Antimicrobial cetylpyridinium chloride causes functional inhibition of mitochondria as potently as canonical mitotoxicants, nanostructural disruption of mitochondria, and mitochondrial Ca2+ efflux in living rodent and primary human cells

People are exposed to high concentrations of antibacterial agent cetylpyridinium chloride (CPC) via food and personal care products, despite little published information regarding CPC effects on eukaryotes. Here, we show that low-micromolar CPC exposure, which does not cause cell death, inhibits mitochondrial ATP production in primary human keratinocytes, mouse NIH-3T3 fibroblasts, and rat RBL-2H3 immune mast cells. ATP inhibition via CPC (EC50 1.7 μM) is nearly as potent as that caused by canonical mitotoxicant CCCP (EC50 1.2 μM). CPC inhibition of oxygen consumption rate (OCR) tracks with that of ATP: OCR is halved due to 1.75 μM CPC in RBL-2H3 cells and 1.25 μM in primary human keratinocytes. Mitochondrial [Ca2+] changes can cause mitochondrial dysfunction. Here we show that CPC causes mitochondrial Ca2+ efflux from mast cells via an ATP-inhibition mechanism. Using super-resolution microscopy (fluorescence photoactivation localization) in live cells, we have discovered that CPC causes mitochondrial nanostructural defects in live cells within 60 min, including the formation of spherical structures with donut-like cross section. This work reveals CPC as a mitotoxicant despite widespread use, highlighting the importance of further research into its toxicological safety.

Effects of different antiviral mouthwashes on the surface roughness, hardness, and color stability of composite CAD/CAM materials

OBJECTIVE

To evaluate the effect of COVID-19 preventive mouthwashes on the surface hardness, surface roughness (Ra), and color change (ΔE) of three different polymer-based composite CAD/CAM materials (Vita Enamic (ENA), Grandio Block (GB), Lava Ultimate (LU)).

METHODS

A total of 100 rectangular-shaped specimens with dimensions of 2 mm × 7 mm × 12 mm were obtained by sectioning three different CAD/CAM blocks and randomly divided into five subgroups according to the 30 days of mouthwash immersion protocol as follows: Control: artificial saliva, PVP-I: 1% povidone-iodine, HP: 1.5% hydrogen peroxide, CPC: mouthwash containing 0.075% cetylpyridinium chloride, EO: mouthwash containing essential oils. Microhardness, Ra, and ΔE values were measured at baseline and after 30 days of immersion protocols. Data were analyzed using the Wald Chi-square, two-way ANOVA, and post hoc Tukey tests.

RESULTS

The independent factors (materials and solutions) significantly influenced the microhardness and color (p < 0.001). Ra of the materials was not affected by any of the mouthwashes (p > 0.05). The microhardness and color of each material varied significantly after immersion in PvP-I and HP (p < 0.05). The highest percentage change in microhardness, Ra, and ΔE was found in LU immersed in PvP-I and HP mouthwashes, while the lowest change was found in ENA groups (p < 0.05).

CONCLUSION

Within the limitations of this study, it was found that the surface hardness and color of tested polymer-based composite CAD/CAM materials are susceptible to degradation and change after 30 days of immersion in 1% PvP-I and 1.5% HP mouthwashes.

Efficient removal of 2,4-D from solution using a novel antibacterial adsorbent based on tiger nut residues: adsorption and antibacterial study

We engineered a tiger nut residue (TNR, a low-cost agricultural waste material) through a facile and simple process to take advantage of the introduced functional groups (cetylpyridinium chloride, CPC) in the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in batch mode and further investigated its impingement on bacterial growth in a yeast-dextrose broth. The surface characterizations of the adsorbent were achieved through Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller method (BET), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The batch adsorption studies revealed that solution pH, adsorbent dose, temperature, and salt affected the adsorptive capacity of TNR-CPC. The equilibrium data were best fitted by Langmuir isotherm model with a maximum monolayer adsorption capacity of 90.2 mg g^-1 at 318 K and pH 3. Pseudo-second-order model best fitted the kinetics data for the adsorption process. Physisorption largely mediated the adsorption system with spontaneity and a shift in entropy of the aqueous solid-solute interface reflecting decreased randomness with an exothermic character. TNR-CPC demonstrated a good reusability potential making it highly economical and compares well with other adsorbents for decontamination of 2,4-D. The adsorption of 2,4-D proceeded through a probable trio-mechanism; electrostatic attraction between the carboxylate anion of 2,4-D and the pyridinium cation of TNR-CPC, hydrogen bonding between the hydroxyl (-OH) group inherent in the TNR and the carboxyl groups in 2,4-D and a triggered π-π stacking between the benzene structures in the adsorbate and the adsorbent. TNR-CPC reported about 99% inhibition rate against both gram-positive S. aureus and gram-negative E. coli. It would be appropriate to investigate the potential of TNR-CPC as a potential replacement to the metal oxides used in wastewater treatment for antibacterial capabilities, and its effects against airborne bacteria could also be of interest.

Cetylpyridinium chloride (CPC) reduces zebrafish mortality from influenza infection: Super-resolution microscopy reveals CPC interference with multiple protein interactions with phosphatidylinositol 4,5-bisphosphate in immune function

The COVID-19 pandemic raises significance for a potential influenza therapeutic compound, cetylpyridinium chloride (CPC), which has been extensively used in personal care products as a positively-charged quaternary ammonium antibacterial agent. CPC is currently in clinical trials to assess its effects on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) morbidity. Two published studies have provided mouse and human data indicating that CPC may alleviate influenza infection, and here we show that CPC (0.1 μM, 1 h) reduces zebrafish mortality and viral load following influenza infection. However, CPC mechanisms of action upon viral-host cell interaction are currently unknown. We have utilized super-resolution fluorescence photoactivation localization microscopy to probe the mode of CPC action. Reduction in density of influenza viral protein hemagglutinin (HA) clusters is known to reduce influenza infectivity: here, we show that CPC (at non-cytotoxic doses, 5-10 μM) reduces HA density and number of HA molecules per cluster within the plasma membrane of NIH-3T3 mouse fibroblasts. HA is known to colocalize with the negatively-charged mammalian lipid phosphatidylinositol 4,5-bisphosphate (PIP2); here, we show that nanoscale co-localization of HA with the PIP2-binding Pleckstrin homology (PH) reporter in the plasma membrane is diminished by CPC. CPC also dramatically displaces the PIP2-binding protein myristoylated alanine-rich C-kinase substrate (MARCKS) from the plasma membrane of rat RBL-2H3 mast cells; this disruption of PIP2 is correlated with inhibition of mast cell degranulation. Together, these findings offer a PIP2-focused mechanism underlying CPC disruption of influenza and suggest potential pharmacological use of this drug as an influenza therapeutic to reduce global deaths from viral disease.

Adsorption of bisphenol A and 2,4-dichlorophenol onto cetylpyridinium chloride-modified pine sawdust: a kinetic and thermodynamic study

Using biomass wastes as adsorbents is a promising option for organic waste reclamation, but unfortunately, their adsorption capacity is usually limited, especially for hydrophobic organic pollutants. To address this issue, this work prepared cetylpyridinium chloride (a cationic surfactant)-modified pine sawdust (CPC-PS) and further demonstrated their performance for hydrophobic bisphenol A (BPA) and 2,4-dichlorophenol (DCP) adsorption. Compared to the PS, the CPC-PS improved the maximum adsorption capacity for BPA and DCP by approximately 98% and 122%, respectively. The kinetic and thermodynamic analyses showed that the BPA and DCP adsorption onto the CPC-PS fitted the pseudo-second-order kinetics and the Freundlich model. After regeneration using NaOH, the adsorption capacity of the CPC-PS for BPA still maintained 80.2% of the initial value after five cycles. Based on the experimental results, the CPC-PS was proposed to enhance the BPA and DCP adsorption through the solubilization of hemimicelles for hydrophobic organic pollutants, the π-π stacking between benzene-ring structures, and the hydrogen binding between the adsorbents and the pollutants. This work provides a viable method to use surfactant-modified pine sawdust as effective adsorbents to remove hydrophobic pollutants.

Recent Development of Active Ingredients in Mouthwashes and Toothpastes for Periodontal Diseases

Periodontal diseases like gingivitis and periodontitis are primarily caused by dental plaque. Several antiplaque and anti-microbial agents have been successfully incorporated into toothpastes and mouthwashes to control plaque biofilms and to prevent and treat gingivitis and periodontitis. The aim of this article was to review recent developments in the antiplaque, anti-gingivitis, and anti-periodontitis properties of some common compounds in toothpastes and mouthwashes by evaluating basic and clinical studies, especially the ones published in the past five years. The common active ingredients in toothpastes and mouthwashes included in this review are chlorhexidine, cetylpyridinium chloride, sodium fluoride, stannous fluoride, stannous chloride, zinc oxide, zinc chloride, and two herbs—licorice and curcumin. We believe this comprehensive review will provide useful up-to-date information for dental care professionals and the general public regarding the major oral care products on the market that are in daily use.

Molecular Recognition of Imidazole Derivatives by Co(III)-Porphyrinsin Phosphate Buffer (pH = 7.4) and Cetylpyridinium Chloride Containing Solutions

Bymeans of spectrophotometric titration and NMR spectroscopy, the selective binding ability ofthe Co(III)-5,15-bis-(3-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Со(III)Р1) andCo(III)-5,15-bis-(2-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Со(III)Р2) towards imidazole derivatives of various nature (imidazole (L1), metronidazole (L2), and histamine (L3)) in phosphate buffer (pH 7.4) has been studied. It was found that in the case of L2, L3 the binding of the "first" ligand molecule by porphyrinatesCo(III)P1 and Co(III)P2 occurs with the formation of complexes with two binding sites (donor-acceptor bond at the center and hydrogen bond at the periphery of the macrocycle), while the "second" ligand molecule is added to the metalloporphyrin only due to the formation of the donor-acceptor bond at the macrocycle coordination center. The formation of stable complexes with two binding sites has been confirmed by density functional theory method (DFT) quantum chemical calculations and two-dimensional NMR experiments. It was shown that among the studied porphyrinates, Co(III)P2 is more selective towards to L1-L3 ligands, and localization of cobalt porphyrinates in cetylpyridinium chloride (CPC) micelles does not prevent the studied imidazole derivatives reversible binding. The obtained materials can be used to develop effective receptors for recognition, delivery, and prolonged release of drug compounds to the sites of their functioning. Considering that cetylpyridinium chloride is a widely used cationic biocide as a disinfectant, the designed materials may also prove to be effective antimicrobial agents.

Papain-cetylpyridinium chloride and pepsin-cetylpyridinium chloride; two novel, highly sensitive, concentration, digestion and decontamination techniques for culturing mycobacteria from clinically suspected pulmonary tuberculosis cases

Mycobacterial culture remains the gold standard for the diagnosis of tuberculosis. However, an appropriate digestion and decontamination method (DDM) is essential for the effective recovery of tubercle bacilli in culture. Therefore, the current study was designed to compare the performance of papain-cetylpyridinium chloride [papain-CPC] and pepsin-cetylpyridinium chloride [pepsin-CPC] DDMs against N-acetyl L-Cysteine-sodium hydroxide (NALC-NaOH) DDM for recovery of mycobacteria from clinically suspected pulmonary tuberculosis cases. To evaluate papain-CPC, pepsin-CPC and NALC-NaOH DDMs, sputum samples (N = 1381) were cultured on Löwenstein-Jensen medium and the results were compared. The papain-CPC DDM showed sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 93.27%, 71.7%, and 100%, respectively as compared to NALC-NaOH DDM. Similarly, pepsin-CPC DDM demonstrated sensitivity, specificity, positive predictive value and negative predictive value of 98.94%, 94.7%, 76.11%, and 99.81%, respectively. In summary, both papain-CPC and pepsin-CPC DDMs are highly sensitive and specific techniques for recovery of mycobacteria as compared to NALC-NaOH DDM. However, when the overall performances of all DDMs compared, papain-CPC DDM isolated increased number of mycobacterial isolates with comparatively higher numbers of colonies on LJ media than both pepsin-CPC and NALC-NaOH DDMs, indicating its potential to replace the NALC-NaOH DDM for recovery of mycobacteria from sputum samples.

Cetylpyridinium bromide/montmorillonite-graphene oxide composite with good antibacterial activity

In this study, a cetylpyridinium bromide (CPB)/montmorillonite-graphene oxide (GM) composite (GM-CPB) was prepared by loading CPB in a carrier of GM. The chemical structure, elemental composition, morphology, thermogravimetric analysis, antibacterial activity, sustained release property and cytotoxicity were analyzed. The loading rate of CPB in a GM carrier was higher than that of the graphene oxide (GO) carrier under the same loading condition. The antibacterial activity and sustained release performance of GM-CPB were also better than that of GO-CPB; furthermore, GM-CPB showed lower cytotoxicity than CPB.

Construction of hydrophobic interface on natural biomaterials for higher efficient and reversible radioactive iodine adsorption in water

For the pollution of radioactive materials, it is of great importance to develop efficient adsorbents for radioactive iodine adsorption in aqueous solution. In this work, a simple and green strategy was developed to construct hydrophobic surface on natural cotton fibers (n-CF) based on organic-soluble carbon dots (OCDs) for the first time. The results demonstrated the successful constructed hydrophobic n-CF@OCDs expressed excellent stability and selectivity for iodine (I₂) adsorption in water. The maximum adsorption capacity for I₂ on n-CF@OCDs is calculated to be 190.1 mg g^-1, which is about 6.8 times higher than that of n-CF (28.1 mg g^-1), this highly I₂ adsorption efficiency should be attributed to the hydrophobic properties of adsorbent. The adsorption mechanism was also discussed in this work. In addition, the adsorbed I₂ could be desorbed easily with a simple reductive process at ambient conditions, which can lead to not only the restore of I₂ but also the recycling of adsorbent, illustrating their good practicability. Furthermore, this universal strategy can also be used for construction of hydrophobic surface on various natural biomaterials, demonstrating its potential application in constructing of hydrophobic surface and used for the adsorption and removal of nonpolar pollutions or radioactive waste in aqueous solutions.

Synthesis, thermal and surface activity of cationic single chain metal hybrid surfactants and their interaction with microbes and proteins

A series of water-soluble metal functionalized surfactants have been prepared using commercially available surfactant cetyl pyridinium chloride and transition metal salts. These complexes were characterized in the solid state by elemental analysis, FTIR, 1H NMR and thermogravimetric analysis. The interfacial surface activity and aggregation behaviour of the metallosurfactants were analysed through conductivity, surface tension and small angle neutron scattering measurements. Our results show that the presence of metal ions as co-ions along with counter ions favours micellization at a low critical micellization concentration (CMC). Small angle neutron scattering revealed that the metallomicelles are of a prolate ellipsoidal shape and exhibit strong counterion binding. This article further describes the interaction of the metallosurfactants with transport protein Bovine Serum Albumin (BSA) using different spectroscopic techniques. A spectroscopic study was used to study the binding, interaction and quenching mechanism of BSA with the metallosurfactants. Gel electrophoresis (SDS-PAGE) and circular dichroism (CD) investigated the structural and conformational changes produced in BSA due to the metallosurfactants. The results indicate that there is an alteration in the secondary structure of BSA due to the electrostatic interaction between positive head groups and metal co-ions of the metallosurfactants and negatively charged amino acids of BSA. As the concentration increases, the α-helicity of BSA decreases and all the three studied metallosurfactants gave comparable results. Finally, the in vitro cytotoxicity and antimicrobial activity of the metallosurfactants were evaluated against erythrocytes and microorganisms, which showed prominent effects related to the presence of a metal ion in metallomicelles of the hybrid surfactants.

Innovative findings about ferrous oxalate dihydrate crystallization in simulated dihydrate phosphoric acid product

The basic fundamentals of ferrous oxalate dihydrate (FeC₂O₄.2H₂O) crystallization including supersaturation, nucleation and crystal growth in simulated dihydrate phosphoric acid product with and without cetyl pyridinium chloride (CPC) additive were studied. Oxalic acid and ferrous sulfate heptahydrate crystals were mixed with dilute phosphoric acid (28% P₂O₅) at 60 °C and the turbidity of the reaction mixture was measured at different time intervals. Induction time of ferrous oxalate dihydrate crystals was calculated at different supersaturation ratios ranging from 2.5 to 6.7. With increasing the supersaturation ratio, the induction time decreased. The nucleation rates are 46.4 × 10²⁸ nuclei cm^-3 s^-1 and 50.2 × 10²⁸ nuclei cm^-3 s^-1 at supersaturation ratio 6.7 with and without CPC addition, respectively. The surface energy increases with CPC addition compared to the baseline. In addition, the formed crystals are modified from cubic shape to rod-like shape with increasing CPC dose.

Simultaneous removal of nitrogen and phosphorus by cetylpyridinium bromide modified zeolite

In this study, surfactant modified zeolite-clinoptilolite (SMZ) by CPB (cetylpyridinium bromide) was used for simultaneous removal of ammonium, nitrate and phosphate in synthetic wastewater, and the sorption properties of SMZ were determined and compared with natural zeolite. Results showed that natural clinoptilolite had good affinity for ammonium (8.940 mg/g), but not for nitrate (0.427 mg/g) and phosphate (0.801 mg/g). With the increase of surfactant loading from 5 g/L to 40 g/L, the sorption capacity for nitrate increased from 0.462 mg/g to 4.661 mg/g. when the surfactant loading is 40 g/L, the SMZ has a phosphate adsorption capacity of 2.119 mg/g. The SMZ had a significant enhancement on nitrate and phosphate sorption, could simultaneously remove ammonium, nitrate and phosphate at specific conditions, with removal efficiency up to 85.2%, 83.1% and 56.7%, respectively. Orthogonal experiments showed that ammonium concentration was the most important factor for ammonium sorption on SMZ. Surfactant loading was the major factor for nitrate and phosphate sorption. With the increase of surfactant loading from 5 g/L to 40 g/L, the sorption capacity for nitrate increased from 0.462 mg/g to 4.661 mg/g. When the surfactant loading is 40 g/L, the SMZ has the best phosphate adsorption capacity 2.119 mg/g. Samples were characterized by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET). Semi-empirical quantum mechanics molecular simulation indicated that electrostatic attraction existed between CPB and dihydrogen phosphate ion. Results indicate that SMZs might have great potential of removing cations and anions simultaneously in the aquatic environment, which is good for eutrophication control and nutrients removal.

Cetylpyridinium chloride at sublethal levels increases the susceptibility of rat thymic lymphocytes to oxidative stress

Cetylpyridinium chloride (CPC) is an antimicrobial agent used in many personal care products, with subsequent release into the environment. Since CPC is found at low concentrations in river and municipal wastewater, its influence on wildlife is of concern. Therefore, in this study, we used flow cytometry to examine the effects of sublethal concentrations of CPC on rat thymic lymphocytes in order to characterize the cellular actions of CPC at low concentrations in the presence and absence of H₂O₂-induced oxidative stress. CPC treatment increased the population of living cells with phosphatidylserine exposed on the outer surface of their plasma membranes (a marker of early stage apoptosis), elevated intracellular Zn²⁺ levels, and decreased the cellular content of nonprotein thiols. CPC also potentiated the cytotoxicity of H₂O₂. Our results suggest that, even at environmentally relevant sublethal concentrations, CPC exerts cytotoxic effects under oxidative stress conditions by increasing intracellular Zn²⁺ concentration and decreasing the cellular content of nonprotein thiols. These findings indicate that, under some in vitro conditions, CPC is bioactive at environmentally relevant concentrations. Therefore, CPC release from personal care products into the environment may need to be regulated to avoid its adverse effects on wildlife.

Adsorption of the mycotoxin zearalenone by clinoptilolite and phillipsite zeolites treated with cetylpyridinium surfactant

In this study, organozeolites were prepared by treatment of the natural zeolites (clinoptilolite and phillipsite) with cetylpyridinium chloride (CP) equivalent to 50 and 100% of their external cation exchange capacities (ECEC). Organoclinoptilolites (ZCPs) and organophillipsites (PCPs) were characterized by FTIR spectroscopy, thermal analysis, determination of the point of zero charge and zeta potential. Adsorption of zearalenone (ZEN) by ZCPs and PCPs at pH 3 and 7 was investigated. Results showed that adsorption of ZEN increases with increasing amounts of CP at the zeolitic surfaces for both ZCPs and PCPs but the adsorption mechanism was different. Adsorption of ZEN by ZCPs followed a linear type of isotherm at pH 3 and 7 while ZEN adsorption by PCPs showed non linear (Langmuir and Freundlich) type of isotherm at both pH values. Different interactions between the ZEN molecule (or ion) and ZCPs and PCPs occurred: partition (linear isotherms) and adsorption in addition to partition (non linear isotherms), respectively. For the highest level of organic phase at the zeolitic surfaces, the maximum adsorbed amount of ZEN was 5.73mg/g for organoclinoptilolite and 6.86mg/g for organophillipsite at pH 3. Slightly higher adsorption: 6.98mg/g for organoclinoptilolite and 7.54mg/g for organophillipsite was achieved at pH 7. The results confirmed that CP ions at both zeolitic surfaces are responsible for ZEN adsorption and that organophillipsites are as effective in ZEN adsorption as organoclinoptilolites.

Mechanisms of CPB Modified Zeolite on Mercury Adsorption in Simulated Wastewater

A systematic study was carried out to analyze the effects of mercury(II) adsorption by surface modified zeolite (SMZ) and adsorption mechanism. Cetylpyridinium bromide (CPB) was used to prepare SMZ. The characterization methods by means of powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM) showed that both the surface and internal zeolite were covered with CPB molecules, but the main binding sites were surface. Results showed that the organic carbon and cation exchange capacity of the SMZ were 7.76 times and 4.22 times higher than those of natural zeolite (NZ), respectively. Zeta potentials before and after modification were measured at -7.80 mV and -30.27 mV, respectively. Moreover, the saturation adsorptive capacity of SMZ was 16.35 times higher than NZ in mercury-containing wastewater. The possible mechanisms of mercury elimination were surface adsorption, hydrophobic interaction, ion exchange, electricity neutralization. The adsorption process was affected little by competitive ions.

Antibacterial effects of conventional glass ionomer cement

OBJECTIVES

The antibacterial activity of conventional glass ionomer cement against three different microorganism strains alone and following incorporation of 1, 2 and 3% Benzalkonium Chloride and Cetylpyridinium Chloride was evaluated.

METHODS

Agar diffusion method was used to determine the inhibitory effect of the conventional glass ionomer cement ChemFlex on Streptococcus mutans, Lactobacillus casei and Actinomyces viscosus. Bacterial strains were inoculated into BHIB, and incubated in an anaerobic atmosphere (37 °C). From the bacteria grown in the liquid medium, the density of the inoculum was set to be equivalent to McFarland 2 standard. In Shaedler agar, 350 μL of the bacterial suspension were equally spread. Specimens (4 mm × 6 mm) were prepared from the cement without and with addition of 1, 2 and 3% Benzalkonium Chloride and Cetylpyridinium Chloride. The inhibition zones were determined after 48 hours, after 2, 7 and 21 days of incubation.

RESULTS

The combination ChemFlex + Benzalkonium Chloride has the best effect on the three analysed bacteria. The Benzalkonium Chloride antibacterial compound has a stronger antibacterial effect than Cetylpyridinium Chloride.

CONCLUSIONS

Glass ionomer cements can potentially be used as a medium for slow release of active antimicrobial components, and they have the potential to improve clinical outcomes of the cements (Tab. 3, Fig. 3, Ref. 31).

Controlled Clustering in Binary Charged Colloids by Adsorption of Ionic Surfactants

We report on the controlled clustering of oppositely charged colloidal particles by the adsorption of ionic surfactants, which tunes charge numbers Z of particles. In particular, we studied the heteroclustering of submicron-sized polystyrene (PS) and silica particles, both of which are negatively charged, in the presence of cetylpyridinium chloride (CPC), a cationic surfactant. The surfactant concentration Csurf was selected below the critical micelle concentration. As CPC molecules were adsorbed, Z values of the PS and silica particles decreased, inverting to positive when Csurf exceeded the isoelectric point Ciep. Hydrophobic PS particles exhibited much lower Ciep than hydrophilic silica particles. At Csurf valuess between their Ciep values, the particles were oppositely charged, and clustering was enabled. To explain the clustering behavior, we investigated adsorption isotherms of the CPC and screened-Coulomb-type pair potential. Expected applications of the present findings are the control of colloidal associations and construction of various particle types into heterogeneous colloidal clusters.

Rapid and sensitive method for analysis of nitrate in meat samples using ultra performance liquid chromatography-mass spectrometry

A sensitive and selective ultra performance liquid chromatography-mass spectrometric method has been developed for the quantitative analysis of nitrate in meat samples. Selected ion reaction (SIR) mode was adopted to identify and quantify the nitrate. Chromatographic analyses were performed on a BEH C-18 column with a mobile phase consisting of a surfactant (Cetylpyridinium chloride) and acetonitrile in equal ratio (50/50, v/v) at a flow rate of 0.4 mL min(-1). The limit of detection and limit of quantitation of the developed method was found to be 0.0599 and 0.1817 mg kg(-1), respectively. The linearity of the proposed method was checked in the concentration range of 0.5-10 mg kg(-1) with an excellent correlation coefficient (r) of 0.997. The recovery of the nitrate in the meat samples were in the range of 98.02-98.99%.

Pretreatment effects on the sorption of Cr(VI) onto surfactant-modified zeolite: Mechanism analysis

Adsorption of Cr(VI) onto different pretreated zeolites modified with cetylpyridinium chloride (CPC) is investigated using batch studies, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). The results indicate that acidification after alkalization is the most effective pretreatment method, and only alkalization would significantly reduce the sorption capability. This behavior is due to the precipitates, such as CaCO3 and MgCO3, generated after alkalization on zeolite surface interfere the formation of the CPC bilayer, which provides active sites for sorbing Cr(VI). The schematic of the adsorption mechanism is presented. The results indicate that developing a better understanding of the influence of different pretreatments is quite helpful and suggest that the content of Ca/Mg/Fe could be a good indication of the effectiveness of preprocessing.

Bentonite modification with hexadecylpyridinium and aluminum polyoxy cations and its effectiveness in Se(IV) removal

Usage of bentonite as a buffer material is suggested in radioactive waste repositories. Although bentonites have higher sorption ability to cations, they cannot adsorp anions due to negative surface charge. Nowadays, ongoing researches focus on increasing anion adsorption ability of the bentonites with modification. Organic-pillared bentonite (OPBent) was produced by modification of sodium bentonite with aluminum polyoxy and hexadecylpyridinium cations in this study. Variation in structure after modification was demonstrated by using different characterization techniques. Se removal efficiency of OPBent is investigated by using (75)Se, since selenium (Se) is one of the important long lived fission products found in radioactive waste and has toxic anionic species in an aqueous environment. The effect of reaction time, solid/liquid ratio, pH and concentration on the adsorption performance were examined. Se speciation and its effect onto adsorption were also investigated by measuring Eh-pH values under certain experimental conditions. Additionally, importance of the amount of Al-polyoxy cations used in modification was investigated by comparing these results with the results of other organic-pillared bentonite produced in our previous research. Experimental results confirmed that both cations were successfully placed into the bentonite interlayer and significant change in the host structure leads to increase Se adsorption. Consequently, bentonite modification improves its Se adsorption ability and further investigations are needed related to the usage of this adsorbent in other remediation studies especially in sorption of other anionic pollutants.

Resonance light scattering spectroscopy of procyanidin-CPB-DNA ternary system and its potential application

A new method for the determination of calf thymus DNA at nanogram level was proposed based on the enhanced resonance light scattering (RLS) signals of DNA in the presence of procyanidin and cetylpyridinium bromide dihydrate (CPB). Under the experimental conditions, the RLS intensity of DNA at 291.0 nm was greatly enhanced by procyanidin-CPB at pH 7.0. There was a good linear relationship (r=0.9993) between the enhanced RLS intensity (ΔI(RLS)) and DNA concentration of 0.0084-3.36 μg mL(-1). The limit of detection (LOD) was 2.27 ng mL(-1) (3S0/S). Three synthetic DNA samples were measured with satisfactory, and the recovery was 102.3-107.2%.

Development of sustained antimicrobial-release systems using poly(2-hydroxyethyl methacrylate)/trimethylolpropane trimethacrylate hydrogels

Reconstructive materials with sustained antimicrobial effects could be useful for preventing infectious diseases in an environment containing indigenous bacteria or fungi such as the oral cavity. With the objective of applying a non-biodegradable hydrogel to resin-based materials as a reservoir for water-soluble antimicrobials, novel hydrogels consisting of 2-hydroxyethyl methacrylate (HEMA) and trimethylolpropane trimethacrylate (TMPT) were fabricated. Cetylpyridinium chloride (CPC) was loaded into five hydrogels comprising different ratios of HEMA/TMPT, and their ability to release as well as to be recharged with CPC was examined in vitro. A polyHEMA/TMPT hydrogel comprising 50% HEMA/50% TMPT could be effectively loaded and recharged with CPC by immersion into a CPC solution, demonstrating the longest release of CPC, above the concentration required to inhibit bacteria and fungi. The binding of CPC to the hydrogels was mainly through hydrophobic interaction. Loading of CPC into a hydrogel by mixing CPC powder with the HEMA/TMPT monomer before polymerization resulted in marked extension of the initial CPC-release period. The CPC-pre-mixed hydrogel was confirmed to exhibit antibacterial activity by agar diffusion tests. It is possible to achieve a sustained release system for antimicrobials by pre-mix loading and recharging CPC into a 50% HEMA/50% TMPT hydrogel.

Nonionic surfactant greatly enhances the reductive debromination of polybrominated diphenyl ethers by nanoscale zero-valent iron: mechanism and kinetics

Nanoscale zero-valent iron (nZVI) has been considered as an effective agent for reductive debromination of polybrominated diphenyl ethers (PBDEs). But the high lipophilicity of PBDEs will hinder their debromination owing to the inefficient contact of PBDEs with nZVI. In this study, different ionic forms of surfactants were investigated aiming to promote PBDE debromination, and the beneficial effects of surfactant were found to be: nonionic polyethylene glycol octylphenol ether (Triton X-100, TX)>cationic cetylpyridinium chloride (CPC)>anionic sodium dodecyl benzenesulfonate (SDDBS). Except for with SDDBS, the promotion effect for PBDE debromination was positively related to the surfactant concentrations until a critical micelle concentration (CMC). The debromination process of octa-BDE and its intermediates could be described as a consecutive reaction. The corresponding rate constants (k) for the debromination of parent octa-BDE (including nona- to hepta-BDEs), the intermediates hexa-, penta-, and tetra-BDEs are 1.24 × 10(-1) h(-1), 8.97 × 10(-2) h(-1), 6.50 × 10(-2) h(-1) and 2.37 × 10(-3) h(-1), respectively.

The resonance Rayleigh light scattering spectral investigation on the interaction of DNA with camellia sinensis in the presence of CPC and its analytical application

A novel method with high sensitivity was designed for the determination of trace nucleic acids by using cationic surfactant cetylpyridinium chloride (CPC) and camellia sinensis (CS) as resonance Rayleigh light scattering (RLS) probes. It was found DNA could combine with CS and CPC in Tris-HCl buffer (pH=7.4). Under optimum conditions, the RLS intensity of DNA can be enhanced by CPC-CS obviously at 294nm, and the enhanced RLS intensity was directly proportional to DNA concentration in the range from 0.024 to 3.48μgmL(-1) with a good linear relationship (r=0.9940). The limit of detection (LOD) was 1.49ngmL(-1) (S/N=3). In addition, the effects of some interferences including K(+), Na(+), Mg(2+), Zn(2+), Cu(2+), Ca(2+) and glucose on the determination were studied. The developed RLS assay was successfully applied to three synthetic samples to measure DNA, the recovery was 94.7-106.3% and RSD was 0.58-3.33%.