Octadecyltrimethylammonium Bromide Research Articles

Exploring the cationic surfactant adsorption efficiency at concentrations relative to the critical micelle concentration by SA/SiO2 microspheres

Studying the adsorption behavior of cationic surfactants can help to develop more effective strategies to limit their dispersion in the environment. However, there have few studies on the adsorption of cationic surfactants from the perspective of critical micelle concentration (CMC). In this study, with cetyltrimethylammonium bromide (CTAB) and octadecyl trimethylammonium bromide (OTAB) serving as the model cationic surfactants, the effect of CMC on the adsorption behavior of cationic surfactant onto the surface of sodium alginate/silica (SA/SiO2) microspheres was systematically revealed. The adsorption mechanism relative to CMC was investigated under different conditions, including surfactant concentration, pH, temperature, and adsorption time. The results suggest that at identical concentrations, the smaller the CMC value of the cationic surfactants, the greater the adsorption amount (qt). qt for CTAB and OTAB were 583.2 and 678.0 mg/g respectively, with the concentration higher than their CMC value. When the concentration was lower than the CMC value of the cationic surfactants, qt for CTAB and OTAB were 123.2 and 138.7 mg/g, respectively. The CMC value of CTAB was lower than that of OTAB under identical conditions, suggesting that the adsorption of cationic surfactants is related to their CMC. These results are beneficial for the removal of cationic surfactants by adsorption methods.

Carbamazepine adsorption with a series of organoclays: removal and toxicity analyses

Organoclays have been used as efficient adsorbents for pharmaceutical pollutants present in waters. Carbamazepine (CBZ) is one of the drugs most frequently found in water bodies. In this study, four organoclays were prepared by modifying bentonite with the cationic surfactants hexadecyltrimethylammonium bromide (HDTMA) and octadecyltrimethylammonium bromide. The synthesized materials were characterized by XRD, CHN, FTIR, TG, BET and SEM analyses, confirming organophilization. The surfactants were interspersed in different arrangements in the interlayer space. CBZ sorption was investigated through batch equilibrium experiments, under variation of the pH, contact time, dosage of adsorbent, and initial drug concentration. Changes in pH showed no adsorption influence. CBZ sorption by the organoclays followed a pseudo-second-order kinetics. The best sorption performance was obtained for the BCN1-HDTMA100 clay, with a capacity of 34.34 ± 1.41 mg g−1, about ten times greater than the unmodified bentonite under the same conditions. This may be attributed to the higher surfactant content. The adsorption isotherm at 25 ºC showed linear behavior. Toxicity tests of the organoclays and corresponding medium in presence of CBZ were carried out. This is a novelty report. Most of the organoclays had no toxicity against Artemia salina. The toxicity of the medium after adsorptive treatment was eliminated. Organoclay-CBZ hybrids were also characterized after adsorption. FTIR and TG analyzes confirmed the incorporation of the drug. Hydrophobic interaction was the dominant contribution evaluated to the adsorption of CBZ. The results demonstrated that organoclays can be a promising alternative adsorbent for the removal of pharmaceutical pollutants in water remediation.

Rheological and Tribological Properties of Zirconium Phosphate (ZrP) Intercalation Compounds as Lubricating Grease Thickener

This research studied layered zirconium phosphate intercalated with octadecyltrimethylammonium bromide (STAB-ZrP) as a thickener by thickening five types of base oils. The thickening ability and fluidity behavior of STAB-ZrP gel were evaluated using rheological measurements. The tribological properties of STAB-ZrP gel were investigated using a reciprocating tribometer under temperatures of 25 °C and −15 °C. The rheological results showed that STAB-ZrP gel had grease-like characteristics. Naphthenic and alkyl naphthalene as the base oil can lead to the higher thickening ability. Naphthenic oil maintained the most colloidal stability at 25 °C and −15 °C. STAB-ZrP gel exhibited superior anti-wear and friction reduction, owing to the formation of a solid protective film on the contact interface. The layered structure and morphology of STAB-ZrP after thickening were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). This research established the relationship of STAB-ZrP with base oils in terms of their performance. STAB-ZrP acts as both a thickener and a solid additive in the STAB-ZrP gel system. This study can serve a beneficial trial for future preparations of lubricating grease.

Stabilization of heavy metals in solid waste and sludge pyrolysis by intercalation-exfoliation modified vermiculite

Increasing amounts of solid waste and sludge have created many environmental management problems. Pyrolysis can effectively reduce the volume of solid waste and sludge, but there is still the problem of heavy metal contamination, which limits the application of pyrolysis in environmental management. The intercalated-exfoliated modified vermiculite (IEMV) by intercalators of sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide were used to control the release of Cd, Cr, Cu, Zn and Pb during pyrolysis process of sludge or solid waste. The retention of heavy metals in sludge was generally better than that in solid waste. The IEMV by octadecyltrimethylammonium bromide as the intercalator calcined 800 °C (STAB-800) was the best additive for heavy metal retention, and the retention of Cr, Cu and Zn was significantly better than that of Pb and Cd. Cr, Cu, Zn and Pb were at low risk, while Cd had considerable risk under certain circumstances. New models were proposed to comprehensively evaluate the results of the risk and forms of heavy metals, and the increasing temperature was beneficial in reducing the hazards of heavy metals by the addition of STAB-800. The reaction mechanism of heavy metals with vermiculite was revealed by simulation of reaction sites, Fukui Function and Frontier Molecular Orbital. Thermal activation-intercalated-exfoliated modified vermiculite (T-IEMV) is more reactive and had more active sites for heavy metals. Mg atoms and outermost O atoms are the main atoms for T-IEMV to react with heavy metals. The Cr, Cu and Zn have better adsorption capacity by T-IEMV than Pb and Cd. This study provides a new insight into managing solid waste and sludge and controlling heavy metal environmental pollution.

Influence of the Mesoporosity of Hierarchical ZSM-5 in Toluene Alkylation by Methanol.

Among the different strategies to design highly shape-selective ZSM-5 to obtain para-xylene through toluene alkylation with methanol, the introduction of mesopores to increase reactant and product diffusion has been proposed but barely studied. In this study, we prepared mesoporous ZSM-5 catalysts, named ZSM5-MT(x), from commercial ZSM-5 (Si/Al = 15), using a two-step micelle-templating procedure with octadecyltrimethylammonium bromide as a surfactant in basic medium (x = NaOH/Si). These materials were used as catalysts for the alkylation of toluene by methanol at a low contact time to avoid thermodynamic equilibrium of the xylene isomers. Compared to the parent ZSM-5, the mesoporous ZSM5-MT(x) catalysts did not improve the para-xylene selectivity, revealing that the strategy of increasing diffusion in the catalyst is not a good strategy to follow. However, ZSM5-MT(0.5) showed less deactivation on stream than the parent ZSM-5. Therefore, introducing mesopores to ZSM-5 could be interesting to explore, combined with another strategy of shape selectivity, such as the passivation of the external surface acidity.

Evaluation and Application of Efficient Gelled Acid for Carbonate Formation Fracturing.

In the middle and west of Sichuan Basin, the targeted carbonate formation exhibits features of deep burial and high temperatures at present. In order to obtain better acid fracturing results, the efficient gelled acid developed was investigated based on the carbonate formation characteristics. At the same time, the field application was conducted to prove its adaptability and effectiveness. The high-effective thickener is mainly polymerized by DMC and an allyl octadecyl trimethyl ammonium bromide monomer and a very small amount of diallyl polyethylene glycol. The efficient gelled acid has good compatibility with carbonate formation and formation water, and its thermal stability is great that the viscosity could obtain 25 mPa·s at a temperature of 180 °C after shearing at 30 min. Furthermore, compared with conventional gelled acid, the friction reduction rate of efficient gelled acid is higher of over 7-12%. Also, the induced fracture conductivity is more than 20 D·cm at a closure stress of 60 MPa, which is higher than that of conventional gelled acid with 16.81 D·cm. In addition, during the acidification fracturing of Well PS, the efficient gelled acid system exhibits a good friction reduction property. The flow rate could reach 6 m3·min-1 and the obvious pressure drop could be observed, which indicated that the efficient gelling acid reacted with the carbonate formation, creating acidified fractures. The test production of Well PS is 23 × 104 m3·d-1 and the acid fracturing adopted by the efficient gelled acid obtains a great break at a high-temperature carbonate formation.

Electroreductive Defluorination of Unsaturated PFAS by a Quaternary Ammonium Surfactant-Modified Cathode via Direct Cathodic Reduction.

Remediation of per- and polyfluoroalkyl substances (PFAS) in groundwater remains a technological challenge due to the trace concentrations of PFAS and the strength of their C-F bonds. This study investigated an electroreductive system with a quaternary ammonium surfactant-modified cathode for degrading (E)-perfluoro(4-methylpent-2-enoic acid) (PFMeUPA) at a low cathodic potential. A removal efficiency of 99.81% and defluorination efficiency of 78.67% were achieved under -1.6 V (vs Ag/AgCl) at the cathode modified by octadecyltrimethylammonium bromide (OTAB). The overall degradation procedure started with the adsorption of PFMeUPA onto the modified cathode. This adsorption process was promoted by hydrophobic and electrostatic interactions between the surfactants and PFMeUPA, of which the binding percentage, binding mode, and binding energy were determined via molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The step-wise degradation pathway of PFMeUPA, including reductive defluorination and hydrogenation, was derived. Meanwhile, C-F bond breaking with direct electron transfer only was achieved for the first time in this study, which also showed that the C═C bond structure of PFAS facilitates the C-F cleavage. Overall, this study highlights the crucial role of quaternary ammonium surfactants in electron transfer and electrocatalytic activities in the electroreductive system and provides insights into novel remediation approaches on PFAS-contaminated groundwater.

Molecular dynamics and thermo physical properties of solid catanionic surfactants composed of octadecyltrimethylammonium bromide and n-alkanoic acids

Two mixed surfactants comprising cationic octadecyltrimethylammonium bromide CH3(CH2)17N+(CH3)3Br− (C18TAB) modified with dodecanoic C12H24O2 (DDA) or hexadecanoic C16H32O2 (HDA) acids have been studied in the solid state in a wide temperature range (25–150 °C). The molecular dynamics and thermotropic properties of acid-modified asymmetric DDA-C18TAB and symmetric HDA-C18TAB surfactants were investigated using DSC measurements and temperature-variable FTIR spectroscopy complemented by room-temperature powder X-ray diffraction. XRD showed a formation of a new layered compound, the acid-modified C18TAB mixed surfactant comprising a hydrophobic moiety formed by two alkyl chains of different lengths. DSC measurements revealed the difference in thermal behavior between symmetric and asymmetric mixed surfactants showing successive phase transitions and several polymorphs in the solid state. With FT-IR spectroscopy, the phase transitions seen in DSC were identified as related to subtle lattice rearrangements in the low-temperature phases C1C2, the trans-gauche conformational disorder and rotational motions of methylene chains followed with lattice instabilities in the intermediate phases C3 and C4, and finally rotational disorder of the alkyl chains and the ionic layer in the high temperature phase H. For the first time, the stabilization effect of DDA acid on the bilayer structure of C18TAB was found.

Efficient Diesel Desulfurization by Novel Amphiphilic Polyoxometalate-Based Hybrid Catalyst at Room Temperature.

Amphiphilic hybrid catalysts were prepared by modifying [SMo12O40]2- with tetrabutylammonium bromide (TBAB), 1-butyl-3-methylimidazole bromide (BMIMBr) and octadecyl trimethyl ammonium bromide (ODAB), respectively. The prepared catalysts were characterized by IR, XRD, SEM, TG and XPS. The desulfurization performance of the catalysts was investigated in model oil and actual diesel using hydrogen peroxide (H2O2) as an oxidant and acetonitrile as an extractant. All catalysts exhibited favorable activity for removing sulfur compounds at room temperature. Dibenzothiophene (DBT) can be nearly completely removed using SMo12O402--organic catalysts within a short reaction time. For different sulfur compounds, the [TBA]2SMo12O40 catalyst showed a better removal effect than the [BMIM]2SMo12O40 and [ODA]2SMo12O40 catalyst. The [TBA]2SMo12O40 dissolved in extraction solvent could be reused up to five times in an oxidative desulfurization (ODS) cycle with no significant loss of activity. The [BMIM]2SMo12O40 performed as a heterogeneous catalyst able to be recycled from the ODS system and maintained excellent catalytic activity. The catalysts showed a positive desulfurization effect in real diesel treatment. Finally, we described the ODS desulfurization mechanism of DBT using SMo12O402--organic hybrid catalysts. The amphiphilic hybrid catalyst cation captures DBT, while SMo12O402- reacts with the oxidant H2O2 to produce peroxy-active species. DBT can be oxidized to its sulfone by the action of peroxy-active species to achieve ODS desulfurization.

Effects of surfactant head group modification on vertically oriented mesoporous silica produced by the electrochemically assisted surfactant assembly method.

Production of mesoporous silica films with vertically oriented pores has been a challenge since interest in such systems developed in the 1990s. Vertical orientation can be achieved by the electrochemically assisted surfactant assembly (EASA) method using cationic surfactants such as cetyltrimethylammonium bromide (C16TAB). The synthesis of porous silicas using a series of surfactants with increasing head sizes is described, from octadecyltrimethylammonium bromide (C18TAB) to octadecyltriethylammonium bromide (C18TEAB). These increase pore size, but the degree of hexagonal order in the vertically aligned pores reduces as the number of ethyl groups increases. Pore accessibility is also reduced with the larger head groups.

Octadecyltrimethylammonium Bromide Micelles as a Template in the Seedless Synthesis of Gold Nanorods

Octadecyltrimethylammonium Bromide Micelles as a Template in the Seedless Synthesis of Gold Nanorods

Construction of a liquid Crystal-based Sensing Platform for the Sensitive Detection of Catalase in Human Serum

A briefness, convenient, label-free and sensitive liquid crystal (LC) sensing platform is demonstrated to detect catalase in human serum with the assistance of CeO2 nanomaterials and the single-stranded DNA (ssDNA). In the presence of H2O2 and ssDNA/CeO2 nanomaterials complex, a colourful optical appearance of LCs doped with octadecyl-trimethylammonium bromide (OTAB) was observed under a polarized optical microscopy (POM), which is corresponding to the oblique alignment of LCs at the aqueous-LC interface. This can be ascribed to the disruption of the OTAB monolayers by ssDNA that is set free from the surface of CeO2 nanomaterials in the presence of H2O2. The stronger coordination interaction between H2O2 and CeO2 nanomaterials causes a replacement for ssDNA. Interestingly, with the hydrolysis of H2O2 by catalase, the LCs exhibit a dim image, which suggests the upright alignment of LCs at the aqueous-LC interface. It is because there is no free ssDNA discharged into the aqueous solution after the hydrolysis of H2O2. Hence, by observing the changes of colourful and dim optical images of LCs, catalase can be analyzed with remarkable sensitivity and excellent specificity. The detection limit of catalase reaches as low as ∼ 1 mU/mL. Besides, the detection of catalase in human serum is also successfully achieved, which makes this assay meets the requirement of practical applications. Therefore, this work offers an effective and appealing strategy for the real-time and label-free detection of catalase in human serum.

Liquid crystal-based sensitive and selective detection of uric acid and uricase in body fluids

The abnormal levels of uric acid (UA) in body fluids are associated with gout, type (II) diabetes, leukemia, Lesch-Nyhan syndrome, uremia, kidney damage, and cardiovascular diseases. Also, the presence of uricase (UOx) symbolizes genetic disorders and corresponding complications. Therefore, the detection of UA and UOx in the body fluids is significant for clinical diagnosis. 4-Cyano-4′-pentylbiphenyl (5CB, a nematic liquid crystal (LC)) was doped with octadecyl trimethylammonium bromide (OTAB, a cationic surfactant), which formed a self-assembled monolayer at the aqueous/5CB interface. The UOx-catalyzed oxidation of UA yielded H2O2, releasing the single-strand deoxyribonucleic acid (ssDNA) from the nanoceria/ssDNA complex. The interaction of the released ssDNA with OTAB disrupted the monolayer at the aqueous/5CB interface, which resulted in a dark to bright change when observed through a polarized optical microscope. The LC-based sensor allowed the detection of UA with a linear range of 0.01–10 μM and a limit of detection (LOD) of 0.001 μM. The UA detection was also performed in human urine samples and the results were comparable to that of a standard commercial colorimetric method. Similarly, the detection of UOx was performed, with a noted linear range of 20–140 μg/mL. The LOD was as low as 0.34 μg/mL. The detection of UOx was also demonstrated in human serum samples with excellent performance. This method provides a robust sensing platform for the detection of UA and UOx and has potential for applications in clinical analysis.

Enhanced thermal conductivity of poly(aryl ether nitrile ketone)/functionalized boron nitride composites by electrospinning–hot press technique

AbstractIn this study, poly(aryl ether nitrile ketone)/functionalized boron nitride (PEK‐CN/f‐BN) composites fibers were prepared by solution blending followed by electrospinning technique. And the thermally conductive PEK‐CN/f‐BN nanocomposites were fabricated via hot press method. Octadecyltrimethylammonium Bromide (OTAB) was performed to functionalize the surface of boron nitride (BN) fillers, which were utilized as thermally conductive fillers to fabricate the corresponding PEK‐CN/BN composites. The thermal conductivity coefficient (λ) of the PEK‐CN/f‐BN composites (25 wt% f‐BN) was 0.702 W/mK, and the PEK‐CN/BN composites (25 wt% unfunctionalized BN) was 0.649 W/mK, whose λ is more than 200% higher than the λ of pure PEK‐CN (0.251 W/mK). Meantime, compared to the pure PEK‐CN, the glass‐transition temperature (Tg) of the PEK‐CN/f‐BN composites was increased from 228.10 to 232.98°C, and the thermal stability of the PEK‐CN/f‐BN composites has been improved as well. It was also noticed that, under the ideal electrospinning conditions, when the content of BN and f‐BN attached to 25 wt%, the storage modulus (E′), loss modulus (E″), and dielectric loss tangent (tan δ) values of the PEK‐CN/BN composites and PEK‐CN/f‐BN composites were higher than that of pure PEK‐CN.

Effects of three surfactants on the degradation and environmental risk of metolachlor in aquatic environment

Surfactants and pesticides can be simultaneously detected in the environment by the reason of their widespread use and large amounts of emissions. Due to the special amphipathicity of surfactants, it may have special effects on the environmental behaviors and toxic effects of other substances in the environment. There are few relevant studies at present. In this study, the effects of three surfactants on the degradation of the amide pesticide metolachlor in water-sediment system were investigated. The study found that the three surfactants had no significant effect on the degradation of metolachlor in the system at environmental concentrations. However, at critical micelle concentration, cationic surfactant octadecyl trimethyl ammonium bromide and nonionic surfactant nonylphenol polyoxyethylene ether promoted the degradation of metolachlor in water-sediment system. Anionic surfactant odium dodecylbenzene sulfonate (SDBS) prolonged the degradation half-life of metolachlor. The presence of surfactants not only affected the environmental behavior of pesticides. When they coexisted with pesticides, the joint toxicity to aquatic organisms cannot be ignored. This study found that the combined effects of three surfactants and metolachlor on the acute developmental toxicity of zebrafish embryos were all synergistic effects. The combined effects of two ionic surfactants and metolachlor on the acute toxicity of adult zebrafish were synergistic effects. Further study showed that co-exposure of SDBS and metolachlor increased the absorption of metolachlor by zebrafish. Combined exposure of SDBS and metolachlor caused oxidative stress in brain, gill and liver of zebrafish. The results showed that the simultaneous presence of anionic surfactants and pesticides in the environment may increase the environmental risk of pesticides.

Polyaniline nanowire arrays generated through oriented mesoporous silica films: effect of pore size and spectroelectrochemical response.

Indium-tin oxide electrodes modified with vertically aligned silica nanochannel membranes have been produced by electrochemically assisted self-assembly of cationic surfactants (cetyl- or octadecyl-trimethylammonium bromide) and concomitant polycondensation of the silica precursors (tetraethoxysilane). They exhibited pore diameters in the 2-3 nm range depending on the surfactant used. After surfactant removal, the bottom of mesopores was derivatized with aminophenyl groups via electrografting (i.e., electrochemical reduction of in situ generated aminophenyl monodiazonium salt). These species covalently bonded to the ITO substrate were then exploited to grow polyaniline nanofilaments by electropolymerization of aniline through the nanochannels. Under potentiostatic conditions, the length of polyaniline wires is controllable by tuning the electropolymerization time. From cyclic voltammetry characterization performed either before or after dissolution of the silica template, it appeared that both the polyaniline/silica composite and the free polyaniline nanowire arrays were electroactive, yet with much larger peak currents in the latter case as a result of larger effective surface area offered to the electrolyte solution. At identical electropolymerization time, the amount of deposited polyaniline was larger when using the silica membrane with larger pore diameter. All polyaniline deposits exhibited electrochromic properties. However, the spectroelectrochemical data indicated more complete interconversion between the coloured oxidized form and colourless reduced polyaniline for the arrays of nanofilaments in comparison to bulky films. In addition, the template-free nanowire arrays (i.e., after silica dissolution) were characterized by faster electrochromic behaviour than the polyaniline/silica hybrid, confirming the potential interest of such polyaniline nano-brushes for practical applications.

Zinc cyanide removal by precipitation with quaternary ammonium salts

In gold-processing plants, the final tailing containing metal cyanide species is typically treated using various oxidation methods to produce the main source of process water, which is subsequently recycled to the upstream units, such as flotation units. In some gold-processing plants, a considerable amount of metal cyanide species such as zinc cyanide remains in process water, despite the cyanide destruction process. Because residual zinc cyanide complexes can depress gold flotation, the amount of process water must be decreased such that it can be recycled to a flotation circuit. Previous studies report that the critical concentration of zinc cyanide, measured based on the total cyanide concentration during flotation depression, is 0.4 mmol/L. In the present study, the feasibility of using quaternary ammonium salts to precipitate zinc cyanide complexes to less than the critical concentration was studied. The results showed that 92.17% of 60 mg/L of cyanide and 88.86% of 50 mg/L of zinc (molar ratio Zn/CN = 1:3) can be removed using 0.4 g/L of octadecyl trimethyl ammonium bromide at a pH of 10. The concentration of the residual CN cyanide was less than the critical concentration. This indicates that the abovementioned process is effective when nonpolar organic contaminants and moderate amounts of salt (<50 mmol/L) are present. This work revealed that the precipitation process can be used as an advanced treatment method for process water subjected to oxidation treatment.

Antibacterial effects of octadecyl trimethylammonium micelle-clay complex against bacterial eye pathogens: potential as a contact lens disinfectant.

In this study, we utilized a micelle-clay complex composed of the surfactant octadecyltrimethylammonium bromide and montmorillonite clay and evaluated its antibacterial effects. Using Pseudomonas aeruginosa, Staphylococcus epidermidis, and Micrococcus luteus, bactericidal assays were performed to determine the effects of ODTMA-clay complex on the viability of bacterial pathogen at various doses and different intervals of time. Cytotoxicity assays were performed to investigate ODTMA-clay complex effects on human cells, as determined by release of intracellular lactate dehydrogenase. The results revealed that ODTMA-clay complex abolished bacterial viability at 100μg/mL within 45min against P. aeruginosa, S. epidermidis, and M. luteus. Cytotoxicity assays revealed that ODTMA-clay complex exhibited minimal toxicity of the human cells. Rapid and potent antibacterial effects of ODTMA micelle-clay complex were observed in vitro; however, research is needed to determine precise formulation of contact lens disinfectants comprising ODTMA micelle-clay complex. Additionally, studies should be conducted using in vivo models of keratitis, progressing to pre-clinical and clinical trials. ODTMA micelle-clay complex is an ideal candidate to be incorporated in a novel contact lens disinfectant given the cost-effectiveness and ease of application and can be incorporated as an effective preventative strategy.

Enhanced Antimicrobial Action of Chlorhexidine Loaded in Shellac Nanoparticles with Cationic Surface Functionality.

We report on an active nanocarrier for chlorhexidine (CHX) based on sterically stabilized shellac nanoparticles (NPs) with dual surface functionalization, which greatly enhances the antimicrobial action of CHX. The fabrication process for the CHX nanocarrier is based on pH-induced co-precipitation of CHX-DG from an aqueous solution of ammonium shellac and Poloxamer 407 (P407), which serves as a steric stabilizing agent. This is followed by further surface modification with octadecyl trimethyl ammonium bromide (ODTAB) through a solvent change to yield cationic surface functionality. In this study, we assessed the encapsulation efficiency and release kinetics of the novel nanocarrier for CHX. We further examined the antimicrobial effects of the CHX nanocarriers and their individual components in order to gain better insight into how they work, to improve their design and to explore the impacts of their dual functionalization. The antimicrobial actions of CHX loaded in shellac NPs were examined on three different proxy microorganisms: a Gram-negative bacterium (E. coli), a yeast (S. cerevisiae) and a microalgae (C. reinhardtii). The antimicrobial actions of free CHX and CHX-loaded shellac NPs were compared over the same CHX concentration range. We found that the non-coated shellac NPs loaded with CHX showed inferior action compared with free CHX due to their negative surface charge; however, the ODTAB-coated, CHX-loaded shellac NPs strongly amplified the antimicrobial action of the CHX for the tested microorganisms. The enhancement of the CHX antimicrobial action was thought to be due to the increased electrostatic adhesion between the cationic surface of the ODTAB-coated, CHX-loaded shellac NPs and the anionic surface of the cell walls of the microorganisms, ensuring direct delivery of CHX with a high concentration locally on the cell membrane. The novel CHX nanocarriers with enhanced antimicrobial action may potentially find applications in dentistry for the development of more efficient formulations against conditions such as gingivitis, periodontitis and other oral infections, as well as enabling formulations to have lower CHX concentrations.

A stable liquid crystals sensing platform decorated with cationic surfactant for detecting thrombin

A liquid crystals (LCs) sensing platform to detect thrombin was demonstrated based on high specificity of aptamer recognition. Initially, LCs doped with a cationic surfactant, octadecyl-trimethylammonium bromide (OTAB), adopted homeotropic alignment corresponding to dark optical image. Upon introduction of thrombin aptamer, the orientational transition of LCs from homeotropic to tilted state occurred due to the electrostatic interaction between it and OTAB. And accordingly a visual dark-to-bright alteration was observed for the polarized light microscope (POM) image of LCs. In the presence of thrombin with which the aptamer preferred to bind, OTAB released could induce the vertical arrangement of LCs and a dark optical image was regained. Therefore, by observing the changes of bright and dark optical appearances for LCs, thrombin could be analyzed with a detection limit of ~ 136 nM. The LCs sensing system, assisted with the specific combination of target molecule and its corresponding aptamer, reveals a simple and effective way to achieve label-free and low-cost detection of biomolecules in related clinic diagnosis.