TiO2–Based Nanofibrous Membranes for Environmental Protection

Electrospinning is a unique technique that can be used to synthesize polymer and metal oxide nanofibers. In materials science, a very active field is represented by research on electrospun nanofibers. Fibrous membranes present fascinating features, such as a large surface area to volume ratio, excellent mechanical behavior, and a large surface area, which have many applications. Numerous techniques are available for the nanofiber’s synthesis, but electrospinning is presented as a simple process that allows one to obtain porous membranes containing smooth non-woven nanofibers. Titanium dioxide (TiO2) is the most widely used catalyst in photocatalytic degradation processes, it has advantages such as good photocatalytic activity, excellent chemical stability, low cost and non-toxicity. Thus, titanium dioxide (TiO2) is used in the synthesis of nanofibrous membranes that benefit experimental research by easy recyclability, excellent photocatalytic activity, high specific surface areas, and exhibiting stable hierarchical nanostructures. This article presents the synthesis of fiber membranes through the processes of electrospinning, coaxial electrospinning, electrospinning and electrospraying or electrospinning and precipitation. In addition to the synthesis of membranes, the recent progress of researchers emphasizing the efficiency of nanofiber photocatalytic membranes in removing pollutants from wastewater is also presented.

Optimization of spark plasma sintered titania for potential application as a keratoprosthesis skirt

The manufacture of mechanically strong and biocompatible titania (TiO₂ ) materials is of vital importance for their application as corneal implant skirts. This study was aimed at optimizing the selection of raw powder and sintering conditions for TiO₂ ceramics. TiO₂ compacts were synthesized from five raw powders, denoted as Altair, Inframat, Alfa, Materion, and Amperit, respectively, by spark plasma sintering using different sintering parameters. The XRD and Raman results confirmed that the anatase TiO₂ phase in the Inframat powder had converted completely to rutile TiO₂ phase after sintering at 900°C and above. The nanoindentation results indicated that among the five types of TiO₂ samples sintered at 1100°C, the Inframat pellets possessed the highest Young's modulus and hardness. Additionally, when Materion samples were employed to study the effects of SPS parameters, a higher sintering temperature in the range of 1100-1300°C decreased the mechanical properties of sintered pellets probably due to the generation of more structural defects. Culture of human corneal stromal fibroblasts on the sintered sample surfaces showed that comparably high cell viability and proliferation were observed on all TiO₂ samples except Amperit compared to positive control. Furthermore, cells cultured on Inframat TiO₂ sintered in the temperature range of 900-1300°C exhibited viability and formation of focal adhesion complex similar to those on control, and those prepared at 1100°C had significantly higher cell proliferation indices than control. In conclusion, Inframat TiO₂ consolidated at 1100°C by SPS was the best formulation for the preparation of mechanically strong and biocompatible Keratoprosthesis skirt. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3502-3513, 2017.

Synthesis and characterization of biocompatible antimicrobial N-halamine-functionalized titanium dioxide core-shell nanoparticles

As one of the most powerful biocides, N-halamine based antimicrobial materials have attracted much interest due to their non-toxicity, rechargeability, and rapid inactivation against a broad range of microorganisms. In this study, novel titanium dioxide-ADMH core-shell nanoparticles [TiO₂@poly (ADMH-co-MMA) NPs] were prepared via miniemulsion polymerization using 3-allyl-5,5-dimethylhydantoin (ADMH) and methyl methacrylate (MMA) with nano-TiO₂. The produced nanoparticles were characterized by FT-IR, TEM, TGA, and XPS. The UV stability of N-halamine nanoparticles has been improved with the addition of titanium dioxide. After chlorination treatment by sodium hypochlorite, biocidal efficacies of the chlorinated nanoparticles against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) were determined. The nanoparticles showed excellent antimicrobial properties against bacteria within brief contact time. In addition, in vitro cell cytocompatibility tests showed that the antibacterial nanoparticles had good biocompatibility.

Antibacterial activity and interaction mechanism of electrospun zinc-doped titania nanofibers

In this study, a biological evaluation of the antimicrobial activity of Zn-doped titania nanofibers was carried out using Escherichia coli ATCC 52922 (Gram negative) and Staphylococcus aureus ATCC 29231 (Gram positive) as model organisms. The utilized Zn-doped titania nanofibers were prepared by the electrospinning of a sol-gel composed of zinc nitrate, titanium isopropoxide, and polyvinyl acetate; the obtained electrospun nanofibers were vacuum dried at 80°C and then calcined at 600°C. The physicochemical properties of the synthesized nanofibers were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis, thermogravimetry, and transmission electron microscopy (TEM). The antibacterial activity and the acting mechanism of Zn-doped titania nanofibers against bacteria were investigated by calculation of minimum inhibitory concentration and analyzing the morphology of the bacterial cells following the treatment with nanofibers solution. Our investigations reveal that the lowest concentration of Zn-doped titania nanofibers solution inhibiting the growth of S. aureus ATCC 29231 and E. coli ATCC 52922 strains is found to be 0.4 and 1.6 μg/ml, respectively. Furthermore, Bio-TEM analysis demonstrated that the exposure of the selected microbial strains to the nanofibers led to disruption of the cell membranes and leakage of the cytoplasm. In conclusion, the combined results suggested doping promotes antimicrobial effect; synthesized nanofibers possess a very large surface-to-volume ratio and may damage the structure of the bacterial cell membrane, as well as depress the activity of the membranous enzymes which cause bacteria to die in due course.

Nitrogen-doped TiO2 thin films: photocatalytic applications for healthcare environments

N-doped TiO(2) has for many years received interest as visible light photocatalytic materials. Here we give our perspective on the subject with special consideration towards the use of visible light photocatalysts in the field of antimicrobial materials with applications in healthcare environments. The subject is reviewed and critiqued from synthetic techniques to characterisation and assessment of functional properties. N-doped TiO(2) has huge potential to form commercially viable antimicrobial surfaces that are easily implemented within the healthcare environment. We aim to shed light on the illusive nature of the mechanism of the different types of N-doping and comment on how these affect the properties of the catalysts themselves. Small concentrations of nitrogen doped under mild conditions lead to interstitial doping, which also promotes the creation of oxygen vacancies. Many believe that it is these oxygen vacancies that actually promote the formation of visible light photocatalysis and hence there is an indirect correlation between the interstitial doping and the photocatalysis. As the concentration of interstitial nitrogen increases the oxygen vacancies increase, however the presence of oxygen vacancies in turn encourages substitutional doping which then fills the oxygen vacancies. This cyclic relationship leads to photocatalysts that are very sensitive to changing nitrogen concentration.

Photocatalytic antibacterial capabilities of TiO(2)-biocidal polymer nanocomposites synthesized by a surface-initiated photopolymerization

Novel biocidal polymer-functionalized TiO(2) nanoparticles were prepared by surface-initiated photopolymerization using titania as an initiator. Vinyl monomer mixtures of nontoxic secondary amine-containing biocidal 2-(tert-butylamino)ethyl methacrylate and antifouling ethylene glycol dimethacrylate were used for the antimicrobial polymer shell. It was shown that the synthesized TiO(2)/poly[2-(tert-butylamino)ethyl methacrylate-co-ethylene glycol dimethacrylate] core/shell nanoparticles had enhanced photocatalytic antibacterial properties compared to the pristine TiO(2) nanoparticles due to the combined antibacterial activities of light-driven anti-infective TiO(2) core and biocidal polymer shell. In the dark condition, the TiO(2)/biocidal polymer nanoparticles exhibited high antimicrobial efficiency (95.7%) against gram-positive S. aureus. Furthermore, during UV irradiation, the TiO(2)/biocidal polymer showed improved inhibition of bacterial growth against gram-negative E. coli and gram-positive S. aureus in comparison to the pristine TiO(2) nanoparticles.