Total Protein Determination by Recovery Fluorescence of Trinitrotoluene-Quenched protein-functionalized Gold Nanoclusters

Abstract

Determination of total protein content is very important for clinical, pharmaceutical and food chemistry, and the selectivity and accuracy of the existing total protein assays should be improved. Here, a novel fluorescent sensor for total protein assay is described using near-infrared emitting fluorescent gold nanoclusters (Au NCs) prepared with egg white. Trinitrotoluene (TNT) serves as highly efficient quencher to quench the Au NCs fluorescence. Interestingly, the TNT-protein complex formed by premixing of TNT and protein-containing real samples can maintain the Au NCs fluorescence. These interesting findings provide a novel mechanism to design a fluorescence sensor to determine total protein levels in various real samples (commercial sera and food milk). With available and low-cost bovine serum albumin (BSA) serves as reference, the obtained standard curve for total protein determination indicates a linear range of 0.1 – 3.5 g L−1 with a detection limit of 0.06 g L−1 (3σ rule) and a correlation efficiency (R2) of 0.9850. The good performance and applicability of the proposed sensor are validated by comparison with which of the biuret assay. Comparison with the existing spectrophotometric methods, the proposed method is advantageous of simplicity, rapidity, cost-effectiveness and improved sensitivity and accuracy.