A method for synthesizing copper nanoclusters based on protein–polyacrylamide gel and its application

Copper nanoclusters (NCs) are increasingly favored by many researchers in the field of biochemistry. In this study, we have provided a method for the preparation of copper NCs based on a protein “turn-on” method, i.e. by immobilizing low-emissive copper nanoparticles (NPs) and proteins [human serum albumin (HSA), catalase, and lysozyme] together in polyacrylamide gel, high-fluorescent copper NCs can be achieved easily. The fluorescent color of HSA-mediated copper NCs is blue purple, the one of catalase-mediated copper NCs is pink yellow, and that of lysozyme-mediated copper NCs is orange red. The results show that the pore size of polyacrylamide gel, the ratio of protein to copper NPs and the modifiers of copper NPs have crucial effects on the yield of copper NCs. This method can also be used for the detection of the corresponding proteins, i.e. HSA, catalase, and lysozyme, based on the fluorescence of their respective copper NCs. The detection limits for the three proteins are all 0.02 mg mL−1, with a linear dynamic range from 0.02 to 2.00 mg mL−1 (HSA), 0.02 to 1.00 mg mL−1 (catalase), and 0.02 to 1.00 mg mL−1 (lysozyme). This method is simple and of low cost, which can be used for the identification of three proteins easily via a “turn-on” mode, which may have potential in biochemical analytical field for the detection of proteins or even more complex substances.