Microflow‐injection chemiluminescence of luminol and hypochlorite enhanced by phloxine B

We report for the first time that the sensitivity of the luminol–hypochlorite chemiluminescence (CL) reaction was enhanced approximately 10 times by the addition of phloxine B. The maximum wavelength of CL emission shifted from 431 to 595 nm in the absence and presence, respectively, of phloxine B, suggesting that an efficient chemiluminescence resonance energy transfer occurred between a luminol donor and a phloxine B acceptor in the luminol–hypochlorite–phloxine B system. Based on this observation, a simple, rapid and sensitive microflow injection CL method, using a microchip with spiral channel configurations, was developed for the determination of hypochlorite. Under optimized conditions, a linear calibration curve (R² = 0.9944) over the range 0.1–10.0 µmol/L was obtained, with a detection limit of 0.025 µmol/L (S:N = 3). The relative standard deviation (RSD) was found to be 4.2% (n = 10) for 2.5 µmol/L hypochlorite. The sample consumption was only 2 μL, with a sample throughput of 90/h. The method has been used for determining trace amounts of hypochlorite in water samples with satisfactory results. Copyright © 2012 John Wiley & Sons, Ltd.     

Antimicrobial activity and effectiveness of a combination of sodium hypochlorite and hydrogen peroxide in killing and removing Pseudomonas aeruginosa biofilms from surfaces

AIMS: To evaluate both the antimicrobial activity and the effectiveness of a combination of sodium hypochlorite and hydrogen peroxide (Ox-B) for killing Pseudomonas aeruginosa ATCC 19142 cells and removing P. aeruginosa biofilms on aluminum or stainless steel surfaces. METHODS AND RESULTS: Pseudomonas aeruginosa biofilms were developed in tryptic soy broth containing vertically suspended aluminium or stainless steel plates. Biofilms were exposed to a mixed sodium hypochlorite and hydrogen peroxide solution as a sanitizer for 1, 5 and 20 min. The sanitizer was then neutralized, the cells dislodged from the test surfaces, and viable cells enumerated. Cell morphologies were determined using scanning (SEM) and transmission electron microscopy (TEM). Cell viability was determined by confocal scanning laser microscopy (CSLM). Biofilm removal was monitored by Fourier transform infrared (FTIR) spectrophotometry. Cell numbers were reduced by 5-log to 6-log after 1 min exposure and by 7-log after 5 min exposure to Ox-B. No viable cells were detected after a 20 min exposure. Treatment with equivalent concentrations of sodium hypochlorite reduced viable numbers by 3-log to 4-log after 1 min exposure and by 4-log to 6-log after 5 min, respectively. A 20 min exposure achieved a 7-log reduction. Hydrogen peroxide at test concentration treatments showed no effect. FTIR analysis of treated pseudomonad biofilms on aluminium or stainless steel plates showed either a significant reduction or complete removal of biofilm material after a 5 min exposure to the mixed sodium hypochlorite and hydrogen peroxide solution. SEM and TEM images revealed damage to cell wall and cell membranes. CONCLUSIONS: A combination of sodium hypochlorite and hydrogen peroxide effectively killed P. aeruginosa cells and removed biofilms from both stainless steel and aluminium surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of sodium hypochlorite and hydrogen peroxide can be used as an alternative disinfectant and/or biofilm remover of contaminated food processing equipment.     

Use of superabsorbent polymer gels for surface decontamination of Bacillus anthracis spores

Aims:  This study evaluated the inactivation of Bacillus anthracis Vollum spores dried on a nonporous surface using a superabsorbent polymer (SAP) gel containing commercially available liquid decontaminants.
Methods and Results:  The first phase determining the availability of the liquid decontaminant within the SAP showed that the SAP gel containing pH-adjusted sodium hypochlorite (NaOCl) inhibited B. anthracis growth while the water control SAP gel had no affect on growth. For testing surface decontamination, B. anthracis spores were dried onto steel coupons painted with chemical agent resistant coating and exposed to SAP containing either pH-adjusted NaOCl, chlorine dioxide (ClO₂) or hydrogen peroxide/peracetic acid (H₂O₂/PA) for 5 and 30 min. At contact times of both 5 and 30 min, all of the SAP gels containing pH-adjusted NaOCl, ClO₂ or H₂O₂/PA inactivated B. anthracis spores at levels ranging from 2·2 to ≥7·6 log reductions.
Conclusions:  Incorporation of three commercially available decontaminant technologies into a SAP gel promotes inactivation of B. anthracis spores without observable physical damage to the test surface.
Significance and Impact of the Study:  This work provides preliminary data for the feasibility of using SAP in inactivating B. anthracis spores on a nonporous surface, supporting the potential use of SAP in surface decontamination.     

Urate attenuates oxidation of native low-density lipoprotein by hypochlorite and the subsequent lipoprotein-induced respiratory burst activities of polymorphonuclear leukocytes

Oxidation converts native low-density lipoprotein (LDL) into a signal molecule promoting inflammatory processes during atherogenesis. The exact contribution of different antioxidants in prevention of LDL oxidation is not known. Uric acid efficiently scavenges oxidants including hypochlorite. We investigated the effect of different urate concentrations (25-500 mol/l) on the oxidation of isolated native LDL by sodium hypochlorite (1000 mol/l). While relative electrophoretic mobility declined continuously with increasing urate concentrations in the oxidation medium, lipid peroxidation as measured by TBARS was blunted only at high molar urate/NaOCl ratios. By decreasing oxidative modifications, urate dose-dependently (beginning with a urate/NaOCl ratio of 1:40) diminished stimulatory effects of oxidized LDL on the respiratory burst of resting polymorphonuclear leukocytes (PMNL). Protecting effects of urate against the proinflammatory action of oxidized LDL on activated cells were evident only at a molar urate/NaOCl ratio of 1:2 suggesting different sensitivities of PMNL to LDL oxidation state in dependence on their activity state.     

Peroxyl radical is produced upon the interaction of hypochlorite with tert-butyl hydroperoxide

As we reported previously, hypochlorite interacting with organic hydroperoxides causes their decomposition ((1995) Biochemistry (Moscow), 60, 1079-1086). This interaction was supposed to be a free-radical process and serve as a source of free radicals initiating lipid peroxidation (LP). The present study is the first attempt to detect and identify free radicals produced in the reaction of hypochlorite with tert-butyl hydroperoxide, (CH₃)₃COOH, which we have used as an example of organic hydroperoxides. We have used a direct method for free radical detection, EPR of spin trapping, and the following spin traps: N-tert-butyl--phenylnitrone (PBN) and -(4-pyridyl-1-oxyl)-N-tert-butylnitrone (4-POBN). When hypochlorite was added to (CH₃)₃COOH in the presence of a spin trap, an EPR spectrum appeared representing a superposition of two signals. One of them belonged to a spin adduct formed as a result of direct interaction of hypochlorite with the spin trap (hyperfine splitting constants were: _H H = 0.148 mT; a_N = 1.537 mT; and H_PP = 0.042 mT for 4-POBN and _H = 0.190 mT; a_N = 1.558 mT; and H_PP = 0.074 mT for PBN). The other signal was produced by hypochlorite interactions with (CH3)3COOH itself (hyperfine splitting constants were: _H = 0.233 mT; aN = 1.484 mT; H_PP = 0.063 mT and _H = 0.360 mT; a_N = 1.547 mT; H_PP = 0.063 mT for 4-POBN and PBN, respectively). Comparison of spectral characteristics of this spin adduct with those of tert-butoxyl or tert-butyl peroxyl radicals produced in known reactions of (CH₃)₃COOH with Fe²⁺ and Ce⁴⁺, respectively, showed that the radical (CH₃)₃COO. is produced from the interaction of hypochlorite with (CH₃)₃COOH^. Like Ce⁴⁺ but not Fe²⁺, hypochlorite addition to (CH₃)₃COOH was accompanied by a bright flash of chemiluminescence characteristic of the reactions in which peroxyl radicals are produced. Thus, all these results suggest peroxyl radical production in the reaction of hypochlorite with hydroperoxide. This reaction is one of the most possible ways for the initiation of free-radical LP that occurs in vivo, when hypochlorite interacts with unsaturated lipids comprising natural protein–lipid complexes, such as lipoproteins and biological membranes.     

Evaluation of Hot Water Treatments for Management of Ditylenchus dipsaci and Fungi in Daffodil Bulbs

Treatment of daffodil (Narcissus pseudonarcissus) bulbs in a 0.37% formaldehyde water solution at 44 C for 240 minutes is a standard practice in California for management of the stem and bulb nematode, Ditylenchus dipsaci. Recent concern over the safety of formaldehyde and growers'' requests for a shorter treatment time prompted a reevaluation of the procedure. The time (Y, in minutes) required to raise the temperature at the bulb center from 25 to 44 C was related to bulb circumference (X, in cm) and is described by the linear regression Y = -15 + 3.4X. The time required for 100% mortality of D. dipsaci in vitro without formaldehyde was 150, 60, and 15 minutes at 44, 46, and 48 C, respectively. Hot water treatment (HWT) with 0.37% formaldehyde at 44 C for 150 minutes controlled D. dipsaci and did not have a detrimental effect on plant growth and flower production. Shorter formaldehyde-HWT of 90, 45, and 30 minutes at 46, 48, and 50 C, respectively, controlled D. dipsaci but suppressed plant growth and flower production. Fungal genera commonly isolated from the bulbs in association with D. dipsaci were Penicillium sp., Fusarium oxysporum f. sp. narcissi, and Mucor plumbeus, representing 60, 25, and 5%, respectively, of the total fungi isolated. These fungi caused severe necrosis in daffodil bulbs. HWT at 44 C for 240 minutes reduced the number of colonies recovered from bulbs. The effects of formaldehyde, glutaraldehyde, and sodium hypochlorite in reducing the population of fungi within bulbs were variable. Satisfactory control of D. dipsaci within bulbs can be achieved with HWT of bulbs at 44 C for 150 minutes with 0.37% formaldehyde or at 44 C for 240 minutes without chemicals.     

Patulin and aflatoxin in brown rot lesion of apple fruits and their regulation

Aspergillus flavus, A. niger, Penicillium expansum and Rhizopus stolonifer were the most frequently isolated fungi from healthy apple fruits. Alternaria alternata was the most common organism of rotten apple fruits, followed by A. niger, A. flavus, P. expansum and R. stolonifer. The prevalent type of decay, brown rot lesion, is caused by R. stolonifer followed by A. flavus, A. niger, A. alternata and P. expansum. Sodium hypochlorite had good curative properties against fruit rots. The main natural mycotoxins produced in rotten apple were patulin and aflatoxins. The optimum temperature for patulin production by P. expansum was 15 °C after 15 days. Complete inhibition of patulin formation was attained using 0.2% lemon oil and > 90% inhibition using 0.05% lemon and 0.2% orange oils. Also significant inhibition (> 90%) of aflatoxin production was observed with 0.2% lemon oil. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quantitative analysis of CL-20 explosive by smartphone-based chemiluminescence method

A new smartphone-based chemiluminescence method has been introduced for the quantitative analysis of CL-20 (Hexanitroazaisowuertzitan) explosive. The solvent mixture, oxidizer agent, and concentration of the reactants were optimized using statistical procedures. CL-20 explosive showed a quenching effect on the chemiluminescence intensity of the luminol−NaClO reaction in the solvent mixture of DMSO/H₂O. A smartphone was used as a detector to record the light intensity of chemiluminescence reaction as a video file. The recorded video file was converted to an analytical signal as intensity luminescence–time curve by a written code in MATLAB software. Dynamic range and limit of detection of the proposed method were obtained 2.0–240.0 and 1.1 mg⋅L⁻¹, respectively, in optimized concentrations 1.5 × 10⁻³ mol⋅L⁻¹ luminol and 1.0 × 10⁻² mol⋅L⁻¹ NaClO. Precursors TADB, HBIW, and TADNIW in CL-20 explosive synthesis did not show interference in measurement the CL-20 purity. The analysis of CL-20 spiked samples of soil and water indicated the satisfactory ability of the method in the analysis of real samples. The interaction of CL-20 molecules and OCl⁻ ions is due to quench of chemiluminescence reaction of the luminol−NaClO.     

Heterodera glycines Cyst Components and Surface Disinfestants Affect H. glycines Hatching

We investigated the effects of Heterodera glycines cyst components and surface disinfestants on hatching of H. glycines eggs in vitro. Eggs were incubated in either H. glycines cyst wall fragments, cyst wall and egg rinsate, egg homogenate, or control solutions of soybean root diffusate, sterile distilled water, or zinc sulfate. Hatch in cyst wall and egg rinsate, and egg homogenate, was greater (α = 0.05) than hatch in sterile distilled water; however, it was not different from hatch in zinc sulfate according to Dunnett''s test. Hatch in cyst wall fragments was similar to hatch in sterile distilled water. To determine whether surface disinfestants affected hatch, eggs were treated first with chlorhexidine diacetate, mercuric chloride, sodium hypochlorite, or streptomycin sulfate and then incubated in H. glycines egg homogenate, soybean root diffusate, sterile distilled water, or zinc sulfate. Hatch of eggs treated with chlorhexidine diacetate, mercuric chloride, and streptomycin sulfate was reduced (α = 0.05), and hatch of eggs treated with sodium hypochlorite was increased (α = 0.05) relative to hatch of nontreated eggs in all incubation solutions except zinc sulfate according to Dunnett''s Test. Hatch in zinc sulfate was similar among all surface disinfestants except mercuric chloride, where hatch was reduced relative to hatch of nontreated and other surface disinfestant-treated eggs.