Using electrostatic self-assembled gradient nanosensor phantoms for calibration of an optical intrinsic signal imaging system

Wide-field optical intrinsic signal (OIS) imaging has been used in functional cortex mapping for its excellent spatial resolution. To compensate for its low temporal resolution, extrinsic dye signals have been introduced. Fluorescence spectroscopy in the form of nanoengineered sensors has also been used to detect biochemical signals of molecular interactions. In this paper, oxygen-sensitive dye Ru(dpp)₃²⁺ was immobilized into nano-sized spheres by electrostatic layer-by-layer (LbL) self-assembly, and then deposited on glass slides as intensity gradients. By comparing gradient ratios and ratios of function dye Ru(dpp)₃²⁺ and reference dye between epi-fluorescence microscope and an OIS imaging system, the feasibility and efficiency of nano-sized oxygen sensors in OIS imaging were studied.