Bacterial sterilization by a dielectric barrier discharge (DBD) in air

Cold atmospheric plasma treatment of microorganisms and living tissues has become a popular topic in modern plasma physics and in medical science. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for treatment of skin diseases, open injuries and dental caries. Because of their enhanced plasma chemistry, Dielectric Barrier Discharges (DBDs) have been widely investigated for some emerging applications such as biological and chemical decontamination of media at ambient conditions. Despite the high breakdown voltage in air at atmospheric pressure, the average current of DBD discharges is low. Therefore, a DBD can be applied in direct contact with biological objects without causing any damage. In this work a 60 Hz DBD reactor, which generates cold atmospheric plasma inside Petri dishes with bacterial culture, is investigated. Samples of Staphylococcus aureus, a Gram-positive bacterium and Escherichia coil a Gram-negative bacterium were selected for this study. The bacterial suspensions were evenly spread on agar media planted in Petri dishes. The reactor electrodes were placed outside the Petri dish, thus eliminating the risk of samples microbial contamination. The covered Petri dish with agar medium in it serves as dielectric barrier during the treatment. The plasma processing was conducted at same discharge power (similar to 1.0 W) with different exposure time. Sterilization of E. coil and S. aureus was achieved for less than 20 min. Plasma induced structural damages of bacteria were investigated by Scanning Electron Microscopy. (C) 2010 Elsevier B.V. All rights reserved.

Effect of the fluorination of DLC film on the corrosion protection of aluminum alloy (AA 5052)

It is presented a study conducted on the physical and electrochemical properties of fluorinated a-C:H films deposited onto a commercial aluminum alloy (AA 5052). The coatings were deposited from mixtures of 91% of acetylene and 9% of argon by plasma immersion ion implantation and deposition technique, PIIID. Total gas pressure was 44 Pa and deposition time (t(dep)) was varied from 300 to 1200 s. The depositing plasmas were generated by the application of radiofrequency power (13.56 MHz, 100W) to the upper electrode and high voltage negative pulses (2400 V. 300 Hz) to the sample holder. Fluorine was incorporated in a post-deposition plasma treatment (13.56 MHz, 70W, 13 Pa) generated from sulfur hexafluoride atmosphere. Chemical structure and composition of the films were investigated using infrared reflectance/absorbance spectroscopy and X-ray photoelectron spectroscopy. The corrosion resistance of the layers was determined by electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution, at room temperature. Films presented good adhesion to the substrates and are classified as hydrogenated amorphous carbon (a-C:H) with oxygen traces. Fluorine was detected in all the samples after the post-deposition treatment being its proportion independent on the deposition time. Film thickness presented different tendencies with t(dep), revealing the variation of the deposition rate as a function of the deposition time. Such fluorinated a-C:H films improved the corrosion resistance of the aluminum surface. In a general way the corrosion resistance was higher for films prepared with lower deposition times. The variation of sample temperature with t(dep) was found to be decisive for the concentration of defects in the films and, consequently, for the performance of the samples in electrochemical tests. Results are interpreted in terms of the energy delivered to the growing layer by ionic bombardment. (C) 2010 Elsevier B.V. All rights reserved.

Study of polypropylene surface modification by air dielectric barrier discharge operated at two different frequencies

In this work, air dielectric barrier discharge (DBD) operating at the line frequency (60 Hz) or at frequency of 17 kHz was used to improve the wetting properties of polypropylene (PP). The changes in the surface hydrophilicity were investigated by contact angle measurements. The plasma-induced chemical modifications of PP surface were studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transformed infrared spectroscopy (FTIR). The polymer surface morphology and roughness before and after the DBD treatment were analyzed by atomic force microscopy (AFM). To compare the plasma treatment effect at different frequencies the variation of the contact angle is presented as a function of the deposited energy density. The results show that both DBD treatments leaded to formation of water-soluble low molecular weight oxidized material (LMWOM), which agglomerated into small mounts on the surface producing a complex globular structure. However, the 60 Hz DBD process produced higher amount of LMWOM on the PP surface comparing to the 17 kHz plasma treatment with the same energy dose. The hydrophilic LMWOM is weakly bounded to the surface and can be easily removed by polar solvents. After washing the DBD-treated samples in de-ionized water their surface roughness and oxygen content were reduced and the PP partially recovered its original wetting characteristics. This suggested that oxidation also occurred at deeper and more permanent levels of the PP samples. Comparing both DBD processes the 17 kHz treatment was found to be more efficient in introducing oxygen moieties on the surface and also in improving the PP wetting properties. © 2012 Elsevier B.V. All rights reserved.

Estudo da reciclagem mecânica de poli (cloreto de vinila) - PVC - proveniente deresíduos da construção civil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito da incorporação de flúor nas propriedades de superfície de filmes DE aC:H

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of the high-temperature plasma immersion ion-implantation treatment on corrosion behavior of Ti-6Al1-4V

Nitrogen implantation into Ti alloys at higher temperatures improves their mechanical and corrosion resistance properties by forming a thicker nitride layer. In this paper, two different sets of Ti-6Al-4V samples were plasma immersion ion implantation (PIII)-treated using nitrogen plasma, varying the treatment time from 30 to 150 min (800 degrees C) and the process temperature from 400 degrees C to 800 degrees C (t = 60 min). Nanoindentation measurements of the PIII-treated samples at 800 C during 150 min showed the highest hardness value, 24 GPa, which is about four times bigger than untreated sample hardness. The N penetration at these conditions reached approximately 150 nm as analyzed by Auger spectroscopy. on the other hand, the lowest passive current density (3 x 10(-7) A. cm(-2)) was obtained for a PIII-treated sample during 30 min at higher temperature (800 degrees C). The corrosion resistance of this sample is almost the same as for the untreated specimen. Corrosion behavior evidenced that in strong oxidizing media, all PIII-treated samples are more corrosion resistant than the untreated one. PIII processing at higher temperatures promotes smoothing of the sample surface as observed by scanning electron microscopy (SEM). Grazing incidence X-ray diffraction analyses of the untreated samples identified the two typical Ti phases, Ti alpha and Ti beta. After the implantation, Ti2N and TiO2 phases were also detected.

The influence of hydrogen plasma pre-treatment on the structure of BDND electrode surface applied for phenol detection

The surface properties of boron-doped nanocrystalline diamond films treated with H(2) plasma was investigated in regard to their electrochemical response for phenol oxidation. The surface of these films is relatively flat formed by crystallites with sizes of about 40 nm. X-ray photoelectron spectroscopy analyses showed that electrode surface has a high amount of C-H bonds. This behavior is in agreement with Mott-Schottky plot measurements concerning the flat band potential that presented a value as expected for hydrogenated diamond surface. This electrode presented the phenol detection limit of 0.08 mg L(-1) for low phenol concentrations from 40 to 250 mu mol L(-1).

Polymer treatment by plasma immersion ion implantation of nitrogen for formation of diamond-like carbon film

Nitrogen ions were implanted by plasma immersion in Kapton, Mylar and polypropylene, with the objective of forming a diamond-like carbon layer on these polymers. The Raman spectrum of the implanted polypropylene showed typical Diamond-Like Carbon (DLC) graphite (G) and disorder (D) peaks, with an sp 3/sp2 hybridization ratio of approximately 0.4 to 0.6. The XPS analysis of the three implanted polymers also showed peaks of C-C and N-C bonds in the sp3 configuration, with hybridization ratios in the same range as the Raman result. The implanted polymers were exposed to oxygen plasma to test the resistance of the polymers to oxygen degradation. Mass loss rate results, however, showed that the DLC layer formed is not sufficiently robust for this application. Nevertheless, the layer formed can be suitable for other applications such as in gas barriers in beverage containers. Further study of implantation conditions may improve the quality of the DLC layer.

Use of platelet-rich plasma in the treatment of deep corneal ulcers induced in rabbits.clinical and histomorphometric evaluation

The repair process induced corneal ulcer in rabbits using platelet-rich plasma in the form of eyedrop or clot was clinically evaluated and compared. Sixty rabbits were divided into four groups of 15 animals, denominated platelet group (PG), clot group (CLG), control group (CG), and amniotic control group (AG). Experimental groups were then subdivided into three groups (M4, M7, M30), corresponding to the end of the evaluation period. There were no differences between treatments regarding ocular sensitivity, chemosis and ocular secretion. The groups treated with PRP either as eyedrop or a clot showed less opacity than the animals treated only with amniotic membrane at the moment of the final evaluation. The presence of corneal ulcers in the groups treated with PRP showed lower intensity than the other groups. Histomorphometric examination showed that corneal epithelization in the initial phase of the lesion was greater when using PRP. The use of amniotic membrane promoted corneal epithelial and stromal thickness, as well as synergism when associated to PRP.

Incorporation of Ca, P, and Si on bioactive coatings produced by plasma electrolytic oxidation: The role of electrolyte concentration and treatment duration

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Solution heat treatment of plasma nitrided 15-5PH stainless steel - Part I: Improvement of the corrosion resistance

The results of the investigation on Solution Heat Treatment of Plasma Nitrided (SHTPN) precipitation-hardened steel 15-5PH are presented. The layers have been obtained by the plasma nitriding process followed by solution heat treatment at different temperatures. The influence of the solution heat treatment after nitriding on the dissolution process of the nitrided layer has been considered. The nitrided layers were studied by scanning electron microscopy, X-ray microanalysis (EDX), and X-Ray diffraction. Micro-hardness tests of the nitrided layers and solubilized nitrided layers have been carried out and interpreted by considering the processing conditions. It was found that high nitrogen austenitic cases could be obtained after SHTPN of martensitic precipitation-hardened steel (15-5PH). When Solution Heat Treatment (SHT) was performed at 1100 °C, some precipitates were observed. The amount of precipitates significantly reduced when the temperature increased. The EDX microanalysis indicated that the precipitate may be chromium niobium nitride. When the precipitation on the austenite phase occurred in small amount, the corrosion resistance increased in SHTPN specimens and the pit nucleation potential also increased. The best corrosion result occurred for SHT at 1200 °C.

Evaluation of the spouted bed dried leaf extract of Bauhinia forficata for the treatment of experimental diabetes in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cissus sicyoides (princess vine) in the long-term treatment of streptozotocin-diabetic rats

Leaf decoctions of Cissus sicyoides (princess vine) are taken widely as a popular remedy for diabetes mellitus in Brazil, where its common name is 'vegetal insulin'. However, there have been practically no attempts so far to determine scientifically whether it has antidiabetic effects and we decided to administer leaf decoctions, over extended periods, to normal and streptozotocin-diabetic rats, and investigate the effects of this treatment on the physiological and metabolic parameters that are altered in diabetic animals. The experimental model adopted was shown to be appropriate by running a parallel treatment with insulin, which led to expected improvements in several abnormal parameter values. The decoction treatment significantly reduced the intake of both food and fluid and the volume of urine excreted, as well as the levels of blood glucose, urinary glucose and urinary urea, in comparison with controls. Lipid metabolism was not affected by the treatment; nor was the level of hepatic glycogen in diabetic animals, which indicated that the mechanism responsible for the improvement in carbohydrate metabolism, observed in animals treated with the decoction, could not involve inhibition of glycogenolysis and/or stimulation of glycogenesis. The fact that normal animals treated with C. sicyoides exhibited no changes in any of the measured parameters suggests that its mode of action in diabetic animals does not resemble those of sulphonylurea or insulin. It may, however, act in a similar way to biguanide, via inhibition of gluconeogenesis.

Effects of calcium gluconate and PMSF in the treatment of acute intoxication of chicken by TOCP

To examine the efficacy of calcium gluconate (two doses of Ca-Glu 5 mg/kg i.v.) to alleviate the injurious effects of organophosphorus induced delayed neuropathy (OPIDN) in the presence or absence of phenylmethanesulfonyl fluoride (PMSF go mg/kg i.m.), 14 groups of four isabrown hens were used. To measure the lymphocyte neuropathy target esterase (LNTE)activity, groups receiving just distilled water (control), groups receiving just Tri-orto-cresyl phosphate (TOCP; 500 mg/kg p.o.) (Positive control), and other groups receiving TOCP and Ca-Glu or PMSF simultaneously or 12 hours later following intoxication by TOCP were used. They were sacrificed 12 and 24 hours after the administration of TOCP. To observe a 28-day time course of neurotoxicity scores and calcium plasma concentration, five groups were used. Regarding free Ca(2+)in the plasma, the positive control produced a characteristic profile time course up and down (luring 28 days, and some hens with maximum score of neurotoxicity in 28 days. The treatment, which prevented greater oscillation in free Ca(2+) in the plasma, presented a decrease in OPIDN in relation to the positive control. Twelve hours after the administration of TOCP, LNTE was 70-80% inhibited when compared with control, whereas the first decrease in the free Ca(2+) in the plasma was significantly different from the control only 24 hours after the administration of TOCP. In summary, the sooner the Ca-Glu is started, the less severe the neuropathy effects.