Cho Yeon Lee

Electrical Detection of Pneumococcus through the Nanoparticle Decoration Method

A simple method of nanoparticle decoration can be used in the detection of pneumococcus. After the pneumococcal bacteria were captured by an antibody (pneumococcal C-polysaccharide (PnC) antibody) between the interdigitated electrodes, the gold nanoparticles conjugated with the PnC antibodies were let to bind onto an outer membrane of the bacteria. Upon successfully dense decoration, the bacteria surface will become conductive owing to the metal nanoparticles, and a distinctive conductance change between the electrodes can be observed. Since this success ratio, or the probability of the conductance change, reflects the concentration of the analyte, a number of repeated measurements can be used in the quantification of the bacteria. In this way, we have successfully detected S. pneumoniae in the range of 10–108 CFU/mL. The limit of detection in this work is lower than that in the commercial detection kit. We hope that the nanoparticle decoration method will play a role in the facile detection of various bacteria.

Quantification of antigen by digital domain analysis of integrated nanogap biosensors

Nanogap biosensor shows a distinct conduction change upon sandwich-type immobilization of gold nanoparticle probes onto the gap region in the presence of target biomolecules. Although this large conductance change could be advantageous in distinguishing signal on or off devices, since the extent of conductance change is quite irregular even at the same analyte concentrations, it fails to extract quantitative information from its level of conductance change. In other words, the conductance change of a single device does not reflect the concentration of the target molecule. In this study, we introduce an alternative approach of interpreting the concentration of target molecules using digital domain analysis of integrated nanogap devices, where the fraction of signal-on-devices, or on-device-percentage (ODP), was translated into the concentration of the target molecule. The ODP was found to be closely related to the number density of the immobilized probes and, therefore, to be an excellent measure of the analyte concentration, which was demonstrated in the immuno-selective detection and quantification of influenza A hemagglutinin and prostate specific antigen.