A fluorometric aptamer based assay for cytochrome C using fluorescent graphitic carbon nitride nanosheets

A method is introduced for the fluorometric turn-on detection of cytochrome C (cyt c) by using a specific aptamer and nanosheets composed of fluorescent graphitic carbon nitride (g-C3N4) nanosheets. Bulk g-C3N4 was obtained by pyrolysis of melamine at 550 °C. The nanosheets were characterized by scanning electron microscopy and X-ray diffraction. The material was then subjected to protonation and exfoliation to obtain blue fluorescent g-C3N4 nano-sheets. The adsorption of aptamers on the surface of the g-C3N4 nanosheets leads to quenching of its fluorescence (measured at excitation/emission wavelengths of 320/450 nm), but fluorescence is restored on addition of cyt c. Response is linear in the 16 to 140 nM cyt c concentration window, and the detection limit is as low as 2.6 nM. The assay is simple, inexpensive, and can be easily performed. It is selective for cyt c over a number of interfering species. The method was successfully applied to the determination of cyt c in spiked human serum samples.