Ex vivo performance evaluation of a transdermal gold injectable microneedle for tyrosinase sensing

Here, the semi-invasive direct electrochemical detection of melanoma biomarkers in non-treated skin has been envisaged. The enzyme tyrosinase (TYR) was to be addressed with a microneedle electrochemical sensor. The microneedles were fabricated by polydimethylsiloxane (PDMS) casting with stable polymers. The as-prepared microneedles (MNs) were then coated by gold sputtering. The gold MNs were finally covered by alginate/catechol to provide a liquid electrolyte layer that contained electroactive species, such as catechol, whose redox state can be linked to the concentration of TYR in the skin. The sensor showed high sensitivity of 7.52 µA·mg–1·mL TYR in dummy skin. A relative standard deviation (RSD) of 8.54 % (n=5) demonstrated that the Catechol@alginate: gold MN electrode had excellent reproducibility for continuous glucose detection. Also, five parallel Catechol@alginate: gold MN electrodes were fabricated using the same experimental setup and showed an RSD of 3.95 % (n=5). These results suggest that the electrode fabrication process was reproducible, and Catechol@alginate: gold MN biosensors demonstrated high stability for the repetitive detection of TYR. Furthermore, the sensor has high selectivity in the presence of interfering components towards TYR screening.