Effect of pH and addition of salt on the adsorption behavior of lysozyme on gold, silica, and titania surfaces observed by quartz crystal microbalance with dissipation monitoring.

The adsorption behaviors of lysozyme on dentally related Au, SiO2, and TiO2 surfaces were investigated by a quartz crystal microbalance with dissipation monitoring (QCM-D) method. Frequency shifts indicated that while lysozyme (pI 11) was fairly adsorbed on the SiO2 (pI 1.9) surface at both pH 3 and 7, it was adsorbed on TiO2 (pI 6.3) surface only at pH 7. However, adsorption was disturbed by 50 mM NaCl. These results strongly suggested an electrostatic nature of the adsorption behavior. Though a large-scale adsorption of the lysozyme on Au sensor was pH-insensitive, softness of the adlayer as seen from the dissipation profile was pH-dependent, indicating an interaction of another type. With all the surfaces, the small dissipation change indicated a stiff lysozyme adlayer. Results of this study revealed that the controlled electrostatic interaction between the material surface and lysozyme might be a useful method for imparting antibacterial property to the dental materials.