Add time:08/08/2019         Source:sciencedirect.com

It is well known that chitosan degradation by nitrous acid leads to oligochitosan (oligoCHIt–ahm) bearing reactive 2,5-anhydromannose (3,4-dihydroxy-5-hydroxymethyl-tetrahydrofuran-2-aldehyde) units at the new reducing ends of macromolecules. Standard protocol requires reduction of oligoCHIt–ahm with NaBH4 to corresponding oligoCHIt–hml bearing unreactive hydroxymethyl group instead of reactive aldehyde group. For the first time, HP SEC as well as UV and CD spectroscopy methods have revealed that the reduction leads to an indefinite side modification and the formation of a branched oligoCHIt-hml with increased molecular weight. Here, it is shown that the branching and modification can be prevented by means of the simple and reproducible reaction of oligoCHIt–ahm with hydroxylamine that allows preparation of a stable linear oligochitosan oxime, oligoCHIt–oxm. Cytotoxicity tests show that oligoCHIt–ahm, oligoCHIt–hml and oligoCHIt–oxm are non-toxic at concentration below 2.5 mg/ml, and the cytotoxicity is concentration dependent and decreases in the order oligoCHIt–ahm > oligoCHIt–hml > oligoCHIt–oxm at higher concentrations both before and after long shelf-storage. The elaborated approach and cytotoxicity data give an opportunity to use the non-branched oligoCHIt–oxm for biomedical applications.

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