Colorimetric kinetic determination of potassium ions based on the use of a specific aptamer and catalytically active gold nanoparticles

Application of the catalytic activity of gold nanoparticles for development of optical aptasensors

Biosensor technology is considered to be a great alternative in analytical techniques over the conventional methods. Among many recently developed techniques and devices, aptasensors are interesting because of their high specificity, selectivity and sensitivity. Combining aptamer as a biological recognition element with gold nanoparticles (AuNPs) as probe, are becoming more general owing to their beneficial properties, including low cost and ability to analyze specific targets on-site and using naked eye. Hydrogen bonds, nucleic acid hybridization, aptamer-target and antigen-antibody binding, Raman signature, enzyme inhibition, and enzyme-mimicking activity are main different sensing strategies exploited in AuNPs-based optical aptasensors. In this review article, we discussed the recent advances in optical aptasensors with a special emphasis on the catalytic activity property of AuNPs.

Colorimetric aptasensor for progesterone detection based on surfactant-induced aggregation of gold nanoparticles

This paper proposes an aptasensor for progesterone (P4) detection in human serum and urine based on the aggregating behavior of gold nanoparticles (AuNPs) controlled by the interactions among P4-binding aptamer, target P4 and cationic surfactant hexadecyltrimethylammonium bromide (CTAB). The aptamer can form an aptamer-P4 complex with P4, leaving CTAB free to aggregate AuNPs in this aptasensor. Thus, the sensing solution will turn from red (520 nm) to blue (650 nm) in the presence of P4 because P4 aptamers are used up firstly owing to the formation of an aptamer-P4 complex, leaving CTAB free to aggregate AuNPs. However, in the absence of P4, CTAB combines with aptamers so that AuNPs still remain dispersed. Therefore, this assay makes it possible to detect P4 not only by absorbance measurement but also through naked eyes. By monitoring the variation of absorbance and color, a CTAB-induced colorimetric assay for P4 detection was established with a detection limit of 0.89 nM. Besides, the absorbance ratio A650/A520 has a linear correlation with the P4 concentration of 0.89-500 nM. Due to the excellent recoveries in serum and urine, this biosensor has great potential with respect to the visual and instrumental detection of P4 in biological fluids.