Spectroscopic, thermal characterizations and bacteria inhibition of chemically modified chitosan with phthalic anhydride

Chitosan (Ch) is a natural polysaccharide which presents biocompatibility, biodegradability, non-toxicity, mucoadhesion and antimicrobial activity. For instance, the chemical modification using anhydrides have been receiving many attentions for biomedical applications due to the grafting of hydrophobic groups to obtain an amphiphilic molecule. Herein the modified Ch (m-Ch) was obtained by grafting using phthalic anhydride and evaluated their potential to inhibit Gram-positive and Gram-negative bacteria growth. FTIR identified the presence of two new bands in m-Ch referred to C=O and C=N vibrations (1637 cm(-1) and 1402 cm(-1), respectively). Meanwhile, thermogravimetric analysis showed that m-Ch had four stage (3% in first stage, 17% in second one, 15% in the third and 56% in its fourth event) while Ch had two (5% and 63% in first and second stages, respectively) identifying that m-Ch has a different thermal behaviour. Thermal gravimetric coupled mass spectrometry showed that the main fragments of Ch decomposition were: NH3, H2O, H3O+, CO and their derivative were NH3, H2O e CO2, respectively. The m-Ch effectively inhibited 98.2 +/- 0.84% of S. aureus and 24.85 +/- 6.51% of E. coli while Ch inhibited only 58.11 +/- 1.46% of S. aureus. Then the material m-Ch had effectiveness in Gram-positive and negative bacteria inhibition. All produced materials did not present cytotoxicity when in contact with mammalian cells, demonstrating its potential to be used as biomaterial.