Cell Interactions with Size-Controlled Colloidal Monolayers: Toward Improved Coatings in Bone Tissue Engineering.

The surface structure of biomaterials is of key importance to control its interactions with biological environments. Industrial fabrication and coating processes often introduce particulate nanostructures at implant surfaces. Understanding the cellular interaction with particle-based surface topologies and feature sizes in the colloidal length scale therefore offers the possibility to improve the biological response of synthetic biomaterials. Here, surfaces with controlled topography and regular feature sizes covering the relevant length scale of particulate coatings (100-1000 nm) are fabricated by colloidal templating. Using fluorescent microscopy, WST assay, and morphology analysis, results show that adhesion and attachment of bone-marrow derived murine stromal cells (ST2) are strongly influenced by the surface feature size while geometric details play an insignificant role. Quantitative analysis shows enhanced cell adhesion, spreading, viability, and activity when surface feature size decreases below 200 nm compared to flat surfaces, while larger feature sizes are detrimental to cell adhesion. Kinetic studies reveal that most cells on surfaces with larger features lose contact with the substrate over time. This study identifies colloidal templating as a simple method for creating highly defined model systems to investigate complex cell functions and provides design criteria for the choice of particulate coatings on commercial implant materials.