Design of a Fluorescence Turn-on and Label-free Aptasensor Using the Intrinsic Quenching Power of G-Quadruplex to AMT

DNA Aptamer Beacon Probe (ABP) for Monitoring of Adenosine Triphosphate Level in SW480 Cancer Cells Treated with Glycolysis Inhibitor 2-Deoxyglucose

Early cancer screening enables timely detection of carcinogenesis, and aids in prompt clinical intervention. Herein, we report on the development of a simple, sensitive, and rapid fluorometric assay based on the aptamer probe (aptamer beacon probe, ABP) for monitoring the energy-demand biomarker adenosine triphosphate (ATP), an essential energy source that is released into the tumor microenvironment. Its level plays a significant role in risk assessment of malignancies. The operation of the ABP for ATP was examined using solutions of ATP and other nucleotides (UTP, GTP, CTP), followed by monitoring of ATP production in SW480 cancer cells. Then, the effect of a glycolysis inhibitor, 2-deoxyglucose (2-DG), on SW480 cells was investigated. The stability of predominant ABP conformations in the temperature range of 23-91 °C and the effects of temperature on ABP interactions with ATP, UTP, GTP, and CTP were evaluated based on quenching efficiencies (QE) and Stern-Volmer constants (K_SV). The optimized temperature for best selectivity of ABP toward ATP was 40 °C (K_SV = 1093 M^-1, QE = 42%). We have found that the inhibition of glycolysis in SW480 cancer cells by 2-deoxyglucose resulted in lowering of ATP production by 31.7%. Therefore, monitoring and modulation of ATP concentration may aid in future cancer treatment.

Fractionation of Single-stranded DNAs with/without Stable Preorganized Structures Using Capillary Sieving Electrophoresis for Aptamer Selection

Aptamers, single-stranded DNAs/RNAs with a strong and specific interaction towards a target molecule, have wide applications in the fields of medicine and biosensors. In conventional aptamer selection methods, it is difficult to obtain "preorganized" and/or "induced-fit" type of aptamers selectively. In this study, separation and fractionation of single-stranded DNAs with/without stable preorganized structures were carried out using capillary sieving electrophoresis. The fractionated DNAs showed different mobilities and thermodynamic stabilities of their secondary structures; this outcome is deemed to be necessary for the synthesis of novel aptasensors with a desirable sensing mechanism.

Graphene-Based FRET Aptasensors

Graphene-based FRET aptasensors can be realized only by unique combinations of aptamer that can be freely functionalized by chemical modification, and graphene/graphene oxide that works as an excellent fluorescence acceptor at the same time as aptamer adsorbates. This review describes the principles of the sensor, several applications to microchannel devices, improvement of the sensing performance by molecular design of the aptamer and remarks on future prospects based on an introduction of recent works and achievements, including the author's paper. The sensor employs DNA modified with graphene/graphene oxide at the terminal as the molecular probe. This system is supported by the excellent property of DNA that does not lose the molecular recognition ability even due to a chemical modification at the terminal. I hope that this review will be useful for developing research on higher performance of graphene aptasensors in the future.