TiCaPCON-Supported Pt- and Fe-Based Nanoparticles and Related Antibacterial Activity

Structure-driven tuning of catalytic properties of core-shell nanostructures

The annual increase in demand for renewable energy is driving the development of catalysis-based technologies that generate, store and convert clean energy by splitting and forming chemical bonds. Thanks to efforts over the last two decades, great progress has been made in the use of core-shell nanostructures to improve the performance of metallic catalysts. The successful preparation and application of a large number of bimetallic core-shell nanocrystals demonstrates the wide range of possibilities they offer and suggests further advances in this field. Here, we have reviewed recent advances in the synthesis and study of core-shell nanostructures that are promising for catalysis. Particular attention has been paid to the structural tuning of the catalytic properties of core-shell nanostructures and to theoretical methods capable of describing their catalytic properties in order to efficiently search for new catalysts with desired properties. We have also identified the most promising areas of research in this field, in terms of experimental and theoretical studies, and in terms of promising materials to be studied.

X-ray and UV Irradiation-Induced Reactive Oxygen Species Mediated Antibacterial Activity in Fe and Pt Nanoparticle-Decorated Si-Doped TiCaCON Films

Bone implants with biocompatibility and the ability to biomineralize and suppress infection are in high demand. The occurrence of early infections after implant placement often leads to repeated surgical treatment due to the ineffectiveness of antibiotic therapy. Therefore, an extremely attractive solution to this problem would be the ability to initiate bacterial protection of the implant by an external influence. Here, we present a proof-of-concept study based on the generation of reactive oxygen species (ROS) by the implant surface in response to X-ray irradiation, including through a layer of 3 mm adipose tissue, providing bactericidal protection. The effect of UV and X-ray irradiation of the implant surface on the ROS formation and the associated bactericidal activity was compared. The focus of our study was light-sensitive Si-doped TiCaCON films decorated with Fe and Pt nanoparticles (NPs) with photoinduced antibacterial activity mediated by ROS. In the visible and infrared range of 300-1600 nm, the films absorb more than 60% of the incident light. The high light absorption capacity of TiO2/TiC and TiO2/TiN heterostructures was demonstrated by density functional theory calculations. After short-term (5-10 s) low-dose X-ray irradiation, the films generated significantly more ROS than after UV illumination for 1 h. The Fe/TiCaCON-Si films showed enhanced biomineralization capacity, superior cytocompatibility, and excellent antibacterial activity against multidrug-resistant hospital Escherichia coli U20 and K261 strains and methicillin-resistant Staphylococcus aureus MW2 strain. Our study clearly demonstrates that oxidized Fe NPs are a promising alternative to the widely used Ag NPs in antibacterial coatings, and X-rays can potentially be used in ROS-regulating therapy to suppress inflammation in case of postimplant complications.

Synthesis and antibacterial activities of Ag-TiO2/ZIF-8

In recent years, massive bacterial infections have led to human illness and death, reminding us of the urgent need to develop effective and long-lasting antimicrobial materials. In this paper, Ag-TiO2/ZIF-8 with good environmental friendliness and biological antibacterial activity was prepared by solvothermal method. The structure and morphology of the synthesized materials were characterized by XRD, FT-IR, SEM-EDS, TEM, XPS, and BET. To investigate the antibacterial activity of the synthesized samples, Escherichia coli and Bacillus subtilis were used as target bacteria for experimental studies of zone of inhibition, bacterial growth curves, minimum bactericidal concentration and antibacterial durability. The results demonstrated that 20 wt.%Ag-TiO2/ZIF-8 had the best bacteriostatic effect on E. coli and B. subtilis under dark and UV conditions compared to TiO2 and ZIF-8. Under the same conditions, the diameter of the inhibition circle of 20 wt% Ag-TiO2/ZIF-8 is 8.5-11.5 mm larger than that of its constituent material 4 wt% Ag-TiO2, with more obvious antibacterial effect and better antibacterial performance. It is also proposed that the excellent antibacterial activity of Ag-TiO2/ZIF-8 is due to the synergistic effect of Ag-TiO2 and ZIF-8 under UV light. In addition, the prepared material has good stability and durability with effective antimicrobial activity for more than 5 months.

Antibacterial Composite Material Based on Polyhydroxybutyrate and Zn-Doped Brushite Cement

A composite material based on electrospinning printed polyhydroxybutyrate fibers impregnated with brushite cement containing Zn substitution was developed for bone implant applications. Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy were applied for materials characterization. Soaking the composite in Ringer's solution led to the transformation of brushite into apatite phase, accompanied by the morphology changes of the material. The bending strength of the composite material was measured to be 3.1 ± 0.5 MPa. NCTC mouse fibroblast cells were used to demonstrate by means of the MTT test that the developed material was not cytotoxic. The behavior of the human dental pulp stem cells on the surface of the composite material investigated by the direct contact method was similar to the control. It was found that the developed Zn containing composite material possessed antibacterial properties, as testified by microbiology investigations against bacteria strains of Escherichia coli and Staphylococcus aureus. Thus, the developed composite material is promising for the treatment of damaged tissues with bacterial infection complications.

Multifunctional MoSe2 @MXene Heterostructure-Decorated Cellulose Fabric for Wearable Thermal Therapy

A booming demand for wearable electronic devices urges the development of multifunctional smart fabrics. However, it is still facing a challenge to fabricate multifunctional smart fabrics with satisfactory mechanical property, excellent Joule heating performance, highly efficient photothermal conversion, outstanding electromagnetic shielding effectiveness, and superior anti-bacterial capability. Here, a MoSe₂ @MXene heterostructure-based multifunctional cellulose fabric is fabricated by depositing MXene nanosheets onto cellulose fabric followed by a facile hydrothermal method to grow MoSe₂ nanoflakes on MXene layers. A low-voltage Joule heating therapy platform with rapid Joule heating response (up to 230 °C in 25 s at a supplied voltage of 4 V) and stable performance under repeated bending cycles (up to 1000 cycles) is realized. Besides, the multifunctional fabric also exhibits excellent photothermal performance (up to 130 °C upon irradiation for 25 s with a light intensity of 400 mW cm^-2 ), outstanding electromagnetic interference shielding effectiveness (37 dB), and excellent antibacterial performances (>90% anti-bacterial rate toward Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). This work offers an efficient avenue to fabricate multifunctional wearable thermal therapy devices for mobile healthcare and personal thermal management.

Ferric Chloride-Induced Synthesis of Silver Nanodisks with Considerable Activity for the Reduction of 4-Nitrophenol

Silver nanodisks (AgNDs) have been successfully synthesized by using ferric chloride as an auxiliary agent in the presence of polyvinylpyrrolidone and N,N-dimethylformamide as both a solvent and a reducing agent. The mass ratio of reactants, temperature, and time were demonstrated to be the key factors determining the morphology of the product, and the conversion of Fe3+/Fe2+ ions played an important role in increasing the ratio of silver nanosheets (AgNSs). As the reaction prolonged, the etching effect of Cl- ions on the tips of AgNSs became more and more obvious, which made the obtained typical polygonal AgNSs turn into AgNDs eventually. In addition, the prepared AgNDs exhibited a considerable catalytic activity in the reduction of 4-nitrophenol.

Biodegradable Nanohybrid Materials as Candidates for Self-Sanitizing Filters Aimed at Protection from SARS-CoV-2 in Public Areas

The COVID-19 pandemic has raised the problem of efficient, low-cost materials enabling the effective protection of people from viruses transmitted through the air or via surfaces. Nanofibers can be a great candidate for efficient air filtration due to their structure, although they cannot protect from viruses. In this work, we prepared a wide range of nanofibrous biodegradable samples containing Ag (up to 0.6 at.%) and Cu (up to 20.4 at.%) exhibiting various wettability. By adjusting the magnetron current (0.3 A) and implanter voltage (5 kV), the deposition of TiO2 and Ag+ implantation into PCL/PEO nanofibers was optimized in order to achieve implantation of Ag+ without damaging the nanofibrous structure of the PCL/PEO. The optimal conditions to implant silver were achieved for the PCL-Ti0.3-Ag-5kV sample. The coating of PCL nanofibers by a Cu layer was successfully realized by magnetron sputtering. The antiviral activity evaluated by widely used methodology involving the cultivation of VeroE6 cells was the highest for PCL-Cu and PCL-COOH, where the VeroE6 viability was 73.1 and 68.1%, respectively, which is significantly higher compared to SARS-CoV-2 samples without self-sanitizing (42.8%). Interestingly, the samples with implanted silver and TiO2 exhibited no antiviral effect. This difference between Cu and Ag containing nanofibers might be related to the different concentrations of ions released from the samples: 80 μg/L/day for Cu2+ versus 15 µg/L/day for Ag+. The high antiviral activity of PCL-Cu opens up an exciting opportunity to prepare low-cost self-sanitizing surfaces for anti-SARS-CoV-2 protection and can be essential for air filtration application and facemasks. The rough cost estimation for the production of a biodegradable nanohybrid PCL-Cu facemask revealed ~$0.28/piece, and the business case for the production of these facemasks would be highly positive, with an Internal Rate of Return of 34%.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

Transmembrane charge (ion/electron) transfer is essential for maintaining cellular homeostasis and is involved in many biological processes, from protein synthesis to embryonic development in organisms. Designing implant devices that can detect or regulate cellular transmembrane charge transfer is expected to sense and modulate the behaviors of host cells and tissues. Thus, charge transfer can be regarded as a bridge connecting living systems and human-made implantable devices. This review describes the mode and mechanism of charge transfer between organisms and nonliving materials, and summarizes the strategies to endow implants with charge-transfer regulating or monitoring abilities. Furthermore, three major charge-transfer controlling systems, including wired, self-activated, and stimuli-responsive biomedical implants, as well as the design principles and pivotal materials are systematically elaborated. The clinical challenges and the prospects for future development of these implant devices are also discussed.

Next-Generation Antibiotics, Bacteriophage Endolysins, and Nanomaterials for Combating Pathogens

This review presents various strategies to fight causative agents of infectious diseases. Species-specific programmable RNA-containing antibiotics open up new possibilities for creating next-generation of personalized drugs based on microbiome editing and can serve as a new tool for selective elimination of pathogenic bacterial species while keeping intact the rest of microbiota. Another promising approach in combating bacterial infections is genome editing using the CRISPR-Cas systems. Expanding knowledge on the molecular mechanisms of innate immunity has been actively used for developing new antimicrobials. However, obvious risks of using antibiotic adjuvants aimed at activation of the host immune system include development of the autoimmune response with subsequent organ damage. To avoid these risks, it is essential to elucidate action mechanisms of the specific ligands and signal molecules used as components of the hybrid antibiotics. Bacteriophage endolysins are also considered as effective antimicrobials against antibiotic-resistant bacteria, metabolically inactive persisters, and microbial biofilms. Despite significant advances in the design of implants with antibacterial properties, the problem of postoperative infections still remains. Different nanomodifications of the implant surface have been designed to reduce bacterial contamination. Here, we review bactericidal, fungicidal, and immunomodulating properties of compounds used for the implant surface nanomodifications, such as silver, boron nitride nanomaterials, nanofibers, and nanogalvanic materials.

Antibacterial Activity of Polyvinyl Alcohol/WO3 Films Assisted by Near-Infrared Light and Its Application in Freshness Monitoring

Nowadays, films with antibacterial activity and applied for freshness monitoring by colorimetric response have been drawing growing attention in food packaging. However, the development of versatile antibacterial and colorimetric agents is still highly desirable. Herein, WO₃ nanorods are incorporated in a polyvinyl alcohol (PVA) matrix to develop a novel composite film with photothermal antibacterial activity and freshness monitoring faculty. The interaction between WO₃ nanorods and PVA is due to hydrogen bonds. Compared with the PVA film, the presence of WO₃ nanorods can significantly enhance the mechanical and barrier properties; typically, the target film (WO₃/PVA)₄ shows an increase in tensile strength by 52.7% and Young's modulus by 400.0% and a decrease in oxygen permeability by 72.4% and water vapor permeability by 66.9%. The films demonstrate a WO₃ content-dependent antibacterial activity. Under irradiation of near-infrared light (NIR808), the synergistic effect of physical damage, oxidative stress, and temperature increase markedly improves the antibacterial activity of (WO₃/PVA)₄, showing an antibacterial efficiency of ∼90% against Escherichia coli or beyond 90% against Staphylococcus aureus. The incorporated WO₃ nanorods demonstrate lower cytotoxicity toward the model cells of human colon cancer cell line HT-29. The (WO₃/PVA)₄ film exhibits colorimetric response to H₂S and can also be used for pork freshness monitoring as an indicator.

Pristine and Antibiotic-Loaded Nanosheets/Nanoneedles-Based Boron Nitride Films as a Promising Platform to Suppress Bacterial and Fungal Infections

In recent years, bacteria inactivation during their direct physical contact with surface nanotopography has become one of the promising strategies for fighting infection. Contact-killing ability has been reported for several nanostructured surfaces, e.g., black silicon, carbon nanotubes, zinc oxide nanorods, and copper oxide nanosheets. Herein, we demonstrate that Gram-negative antibiotic-resistant Escherichia coli (E. coli) bacteria are killed as a result of their physical destruction while contacting nanostructured h-BN surfaces. BN films, made of spherical nanoparticles formed by numerous nanosheets and nanoneedles with a thickness <15 nm, have been obtained through a reaction of ammonia with amorphous boron. The contact-killing bactericidal effect of BN nanostructures has been compared with a toxic effect of gentamicin released from them. For a wider protection against bacterial and fungal infection, the films have been saturated with a mixture of gentamicin and amphotericin B. Such BN films demonstrate a high antibiotic/antimycotic agent loading capacity and a fast initial and sustained release of therapeutic agents for 170-260 h depending on the loaded dose. The pristine BN films possess high antibacterial activity against E. coli K-261 strain at their initial concentration of 10⁴ cells/mL, attaining >99% inactivation of colony forming units after 24 h, same as gentamicin-loaded (150 μg/cm²) BN sample. The BN films loaded with a mixture of gentamicin (150 and 300 μg/cm²) and amphotericin B (100 μg/cm²) effectively inhibit the growth of E. coli K-261 and Neurospora crassa strains. During immersion in the normal saline solution, the BN film generates reactive oxygen species (ROS), which can lead to accelerated oxidative stress at the site of physical cell damage. The obtained results are valuable for further development of nanostructured surfaces having contact killing, ROS, and biocide release abilities.