A swellable bilateral microneedle patch with core-shell structure for rapid lactate analysis and early melanoma diagnosis

Lactate is an important biomarker in sport medicine and clinical care. Conventional methods for lactate detection mostly rely on blood withdrawing which usually causes much pain, significantly reducing patient compliance. Here, we design a bilateral core-shell microneedle (MN) patch for measuring lactate level in skin with improved compliance and accuracy. The shell layer can rapidly absorb sufficient interstitial fluid (ISF) upon skin insertion, while the core layer selectively reacts with lactate in ISF and subsequently shows two visible color changes within a short time. In rats, the colorimetric patch allows determination of lactate-level changes over time after intensive exercise, which shows excellent agreement with lactate variation in blood, indicating admirable accuracy and sensitivity of lactate sensing of the bilateral core-shell MN patch. Furthermore, the MN-based sensor can recognize the abnormally increased lactate level in melanoma mice at early stage and distinguish it from the normal lactate concentration in healthy mice without driving tumor growth, suggesting a great potential for early tumors diagnosis in clinics.