Biosensing with Localized Surface Plasmon Resonance Based on Cap-Shaped Gold Nano-Particles

In this paper, the optical biosensors based on cap- shaped gold nano-particles have been constructed by evaporating gold on polystyrene and silica microspheres to form Au caps, which show a novel localized surface plasmon resonance (LSPR). The gold surface on silica spheres modified with a carboxymethyl dextran layer was used for sensing of anti-avidin D with a detection limit of 5.0 nmolldrL^-1 and a sensitivity of 3.4 times 10^-3 nmldrLldrnmol^-1, which was based on surface-bound avidin molecule. Furthermore, a double stranded DNA (dsDNA) with a binding site of hexa sequence AGGTCA for a nuclear receptor, retinoid X receptor beta (RXRbeta), has been successfully immobilized on gold surface via a specific interaction between biotin moiety and streptavidin, and applied to selective recognition of small molecule nuclear ligands like 9-cis retinoic acid.