Photocatalysis with anatase Titanium dioxide (TiO 2 ) under ultraviolet A (UVA) has a well recognized bactericidal effect. There have been a few reports, however, on the effects of photocatalysis on bio-implant-related infections. The purpose of present study was to evaluate the photocatalytic bactericidal effects of anatase TiO 2 on Staphylococcus aureus (S. aureus) associated with surgical site infections.TiO 2 films were synthesized on commercially pure titanium substrates and SUS316 stainless steel using a plasma source ion implantation method followed by annealing. The chemical composition of the surface layers was determined using GXRD and XPS. The disks were seeded with cultured S. aureus and exposed to UVA illumination from black light. The bactericidal effect of the TiO 2 films was evaluated by counting the survived colonies statistically.A structural gradient anatase type TiO 2 layer formed on all substrates. The viability of the bacteria on the photocatalytic TiO 2 film coated on titanium was suppressed to 7.0% at 30 minutes and 5.5% at 45 minutes, whereas that on a similarly coated stainless steel was suppressed to 45.8% at 30 minute and 28.6% at 45 minutes (ANOVA: p < 0.05). Complete bacterial inactivation was achieved after 90 minutes on titanium and after 60 minutes on stainless steel. The photocatalytic bactericidal effect of TiO 2 is useful for sterilizing the contaminated surfaces of bioimplants.
When ultraviolet (UV) light comes into contact with titanium dioxide (TiO 2 ), a variety of free radicals are released to provide a potent oxidizing power. Few reports are available, however, evaluating the bactericidal effects of TiO 2 particle under UV light and fluorescent light (FL) in the same line of research for clinical applications. In the present study, we set out to evaluate the in vitro photocatalytic bactericidal effects on Staphylococcus aureus, which is one of the most common pathogens of infectious disease, in an aqueous system of TiO 2 particles irradiated by UV and FL. A TiO 2 particle mixture containing 0.019 mg/ml of TiO 2 was prepared. A bacterial solution was added dropwise to the mixture, and the resulting product was irradiated by UV or FL light. The colony-forming units were counted and the bacterial survival rate was calculated. Control samples maintained a relatively high bacterial survival rate. In the TiO 2 mixture group, however, the bacterial survival rate decreased steadily, reaching 9.4% after 60 min of exposure to UV light and 10.9% after 60 min of FL irradiation. Distributing the TiO 2 particles in a water mixture produces highly efficient light absorption and enables greater and more frequent adhesion with bacteria, allowing a high degree of photocatalytic antibacterial action. Although the quantity was inferior to UV, our TiO 2 particles were able to show effective bactericidal activity even under FL. The TiO 2 particle mixture is expected to prove effective in preventing postoperative infection.
Traditional titanium dioxide (TiO 2 ) has photocatalytic bactericidal properties only under ultraviolet (UV) irradiation, which restricts its use in clinical treatment regimens. In this study, we evaluated the photocatalytic bactericidal effects of an aqueous system of TiO 2 particles irradiated by fluorescent light (FL) on Staphylococcus aureus. A TiO 2 particle mixture containing 19 ppm (0.019 mg/ mL) of TiO 2 was prepared. A bacterial solution of 1 × 10 5 CFU/mL was added one drop at a time to the TiO 2 mixture. The resulting product was then irradiated with FL. The bacterial survival rate decreased steadily in the TiO 2 mixture group, reaching 76.7% after 30 min of FL irradiation and 10.9% after 60 min. After 60 to 180 min, the bacterial survival ratio of the TiO 2 mixture group was significantly lower than that of the control group (P < 0.05). The present study indicates that treating the surfaces of surgical devices and the surgical field with a TiO 2 particle mixture can create a nearly sterile environment that can be maintained throughout surgery, even at low luminous intensities.When titanium dioxide (TiO 2 ) is exposed to ultraviolet (UV) light, various free radicals are released. These free radicals are a potent oxidant that can decompose bacteria and other organic substances (4, 7). In a previous study by the authors, a TiO 2 particle mixture was prepared in order to use its photocatalytic action to prevent postoperative infection. In comparison to the morphological characteristics of thin-film and large-particle TiO 2 formulations, the use of fine particles resulted in a greater surface area, improved UV exposure, and increased contact with the bacteria. This combination of factors provided potent antibacterial effects against Staphylococcus aureus (8). However, the physiological effects of the UV rays used to elicit photocatalysis must also be considered. This study evaluates the photocatalytic bactericidal effects on Staphylococcus aureus of an aqueous system of TiO 2 particles irradiated with fluorescent light (FL) containing no UV light whatsoever and having a lower luminous intensity than sunlight. TiO 2 particles were prepared from titanium (IV) chloride gas using the vapor phase method followed by annealing at room temperature. The surfaces of the particles were rutile (20%) while the interiors were anatase (80%). A powder was prepared by mixing these TiO 2 particles with other substances, mainly sodium percarbonate and citric acid, in order to adjust the aqueous pH and generate a reaction with the TiO 2 (MEK-01; Nanowave, Aichi, Japan). The TiO 2 concentration was 0.38%. The mixture
Titanium dioxide (TiO 2 ) is known to confer photocatalytic bactericidal effects under ultraviolet (UV) irradiation. Few reports are available, however, on the clinical applications of TiO 2 particle mixtures. Our objective in the present research was to evaluate the in vitro bactericidal effects of a TiO 2 particle mixture in a nutrition-rich biological environment. A bacterial suspension of Staphylococcus aureus and epidermidis 3 × 10 3 CFU/mL was added to a TiO 2 particle mixture (0.038 mg/mL) containing mainly sodium percarbonate and citric acid. To simulate a biological environment, 40 μL of 10% bovine serum albumin was added and the culture temperature was maintained at 37°C. The resulting product was irradiated by UV light and the bacterial survival rate was calculated for each time of UV irradiation. In the control sample treated with distilled water + UV, the bacteria survived at a high rate even after 180 min. In the TiO 2 mixture + UV sample, meanwhile, the bacterial survival rate dropped to 43.8% and 6.0% of the baseline values in S. aureus and S. epidermidis, respectively, after 60 min of UV irradiation. The photocatalytic antibacterial action of the TiO 2 particle mixture was high even in a protein-rich biological environment.
By proving the bactericidal effects of a low-concentration titanium dioxide (TiO 2 ) particle mixture against Staphylococcus aureus, we hope to ultimately apply a mixture of this type as part of a clinical treatment regimen. A bacterial suspension of S. aureus 1×10 5 CFU/ml was added dropwise to a TiO 2 particle mixture (19 ppm TiO 2 ) and irradiated by ultraviolet (UV) light. The colony-forming units were counted and the bacterial survival rate was calculated. In the control sample, the bacterial survival rate was 83.3% even after 120 min. In the TiO 2 mixture + UV sample, the bacteria count dropped sharply, reaching 17.3% of the baseline value at 30 min and 0.4% at 60 min. TiO 2 particles dispersed in water mixtures are known to elicit highly efficient UV absorption and greater bonding to bacteria. A reaction of the TiO 2 with another oxidizer altered the aqueous pH and accelerated the photocatalytic chemical reaction. The TiO 2 particle mixture showed high antibacterial action against S. aureus even at a low concentration.
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