Bactericidal activity and recovery effect of hydroxyl radicals generated by ultraviolet irradiation and silver ion application on an infected titanium surface

Synergistic Bactericidal Effect of Zn2+ Ions and Reactive Oxygen Species Generated in Response to Either UV or X-ray Irradiation of Zn-Doped Plasma Electrolytic Oxidation TiO2 Coatings

Zn-containing TiO2-based coatings with Na, Ca, Si, and K additives were obtained by plasma electrolytic oxidation (PEO) of Ti in order to achieve an effective and broad bactericidal protection without compromising biocompatibility. A protocol has been developed for cleaning the coating surface from electrolyte residues, ensuring the preservation of the microstructure and composition of the surface layer. Using high-resolution transmission electron microscopy, three characteristic microstructural zones in the PEO-Zn coating are well documented: zone 1 with a TiO2-based nanocrystalline structure, zone 2 with an amorphous structure, and zone 3 around pores with an amorphous-nanocrystalline structure. The excellent cytocompatibility of PEO-Zn samples was confirmed by three different methods: monitoring the proliferation of MC3T3-E1 cells, assessing the viability of sheep osteoblast cells using calcein-AM staining and fluorescence microscopy, and incubation with spheroids based on primary osteoblast cells and mouse embryonic fibroblast NIH3T3 cells. The PEO-Zn coatings absorb >60% of the incident light over the UV and Vis-NIR spectral ranges. After 24 h, the PEO-Zn coatings completely inactivate four types of strains: Gram-positive Staphylococcus aureus CSA154 and ATCC29213 and Gram-negative Escherichia coli K261 and U20, and also prevent E. coli U20 and K261 biofilm formation. The superior antibacterial activity is associated with the synergistic effect of Zn2+ ions in safe concentration and reactive oxygen species (ROS) generated in response to either UV irradiation or soft short-term X-ray irradiation. The X-ray irradiation-induced ROS formation by a PEO coating is reported for the first time. The enhanced bactericidal activity after X-ray irradiation compared to UV illumination is attributed to the more intense ROS generation in the first few hours. The results obtained significantly expand the possibilities of using PEO coatings on the surfaces of titanium implants.

Innovative Anodic Treatment to Obtain Stable Metallic Silver Micropatches on TiO2 Nanotubes: Structural, Electrochemical, and Photochemical Properties

Electrochemical modification of the Ti surface to obtain TiO2 nanotubes (NT-Ti) has been proposed to enhance osseointegration in medical applications. However, susceptibility to microbial adhesion, linked to biomaterial-associated infections, and the high TiO2 band gap energy, which allows light absorption almost exclusively in the ultraviolet (UV) region, limit its applications. Modifying the TiO2 semiconductor with metals such as Ag has been suggested both for antimicrobial purposes and for absorbing light in the visible region. The formation of NT-Ti with Ag micropatches (Ag-NT-Ti) is pursued with the objective of enhancing the stability of the deposits and preventing cytotoxic levels of Ag cellular uptake. The innovative process proposed here involves immersing NT-Ti in a AgNO3 solution as the initial step. Diverging from previously reported electrochemical methods, this process incorporates anodization within the TiO2 oxide formation region instead of cathodic reduction generally employed by other researchers. The final step encompasses an annealing treatment. The treatments result in the in situ Ag1+ reduction and formation of stable and active micropatches of metallic Ag on the NT-Ti surface. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman, diffuse reflectance spectroscopy (DRS), wettability assessment, and electrochemical characterizations were conducted to evaluate the modified surfaces. The well-known properties of NT-Ti surfaces were enhanced, leading to improved photocatalytic activity across both visible and UV regions, significant stability against detachment, and controlled release of Ag1+ for promising antimicrobial effects.

Copper: DNA extraction and solid phase detection agent for all-in-one molecular diagnostic device coupled with isothermal amplification

In this study, an all-in-one poly(methyl methacrylate) (PMMA) device integrating two novel techniques - DNA extraction employing a CuSO₄/H₂O₂ system and DNA detection utilizing solid phase copper tape - coupled with loop-mediated isothermal amplification (LAMP) is developed for on-site pathogen detection. The CuSO₄/H₂O₂ system, also known as Fenton-like reaction, is used to produce hydroxyl radicals, which can disrupt bacterial membranes via lipid peroxidation and release DNA at room temperature. The released DNA is subsequently amplified by LAMP reaction. The acidic environment resulting from the production of hydrogen ions in the presence of target DNA in the LAMP reaction can stimulate the color change on copper tape due to the corrosion, while the innate alkaline environment in a negative sample not containing target DNA cannot stimulate the corrosion. The fabricated PMMA device integrates all the functionalities necessary for molecular diagnostics such as DNA extraction, amplification, and detection, and a carbon paste-based heater is fabricated for LAMP reaction. Using the PMMA device, Enterococcus faecium was detected as low as 4.67 × 10² CFU/mL within 90 min. E. faecium spiked in milk was successfully detected using the all-in-one PMMA device. The equipment-free techniques for decentralized diagnostics and naked-eye readout of results coupled with the portable heater serves as a promising solution for point-of-care testing particularly in a resource-limited environment.

Does Ultraviolet Radiation Exhibit Antimicrobial Effect against Oral Pathogens Attached on Various Dental Implant Surfaces? A Systematic Review

Background: Dental implant therapy is currently identified as the most effective treatment for edentulous patient. However, peri-implant inflammations were found to be one of the most common complications that leads to the loss and failure of dental implantation. Ultraviolet (UV) radiation has been proposed to enhance bone integration and reduce bacterial attachment. In this study, we aimed to systematically review the current evidence regarding the antimicrobial effect of UV on different dental implant surfaces. Methods: Five databases including PubMed, Scopus, Web of science, VHL, and Cochran Library were searched to retrieve relevant articles. All original reports that examined the effect of the application of UV radiation on dental implants were included in our study. Results: A total of 16 in vitro studies were included in this systematic review. Polymethyl methacrylate UV radiation has induced a significant decrease in bacterial survival in PMMA materials, with an increased effect by modification with 2.5% and 5% TiO₂ nanotubes. UV-C showed a superior effect to UV-A in reducing bacterial attachment and accumulation. UV wavelength of 265 and 285 nm showed powerful bactericidal effects. UV of 365 nm for 24 h had the highest inhibition of bacterial growth in ZnO coated magnesium alloys. In UV-irradiated commercially pure titanium surfaces treated with plasma electrolytic oxidation, silver ion application, heat or alkali had shown significant higher bactericidal effect vs non-irradiated treated surfaces than the treatment with any of them alone. UVC and gamma-ray irradiation increased the hydrophilicity of zirconia surface, compared to the dry heat. Conclusion: UV radiation on Ti surfaces exhibited significant antibacterial effects demonstrated through the reduction in bacterial attachment and biofilm formation with suppression of bacterial cells growth. Combination of UV and treated surfaces with alkali, plasma electrolytic oxidation, silver ion application or heat enhance the overall photocatalytic antimicrobial effect.

Optical clearing of tissues: Issues of antimicrobial phototherapy and drug delivery

This review presents principles and novelties in the field of tissue optical clearing (TOC) technology, as well as application for optical monitoring of drug delivery and effective antimicrobial phototherapy. TOC is based on altering the optical properties of tissue through the introduction of immersion optical cleaning agents (OCA), which impregnate the tissue of interest. We also analyze various methods and kinetics of delivery of photodynamic agents, nanoantibiotics and their mixtures with OCAs into the tissue depth in the context of antimicrobial and antifungal phototherapy. In vitro and in vivo studies of antimicrobial phototherapies, such as photodynamic, photothermal plasmonic and photocatalytic, are summarized, and the prospects of a new TOC technology for effective killing of pathogens are discussed.

Gene transfection achieved by utilizing antibacterial calcium phosphate nanoparticles for enhanced regenerative therapy

Protamine-coated multi-shell calcium phosphate (CaP) was developed as a non-viral vector for tissue regeneration therapy. CaP nanoparticles loaded with different amounts of plasmid DNA encoding bone morphogenetic protein 2 (BMP-2) and insulin-like growth factor 1 (IGF-1) were used to treat MC3T3E1 cells, and the yield of the released BMP-2 or IGF-1 was measured using ELISA 3 days later. Collagen scaffolds containing CaP nanoparticles were implanted into rat cranial bone defects, and BMP-2 and IGF-1 yields, bone formation, and bone mineral density enhancement were evaluated 28 days after gene transfer. The antibacterial effects of CaP nanoparticles against Streptococcus mutans and Aggregatibacter actinomycetemcomitans increased with an increase in the protamine dose, while they were lower for Staphylococcus aureus and Porphyromonas gingivalis. In the combination treatment with BMP-2 and IGF-1, the concentration ratio of BMP-2 and IGF-1 is an important factor affecting bone formation activity. The calcification activity and OCN mRNA of MC3T3E1 cells subjected to a BMP-2:IGF-1 concentration ratio of 1:4 was higher at 14 days. During gene transfection treatment, BMP-2 and IGF-1 were released simultaneously after gene transfer; the loaded dose of the plasmid DNA encoding IGF-1 did not impact the BMP-2 or IGF-1 yield or new bone formation ratio in vitro and in vivo. In conclusion, two growth factor-releasing systems were developed using an antibacterial gene transfer vector, and the relationship between the loaded plasmid DNA dose and resultant growth factor yield was determined in vitro and in vivo.

Boosting nanotoxicity to combat multidrug-resistant bacteria in pathophysiological environments

Nanomaterials are promising novel antibiotics, but often ineffective. We found that nanomaterial-bacteria complex formation occurred with various nanomaterials. The bactericidal activity of NMs strongly depends on their physical binding to (multidrug-resistant) bacteria. Nanomaterials' binding and antibiotic effect was reduced by various pathophysiological biomolecule coronas strongly inhibiting their antibiotic effects. We show from analytical to in vitro to in vivo that nanomaterial-based killing could be restored by acidic pH treatments. Here, complex formation of negatively-charged, plasma corona-covered, nanomaterials with bacteria was electrostatically enhanced by reducing bacteria's negative surface charge. Employing in vivo skin infection models, acidic pH-induced complex formation was critical to counteract Staphylococcus aureus infections by silver nanomaterials. We explain why nano-antibiotics show reduced activity and provide a clinically practical solution.