Electrochemically prepared poly(L-lysine) and 3-hydroxyphenylboronic acid composite as a conventional adhesion material for rice suspension cells

Poly(L-lysine) (PLL)-3-hydroxyphenylboronic acid (3-PBA) composite was prepared onto an Au electrode via cyclic voltammetry (CV), which was characterized by electrochemical and quartz crystal microbalance (QCM) techniques, and used to promote adhesion of plant cells. 3-PBA can interact with glycosyl compounds on the cell wall to form negatively charged covalent compounds while PLL increases the number of positively charged sites, which enhances the electrostatic interactions with the negatively charged cell wall, both promoting cell adhesion. The PLL-poly(3-PBA) composite was successfully modified on the Au electrode surface, as demonstrated by QCM and Fourier transform infrared spectrophotometry (FTIR). Moreover, we confirmed the synergistic effect of PLL and 3-PBA to adhere rice suspension cells using CV, electrochemical impedance spectroscopy (EIS), QCM and optical microscope observations. Finally, the dynamic process of rice cells' adhesion to PLL-poly(3-PBA)/Au followed by salt stress treatment of NaCl was monitored in real-time by QCM. The cells softened at first then hardened under the action of 40 mM NaCl. This work presents a novel and conventional way to immobilize plant cells onto sensors, and has importance in the study of the structure, function and behavior of plants under various stresses at the cellular level.