Wearable physicochemical-sensing system integrated with diaper for pheochromocytoma monitoring

Pheochromocytoma is a neuroendocrine tumor characterized by excessive catecholamine secretion, leading to hypertension and complications. Vanillylmandelic acid (VMA), a stable metabolic product of catecholamines (CA), is primarily excreted in urine, with levels rising early in the disease or prior to tumor recurrence. Therefore, rapid and accurate detection of urinary VMA is essential for the early diagnosis and monitoring of pheochromocytoma. Herein, we developed a wearable physicochemical-sensing system for non-invasive in situ monitoring of biomarkers associated with pheochromocytoma. The system integrates cuffless blood pressure (BP) monitoring technology and electrochemical biosensor, utilizing screen-printing to create high-precision multi-channel electrodes. It can be integrated with diaper to detect blood pressure and biomarkers including VMA, creatinine, and pH, aiming to improve urine analysis efficiency and enhance patient experience. The VMA-to-creatinine concentration ratio was employed as an evaluative metric, with measurements calibrated against external variables including pH, temperature, and ionic strength, enabling random urine sample collection and analysis. The resulting sensor demonstrates sensitive and linear responses within the concentration ranges of 10 nM–100 μM for VMA, 100 nM–10 mM for creatinine, and 4–9 for pH. The cuffless blood pressure monitoring patch simultaneously collects dual-lead ECG and PPG, extracts features, and inputs them into a prediction model to estimate BP values. The correlation between the estimated blood pressure value of the model and the actual blood pressure value is 0.9207 (systolic blood pressure, SBP) and 0.9015 (diastolic blood pressure, DBP), respectively. We conducted further tests on the electrochemical biosensor's selectivity, reproducibility, and stability, evaluating the potential of this strategy in effectively monitoring pheochromocytoma.