The novel conductive polyaniline/bacterial cellulose (PANI/BC) nanocomposite membranes have been synthesized in situ by oxidative polymerization of aniline with ammonium persulfate as an oxidant and BC as a template. The resulting PANI-coated BC nanofibrils formed a uniform and flexible membrane. It was found that the PANI nanoparticles deposited on the surface of BC connected to form a continuous nanosheath by taking along the BC template, which greatly increases the thermal stability of BC. The content of PANI and the electrical conductivity of composites increased with increasing reaction time from 30 to 90 min, while the conductivity decreased because of the aggregation of PANI particles by further prolonging the reaction time. In addition, the acids remarkably improve the accessibility and reactivity of the hydroxyl groups of BC. The results indicate that the composites exhibit excellent electrical conductivity (the highest value was 5.0 × 10(-2) S/cm) and good mechanical properties (Young's modulus was 5.6 GPa and tensile strength was 95.7 MPa). Moreover, the electrical conductivity of the membrane is sensitive to the strain. This work provides a straightforward method to prepare flexible films with high conductivity and good mechanical properties, which could be applied in sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of BC materials.

Titanium (Ti) and its alloys have been extensively used as implant materials in orthopedic applications. Nevertheless, implants may fail due to a lack of osseointegration and/or infection. The aim of this in vitro study was to endow an implant surface with favorable biological properties by the dual modification of surface chemistry and nanostructured topography. The application of a nanostructured titanium dioxide (TiO 2 ) coating on Ti-based implants has been proposed as a potential way to enhance tissue-implant interactions while inhibiting bacterial colonization simultaneously due to its chemical stability, biocompatibility, and antimicrobial properties. In this paper, temperature-controlled atomic layer deposition (ALD) was introduced for the first time to provide unique nanostructured TiO 2 coatings on Ti substrates. The effect of nano-TiO 2 coatings with different morphology and structure on human osteoblast and fibroblast functions and bacterial activities was investigated. In vitro results indicated that the TiO 2 coating stimulated osteoblast adhesion and proliferation while suppressing fibroblast adhesion and proliferation compared to uncoated materials. In addition, the introduction of nano-TiO 2 coatings was shown to inhibit gram-positive bacteria ( Staphylococcus aureus ), gram-negative bacteria ( Escherichia coli ), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus ), all without resorting to the use of antibiotics. Our results suggest that the increase in nanoscale roughness and greater surface hydrophilicity (surface energy) together could contribute to increased protein adsorption selectively, which may affect the cellular and bacterial activities. It was found that ALD-grown TiO 2 -coated samples with a moderate surface energy at 38.79 mJ/m 2 showed relatively promising antibacterial properties and desirable cellular functions. The ALD technique provides a novel and effective strategy to produce TiO 2 coatings with delicate control of surface nanotopography and surface energy to enhance the interfacial biocompatibility and mitigate bacterial infection, and could potentially be used for improving numerous orthopedic implants.

Catheter-associated infections, most of which are caused by microbial biofilms, are still a serious issue in healthcare and are associated with significant morbidity, mortality, and excessive medical costs. Currently, the use of nanostructured materials, especially materials with nanofeatured topographies, which have more surface area, altered surface energy, enhanced select protein adsorption, and selectively increased desirable cell functions while simultaneously decreasing competitive cell functions, seem to be among the most promising ways for reducing initial bacteria attachment, biofilm formation, and infections. In this study, polydimethylsiloxane (PDMS), a commonly used polymeric catheter material, was formulated to mimic the nanopatterned topography of natural tissue by using a template method with nanotubular anodized titanium. Results showed that increased PDMS surface nanoscale roughness alone can inhibit both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria adhesion and growth for up to 2 days, the time length of the current study. Additionally, increased fibroblast and endothelial cell adhesion on nano-PDMS indicated that this nanoscale topography had no toxic effects toward mammalian cells. Mechanistically, this study also developed a model for the first time to correlate bacteria responses to nanoscale roughness with initial protein and biomolecule adsorption (specifically, casein protein and glucose, which are unique biomolecules that mediate bacteria functions). Data revealed that the increase in nanoscale roughness and associated energy contributed to greater select casein adsorption during the first several minutes of culture, which is critical for decreasing bacteria attachment and growth. In contrast, no significant differences for glucose adsorption between samples before and after nanofabrication were identified. These results together indicated that the present biomimetic nanopatterned PDMS surface without any chemical or antibiotic modification has the potential to combat catheter-associated infections and should be further investigated.

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