No abstract

The first report on the fabrication and application of a nanocomposite containing poly-N-vinyl carbazole (PVK) polymer and graphene oxide (GO) as an antimicrobial film was demonstrated. The antimicrobial film was 90% more effective in preventing bacterial colonization relative to the unmodified surface. More importantly, the nanocomposite thin film showed higher bacterial toxicity than pure GO-modified surface.

Materials possessing excellent bacterial toxicity, while presenting low cytotoxicity to human cells, are strong candidates for biomaterials applications. In this study, we present the fabrication of a nanocomposite containing poly(N-vinylcarbazole) (PVK) and graphene (G) in solutions and thin films. Highly dispersed PVK-G (97-3 w/w%) solutions in various organic and aqueous solvents were prepared by solution mixing and sonication methods. The thermal properties and morphology of the new composite were analyzed using thermal gravimetry analysis (TGA) and atomic force microscopy (AFM), respectively. PVK-G films were immobilized onto indium tin oxide (ITO) substrates via electrodeposition. AFM was used to characterize the resulting topography of the nanocomposite thin films, while cyclic voltammetry and UV-vis were used to monitor their successful electrodeposition. The antimicrobial properties of the electrodeposited PVK-G films and solution-based PVK-G were investigated against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). Microbial growth after exposure to the nanocomposite, metabolic assay and live-dead assay of the bacterial solutions exposed to PVK-G presented fewer viable and active bacteria than those exposed to pure PVK or pure graphene solutions. The PVK-G film inhibited about 80% of biofilm surface coverage whereas the PVK- and G-modified surfaces allowed biofilm formation over almost the whole coated surface (i.e. > 80%). The biocompatibility of the prepared PVK-G solutions on NIH 3T3 cells was evaluated using the MTS cell proliferation assay. A 24 h exposure of the PVK-G nanocomposite to the NIH 3T3 cells presented ~80% cell survival.

Abstract.Highly porous poly (ε-caprolactone) microfiber scaffolds can be fabricated using electrospinning for tissue engineering applications. Melt electrospinning produces such scaffolds by direct deposition of a polymer melt instead of dissolving the polymer in a solvent as performed during solution electrospinning. The objective of this study was to investigate the significant parameters associated with the melt electrospinning process that influence fiber diameter and scaffold morphology, including processing temperature, collection distance, applied voltage and nozzle size. The mechanical properties of these microfiber scaffolds varied with microfiber diameter. Additionally, the porosity of scaffolds was determined by combining experimental data with mathematical modeling. To test the cytocompatability of these fibrous scaffolds, we seeded neural progenitors derived from murine R1 embryonic stem cell lines onto these scaffolds where they could survive, migrate, and differentiate into neurons, demonstrating the potential of these melt electrospun scaffolds for tissue engineering applications.

The antibacterial properties of a nanocomposite containing an electroactive polymer, polyvinyl-N-carbazole (PVK) (97 wt %), and single-walled carbon nanotubes (SWNT) (3 wt %) was investigated as suspensions in water and as thin film coatings. The toxic effects of four different PVK-SWNT (97:3 wt %) nanocomposite concentrations (1, 0.5, 0.05, and 0.01 mg/mL) containing 0.03, 0.015, 0.0015, and 0.0003 mg/mL of SWNT, respectively, were determined for planktonic cells and biofilms of Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). The results showed that the nanocomposite PVK-SWNT had antibacterial activity on planktonic cells and biofilms at all concentration levels. Higher bacterial inactivation (94% for E. coli and 90% for B. subtilis) were achieved in planktonic cells at a PVK-SWNT concentration of 1 mg/mL. Atomic force microscopy (AFM) imaging showed significant reduction of biofilm growth on PVK-SWNT coated surfaces. This study established for the first time that the improved dispersion of SWNTs in aqueous solutions in the presence of PVK enhances the antimicrobial effects of SWNTs at very low concentrations. Furthermore, PVK-SWNT can be used as an effective thin film coating material to resist biofilm formation.