Coaxial microneedle assemblies and methods thereof

A device comprising:

• a hollow needle, wherein the needle has an interior surface facing a hollow lumen and an exterior surface, a distal end of the exterior surface comprises a puncturing edge, and the needle has a length of less than about 1.5 mm and/or a width or diameter of less than about 1 mm in order to avoid capillary beds in a tissue and measure a dermal interstitial fluid,
• at least one transducing wire disposed within the lumen of the needle, each transducing wire comprising a surface within the lumen and a distal end comprising an exposed surface and wherein the exposed surface of each transducing wire is conductive and optionally comprises one or more electrochemical modifications;
• and
• an insulating layer disposed upon and completely covering the surface of each transducing wire within the lumen whilst leaving the conducting surface at the distal end directly in tissue contact and exposed to the dermal interstitial fluid.