Abstract
Using gold nanoparticles (AuNPs) on “capillary enzyme-linked immunosorbent assay (ELISA)”, we produced highly sensitive and rapid assays, which are the major attributes for point-of-care applications. First, in order to understand the size effect of AuNPs, AuNPs of varying diameters (5 nm, 10 nm, 15 nm, 20 nm, 30 nm, and 50 nm) conjugated with Horseradish Peroxidase (HRP)-labeled anti-C reactive protein (antiCRP) (AuNP•antiCRP-HRP) were used for well-plate ELISA. AuNP of 10 nm produced the largest optical density, enabling detection of 0.1 ng/mL of CRP with only 30 s of incubation, in contrast to 10 ng/mL for the ELISA run in the absence of AuNP. Then, AuNP of 10 nm conjugated with antiCRP-HRP (AuNP•antiCRP-HRP) was used for “capillary ELISA” to detect as low as 0.1 ng/mL of CRP. Also, kinetic study on both 96-well plates and in a capillary tube using antiCRP-HRP or AuNP•antiCRP-HRP showed a synergistic effect between AuNP and the capillary system, in which the fastest assay was observed from the “AuNP capillary ELISA”, with its maximum absorbance reaching 2.5 min, while the slowest was the typical well-plate ELISA with its maximum absorbance reaching in 13.5 min.
Highlights
Recent interest in point-of-care (POC) applications [1] has prompted researchers to develop a wide range of immunoassay methods that display low-cost enhanced performance while not requiring help from an expert or facilities
A new assay system was devised by applying AuNPantiCRP-Horseradish Peroxidase (HRP) on the “capillary enzyme-linked immunosorbent assay (ELISA)”
In order better to see the size effect on catalytic efficiency, the normalized values of the optical densities were plotted against diameters of AuNPs (Figure 2b), in which the inverse relationship plateaued with AuNPs larger than 20 nm
Summary
Recent interest in point-of-care (POC) applications [1] has prompted researchers to develop a wide range of immunoassay methods that display low-cost enhanced performance while not requiring help from an expert or facilities. We reported a highly-sensitive assay in which a capillary tube was used as a platform for POC purposes [5]. Based on typical surface chemistry in the simple structure of a capillary tube, the combined assay system resulted in enhancement in sensitivity and assay time. (AuNPantiCRP-HRP) and the “capillary ELISA”, which produces multiple benefits such as high sensitivity, short assay time and the shift of the linear region to lower concentration range, is likely to be an advantageous candidate as an assay system towards salivary CRP for POC purposes
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