OPTICAL NANOSENSORS FOR SUBCELLULAR CHEMICAL IMAGING

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The objective is to produce optical nanosensors for direct, real-time chemical imaging of cellular membranes and intracellular processes. These sensors will monitor pH, calcium, magnesium, sodium, potassium, chloride, oxygen, nitrite, nitric oxide, carbon dioxide and glucose. The sample size required for these sensors will be a million to a billion times less than for current fiber-optic sensors, and so will the absolute detection limit. These sensors will also be 1O0-1000 times smaller and their response times 1OO-1000 times shorter. The method capitalizes on an already demonstrated ability to construct such robust and ultra-small sensors and on a new universal technique for making fluorescent cation and anion sensors, based on utilizing as is the best ionophores available from electrochemical sensors. Specifically, we propose to make and demonstrate submicrometer fiber-optic sensors for the above list of analytes. For the same analytes we also propose a new, cell immplantable optical nanosensor ("pebble"), which is biocompatible and only occupies one millionth of the cell's volume. A group of intracellular pebble sensors can provide either multiple analyte information or single analyte fluxes. The proposed nitric oxide biosensor is the first optical NO sensor to combine reversibility, selectivity and fast response with an excellent detection limit. This design is also miniaturizable. The carbon dioxide, magnesium ion and calcium ion sensors are also new designs and measure activities. Also, having just constructed an advanced version of a scanning near-field-optical microscope, we plan to combine it with our fiber-optic sensors into a scanning-fiber-optic chemical imagery with a spatial resolution down to 100-200 nm and a millisecond time resolution. Cellular and subcellular chemical imaging will be carried out on rat embryos, mouse oocytes and human neuroblastoma cells. Such nano-chemical sensors and mappings are expected to revolutionize bio-medical research: the resulting technology will speed up by orders of magnitude various biochemical test protocols and also make possible cellular microbiology investigations on subcellular samples, with single channel resolution, resulting in chemical space-time mappings as a function electrophysiological cell input. The long range goal is to achieve single molecule on of the chemical spatial resolution and chemical sensitivity.