Synthesis and Microcontact Printing of novel nanoflowers of ZnO_Ag_rGO nanocomposite to check microbial adhesion

Nanocomposites (NCs) have garnered enormous attention lately due to their superior qualities and manipulative flexibility. In the presented work we have synthesized two NCs, binary Zinc Oxide_Reduced Graphene Oxide (ZnO_rGO) and ternary Zinc Oxide_Silver_Reduced Graphene Oxide (ZnO_Ag_rGO), using a simple one-pot hydrothermal method. Transmission Electron Microscopy (TEM) images of these NCs revealed three-dimensional (3D) flower shaped structures, where the petals are formed by ZnO wrapped with flaky layers of GO. Additionally in the latter NC, the petals are decorated with Ag. Two other single nanomaterials were also prepared, namely Silica (Si) nanoparticles (NPs) and GO sheets, where silica was bioconjugated with poly-L-lysine (PLL) and GO was used as a control material. The synthesis of these nanomaterials were followed by fabrication of patterns on a solid support in the micrometer-scale range using microcontact printing (μCP), with the aim to create surfaces with different topologies. PLL functionalized Si particles (Si-PLL) were used as a standard to identify the outcome of the printing process. To check the resultant patterns with increasing complexity of the ink, both the binary (ZnO_rGO) and ternary (ZnO_Ag_rGO) nanocomposites were used. Variations in surface topology corresponding to these materials were assessed using Atomic Force Microscopy (AFM). AFM analysis showed that though all the substrates were patterned employing precisely identical conditions, surface coverage of the materials in the patterns and their height from the surfaces differed in all the cases. Finally, their biological evaluations were performed using Escherichia coli and Candida albicans. The ternary NC (ZnO_Ag_rGO) coated surfaces showed a significant reduction in both bacterial and fungal adhesion. Another interesting observation that was noted was the micropatterned surfaces displayed a dual cumulative physical and chemical effect against both E. coli and C. albicans. Our overall results manifested that simple micron-sized structures, in comparison to fully coated surfaces, showed a declining trend of microbial adhesion. This can serve as a promising alternative to create patterned large surface areas to prevent microbial and fungal advances in medical devices or other materials susceptible to biofilm formation, based on further investigations.