An increased use of antibiotic drugs has led to the development of numerous multi-resistant microbes in the last years. Due to this medical situation the treatment of biomaterials-associated infections (BAI) with antibiotics is critically discussed. Therefore, a reduced adhesion of microorganisms on biomaterials surfaces is of high interest for preventing BAI. One strategy is the modification of the topographical characteristics of biomaterials surfaces. We immobilized nanoparticles (Ø 15 nm diameter) in order to nanostructure biomaterials surfaces. The aims of the study were [i] to investigate microbial adhesion on biomaterials surfaces nanostructured with nanoparticles and [ii] to identify and understand the physical mechanisms of microbial adhesion on the nanostructured surfaces.
For reproducible fabrication of gold surfaces physical vapor deposition (PVD) was used. Different concentrations of COOH-functionalized gold nanoparticles were immobilized on polyethylenimin-functionalized gold surfaces. The surfaces were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy and contact angle measurements. Escherichia coli cells adhesion to the modified gold surfaces and to the unstructured control surface was measured by confocal laser scanning microscope after 3 h, 6 h and 9 h. For investigation of the material-microbe interfaces, a SEM equipped with a focused ion beam was used.
RESULTS AND DISCUSSION
AFM images indicate the successful immobilization of gold nanoparticles with different concentrations on the activated gold surfaces. After 6 h and 9 h of adhesion, a statistically significantly reduced surface coverage on the nanostructured gold surfaces compared to the unstructured control surface was observed. With decreasing the amount of immobilized nanoparticles the microbial adhesion was reduced. The material-microbe interface indicated that the contact points given by the nanoparticles mediate the initial contact between the microbial cell and the surface. With a reduced amount of immobilized nanoparticles the number of contact points decreases resulting in less microbial adhesion.
Our study deepen the knowledge about the mechanisms of interactions between bacterial cells and nanostructured biomaterials surfaces. The modification of biomaterials surfaces with nanoparticles is, therefore, a promising antibiotic-free strategy for reducing BAI.