A rational approach towards the design of chitosan-based nanoparticles obtained by ionotropic gelation.

Chitosan is a linear aminopolysaccharide that has been widely used for the formation of chitosan-based nanoparticles by ionic gelation with sodium tripolyphosphate (TPP). Often, the experimental design used to obtain these systems does not take into consideration important variables, such as the degree of acetylation (DA) and the molecular weight (Mw) of chitosan. In this work, we studied the formation of chitosan-TPP nanoparticles with chitosan samples of varying DA and Mw (DA0 ∼ 0-47% and Mw ∼ 2.5-282 kDa). We addressed the influence the degree of space occupancy and the degree of crosslinking on the physical properties of chitosan-TPP nanoparticles. Nanoparticles that comprised chitosan of DA ∼ 0-21.7% behaved differently than those made of chitosan of DA ∼ 34.7-47%. We attributed these differences to the polymer conformation and chain flexibility of the distinct chitosans in solution. Moreover, chitosan of high Mw were found to have a stronger preference for incorporating into the formed nanoparticles than do low-Mw ones, as determined by SEC-HPLC. These results open new perspectives to understand the formation of chitosan nanoparticles by the ionic gelation technique.