Development of low cost rapid fabrication of sharp polymer microneedles for in vivo glucose biosensing applications

New approaches to enable more effective management of diabetes mellitus, such as continuous glucose monitoring are being developed both to prevent unstable episodes of hypo or hyper glycaemia and also to provide an improved user experience. One emerging approach to realize these requirements is to fabricate aminimally invasive transdermal sensor for the direct in vivo detection of glucose in the interstitial fluid. Microneedles - sharp, microscopic structures measuring less than 1 mm in length - have been previously employed to allow painless penetration of the stratum corneum for delivery of drugs and vaccines. In this work we present, ultra sharp gold coated polymer microneedle arrays (sub micron tip radii) which are fabricated using a low cost polymer replication approach. Critical dimensions of the microneedle arrays are characterized using a combination of optical and scanning electron microscopies. Fabricated microneedle devices are characterized by cyclic voltammetry to explore functionality. The voltammetric detection of glucose is performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the physiological range (2-13.5 mM). The sensors demonstrate high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol). This demonstrates potential future use of these microneedle devices for in vivo glucose detection.