Digital immunoassay of a prostate-specific antigen using gold nanorods and magnetic nanoparticles

Abstract

Herein, a digital immunoassay was developed by counting highly confined gold nanorod (AuNR) probes with the aid of magnetic nanoparticles (MNPs). MNPs were conjugated with capture antibodies to concentrate the target analytes. AuNRs were conjugated with a mixture of the detection antibody and randomly selected DNA, where the detection antibody was applied to signal the target binding event and DNA was applied to provide sufficient negative charges. The bicomponent AuNR probes in the targetmediated immunocomplexes were eluted and confined onto a positively charged glass slide on the basis of electrostatic attraction for accurate counting. The combination of the magnetic concentration of the target analytes and the confinement of the DNA/antibody AuNR probes results in improved detection efficiency; a good linear range from 0.01 to 10 pg mL À1 and a detection limit of 8 fg mL À1 ($226 aM)were achieved for the detection of prostate-specific antigen (PSA). The proposed method offers the simultaneous advantages of high sensitivity, digital quantification accuracy, lack of requirement for signal or target amplification, wide dose response curve and low detection cost; thus, it shows good potential in practical applications.

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

“…Initially, the heterobifunctional cross-linker N-Succinimidyl-6-(3’-(2-PyridylDithio)-Propionamido)-hexanoate (LC-SPDP) enabled the introduction of reactive disulfide bonds on an IgG type antibody [ 121 ]. Later on, Traut’s reagent (2-iminothiolane), a popular protein thiolation reagent was employed to introduce sulfhydryl groups by reaction of some of the amino groups of antibodies [ 146 , 147 , 148 ]. Occasionally, CTAB molecules capping AuNR were temporarily replaced by PVP and SDS [ 147 ].…”

“…Later on, Traut’s reagent (2-iminothiolane), a popular protein thiolation reagent was employed to introduce sulfhydryl groups by reaction of some of the amino groups of antibodies [ 146 , 147 , 148 ]. Occasionally, CTAB molecules capping AuNR were temporarily replaced by PVP and SDS [ 147 ]. Other strategies have been implemented to introduce sulfhydryl groups on antibodies in a site-selective fashion, away from the antigen binding site.…”

A Sensitive and Stable Surface Plasmon Resonance Sensor Based on Monolayer Protected Silver Film

“…The immobilization process was monitored with angular spectrum setup as shown in Figure 1 . After activating the carboxyl groups of MHDA molecules on the silver or gold film with EDC PB buffer solution (10 mg/mL) [ 39 , 40 , 41 ] for about 60 min at a speed of 30 μL/min, the chip was then washed with PB buffer for ca. 25 min at the same pumping speed.…”

Time-resolved digital immunoassay for rapid and sensitive quantitation of procalcitonin with plasmonic imaging

“…Another digital immunoassay platform combines single molecule fluorescent detection with flow cytometry [14] . The third platform uses metal nanoparticles as the signal readout mechanism [15][16][17][18] . The nanoparticles can be imaged individually via dark field, interference and plasmonic optical imaging techniques [19,20] .…”