HALOGENS AND THEIR MODE OF ACTION
The extensive use of various forms of chlorine and iodine as antiseptics has resulted in the accumulation of much information about efficiency of these halogens under various circumstances. There has been considerable study given to the factors affecting their germicidal activities and to the mechanisms of these effects.' Much less is known about bromine?. a* The qualitative similarities and quantitative differences in many of the properties of chlorine, bromine, and iodine afford an excellent opportunity for observing the effects of certain isolated factors on germicidal activity. Accordingly, this paper will be concerned, for the most part, with the extent to which a few basic chemical properties of the halogens, such as hydrolysis, ionization, and formation of complexes can be used to explain quantitative dfierences in antiseptic power. The mechanism of the reactions leading to the death of the organism will not be discussed here. The interested reader is referred to another paper in this series and to a published report6 for information on this subject. One would expect that the rate of bactericidal action would be characteristic of the particular halogen compound present. Under usual conditions of use, however, one may have present, in addition to elemental halogen, hypohalous acid formed by hydrolysis, hypohalite ion from ionization of the acid, complex ions involving elemental halogen with halide ion, and N-halogen compounds. Furthermore, factors such as concentration, pH, and temperature should have quantitatively different effects on the germicidal activities of the three halogens because the equilibrium constants of the reactions involved are different. Most of the work leading to quantitative conclusions has been carried out with bacterial spores, beginning with Levine and co-workers,6 Meyers,' Tilley and Chapin: and others. The advantages of using B. metiens spores, for example, have been pointed out by Charlton and Levine9 and need not be enumerated here. Accordingly, in FIGURE 1, we consider the comparative action on B. meliens spores over a suitable concentration range of chlorine,'O bromine, and iodine" at pH 7 and room temperatures. A solution of each halogen free of added halide was added to a buffered distilled water suspension of spores, extraneous organic matter being excluded as far as possible. The log of the time for 99 per cent kill is plotted against the log of the normality of the solution. Calculation shows that under these conditions chlorine exists chiefly as hypochlorous acid and bromine entirely as hypobromous acid, but iodine is present as molecular iodine. It is then not surprising that the usual order of halogen reactivities is not found and that iodine fails to show less germicidal power than bromine. It might be of some interest to note that on a weight concentration basis, iodine is considerably less active than chlorine, although still more active than bromine. Against
Laccase- and chloroperoxidase-nanotube paint composites with bactericidal and sporicidal activity.
Laccase and chloroperoxidase (CPO) were separately immobilized onto multi-walled carbon nanotubes (MWNTs) and subsequently mixed with a commercial eco-friendly paint to generate biocatalytic coatings. The laccase-nanotube based paints showed >99% bactericidal activity against Escherichia coli and Staphylococcus aureus (both challenged with 10⁶ CFU/mL) within 30 min and >98% sporicidal activity against Bacillus cereus and Bacillus anthracis-ΔSterne (initially challenged with 10⁴ CFU/mL) within 120 min. The CPO-nanotube based paints also showed >99% antimicrobial activity within 30 min against E. coli and S. aureus (both challenged with 10⁶ CFU/mL). These enzyme-nanotube based formulations provide an eco-friendly route to generate biocidal compounds, which can prevent the growth of a broad spectrum of bacterial pathogens, including spores. These enzyme-containing paints may be envisioned to be applied as self-decontaminating coatings onto a wide range of surfaces, such as hospital infrastructure, medical devices and equipment, food processing and packaging, etc.; in all cases effective killing of a variety of infectious organisms is critical.
Adsorption of immunoglobulin Y in supermacroporous continuous cryogel with immobilized Cu(2+) ions.
The influence of temperature, pH and ionic strength on the adsorption of Immunoglobulin Y (IgY) in IDA-Cu(2+) cryogel system was studied by batch equilibrium measurements. The adsorptive equilibrium data were obtained at 17 and 27°C, pH 5.0 and 6.5, and at ionic strength of 50 and 200mmolL(-1) NaCl. Langmuir, Freundlich and Langmuir-Freundlich models were fitted to equilibrium data, while the enthalpy of adsorption of IgY in IDA-Cu(2+) cryogel system was calculated through Van't Hoff analysis. The binding of IgY on cryogel was stronger at 27°C and lowest pH and ionic strength values, with apparent maximum adsorption capacity of 27mgg(-1). The adsorption of protein in the resin was spontaneous in all analyzed cases. The results provide valuable information to enable the improvement of IgY purification processes.