Microbial degradation, cytotoxicity and antibacterial activity of polyurethanes based on modified castor oil and polycaprolactone.

The objective of this study was to assess the effects of type of polyol and concentration of polycaprolactone (PCL) in polyurethanes (PUs) on microbial degradability, cytotoxicity, biological properties and antibacterial activity to establish whether these materials may have biomedical applications. Chemically modified and unmodified castor oil, PCL and isophorone diisocyanate in a 1:1 ratio of NCO/OH were used. PUs were characterized by stress/strain fracture tests and hardness (ASTM D 676-59). Hydrophilic character was determined by contact angle trials and morphology was evaluated by scanning electron microscopy. Degradability with Escherichia coli and Pseudomonas aeruginosa was evaluated by measuring variations in the weight of the polymers. Cytotoxicity was evaluated using the ISO 10993-5 (MTT) method with mouse embryonic fibroblasts L-929 (ATCC® CCL-1) in direct contact with the PUs and with NIH/3T3 cells (ATCC® CRL-1658) in indirect contact with the PUs. Antimicrobial activity against E. coli and P. aeruginosa was determined. PUs derived from castor oil modified (P0 and P1) have higher mechanical properties than PUs obtained from castor oil unmodified (CO). The viability of L-929 mouse fibroblasts in contact with polymers was greater than 70%. An assessment of NIH/3T3 cells in indirect contact with PUs revealed no-toxic degradation products. Finally, the antibacterial effect of the PUs decreased by 77% for E. coli and 56% for P. aeruginosa after 24 h. These results indicate that PUs synthesized with PCL have biocidal activity against Gram-negative bacteria and do not induce cytotoxic responses, indicating the potential use of these materials in the biomedical field.