Dual-zone swelling microneedle-smartphone platform for simultaneous colorimetric quantification of glucose and pH in diabetic wound interstitial fluid

Diabetic wounds undergo dynamic changes in local metabolism and infection-associated microenvironments, making timely assessment of wound status challenging. Herein, we report, to the best of our knowledge, the first dual-zone swelling microneedle-smartphone platform for simultaneous colorimetric quantification of glucose and pH directly from diabetic wound interstitial fluid (ISF). The platform combines a swelling microneedle patch, termed "IDB-CMN", with a companion WeChat mini program, "IDB-CMN Insight". Two spatially separated response zones are incorporated into the patch, using a glucose oxidase-horseradish peroxidase-3,3',5,5'-tetramethylbenzidine (GOx-HRP-TMB) cascade for glucose detection and m-cresol purple (mCP) for pH sensing. After local ISF uptake, the resulting colorimetric responses are analyzed by IDB-CMN Insight, which extracts RGB values from user-selected regions and converts them into quantitative glucose concentrations and pH values using pre-established calibration equations. The patch exhibited a mechanical strength of approximately 0.4 N per needle and a maximum swelling ratio of approximately 305%, with quantitative response ranges of 0.5-5.0 mg mL^-1 for glucose and pH 6.0-10.0. In non-infected and Staphylococcus aureus-infected diabetic mouse wounds, the platform captured temporal changes in local glucose and pH that were consistent with conventional measurements, while infected wounds maintained a more alkaline microenvironment. Concurrent analysis of these two parameters provides complementary information on local metabolic and infection-associated changes and may offer early indications of adverse microenvironmental shifts during wound healing, supporting future risk assessment and treatment optimization.