Regulating the macroscopic and microscopic self-assembly behavior of hydroxybutyl chitosan based on alkyl...

Hydroxybutyl chitosan (HBC), a derivative of chitosan, exhibits biocompatibility and temperature-sensitive properties, rendering it utilized in tissue engineering, and biomedical science. Currently, HBC is mainly prepared based on heterogeneous and homogeneous reactions. However, the impact of reactions on structure of derivatives and their mechanisms for self-assembly remains to be elucidated. Here, we synthesized HBC with homogeneous and heterogeneous modifications separately, and compared the disparities in their structures and assembly processes. The findings revealed that the structure dissimilarities between heterogeneous (Het-HBC) and homogeneous (Hom-HBC) modification of HBC primarily manifested in the distribution of alkyl. In homogeneous reaction, alkyls are uniformly modified to the hydroxyl and amino of chitosan, facilitating intrachain self-assembly and ultimately resulting in nanoparticle formation. In contrast, the alkyl substituents on the Het-HBC exhibit localized concentration or sparsity, promoting interchain assembly to form the porous hydrogel. This work will provide references for the preparation and application of HBC.