An ultrasensitive electrochemiluminescence immunosensor based on platinum nickel nanocubes-L-cysteine-luminol nanocomposite

An ultrasensitive electrochemiluminescence (ECL) immunosensor was initially developed for quantitative detection of carbohydrate antigen 15-3 (CA15-3) using platinum nickel nanocubes-L-cysteine-luminol nanocomposite (PtNi NCs-L-Cys-luminol) as signal probe. Herein, the PtNi NCs-L-Cys-luminol nanocomposite was modified on the glassy carbon electrode (GCE) surface via the film-forming properties of chitosan. Then, the CA15-3 antibody was attached to the modified electrode surface by amidating reaction to construct the ECL immunosensor. Experimental results showed that with the capturing of CA15-3 antigen molecules on the immunosensor, the ECL signal intensity observably decreased, indicating the quenching detection principle of electrochemiluminescence. Under optimal experimental conditions, the constructed ECL immunosensor displayed remarkable performance for CA15-3 detection ranging from 0.0005 U/mL to 500 U/mL, with a relatively low detection limit of 0.000167 U/mL (S/N = 3). It might be ascribed to the fact that the PtNi NCs could dramatically promote the decomposition of H2O2 to produce various active free radical, thereby the ECL responses of luminol were prominently magnified and its sensitivity was effectively increased. The immunosensor exemplified its advantages of easy fabrication, fast analysis, high sensitivity, good reproducibility and selectivity. Moreover, the recovery tests exhibited that the sensor can be used to sensitively detect CA15-3 in serum samples, suggesting potential application prospect in bioanalysis.