Electroanalytical sensors have a major technical importance. Prominent examples are glucose and carbon monoxide sensors. SECM can be used as a characterization method in the development of new biosensors and modified microelectrodes which act as electrochemical biosensors can be used in SECM to study biological samples and materials.
Miniaturized electrochemical sensors which can be employed as microelectrodes in SECM experiments allow the detection of metabolites at the single cell level with high spatial resolution.
They can be fabricated by modification of microelectrodes, e.g by immobilizing a film of glucose oxidase (GOx) on top of the Pt core of a microelectrode. Such microelectrodes show enhanced sensitivity towards the detection of certain chemical compounds (glucose in the case of GOx). In this way, the glucose concentration above a single cell can be imaged. The uptake of glucose by the cell leads to reduced currents at the microelectrode.
Soldà, A.; Valenti, G.; Marcaccio, M.; Giorgio, M.; Pelicci, P. G.; Paolucci, F. & Rapino, S.; Glucose and Lactate Miniaturized Biosensors for SECM-Based High-Spatial Resolution Analysis: A Comparative Study. ACS Sensors, 2017, 2, 1310-1318. View article.
SECM was used to locally study the enzymatic activity of a macroscopic biosensor. An inorganic film with entrapped glucose oxidase was electrosynthesized on a Pt electrode. Topography and local variations of the film were studied using the reaction of K3[Fe(CN)6] with glucose in a feedback experiment where K3[Fe(CN)6] was generated at the microelectrode tip.
Guadagnini, L., Ballarin, B., Mignani, A., Scavetta, E., & Tonelli, D.; Microscopy techniques for the characterization of modified electrodes in the development of glucose biosensors. Sensors and Actuators B: Chemical, 2007, 126, 492-498. View article.
Fast-Scan Cyclic Voltammetry (FSCV) can be used for studying the release or uptake of many neurotransmitters, enzymes or metabolites. Very fast scan rates of about 300 V/s allow a high temporal resolution of the measurement. For the detection a carbon microelectrode is positioned close to the area of interest. Although FSCV does not require a SECM setup because it is a static technique it offers a convenient platform for electrode positioning with the 3-axis positiong system and allows combination of FSCV with scanning techniques.