Physicochemical properties of (ethylene glycol)-containing self-assembled monolayers relevant for protein and algal...

The influence of the number of repeating units in self-assembled monolayers (SAMs) of ethylene glycol and of their end-group termination on the settlement and adhesion of two types of algal cells, viz., zoospores of the macroalga Ulva and cells of the diatom Navicula , was studied. The findings are related to the resistance of these surfaces against fibrinogen adsorption. Results showed that settlement and adhesion of algal cells to oligo(ethylene glycol) (OEG; 2-6 EG units) and poly(ethylene glycol) (PEG; MW = 2000, 5000) SAMs was low, while resistance was less effective for mono(ethylene glycol) (EG(1)OH)-terminated surfaces. These findings concur with former protein adsorption studies. In situ microscopy showed that PEG surfaces inhibited the settlement of zoospores, i.e., zoospores did not attach to the surfaces and remained motile. In contrast, on EG(2-6)OH surfaces, although zoospores settled, i.e., they secreted adhesive and lost motility, adhesion between secreted adhesive and the surface was extremely weak, and the settled spores were unable to bond to the surfaces. The influence of surface properties such as hydration, conformational degrees of freedom, and interfacial characteristics of the SAMs is discussed to understand the underlying repulsive mechanisms occurring in (ethylene glycol)-based coatings.