An amplified fluorescent aptasensor based on single-stranded DNA binding protein, copper and silica nanoparticles for sensitive detection of interferon-gamma.

It is great significance to identify interferon-gamma (IFN-γ), as a biological marker for diagnosis of latent tuberculosis, in serum samples. In this paper, a novel fluorescent aptasensor was fabricated and applied for sensitive and specific detection of IFN-γ. This biosensor was based on hairpin structure of oligonucleotide, single-stranded DNA-binding protein (SSB), copper nanoparticles (CuNPs) and silica nanoparticles coated with streptavidin (SNPs-Streptavidin). The presences of double-stranded DNA (dsDNA) region and poly thymine (T) in the hairpin structure of the oligonucleotide, SSB and SNPs-streptavidin caused IFN-γ determination with high selectivity and sensitivity. Upon addition of IFN-γ, the hairpin structure of the oligonucleotide was disassembled and therefore, poly T strand interacted with SSB and a weak fluorescence signal was obtained. Without introduction of IFN-γ, the hairpin structure of oligonucleotide was preserved and fluorescent CuNPs were formed on the stem region of hairpin structure of oligonucleotide, resulting in strong fluorescence intensity. Under optimal conditions, concentration as low as 1 pg/mL IFN-γ could be detected, with a linear range between 10 pg/mL and 4 ng/mL. The presented method was further performed for detection of IFN-γ in the spiked human serum samples and the recoveries were 92.52%-98.32%, showing the great potential of the proposed analytical method in biomedical analysis.