Flexible pH‐Sensing Hydrogel Fibers for Epidermal Applications

Abstract

Epidermal pH is an indication of the skin’s physiological condition. For example, pH of wound can be correlated to angiogenesis, protease activity, bacterial infection, etc. Chronic non-healing wounds are known to have an elevated alkaline environment, while healing process occurs more readily in an acidic environment. Thus, dermal patches capable of continuous monitoring of pH can be used as point-of-care systems for monitoring skin disorder and the wound healing process. Here, we present pH-responsive hydrogel fibers that can be used for long-term monitoring of epidermal wound condition. We load pH-responsive dyes into mesoporous microparticles and incorporate them into hydrogel fibers developed through microfluidic spinning. The fabricated pH-responsive microfibers are flexible and can create conformal contact with skin. The response of pH-sensitive fibers with different compositions and thicknesses are characterized. The suggested technique is scalable and can be used to fabricate hydrogel based wound dressing with a wide range of sizes. Images of the pH-sensing fibers during real-time pH measurement can be captured with a smart phone camera for convenient readout on-site. Through image processing, a quantitative pH map of the hydrogel fibers and the underlying tissue can be extracted. The developed skin dressing can act as a point-of-care device for monitoring the wound healing process.

A Device to Predict Short-Term Healing Outcome of Chronic Wounds

“…Unlike previous approaches that directly tested the wound environment, we have documented the ability to measure and create a visual map of the pH environment on the wound contacting side of discarded wound dressings to identify the state of healing and a window into the short-term healing outcome based on the alkalinity level. [52][53][54] This approach offers a number of advantages. First, it is noninvasive and does not involve any direct contact with the patient.…”

Flexible Substrate-Based Devices for Point-of-Care Diagnostics

“…In another report, a flexible pH electrochemical sensor array was developed on polyaniline, and it showed a linear dynamic range of pH from 4–10 [57]. Recently, a flexible hydrogel fiber-based dressing has been developed for monitoring pH during wound healing [58]. In this study, mesoporous microparticles loaded with pH sensitive dyes were incorporated into flexible hydrogel fibers via spin coating.…”

“…Smartphone and computer-based wireless electronics have been tethered with wearable devices to acquire sensing signals, analyze data, and report and transfer clinical results for POC applications [58, 65–70]. For example, a wearable biosensor attached to tooth enamel was recently developed for detection of bacteria in saliva (Figure 4C) [71].…”

Orange‐Emissive Carbon Quantum Dots: Toward Application in Wound pH Monitoring Based on Colorimetric and Fluorescent Changing

“…Over the past years, apart from developing advanced biomaterials for promoting wound healing, there are growing evidences to suggest that the determination of surface pH value for wound in nonhealing condition or infection status is of paramount importance in preventing exacerbations, and is also helpful for therapeutic interventions in wound care. To date, various systems have been constructed for the realization of monitoring pH that was related to wound status, such as dye immobilization technique, micromachined‐based transducer, and screen‐printed pH potentiometric sensor or voltammetric sensor . Although these wound pH sensors fabricated on the basis of electrochemical or colorimetric performances are acceptable with respect to accuracy and sensitivity, each detection system is not perfect.…”