Designing supermacroporous cryogels based on polyacrylonitrile and a polyacrylamide-chitosan semi-interpenetrating network

Cryogels of polyacrylonitrile (PAN) and a semi-interpenetrating network of polyacrylamide-chitosan (PAAC) synthesized at sub-zero temperature have large interconnected pores in the range of 10-100 μm as analyzed by scanning electron microscopy (SEM) and mercury porosimetry with porosity more than 90%. They had good transport properties with a diffusion constant of 3.5 × 10^-7 cm²/s for bovine serum albumin and hydraulic permeability of 4 × 10^-12 m⁴/N s. The materials have a high surface area of 9-18 m²/g which is significantly larger than the surface area available in commercially available hollow fiber bioreactors. The cryogels are thermally stable and have good mechanical strength with a Young's modulus of 137-1967 kPa for different concentration of PAN gels and 13 kPa for PAAC cryogel. The cryogels are biocompatible as confirmed by fetal bovine serum protein adsorption and direct contact assay. The material demonstrated adherence and proliferation of cells on the polymer surface and a sustained growth of cells over the scaffolds was seen for a period of 14 days. The three-dimensional (3-D) cryogel network with these physical characteristics renders them as potential material for cell scaffold in a perfusion bioreactor.