Thermoinduced aggegation of chitosan systems in perikinetic and orthokinetic regimes.

Thermoresponsive colloidal chitosan systems forming the polymer structure in situ are an example of promising solutions in tissue engineering as an injectable scaffolds or drug carriers. Their application method, and thus shearing, may affect the aggregation process in accordance with the colloidal engineering approach. The aim of the study is to compare the kinetics of chitosan aggregation in the perikinetic regime (limited by Brownian motions) with the orthokinetic process carried out under the influence of an external shear field. The research was carried out using static multiple light scattering (S-MLS) and rheometric measurement techniques coupled with small-angle light scattering (Rheo-SALS). It has been found that the introduction of an external shear field (orthokinetic regime) accelerates the aggregation of chitosan systems. Simultaneously, the rotational measurements can even lead to spontaneous gelation, most likely caused by changes in the conformation of chitosan molecules, their deformation and ordering along the shear field.