Self-Modification of Defective TiO2 under Controlled H2/Ar Gas Environment and Dynamics of Photoinduced Surface Oxygen Vacancies.

In recent years, defective TiO2 has caught considerable research attention because of its potential to overcome the limits of low visible light absorption and fast charge recombination present in pristine TiO2 photocatalysts. Among the different synthesis conditions for defective TiO2, ambient pressure hydrogenation with the addition of Ar as inert gas for safety purposes has been established as an easy method to realize the process. Whether the Ar gas might still influence the resulting photocatalytic properties and defective surface layer remains an open question. Here, we reveal that the gas flow ratio between H2 and Ar has a crucial impact on the defective structure as well as the photocatalyic activity of TiO2. In particular, transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS) revealed a larger width of the defective surface layer when using a H2/Ar (50 %-50 %) gas mixture over pure H2. A possible reason could be the increase in dynamic viscosity of the gas mixture when Ar is added. Additionally, photoinduced enhanced Raman spectroscopy (PIERS) is implemented as a complementary approach to investigate the dynamics of the defective structures under ambient conditions which cannot be effortlessly realized by vacuum techniques like TEM.

Antibacterial properties of marine algae incorporated polylactide acid membranes as an alternative to clinically applied different collagen membranes.

The reconstruction of bony defects in the alveolar crest poses challenges in dental practice. Guided tissue regeneration (GTR) and guided bone regeneration (GBR) procedures utilize barriers to promote bone regeneration and prevent epithelial growth. This study focuses on evaluating the antibacterial properties of marine algae-polylactic acid (PLA) composite membranes compared to commercially available collagen membranes. Marine algae (Corallina elongata, Galaxaura oblongata, Cystoseira compressa, Saragassum vulgare, and Stypopodium schimperi) were processed into powders and blended with PLA to fabricate composite membranes. Cytocompatibility assays using human periodontal ligament fibroblasts (n = 3) were performed to evaluate biocompatibility. Antibacterial effects were assessed through colony-forming units (CFU) and scanning electron microscopy (SEM) analysis of bacterial colonization on the membranes. The cytocompatibility assays demonstrated suitable biocompatibility of all marine algae-PLA composite membranes with human periodontal ligament fibroblasts. Antibacterial assessment revealed that Sargassum vulgare-PLA membranes exhibited the highest resistance to bacterial colonization, followed by Galaxaura oblongata-PLA and Cystoseira compressa-PLA membranes. SEM analysis confirmed these findings and revealed smooth surface textures for the marine algae-PLA membranes compared to the fibrous and porous structures of collagen membranes. Marine algae-PLA composite membranes show promising antibacterial properties and cytocompatibility for guided bone and tissue regeneration applications. Sargassum vulgare-PLA membranes demonstrated the highest resistance against bacterial colonization. These findings suggest that marine algae-PLA composite membranes could serve as effective biomaterials for infection control and tissue regeneration. Further in vivo validation and investigation of biodegradation properties are necessary to explore their clinical potential.

Decontaminative Properties of Cold Atmospheric Plasma Treatment on Collagen Membranes Used for Guided Bone Regeneration.

Background cold atmospheric plasma (CAP) is known to be a surface-friendly yet antimicrobial and activating process for surfaces such as titanium. The aim of the present study was to describe the decontaminating effects of CAP on contaminated collagen membranes and their influence on the properties of this biomaterial in vitro. Material and Methods: A total of n = 18 Bio-Gide® (Geistlich Biomaterials, Baden-Baden, Germany) membranes were examined. The intervention group was divided as follows: n = 6 membranes were treated for one minute, and n = 6 membranes were treated for five minutes with CAP using kINPen® MED (neoplas tools GmbH, Greifswald, Germany) with an output of 5 W, respectively. A non-CAP-treated group (n = 6) served as the control. The topographic alterations were evaluated via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Afterward, the samples were contaminated with E. faecalis for 6 days, and colony-forming unit (CFU) counts and additional SEM analyses were performed. The CFUs increased with CAP treatment time in our analyses, but SEM showed that the surface of the membranes was essentially free from bacteria. However, the deeper layers showed remaining microbial conglomerates. Furthermore, we showed, via XPS analysis, that increasing the CAP time significantly enhances the carbon (carbonyl group) concentration, which also correlates negatively with the decontaminating effects of CAP. Conclusions: Reactive carbonyl groups offer a potential mechanism for inhibiting the growth of E. faecalis on collagen membranes after cold atmospheric plasma treatment.

Nanoscale Synergetic Effects on Ag-TiO2 Hybrid Substrate for Photoinduced Enhanced Raman Spectroscopy (PIERS) with Ultra-Sensitivity and Reusability.

Here, a 4N-in-1 hybrid substrate concept (nanocolumnar structures, nanocrack network, nanoscale mixed oxide phases, and nanometallic structures) for ultra-sensitive and reliable photo-induced-enhanced Raman spectroscopy (PIERS), is proposed. The use of the 4N-in-1 hybrid substrate leads to an ≈50-fold enhancement over the normal surface-enhanced Raman spectroscopy, which is recorded as the highest PIERS enhancement to date. In addition to an improved Raman signal, the 4N-in-1 hybrid substrate provides a high detection sensitivity which may be attributed to the activation possibility at extremely low UV irradiation dosage and prolonged relaxation time (long measurement time). Moreover, the 4N-in-1 hybrid substrate exhibits a superior photocatalytic degradation performance of analytes, allowing its reuse at least 18 times without any loss of PIERS activity. The use of the 4N-in-1 concept can be adapted to biomedicine, forensic, and security fields easily.

Marine Algae Incorporated Polylactide Acid Patch: Novel Candidate for Targeting Osteosarcoma Cells without Impairing the Osteoblastic Proliferation.

Biodegradable collagen-based materials have been preferred as scaffolds and grafts for diverse clinical applications in density and orthopedy. Besides the advantages of using such bio-originated materials, the use of collagen matrices increases the risk of infection transmission through the cells or the tissues of the graft/scaffold. In addition, such collagen-based solutions are not counted as economically feasible approaches due to their high production cost. In recent years, incorporation of marine algae in synthetic polymers has been considered as an alternative method for preparation grafts/scaffolds since they represent abundant and cheap source of potential biopolymers. Current work aims to propose a novel composite patch prepared by blending Sargassum vulgare powders (SVP) to polylactide (PLA) as an alternative to the porcine-derived membranes. SVP-PLA composite patches were produced by using a modified solvent casting method. Following detailed material characterization to assess the cytocompatibility, human osteoblasts (HOBs) and osteosarcoma cells (SaOS-2) were seeded on neat PLA and SVP-PLA patches. MTT and BrdU assays indicated a greater cytocompatibility and higher proliferation for HOBs cultured on SVP-PLA composite than for those cultured on neat PLA. SaOS-2 cells cultured on SVP-PLA exhibited a significant decrease in cell proliferation. The composite patch described herein exhibits an antiproliferative effect against SaOS-2 cells without impairing HOBs' adhesion and proliferation.

Initiated Chemical Vapor Deposition (iCVD) Functionalized Polylactic Acid-Marine Algae Composite Patch for Bone Tissue Engineering.

The current study aimed to describe the fabrication of a composite patch by incorporating marine algae powders (MAPs) into poly-lactic acid (PLA) for bone tissue engineering. The prepared composite patch was functionalized with the co-polymer, poly (2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) (p(HEMA-co-EGDMA)) via initiated chemical vapor deposition (iCVD) to improve its wettability and overall biocompatibility. The iCVD functionalized MAP-PLA composite patch showed superior cell interaction of human osteoblasts. Following the surface functionalization by p(HEMA-co-EGDMA) via the iCVD technique, a highly hydrophilic patch was achieved without tailoring any morphological and structural properties. Moreover, the iCVD modified composite patch exhibited ideal cell adhesion for human osteoblasts, thus making the proposed patch suitable for potential biomedical applications including bone tissue engineering, especially in the fields of dentistry and orthopedy.

Photodeposition of Au Nanoclusters for Enhanced Photocatalytic Dye Degradation over TiO2 Thin Film.

Au nanoparticle (NP) decorated heterogeneous TiO2 catalysts are known to be effective in the degradation of various organic pollutants. The photocatalytic performance of such Au-TiO2 structures remarkably depends on the size, morphology, and surface coverage of the Au NPs decorating TiO2. Here we propose an effective way of preparing a highly active Au nanocluster (NC) decorated TiO2 thin film by a novel photodeposition method. By altering the solvent type as well as the illumination time, we achieved well-controlled surface coverage of TiO2 by Au NCs, which directly influences the photocatalytic performance. Here the Au NCs coverage affects both the electron store capacity and the optical absorption of the hybrid Au-TiO2 system. At low surface coverage, 19.2-29.5%, the Au NCs seem to enhance significantly the optical adsorption of TiO2 at UV wavelengths which therefore leads to a higher photocatalytic performance.

Early osteoblastic activity on TiO2 thin films decorated with flower-like hierarchical Au structures.

Titanium alloys are the most commonly used dental and orthopedic implant materials due to their proven biocompatibility and mechanical properties. The native oxide layer (TiO2 layer) formed on such Ti-based implants acts as the self-protecting layer against possible ion release. Increasing the oxide layer thickness further on such TiO2 implants even opens the triggering of the osseointegration process if the oxide layer is having a certain degree of roughness, preferably higher. This work reports a novel photocatalytic patterning of sputter deposited TiO2 layers with flower-like Au structures to enhance the early osteoblastic activity. The prepared hierarchical Au structures, composed of micro- and nanoscale features on the top, lead to improved number of filopodia formation. This suggest that proposed Au-TiO2 surface may foster the cell attachment and as well as cell proliferation.

Pathways to Tailor Photocatalytic Performance of TiO2 Thin Films Deposited by Reactive Magnetron Sputtering.

TiO2 thin films are used extensively for a broad range of applications including environmental remediation, self-cleaning technologies (windows, building exteriors, and textiles), water splitting, antibacterial, and biomedical surfaces. While a broad range of methods such as wet-chemical synthesis techniques, chemical vapor deposition (CVD), and physical vapor deposition (PVD) have been developed for preparation of TiO2 thin films, PVD techniques allow a good control of the homogeneity and thickness as well as provide a good film adhesion. On the other hand, the choice of the PVD technique enormously influences the photocatalytic performance of the TiO2 layer to be deposited. Three important parameters play an important role on the photocatalytic performance of TiO2 thin films: first, the different pathways in crystallization (nucleation and growth); second, anatase/rutile formation; and third, surface area at the interface to the reactants. This study aims to provide a review regarding some strategies developed by our research group in recent years to improve the photocatalytic performance of TiO2 thin films. An innovative approach, which uses thermally induced nanocrack networks as an effective tool to enhance the photocatalytic performance of sputter deposited TiO2 thin films, is presented. Plasmonic and non-plasmonic enhancement of photocatalytic performance by decorating TiO2 thin films with metallic nanostructures are also briefly discussed by case studies. In addition to remediation applications, a new approach, which utilizes highly active photocatalytic TiO2 thin film for micro- and nanostructuring, is also presented.

Controlling fibroblast adhesion and proliferation by 1D Al2O3 nanostructures.

The fibrotic encapsulation, which is mainly accompanied by an excessive proliferation of fibroblasts, is an undesired phenomenon after the implantation of various medical devices. Beside the surface chemistry, the topography plays also a major role in the fibroblast-surface interaction. In the present study, one-dimensional aluminium oxide (1D Al2O3) nanostructures with different distribution densities were prepared to reveal the response of human fibroblasts to the surface topography. The cell size, the cell number and the ability to form well-defined actin fibres and focal adhesions were significantly impaired with increasing distribution density of the 1D Al2O3 nanostructures on the substratum.

Cauliflower-like CeO2-TiO2 hybrid nanostructures with extreme photocatalytic and self-cleaning properties.

In recent years, heterogeneous photocatalysis has gained enormous interest due to increasing concerns about environmental pollution. Here we propose a facile approach to synthesize cauliflower-like CeO2-TiO2 hybrid structures by magnetron reactive sputtering, exhibiting an extremely high photocatalytic activity. While heating and air-quenching of the sputter deposited TiO2 thin film (first layer) triggered the formation of a nanocrack network, the second heat-treatment led to transformation of the CeO2 film (second layer) into CeO2 nanoclusters (NCs). We attribute the resulting high photocatalytic activity to the confined structure of the CeO2 NCs and the CeO2-TiO2 interface, which allows Ce3+/Ce4+ dynamic shifting. In addition to high photocatalytic activity in an aqueous medium, the prepared CeO2-TiO2 hybrid structures exhibited significant self-cleaning properties in air (non-aqueous).

Enhancing adhesion and alignment of human gingival fibroblasts on dental implants.

BACKGROUND: Promoting the directional attachment of gingiva to the dental implant leads to the formation of tight connective tissue which acts as a seal against the penetration of oral bacteria. Such a directional growth is mostly governed by the surface texture. MATERIAL AND METHODS: In this study, three different methods, mechanical structuring, chemical etching and laser treatment, have been explored for their applicability in promoting cellular attachment and alignment of human primary gingival fibroblasts (HGFIBs). RESULTS: The effectiveness of mechanical structuring was shown as a simple and a cost-effective method to create patterns to align HGIFIBs. CONCLUSION: Combining mechanical structuring with chemical etching enhanced both cellular attachment and the cellular alignment.

PTFEP-Al2O3 hybrid nanowires reducing thrombosis and biofouling.

Thrombosis and bacterial infection are major problems in cardiovascular implants. Here we demonstrated that a superhydrophobic surface composed of poly(bis(2,2,2-trifluoroethoxy)phosphazene) (PTFEP)-Al2O3 hybrid nanowires (NWs) is effective to reduce both platelet adhesion/activation and bacterial adherence/colonization. The proposed approach allows surface modification of cardiovascular implants which have 3D complex geometries.

Novel glass-like coatings for cardiovascular implant application: Preparation, characterization and cellular interaction.

Glass coatings are of great interest for biomedical implant application due to their excellent properties. Nowadays they are used in different fields including drug delivery, for bone tissue regeneration or as implant. Nevertheless they can only be applied using high temperatures. Therefore their usage in the field of cardiovascular implant application is still restricted. Accordingly new developments in this field have been carried out to overcome this problem and to coat cardiovascular implants. Here, novel glass-like coatings have been developed and applied using sol-gel technique at moderate temperatures. The biocompatibility and selectivity have been analyzed using human endothelial cells. The obtained results clarify that the developed compositions can either promote or suppress endothelial cell growth only by altering the sintering atmosphere. A later application as thin layer on cardiovascular implants like stents is conceivable.

Alignment of human cardiomyocytes on laser patterned biphasic core/shell nanowire assemblies.

The management of end stage heart failure patients is only possible by heart transplantation or by the implantation of artificial hearts as a bridge for later transplantation. However, these therapeutic strategies are limited by a lack of donor hearts and by the associated complications, such as coagulation and infection, due to the used artificial mechanical circulatory assist devices. Therefore, new strategies for myocardial regenerative approaches are under extensive research to produce contractile myocardial tissue in the future to replace non-contractile myocardial ischemic and scarred tissue. Different approaches, such as cell transplantation, have been studied intensively. Although successful approaches have been observed, there are still limitations to the application. It is envisaged that myocardial tissue engineering can be used to help replace infarcted non-contractile tissue. The developed tissue should later mimic the aligned fibrillar structure of the extracellular matrix and provide important guidance cues for the survival, function and the needed orientation of cardiomyocytes. Nanostructured surfaces have been tested to provide a guided direction that cells can follow. In the present study, the cellular adhesion/alignment of human cardiomyocytes and the biocompatibility have been investigated after cultivation on different laser-patterned nanowires compared with unmodified nanowires. As a result, the nanostructured surfaces possessed good biocompatibility before and after laser modification. The laser-induced scalability of the pattern enabled the growth and orientation of the adhered myocardial tissue. Such approaches may be used to modify the surface of potential scaffolds to develop myocardial contractile tissue in the future.

Surface topography and wetting modifications of PEEK for implant applications.

Polyetheretherketone (PEEK) is considered as a substitute for metallic implant materials due to its extremely low elastic modulus (3-4 GPa). Despite its good mechanical properties, PEEK exhibits a slow integration with the bone tissue due to its relatively inert surface and low biocompatibility. We introduced a dual modification method, which combines the laser and plasma surface treatments to achieve hierarchically patterned PEEK surfaces. While the plasma treatment leads to nanotopography, the laser treatment induces microstructures over the PEEK surface. On the other hand, plasma and laser treatments induce inhomogeneity in the surface chemistry in addition to the tailored surface topography. Therefore, we coated the structured PEEK surfaces with a thin alumina layer by pulsed laser deposition (PLD) to get identical surface chemistry on each substrate. Such alumina-coated PEEK surfaces are used as a model to investigate the effect of the surface topography on the wetting independent from the surface chemistry. Prepared surfaces bring advantages of enhanced wetting, multiscaled topography, proven biocompatibility (alumina layer), and low elastic modulus (PEEK as substrate), which together may trigger the use of PEEK in bone and other implant applications.

Strain-controlled growth of nanowires within thin-film cracks.

There is continued interest in finding quicker and simpler ways to fabricate nanowires, even though research groups have been investigating possibilities for the past decade. There are two reasons for this interest: first, nanowires have unusual properties-for example, they show quantum-mechanical confinement effects, they have a very high surface-to-volume ratio, enabling them to be used as sensors, and they have the ability to connect to individual molecules. Second, no simple method has yet been found to fabricate nanowires over large areas in arbitrary material combinations. Here we describe an approach to the generation of well-defined nanowire network structures on almost any solid material, up to macroscopic sample sizes. We form the nanowires within cracks in a thin film. Such cracks have a number of properties that make them attractive as templates for nanowire formation: they are straight, scalable down to nanometre size, and can be aligned (by using microstructure to give crack alignment via strain). We demonstrate the production of nanowires with diameter <16 nm, both singly and as networks; we have also produced aligned patterns of nanowires, and nanowires with individual contacts.