A one-step, electrochemical biosensing strategy that is based on transport of signaling CdS nanoparticles controlled by biomolecules.

ABSTRACT

A novel, one-step electrochemical biosensing technique has been developed by utilizing a strategy in which a biomolecule controls transport of CdS-signaling nanoparticles to the surface of an electrode. The viability of this approach was explored using DNA as a model target biomolecule. The capture and signaling probes both contain nucleic acid sequences that are complementary to the target DNA. The detection chamber consists of a gold matrix modified with the capture probe on the bottom, a glassy carbon (GC) working electrode on the top, and a buffered electrolyte containing the signaling probe conjugated with the CdS nanoparticle. When target DNA is not present in the chamber, the CdS-signaling probe is freely transported to the GC electrode where CdS accumulates during the preconcentration step and undergoes electrochemical anodic stripping voltammetry (ASV) that subsequently generates a current signal during the following oxidative stripping step. On the other hand, target DNA present in the sample undergoes simultaneous hybridization to both the capture and signaling probes in a sandwich-like manner. This phenomenon leads to fixation of the CdS nanoparticles on the bottom of the chamber, thus preventing their electrochemical reduction on the GC electrode. As a result, the electrochemical signal is reduced in the presence of target DNA. Based on the reduction of the current signal, target DNA from C. trachomatis was successfully detected without the need for any complicated secondary procedures. This electrochemical one-step detection method could serve as a conceptually new technology enabling highly convenient biosensing that is applicable to point-of-care testing (POCT).