Influence of Injection Application on the Sol-Gel Phase Transition Conditions of Polysaccharide-Based Hydrogels.

Anna Rył,Piotr Owczarz

doi:10.3390/ijms222413208

Anna Rył, Piotr Owczarz

Open Access

https://doi.org/10.3390/ijms222413208

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Abstract

Polysaccharide matrices formed via thermoinduced sol–gel phase transition are promising systems used as drug carriers and minimally invasiveness scaffolds in tissue engineering. The strong shear field generated during injection may lead to changes in the conformation of polymer molecules and, consequently, affect the gelation conditions that have not been studied so far. Chitosan (CS) and hydroxypropyl cellulose (HPC) sols were injected through injection needles (14 G–25 G) or sheared directly in the rheometer measuring system. Then the sol–gel phase transition conditions were determined at 37 °C using rheometric, turbidimetric, and rheo-optical techniques. It was found that the use of low, respecting injection, shear rates accelerate the gelation, its increase extends the gelation time; applying the highest shear rates may significantly slow down (HPC) or accelerate gelation (CS) depending on thixotropic properties. From a practical point of view, the conducted research indicates that the use of thin needles without preliminary tests may lead to an extension of the gelation time and consequently the spilling of the polymeric carrier before gelation. Finally, an interpretation of the influence of an intensive shear field on the conformation of the molecules on a molecular scale was proposed.

Highlights

In the biomedical engineering field, a growing interest in innovative methods of treatment and regeneration has been observed [1]
The most frequently discussed materials in the literature that fulfill this requirement are systems made of polysaccharides like chitosan [16,17,18], cellulose derivatives such as hydroxypropyl cellulose (HPC) [19,20,21], HPMC [22,23], and synthetic polymers, e.g., PNIPAAM [24] and PLGA [25]
It has been shown that the flow of the polymer sol under the conditions of high shear rates observed during injection causes a significant increase in shear stress, which affects the sol–gel phase transition conditions

Summary

Introduction

In the biomedical engineering field, a growing interest in innovative methods of treatment and regeneration has been observed [1]. Injectable hydrogels [2,3,4] obtained from natural and synthetic polymers may provide a very promising solution Interest in these systems results from their lower invasiveness compared to implantation scaffolds, reduced risk of infection and scarring, as well as better filling of difficult, irregular defects [5]. Depending on the form of the formulation before and after administration, as well as the mechanism of creating an unlimited polymer structure, three groups of materials are distinguished: shear thinning injectable gels, self-assembling suspensions of solid particles, and in situ gelling liquids [8] The latter creates a three-dimensional polymer matrix directly in the body as a result of the sol–gel phase transition induced by one or a combination of different stimuli [9,10], the most common temperature changes [11,12,13]. Such systems are often subject to further modifications leading to the improvement of mechanical properties [18,26,27]

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