Chitosan Mixtures from Marine Sources: A Comparative Study of Biological Responses and Practical Applications

Chitosan, a biopolymer with molecular variability, continues to demonstrate promising potential for biomedical and biotechnological applications. In this study, mixtures of β-oligochitosan, with a low molar mass (MM) of 1.5 kDa (CH1), α-oligochitosan, MM = 26.39 kDa (CH2), and α-chitosan, MM = 804.33 kDa (CH3) were analyzed. The tested solutions, chitosan alone and mixtures (CH1:CH2 and CH1:CH3), prepared in different mass ratios (1:1, 2:1, 3:1), were characterized in terms of MM and degree of deacetylation (DDA). The antimicrobial activity on S. aureus, E. coli, and C. parapsilosis was evaluated. The fractional inhibitory concentration index (FICI) was also calculated for mixtures. Using the Brine Shrimp Lethality Assay (BSLA), the in vivo interactions, which involve the internalization of chitosan in the cells, were assessed. The results showed that α-β chitosan mixtures exhibited an in vitro antimicrobial antagonistic effect (FICI > 1) for all samples. In contrast, significantly improved larval survival (%), development, and motility (p < 0.0001), with a close correlation between cellular inclusions and naupliar stages (R = 0.94), were detected in vivo testing. These data support the strategic use of chitosan mixtures with variable characteristics in biotechnological applications, with potential for optimizing intake, biological activity, and controlling cytotoxicity.