Label-free optical biosensors based on Au2S-coated gold nanorods

In this research, two new types of optical biosensors were explored from Au2S-coated gold nanorods (Au2S-coated GNRs) chemically attached with human IgG as recognizing probes. The first type of biosensors were suspended GNRs and exhibited sensitive shift of longitudinal plasmon wavelength in response to anti-human IgG, with the limit of detection down to 67 pM. The second type of sensors were on-chip-immobilized GNRs, able to be used repeatedly through measuring the change of plasmon absorption intensity at a fixed wavelength, with the limit of detection down to 33 pM. The latter sensors suited for dynamic measurements, having linear response over rang from 33 pM to 1.35 nM. Both the types of sensors not only preserved the desirable features of common GNR sensors but also easy for preparation and manipulation. The concept and methodology suggested in this study can serve as the basis to develop new methods for molecular binding events or other applications like in medical researches.