Development of Crosslinked Chitosan-Gelatin Hydrogel Based pH Sensor and Hemostatic Sponge Bandage for Real Time Wound Management

Abstract

Real time wound monitoring through pH, temperature and moisture content in the wound bed has been extensively investigated during the past few decades. The pH milieu of wound is the most critical parameter as it indicates healing stage of injured tissues as well as the incidence of any impairment in normal healing process. A persistent alkaline pH exists in chronic wounds and bacterial infection however it progresses from acidic to alkaline and then revert back to acidic value in normal healing process. This study reports chitosan-gelatin hydrogel based pH sensor that can be used for real time wound management. The prepared chitosan-gelatin hydrogel is pH responsive and in combination with voltammetry method, it was tested for pH change in physiological range from 4 to 9.8. The size of hydrogel was 10 mm x 10 mm and it was fabricated by lyophilization process to sublimate the acidic solvent used during fabrication process. The hydrogel was casted on silicone mold and silver wires were embedded inside it. A highly linear response of 0.01 Volt/ unit change in pH was obtained. The source voltage is 5 Volt which upon change in sensor resistance varies and a minor change in pH is detectable through it. The pH response of the hydrogel with blood and simulated wound exudate have also been recorded and compared with standard pH measurement method. This sensor can be integrated in the commercial wound healing dressings where upon building interface with injured tissues, it will facilitate real time monitoring of the wound healing process. Chitosan composite sponge bandages with different polymers have been introduced to achieve effective hemostasis that aimed to reduce mortality rate of hemorrhage leading preventable deaths. In the second phase of our study, we investigated hemostasis potential of chitosan-gelatin sponge crosslinked with 5% glutaraldehyde and results were compared with uncrosslinked chitosan-gelatin sponge and other already reported chitosan 13 composite bandages. FTIR results showed successful crosslinking with glutaraldehyde which resulted in improved tensile (increase from 0.1MPa to 0.61MPa in crosslinked chitosan-gelatin sponge) and compressive properties (57.1% more compressible compared to uncrosslinked chitosan-gelatin sponge which was 50.1% compressible). The crosslinking affected hemostasis potential of chitosan-gelatin sponge and uncrosslinked sponge showed least absorbance (0.2) while 0.1ml crosslinked showed highest absorbance (0.974) after 30 minutes. Blood absorption capacity was highest (33.5 g/cm2) in 0.05ml crosslinked chitosan-gelatin sponge compared to 9.4 g/cm2 and 26.7 g/cm2 with 0.1ml crosslinked and uncrosslinked chitosan-gelatin sponges respectively. The high blood sorption capacity of 0.05 ml crosslinked chitosan-gelatin sponge can be related to its porosity. It exhibits roughly ellipsoid shaped pores which were less dense and has 75 μm average pore size. Pore morphology with increased size and less density is found to be a favorable factor for blood sorption however addition of glutaraldehyde and its increasing concentration inhibited blood clotting efficiency of chitosan-gelatin sponges. The developed pH sensor integrated inside the chitosan-gelatin bandage can be a potential tool for real time wound management following clinical evaluation of it.