Abstract
Here, we propose simple diamond functionalization by carboxyl termination for adenosine triphosphate (ATP) detection by an aptamer. The high-sensitivity label-free aptamer sensor for ATP detection was fabricated on nanocrystalline diamond (NCD). Carboxyl termination of the NCD surface by vacuum ultraviolet excimer laser and fluorine termination of the background region as a passivated layer were investigated by X-ray photoelectron spectroscopy. Single strand DNA (amide modification) was used as the supporting biomolecule to immobilize into the diamond surface via carboxyl termination and become a double strand with aptamer. ATP detection by aptamer was observed as a 66% fluorescence signal intensity decrease of the hybridization intensity signal. The sensor operation was also investigated by the field-effect characteristics. The shift of the drain current–drain voltage characteristics was used as the indicator for detection of ATP. From the field-effect characteristics, the shift of the drain current–drain voltage was observed in the negative direction. The negative charge direction shows that the aptamer is capable of detecting ATP. The ability of the sensor to detect ATP was investigated by fabricating a field-effect transistor on the modified NCD surface.
Highlights
Aptamers are single-stranded nucleic acids with selective binding ability obtained by the systematic evolution of ligands by exponential enrichment process from random sequences using an in vitro process [1]
Experiments were performed to determine the amount of carboxyl groups that formed on the diamond surface by VUV irradiation
The surface density of carboxyl groups determines the effective number of probe DNA molecules that can immobilize on the diamond surface
Summary
Aptamers are single-stranded nucleic acids with selective binding ability obtained by the systematic evolution of ligands by exponential enrichment process from random sequences using an in vitro process [1]. Aptamers are ideal for biosensor applications because of their high affinity, specificity, sensitivity, and stability [2,3,4,5]. Diamond substrates have been recognized as good candidates for biosensing applications [9,10]. Compared with other candidates [11,12], diamond substrates are better electrochemical transducers because of their favorable chemical properties, outstanding biocompatibility [8,9,13,14,15,16], and large potential windows [15]. Nanocrystalline diamond (NCD) has high chemical stability and biocompatibility, and it is simple to functionalize [13,14] for various biological samples [10,17,18]
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