Characterization of single network and interpenetrating network hydrogels of natural and synthetic polymers

Progress in the field of tissue engineering is largely dependent upon the construction of materials that can maintain the mechanical characteristics during the tissue regeneration. The work presented in this thesis provides a foundation for the further development of long-term degrading hydrogels for future tissue engineering applications. Natural polymers; gellan gum (GG), k-carrageenan (kC) and synthetic polymers; polyacrylamide (PAAm) and epoxy-amines (EA) are either being proposed or used as potential candidates for tissue engineering. This thesis aimed to study the long-term degradation behaviour of single network hydrogels of GG (low-acyl and high-acyl) and ionic-covalent entanglement (ICE) hydrogels of GG/PAAm and kC/EA. All the hydrogels were synthesized using simultaneous preparation techniques and characterized while degrading in PBS at 37oC. GG gels show mass loss up to 28 days and remain stabilized during the rest of the study period (168 days), whereas kC gels disintegrate within 4 hours. The mass losses of GG/PAAm and kC/EA stabilize after 7 and 21 days, respectively. The mass loss profiles of GG and GG/PAAm are affected by the ion-exchange with surrounding PBS. The mechanical and load tolerant properties of the ICE hydrogels are proportional to their respective swelling and mass loss profiles. The mechanical and load tolerant properties of GG and GG/PAAm remain less affected, whereas these properties of kC/EA significantly decrease with increasing swelling. In enzymatic conditions, GG/PAAm show higher mass loss when immersed in trypsin. The mass loss in enzymes were attributed to the hydrolysis of glycosidic and amide bonds in respective GG and PAAm networks (of GG/PAAm network). The leachates of GG/PAAm and kC/EA collected for 28 days, are noncytotoxic for L929 fibroblasts and PC12 growth. Inconclusion, GG/PAAm and kC/EA hydrogels may be suitable for tissue engineering applications demand slow degradation.