Various Antibacterial Strategies Utilizing Titanium Dioxide Nanotubes Prepared via Electrochemical Anodization Biofabrication Method

Currently, titanium and its alloys have emerged as the predominant metallic biomaterials for orthopedic implants. Nonetheless, the relatively high post-operative infection rate (2-5%) exacerbates patient discomfort and imposes significant economic costs on society. Hence, urgent measures are needed to enhance the antibacterial properties of titanium and titanium alloy implants. The titanium dioxide nanotube array (TNTA) is gaining increasing attention due to its topographical and photocatalytic antibacterial properties. Moreover, the pores within TNTA serve as excellent carriers for chemical ion doping and drug loading. The fabrication of TNTA on the surface of titanium and its alloys can be achieved through various methods. Studies have demonstrated that the electrochemical anodization method offers numerous significant advantages, such as simplicity, cost-effectiveness, and controllability. This review presents the development process of the electrochemical anodization method and its applications in synthesizing TNTA. Additionally, this article systematically discusses topographical, chemical, drug delivery, and combined antibacterial strategies. It is widely acknowledged that implants should possess a range of favorable biological characteristics. Clearly, addressing multiple needs with a single antibacterial strategy is challenging. Hence, this review proposes systematic research into combined antibacterial strategies to further mitigate post-operative infection risks and enhance implant success rates in the future.

Evaluation of bioactivity and antibacterial properties of Ti6Al4V-based green biocomposite implant encompassing TiO2 nanotube arrays and garlic extract

This study involved the incorporation of an antibacterial garlic extract into titanium oxide nanotubes (TNTs) formed via the anodization of Ti6Al4V implants. The garlic extract, obtained through low-temperature extraction aided by ultrasound waves, was loaded into the nanotubes. The presence of the nanotubes was confirmed through X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) were used to investigate the presence of bioactive compounds, particularly sulfur compounds responsible for garlic's antibacterial effects. The impact of loading two concentrations (0.1 and 0.2 g per milliliter) of garlic extract on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria was examined. Results indicated a decrease in the growth range of S. aureus from 109 to 106 (CFU/ml) and E. coli from 1011 to 109 (CFU/ml) upon treatment. Additionally, cell adhesion and viability tests conducted on MG63 cells revealed an 8% increase in cell viability with the 0.1 g per milliliter concentration and a 35% decrease with the 0.2 g per milliliter concentration of garlic extract after 72 h of incubation (They have been evaluated by Microculture tetrazolium (MTT) assay). GC-MS analysis identified the presence of diethyl phthalate compounds in the garlic extract, suggesting a potential correlation with cellular toxicity observed in the sample with the higher concentration (0.2 g per milliliter) of garlic extract. Overall, the TNTs loaded with 0.1 g per milliliter of garlic extract simultaneously demonstrated antibacterial activity, cell viability, adhesion, and growth enhancement.

Synthesis of P-(NiCo)CO3 /TiO2 /Ti Self-Supported Electrode with High Catalytic Activity and Stability for Hydrogen Evolution

Hydrogen is considered an ideal clean energy due to its high mass-energy density, and only water is generated after combustion. Water electrolysis is a sustainable method of obtaining a usable amount of pure hydrogen among the various hydrogen production methods. However, its development is still limited by applying expensive noble metal catalysts. Here, the dissolution-recrystallization process of TiO2 nanotube arrays in water with the hydrothermal reaction of a typical nickel-cobalt hydroxide synthesis process followed by phosphating to prepare a self-supported electrode with (NiCo)CO3 /TiO2 heterostructure named P-(NiCo)CO3 /TiO2 /Ti electrode is combined. The electrode exhibits an ultra-low overpotential of 31 mV at 10 mA  cm-2 with a Tafel slope of 46.2 mV dec-1 in 1 m KOH and maintained its stability after running for 500 h in 1 m KOH. The excellent catalytic activity can be attributed to the structure of nanotube arrays with high specific surface area, superhydrophilicity, and super aerophobicity on the electrode surface. In addition, the uniform (NiCo)CO3 /TiO2 heterostructure also accelerates the electron transfer on the electrode surface. Finally, DFT calculations demonstrate that phosphating also improves the ΔGH* and ΔGH2O of the electrode. The synthesis strategy also promotes the exploration of catalysts for other necessary electrocatalytic fields.

Fabrication of a micro/nanocomposite structure on the surface of high oxygen concentration titanium to promote bone formation

This study investigated the properties of the micro/nano composite structure on the surface of high oxygen concentration titanium (HOC-Ti) after anodic oxidation modification (HOC-NT) and evaluated its biocompatibility as a dental implant material in vitro and in vivo. HOC-Ti was produced by titanium powders and rutile powders using the powder metallurgy method. Its surface was modified by anodic oxidation. After detecting the electrochemical characteristics, the surface properties of HOC-NT were investigated. MC3T3 and MLO-Y4 cells were employed to evaluate the biocompatibility of HOC-NT and cocultured to study the effects of the changes in osteocytes induced by HOC-NT on osteoblasts. While, its possible mechanism was investigated. In addition, osseointegration around the HOC-NT implant was investigated through in vivo experiments. The results showed that a unique micronano composite structure on the HOC-Ti surface with excellent hydrophilicity and suitable surface roughness was created after anodic oxidation promoted by its electrochemical characteristics. The YAP protein may play an important role in regulating bone remodeling by β-catenin and Rankl/OPG Signaling Pathways. An in vivo study also revealed an accelerated formation rate of new bone and more stable osseointegration around the HOC-NT implant. In view of all experimental results, it could be concluded that the unique morphology of HOC-NT has enhanced physicochemical and biological properties. The promotion of bone formation around implants indicated the feasibility of HOC-NT for applications in oral implants.

Novel bilayer coating on gentamicin-loaded titanium nanotube for orthopedic implants applications

Fabricating a multifunctional orthopedic implant which prevents post-surgery infection is highly desirable in advanced materials applications. However, designing an antimicrobial implant, which simultaneously promotes a sustained drug release and satisfactory cell proliferation, remains a challenge. The current study presents a drug-loaded surface-modified titanium nanotube (TNT) implant with different surface chemistry which was developed to investigate the effect of surface coating on drug release, antimicrobial activity, and cell proliferation. Accordingly, sodium alginate and chitosan were coated on the surface of TNT implants with different coating orders through layer-by-layer assembly. The coatings' swelling ratio and degradation rate were around 613% and 75%, respectively. The drug release results showed that surface-coatings prolonged the releasing profile for about 4 weeks. Chitosan coated TNTs demonstrated greater inhibition zone at 16.33mm compared with the other samples where no inhibition zone was observed. However, chitosan and alginate coated TNTs exhibited smaller inhibition zones at 48.56mm and 43.28mm, respectively, compared to bare TNT, which can be attributed to the coatings preventing the antibiotic burst release. Higher viability of cultured osteoblast cells was observed for chitosan-coated TNT as the top layer compared to the bare TNT at 12.18%, indicating improved bioactivity of TNT implants when the chitosan has the most contact with cells. Coupled with the cell viability assay, molecular dynamics (MD) simulations were carried out by placing collagen and fibronectin near the considered substrates. In agreement with cell viability results, MD simulations also indicated that chitosan had the highest adsorption energy approximately 60Kcal/mol. In summary, the proposed bilayer chitosan-coated drug-loaded TNT implant with chitosan and sodium alginate coating as the top and the bottom layers, respectively, can be a potential candidate for orthopedic applications in the light of its bacterial biofilm prevention, better osteoconductivity, and providing an adequate drug release profile.

Different Cell and Tissue Behavior of Micro-/Nano-Tubes and Micro-/Nano-Nets Topographies on Selective Laser Melting Titanium to Enhance Osseointegration

Background and Purpose

Micro-/nano-tubes (TNTs) and micro-/nano-nets (TNNs) are the common and sensible choice in the first step of combined modifications of titanium surface for further functionalization in the purpose of extended indications and therapeutic effect. It is important to recognize the respective biologic reactions of these two substrates for guiding a biologically based first-step selection.

Materials and Methods

TNTs were produced by anodic oxidation and TNNs were formed by alkali-heat treatment. The original selective laser melting (SLM) titanium surface was set as control. Surface characterization was evaluated by scanning electron microscopy, surface roughness, and water contact angle measurements. Osteoclastogenesis and osteogenesis were measured. MC3T3-E1 cells and RAW 264.7 cells were used for in vitro assay in terms of adhesion, proliferation, and differentiation. In vivo assessments were taken on Beagle dogs with micro-CT and histological analysis.

Results

TNN and TNT groups performed decreased roughness and increased hydrophilicity compared with SLM group. For biological detections, the highest ALP activity and osteogenesis-related genes expression were observed in TNT group followed by TNN group (P <0.05). Interestingly, when it comes to the osteoclastogenesis, TNNs displayed lowest TRAP activity and osteoclastogenesis-related genes expression and TNTs were lower than SLM but higher than TNNs (P <0.05). BV/TV around implants was highest in TNT group after 4 weeks (P <0.05). HE, ALP and TRAP staining showed that osteogenic and osteoclastic activity around TNTs were both higher than TNNs (P <0.05).

Conclusion

TNNs and TNTs have dual advantages in promotion of osteogenesis and inhibition of osteoclastogenesis. Furthermore, TNNs showed better capability in inhibiting osteoclast activity while TNTs facilitated stronger osteogenesis. Our results implied that TNT substrates would take advantage in early application after implantation, while diseases with inappropriate osteoclast activity would prefer TNN substrates, which will guide a biologically based first-step selection on combined modification for different clinical purposes.

Characterization of Optimized TiO2 Nanotubes Morphology for Medical Implants: Biological Activity and Corrosion Resistance

Background

Nanostructured surface modifications of Ti-based biomaterials are moving up from a highly-promising to a successfully-implemented approach to developing safe and reliable implants.

Methods

The study’s main objective is to help consolidate the knowledge and identify the more suitable experimental strategies related to TiO₂ nanotubes-modified surfaces. In this sense, it proposes the thorough investigation of two optimized nanotubes morphologies in terms of their biological activity (cell cytotoxicity, alkaline phosphatase activity, alizarin red mineralization test, and cellular adhesion) and their electrochemical behavior in simulated body fluid (SBF) electrolyte. Layers of small-short and large-long nanotubes were prepared and investigated in their amorphous and crystallized states and compared to non-anodized samples.

Results

Results show that much more than the surface area development associated with the nanotubes’ growth; it is the heat treatment-induced change from amorphous to crystalline anatase-rutile structures that ensure enhanced biological activity coupled to high corrosion resistance.

Conclusion

Compared to both non-anodized and amorphous nanotubes layers, the crystallized nano-structures’ outstanding bioactivity was related to the remarkable increase in their hydrophilic behavior, while the enhanced electrochemical stability was ascribed to the thickening of the dense rutile barrier layer at the Ti surface beneath the nanotubes.

Silver-Deposited Nanoparticles on the Titanium Nanotubes Surface as a Promising Antibacterial Material into Implants

The main disadvantage of the implants is the associated infections. Therefore, in the long term, the possibility of improving the antibacterial capacity of different types of implants (dental, orthopedic) is being researched. The severity of the problem lies in the increasing bacterial resistance and finding appropriate alternative treatments for infectious diseases, which is an important research field nowadays. The purpose of this review is to draw a parallel between different studies analyzing the antibacterial activity and mechanism of silver nanoparticles (NP Ag) deposited on the titanium nanotubes (NTT), as well as the analysis of the NP Ag toxicity. This review also provides an overview of the synthesis and characterization of TiO2-derived nanotubes (NT). Thus, the analysis aims to present the existing knowledge to better understand the NP Ag implants benefits and their antibacterial activity.

An off-on electrochemiluminescence detection for microRNAs based on TiO2 nanotubes sensitized with gold nanoparticles as enhanced emitters

A sensitive electrochemiluminescence (ECL) assay for microRNAs (miRNAs) based on a semiconductor nanomaterial sensitized with noble-metal Au nanoparticles (NPs) is successfully developed. TiO₂ nanotubes (NTs) were equipped with Au NPs to obtain an enhanced ECL emitter. Then, an ECL assay for miRNA-21 was fabricated, which was based on the use of probe 2 DNA-functionalized Pt/PAMAM nanocomposites (NCs) assembled on the surface of Au/TiO₂ NT conjugate via DNA hybridization between probe 1 DNA and capture DNA. The Pt/PAMAM NCs act as an ECL quencher of Au/TiO₂ NTs via resonance energy transfer. After the binding of target miRNA-21 and the capture DNA, the Pt/PAMAM NCs were released and the ECL signal was recovered. An "off-on" ECL assay was achieved with a linear response from 0.01 to 10,000 pM. Finally, this method has been validated to be sensitive and specific for miRNAs in human serum samples. The ECL enhancement strategy opens a new way for fabricating various sensitive biosensors. Graphical abstract A sensitive "off-on" electrochemiluminescence analysis method was developed, which combined Au NP-enhanced ECL emission of TiO₂ nanotubes and an efficient energy-transfer system between Au/TiO₂ nanotubes and Pt/PAMAM nanocomposites.

Plasma Nitriding of TiO2 Nanotubes: N-Doping in Situ Investigations Using XPS

The nitrogen doping of titanium dioxide nanotubes (TiO₂ NTs) was investigated as a result of well-controlled plasma nitriding of TiO₂ NTs at a low temperature. This way of nitrogen doping is proposed as an alternative to chemical/electrochemical methods. The plasma nitriding process was performed in a preparation chamber connected to an X-ray photoelectron spectroscopy (XPS) spectrometer, and the nitrogen-doped TiO₂ NTs were next investigated in situ by XPS in the same ultrahigh vacuum (UHV) system. The collected high-resolution (HR) XPS spectra of N 1s, Ti 2p, O 1s, C 1s, and valence band (VB) revealed the formation of chemical bonds between titanium, nitrogen, and oxygen atoms as substitutional or interstitial species. Moreover, the results provided a characterization of the electronic states of N-TiO₂ NTs generated by various plasma nitriding and annealing treatments. The VB XPS spectrum showed a reduction in the TiO₂ band gap of about 0.6 eV for optimal nitriding and heat-treated conditions. The TiO₂ NTs annealed at 450 or 650 °C in air (ex situ) and nitrided under UHV conditions were used as reference materials to check the formation of Ti-N bonds in the TiO₂ lattice with a well-defined structure (anatase or a mixture of anatase and rutile). Scanning electron microscopy microscopic observations of the received materials were used to evaluate the morphology of the TiO₂ NTs after each step of the nitriding and annealing treatments.

TiO2 Nanotubes with Pt and Pd Nanoparticles as Catalysts for Electro-Oxidation of Formic Acid

In the present work, the magnetron sputtering technique was used to prepare new catalysts of formic acid electrooxidation based on TiO₂ nanotubes decorated with Pt (platinum), Pd (palladium) or Pd + Pt nanoparticles. TiO₂ nanotubes (TiO₂ NTs) with strictly defined geometry were produced by anodization of Ti foil and Ti mesh in a mixture of glycerol and water with ammonium fluoride electrolyte. The above mentioned catalytically active metal nanoparticles (NPs) were located mainly on the top of the TiO₂ NTs, forming 'rings' and agglomerates. A part of metal nanoparticles decorated also TiO₂ NTs walls, thus providing sufficient electronic conductivity for electron transportation between the metal nanoparticle rings and Ti current collector. The electrocatalytic activity of the TiO₂ NTs/Ti foil, decorated by Pt, Pd and/or Pd + Pt NPs was investigated by cyclic voltammetry (CV) and new Pd/TiO₂ NTs/Ti mesh catalyst was additionally tested in a direct formic acid fuel cell (DFAFC). The results so obtained were compared with commercial catalyst-Pd/Vulcan. CV tests have shown for carbon supported catalysts, that the activity of TiO₂ NTs decorated with Pd was considerably higher than that one decorated with Pt. Moreover, for TiO₂ NTs supported Pd catalyst specific activity (per mg of metal) was higher than that for well dispersed carbon supported commercial catalyst. The tests at DFAFC have revealed also that the maximum of specific power for 0.2 Pd/TiO₂ catalyst was 70% higher than that of the commercial one, Pd/Vulcan. Morphological features, and/or peculiarities, as well as surface composition of the resulting catalysts have been studied by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and chemical surface analytical methods (X-ray photoelectron spectroscopy-XPS; Auger electron spectroscopy-AES).

Enhanced antibacterial activity of titanium by surface modification with polydopamine and silver for dental implant application

BACKGROUND

Biofilm formation and microbial colonization on the surface of implant devices may cause dental caries and peri-implantitis. Therefore, various surface treatments have been developed to improve the antibacterial activity of titanium implant.

METHODS

Silver-loaded polydopamine coating was formed by immersing pure titanium in dopamine hydrochloride/HCl buffer solution for 24 h in 50 mL silver nitrate solutions with different concentrations for 30 min. Microbial growth inhibition and microbial growth curve analyses for bacterial solutions of Streptococcus mutans and Porphyromonas gingivalis incubated with the specimens were respectively conducted by counting the numbers of colonies on agar solid medium and by measuring absorbance using enzyme-linked immunosorbent assay reader.

RESULTS

Silver nanoparticles were uniformly distributed over the whole surface of the polydopamine and silver-coated titanium specimens. The numbers of microbial colonies for both bacteria cultured with surface-modified titanium were significantly lower than those cultured with uncoated titanium. When Streptococcus mutans and Porphyromonas gingivalis were cultured with surface-modified titanium, the lag phase of the growth curves for both bacteria was continually maintained, whereas the lag phase for Streptococcus mutans and Porphyromonas gingivalis changed to exponential phase after 9 and 15 h, respectively, when both bacteria were cultured with uncoated titanium.

CONCLUSION

It was confirmed that the coating of polydopamine and silver on the surface of titanium effectively retards the microbial growth, which can cause the formation of biofilm and pathogenesis of gum disease in the mouth.

Enzyme responsive titanium substrates with antibacterial property and osteo/angio-genic differentiation potentials

After implantation into a host, titanium (Ti) orthopaedic materials are facing two major clinical challenges: bacterial infection and aseptic loosening, which directly determine the long-term survival of the implant. To endow Ti implant with self-defensive antibacterial properties and desirable osteo/angio-genic differentiation potentials, hyaluronic acid (HA)-gentamicin (Gen) conjugates (HA-Gen) and chitosan (Chi) polyelectrolyte multilayers were constructed on deferoxamine (DFO) loaded titania nanotubes (TNT) substrates via layer-by-layer (LBL) assembly technique, termed as TNT/DFO/HA-Gen. The HA-Gen conjugate was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (¹H NMR). The physicochemical properties of the substrates were characterized by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The on-demand DFO release was associated with the degradation of multilayers triggered by exogenous hyaluronidase, which indicated enzymatic and bacterial responsiveness. The TNT/DFO/HA-Gen substrates displayed effective antifouling and antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), while were favourable for the adhesion, proliferation and osteo/angio-genic differentiation of mesenchymal stem cells (MSCs). The multifaceted drug-device combination (DDC) strategy showed potential applications in orthopaedic fields.

Voltammetric determination of human papillomavirus 16 DNA by using interdigitated electrodes modified with titanium dioxide nanoparticles

A gene sensor for rapid detection of the Human Papillomavirus 16 (HPV 16) which is associated with the appearance of cervical cancer was developed. The assay is based on voltammetric determination of HPV 16 DNA by using interdigitated electrodes modified with titanium dioxide nanoparticles. Titanium dioxide nanoparticles (NPs) were used to modify a semiconductor-based interdigitated electrode (IDE). The surface of the NPs was then functionalized with a commercial 24-mer oligomer DNA probe for HPV 16 that was modified at the 5' end with a carboxyl group. If the probe interacts with the HPV 16 ssDNA, the current, best measured at a working voltage of 1.0 V, increases. The gene sensor has has a ∼ 0.1 fM limit of detection which is comparable to other sensors. The dielectric voltammetry analysis was carried out from 0 V to 1 V. The electrochemical sensitivity of the IDE is 2.5 × 10^-5 μA·μM^-1·cm^-2. Graphical abstract Schematic of an interdigitated electrode (IDE) modified with titanium dioxide nanoparticles for voltammetric determination of HPV 16 DNA by using an appropriate DNA probe.

In vitro evaluation of the toxicity and underlying molecular mechanisms of Janus Fe3 O4 -TiO2 nanoparticles in human liver cells

Recent studies show that Janus Fe3 O4 -TiO2 nanoparticles (NPs) have potential applications as a multifunctional agent of magnetic resonance imaging (MRI) and photodynamic therapy (PDT) for the diagnosis and therapy of cancer. However, little work has been done on their biological effects. To evaluate the toxicity and underlying molecular mechanisms of Janus Fe3 O4 -TiO2 nanoparticles, an in vitro study using a human liver cell line HL-7702 cells was conducted. For comparison, the Janus Fe3 O4 -TiO2 NPs parent material TiO2 NPs was also evaluated. Results showed that both Fe3 O4 -TiO2 NPs and TiO2 NPs decreased cell viability and ATP levels when applied in treatment, but increased malonaldehyde (MDA) and reactive oxygen species (ROS) generation. Mitochondria JC-1 staining assay showed that mitochondrial membrane permeability injury occurred in both NPs treated cells. Cell viability analysis showed that TiO2 NPs induced slightly higher cytotoxicity than Fe3 O4 -TiO2 NPs in HL7702 cells. Western blotting indicated that both TiO2 NPs and Fe3 O4 -TiO2 NPs could induce apoptosis, inflammation, and carcinogenesis related signal protein alterations. Comparatively, Fe3 O4 -TiO2 NPs induced higher signal protein expressions than TiO2 NPs under a high treatment dose. However, under a low dose (6.25 μg/cm2 ), neither NPs had any significant toxicity on HL7702 cells. In addition, our results suggest both Fe3 O4 -TiO2 NPs and TiO2 NPs could induce oxidative stress and have a potential carcinogenetic effect in vitro. Further studies are needed to elaborate the detailed mechanisms of toxicity induced by a high dose of Fe3 O4 -TiO2 NPs.

Regulating the local pH level of titanium via Mg-Fe layered double hydroxides films for enhanced osteogenesis

Hard tissue implant materials which can cause a suitable alkaline microenvironment are thought to be beneficial for stimulating osteoblast differentiation while suppressing osteoclast generation. To make the local pH around the interface between materials and cells controllable, we prepared a series of Mg-Fe layered double hydroxide (LDH) films on acid-etched pure titanium surfaces via hydrothermal treatment. By adjusting the Mg/Fe proportion ratio, the interlayer spacing of Mg-Fe LDHs was regulated, making their OH- exchange abilities adjustable, and this ultimately resulted in a microenvironment with a controllable pH value. In vitro experiments demonstrated that the Mg-Fe LDH film-modified titanium surface possessed good biocompatibility and osteogenic activity, especially the Mg-Fe LDH film with Mg/Fe proportion ratio of 4, which could form a suitable alkaline microenvironment for the growth and osteogenetic differentiation of stem cells. These results demonstrate the potential application of the prepared Mg-Fe LDH films in enhancing the osteogenesis of implant materials while providing a new way into the design of controllable alkaline environment.

High-Throughput Screening of Rat Mesenchymal Stem Cell Behavior on Gradient TiO2 Nanotubes

The dimension of TiO₂ nanotubes (TNTs) ranges from several nanometers to hundreds of nanometers. This variety raises the difficulty of screening suitable nanotube dimension for biomedical applications. Herein, we report the use of a simple one-step bipolar anodization method for fabrication of TNT gradients with diameter range from 30 to 100 nm. The gradient TNTs were successfully applied for high-throughput screening of TNT size effect on cell responses, including cell adhesion, proliferation, and differentiation. Results reveal that no significant difference in adherent cell number could be found within the range of 30-87 nm in both the presence and absence of serum proteins. On the contrary, large nanotubes (with outer diameter >87 nm) profoundly reduce cell adhesion in both the presence and absence of serum proteins, indicating TNT size could affect cell adhesion directly without the adsorbed proteins. The size effect on cell behavior becomes prominent with time that cell proliferation and differentiation decrease with increasing nanotube size. This size effect can be comprehended by protein adsorption and the formation of focal adhesion. Another two sample applications of gradient TNTs demonstrate gradient TNTs are promising for high-throughput screening.

Deferoxamine loaded titania nanotubes substrates regulate osteogenic and angiogenic differentiation of MSCs via activation of HIF-1α signaling

To develop biomaterials for inducing osteogenic and angiogenic differentiation of mesenchymal stem cells (MSCs) is crucial for bone repair. In this study, we employed titania nanotubes (TNT) as drug nanoreservoirs to load deferoxamine (DFO), and then deposited chitosan (Chi) and gelatin (Gel) multilayer as coverage structure via layer-by-layer (LBL) assembly technique, resulting in TNT-DFO-LBL substrates. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements were employed to characterize the physical and chemical properties of the substrates. The results proved the successful fabrication of multilayer coating on TNT array. DFO released from the TNT arrays in a sustained manner. The drug-device combination titanium (Ti) substrates positively improved the adhesion, proliferation, osteogenic/angiogenic differentiation of MSCs and mediated the growth behavior of human umbilical vein endothelial cells (HUVECs). Moreover, the TNT-DFO-LBL substrates up-regulated osteogenic and angiogenic differentiation related genes expression of MSCs by activating HIF-1α signaling pathway. The approach presents here has a potential impact on the development of high quality Ti-based orthopedic implants.

Progress in TiO2 nanotube coatings for biomedical applications: a review

Titanium dioxide nanotubes (TNTs) have drawn wide attention and been extensively applied in the field of biomedicine, due to their large specific surface area, good corrosion resistance, excellent biocompatibility, and enhanced bioactivity. This review describes the preparation of TNTs and the surface modification that entrust the nanotubes with better antibacterial property and enhanced osteoblast adhesion, proliferation, and differentiation. Considering the contact between TNTs' surface and surrounding tissues after implantation, the interactions between TNTs (with properties including their diameter, length, wettability, and crystalline phase) and proteins, platelets, bacteria, and cells are illustrated. The state of the art in the applications of TNTs in dentistry, orthopedic implants, and cardiovascular stents are introduced. In particular, the application of TNTs in biosensing has attracted much attention due to its ability for the rapid diagnosis of diseases. Finally, the difficulties and challenges in the practical application of TNTs are also discussed.

Effects of different hierarchical hybrid micro/nanostructure surfaces on implant osseointegration

BACKGROUND

Hierarchical hybrid micro/nanostructure implant surfaces are considered to better mimic the hierarchical structure of bone and the nanostructures substantively influence osseointegration through managing cell behaviors.

PURPOSE

To enhance implant osseointegration for further clinical application, we evaluated the material properties and osseointegration effects of hierarchical surfaces with different nano-morphologies, using a rat model.

MATERIALS AND METHODS

Two representative surface fabrication methods, hydrofluoric (HF) acid etching combined with anodization (HF + AN) or magnetron sputtering (HF + MS), were selected. Sample material properties were evaluated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and epoxy resin docking tensile test. Implants with different surfaces were inserted into the distal femurs of rats. After 12 weeks, osseointegration was examined by microcomputed tomography (micro-CT), histological, and biomechanical tests.

RESULTS

Tensile testing demonstrated high bonding strength at coating/implant in the HF + MS group. Micro-CT revealed increased bone volume/total volume and significantly reduced trabecular separation in HF + MS versus other groups. Histological analysis showed significantly higher HF + MS bone-to-implant contact (74.78 ± 4.40%) versus HF + AN (65.11 ± 5.10%) and machined samples (56.03 ± 3.23%). The maximal HF + MS pull-out force increased by 33.7% versus HF + AN.

CONCLUSIONS

These results indicated that HF + MS surfaces exhibited superior material property in terms of bonding strength and favorable implant osseointegration compared to other groups.

Titanium dioxide nanotube membranes for solar energy conversion: effect of deep and shallow dopants

Here we show the effect of shallow and deep dopants on titanium dioxide (TiO₂) nanotube membranes, for applications in photocatalytic, photoelectrochemical, photovoltaic, and other photosensitized devices for converting light into chemical feedstocks or electricity.

Antibacterial and cytocompatible AgNPs constructed with the assistance of Mefp-1 for orthopaedic implants

For the first time, Mefp-1 coating has been used in surface antibacterial and biocompatible modifications based on its multifunctionality.

Highly Functional TNTs with Superb Photocatalytic, Optical, and Electronic Performance Achieving Record PV Efficiency of 10.1% for 1D-Based DSSCs

Different nanostructures of TiO2 play an important role in the photocatalytic and photoelectronic applications. TiO2 nanotubes (TNTs) have received increasing attention for these applications due to their unique physicochemical properties. Focusing on highly functional TNTs (HF-TNTs) for photocatalytic and photoelectronic applications, this study describes the facile hydrothermal synthesis of HF-TNTs by using commercial and cheaper materials for cost-effective manufacturing. To prove the functionality and applicability, these TNTs are used as scattering structure in dye-sensitized solar cells (DSSCs). Photocatalytic, optical, Brunauer-Emmett-Teller (BET), electrochemical impedance spectrum, incident-photon-to-current efficiency, and intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy characterizations are proving the functionality of HF-TNTs for DSSCs. HF-TNTs show 50% higher photocatalytic degradation rate and also 68% higher dye loading ability than conventional TNTs (C-TNTs). The DSSCs having HF-TNT and its composite-based multifunctional overlayer show effective light absorption, outstanding light scattering, lower interfacial resistance, longer electron lifetime, rapid electron transfer, and improved diffusion length, and consequently, J SC , quantum efficiency, and record photoconversion efficiency of 10.1% using commercial N-719 dye is achieved, for 1D-based DSSCs. These new and highly functional TNTs will be a concrete fundamental background toward the development of more functional applications in fuel cells, dye-sensitized solar cells, Li-ion batteries, photocatalysis process, ion-exchange/adsorption process, and photoelectrochemical devices.

Recent Advances in TiO2 -Based Nanostructured Surfaces with Controllable Wettability and Adhesion

Bioinspired surfaces with special wettability and adhesion have attracted great interest in both fundamental research and industry applications. Various kinds of special wetting surfaces have been constructed by adjusting the topographical structure and chemical composition. Here, recent progress of the artificial superhydrophobic surfaces with high contrast in solid/liquid adhesion has been reviewed, with a focus on the bioinspired construction and applications of one-dimensional (1D) TiO2-based surfaces. In addition, the significant applications related to artificial super-wetting/antiwetting TiO2-based structure surfaces with controllable adhesion are summarized, e.g., self-cleaning, friction reduction, anti-fogging/icing, microfluidic manipulation, fog/water collection, oil/water separation, anti-bioadhesion, and micro-templates for patterning. Finally, the current challenges and future prospects of this renascent and rapidly developing field, especially with regard to 1D TiO2-based surfaces with special wettability and adhesion, are proposed and discussed.

Stability of titania nanotube arrays in aqueous environment and the related factors

Titania nanotube arrays (NTAs) on titanium (Ti) fabricated by electrochemical anodization have attracted tremendous interest for diverse applications, of which most perform in aqueous environment or related to interaction with water. The NTAs are widely studied however the related factor of stability of NTAs when applied in such environment has rarely been concerned. We report that the annealed anatase NTAs are stable but the non-annealed amorphous NTAs are unstable to undergo specific structural change accompanied with a process of amorphous TiO2 dissolution and anatase TiO2 recrystallization. Quite unexpectedly, the non-annealed NTAs still show good stability without structural change in the cell culture media, possibly due to the presence of inorganics that may interfere with the TiO2 dissolution/redeposition process. The pH value of the aqueous environment is not a determinant factor for the structural change for non-annealed NTAs or not, while the temperature and the existence of F(-) can accelerate the structural change process. F(-) may play a very important role in the change process.

In situ plasmonic Ag nanoparticle anchored TiO2 nanotube arrays as visible-light-driven photocatalysts for enhanced water splitting

An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ ≥ 420 nm). It was found that the hydrogen production rate of the Ag@TiO2 NTAs prepared with ultrasonication-assisted deposition for 5 min was approximately 15 times higher than that of its pristine TiO2 NTAs counterpart. The highly efficient photocatalytic hydrogen evolution is attributed to the SPR effect of Ag for enhanced visible light absorption and boosting the photogenerated electron-hole separation/transfer. This strategy is promising for the design and construction of high efficiency TiO2 based photocatalysts for solar energy conversion.

Pore orientation effects on the kinetics of mesostructure loss in surfactant templated titania thin films

The mesostructure loss kinetics are measured as a function of the orientation of micelles in 2D hexagonal close packed (HCP) columnar mesostructured titania thin films using in situ grazing incidence small angle X-ray scattering (GISAXS). Complementary supporting information is provided by ex situ scanning electron microscopy. Pluronic surfactant P123 acts as the template to synthesize HCP structured titania thin films. When the glass substrates are modified with crosslinked P123, the micelles of the HCP mesophase align orthogonal to the films, whereas a mix of parallel and orthogonal alignment is found on unmodified glass. The rate of mesostructure loss of orthogonally oriented (o-HCP) thin films (∼60 nm thickness) prepared on modified substrate is consistently found to be less by a factor of 2.5 ± 0.35 than that measured for mixed orientation HCP films on unmodified substrates. The activation energy for mesostructure loss is only slightly greater for films on modified glass (155 ± 25 kJ mol(-1)) than on unmodified (128 kJ mol(-1)), which implies that the rate difference stems from a greater activation entropy for mesostructure loss in o-HCP titania films. Nearly perfect orthogonal orientation of micelles on modified surfaces contributes to the lower rate of mesostructure loss by supporting the anisotropic stresses that develop within the films during annealing due to continuous curing, sintering and crystallization into the anatase phase during high temperature calcination (>450 °C). Because the film thickness dictates the propagation of orientation throughout the films and the degree of confinement, thicker (∼250 nm) films cast onto P123-modified substrates have a much lower activation energy for mesostructure loss (89 ± 27 kJ mol(-1)) due to the mix of orientations found in the films. Thus, this kinetic study shows that thin P123-templated o-HCP titania films are not only better able to achieve good orthogonal alignment of the mesophase relative to thicker films or films on unmodified substrates, but that alignment of the mesophase in the films stabilizes the mesophase against thermally-induced mesostructure loss.

Nanopatterned polymer brushes: conformation, fabrication and applications

Surfaces with end-grafted, nanopatterned polymer brushes that exhibit well-defined feature dimensions and controlled chemical and physical properties provide versatile platforms not only for investigation of nanoscale phenomena at biointerfaces, but also for the development of advanced devices relevant to biotechnology and electronics applications. In this review, we first give a brief introduction of scaling behavior of nanopatterned polymer brushes and then summarize recent progress in fabrication and application of nanopatterned polymer brushes. Specifically, we highlight applications of nanopatterned stimuli-responsive polymer brushes in the areas of biomedicine and biotechnology.