-AA) copolymers for gel formation. These systems have been chosen to allow a wide range of structural variation for the constituent pH-responsive copolymers. We have established that MMA is the optimal hydrophobic monomer, whereas the use of various COOH-containing monomers, e.g. MAA and AA, will always induce a pH-triggered physical gelation.