Scanning Electrochemical Microscopy of Individual Pancreatic Islets

Abstract

Scanning electrochemical microscopy (SECM), a non-invasive variant of scanning probe microscopy, can be used to measure oxygen uptake or insulin secretion of isolated murine pancreatic islets in the presence of low and high physiological glucose concentrations levels. SECM imaging of islet topography and islet oxygen uptake is accomplished by the use of a redox mediator that cannot penetrate into the cell membranes of the islet coupled to direct reduction of oxygen at the SECM tip. An insulin sensing ultramicroelectrode (UME), adapted from a macro-scale insulin sensor incorporating a multiwalled carbon nanotube/dihydropyran film developed in our lab previously, was used for the direct electrochemical detection of insulin levels within extracellular media in real-time. We were able to stimulate and record increased insulin production in a single pancreatic islet by raising the concentration of extracellular glucose to the physiological 'high level.' These experiments generated probe scan curves (PSCs) for insulin production in the extracellular media surrounding single pancreatic islets extracted from male mice. This research is a part of an ongoing attempt to increase the scope of application for Bio-SECM, both through the adaptation of specialized biosensors and application of existing techniques for biological analysis of single cells and micro-organs.

Strategies for fabrication of highly-dense ordered arrays of metal microdisks by the scanning electrochemical microscopy microwriting approach

“…This electrode can be used to induce a local chemical perturbation that causes a response of the studied single system, which is detected by the SECM tip. Such strategy can be used to improve the control of SECM studies of metabolic processes on cells [42,43], catalysis, electrocatalysis, and photocatalysis on nanoparticles [44][45][46], among many other systems. The application of this technique for modification of well-defined surfaces with tipgenerated species (e.g.…”

Biological imaging with scanning electrochemical microscopy

“…Exotic targets for biological SECM studies were salt glands on the leaf of the halophyte Cynodon dactylon (L.) [70] and chloroplasts and their thylakoid membranes for which local photosynthetic flux measurements have been attempted [71]. SECM study entries into the literature databases that underline well the wide applicability of scanning electrochemical probe-based cellular analysis are examinations of the differentiation status of embryonic stem cells [72], evaluation of the respiration activity of blastocysts [73], monitoring intracellular enzyme activity of HeLa cells [74], analysis of beat fluctuations and oxygen consumption of cardiomyocytes [75], characterization of Ag + toxicity on fibroblast cells [76], inspection of the multi-drug resistance of adenocarcinoma cervical cancer cells [77], the detection of reactive oxygen species in prostate cancer cells [78], the creation of insulin release profiles of single pancreatic islets [79] and the disclosure of Cd 2+ -induced variability in the permeation properties of human bladder cancer cells [80,81]. Recent activities also addressed topics such as SECM-based inspections of heavy metal (chromium) cell toxicity [82,83], quantitative detection of protein markers for lung cancer [84], real-time monitoring of metabolic crosstalk between neighbouring bacterial cells [85], spatial mapping of molecular uptake of chemical species at living cells [59] and the pH dependence of yeast cell viability and metabolism [66].…”

Advances and Perspectives in Chemical Imaging in Cellular Environments Using Electrochemical Methods

“…Noteworthy examples include carbon microelectrodes that have been modified with [NiFe]-hydrogenase embedded in a viologen-modified redox polymer hydrogel to produce a microbiosensor for hydrogen detection with high sensitivity (30 times higher current associated with hydrogen generation as compared with a bare Pt microelectrode) in scanning photoelectrochemical microscopy (SPECM) [89]. The real-time direct electrochemical detection of insulin was realized by the development of a miniaturized insulin sensor, by the incorporation of a multi-walled carbon nanotube (MWCNT)/dihydropyran film onto a 7 µm carbon fiber UME [90]. This sensor was used to measure insulin within extracellular media in the vicinity of a single pancreatic islet by performing a linescans over the islet, at different extracellular glucose concentrations.…”