Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically

Beatrix Peter,Szilvia Bosze,Inna Szekacs,Robert Horvath,Andras Saftics,Sandor Kurunczi,Eniko Farkas,Boglarka Kovacs,Eniko Forgacs,Antal Csampai

doi:10.1038/srep42220

Abstract

The interaction of the anti-adhesive coating, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its Arg-Gly-Asp (RGD) functionalized form, PLL-g-PEG-RGD, with the green tea polyphenol, epigallocatechin-gallate (EGCg) was in situ monitored. After, the kinetics of cellular adhesion on the EGCg exposed coatings were recorded in real-time. The employed plate-based waveguide biosensor is applicable to monitor small molecule binding and sensitive to sub-nanometer scale changes in cell membrane position and cell mass distribution; while detecting the signals of thousands of adhering cells. The combination of this remarkable sensitivity and throughput opens up new avenues in testing complicated models of cell-surface interactions. The systematic studies revealed that, despite the reported excellent antifouling properties of the coatings, EGCg strongly interacted with them, and affected their cell adhesivity in a concentration dependent manner. Moreover, the differences between the effects of the fresh and oxidized EGCg solutions were first demonstrated. Using a semiempirical quantumchemical method we showed that EGCg binds to the PEG chains of PLL-g-PEG-RGD and effectively blocks the RGD sites by hydrogen bonds. The calculations supported the experimental finding that the binding is stronger for the oxidative products. Our work lead to a new model of polyphenol action on cell adhesion ligand accessibility and matrix rigidity.

Highlights

Markers that may affect normal cell behavior and the imaging time is often limited by the bleaching of the marker
Increased cell spreading was observed on the PPR surfaces with the higher RGD density and the authors argued for reduced differentiation of osteoblasts to an extent conducive to proliferation rather than stimulating differentiation
An important novelty of this study is that the polymer coating fabrication, its treating with small molecule, and the observation of cell adhesion could be all studied on-line by the Epic BT label-free biosensor in triplicates, and with different EGCg and oxidized EGCg concentrations

Summary

Introduction

Markers that may affect normal cell behavior and the imaging time is often limited by the bleaching of the marker. While quartz crystal microbalance (QCM)[4,6,13], cellular dielectric spectroscopy (CDS)[14,15], optical waveguide lightmode spectroscopy (OWLS)[16], surface plasmon resonance (SPR)[7] usually employ one or a low number of sensing units, novel biosensors have high-throughput capability to practically parallel measurements of hundreds of samples in a microplate format At present, they meet the required sensitivity of being able to detect the binding of ligands of molecular mass as low as 100–200 Da, below 5 pg/mm[2] surface mass density; and their current throughput allows up to 460,000 data points/hour. The calculations illuminated the differences in binding affinity between the fresh and oxidized EGCg, well supporting the experimental findings

Methods

Results

Conclusion