Alginate Gel Reinforcement with Chitin Nanowhiskers Modulates Rheological Properties and Drug Release Profile.

Valentina A Petrova,Dmitry P Romanov,Daria N Poshina,Yury A Skorik,Vladimir Y Elokhovskiy,Sergei V Raik

doi:10.3390/biom9070291

Abstract

Hydrogels are promising materials for various applications, including drug delivery, tissue engineering, and wastewater treatment. In this work, we designed an alginate (ALG) hydrogel containing partially deacetylated chitin nanowhiskers (CNW) as a filler. Gelation in the system occurred by both the protonation of alginic acid and the formation of a polyelectrolyte complex with deacetylated CNW surface chains. Morphological changes in the gel manifested as a honeycomb structure in the freeze-dried gel, unlike the layered structure of an ALG gel. Disturbance of the structural orientation of the gels by the introduction of CNW was also expressed as a decrease in the intensity of X-ray diffraction reflexes. All studied systems were non-Newtonian liquids that violated the Cox-Merz rule. An increase in the content of CNW in the ALG-CNW hydrogel resulted in increases in the yield stress, maximum Newtonian viscosity, and relaxation time. Inclusion of CNW prolonged the release of tetracycline due to changes in diffusion. The first phases (0–5 h) of the release profiles were well described by the Higuchi model. ALG-CNW hydrogels may be of interest as soft gels for controlled topical or intestinal drug delivery.

Highlights

IntroductionHydrogels based on natural polysaccharides are promising materials for biomedical applications due to their biocompatibility, biodegradability, and wide range of physical properties [1].Polysaccharides can be used in the form of films, sponges, and hydrogels for purposes that include wound-healing and burn coatings [2,3], tissue engineering [4,5], drug and growth factor delivery [6], and suturing [7].Hydrogels and composite materials based on the natural polysaccharide alginic acid (ALG) are well known and widely used in bone tissue engineering [8], drug delivery [9], and cell encapsulation [10,11].ALG molecules are linear and contain β-d-mannuronic and α-l-guluronic acid residues that are present in their pyranose forms and are linked by 1–4 bonds
The gel-forming centers in the ALG-chitin nanowhiskers (CNW) hydrogels were the positively charged CNW, which are capable of forming polyelectrolyte complexes (PEC) with negatively charged ALG molecules
Hydrogels were fabricated from ALG and partially deacetylated CNW

Summary

Introduction

Hydrogels based on natural polysaccharides are promising materials for biomedical applications due to their biocompatibility, biodegradability, and wide range of physical properties [1].Polysaccharides can be used in the form of films, sponges, and hydrogels for purposes that include wound-healing and burn coatings [2,3], tissue engineering [4,5], drug and growth factor delivery [6], and suturing [7].Hydrogels and composite materials based on the natural polysaccharide alginic acid (ALG) are well known and widely used in bone tissue engineering [8], drug delivery [9], and cell encapsulation [10,11].ALG molecules are linear and contain β-d-mannuronic and α-l-guluronic acid residues that are present in their pyranose forms and are linked by 1–4 bonds. Hydrogels and composite materials based on the natural polysaccharide alginic acid (ALG) are well known and widely used in bone tissue engineering [8], drug delivery [9], and cell encapsulation [10,11]. Ionotropic ALG gels are obtained by adding multiply charged cations (e.g., Ca2+ , Ba2+ , Cu2+ , Al3+ ), which act as crosslinking agents. These cations interact with the carboxylic groups of the guluronate units of the polysaccharide molecules, whereas the mannuronate units remain free [12]. ALG does not form ionotropic gels if the mole fraction of guluronic acid in the polysaccharide is less than 20–25% [13]. Modulation of Biomolecules 2019, 9, 291; doi:10.3390/biom9070291 www.mdpi.com/journal/biomolecules

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