Poly(N-hydroxyethyl acrylamide) / Chitosan Based Hydrogels

Poly(N-hydroxyethyl acrylamide) (polyHEAA) was grafted onto chitosan in aqueous acidic medium using potassium per sulphate initiator to obtain polymer surfaces with blood compatibility for potential biomedical applications such as blood contacting devices as artificial veins or devices to remove excess ions from the blood. The grafting parameters monomer concentration, crosslinker concentration, initiator concentration, processing time and temperature were changed to find out the effect of each parameter on the grafting yield (%G) and choose the best preparation parameters for the aimed purpose. Grafting yield values up to 600% were achieved. Thermally cross-linked products were obtained upon drying at 60°C overnight. Chemically cross-linked films were prepared using methylene bis acrylamide (MBA) and glutaraldehyde (GA) cross-linkers. The products were characterized by FTIR, XRD and SEM analyses. Blood compatibility and protein adsorption characteristics of the MBA crosslinked and poly (N-hydroxy ethyl acrylamide) grafted chitosans namely (chitosan-graft-polyHEAA;MBA) were investigated. Protein adsorption onto the film surfaces were about 10% human serum albumin (HSA) removal from aqueous solution, after 3 h contact, in vitro. Blood compatibility was evaluated with respect to activated prothrombin time (PT), activated partial thromboplastin time (APTT), and platelet adhesion. PT and APTT values remained within normal ranges after blood-polymer contact for 90 minutes, with chitosan-graft-polyHEAA films, in vitro. Examining chitosan-graft-MBA or chitosan-graft-(polyHEAA;MBA), and blank chitosan films caused higher PT and APTT values under similar experimental conditions with chitosan-graft-polyHEAA films, exhibiting blood anticoagulant activity. SEM images taken before and after contact with blood sample did not reveal iv any significant blood component adhesion on the chitosan-graft-(polyHEAA;MBA) film surface contrary to the observation made on the chitosan film. However, the blood components on the film surfaces were not identified. Glutaraldehyde crosslinked films (chitosan-graft-(polyHEAA;GA)) were prepared and tested as adsorbents for Fe3+ ion in solution. It was observed that crosslinking, swelling and polyHEAA grafting values acted together in determining the adsorption capacity. The highest adsorption capacity was found as 44.8 mg Fe /g adsorbent at pH=1.2, at room temperature from 500 ppm FeCl3 solution within 24 h contact by a sample with 586% grafting yield value. Keywords: biomaterial, chitosan, glutaraldehyde, grafting, hemocompatibility, hydrogel, methylene bis acrylamide, polyacrylamide.