Detection of [Ca2+]I Changes In Sub–Plasma Membrane Micro Domains in A Single Living Cell By an Optical Fiber–Based Nanobiosensor

An optical fiber-based nanobiosensor, for advanced detection of [Ca2+]i (i.e. intracellular Ca2+ concentration) changes in sub–plasma membrane microdomains in a single living smooth muscle cell and a single living cardiomyocyte, was successfully prepared by coating silver and then immobilizing Calcium Green–1 Dextran, a calcium ion sensitive dye, on the distal end of the nanoprobe. The constructed nanobiosensor was capable of detecting ultra–low and local intracellular calcium ion concentration within the nanomolar range, which is around the physiological level of free cytosolic calcium ion in a single living cell. The response time was less than milliseconds enabling the detection of transient elementary calcium ion signaling events associated with calcium ion microdomains. The effects of stimulants such as high potassium buffer solution and norepinephrine solution were also investigated. The resulting system could thus greatly facilitate the development of an advanced nano–diagnostic platform for in vivo and real–time sensing/diagnosing of [Ca2+]i at the single cell level.