https://doc.rero.ch/record/29689/files/fro_apn.pdf

Antibacterial properties of nanoparticles.

A review of the biomaterials technologies for infection-resistant surfaces.

The photocatalytic properties of titanium dioxide are well known and have many applications including the removal of organic contaminants and production of self-cleaning glass. There is an increasing interest in the application of the photocatalytic properties of TiO2 for disinfection of surfaces, air and water. Reviews of the applications of photocatalysis in disinfection (Gamage and Zhang 2010; Chong et al., Wat Res 44(10):2997–3027, 2010) and of modelling of TiO2 action have recently been published (Dalrymple et al. , Appl Catal B 98(1–2):27–38, 2010). In this review, we give an overview of the effects of photoactivated TiO2 on microorganisms. The activity has been shown to be capable of killing a wide range of Gram-negative and Gram-positive bacteria, filamentous and unicellular fungi, algae, protozoa, mammalian viruses and bacteriophage. Resting stages, particularly bacterial endospores, fungal spores and protozoan cysts, are generally more resistant than the vegetative forms, possibly due to the increased cell wall thickness. The killing mechanism involves degradation of the cell wall and cytoplasmic membrane due to the production of reactive oxygen species such as hydroxyl radicals and hydrogen peroxide. This initially leads to leakage of cellular contents then cell lysis and may be followed by complete mineralisation of the organism. Killing is most efficient when there is close contact between the organisms and the TiO2 catalyst. The killing activity is enhanced by the presence of other antimicrobial agents such as Cu and Ag.

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Photocatalytic disinfection using titanium dioxide: spectrum and mechanism of antimicrobial activity

Related Systems: New Insights into Biosensing, Bioimaging, Genomics, Diagnostics, and Therapy Jun Yao,† Mei Yang,† and Yixiang Duan*,†,‡ †Research Center of Analytical Instrumentation, Analytical and Testing Center, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, China ‡Research Center of Analytical Instrumentation, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, China

Chemistry, Biology, and Medicine of Fluorescent Nanomaterials and Related Systems: New Insights into Biosensing, Bioimaging, Genomics, Diagnostics, and Therapy

Metal oxide nanoparticles as antimicrobial agents: a promise for the future

Metal pins used to apply skeletal traction or external fixation devices protruding through skin are susceptible to the increased incidence of pin site infection. In this work, we tried to establish the photokilling effects of titanium dioxide (TiO2) nanoparticles on an orthopedic implant with an in vitro study. In these photocatalytic experiments, aqueous TiO2 was added to the tested microorganism. The time effect of TiO2 photoactivation was evaluated, and the loss of viability of five different bacteria suspensions (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus hirae, and Bacteroides fragilis) was examined by the viable count procedure. The bactericidal effect of TiO2 nanoparticle-coated metal plates was also tested. The ultraviolet (UV) dosage used in this experiment did not affect the viability of bacteria, and all bacteria survived well in the absence of TiO2 nanoparticles. The survival curve of microorganisms in the presence of TiO2 nanoparticles showed that nearly complete killing was achieved after 50 min of UV illumination. The formation of bacterial colonies above the TiO2 nanoparticle-coated metal plates also decreased significantly. In this study, we clearly demonstrated the bactericidal effects of titanium dioxide nanoparticles. In the presence of UV light, the titanium dioxide nanoparticles can be applicable to medical facilities where the potential for infection should be controlled.

Studies of photokilling of bacteria using titanium dioxide nanoparticles.

Soy protein, a rich source of phytoestrogens, exhibit estrogen-type bioactivity. The purpose of this study was to determine if ingestion of isoflavones before ovariectomy can prevent bone loss following ovariectomy. Twenty-four nulliparous Wistar rats were randomly divided into four groups. In the normal diet groups, a sham operation was performed on Group A, while ovariectomy was performed on Group B. For Groups C and D, all rats were fed with an isoflavone-rich (25 mg/day) diet for one month, then bilateral ovariectomy were performed. In the rats in Group C, a normal diet was begun following the ovariectomy. The rats in Groups D continued to receive the isoflavone-rich diet for two additional months postoperatively. All rats were sacrificed 60 days after surgery. The weight of bone ash of the long bones and whole lumbar spine were determined. A histological study of cancellous bone was done and biochemical indices of skeletal metabolism were performed and analyzed. The markers of bone metabolism exhibited no significant changes. When compared with the sham-operated rats fed a normal diet, the bone mass of ovariectomized rats decreased significantly; pre-ovariectomy ingestion of an isoflavone-rich diet did not prevent bone loss. The bone mass of rats treated with an isoflavone-rich diet for three months was higher than controls two months after ovariectomy. Dietary isoflavones did not prevent the development of post-ovariectomy bone loss, but long-term ingestion of an isoflavone-rich diet increased the bone mineral contents after ovariectomy in young rats.

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Isoflavones prevent bone loss following ovariectomy in young adult rats

Intensive eccentric exercise can cause muscle damage. We simulated an animal model of isokinetic eccentric exercise by repetitively stretching stimulated triceps surae muscle-tendon units to determine if such exercise affects the mechanical properties of the unit within its physiologic excursion. Biomechanical parameters of the muscle-tendon unit were monitored during isokinetic eccentric loading in 12 rabbits. In each animal, one limb (control group) was stretched until failure. The other limb (study group) was first subjected to isokinetic and eccentric cyclic loading at the rate of 10.0 cm/min to 112% (group I) or 120% (group II) of its initial length for 1 hour and then stretched to failure. Load-deformation curves and biomechanical parameters were compared between the study and control groups. When the muscle-tendon unit received eccentric cyclic loading to 112%, changes in all biomechanical parameters – except for the slope of the load-deformation curve – were not significant. In contrast, most parameters, including the slope of the load-deformation curve, peak load, deformation at peak load, total energy absorption, and energy absorption before peak load, significantly decreased after isokinetic eccentric cyclic loading to 120%. We found a threshold for eccentrically induced injury of the rabbit triceps surae muscle at between 12% and 20% strain, which is within the physiologic excursion of the muscle-tendon units. Our study provided evidence that eccentric exercise may induce changes in the biomechanical properties of skeletal muscles, even within the physiologic range of the excursion of the muscle-tendon unit.

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Chien Che Wang

Papers

Studies of photokilling of bacteria using titanium dioxide nanoparticles.

Isoflavones prevent bone loss following ovariectomy in young adult rats

Isokinetic eccentric exercise can induce skeletal muscle injury within the physiologic excursion of muscle-tendon unit: a rabbit model