Producing chitin scaffolds with controlled pore size and interconnectivity for tissue engineering

Tissue engineering utilizes cells and synthetic matrices to create new tissues. Living cells are anchorage dependent and will die if they are not provided with an adhesion substrate. Man-made scaffolds are designed to provide a structural framework for the selected cells and to facilitate the formation of new tissues. Matrix structure of the scaffold should be connective together with high porosity to provide diffusion of nutrients and to permit vascular ingrowth into the implanted structure. Biodegradable polymers are preferred materials for synthetic matrices because they disintegrate or bioresorb once they have accomplished their functions, leading to the formation of a completely natural tissue without leaving permanent synthetic element(s) in the human body. Chitin, occurring mainly in crustacea, mollusks and insects where it is an important constituent of the exoskeleton, is one of the most abundant organic materials [1]. It is biodegradable because the β-1, 4-glycosidic linkage is susceptible to degradation by lysozyme [2]. Therefore, chitin is a promising biodegradable polymer having the potential of being fabricated as porous scaffolds for tissue engineering. In this investigation, the co-extraction process was adopted for producing chitin scaffolds, which combined co-leaching of a fugitive phase and polymer solvent with simultaneous polymer precipitation [3]. The raw material of chitin flakes was obtained from Polysciences Inc., USA. N ,N -dimethy-lacetamide (DMAc)/5%LiCl solution was used as a solvent for chitin. Chitin flakes were completely dissolved in DMAc/5%LiCl solvent to produce 0.5%, 1% and 1.5% (w/w) solutions of chitin after magnetic stirring for 3 days. A particulate porosifier, i.e., sugar, was added into the resultant chitin solutions. The chitin/solvent/porosifier mixture was poured into a mold and subjected to the simultaneous extraction of the porosifier and chitin solvent in distilled water, which is a non-solvent for chitin but a solvent for the porosifier and is also miscible with the chitin solvent. The porous chitin blocks were immersed in distilled water for days to remove the residual chitin solvent and LiCl. The water-swollen porous chitin blocks were frozen to −40 ◦C and a freeze-drying procedure was applied using a freeze-drier (VirTis AdVantage Model EL, VirTis Inc., USA) to produce dry porous chitin. The