A fluorescence aptasensor based on two-dimensional sheet metal-organic frameworks for monitoring adenosine triphosphate.

In the present study, a facile fluorescence aptasensor based on two-dimensional sheet metal-organic frameworks of N,N-bis(2-hydroxyethyl)dithiooxamidato copper(II) (H2dtoaCu) was developed for the sensitive detection of adenosine triphosphate (ATP). The sensing mechanism was based on the noncovalent interaction between FAM-labeled (fluorescein amidite) ATP aptamers and H2dtoaCu. In the absence of ATP, the FAM-labeled aptamer readily adsorbs onto H2dtoaCu, mainly via π-π stacking and hydrogen bond interactions between the nucleotide bases and the H2dtoaCu surface, leading to the reduction of fluorescence intensity of the FAM by photoinduced electron transfer (PET). In the presence of ATP, the FAM-labeled aptamer specifically forms ATP-binding aptamer complexes which exhibit only weak adsorption on the H2dtoaCu surface. Thus, the fluorescence of the FAM-labeled ATP aptamer remained largely unchanged. The fluorescence aptasensor exhibited a good linear relationship between the fluorescence intensity and the logarithm concentration of ATP over a range of 25-400 nM, with a detection limit of 8.19 nM (3S/N). ATP analogs such as guanosine triphosphate, uridine triphosphate, and cytidine triphosphate have negligible effect on the aptasensor performance due to the high selectivity of the ATP aptamer to its target, showing promising potential in real sample analysis.

MnO2 nanosheet-assisted ligand-DNA interaction-based fluorescence polarization biosensor for the detection of Ag+ ions.

Silver (Ag+) ions are highly toxic to aquatic organisms and accumulate in the human body via the food chain. Therefore, the development of sensitive and selective quantitative analytical methods for detecting trace amounts of these ions is necessary. In the present study, a MnO2 nanosheet-assisted, ligand-DNA interaction and fluorescence polarization-based method was developed, for the first time, for sensitive detection of Ag+. The addition of Ag+ to the preformed proflavine-DNA complex induced the release of proflavine, which elicited weak changes in fluorescence polarization. The subsequent addition of MnO2 nanosheets magnified the observed changes, making this a feasible method for the detection of Ag+. The calibration graphs indicated good linearity over the concentration ranges of 30-240nM for Ag+, with a detection limit (S/N=3) of 9.1nM. This method additionally exhibits high selectivity. The mechanism underlying the changes in fluorescence polarization caused by the addition of Ag+ in the presence of MnO2 nanosheets was further explored in this study. These findings demonstrate that the present MnO2 nanosheet-assisted fluorescence polarization biosensor may represent a promising tool for the detection of Ag+ ions. The results for practical detecting Ag+ proved that this biosensor can be applied to environmental water sample analysis.