VOLUME 3, NUMBER 5, MAY 2003 © Copyright 2003 by the American Chemical Society
Biomimicry Patterning with Nanosphere Suspensions Andrei P. Sommer* and Ralf-Peter Franke Department of Biomaterials/ENSOMA-Laboratory, Central Institute of Biomedical Engineering, UniVersity of Ulm, 89081 Ulm, Germany Received October 3, 2002; Revised Manuscript Received October 22, 2002
ABSTRACT Experiments designed to mimic cell receptor structures on biomaterial surfaces showed that slow evaporation of water-based suspensions containing polystyrene nanospheres created translucent nanostructured films enclosed by highly regular ring shaped patterns. Our finding represents a novel method to functionalize biomaterial surfaces by structurizing both the micro- and nanoscale topography in one single process, answering practically the complete scale of biological demands required for a better integration of biomaterials into the targeted site of the body.
It has been shown that the attachment of cells to biomaterials is largely determined by the micro- and nanoscale structures of the surfaces.1 Suitable microscale profiles appear to facilitate a better adjustment of the cell body to biomaterial surfaces; additional nanoscale structures seem to play an important role in mimicking the lacking extracellular matrix in the interaction with cell receptors. In the experimental section we analyze deposition patterns formed by evaporation of 10 µL droplets of a water based nanosphere suspension on different materials: titanium, stainless steel, silicone (wafer quality), glass, and polystyrene (Petri dishes). With diameters of 60 ( 2.5 nm, the size of the nanospheres (Duke Scientific) was adjusted to the dimension of the space separating the abluminal cell membrane of epi-/endothelial cells from the organized layer of the adjacent basal membrane. The observed deposition patterns depended on three physicochemical parameters: the interfacial tension between * Corresponding author. 10.1021/nl0258269 CCC: $25.00 Published on Web 11/05/2002
© 2003 American Chemical Society
droplet and substrate, the speed of evaporation, and most importantly the surface roughness of the substrate. The material with the highest interfacial tension relative to the droplet was titanium - an excellent biocompatible material. Evaporation of 10 µL droplets of the nanospheres suspension on polished titanium disks resulted in circularly shaped deposition patterns (Figure 1a). The titanium disks, similar to the reflecting substrates employed for optical contrast enhancement in near-field optical analysis (NOA), were mechanochemically polished and had a total surface roughness
