Enhanced Colorimetric Immunoassay Accompanying with Enzyme Cascade Amplification Strategy for Ultrasensitive Detection of Low-Abundance Protein

Abstract

Methods based on enzyme labels have been developed for colorimetric immunoassays, but most involve poor sensitivity and are unsuitable for routine use. Herein, we design an enhanced colorimetric immunoassay for prostate-specific antigen (PSA) coupling with an enzyme-cascade-amplification strategy (ECAS-CIA). In the presence of target PSA, the labeled alkaline phosphatase on secondary antibody catalyzes the formation of palladium nanostructures, which catalyze 3,3′,5,5′-tetramethylbenzidine-H2O2 system to produce the colored products, thus resulting in the signal cascade amplification. Results indicated that the ECAS-CIA presents good responses toward PSA, and allows detection of PSA at a concentration as low as 0.05 ng mL−1. Intra- and inter-assay coefficients of variation are below 9.5% and 10.7%, respectively. Additionally, the methodology is validated for analysis of clinical serum specimens with consistent results obtained by PSA ELISA kit. Importantly, the ECAS-CIA opens a new horizon for protein diagnostics and biosecurity.

Portable smartphone quantitation of prostate specific antigen (PSA) in a fluoropolymer microfluidic device

“…However, colorimetric detection is still widely used in immunoassays, offering speed, simplicity, well established assay chemistry and high quality reagents, and widespread availability of cost-effective readers. For this reason researchers still focused in finding new ways to increase the performance of colorimetric detection, for example through enzymatic amplification systems (Brooks et al, 1991;Gao et al, 2014). Besides being inherently less sensitive, colorimetric detection sensitivity can also be limited by the working range of the instrument.…”

Hollow PDA-Au nanoparticles-enabled signal amplification for sensitive nonenzymatic colorimetric immunodetection of carbohydrate antigen 125

“…To this end, other materials with similar functions, such as nanoparticles, have been proposed and tested to replace enzymes in the current immunoassays (Gao et al 2014). As compared to enzyme, the use of nanoparticles in immunoassays exhibits great advantages due to the low-cost, good stability, and simplicity (Tang et al 2011b;Wang et al 2012).…”

“…As compared to other counterparts, colorimetric immunoassays have gained increased attention as a promising approach for visual analysis due to their high selectivity and ease of detection (Gao et al 2014;Place et al 1983;Qu et al 2011;Zhou et al 2012). For typical colorimetric immunoassays, detection probes are usually included to monitor the signal change as induced by cancer biomarker.…”

Nanomaterials for early detection of cancer biomarker with special emphasis on gold nanoparticles in immunoassays/sensors

“…Few recent assays with graphene sheet Jia et al, 2014) and mesoporous platinum nanoparticles , palladium nanoparticles Gao et al, 2014) and iron oxide nanoparicles (Emami et al, 2014) have high sensitivity with multiplexing and high throughput capabilty. However the exciting properties of AuNPs are always inimitable.…”