▎ 摘　　要

NOVELTY - Working electrode comprises an array of solid, non-hollow skin piercing microprojections at an array density of at least 2,000 microprojections/cm2 disposed on an electrode substrate which is provided onto an electrode and connector support having a proximal portion comprising the sensing electrode substrate of electrode and a non-sensing distal portion for connection to connectors, contacts or leads for transfer of electrical signal, where the substrate of the microprojections, and the support are coated with a conformal nanofilm of biocompatible electrically conducting, chemically inert material which supports a redox reaction having a thickness of 5-500 nm, and where non-sensing parts of the working electrode are coated with an electronically and ionically insulating material. USE - Working electrode for in vivo pH sensing or vivo sensing of bioanalyte in medium of interest, preferably ISF, continuous bioanalyte monitoring, and transdermal sensing or transdermal capture and monitoring of bioanalyte using electrochemical sensor system or wearable device, where the bioanalyte is glucose and the disease or condition is insulin resistance, glucose intolerance, diabetes including Type 1 or Type 2 diabetes, the bioanalyte is lactate and the disease or condition is sepsis, the bioanalyte is a cancer biomarker such as an erbB2 marker present at a concentration of greater than 15 ng/mL which is diagnostic of breast cancer (all claimed). ADVANTAGE - The working electrode has high potential in early cancer detection. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) an electrochemical sensor system, which comprises electrochemical cell comprising a working electrode; (2) a wearable device, which comprises working electrode, or the sensor system; and (3) a method of diagnosis a disease or condition, which involves identifying the in vivo presence of a bioanalyte and a level of a bioanalyte in interstitial fluid (ISF) or peripheral blood associated with a disease or condition using the sensor system or the wearable device.