Anti-fouling nano-Ag/SiO2 ormosil treatments for building materials: The role of cell-surface interactions on toxicity and bioreceptivity

Protective coatings with hydrophobic or biocide properties are commonly employed to prevent biofouling of building materials exposed to the environment. Although the factors affecting bioreceptivity of the base materials are well known, the influence of the coating and/or biocide agent surface properties on the interaction with the cell surface is often overlooked. As such, a proper understanding of these interfacial interactions can help improve their anti-fouling effectiveness. This work studies a multifunctional superhydrophobic/biocide treatment, containing surface engineered Ag/SiO2 nanoparticles embedded in an organically modified silica matrix, focusing on determining the effect of the cell-nanoparticle interactions and surface properties on its effectiveness against algal fouling. The modification of SiO2 with positively charged groups increased the interaction of the biocide with the cell walls through electrostatic forces, while at the same time it promotes cell aggregation. The hydrophobic matrix decreases initial colonization due to its lower roughness and water absorption, although surface free energy measurements indicated an increase of the cell-surface adhesion force as polarity of the cell wall decreased. A Cassie-Baxter wetting regime on the superhydrophobic surfaces decreased effective contact area and adhesion force, though this state was quickly lost under exposure to the cultures