A pH-Indicating Colorimetric Tough Hydrogel Patch towards Applications in a Substrate for Smart Wound Dressings

Abstract

Abstract:The physiological milieu of healthy skin is slightly acidic, with a pH value between 4 and 6, whereas for skin with chronic or infected wounds, the pH value is above 7.3. As testing pH value is an effective way to monitor the status of wounds, a novel smart hydrogel wound patch incorporating modified pH indicator dyes was developed in this study. Phenol red (PR), the dye molecule, was successfully modified with methacrylate (MA) to allow a copolymerization with the alginate/polyacrylamide (PAAm) hydrogel matrix. This covalent attachment prevented the dye from leaching out of the matrix. The prepared pH-responsive hydrogel patch exhibited a porous internal structure, excellent mechanical property, and high swelling ratio, as well as an appropriate water vapour transmission rate. Mechanical responses of alginate/P(AAm-MAPR) hydrogel patches under different calcium and water contents were also investigated to consider the case of exudate accumulation into hydrogels. Results showed that increased calcium amount and reduced water content significantly improved the Young's modulus and elongation at break of the hydrogels. These characteristics indicated the suitability of hydrogels as wound dressing materials. When pH increased, the color of the hydrogel patches underwent a transition from yellow (pH 5, 6 and 7) to orange (7.4 and 8), and finally to red (pH 9). This range of color change matches the clinically-meaningful pH range of chronic or infected wounds. Therefore, our developed hydrogels could be applied as promising wound dressing materials to monitor the wound healing process by a simple colorimetric display, thus providing a desirable substrate for printed electronics for smart wound dressing.

A Multifunctional Pro‐Healing Zwitterionic Hydrogel for Simultaneous Optical Monitoring of pH and Glucose in Diabetic Wound Treatment

“…As shown in Figure a, the color of PCB hydrogel discs embedding phenol red and enzymes (PCB‐PE‐E) changed from yellow to red with the increasement of pH values. The adsorption peak at 560 nm (Figure b) corresponded to the n –π* transition from benzenoid to quinoid excitonic when environment solution became more alkaline . The color change in AWE solution was similar to that of PBS solution, indicating that the phenol red transition was not disturbed by the proteins in AWE after PCB hydrogel immobilization.…”

β-Glucan-Based Wet Dressing for Cutaneous Wound Healing

“…As infected wound beds and exudate fluid have pH values ranging from 7.5 to 8.9, the higher swelling ratio of the PVA/b-glucan hydrogel under alkaline conditions makes it a better candidate for removing oozes from the wound bed while maintaining a moist environment. 15 As a potent macrophage stimulator, b-glucan plays a vital role in the dynamic wound healing process by releasing wound growth factors through macrophage stimulation. 16 Healing efficiency evaluated at the microscopic level using H&E staining revealed abnormal deposition of the epidermis into the dermis layer in the control groups on day 17.…”

Role of pH Value in Clinically Relevant Diagnosis

“…Monitoring and manipulating pH can be a critical tool for preventing and treating chronic wounds. Studies have reported on pH value monitoring combined with pH-activated drug control release systems and smart wound dressings and bandages [11][12][13][14][15].…”

“…Recently, multiple innovative and elegant smart wound dressings combined with either pH sensors or drug control-released carriers have been extensively studied [11][12][13][14][15]. With these promising Most human-pathogen bacteria are inhibited by the acidic milieu on the surface of normal human skin, but this shield is disturbed when skin is wounded.…”