Quartz crystal microbalance (QCM) has been extensively applied in real-time and label-free biomolecular interaction studies. However, the sensitive detection by QCM technology remains challenging, mainly due to the limited surface immobilization capacity. Here, a three-dimensional (3D) carboxymethyl dextran coated gold sensor chip surface was successfully fabricated with dextran of different molecular weight (100, 500 and 2000 kDa, respectively). To evaluate the 3D carboxymethyl dextran surface immobilization capacity, the 3D surface was used for studying antigen–antibody interactions on the QCM biosensor. The results showed that the protein immobilization capacity of the 3D carboxymethyl dextran (2000 kDa) surface exceeded more than 4 times the capacity of the 2D carboxyl surface, and 2 times the capacity of the traditional 3D carboxymethyl dextran (500 kDa) surface. Furthermore, the kinetic and affinity properties of antigen–antibody interactions were performed. Most notably, the optimized 3D carboxymethyl dextran (2000 kDa) surface could be used for small molecule detection, where the binding of biotinylated oligo (0.67 kDa) reached 8.1 Hz. The results confirmed that a 3D carboxymethyl dextran (2000 kDa) surface can be exploited for sensitive detection of low molecular weight analytes, which have great potential applications for characterizing the interactions between small molecule drugs and proteins.

A novel metal-free organobase-catalyzed regioselective benzoylation of diols and carbohydrates has been developed. Treatment of diol and carbohydrate substrates with 1.1 equiv. of 1-benzoylimidazole and 0.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in MeCN under mild conditions resulted in highly regioselective benzoylation for the primary hydroxyl group. Importantly, compared to most commonly used protecting bulky groups for primary hydroxyl groups, the benzoyl protective group offers a new protection strategy.