(Invited) Processing and Evaluation of Microneedle-Based Sensors for Biomedical Sensing

The biosensor applications of microneedles made by digital micromirror device-based stereolithography or two photon polymerization will be reviewed in this presentation. Microneedles are small lancet-shaped instruments that can be employed for bodily fluid sampling. In one study, carbon fiber electrodes were placed within the bores of hollow microneedles. The carbon fibers were chemically modified to enable detection of hydrogen peroxide and ascorbic acid; the functionality of the electrode-hollow microneedle devices were demonstrated with electrochemical measurements. In another study, metallized carbon paste transducers were filled within the bores of hollow microneedle arrays. Sensing of hydrogen peroxide and lactate with rhodium-dispersed carbon paste-filled microneedles was shown. Additionally, it was demonstrated that lactate was detected in the presence of physiologically relevant interfering molecules, such as uric acid, acetaminophen, and ascorbic acid. In another study, the enzymes glutamate oxidase and glucose oxidase were enclosed within poly(o-phenylenediamine) thin films; these films were incorporated in structures including hollow microneedles and solid microneedles. Detection of glutamate and glucose with high sensitivity, stability, and selectivity in undiluted human serum was shown. Another study considered the use of a solid-state ion selective electrode for potassium ions, which was prepared using three-dimensional porous carbon. This electrode was integrated with a two-photon polymerization-created hollow microneedle. The functionality of the ion selective electrode was shown over the physiologic range of potassium and in the presence of sodium ions, which served as an interferent. Application-specific and translation-relevant studies for microneedle-based biosensors will be considered.