Total Protein Determination by Recovery Fluorescence of Trinitrotoluene-Quenched Protein-Functionalized Gold Nanoclusters.

Determination of total protein content is very important for clinical, pharmaceutical and food chemistry, and the simplicity and rapidity of the existing total protein content assays should be improved. Here, a novel fluorescent sensor for total protein content measurement was described using near-infrared emitting fluorescent gold nanoclusters, which were prepared with egg whites. Trinitrotoluene served as highly efficient quencher to quench the fluorescence of gold nanoclusters. Interestingly, the trinitrotoluene-protein complex that formed by premixing of trinitrotoluene and protein-containing real samples maintained the fluorescence of gold nanoclusters. These new findings provided a novel mechanism to design a fluorescence sensor for determination of total protein levels in various real samples. With available and low-cost bovine serum albumin as reference, the obtained standard curve for total protein determination indicated a linear range of 0.1-3.5 g L with a detection limit of 0.06 g L (3σ rule) and a correlation efficiency (R) of 0.9850. The applicability of the proposed sensor was validated by determination of total protein levels in real samples. Comparison with the existing spectrophotometric methods, the proposed sensor is advantageous of simplicity, rapidity, and cost-effectiveness.