Bimodal effect of humic acids on the LPS-induced TNF-alpha release from differentiated U937 cells.

Humic substances (HS) have been reported to possess anti-inflammatory as well as pro-inflammatory properties. The anti-inflammatory activity was demonstrated in the rat paw edema model and we found a preliminary explanation in the 5-lipoxygenase inhibitory effect of humic acids (HA). The pro-inflammatory activity is reflected by the production and release of pro-inflammatory cytokines in HA-treated neutrophilic granulocytes. With regard to the potential use of HA as antiviral and UV-protective agents it appears advisable to investigate the role of HS in the inflammation process in more detail. Hence we tested four different HS preparations - two naturally occurring HA from the Altteich peatland in Germany, one fulvic acid (FA) preparation from a Finnish spruce forest and a synthetic HA-like polymer (caffeic acid oxidation product, KOP) for their influence on the lipopolysaccharide (LPS)-induced TNF-alpha release in human U937 cells. In addition, the cytotoxicity of HS was determined. The results demonstrate a concentration-dependent bimodal effect of HA on the TNF-alpha release of differentiated LPS-stimulated U937 cells for both the natural black peat HA from the Altteich peatland and the HA-like polymer KOP. Low HA concentrations (10-80 microg/ml) enhanced the TNF-alpha release by up to threefold (pro-inflammatory activity), while HA concentrations >100 microg/ml reduced it about 10-fold (anti-inflammatory activity). FA failed to enhance TNF-alpha release, but reduced it at higher concentrations (>200 microg/ml) by the half. Brown water HA did not exert any significant effect on TNF-alpha release. No HS-stimulated TNF-alpha release was also observed in the absence of exogenously supplied LPS. This means that HS, unlike endotoxin, are no inflammation-causing agents for LPS-untreated cells. Differences in the effect of individual HS on TNF-alpha release are discussed in connection with the polyanionic character of HS, their molecular mass distribution and the hitherto imperfectly known chemical structure.

The effect of sonication on microbial disinfection using hypochlorite.

Ultrasound alone is capable of killing bacteria when sufficient power is applied but ultrasound at low powers can also be used to improve the effectiveness biocides. In this paper, we explore the effect of the timing of the ultrasonic treatment at 20 and 850 kHz on the biocidal efficiency of sodium hypochlorite solution towards Escherchia coli suspensions. A remarkable frequency effect has been noted. At the lower frequency of 20 kHz the improvement in biocidal activity is greatest when the ultrasound is applied at the same time as the hypochlorite. At the higher frequency of 850 kHz the improvement is best when ultrasound is used as a pre-treatment immediately followed by hypochlorite addition under normal (silent) conditions. The kill rate achieved for pre-treatment using 850 kHz and simultaneous treatment using 20 kHz are very similar. However the former involves less acoustic energy and so is considered to be the more efficient.

Sonovoltammetric studies on copper in buffered alkaline solution.

The effect of ultrasound on the voltammetry of copper in alkaline solution is reported. At pH 7 the electrode surface remains active after scanning to ca. +1.0 V (vs. SCE) and the effects of ultrasound show the expected substantial enhancement in limiting current due to improved mass transport under ultrasound. However at pH 9, whereas the silent scan is only slightly altered in gross detail from that obtained at pH 7, the sonicated scan is significantly different. This shows the expected current increase only up until ca. +0.6 V (vs. SCE), where there is a substantial loss of current showing a passivation phenomenon that is enhanced by ultrasound. In addition, during the reverse (reduction) scan under ultrasound an anodic peak appears. This suggests reactivation of the electrode during the cathodic sweep, possibly by reductive removal of a transient species from the electrode/(hydr)oxide interface at a potential where oxidation still occurs. Increasing the pH to 11 further shifts the cathodic peaks in the silent voltammogram.

The development and evaluation of ultrasound for the treatment of bacterial suspensions. A study of frequency, power and sonication time on cultured Bacillus species.

Some species of bacteria produce colonies and spores which agglomerate in spherical clusters (Bacillus subtilis) and this serves as a protection for the organisms inside against biocidal attack. Flocs of fine particles e.g. clay can entrap bacteria which can also protect them against the biocides. It is because of problems such as these that alternative methods of disinfecting water are under active investigation. One such method is the use of power ultrasound, either alone or in combination with other methods. Ultrasound is able to inactivate bacteria and deagglomerate bacterial clusters or flocs through a number of physical, mechanical and chemical effects arising from acoustic cavitation. The aim of this study was to investigate the effect of power ultrasound at different powers and frequencies on Bacillus subtilis. Viable plate count techniques were used as a measure of microbial activity. Results showed a significant increase in percent kill for Bacillus species with increasing duration of exposure and intensity of ultrasound in the low-kilohertz range (20 and 38 kHz). Results obtained at two higher frequencies (512 and 850 kHz) indicated a significant increase in bacteria count suggesting declumping. In assessing the bacterial kill with time under different sonication regimes three types of behaviour were characterized: High power ultrasound (lower frequencies) in low volumes of bacterial suspension results in a continuous reduction in bacterial cell numbers i.e. the kill rate predominates. High power ultrasound (lower frequencies) in larger volumes results in an initial rise in cell numbers suggesting declumping of the bacteria but this initial rise then falls as the declumping finishes and the kill rate becomes more important. Low intensity ultrasound (higher frequencies) gives an initial rise in cell numbers as a result of declumping. The kill rate is low and so there is no significant subsequent decrease in bacterial cell numbers.

Potential uses of ultrasound in the biological decontamination of water.

In the past there was a prevailing feeling in industry that power ultrasound would be too expensive to use for water treatment on an industrial scale. This was based on calculations involving the direct scale up of power consumption in small-scale (generally batch) laboratory experiments. In recent times this attitude has changed somewhat as a result of the installation of a number of ultrasonic devices in operational water or sewage treatment plants. In our laboratories we have investigated the decontamination of water under the influence of ultrasound alone and in conjunction with other treatments. The results, particularly when applied to flowing systems, indicate a real future for sonochemistry in water treatment.

Sonoelectrochemical effects in electro-organic systems.

This paper describes recent studies in organic sonoelectrochemistry at Coventry University, including the oxidation of thiophene monoxides, degradation of dye pollutants, formation of conducting polymers and electrosynthetic modification of proteins.

A novel angular geometry for the sonochemical silver recovery process at cylinder electrodes.

In order to obtain maximum ultrasonic effect upon electrochemical silver recovery, mass transfer measurements were investigated. The effect on limiting current of changing the position of an ultrasonic horn tip (i.e. vertical and horizontal) and using a cylinder electrode (CE), was studied in an attempt to find the optimum position required for maximum sonoelectrochemical effect. The importance of the ultrasonic intensity, the electrode-horn distance and positioning (angle) in assigning limiting currents was also investigated. For the CE placed at an angle of 45 degrees with respect to the ultrasonic horn, it was suggested that the 50% increase in limiting current for the 'face-on' geometry is caused by an approximately 50% decrease in diffusion layer thickness for the 'face-on' geometry compared to the 'angular' geometry due to the difference in the sonicated areas for both geometries.

The development and evaluation of electrolysis in conjunction with power ultrasound for the disinfection of bacterial suspensions.

There is an increasing incidence in health problems related to environmental issues that originate from inadequate treatment of potable waters. This has compelled scientists and engineers to engage in innovative technologies to achieve a maximum disinfection at affordable costs. Some species of bacteria produce colonies and spores that can agglomerate in spherical clusters and thus protect organisms on the inside of the cluster against biocidal attack. Flocs of fine particles (e.g., clay) can entrap bacteria and this can also protect them against the biocides. Other bacteria have the ability to mutate, thus building up resistance to conventional biocides (e.g., chlorine). Ultrasound has been shown to be effective in improving the effectiveness of biocides such as chlorine. The aim of this present study was to investigate the effect of electrolysis and power ultrasound as a disinfection treatment and to provide a greater knowledge of the fundamentals of disinfection through the production of hypochlorite in situ from saline solution via electrolysis. The electrode materials investigated were, carbon (felt and graphite), copper and stainless steel rods. The results show that sonication appears to amplify the effect of electrolysis. A combination of both treatments is significantly better than sonication or electrolysis alone.

The effect of ultrasound upon the oxidation of thiosulphate on stainless steel and platinum electrodes.

Ultrasound was found to increase the oxidation peak current and hence the decomposition rate of thiosulphate 50-fold compared to silent conditions. The effects of the ultrasonic frequency (20 and 38 kHz) and power upon the electrochemical oxidation of thiosulphate in aqueous KCl (1 mol dm-3) at stationary stainless steel and platinum electrodes were studied chronoamperometrically and potentiostatically (at various scan rates). No sigmoidal-shaped voltammograms were observed for the redox couple S4O6(2-)/S2O3(2-) in the presence of ultrasound. However, application of ultrasound to this redox couple provided an increase in the oxidation peak current at the frequencies employed, the magnitude of which varied with concentration, scan rate and ultrasonic power. Under sonication at 20 and 38 kHz, the oxidation peak potential shifted anodically with increasing ultrasonic power. This anodic shift in potential may be due to the formation of hydroxyl radicals, changes in electrode surface composition and complex adsorption phenomena. The large increase in oxidation peak currents and the rates of decomposition of thiosulphate, in the presence of ultrasound, are explained in terms of enhanced mass transfer at the electrode due to cavitation and acoustic streaming together with microstreaming coupled with adsorption phenomena. It is also shown that changes in macroscopic temperature throughout the experiment are insufficient to cause the observed enhanced diffusion.

Dye effluent decolourisation using ultrasonically assisted electro-oxidation.

Solutions of the acidic dye, Sandolan Yellow, were subjected to sonolysis, electrolysis and sonoelectrolysis. Decolourisation did not take place using ultrasound alone but was achieved using an electro-oxidation process. The rate of electro-chemical decolourisation in the absence of ultrasound was dependent on the type of electrode used, electrolyte concentration, reaction temperature and the current density. Electro-oxidation of Sandolan Yellow using platinum electrodes was enhanced using ultrasound when carried out in a semi-sealed cell, which minimised the effects of ultrasonic degassing.

The development and evaluation of ultrasound in the biocidal treatment of water.

The effect of ultrasound upon the destruction of micro-organisms has been studied and reported here. The results obtained from the work carried out has shown that ultrasound can be used effectively for water disinfection and has several advantages. When used in conjunction with chlorine it significantly reduces the number of bacteria present in water samples. Ultrasound also reduces the amount of chlorine required for disinfection. Increasing the power of ultrasound leads to greater efficiency in the destruction of bacterial cells. High frequency ultrasound is more beneficial than low frequency in the disinfection of water.