Real time monitoring of the effects of Heparan Sulfate Proteoglycan (HSPG) and surface charge on the cell adhesion process using thickness shear mode (TSM) sensor

Abstract

The effects of Heparan Sulfate Proteoglycan (HSPG) and surface charge on the cellular interactions of the cell membrane with different substrates to determine the kinetics of cell adhesion was studied using thickness shear mode (TSM) sensor. The TSM sensor was operated at its first, third, fifth and seventh harmonics. Since the penetration depth of the shear wave decreases with increases in frequency, the multi-resonance operation of the TSM sensor was used to monitor the changes in the kinetics of the cell–substrate interaction at different distances from the sensor surface. During the sedimentation and the initial attachment of the cells on the sensor surface, the changes in the sensor resonant frequency and the magnitude response were monitored. First, HSPGs were partially digested with the enzyme Heparinase III to evaluate the effect of HSPG on the cell adhesion process. The results indicated that HSPG did not have any effect on the kinetics of the initial attachment, but it did reduce the strength of steady-state cell adhesion. Next, we investigated the effect of the electrostatic interactions of the cell membrane with the substrate on the cell adhesion. In this case, the sensor surface was coated with positively charged Poly- d-Lysine (PDL). It was observed that electrostatic interaction of the negatively charged cell membrane with the PDL surface promoted the initial cell adhesion but did not support long-term cell adhesion. The multi-resonant TSM technique was shown to be a very promising method for monitoring specific interfacial effects involving in cell adhesion process in real-time.