Christodoulopoulos, K. | bioRxiv Science

bioRxiv2026

Colorimetric Hydrogel Dressing with Smartphone Detector for Point-of-Care Wound pH Monitoring

Chronic wounds such as diabetic foot ulcers are typically more alkaline than healing wounds, making wound pH a valuable diagnostic and prognostic marker. However, point-of-care pH monitoring remains limited by the availability of point-of-care wound pH sensing systems that offer quantitative pH determination, low toxicity, and small portable detectors. Here, we report a colorimetric pH-sensing wound dressing that enables in situ pH detection using a conventional smartphone camera. The anionic pH-sensitive dye HPTS was loaded onto cationic microparticles and embedded within a calcium-crosslinked alginate hydrogel. Across the clinically relevant range of pH 6.0-9.0, increasing pH produced a progressively more intense yellow coloration, quantified through the blue channel of smartphone-acquired RGB images. The dressing displayed a strong, rapid, and reversible signal in vitro with low dye release. In a full-thickness excisional wound model in mice, wound pH changes were detected in vivo. The combination of a pH-sensitive colorimetric hydrogel with a conventional smartphone detector offers accessible wound pH monitoring at the point-of-care.

bioengineering↗

bioRxiv2024

Colorimetric detection methods of pH-sensing wound dressing for point-of-care wound diagnostics

Chronic lower extremity wounds like diabetic foot ulcers (DFUs) are a major complication of diabetes and the leading cause of lower limb amputations worldwide. Currently, DFUs are diagnosed through macroscopic evaluation, and molecular diagnostics are lacking for the disease staging, treatment selection, and evaluation of treatment success. There is a need for new diagnostic technologies combined with detection methods for point-of-care use. Preclinical and clinical data support the importance of wound pH as a biomarker in chronic wound healing, with DFUs typically exhibiting more alkaline pH values when compared to normal healing wounds. In a previous study, we developed a pH-sensing fluorescent bandage based on pyranine-loaded microparticles that were physically immobilized in an alginate hydrogel. Here, we present a second-generation pH-sensing bandage for colorimetric wound diagnostics. Pyranine was adsorbed at high concentrations onto microparticles to enable colorimetric signal detection. This approach leverages pyranines ability to change color in response to pH variations through proton exchange properties with the wound fluid. The colorimetric properties of our bandage enable signal detection by two methods suited for point-of-care use: a smartphone camera and a cost-effective homebuilt RGB detector. Analyzing the color intensity of the bandage with Red, Green and Blue absorbance values, it is possible to correlate the RGB absorbance to a pH value in the clinically-relevant range to 6.0 to 9.0 in vitro and ex vivo, as the B values decreased with the increase in pH levels, as associated with DFUs. These findings indicate the potential of colorimetric detection using smartphone cameras or home-built absorbance detectors for rapid wound diagnostics at the point-of-care. Graphical AbstractA pH-sensing bandage enables colorimetric detection of chronic wounds. The bandage absorbs wound exudate, triggering proton exchange with dye-loaded microparticles in an alginate matrix. Chronic wounds with high pH values induce strong fluorescence and yellow coloration. The signal is quantified through RGB colorimetry analysis using a smartphone camera or a homebuilt RGB detector, enabling point-of-care diagnostics for chronic wounds. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/617850v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@19aba53org.highwire.dtl.DTLVardef@13eb582org.highwire.dtl.DTLVardef@1fe8831org.highwire.dtl.DTLVardef@19f5231_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗