Quartz crystal microbalance sensor based on 11-mercaptoundecanoic acid self-assembly and amidated nano-titanium film for selective and ultrafast detection of phosphoproteins in food.

A novel quartz crystal microbalance (QCM) sensor for trace-phosphoprotein ultrafast detection was constructed based on the bridge interactions between the NH2-TiO2 sites enriched on Au-electrode and phosphate groups. Herein, 11-mercaptoundecanoic acid (MUA) modified by Au-S bond acted as carrier for immobilizing NH2-TiO2. Functionalized NH2-TiO2 to absorb phosphoproteins. Under the optimal conditions, the proposed sensor showed a linear frequency shift to the concentration of α-casein ranging from 1.0 × 10-3 to 1.0 mg mL-1 with a low detection limit of 5.3 × 10-6 mg mL-1 (S/N = 3), and the limit of quantitation was 0.001 mg mL-1. Compared with traditional Ti4+-IMAC/MOAC-system, the analysis process of NH2-TiO2/MUA/AuE-QCM sensor was simpler and faster which could complete within 5 min. Additionally, the constructed biosensor was successfully used for the non-fat milk and chicken egg white. This proposed sensor presents a great prospective strategy for the evaluation of the nutrition in different foods.