Signal self-enhancement by coordinated assembly of gold nanoparticles enables accurate one-step-immunoassays

Abstract

Current immunoassays are in general performed through time-consuming multi-step procedures that depend on the use of premade signal-producing reporters and often cause assay inaccuracy. Here we report an advanced immunoassay technology that resolves the delayed, complex, and inaccurate assay problems of conventional immunoassays. We have developed an accurate, rapid, simple, and label-free one-step-immunoassay based on the self-enhancement of sensitive immunoassay signals in an assay solution. The nano-scale protein particles (hepatitis B virus capsid and human ferritin heavy chain particles) were genetically engineered to present many well-oriented antibody (or antigen) probes and multi-copies of poly-histidine peptides on their surface, resulting in the construction of 3-dimensional (3D) bioprobes that chemisorb gold ions via coordination bonding and sensitively detect both antigen and antibody analytes. Systematic numerical and experimental analyses show that the signal self-enhancement happens through two coupled reactions under reducing conditions: (1) 3D bioprobe-based sensitive immuno-detection of analytes and (2) coordinated assembly of free and chemisorbed gold nanoparticles around the 3D bioprobe-analyte-associated complexes, which is followed by the quick generation of apparent optical signals. This advanced one-step-immunoassay was successfully applied to diagnostic assays requiring high accuracy and/or speed, i.e. diagnosis of acute myocardial infarction and hepatitis C through detecting a cardiac protein (troponin I) and anti-hepatitis C virus antibodies in patient sera, indicating that it is applicable to the accurate and rapid detection of both antigen and antibody markers of a wide range of diseases.

One-step-immunoassay of procalcitonin enables rapid and accurate diagnosis of bacterial infection

“…S2-S4 †). [42][43][44] However, this assay method has intrinsic problems, because assay performance is signicantly affected not only by serum viscosity that varies depending on individual physiological condition but also by non-specic adsorption of free gold ions of pre-assay solution to various serum proteins, which is associated with molecular diffusion of 3D probes and markers and gold particle formation, respectively.…”

Protein Particles Decorated with Pd Nanoparticles for the Catalytic Reduction of p-Nitrophenol to p-Aminophenol

“…In the last few decades, various nano-biomaterial composites have been reported, including 2D ordered structure composed of metal NPs and protein, co-immobilization of an enzyme and PdNPs onto mesoporous silica for tandem reaction, DNA-coated metal nanostructures, and aptamer nanoflares consisting of a gold NP core functionalized with a dense monolayer of nucleic acid aptamers for molecular detection in living cells. − Recently, we produced nano-biocomposite materials under an optimal and controllable condition, where small (1.5–5 nm) gold NPs are attached to the surface of a PP scaffold, − showing unique physicochemical properties (photothermal or superparamagnetic activity) that are applicable to cancer imaging and therapy. , Based on these previous studies, we propose the strategy for maximizing the catalytic performance of nano-biocomposites consisting of catalytic metal NPs and biomaterial scaffold, which requires some essential prerequisites as follows: (1) the size of metal NPs needs to be small enough to enlarge the catalytic surface area; (2) the exposed surface of metal NPs should be clean without being covered by surfactants; (3) a sufficient extent of surface-exposed region should exist for both metal NPs and biomaterial scaffold; and (4) the synthetic process should be controllable to ensure the reproducibility of the above prerequisites.…”