Impedance Biosensing atop MoS2 Thin Films with Mo-S Bond Formation to Antibody Fragments Created by Disulphide Bond Reduction

Immobilization of antibody fragments to 3-phenoxybenzoic acid (3-PBA), which are created by disulphide bond (S-S) reduction with tris (2-carboxyethyl) phosphine (TCEP), is reported atop MoS2 and Cu-doped MoS2 thin films. MoS2 and Cu-doped MoS2 thin films are electrodeposited using previously reported methods and tested for their ability to immobilize antibody fragments, before and after annealing in Ar at 500 degrees C for 3 h. This annealing procedure removes excess sulphur in the as-deposited films, and creates coordinatively unsaturated Mo sites that are highly reactive towards sulphur, as previously reported for MoS2 hydrodesulphurization catalysts. As demonstrated by electrochemical impedance spectroscopy (EIS) measurements, both annealed MoS2 and Cu-doped MoS2 thin films adsorb antibody fragments through Mo-S bond formation, unlike the as-deposited films. Impedance detection of 3-PBA is reported utilizing antibody fragments bound to both materials, with a sensitivity of 2.7x10(8) omega cm(2) M-1 and a detection limit of 2.5x10(-6) M atop MoS2, and a sensitivity of 5.9x10(8) omega cm(2) M-1 and a detection limit of 3.8x10(-6) M atop Cu-doped MoS2. The rms surface roughness obtained by atomic force microscopy (AFM) measurements atop annealed MoS2 and Cu-doped MoS2 ranges from 60-140 nm, so the methods described herein are not limited to ultra-smooth substrates.