Injectability of Thermosensitive, Low-Concentrated Chitosan Colloids as Flow Phenomenon through the Capillary under High Shear Rate Conditions.

Anna Rył,Piotr Owczarz

doi:10.3390/polym12102260

Abstract

Low-concentrated colloidal chitosan systems undergoing a thermally induced sol–gel phase transition are willingly studied due to their potential use as minimally invasive injectable scaffolds. Nevertheless, instrumental injectability tests to determine their clinical utility are rarely performed. The aim of this work was to analyze the flow phenomenon of thermosensitive chitosan systems with the addition of disodium β-glycerophosphate through hypodermic needles. Injectability tests were performed using a texture analyzer and hypodermic needles in the sizes 14G–25G. The rheological properties were determined by the flow curve, three-interval thixotropy test (3ITT), and Cox–Merz rule. It was found that reducing the needle diameter and increasing its length and the crosshead speed increased the injection forces. It was claimed that under the considered flow conditions, there was no need to take into account the viscoelastic properties of the medium, and the model used to predict the injection force, based solely on the shear-thinning nature of the experimental material, showed very good agreement with the experimental data in the shear rate range of 200–55,000 s−1. It was observed that the increase in the shear rate value led to macroscopic structural changes of the chitosan sol caused by the disentangling and ordering of the polysaccharide chains along the shear field.

Highlights

In recent years, due to the growing number of traffic accidents and surgical interventions, innovative methods of treatment and regeneration of damaged tissues are sought
The obtained parameters values of the power law proved a very strong shear-thinning behavior of chitosan sol under the flow conditions observed in injection needles
It should be noted that the applied equation for predicting the injection force value showed very good agreement with the experimental data on the widest range of injection needles considered so far, where the flow conditions determined by the shear rate value varied in the range of 200 s−1 < y < 55,000 s−1

Summary

Introduction

Due to the growing number of traffic accidents and surgical interventions, innovative methods of treatment and regeneration of damaged tissues are sought. One of the desired feature of the injectable hydrogels is their shear-thinning behavior [7,8], resulting in a reduction in viscosity as they flow through the needle. Thanks to this, they can be precisely designed in a laboratory and successfully injected into the body. In addition to purely pharmaceutical aspects such as the use of anesthetics, the reduction of injection pain is possible by reducing the diameter of the needle. In extreme cases, choosing a needle that is too small

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