Synthesis of a new natural chitosan based hydrogel and its usage in drug delivery applications

Hydrogels which have ability to absorp high amount of water and physilogical fluids are physically and chemically crosslinked structures. They have three dimensional network system formed from hydrophilic polymer chains. The network structure can occur from homopolymers or copolymers. Hydrogels do not dissolve in water due to their crosslinks but tend to swell owing to hydrophilic groups. The drug delivery which is one of the important application areas of hydrogels is related to swelling process and it depends on swelling ratios and crosslink density of hydrogels. Hydrogel carrier systems having high swelling degree perform drug delivery more and faster than the other systems. There are a number of studies about drug delivery applications of hydrogels. However, everyday new searches are added to them to improve results and to eliminate present side effects. The most studied hydrogels in the subject of drug delivery applications are natural chitosan based hydrogels. Nevertheless, most of present studies about chitosan hydrogels consist of physical crosslinks, which are not stable and cause to lessen mechanical strength of hydrogels or crosslinker gluteraldehyde, which has toxic effect. In this study, covalently crosslinked chitosan hydrogels with genipin, which has natural structure and can be used for biological purpose, were prepared. Thus, stable and strong hydrogels were obtained by natural genipin compound unlike mostly used gluteraldehyde thus eliminating undesired toxic effect. On the other hand it was aimed to change the swelling degrees and also drug delivery rates with incorporation of spirulina, which is a kind of microalg, compared to present drug delivery system. With this aim, the natural genipin crosslinked chitosan hydrogels having varied spirulina content were prepared. The morphological structure and mechanical properties of the hydrogels were characterized with SEM analysis and compression tests, respectively. In addition, the swelling degrees and 5-fluorouracil, which is present in the cancer treatment medicines, delivery properties were investigated in pH:2 and pH:7,4 media.