Xinping Zeng

Studies on Disinfection Mechanism of Electrolyzed Oxidizing Water on E. coli and Staphylococcus aureus

Suspension quantitative germicidal test showed that electrolyzed oxidizing water (EO water) was an efficient and rapid disinfectant. Disinfection rates towards E. coli (available chlorine concentration ACC: 12.40 mg/L) and Staphylococcus aureus (ACC: 37.30 mg/L) could reach 100% at 1 and 3 min, respectively. Disinfection mechanism of EO water was investigated at a molecular biological level by detecting a series of biochemical indices. The results showed that the dehydrogenase activities of E. coli and S. aureus decreased rapidly, respectively, at the rates of 45.9% and 32% in the 1st minute treatment with EO water. EO water also improved the bacterial membrane permeability, causing the rise of conductivities and the rapid leakages of intracellular DNA, K(+), and proteins in 1 min. The leakages of DNA and K(+) tended to slow down after about 1 min while those of proteins began to decrease a little after reaching the peak values. The sodium dodecyl sulfonate polyacrylamide gel electrophoresis (SDS-PAGE) showed that EO water destroyed intracellular proteins. The protein bands got fainter and even disappeared as the treatment proceeded. EO waters effects on the bacterial ultrastructures were also verified by the transmission electronic microscopy (TEM) photos. The disinfection mechanism of EO water was composed of several comprehensive factors including the destruction of bacterial protective barriers, the increase of membrane permeability, the leakage of cellular inclusions, and the activity decrease of some key enzymes.

Study on the treatment of copper-electroplating wastewater by chemical trapping and flocculation

Sodium diethyldithiocarbamate (DDTC) is used as a trapping agent and poly-ferric sulphate and polyacrylamide are used as flocculants to treat copper-electroplating wastewater. The influences on the precipitation and flocculation of Cu2+ cation are studied in details, such as the amount of complex copper (EDTA and NH4Cl are used as coordination agents), the addition of DDTC, poly-ferric sulphate and polyacrylamide (PAM) and pH of the solution. In addition, the influences on the trapping copper by different agents such as DDTC, diethylammonium diethyldithiocarbamate (DDC) and ammonium pyrrolidinedithiocarbamate (APDC) are studied as well. The results show that the dosage of DDTC depends only on the content of complex copper, but not on the total amount of copper in the wastewater. When the molar ratio of DDTC to Cu is between 0.8 and 1.2, Cu removal efficiency could be higher than 99.6%. Poly-ferric sulphate and PAM have little effects on the Cu removal, but they have significant effects on the flocculating volume, precipitation rate and nephelometric of the upper clean water.

A glucose biosensor based on the synergistic action of nanometer-sized TiO2 and polyaniline

Polyaniline/active carbon (PANI) and nanometer-sized TiO2 (n-TiO2) were prepared by oxidation and sol-gel methods, respectively, and were then used as a zymophore to modify a glassy carbon electrode (GCE) and a GOx/n-TiO2/PANI/GCE sensor with a synergistic effect was established. A series of performance evaluations for the modified material and sensor was studied in detail through cyclic voltammetry (CV) and a chronoamperometry (CA) method. The results showed that the sensor had a good response to glucose and that the electron of the GOx molecule was transferred directly onto the sensor, and a linear relationship between the GOx redox peak current and the sweep speed was found. The apparent transmission speed constant, k, for dissimilar electrode charges was 1.35s(-1), 95% of the maximum steady current for the GOx/n-TiO2/PANI/GCE sensor could be reached in 10s, the linear range of the detected glucose concentration was from 0.02 mM to 6.0mM, the sensitivity was 6.31 μA mM(-1)cm(-2), and the limit of detection was 18 μM. The sensor had good selectivity and stability and could be maintained at 82% of the initial activity for 30 days.

An electrochemical sensor based on polyaniline for monitoring hydroquinone and its damage on DNA

A dsDNA/PANI/CTS/GCE biosensor was constructed by using the biocompatible chitosan (CTS) and the polyaniline (PANI) with excellent electric catalytic properties and large specific surface areas. The electrochemical behavior of hydroquinone on biosensor and its DNA-damaging mechanisms were investigated. Results showed that the redox peak current was remarkably increased after glassy carbon electrode (GCE) was modified by PANI/CTS. The dsDNA damage by hydroquinone was concentration dependent, and increased along with the increase of hydroquinone oxidation peak current and the reduction of dsDNA guanine oxidation peak current. The linear detection range of hydroquinone with dsDNA/PANI/CTS/GCE was 1.25×10(-6)-3.2×10(-4) M, and the detection limit was 9.65×10(-7) M. It was confirmed by the UV method that applying dsDNA/PANI/CTS/GCE to monitor hydroquinone was accurate and reliable. In addition, it could be deduced that the mode of interaction between the hydroquinone and dsDNA was intercalation. The electrochemical oxidation of hydroquinone on the dsDNA/PANI/CTS/GCE electrode was an adsorption-controlled irreversible and a two-electron two-proton transfer process.

Fungicidal efficiency of electrolyzed oxidizing water on Candida albicans and its biochemical mechanism

The fungicidal influencing factors of electrolyzed oxidizing water (EOW) on Candida albicans were investigated by suspension quantitative germicidal tests. Results showed that EOW possessed predominant fungicidal rate on C. albican, as high as consumately 100% after 0.5min duration of 65.5mg/L active available chlorine concentration (ACC). The fungicidal effect was promoted proportionally along with ACC but was inhibited by organic interferential bovine serum albumin (BSA). The fungicidal mechanism was also investigated at a biological molecular level by detecting series of biochemical indices. Fluorescent microscopy showed that almost all C. albicans cells were stained red in 1min, suggesting that cell membrane was one of EOWs action targets. Transmission electron microscopy (TEM) showed that EOW destroyed the cellular protective barriers and imposed some damage upon the nucleus area, which verified EOWs effects on microbial ultra-structures. EOW improved membrane permeabilities with the result that the leakages of cellular inclusions (K(+), proteins and DNA) and the conductivity increased rapidly. The dehydrogenase relative activities of C. albicans decreased by 44.0% after 10min, indicating that EOW also had a destructive effect on cellular dehydrogenase.

Glucose Biosensor Based on a Glassy Carbon Electrode Modified with Polythionine and Multiwalled Carbon Nanotubes

A novel glucose biosensor was fabricated. The first layer of the biosensor was polythionine, which was formed by the electrochemical polymerisation of the thionine monomer on a glassy carbon electrode. The remaining layers were coated with chitosan-MWCNTs, GOx, and the chitosan-PTFE film in sequence. The MWCNTs embedded in FAD were like “conductive wires” connecting FAD with electrode, reduced the distance between them and were propitious to fast direct electron transfer. Combining with good electrical conductivity of PTH and MWCNTs, the current response was enlarged. The sensor was a parallel multi-component reaction system (PMRS) and excellent electrocatalytic performance for glucose could be obtained without a mediator. The glucose sensor had a working voltage of −0.42 V, an optimum working temperature of 25°C, an optimum working pH of 7.0, and the best percentage of polytetrafluoroethylene emulsion (PTFE) in the outer composite film was 2%. Under the optimised conditions, the biosensor displayed a high sensitivity of 2.80 µA mM−1 cm−2 and a low detection limit of 5 µM (S/N = 3), with a response time of less than 15 s and a linear range of 0.04 mM to 2.5 mM. Furthermore, the fabricated biosensor had a good selectivity, reproducibility, and long-term stability, indicating that the novel CTS+PTFE/GOx/MWCNTs/PTH composite is a promising material for immobilization of biomolecules and fabrication of third generation biosensors.

Biological characteristics and oxidation mechanism of a new manganese-oxidizing bacteria FM-2.

A new manganese-oxidizing strain FM-2 was screened out from biological activated carbon (BAC) filter column and was identified as Citrobacter freundii. The results of the systematic study on this species are as follows: At 27°C, the optimum pH for Citrobacter sp. FM-2 to remove manganese was 7.0-8.0.The best removal rate of manganese under 27°C, pH 7.0 by FM-2 was reached at 4 d, being 76.2%; Compared with adsorption, biological oxidation played a dominant role in this removing process. Almost 75.7% of manganese was oxidized into oxides by Citrobacter sp and there were some particular oxides analogs generated on the bacterial surface; A 296bp DNA fragment amplified from Citrobacter sp. FM-2 revealed that this species has multicopper oxidase genes. Meanwhile, the phylogenetic tree indicated that compared with other related species, Citrobacter sp. FM-2 has its own evolutional independence.

Electrochemical sensors based on multi-walled nanotubes for investigating the damage and action of 6-mercaptopurine on double-stranded DNA

Biosensors based on nanomaterials provide a means for sensitive and rapid detection of DNA damage. To investigate the electrochemical behavior of 6-mercaptopurine (6-MP), including the damage to double-stranded deoxyribonucleic acid (dsDNA) by 6-MP and the damage mechanisms, a dsDNA/MWNT/CTS/GCE biosensor was constructed using multi-walled carbon nanotubes (MWNTs) and chitosan (CTS) as the modifying materials. The experimental results showed that after being modified, the active area of the MWNT/CTS/GCE significantly increased and the oxidation peak current of the MWNT/CTS/GCE in response to K3[Fe(CN)6] exhibited a remarkable increase. The characteristic peak of 6-MP on the biosensor was determined to be approximately 0.55 V using differential pulse voltammetry (DPV). Clear damage to dsDNA caused by 6-MP was observed. The damage to adenine was more severe than to guanine. The interaction between 6-MP and dsDNA could be explained as an intercalation during the electrochemical oxidation process on the modified electrode, which was an irreversible process controlled by adsorption and was accompanied by the transfer of a single electron coupled with a single proton.

Effect of electrolyzed reduced water on chiral theanine and polyphenols in tea.

Pure D/L-theanine enantiomers were synthesized separately, and SEM was used for their crystal-structure observation. The novel enantiomeric separating method by HPLC was established using the chiral selector of β-CD in the mobile phase. Green tea, white tea, oolong tea, black tea and Pu-erh tea were tested for theanine enantiomers by different degrees of fermentation. The significantly higher d-enantiomeric proportion of theanine was found in white tea than the others, which was probably due to its specific processing step of withering. The effect of electrolyzed reduced water (ERW) on enantiomeric theanine and polyphenols in tea was explored. There was no change of theanine, but rather a loss of ECG (epicatechin gallate) and an increasing amount of GA (gallic acid). ERW also reduced tea cream, which contains significant amount of polyphenols, indicating its potential application in the tea-beverage industry.

Establishment of dsDNA/GNs/chit/GCE biosensor and electrochemical study on interaction between 6-mercaptopurine and DNA.

In this paper, the anti-cancer drug 6-mercaptopurine (6-MP) was taken as the detection object. The biosensor of dsDNA/GNs/chit/GCE was established using the grapheme (GNs) and chitosan (chit) as the compound modified material. The electrochemical behavior of 6-MP on the sensor was discussed, and the damage and its mechanism of 6-MP on DNA were studied. The experimental result showed that, after the modification of GNs-chit, the electrode activation area of GNs/chit/GCE increased remarkably, which was improved from 1.76cm2 to 8.64 cm2, and the responsive oxidation peak current of GNs/chit/GCE to K3[Fe(CN)6] also increased remarkably. At the meantime, it was demonstrated that DNA was effectively fixed on the GNs/chit/GCE electrode;6-MP caused obvious damage to dsDNA, and the damage degree on the adenine was bigger than that on the guanine; the interaction between 6-MP and dsDNA was preliminarily deduced as the intercalation, and its electrochemical oxidation process was an irreversible process controlled by the adsorption.