Hapten-Grafted Graphene as a Transducer for Homogeneous Competitive Immunoassay of Small Molecules

Abstract

A hapten-grafted graphene-based biosensor by integrating both the graphene nanosheets and immunoassay sensing technologies was developed for ultrasensitive homogeneous competitive immunoassay of small molecules. The structure of hapten-grafted graphene avoids the activity loss of biomolecules immobilized onto the graphene surface and is beneficial to preserve the binding affinity between small molecule and its specific antibody. The sandwich structure formed between hapten-grafted graphene nanosheets and fluorescence-labeled antibody increases the quenching efficiency of the organic dye, thereby resulting in high signal-to-background ratios and improved sensitivity for Bisphenol A (BPA) detection. On the basis of fluorescence resonance energy transfer (FRET) and homogeneous competitive immunoassay mechanism, high BPA concentrations in the sample reduce the amount of fluorescence-labeled anti-BPA antibody bound to graphene-BPA nanosheets, thus resulting in remarkable fluorescence signals. The linear quantification of BPA over concentration ranges from 0.5 to 50 nM with a detection limit determined as 0.12 nM. These findings show that the proposed method provides a powerful tool for the rapid and sensitive detection of small molecules in biological and environmental samples.

Recent advances in carbon-based polymer nanocomposites for electromagnetic interference shielding

“…GO is a layered material consisting of hydrophilic oxygenated graphene sheets carrying oxygen functional groups [81] of hydroxyl, epoxy, carbonyl and carboxyl on their basal planes and edges, which allows the attachment of other functional groups through typical organic reactions, such as amidation, silanization, esterification, substitution and cycloaddition [69]. Modification via amidation provides reaction of GO to functional molecules such as amino acids [82], casein phosphopeptides [83], polyethylene glycol (PEG) [84][85], chitosan [86], polyethyleneimine [87][88][89], acid pectinase [90], poly(Llysine), polyurethane [91], among others [92][93][94]. Likewise, amidation, esterification [95][96][97][98][99] and silanization [100][101][102][103][104] are other approaches to modify GO with numerous functionalities [69].…”

Controlled fluorescence quenching by antibody-conjugated graphene oxide to measure tau protein

“…The GO surface is not only a nano-scale binding platform, but is also an energy acceptor [32][33][34][35] that quenches the fluorescence of tau-FITC. Because quenching occurs in close proximity, only the tau-FITC adsorbed on the antibody-conjugated GO became quenched [36][37][38][39]. As the number density of binding sites was limited to the modified GO, more adsorbed tau analyte resulted in stronger fluorescence signal from free tau-FITC in the solutions.…”

Quantitative Fluorescence Quenching on Antibody-conjugated Graphene Oxide as a Platform for Protein Sensing

“…In this case, the GO surface not only played a role as a binding platform but also as an energy acceptor9101112 to quench the fluorescence of IgG-FITC910. Since quenching occurs in close proximity13, only the IgG-FITCs that were adsorbed on antibody-conjugated GO would be quenched1415161718. As the number density of the binding sites was limited on the modified GO, more adsorbed analyte IgG proteins resulted in a stronger fluorescence signal from free IgG-FITCs in the solutions.…”