Graphdiyne-modified TiO2 nanofibers with osteoinductive and enhanced photocatalytic antibacterial activities to prevent implant infection

Inorganic Metal-Oxide Photocatalyst for H2 O2 Production

Hydrogen peroxide (H₂ O₂ ) is a mild but versatile oxidizing agent with extensive applications in bleaching, wastewater purification, medical treatment, and chemical synthesis. The state-of-art H₂ O₂ production via anthraquinone oxidation is hardly considered a cost-efficient and environment-friendly process because it requires high energy input and generates hazardous organic wastes. Photocatalytic H₂ O₂ production is a green, sustainable, and inexpensive process which only needs water and gaseous dioxygen as the raw materials and sunlight as the power source. Inorganic metal oxide semiconductors are good candidates for photocatalytic H₂ O₂ production due to their abundance in nature, biocompatibility, exceptional stability, and low cost. Progress has been made to enhance the photocatalytic activity toward H₂ O₂ production, however, H₂ O₂ photosynthesis is still in the laboratory research phase since the productivity is far from satisfaction. To inspire innovative ideas for boosting the H₂ O₂ yield in photocatalysis, the most well-studied metal oxide photocatalysts are selected and the modification strategies to improve their activity are listed. The mechanisms for H₂ O₂ production over modified photocatalysts are discussed to highlight the facilitating role of the modification methods. Besides, methods for the quantification of H₂ O₂ and associated radical intermediates are provided to guide future studies in this field.

A Biomimetic Composite Bilayer Dressing Composed of Alginate and Fibroin for Enhancing Full-Thickness Wound Healing

Full-thickness skin wound dressings are critically important for acute cutaneous wound healing. In this study, we developed a bilayer sheet originating from biological macromolecules, mimicking skin hierarchy structure. This sheet was composed of a steady silk fibroin (SF)/sodium alginate (SA) composite scaffold as the bottom regenerative layer and a SA film as the protective top layer. SEM analysis revealed the thickness of the top layer was ∼25 μm and was tightly adhered to the composite scaffold layer with interconnected pores (∼150 μm). The bilayer sheets displayed suitable water uptake capacity and high stability in water. The mass retention percentage of the bilayer sheets was approximately 50% during three weeks of PBS degradation in vitro. The tensile strength of the bilayer sheets significantly increased from 13.41 ± 3.75 kPa (single scaffold) to 59.81 ± 5.98 kPa. The composite scaffolds were more conducive to the growth and proliferation of human dermal microvascular endothelial cells. The experiment results in vivo demonstrated superior and faster epithelialisation and dermal regeneration in the wound treated with bilayer sheets because the sheets accelerated wound closure, reduced the inflammatory response, and promoted protein synthesis in the extracellular matrix and blood vessel ingrowth. This article is protected by copyright. All rights reserved.

Potential Application of Alternative Materials for Organic Pollutant Removal

The work aims to synthesize and characterize vegetal charcoal (or biochar) from Syzygium cumini (AC-SC), evaluating the adsorption capacity for dexamethasone drug (DEX) removal, using the kinetic and equilibrium adsorption. The samples were characterized by N₂ porosimetry, X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, zeta potential, and zero charge point. Adsorption equilibrium was carried out applying the Langmuir, Freundlich, Redlich-Peterson, Sips, and Toth models, and kinetic adsorption applied the pseudo-first order, pseudo-second order, Elovich, Avrami, and Weber-Morris models. AC-SC showed a heterogeneous and porous surface, negatively charged, crystalline structure, specific surface area of the 2.14 m² g^-1 and pH_ZCP = 7.36. About the effect of the AC-SC concentration, 5.0 g L^-1 showed the best DEX removal (53.02%), about the others' concentration (2.0 and 7.5 g L^-1). About the equilibrium and kinetic adsorption, the Sips model and pseudo-second order showed the best experimental data adjusted, indicating that the adsorption monolayer was dependent on the ions onto the biosorbent, with a maximum adsorption capacity of 0.744 mg g^-1 after 180 min. Therefore, AC-SC can be used as an alternative material in the removal of organic pollutants, such as drug removal.

Electrospun Nanofibers for Bone Regeneration: From Biomimetic Composition, Structure to Function

In recent years, a variety of novel materials and processing technologies have been developed to prepare tissue engineering scaffolds for bone defect repair. Among them, nanofibers fabricated via electrospinning technology...

Multifunctional Coatings of Titanium Implants Toward Promoting Osseointegration and Preventing Infection: Recent Developments

Titanium and its alloys are dominant material for orthopedic/dental implants due to their stable chemical properties and good biocompatibility. However, aseptic loosening and peri-implant infection remain problems that may lead to implant removal eventually. The ideal orthopedic implant should possess both osteogenic and antibacterial properties and do proper assistance to in situ inflammatory cells for anti-microbe and tissue repair. Recent advances in surface modification have provided various strategies to procure the harmonious relationship between implant and its microenvironment. In this review, we provide an overview of the latest strategies to endow titanium implants with bio-function and anti-infection properties. We state the methods they use to preparing these efficient surfaces and offer further insight into the interaction between these devices and the local biological environment. Finally, we discuss the unmet needs and current challenges in the development of ideal materials for bone implantation.

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

Eco-friendly bacteria-killing by nanorods through mechano-puncture with top selectivity

Nanorods can induce mechano-puncture of Staphylococcus aureus (S. aureus) that often impairs osseointegration of orthopedic implants, while the critical nanorod top sharpness able to puncture S. aureus and the predominant contributor between top sharpness and length to mechano-puncture activity remains elusive. Herein, we fabricated three kinds of Al₂O₃-wrapped nanorods patterned arrays with different lengths and top sharpness. The top-sharp nanorods have lengths of 469 and 884 nm and the shorter show a length identical to the top-flat nanorods. Driven by the equivalent adhesive force of S. aureus, the top-flat nanorods deform cell envelops, showing a bacteriostatic rate of 29% owing to proliferation-inhibited manner. The top-sharp nanorods puncture S. aureus, showing a bactericidal rate of 96% for the longer, and 98% for the shorter that simultaneously exhibits fair osseointegration in bacteria-infected rat tibias, identifying top sharpness as a predominate contributor to mechano-puncture activity. Based on finite-element simulation, such top-flat nanorod derives the maximum stress (S_max) of 5.65 MPa on cell wall, lower than its ultimate-tensile-strength (13 MPa); while such top-sharp and shorter nanorod derives S_max of 20.15 MPa to puncture cell envelop. Moreover, a critical top conical angle of 138° is identified for nanorods able to puncture S. aureus.

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Top sharpness depended mechano-puncture of nanorods against S. aureus is clarified.

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Top-flat nanorods deform bacterial cell envelop to inhibit their proliferation.

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Top-sharp nanorods (conical angle of 50°) puncture bacteria to intensely kill them.

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138° is confirmed as critical top conical angle for nanorods to puncture S. aureus.

Recent development in graphdiyne and its derivative materials for novel biomedical applications

Graphdiyne (GDY), which possess sp- and sp²-hybridized carbon and Dirac cones, offers unique physical and chemical properties, including an adjustable intrinsic bandgap, excellent charge carrier transfer efficiency, and superior conductivity compared to other carbon allotropes. These exceptional qualities of GDY and its derivatives have been successfully used in a variety of fields, including catalysis, energy, environmental protection, and biological applications. Herein, we focus on the potential application of GDY and its derivatives in the biomedical domain, including biosensing, biological protection, cancer therapy, and antibacterial agents, demonstrating how the biomimetic behavior of these materials can be a step forward in bridging the gap between nature and applications. Considering the excellent biocompatibility, solubility and selectivity of GDY and its derived materials, they have shown great potential as biosensing and bio-imaging materials. The unusual combination of properties in GDY has been used in biological applications such as "OFF-ON" DNA detection and enzymatic sensing, where GDY has a greater adsorption capacity than graphene and other 2D materials, resulting in increased sensitivity. GDY and its derivatives have also been used in cancer treatment due to their high doxorubicin (DOX) loading capacity (using-stacking) and photothermal conversion ability, and radiation protection since their initial biological use. The poor biodegradation rate of graphene demands the search for new nanomaterials. Accordingly, GDY has better biocompatibility and bio-safety than other 2D nanomaterials, especially graphene and its oxide, due to its absence of aggregation in the physiological environment. Thus, GDY-based nanomaterials have become promising candidates as bio-delivery carriers. Besides, GDY and GDY-based materials have also shown interesting applications in the fields of cell-culture, cell-growth and tissue engineering. Herein, we present a comprehensive review on the applications of GDY and its derivatives as biomedical materials, followed by their future perspectives. This review will provide an outlook for the application of graphene and its derivatives and may open up new horizons to inspire broader interests across various disciplines. Finally, the future prospects for GDY-based materials are examined for their potential biological use.

An Efficient Strategy for Reinforcing Flexible Ceramic Membranes

Herein, we present a facile reinforcement method for the large-scale fabrication of highly flexible, mechanically stable, temperature-resistant ceramic lightweight membranes based on the cross-linked assembly of zirconia-silica (ZrO₂-SiO₂) nanofibrous and montmorillonite (MMT) nanosheets through electrospinning and a subsequent calcination process. The resulting MMT@ZrO₂-SiO₂ membranes exhibit high flexibility with a bending rigidity of 0.2 cN mm^-1, robust mechanical performance with a tensile strength of up to 1.83 MPa, robust fire resistance, and temperature-invariant mechanical stability from -196 to 1000 °C. The thermal superinsulation with a thermal conductivity as low as 0.026 W m^-1 K^-1 and the improved mechanical strength can be attributed to the cross-linked interfacial interaction between the ZrO₂-SiO₂ nanofibers and the MMT nanosheets. Additionally, a firefighter uniform with MMT@ZrO₂-SiO₂ membranes inside features a superior thermal protective property up to the A2 level (combined flame and radiant exposure) and an excellent fire resistance of up to 1000 °C, which is ideal for next-generation firefighter uniform manufacturing.

Advances in Use of Nanomaterials for Musculoskeletal Regeneration

Since the worldwide incidence of bone disorders and cartilage damage has been increasing and traditional therapy has reached its limits, nanomaterials can provide a new strategy in the regeneration of bones and cartilage. The nanoscale modifies the properties of materials, and many of the recently prepared nanocomposites can be used in tissue engineering as scaffolds for the development of biomimetic materials involved in the repair and healing of damaged tissues and organs. In addition, some nanomaterials represent a noteworthy alternative for treatment and alleviating inflammation or infections caused by microbial pathogens. On the other hand, some nanomaterials induce inflammation processes, especially by the generation of reactive oxygen species. Therefore, it is necessary to know and understand their effects in living systems and use surface modifications to prevent these negative effects. This contribution is focused on nanostructured scaffolds, providing a closer structural support approximation to native tissue architecture for cells and regulating cell proliferation, differentiation, and migration, which results in cartilage and bone healing and regeneration.

Tuning the biomimetic behavior of hybrid scaffolds for bone tissue engineering through surface modifications and drug immobilization

Bone defects arising from injury and/or disease are a common and debilitating clinical lesion. While the development of tissue microenvironments utilizing biomimetic constructs is an emerging approach for bone tissue engineering. In this context, bioactive glass nanoparticles (BGNPs) were embedded within polycaprolactone (PCL) scaffolds. The scaffolds exhibit an engineered unidirectional pore structure which are surface activated via oxygen plasma to allow immobilization of simvastatin (SIM) on the pore surface. Microscopic observation indicated the surface modification did not disturb the lamellar orientation of the pores improving the biomimetic formation of hydroxyapatite. Mathematically modelled release profiles reveal that the oxygen plasma pre-treatment can be utilized to modulate the release profile of SIM from the scaffolds. With the release mechanism controlled by the balance between the diffusion and erosion mechanisms. Computational modelling shows that Human Serum Albumin and Human α₂-macroglobulin can be utilized to increase SIM bioavailability for cells via a molecular docking mechanism. Cellular studies show positive MG-63 cell attachment and viability on optimized scaffolds with alkaline phosphatase activity enhanced along with enhanced expression of osteocalcoin biomarker.

Graphdiyne: from Preparation to Biomedical Applications

Graphdiyne(GDY) is a kind of two-dimensional carbon nanomaterial with specific configurations of sp and sp 2 carbon atoms. The key progress in the preparation and application of GDY is bringing carbon materials to a brand-new level. Here, the various properties and structures of GDY are introduced, including the existing strategies for the preparation and modification of GDY. In particular, GDY has gradually emerged in the field of life sciences with its unique properties and performance, therefore, the development of biomedical applications of GDY is further summarized. Finally, the challenges of GDY toward future biomedical applications are discussed.

Supramolecular Assembly of β-Cyclodextrin-Modified Polymer by Electrospinning with Sustained Antibacterial Activity

Supramolecular assembly loading drug as biomedical materials is a research hotspot. Herein, we reported a supramolecular electrospun assembly constructed via the hydrophobic and hydrogen bonding interaction. The obtained results showed that the assembly by supramolecular electrospinning not only increased the interactions of multiple antibacterial active species including antibiotics, cationic polymers, and silver to form a flexible membrane with good mechanical strength but also indicated the dual effects of rapid doxycycline and polyethyleneimine release as well as a sustained Ag release. Interestingly, the assembly showed not only good degradability but also a high bacteriostatic efficacy toward Escherichia coli (E. coli) up to 99.9%. More importantly, the in vivo wound healing assay indicated that the assembly could promote the healing of uninfected, E. coli-infected, and even methicillin-resistant staphylococcus aureus-infected wounds. The current research provides a novel approach to construct a supramolecular assembly by electrospinning mechanically induced strong noncovalent interaction.

In situ Irradiated XPS Investigation on S-Scheme TiO2 @ZnIn2 S4 Photocatalyst for Efficient Photocatalytic CO2 Reduction

Reasonable design of efficient hierarchical photocatalysts has gained significant attention. Herein, a step-scheme (S-scheme) core-shell TiO₂ @ZnIn₂ S₄ heterojunction is designed for photocatalytic CO₂ reduction. The optimized sample exhibits much higher CO₂ photoreduction conversion rates (the sum yield of CO, CH₃ OH, and CH₄ ) than the blank control, i.e., ZnIn₂ S₄ and TiO₂ . The improved photocatalytic performance can be attributed to the inhibited recombination of photogenerated charge carriers induced by S-scheme heterojunction. The improvement is also attributed to the large specific surface areas and abundant active sites. Meanwhile, S-scheme photogenerated charge transfer mechanism is testified by in situ irradiated X-ray photoelectron spectroscopy, work function calculation, and electron paramagnetic resonance measurements. This work provides an effective strategy for designing highly efficient heterojunction photocatalysts for conversion of solar fuels.

Effectiveness of photocatalysis of MMT-supported TiO2 and TiO2 nanotubes for rhodamine B degradation

The aim of this paper is to synthesize montmorillonite/TiO₂-nanoparticles (MMT/TiO₂ and montmorillonite/TiO₂-nanotubes (MMT/TiO_2-NTs) photocatalysts through a simple wet agitation method based on TiO₂ nanoparticles and MMT. They are likely to accumulate the effect of adsorption and photodegradation. Then, the photocatalysts are applied to degrade the rhodamine B in dye effluents. The structural characterizations of photocatalysts are investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The photocatalytic activities and effectiveness of photocatalysts are evaluated through rhodamine B degradation at different concentrations under dark and UV-C irradiation conditions. The results show that the synthesized TiO_2-NTs have an average tube diameter of 5 nm and a tube length at least about 110 nm, which are intercalated into MMT sheets in MMT/TiO_2-NTs photocatalyst. Meanwhile, TiO₂ nanoparticles are immobilized on the surface of MMT sheets in the MMT/TiO₂ photocatalyst. The photocatalytic effectiveness of rhodamine B degradation of TiO_2-NTs shows a significantly enhance compared to that of TiO₂ nanoparticles. However, photocatalytic performance of MMT/TiO_2-NTs is lower than that of MMT/TiO₂. The degradation effectiveness of MMT/TiO₂ photocatalyst reaches to 100% for 3 ppm and 90% at 10 ppm of rhodamine B, while these values are 97.5% and 85.5%, respectively, recorded for MMT/TiO_2-NTs.

Fabrication of AQ2S/GR composite photosensitizer for the simulated solar light-driven degradation of sulfapyridine

Chlorination has been intensively investigated for use in water disinfection and pollutant elimination due to its efficacy and convenience; however, the generation and transportation of chlorine and hypochlorite are energy-consuming and complicated. In this study, a novel binary photosensitizer consisting of anthraquinone-2-sulfonate (AQ2S) and graphene was synthesized via a π-π stack adsorption method; this compound could allow for the chlorination of organic pollutants using on-site chlorine generation. In this photosensitive degradation process, sulfapyridine (SPY) was selected as a model pollutant and was decomposed by the reactive species (Cl2 •-, Cl• and O2 •-) generated during the photosensitive oxidation of chloride. The synthesized AQ2S/graphene exhibited superior activity, and the degradation rate of SPY was over 90 % after 12 h of visible light irradiation with a kinetic constant of 0.2034h-1. Results show that 20 mg AQ2S/GR at a 21 % weight percentage of AQ2S in a pH 7 SPY solution with 1 mol/L Cl- achieved the highest kinetics rate at 0.353 h-1. Free radical trapping experiments demonstrated that Cl2 •- and O2 •- were the dominant species involved in SPY decomposition under solar light. The reusability and stability of this composite were verified by conducting a cycle experiment over five successive runs. The capacity of photodegradation still remained over 90 % after these 5 runs. The current study provides an energy-efficient and simple-operational approach for water phase SPY control.

Surface Design for Antibacterial Materials: From Fundamentals to Advanced Strategies

Healthcare-acquired infections as well as increasing antimicrobial resistance have become an urgent global challenge, thus smart alternative solutions are needed to tackle bacterial infections. Antibacterial materials in biomedical applications and hospital hygiene have attracted great interest, in particular, the emergence of surface design strategies offer an effective alternative to antibiotics, thereby preventing the possible development of bacterial resistance. In this review, recent progress on advanced surface modifications to prevent bacterial infections are addressed comprehensively, starting with the key factors against bacterial adhesion, followed by varying strategies that can inhibit biofilm formation effectively. Furthermore, "super antibacterial systems" through pre-treatment defense and targeted bactericidal system, are proposed with increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies to resist healthcare-associated infections are discussed, with promising prospects of developing novel antimicrobial materials.

Dental Implant Nano-Engineering: Advances, Limitations and Future Directions

Titanium (Ti) and its alloys offer favorable biocompatibility, mechanical properties and corrosion resistance, which makes them an ideal material choice for dental implants. However, the long-term success of Ti-based dental implants may be challenged due to implant-related infections and inadequate osseointegration. With the development of nanotechnology, nanoscale modifications and the application of nanomaterials have become key areas of focus for research on dental implants. Surface modifications and the use of various coatings, as well as the development of the controlled release of antibiotics or proteins, have improved the osseointegration and soft-tissue integration of dental implants, as well as their antibacterial and immunomodulatory functions. This review introduces recent nano-engineering technologies and materials used in topographical modifications and surface coatings of Ti-based dental implants. These advances are discussed and detailed, including an evaluation of the evidence of their biocompatibility, toxicity, antimicrobial activities and in-vivo performances. The comparison between these attempts at nano-engineering reveals that there are still research gaps that must be addressed towards their clinical translation. For instance, customized three-dimensional printing technology and stimuli-responsive, multi-functional and time-programmable implant surfaces holds great promise to advance this field. Furthermore, long-term in vivo studies under physiological conditions are required to ensure the clinical application of nanomaterial-modified dental implants.

Osteoinductive and antimicrobial mechanisms of graphene-based materials for enhancing bone tissue engineering

Graphene-based materials (GMs) have great application prospects in bone tissue engineering due to their osteoinductive ability and antimicrobial activity. GMs induce osteogenic differentiation through several mechanisms and pathways in bone tissue engineering. First of all, the surface and high hardness of the porous folds of graphene or graphene oxide (GO) can generate mechanical stimulation to initiate a cascade of reactions that promote osteogenic differentiation without any chemical inducers. In addition, change of the extracellular matrix (ECM), regulation of macrophage polarization, the oncostatin M (OSM) signaling pathway, the MAPK signaling pathway, the BMP signaling pathway, the Wnt/β-catenin signaling pathway, and other pathways are involved in GMs' regulation of osteogenesis. In bone tissue engineering, GMs prevent the formation of microbial biofilms mainly through preventing microbial adhesion and killing them. The former is mainly achieved by reducing surface free energy (SFE) and increasing hydrophobicity. The latter mainly includes oxidative stress and photothermal/photodynamic effects. Graphene and its derivatives (GDs) are mainly combined with bioactive ceramic materials, metal materials and macromolecular polymers to play an antimicrobial effect in bone tissue engineering. Concentration, number of layers, and type of GDs often affect the antimicrobial activity of GMs. In this paper, we reviewed relevant osteoinductive and antimicrobial mechanisms of GMs and their applications in bone tissue engineering.

Microdroplet confined assembly enabling the scalable synthesis of titania supported ultrasmall low-valent copper catalysts for efficient photocatalytic activation of peroxymonosulfate

The synthesis of highly dispersed low-valent copper catalysts is very challenging because they are prone to oxidation and sintering. Herein, scalable synthesis of ultrafine Cu(0)/Cu(i) catalysts supported on mesoporous titania microspheres is enabled by a one-step microdroplet confined assembly method. The extremely fast solute assembly in the microdroplet induces excellent metal precursor dispersion, reduces sol-gel crosslinking, and creates wrinkled microspheres with surface crusts and hollow cavities. This structural architecture allows the generation of an inner reductive gas environment during calcination in air to reduce Cu(ii) and create oxygen vacancy (O_V) sites in titania. The obtained catalysts exhibit excellent performance in the photocatalytic activation of peroxymonosulfate (PMS) for pollutant degradation. The Cu(0) species with a surface plasmon resonance effect and O_V-rich anatase facilitate efficient solar light utilization and charge separation. The intimate interface between Cu(i)/Cu(0) and anatase enables fast electron transfer and timely copper redox cycling to promote the activation of PMS.

TiO2/Chlorophyll S-Scheme Composite Photocatalyst with Improved Photocatalytic Bactericidal Performance

Step-scheme (S-scheme) photocatalysts have been proposed for highly efficient charge separation and strong redox activity in the photocatalysis field. Here, we reported a facile strategy to obtain the S-scheme heterojunction composite TiO₂/chlorophyll (Chl). The S-scheme heterojunction enables the significant improvement of electron transfer efficiency at the interfacial heterojunction of TiO₂/Chl. Also, the lifted conduction band and valence band of TiO₂/Chl resulted in more than 1.61 times generation of reactive oxidizing species, compared to that of bare TiO₂. In addition, TiO₂/Chl was applied as a photocatalytic bactericidal material to fabricate commercial masks for prolonged life span of the mask. The TiO₂/Chl-coated mask filter exhibited excellent bactericidal effect on Escherichia coli under light illumination (2.94 × 10⁷ cfu E. coli were killed by 1 cm^-2 coated mask filters within illumination of 3 h), while commercial mask filters showed no bactericidal effect. After three circulation-sterilization tests, the TiO₂/Chl-made mask filter maintained the initial bactericidal effect, which greatly extended the life span of the mask that presents a promising strategy to alleviate the supply stress of masks.

Sunlight-Activatable ROS Generator for Cell Death Using TiO2/c-Si Microwires

Solar-driven reactive oxygen species (ROS) generation is an attractive disinfection technique for cell death and water purification. However, most photocatalysts require high stability in the water environment and the production of ROS with a sufficient amount and diffusion length to damage pathogens. Here, a ROS generation system was developed consisting of tapered crystalline silicon microwires coated with anatase titanium dioxide for a conformal junction. The system effectively absorbed >95% of sunlight over 300-1100 nm, resulting in effective ROS generation. The system was designed to produce various ROS species, but a logistic regression analysis with cellular survival data revealed that the diffusion length of the ROS is ∼9 μm, implying that the most dominant species causing cell damage is H₂O₂. Surprisingly, a quantitative analysis showed that only 15 min of light irradiation on the system would catalyze a local bactericidal effect comparable to the conventional germicidal level of H₂O₂ (∼3 mM).

Antimicrobial TiO2 nanocomposite coatings for surfaces, dental and orthopaedic implants

Engineering of self-disinfecting surfaces to constrain the spread of SARS-CoV-2 is a challenging task for the scientific community because the human coronavirus spreads through respiratory droplets. Titania (TiO₂) nanocomposite antimicrobial coatings is one of the ideal remedies to disinfect pathogens (virus, bacteria, fungi) from common surfaces under light illumination. The photocatalytic disinfection efficiency of recent TiO₂ nanocomposite antimicrobial coatings for surfaces, dental and orthopaedic implants are emphasized in this review. Mostly, inorganic metals (e.g. copper (Cu), silver (Ag), manganese (Mn), etc), non-metals (e.g. fluorine (F), calcium (Ca), phosphorus (P)) and two-dimensional materials (e.g. MXenes, MOF, graphdiyne) were incorporated with TiO₂ to regulate the charge transfer mechanism, surface porosity, crystallinity, and the microbial disinfection efficiency. The antimicrobial activity of TiO₂ coatings was evaluated against the most crucial pathogenic microbes such as Escherichia coli, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Legionella pneumophila, Staphylococcus aureus, Streptococcus mutans, T2 bacteriophage, H1N1, HCoV-NL63, vesicular stomatitis virus, bovine coronavirus. Silane functionalizing agents and polymers were used to coat the titanium (Ti) metal implants to introduce superhydrophobic features to avoid microbial adhesion. TiO₂ nanocomposite coatings in dental and orthopaedic metal implants disclosed exceptional bio-corrosion resistance, durability, biocompatibility, bone-formation capability, and long-term antimicrobial efficiency. Moreover, the commercial trend, techno-economics, challenges, and prospects of antimicrobial nanocomposite coatings are also discussed briefly.

Prospects of Synthesized Magnetic TiO2-Based Membranes for Wastewater Treatment: A Review

Global accessibility to clean water has stressed the need to develop advanced technologies for the removal of toxic organic and inorganic pollutants and pathogens from wastewater to meet stringent discharge water quality limits. Conventionally, the high separation efficiencies, relative low costs, small footprint, and ease of operation associated with integrated photocatalytic-membrane (IPM) technologies are gaining an all-inclusive attention. Conversely, photocatalysis and membrane technologies face some degree of setbacks, which limit their worldwide application in wastewater settings for the treatment of emerging contaminants. Therefore, this review elucidated titanium dioxide (TiO2), based on its unique properties (low cost, non-toxicity, biocompatibility, and high chemical stability), to have great potential in engineering photocatalytic-based membranes for reclamation of wastewater for re-use. The environmental pathway of TiO2 nanoparticles, membranes and configuration types, modification process, characteristics, and applications of IPMs in water settings are discussed. Future research and prospects of magnetized TiO2-based membrane technology is highlighted as a viable water purification technology to mitigate fouling in the membrane process and photocatalyst recoverability. In addition, exploring life cycle assessment research would also aid in utilizing the concept and pressing for large-scale application of this technology.

Deciphering Single-Bacterium Adhesion Behavior Modulated by Extracellular Electron Transfer

For bacterial adhesion and biofilm formation, a thorough understanding of the mechanism and effective modulating is lacking due to the complex extracellular electron transfer (EET) at bacteria-surface interfaces. Here, we explore the adhesion behavior of a model electroactive bacteria under various metabolic conditions by an integrated electrochemical single-cell force microscopy system. A nonlinear model between bacterial adhesion force and electric field intensity is established, which provides a theoretical foundation for precise tuning of bacterial adhesion strength by the surface potential and the direction and flux of electron flow. In particular, based on quantitative analyses with equivalent charge distribution modeling and wormlike chain numerical simulations, it is demonstrated that the chain conformation and unfolding events of outer membrane appendages are dominantly impacted by the dynamic bacterial EET processes. This reveals how the anisotropy of bacterial conductive structure can translate into the desired adhesion behavior in different scenarios.

A green electrolysis of silver-decorated MoS2 nanocomposite with an enhanced antibacterial effect and low cytotoxicity

To tackle the devastating microbial infections for the public health, a continuous search for effective and safe nanobiocides based on their prominent nanoscale effects has been extensively explored during past decades. In this study, a green electrolysis method was employed to synthesize silver-doped molybdenum sulfide (Ag@MoS₂) composite materials. The obtained nanocomposites exhibited a sheet-like structure with a large specific surface area, which contributed to the efficient loading and refined distribution of silver nanoparticles. G^- E. coli and G ⁺ S. aureus were used as model bacteria for the antibacterial test, which revealed enhanced antibacterial activity of produced nanocomposites with an identified destructive effect on preformed biofilms. It was found that within 72 hour incubation, 20 μg mL^-1 Ag@MoS₂ was sufficient to inhibit the growth of E. coli and S. aureus without visible colony formation, pointing to a desirable long-term antibacterial activity. Further a mechanistic antibiosis study of Ag@MoS₂ indicated the involvement of a generation of reactive oxygen species. Notably, owing to the well-distributed silver nanoparticles on the nontoxic MoS₂ nanosheet, the cytotoxicity evaluation results revealed that produced nanocomposites exhibited negligible toxicity to mammalian cells, and thereby held promising potential for biomedical applications.

Graphdiyne Based Ternary GD-CuI-NiTiO3 S-Scheme Heterjunction Photocatalyst for Hydrogen Evolution

As the demand of fossil fuels continues to expand, hydrogen energy is considered a promising alternative energy. In this work, the NiTiO₃-CuI-GD ternary system was successfully constructed based on morphology modulation and energy band structure design. First, the one-pot method was used to cleverly embed the cubes CuI in the stacked graphdiyne (GD) to prepare the hybrid CuI-GD, and CuI-GD was anchored on the surface of NiTiO₃ by simple physical stirring. The unique spatial arrangement of the composite catalyst was utilized to improve the hydrogen production activity under light. Second, to combine various characterization tools and energy band structures, we proposed an step-scheme (S-scheme) heterojunction photocatalytic reaction mechanism, among them, the tubular NiTiO₃ formed by the self-assembled of nanoparticles provided sufficient sites for the anchoring of CuI-GD, and the thin layer GD acted as an electron acceptor to capture a large number of electrons with the help of the conjugated carbon network; cubes CuI could consume holes in the reaction system; the loading of CuI-GD greatly improved the oxidation and reduction ability of the whole catalytic system. The S-scheme heterojunction accelerated the transfer of carriers and improved the separation efficiency. The experiment provides a new insight into the construction of an efficient and eco-friendly multicatalytic system.

An Inorganic/Organic S-Scheme Heterojunction H2 -Production Photocatalyst and its Charge Transfer Mechanism

Inspired by natural photosynthesis, constructing inorganic/organic heterojunctions is regarded as an effective strategy to design high-efficiency photocatalysts. Herein, a step (S)-scheme heterojunction photocatalyst is prepared by in situ growth of an inorganic semiconductor firmly on an organic semiconductor. A new pyrene-based conjugated polymer, pyrene-alt-triphenylamine (PT), is synthesized via the typical Suzuki-Miyaura reactions, and then employed as a substrate to anchor CdS nanocrystals. The optimized CdS/PT composite, coupling 2 wt% PT with CdS, exhibits a robust H₂ evolution rate of 9.28 mmol h^-1 g^-1 with continuous release of H₂ bubbles, as well as a high apparent quantum efficiency of 24.3%, which is ≈8 times that of pure CdS. The S-scheme charge transfer mechanism between PT and CdS, is systematically demonstrated by photoirradiated Kelvin probe measurement and in situ irradiated X-ray photoelectron spectroscopy analyses. This work provides a protocol for preparing specific S-scheme heterojunction photocatalysts on the basis of inorganic/organic coupling.

Visible light-induced antibacterial and osteogenic cell proliferation properties of hydrogenated TiO2 nanotubes/Ti foil composite

We successfully fabricated the hydrogenated TiO₂ nanotubes/Ti foil (H-TNTs/f-Ti) composite via one-step anodization and two-step annealing. H-TNTs/f-Ti composite had a higher visible light-induced photoelectric response and more hydroxyl functional groups compared with Ti foil and unmodified TiO₂ nanotubes/Ti foil composite, which contributed to limiting the proliferation of Streptococcus mutans and Porphyromonas gingivalis, promoting the proliferation of MC3T3-E1 cell on the hydroxylated surface, and improving the biocompatibility with osteogenic cells. Our study provides a simple and effective method for significantly improving dental implant efficacy.

Near-Infrared-Responsive Photocatalysts

Broadening the absorption of light to the near-infrared (NIR) region is important in photocatalysis to achieve efficient solar-to-fuel conversion. NIR-responsive photocatalysts that can utilize diffusive solar energy are attractive for alleviating the energy crisis and environmental pollution. Over the past few years, considerable progress on the component and structural design of NIR-responsive photocatalysts have been reported. This study aims to systematically summarize recent progress toward the material design and mechanism optimization of NIR-responsive photocatalysts in this area. Depending on the main strategies for harvesting NIR photons, NIR-responsive photocatalysts can be categorized as direct NIR-light photocatalysts, indirect NIR-light photocatalysts, and photothermal photocatalysts. Furthermore, the construction and application of different NIR-responsive photocatalytic systems are summarized. Conclusions and perspectives are presented to further explore the potential of NIR-responsive photocatalysts in this field.

Superior visible light antimicrobial performance of facet engineered cobalt doped TiO2 mesocrystals in pathogenic bacterium and fungi

Pristine and Co-doped TiO2 mesocrystals have been synthesized via a simple sol-gel method and their antimicrobial activity has been investigated. The antimicrobial performance was evaluated in terms of zone of inhibition, minimum inhibitory concentration (MIC), antibiofilm activity, and effect of UV illumination in liquid media. The Co-doped TiO2 mesocrystals showed very promising MIC of 0.390 μg/mL and 0.781 μg/mL for P. mirabilis and P. mirabilis, respectively. Additionally, the material showed an MIC of 12.5 μg/mL against C. albicans, suggesting its use as antifungal agent. Upon the addition of 10.0 µg/mL of Co-doped TiO2 mesocrystals, the biofilm inhibition% reaches 84.43% for P. aeruginosa, 78.58% for P. mirabilis, and 77.81% for S. typhi, which can be ascribed to the created active oxygen species that decompose the tested microbial cells upon illumination. Thus the fabricated Co-doped TiO2 mesocrystals exhibit sufficient antimicrobial features under visible light, qualifying them for use as antimicrobial agents against pathogenic bacteria and fungi and subsequently inhibit their hazardous effects.

Antibacterial biomaterials in bone tissue engineering

Bone infection is a devastating disease characterized by recurrence, drug-resistance, and high morbidity, that has prompted clinicians and scientists to develop novel approaches to combat it. Currently, although numerous biomaterials that possess excellent biocompatibility, biodegradability, porosity, and mechanical strength have been developed, their lack of effective antibacterial ability substantially limits bone-defect treatment efficacy. There is, accordingly, a pressing need to design antibacterial biomaterials for effective bone-infection prevention and treatment. This review focuses on antibacterial biomaterials and strategies; it presents recently reported biomaterials, including antibacterial implants, antibacterial scaffolds, antibacterial hydrogels, and antibacterial bone cement types, and aims to provide an overview of these antibacterial materials for application in biomedicine. The antibacterial mechanisms of these materials are discussed as well.

Superior antibacterial activity of sulfur-doped g-C3N4 nanosheets dispersed by Tetrastigma hemsleyanum Diels & Gilg's polysaccharides-3 solution

Bacterial resistance has become a serious global health issue over the past decades due to the misuse and abuse of antibiotics. The development of effective antibacterial drugs with a new antibacterial mechanism is thus very critical. At present, there are many reports on the antibacterial properties and mechanisms of two-dimensional materials. Currently, the modification of g-C₃N₄ materials, as widely used two-dimensional materials, has become a key step in extending their potential applications in the field of antimicrobial therapy. In the present work, we prepared sulfur-doped g-C₃N₄ nanosheets (SCNNSs), which have good water dispersibility and sharp tips. The electrostatic interaction of SCNNSs with Tetrastigma hemsleyanum Diels & Gilg's polysaccharide-3 (THDG-3) provides a new strategy that can improve the killing efficiency of SCNNSs. In addition, THDG-3 can rapidly inhibit bacterial proliferation in the early stage of administration. Combined with the antibacterial activity of the SCNNSs, TPS/SCNNSs can inhibit bacteria for a long time. Scanning electron microscopy (SEM) observation of Escherichia coli (E. coli) after administration of the materials revealed that the bacterial cells were ruptured and their intracellular contents were completely separated from the cell membrane. Therefore, we speculate that the bactericidal mechanism of the TPS/SCNNSs probably involves cell membrane damage. In summary, TPS/SCNNSs achieve fast, long-term, dual-function bacteriostatic properties.

Recent advances in pH-responsive nanomaterials for anti-infective therapy

The design and synthesis of pH-responsive antibacterial nanomaterials and their applications in anti-infective therapy.