Ultrasensitive aptamer fluorometric detection of IFN-γ by dual atom transfer radical polymerization amplification

Ultrasensitive aptamer fluorometric detection of gamma-interferon by dual ATRP amplification. [Display omitted] •A new aptamer fluorometric protein sensor was fabricated by dual ATRP amplification.•This supersandwich fluorescence method has great potential in realize ultrasensitive protein (IFN-γ) detection in human serum.•This novel preparation is simple, gentle and convenient. Exploiting biological detection methods with high selectivity and sensitivity has been an urgent demand for low abundance biomolecules. Herein, an ultrasensitive aptamer fluorometric method of protein detection was fabricated via a sequential dual atom transfer radical polymerization (ATRP). For the first time, surface-initiated dual ATRP was utilized to make the fluorometric signal amplification for gamma-interferon (IFN-γ) protein assay. Two aptamers are used as protein probes, which can form a high stable and selective “aptamer/ protein/aptamer” sandwich structure. One aptamer probe is attached on superparamagnetic nanoparticle via surface self-assembled, the other one is linked with initiators of dual ATRP amplification by click chemistry formed triazole group. With large numbers of fluorescein-o-acrylate grown directly on a nanoparticle surface, a convenient “aptamer/protein/aptamer-polymer” supersandwich sensor was fabricated. Under optimal conditions, IFN-γ can be assayed with detection limit down to 0.178 fM in PBS buffer (equals to 1.072 ˣ103 IFN-γ molecules). Even in complex human serum, IFN-γ can also be detected with the limit of 1.54 fM, equals to 9.275 ˣ103 IFN-γ molecules. Results show a great potential in real ultrasensitive protein detection for its high selectivity, efficiency and stability. Besides, this proposed sensing method, which combines the advantages of superparamagnetic nanomaterial and chemically catalyzed surface-initiated dual ATRP polymerization, compared to the traditional signal amplify methods, is novel, more convenient, simpler and enzyme-free cascade amplification.