Gold Nanoparticles-based Biosensor For Biomolecular Detection

Biosensor is a device which composed of recognition element andtransducer, can convert molecular recognition events to physicallydetectable signal such as optical or electric signal. With the development ofbiosensors，it’s necessary to exploit new materials and transducers toimprove selectivity and sensitivity. In this paper, we developed threebiosensors based on gold nanoparticles (AuNPs).(1) Colorimetric biosensor for tyrosine (Tyr) detection. A colorimetricbiosensor based on the enzymatic growth of AuNPs using Tyrosinase (TR)was developed for Tyr detection. The optimal Cu2+concentration and pH ofgrowth solution (containing TR, Tyr, chlorauric acid and stabilizing agent)were discussed. Results showed that the limit of detection (LOD) wasabout2×10-6mol/L under the optimal condition. Furthermore, the additionof Cu2+to growth solution could shorten the reaction time to0.5h, whilethe LOD of Tyr was not been effected obviously.(2) Liquid crystal biosensor for Tyr detection. A liquid crystalbiosensor based on enzymatic growth of AuNPs was proposed for Tyrdetection. TR was firstly immobilized on the glass slides which were modified by APTES/DMOAP mixed self-assembled monolayers (SAM)and glutaraldehyde. And then, the glass sides were immersed into a growthsolution containing different concentrations of Tyr. In this method, TRstimulated the biocatalyzed hydroxylation of Tyr to L-DOPA which couldreduce Au3+into AuNPs in the growth solution. The formation of AuNPscould greatly change the surface topology and induce a homeotropic-to-tiled transition of LC molecules, resulting in significant changes incorresponding of optical appearances under the crossed polarized light.Results showed that the presented LC biosensor was highly sensitive to Tyrwith a limit of detection of6×10-7mol/L, which was lower thencolorimetric biosensor. Furthermore, this study offers a simple, high-specific and label-free method with naked eye.(3) Surface plasmon resonance (SPR) biosensor for Ischemia modifiedalbumin (IMA) detection. In this section, we developed a SPR biosensorfor sensitive detection of IMA by using mixed self-assembled monolayerson the gold film. Results showed that the LOD was100ng/L for directdetection, while, as to signal enhanced detection using AuNPs, the LODwas less than10.0ng/L. Compared with other methods, the presentedbiosensor exhibits good repetition and high sensitivity.