Design of a microneedle-based enzyme biosensor using a simple and cost-effective electrochemical strategy to monitor superoxide anion released from cancer cells.

Early detection of Reactive oxygen species (ROS) concentration is very important in cancer diagnosis, pathological examinations, and health screening. Studies show that changes in ROS concentration occurs in a short time, causing irreparable damage to living cells and organs. Miniaturized sensors and microelectrodes are capable of online monitoring of electrochemical reactions both in vitro and in vivo. In this study, an enzymatic biosensor based on an electrochemically roughened gold microneedle electrode (RAuME) has been developed to measure superoxide anion released from prostate cancer cells. A uniform layer of reduced graphene oxide (rGO) was deposited onto the gold microelectrode through electrochemical reduction, followed by electrodeposition of yttrium hexacyanoferrate (YHCF) nanoparticles. The deposited layers improved the current response of the microneedle electrode in CV, Impedance, and Amperometric analysis. Furthermore, chitosan was utilized to superoxide dismutase (SOD) immobilization. The presence of chitosan maintained the catalytic properties of the SOD enzyme. The developed microsensor monitored the superoxide anion in a wide linear range from 0.304 to 314 μM with detection limit of 17 nm. According to the physiological concentration of the superoxide anion (10-100 nm), we hypothesized that the developed micro-biosensor can mediate a fast monitoring of ROS that facilitates early-stage cancer diagnosis and treatment.