Abstract
A new single-step aptamer-based surface-enhanced fluorescent optical sensor is built, by combining an aptamer–target interaction for target recognition and a fluorophore interaction for signal enhancement. The developed aptasensor is simple, sensitive, specific and stable for the detection of thrombin. A new nanometallic Au structure in the range of 100 nm was constructed through effective electroless plating method on a Cu thin film. Cu+ ions act as sacrificial seeds for the reduction of Au2+/3+ ions to form Au nanolawns. In order to utilize the structure for a fluorescence-based sensor, aptamer conjugated with Cy3 was immobilized on the nanogold substrate through electrostatic attraction. The Au substrate was coated with chitosan (molecular weight 1000 Da). Thrombin binding aptamer (TBA) was applied as a model system demonstrating the aptamer-based fluorescence assay on nanogold substrates. Thrice-enhanced fluorescence emission was achieved with Cy3-conjugated TBA stably immobilized on the chitosan-coated Au substrate. The intensity change was proportional to the concentration of thrombin from 10 μM to 10 pM, whereas the intensity change was ignorable for other proteins such as human serum albumin (HSA). Aptamer-based assay benefited from simple immobilization of receptors and Au nanostructure contributed in building an effective surface enhancing/positively charged substrate was proved. Such an aptasensor holding high utilities for point-of-care devices by incorporating simplicity, sensitivity and selectivity in detection, low-cost for test, small sample volumes has been developed.
Highlights
Detection and tracking of proteins and other small molecules is of high priority in the field of medical diagnostics and drug development, and in biological and biotechnology research, environmental monitoring, forensic investigations, and biodefense
Strouse and co-workers further revealed a novel nanosurface energy-transfer effect occurring at the surface of gold nanoparticles (AuNPs), which leads to long-range energy-transfer-based fluorescence quenching
The fabricated gold nanostructures were immersed in the prepared chitosan solution for 4 h, after which the chitosan solution was just removed from the substrate
Summary
Detection and tracking of proteins and other small molecules is of high priority in the field of medical diagnostics and drug development, and in biological and biotechnology research, environmental monitoring, forensic investigations, and biodefense. The advantages of simplicity and specificity, the use of aptamer gold nanoparticles may be well suited for protein analysis and cancer diagnosis Those highly sensitive aptasensors based on surface plasma resonance [21], surface-enhanced resonance Raman scattering [23] and a graphene field-emit transistor require elaborate process [22] for sensor fabrication which limited their extended applications. Strouse and co-workers further revealed a novel nanosurface energy-transfer effect occurring at the surface of gold nanoparticles (AuNPs), which leads to long-range energy-transfer-based fluorescence quenching Based on this superquenching effect, AuNPs have been successfully employed to develop nanosensors for sensitive DNA detection [25,26]; importantly given that AuNPs can efficiently quench almost all fluorophores.
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