An Efficient High-Pressure Solubilization Method for Chitosan Nanoparticle Generation

Abstract The wide variety of highly promising applications of chitosan are currently limited by its low solubility, as well as by its well-known strong tendency to form irregular aggregates. An easy and eco-friendly process based on high hydrostatic pressure yielding soluble chitosan to much higher concentrations (12% w/v) is described. Moreover, molecular characterization of chitosan has been often impaired by its aggregation tendency, making some determinations unreliable. Dynamic light scattering measurements carried out with high-pressure solubilized chitosan suggest that it contains individual free chains with a hydrodynamic radius of 3.45 ± 0.32 nm and very low polydispersity and only a small percentage of aggregates. Meanwhile, chitosan solubilized by classical procedures would consist mainly of aggregated polymer, with a much higher size and polydispersity and a low reproducibility behavior. The lack of other structural or chemical alterations has been checked by a FT-IR-based heatmap analysis. Disaggregated chitosan would be more reactive in all senses: for chemical and enzymatic processes, for its wide property range, such as antimicrobial, antioxidant, health, and plant defense promoting activities. Chitosan, directly derived from chitin, the second most abundant byproduct in nature, is the only cationic biopolymer, and it is considered a very interesting source for a Green Circular Economy implantation.