Detection of transferrin by using a surface plasmon resonance sensor functionalized with a boronic acid monolayer

A surface plasmon resonance sensor whose surface has been modified with boronic acid groups was developed in order to bind and detect transferrin. 4-Mercaptophenylboronic acid (4-MPBA) was utilized to form a self-assembled monolayer on the gold surface of the sensor chip. The surface topography of the modified gold chip was characterized by atomic force microscopy. In solutions of pH 9, the glycosyl groups of transferrin (Trf) quickly and reversibly combine with 4-MPBA on the sensor chip to result in changes of the refractive index. Thus, Trf can be sensed online by monitoring the SPR signal. Under optimized conditions, the sensor has a linear response in the 10 nM to 1.3 μM Trf concentration range, and the limit of detection is 4.4 nM (equivalent to 0.34 μg·mL−1). The results suggest that this 4-MPBA-functionalized sensor is a viable candidate for clinical testing of Trf which is a potential marker for severe diseases such as hypertension, primary renal disease, and diabetes.