Use of Silver Nanostructures on Microtransponders in Ultra-sensitive Assay

DESCRIPTION (provided by applicant): The main goal of the project is to increase sensitivity of the microtransponder-based multiplexed bioassays by (1) introducing a coating with silver nanostructures onto the microtransponders (MTPs) to enhance fluorescen ce, and (2) improving the fluorescence detection limit of the analyzer. The key element of the assay is the MTP, a monolithic 500 x 500 m integrated circuit chip that can transmit its identification code at a radio frequency (RF). Each chip consists of pho tocells, read-only memory (ROM), transmit logic circuitry, and an integrated antenna which, when the chip is illuminated, transmits an ID through a varying magnetic field. In an assay, the chips are derivatized with a molecular probe capable of binding to an analyte of interest that can be fluorescently labeled. The chips are read in a fluidics-based analyzer. The analyzer decodes the MTP ID and measures the fluorescence intensity on the MTP surface to yield information about molecular interactions in the a ssay. Metal-enhanced fluorescence is a phenomenon based on light-induced plasmon formation in the metal, often silver, and transmission of this energy through fluorescence. During the course of the project, we will coat MTPs with different types of sliver nanostructures, quantitate and characterize the fluorescence enhancement on the silicon surface of the MTP. In addition, the analyzer will be improved to measure very low fluorescence levels. This will be achieved by (1) using a highly sensitive low-noise photomultiplier or photon counting device and the connected electronics circuitry, (2) introducing improvements to software aimed at precise quantification of very shallow fluorescence peaks, (3) optimizing the optical path and the critical analysis of all components of the optical system, and (4) increasing the power of the excitation beam. The performance of the optimized system will be thoroughly characterized. We anticipate an overall three-order sensitivity improvement over the existing non-enhanced MT P system, which would allow for detection of biomolecules present in low femtomolar concentrations in assays where the molecules forming a sandwich have sufficiently high affinity. Several types of assays will also be developed to demonstrate the high sens itivity of the system, including assays for interleukins IL-2 and IL-6, mi RNAs and cancer markers cytochrome c and Bax.