Zeta potential based colorimetric immunoassay for the direct detection of diabetic marker HbA1c using gold nanoprobes

Abstract

A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements for determination of specific diabetic biomarker glycated hemoglobin (HbA1c) using functionalised gold nanoparticles as bioprobes is reported. The assay exhibited an excellent sensitivity based on absorbance and zeta potential measurements showing the dynamic response range from 0.001-0.004 mg mL(-1) for HbA1c with a detection limit of 0.0015 mg mL(-1).

A sensitive sequential ‘on/off’ SERS assay for heparin with wider detection window and higher reliability based on the reversed surface charge changes of functionalized Au@Ag nanoparticles

“…While the color and surface Plasmon absorption band are strongly related to their state of aggregation, the internal distance on three-dimensional space, besides the size, shape, dielectric properties of the nanoparticles and environment. The color change induced by aggregation of Au NPs provides the basis for the colorimetric analysis, which has by far been used for the detection of many substances including DNA, proteins (Zhao et al, 2008;Ghosh and Pal, 2007;Wangoo et al, 2010;Li et al, 2010) andheparin (Cao andLi, 2011;Jena and Raj, 2008) as well. Remarkably, the controllably aggregated noble metal nanoparticles (NPs)-based colorimetric assays are derived by quantifying how much the heparin and the intensity ratio between transverse Plasmon peak and longitudinal one of metal colloids, which is not much convincing because the longitudinal Plasmon peak keeps broadening and red shifting in a certain range, making it hard to determine its peak position and intensity (Cao and Li, 2011).…”

Control of Electron‐transfer in Immunonanosensors by Using Polyclonal and Monoclonal Antibodies

“…Size is another important factor for nanoparticles in electrochemical biosensors. For example, in a recent study, nanoparticles in the size range of 15 to 30 nm (similar to that of biomacromolecules) were recently shown to give the improved electrochemical results compared with other particles sizes [14][15].…”

Selective label-free electrochemical impedance measurement of glycated haemoglobin on 3-aminophenylboronic acid-modified eggshell membranes

“…Currently, the quantitative analysis of HbA1c is performed with a variety of analytical techniques, including electrophoresis [4], ion-exchange chromatography [5], boronate affinity chromatography [6], mass spectrometry [7][8][9], immunoassays [10][11][12][13], electrochemical detection [14][15][16][17][18][19], piezoelectric sensors [20][21][22], chemiluminescence [23], surface plasmon resonance [24] and surface-enhanced resonance Raman spectroscopy [25]. Among these available techniques, the major drawbacks are that such methods are rather complicated, take a long time for the analysis [10] and require the use of labelled antibodies [16], expensive equipment [20,22] and/or sample preparation prior to the analysis [26].…”