Immunoglobulin-Immobilized Quartz Crystal Microbalance for Staphylococcus Aureus Real-Time Detection

Quartz crystal microbalance (QCM) sensor is still a high-precision surface sensing technique. Here, we described an immunoglobulin G (IgG) biofunctionalized QCM sensor for
Staphylococcus aureus
(S. aureus) sensing application. In the case of the QCM sensor, a gold-titanium (Au/Ti) electrode layer was fabricated by magnetron sputtering and sequentially immobilized with thoil self-assembled monolayer (SAM) and IgG gripper. The selectivity test showed that the rabbit IgG-based QCM sensor exhibited a good sensitivity performance. IgG immobilization optimal experiment was conducted by adjusting parameters including immobilization time, temperature, buffer pH and IgG concentration. The lower limit of detection and sensitivity of the IgG-based QCM biosensor toward
S. aureus
were suggested to be
$1.0\times {10}^{{4}}$
CFU/mL and 562.5 Hz/ng, respectively. Furthermore, the real-time monitoring and frequency response of IgG immobilization process and its sensitive adsorption behavior to
S. aureus
were performed in droplet environment. By comparison, the average sensitivity of IgG-immobilized QCM sensor in liquid phase is 2-3.5 times higher than that in air. Overall, it is indicative that IgG-based QCM sensors do have great potential for biological monitoring applications.