Cytosensing and evaluation of cell surface glycoprotein based on a biocompatible poly(diallydimethylammonium) doped...

In this paper, we constructed an interface that not only retains viability of immobilized BGC823 human gastric carcinoma cells (BGC823 cells) but also efficiently resists nonspecific adsorption of the P-glycoprotein antibody and its secondary antibody, which enabled us to sensitively detect the number of cells and P-glycoproteins on the BGC823 cell surface by the immunoassay method. Preparation of the film was quite simple and inexpensive just by spin-coating poly(dimethylsiloxane) (PDMS) doped with poly(diallydimethylammonium) (PDDA) on the surface of gold electrodes. The composite film's biocompatibility, antinonspecific adsorption ability, and the conductivity for electrochemical probe ([Fe(CN)6]3-/4-) were proved by cell culture experiments, blocking experiments, and electrochemical experiments. Compared with PDMS and PDMS doped with poly(sodium 4-styrenesulfonate) (PSS), the PDMS-PDDA composite film showed a predominant ability to capture cells due to electrostatic reaction between the presence of positively charged PDDA and the negatively charged glycocalyx on the surface of cells. On the advantage of electrochemical immunoassay with a signal amplification path by using biocatalytic precipitation of an insoluble product, differential pulse voltammetry (DPV) measurement based on the changes of electron-transfer resistance was introduced to detect the cell amount and monitor growing states of cells like adhesion, spread, proliferation, and apoptosis on the electrodes. Optimally, signal response was proportional to the logarithm of cell concentration ranging from 1.0 x 10(3) to 5.0 x 10(7) cells mL(-1) with a detection limit of 7.2 x 10(2) cells mL(-1). On the basis of the special property for resisting nonspecific adsorption of this composite film, an ultraviolet and visible (UV-vis) absorption spectrum with one-step immunoreaction was employed to evaluate the P-glycoprotein on the BGC823 cell surface. The P-glycoprotein on a single living intact BGC823 cell was detected correspondingly to 4.7 x 10(7) molecules. The work implied that the composite film possessed potential applications for biosensing and convenient evaluation of surface glycoprotein on living cells.