Real-Time Electrochemical Monitoring of Adenosine Triphosphate in the Picomolar to Micromolar Range Using Graphene-Modified Electrodes

Abstract

We report on a competitive electrochemical detection system that is free of wash-steps and enables the real-time monitoring of adenosine triphosphate (ATP) in a quantitative manner over a five-log concentration range. The system utilizes a recognition surface based on ATP aptamer (ATPA) capture probes pre-bound to electro-active Flavin adenine dinucleotide (FAD) molecules, and a signaling surface utilizing graphene (Gr) and gold nanoparticle (AuNP) modified carbon paste electrode (Gr-AuNP-CPE) that is optimized to enhance electron transfer kinetics and signal sensitivity. Binding of ATP to ATPA at the recognition surface causes the release of an equivalent concentration of FAD that can be quantitatively monitored in real-time at the signaling surface, thereby enabling a wide linear working range (1.14 ×10−10–3.0×10−5M), a low detection limit (2.01×10−11M using graphene and AuNP modified glassy carbon), and fast target binding kinetics (steady-state signal within 12 minutes at detection limit). Unlike assays based on capture probe-immobilized electrodes, this double-surface competitive assay offers the ability to speed-up target binding kinetics by increasing the capture probe concentration, with no limitations due to intermolecular coulombic interactions and non-specific binding. We utilize the real-time monitoring capability to compute kinetic parameters for target binding and to make quantitative distinctions on degree of base-pair mismatch through monitoring target binding kinetics over a wide concentration range. Based on simplicity of the assay chemistry and the quantitative detection of ATP within fruit and serum media, as demonstrated by comparison of ATP levels against those determined using a standard HPLC-UV absorbance method, we envision a versatile detection platform for applications requiring real-time monitoring over a wide target concentration range.

Removal of humic acid from aqueous solution using UV/ZnO nano-photocatalysis and adsorption

“…Photocatalysis has been successfully used for the oxidation of many organic pollutants by advanced oxidation. Heterogeneous photocatalysis disrupts the mineralization of most organic compounds [8][9][10][11][12][13][14][15][16][17]. Heterogeneous metal oxides such as ZnO have the potential to remove organic substances from aquatic environments in the presence of ultraviolet light.…”

Recent advances in electrochemical biosensors based on graphene two-dimensional nanomaterials

“…This biosensor can simultaneously monitor the glucose and lactate in vivo with little cross-talk. With the similar strategy, a real-time graphene based electrochemical biosensor for monitoring of adenosine triphosphate (ATP) was constructed utilizing an ATP aptamer (ATPA) capture probes profound to flavin adenine dinucleotide (FAD) molecules (Sanghavi et al, 2013). The system could quantitatively monitor FAD releasing in real time.…”

A label-free fluorescence strategy for sensitive detection of ATP based on the ligation-triggered super-sandwich

“…The correlation equation is ΔF¼59.45þ 65.97 log C with a correlation coefficient of 0.9872. The detection limit was calculated to be 200 pM (3s/k, where s is the relative standard deviation and k is the slope of the calibration graph, n ¼11), providing superior detection sensitivity compared with aptamer-based fluorescence strategies (Sanghavi et al, 2013;Xu et al, 2014;Zhang et al, 2012), and it is comparable with the T4 DNA-based strategies (Ma et al, 2012(Ma et al, , 2013. The high sensitivity can be achieved owing to the following factors: (1) T4 DNA ligase can efficiently help the formation of the super-sandwich in the homogeneous solution and (2) an 800-1000 fold increase of the fluorescence intensity of SG I can be obtained when it is intercalated into the duplex DNA while the formed super-sandwich can provide more binding points for the dye.…”