Cytotoxicity and nontoxicity performance testing

P4HB and P3HB-4HB have been evaluated in preclinical tests reconunended by the FDA for medical devices. These tests include cytotoxicity, sensitization, irritation and intracutaneous reactivity, hemocompatibility, and implantation. Thus for example, P4HB films and sutures were subjected to a complete series of biocompatibility test protocols that were performed in accordance with the FDA s GLP regulations as set forth in 21 CFR, part 58, as well as ISO 10993-1. The test results confirmed that P4HB is nontoxic and biocompatible (Martin DP, personal communication). 

To investigate the safety of thiolated chitosans, several studies have been performed measuring its potential cytotoxicity on various cell lines. The toxicity profiles of chitosan-TBA, for example, were assessed using the red blood cell lysis test. The results showed that thiolated chitosan had a lower membrane damaging effect than the corresponding unmodified control. The safety of thiolated chitosan was further confirmed by metabolic activity (cleavage of dimethyl-thiazolyl-diphenyltetrazo-lium bromide) (MTT) and DNA synthesis (incorporation of 5-bromo-2 -deoxyur-idine [BrdU]) assay on L-929 mouse fibroblast cells. It was found that the toxicity of chitosan-TBA was concentration-dependent [63]. Another thiolated chitosan investigated for cytotoxicity was chitosan-MBA, which was found to be nontoxic because Caco-2 cell viability was around 100% after 4 and 24 h of incubation [25]. 

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