Influence of thickness, homogeneity, and morphology of TiO2-m nanoparticle coatings on cancer cell adhesion

In the last decades great advances have been made in the photodynamic therapy (PDT) of different types of cancer using TiO2 nanoparticles. However, while most of these have been applied on adherent cancer cells, few reports show the application of PDT to non-adherent cancers such as leukemia, due to inherent challenges related to the selective targeting and irradiation of non-adherent cancer cells. As a possible solution for this issue, coatings based on modified TiO2 (TiO2-m) nanoparticles have been shown to exhibit remarkable selectivity for trapping non-adherent cancer cells without additional binding agents such as aptamers or antibodies. To elucidate the influence of deposition conditions and film morphology on cell adhesion, we have coated glass slides with TiO2 -m nanoparticles by dip coating according to a 2(2) factorial experimental design. The physicochemical surface properties of the TiO2-m nanoparticle coatings were characterized for different deposition conditions and correlated with their performance in trapping leukemic cells. Surface statistical parameters such as root-mean-square (RMS) surface roughness, roughness factor, and height distribution were determined by atomic force microscopy, while coating thickness and homogeneity were assessed by UV transmittance and Raman spectroscopy, respectively. The biological tests showed that the adhesion of leukemic cells on the TiO2-m nanoparticle coating depends on multiple parameters with layer homogeneity and the higher-order surface morphological parameters skewness (Ssk) and excess kurtosis (Sks) playing particularly important roles. By maximizing layer homogeneity and minimizing both Ssk and Sks, we were able to obtain a more than threefold increase in the cell adhesion factor after 24 h incubation.