Comparative study of Physicochemical properties of novel Chitosan-GANT and PVA-GANT Hydrogels for drug delivery applications

The pharmaceutical industry is continuously researching, developing, and marketing new delivery systems to load and release variety of drugs for site-specific therapy. Scientists have discovered that three dimensional, flexible water-soluble hydrogels are the future for potential drug delivery systems. These hydrogels are intelligent by responding to environmental stimuli, like body temperature, are biocompatible since they resemble biological membranes, and can adhere to specific linings for prolonged retention time to deliver drug at the localised area. In this scope of work, novel chitosan-Gantrez-AN® was synthesised in different polymer concentrations using an environmentally friendly method, which was by steam sterilisation autoclave. The novel hydrogel was successfully synthesised, manufacturing a chemically three-dimensional network without additional toxic agents as only polymer and water were the only excipients required to formulate the hydrogels. A comparative investigation with a previously autoclaved PVA-GANT hydrogel was carried out to validate the preliminary characteristics using IR spectroscopy, to verify the presence of cross-link bonds and morphology of pore formation by SEM microscope. Texture of the hydrogel (hardness, springiness, cohesiveness, and adhesiveness) was measured using texture analyser under compression mode. The total water content and physicochemical properties such as degree of swelling was measured by thermogravimetric systems such as DSC and TGA. Finally, antimicrobial characteristics was assayed against Staphylococcus aureus and Escherichia coli bacterial strains by disk diffusion. The autoclave effectively produced transparent, bubble free hydrogels at various polymer concentrations and at two autoclave times. Both types of hydrogels synthesised derive from different chemical reaction pathways; where novel CHI-GANT hydrogel may undergo amidation synthesis developing amide bonds, PVA-GANT is formed by esterification-condensation reaction leading to ester bonds. The IR spectroscopy suggested that 1397.68 cm-1 could link to amide bonds and 1179.59 cm-1 . SEM microscope observed pore size diameter was larger in higher polymer concentration freeze dried 20% chitosan-GANT C20T90 hydrogel (42.7817.73m), and in water swollen 20% PVA-GANT P20T90 (24.477.059m) hydrogels autoclaved at 90-minutes. Although 30-minute 20% chitosan-GANT C20T30 had small pore size compared to C20T90, the pore size was uniformly distributed. 90-minute hydrogels samples autoclaved at low concentration 10% PVA-GANT (P10T90) possessed low wall thickness 0.3650.0729m between neighbouring pores. The texture analyser proved that level of hardness and cohesiveness were exceptionally low in samples composed with 10-15% polymer concentration but obtained higher adhesiveness and springiness behaviour. In the oven drying and TGA experiments, both hydrogels occupied a large quantity of water, and were fairly close to the theoretical amount of water v between the polymer: water ratio i.e. a 15% hydrogel reflects 15% polymer and 85% water, so in 90-minute 15% chitosan-GANT (C15T90) it contained 82.14% of water. The DSC thermogram clearly presented two distinct peaks attributed to free water that is freezable and from the calculations based on the melting enthalpy was able to quantify the bound unfrozen water. CHI-GANT hydrogels indicated gradual, slow swelling degree, suggesting these hydrogels can be developed as sustained/controlled drug release applications, whereas PVA-GANT hydrogels represented fast swelling properties that can be developed as future dressing systems for wound recovery. The individual GANT polymer and autoclaved hydrogels exhibited antimicrobial activity against Staphylococcus aureus and Escherichia coli, except for individual PVA and chitosan polymers. In conclusion, by changing polymer composition, concentration or autoclave time affects both internal and external hydrogel features such as cross-link density, number of hydrophilic groups or polymer chain mobility. The autoclaved hydrogels are promising materials to be designed as potential pharmaceutical drug delivery systems, which will transform new ways to deliver medicine.