Zeta Potential Distribution Research Articles

Application of submerged membrane bioreactor technology for the treatment of high strength dairy wastewater

Abstract In this study, an aerobic submerged membrane bioreactor (sMBR) was used for the treatment of dairy wastewater at 15 h of hydraulic retention time (HRT) and 40 d of sludge retention time (SRT) with constant permeate flux (9.5 L.m-3.d-1(LMH)). The COD, ammonia-nitrogen (NH3-N) and orthophosphate (PO4-P) removal efficiencies were 98.2%, 95.4% and 88.9%, respectively. The results demonstrated that sMBR was a suitable and effective treatment for removal of organic matter and nutrients for treating dairy wastewater. The properties of the activated sludge, such as extracellular polymeric substances (EPS) and soluble microbial products (SMP) concentration, protein and carbohydrate, relative hydrophobicity, zeta potential and floc size distribution were also investigated. According to the results obtained, the total EPS content was lower than that of domestic wastewater treatment by MBR technology.

Cytotoxicity Enhancement of Paclitaxel by Loading on Stearate-g-dextran Micelles on Breast Cancer Cell Line MCF-7

Objective:Paclitaxel (PTX) is a chemotherapeutic agent used for treating breast cancer. The study aimed to prepare PTX loaded dextran stearate (Dex-SA) and evaluate its efficacy against human breast cancer cell line MCF-7.Methods:Dex-SA/PTX micelles were prepared by dialysis method. The micelles size, zeta potential and particle size distribution were measured by dynamic laser light scattering method. Amount of loaded PTX on the polymer measured by HPLC. Release profiles of the drug from the micelles were obtained in buffer (phosphate pH=7.4). Then the cytotoxicity of blank micelles, Dex-SA/PTX micelles and free PTX were evaluated in the MCF-7 cells by MTT method.Result:Loading efficiency of PTX on the Dex-SA was measured about 84.24±9.07%. The smallest particles size was about 193.9±7.1 nm but the other formulation with larger particle size had better zeta potential (-33.5±6.74 mV). The drug release from the micelles was slowly and reached steady state after about 12 hours. The cytotoxicity experiment showed that Dex-SA/PTX micelles have more cytotoxicity compared to free PTX against MCF7 cell lines.Conclusions:Dex-SA polymeric micelle is a suitable carrier for hydrophobic cytotoxic drugs such as PTX.

Magnetic polystyrene–palygorskite nanocomposite obtained by heterogeneous phase polymerization to apply in the treatment of oily waters

ABSTRACTWater contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The organo‐Fe3O4‐palygorskite nanoparticles were coated with polystyrene, forming water repellent and oil absorbing surfaces to promote the removal of oil from the surfaces of nanocomposites by applying an external magnetic field. X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy, zeta potential and size distribution measurement, surface area determination by BET, density measurement by He pycnometry, carbon grade determination, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, Raman spectroscopy, and evaluation of hydrophobicity by contact angle were used to characterize the nanoparticles. The magnetic nanocomposite obtained showed excellent hydrophobicity, around 78° contact angle. In addition, oil removal capability tests were also performed, according to which the preliminary results indicated removal of approximately 98% of oil in synthetic oily water samples. The oil–water separation using this magnetic nanocomposite provides a promising alternative strategy for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46162.

Preparation of starch nanocrystals through enzymatic pretreatment from waxy potato starch

A comparative experiment about the production of starch nanocrystals (SNCs) with/without glucoamylase enzymatic pretreatment by sulfate acid hydrolysis from waxy potato starch (WPS) was employed in the present study. The research focused on the enhancement of the preparation efficiency while improving the dispersion of SNCs at the same time. The enzymatic pretreatment resulted in the decrease of acid hydrolysis duration. The minimum size and best dispersibility of nanocrystals was obtained after 5 days of hydrolysis. X-ray diffraction confirmed the increase of crystallinity (from 33% to 50.8%) and the polymorphic transitions (B–A) for nanocrystals harvested at day 5. The structure of nanocrystals was characterized by FT-IR, which suggested the presence of sulfate ester on the surface of SNCs. Zeta potential and size distribution revealed the prominent stability and dispersibility of nanocrystals at pH 7.0. SEM and TEM revealed that SNCs had square shapes with particle sizes ranging from 50 to 100 nm.

Investigation of the thermophysical properties and stability performance of non-covalently functionalized graphene nanoplatelets with Pluronic P-123 in different solvents

The employment of nanofluids involving the dispersion of nanomaterials in the base fluid has become a major interest of the researchers due to great potential in enhancing the thermophysical properties and heat transfer coefficients. The stability of nanoparticles in base fluids is a major concern with heat transfer applications. The main purpose of this research was to study the stability of graphene nanoplatelets (GNPs) in the presence of Pluronic P-123 surfactant (P-123) in aqueous media and to compare with other common surfactants such as sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX). Each of the surfactants was mixed with GNPs at different ratios of 1:1, 1:2, 1:3 and 1:4. Then, the best ratio with the most stable sample was selected and compared with other samples. The stability of samples was evaluated by using UV-vis spectrometry, zeta potential and particle size distribution. The viscosity and thermal conductivity of the best sample were also measured at different temperatures. High resolution-transmission Electron Microscopy (HR-TEM) was used to characterize the morphology of GNPs. Interestingly, P-123 as a new surfactant showed the best colloidal stability between our samples. Furthermore, the presence of SDS, CTAB and TX surfactants in the nanofluids caused the formation of excessive foam, while P123-GNPs showed no foam-formation after shaking within the given time. It is worthy to highlight that the rises in thermal conductivity and stability in the presence of P-123 were higher than those of other surfactants. Also, the addition of rheological property (viscosity) was found to be insignificant once loading P-123.

Characteristics of wood-silica composites influenced by the pH value of silica sols

Abstract Southern pine (Pinus spp.) sapwood samples were impregnated with silica sols with known zeta potential and particle size distribution at various pH values (3, 5, 7, 9, 11 and 13) to produce wood-silica composites (WSiCs). The morphological and chemical properties of the composites were evaluated by scanning electron microscopy-energy dispersive X-ray (SEM-EDXA) and Fourier transform infrared (FTIR) spectroscopy. The overall performance of the composites was characterized by X-ray diffraction (XRD) and thermogravimetric (TG) analysis, and dynamic wettability tests, and their dimensional stability and surface hardness were also investigated as well. The pH value of the sols had a remarkable effect on the distribution of zeta potential and colloidal particle size, and on their penetration and distribution in the wood. The composites produced at pH 5 and pH 11 show relatively better impregnability and overall properties. In the first case the compatibility with the wood pH (ca. 5) is relevant, and at these pH values are the sol’s particle sizes low. Sols with pH around 13 resulted in inferior properties, such as increased water absorption, high thermal degradation and poor dimensional stability. This could be ascribed to wood degradation under high alkaline conditions. The results were discussed in view of the colloidal particle redistribution and the interaction between silica sol and wood.

Electroosmotic flow of a two-layer fluid in a slit channel with gradually varying wall shape and zeta potential

This study aims to investigate electroosmotic (EO) flow of a two-layer fluid through a slit microchannel where the wall shape as well as zeta potential may vary slowly and periodically with axial position. The two-layer EO flow is a model for the flow of two immiscible fluids: a non-conducting working fluid being dragged into motion by a conducting sheath fluid. Electric double layers may develop in the conducting fluid near the interface between the two fluids, and near a wall that is assumed to be non-uniform in both shape and zeta potential distribution. Because of these geometrical and electrical non-uniformities, pressure is internally induced. The two-fluid flow is therefore driven by electrokinetic and hydrodynamic forcings, while subjected to the combined effects of the axial variations of the wall shape and potential distribution. The present problem is formulated by invoking the lubrication approximation, for a nearly parallel flow of low Reynolds number, and the governing equations are solved as analytically as possible. The induced pressure gradient and the deformed shape of the interface, which are functions of axial position, as well as the flow rates of the two fluids, are determined by an iterative trial-and-error numerical scheme. Results are generated to show the effects due to various factors, including the applied pressure difference, interfacial potential, viscosity ratio, wall undulation, and phase shift between the wall shape and potential distribution. Some of the effects on flow in a non-uniform channel can be qualitatively different from that in a uniform channel.

Association of Spherical Porous Nanocluster Keplerate-Type Polyoxometalate Mo72Fe30 with Biologically Active Substances

The peculiarities of formation of ionic associates of the spherical porous nanocluster polyoxometalate [Mo72Fe30O252(CH3COO)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91] ~ 150H2O with biologically active substances, in particular, thiamine chloride using the methods of UV/Vis spectroscopy, pH-metry, laser light scattering (the measurement of Zeta potential and particle size distribution), Raman spectroscopy, infrared spectroscopy and inductively coupled plasma atomic emission spectroscopy has been studied. The location of thiamine molecules on POM’s surface is given. The solubility product of associate was estimated. The formation of molecular associates of polyoxometalate with insulin, albumin has been shown. Using the meglumine acridonacetate the influence of complexing agents on the possibility of obtaining associates on the basis of [Mo72Fe30O252(CH3COO)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91] ~ 150H2O has been studied.

Increase in hydrophobicity of Bacillus subtilis spores by heat, hydrostatic pressure, and pressurized carbon dioxide treatments

The effects of heat treatment (HT), hydrostatic pressure treatment (HPT), and pressurized carbon dioxide treatment (CT) on surface hydrophobicity of B. subtilis 168 spores were investigated. The spore surface hydrophobicity was measured by determining the ratio of hydrophobic spores (RHS) that were partitioned into the n-hexadecane phase from the aqueous spore suspension. The RHS after HT generally increased in a temperature-dependent manner and reached approximately 10% at temperatures above 60°C. The effects of pressurization by HPT and accompanying temperature on increased RHS were complex. The highest RHS after HPT was approximately 17%. Following CT, RHS reached approximately 80% at 5MPa at 80°C for 30min. An increased treatment temperature enhanced RHS by CT. The increase in RHS by CT led to the formation of spore clumps and adhesion of spores to hydrophobic surfaces. Acidification of spore suspension to pH 3.2, expected pH during CT, by HCl also increased the adhesion of spores at the similar degree with CT. The spore surface zeta potential distribution was not changed by CT. Furthermore, spores with increased RHS after CT had germination-like phenomena including loss of their refractility and enhanced staining by 4',6-diamidino-2-phenylindole. Physiological germination that was induced by the addition of l-alanine also increased the RHS. From these results, it is clear that CT under heating considerably increases RHS. CT under heating considerably increases RHS. This increase in RHS may be due to acidification or germination-like phenomena during CT.

Effect of chelators on functionality of milk protein concentrates obtained by ultrafiltration at a constant pH and temperature.

Modulating conditions during ultrafiltration of skim milk appears to be a feasible strategy to obtain milk protein concentrates (MPC) with tailored functionalities. Adjustment of pH and process temperature attenuated properties of casein micelle resulting in enhanced emulsification capacity. Additional pre-treatment options such as addition of calcium chelators can further impact on the functionality of MPC by modifying the calcium distribution and casein micelle integrity. The objective of the project was to establish effects of pre-treating skim milk with calcium chelators (EDTA or citrate) in concentrations between 10 to 30 mm prior to UF on the physical properties of the feed, corresponding retentates and dried MPC, including particle size, zeta potential and calcium distribution in skim milk and the corresponding retentates, as well as the physical functionalities such as solubility, heat stability and emulsifying properties. Addition of calcium chelators (EDTA or citrate), at levels 20-30 mm concentrations reduced casein micelle size as well as total, soluble and ionic calcium contents that resulted in MPC with enhanced solubility and heat stability. The emulsion capacity was, however, improved only with EDTA at 10 mm concentration. The enhanced functionality is attributed to the reduced particle size resulting from the removal of calcium from the retentate that could modify micellar casein to an extent sufficient to cause such improvements.

Stabilising nanofluids in saline environments

Nanofluids (i.e. nanoparticles dispersed in a fluid) have tremendous potential in a broad range of applications, including pharmacy, medicine, water treatment, soil decontamination, or oil recovery and CO2 geo-sequestration. In these applications nanofluid stability plays a key role, and typically robust stability is required. However, the fluids in these applications are saline, and no stability data is available for such salt-containing fluids. We thus measured and quantified nanofluid stability for a wide range of nanofluid formulations, as a function of salinity, nanoparticle content and various additives, and we investigated how this stability can be improved. Zeta sizer and dynamic light scattering (DLS) principles were used to investigate zeta potential and particle size distribution of nanoparticle-surfactant formulations. Also scanning electron microscopy was used to examine the physicochemical aspects of the suspension.We found that the salt drastically reduced nanofluid stability (because of the screening effect on the repulsive forces between the nanoparticles), while addition of anionic surfactant improved stability. Cationic surfactants again deteriorated stability. Mechanisms for the different behaviour of the different formulations were identified and are discussed here.We thus conclude that for achieving maximum nanofluid stability, anionic surfactant should be added.

Thermo-sensitive chitosan copolymer-gold hybrid nanoparticles as a nanocarrier for delivery of erlotinib

Here, using (poly(N-isopropylacrylamide)-co-oleic acid)-g-chitosan ((PNIPAAm-co-OA)-g-CS), CS copolymer-gold hybrid nanoparticles (CGH NPs) were synthesized by autoreduction of auric cations (HAuCl4) in aqueous solution in the absence of any other reducing agent. The engineered thermo-sensitive CS copolymer with free amino groups could reduce auric cations and stabilized the resultant NPs. CGH NPs were prepared using different concentrations of CS copolymer (0.1–1% w/v) and HAuCl4 (50–500μL, 0.2% w/v). They were characterized in terms of structure, surface Plasmon band, zeta potential, atomic absorption, stability, size and size distribution. The obtained CGH NPs showed a size range of 80–100nm and high stability at different pHs with no observable agglomeration/sedimentation for couple of months. The loading efficiency of erlotinib (ETB) in the CGH NPs was about 30%. The ETB was released from the CGH NPs in a thermo-responsive manner. FACS flow cytometry analysis confirmed high cellular uptake (85.81%) of CGH NPs by A549 cells. The cytotoxicity evaluations proved the cytocompatibility and high anti-tumor effect of the engineered CGH NPs. Based on these findings, having used thermo-sensitive CS copolymer, CGH NPs were obtained in one-pot procedure, which could be considered as stimuli-responsive delivery system with potential biomedical applications.

Difficulties and flaws in performing accurate determinations of zeta potentials of metal nanoparticles in complex solutions-Four case studies.

The zeta potential (ZP) is a parameter commonly used to characterize metal nanoparticles (NPs) in solution. Such determinations are for example performed in nanotoxicology since the ZP influences e.g. the interaction between cells and different biomolecules. Four case studies on different metal NPs (Cu and Zn NPs, and citrate capped Ag NPs) are presented in this study in order to provide guidance on how to accurately interpret and report ZP data. Solutions of high ionic strength (150 mM NaCl) induce a higher extent of particle agglomeration (elucidated with Ag NPs) when compared with conditions in 10 mM NaCl, which further complicates the prediction of the ZP due to e.g. sedimentation and broadening of the zeta potential distribution. The particle size is seldom included specifically in the standard ways of determining ZP (Hückel and Smoluchowski approximations). However corrections are possible when considering approximations of the Henry function. This was seen to improve the analysis of NPs, since there are cases when both the Hückel and the Smulochowski approximations are invalid. In biomolecule-containing cell media (BEGM), the signal from e.g. proteins may interfere with the measured ZP of the NPs. The intensity distribution of the ZP of both the blank solution and the solution containing NPs should hence be presented in addition to the mean value. Due to an increased ionic strength for dissolving of metal NPs (exemplified by Zn NPs), the released metal ions must be considered when interpreting the zeta potential measurements. In this work the effect was however negligible, as the particle size was several hundred nm, conditions that made the Smoluchowski approximation valid despite an increased ionic strength. However, at low ionic strengths (mM range) and small-sized NPs (tens of nm), the effect of released metal ions can influence the choice of model for determining the zeta potential.Sonication of particle dispersions influences not only the extent of metal release but also the outermost surface oxide composition, which often results in an increased ZP. Surface compositional changes were illustrated for sonicated and non-sonicated Cu NPs. In all, it can be concluded that accurate measurements and interpretations are possible in most cases by collecting and reporting complementary data on characteristics such as particle size, ZP distributions, blank sample information, and particle oxide composition.

Abstract 5097: An industrial method of manufacturing a novel RNAi anticancer drug, DFP-10825, for the treatment of peritoneal disseminated gastric cancer

Abstract We have developed an RNAi based anticancer drug, DFP-10825 [a cationic liposome and short-hairpin RNAi molecule for thymidylate synthase (TS shRNA)] and here established an industrial method of manufacturing the formulation. The therapeutic efficacy of the DFP-10825 was examined in a MKN45 human gastric carcinoma xenograft mouse model (peritoneal disseminated gastric cancer model). The mice were received intraperitoneal injection with 5 doses of DFP-10825 or control formulation (short-hairpin RNA for luciferase) (1 mg shRNA/kg/day) once every 3 days. The treatment with DFP-10825 obviously prolonged survival time of the mice compared to control formulation and significantly suppressed the target mRNA level in the peritoneal disseminated tumors. We recently reported that DFP-10825 showed a significant therapeutic efficiency in the human malignant pleural mesothelioma orthotopic xenograft model. Accordingly, DFP-10825 may lead a clinical benefit to patients with pulmonary malignant mesothelioma or disseminated peritoneal tumor. In addition, we established an industrial method of manufacturing DFP-10825, which provides a large scale preparation. Water solution of TS shRNA was gently mixed at an optimal ratio with ethanol solution of cationic lipids, composed of DC-6-14 (a cationic lipid), DOPE and DOPC. Then, the mixture was lyophilized under optimal condition. The freeze-dried cake provided a ready for injection formulation by a one-step hydration with saline. Physicochemical properties of the obtained DFP-10825 such as particle size, zeta-potential, and size distribution were almost comparable with those of conventionally prepared DFP-10825, which prepared with conventional preparation method, mixing TS shRNA solution and cationic liposomes. Our findings in this study demonstrate that intraperitoneal chemotherapy with a simple freeze-dried RNAi medicine, DFP-10825, showing an equivalent pharmaceutical and therapeutic potency with conventionally prepared DFP-10825, meets a criteria to use for clinical settings and will have a clinical benefit to treat patients with disseminated peritoneal and pulmonary cancers. Citation Format: Tatsuhiro Ishida, Hidenori Ando, Masakazu Fukushima, Cheng-Long Huang, Hiromi Wada. An industrial method of manufacturing a novel RNAi anticancer drug, DFP-10825, for the treatment of peritoneal disseminated gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5097. doi:10.1158/1538-7445.AM2017-5097

The investigation of paper mill industry wastewater treatment and activated sludge properties in a submerged membrane bioreactor.

The paper mill industry produces high amounts of wastewater and, for this reason, stringent discharge limits are applied for sustainable reclamation and reuse of paper mill industry wastewater in many countries. Submerged membrane bioreactor (sMBR) systems can create new opportunities to eliminate dissolved substances present in paper mill wastewater including. In this study, a sMBR was operated for the treatment of paper mill industry wastewater at 35 h of hydraulic retention time (HRT) and 40 d of sludge retention time (SRT). The chemical oxygen demand (COD), NH3-N and total phosphorus (TP) removal efficiencies were found to be 98%, 92.99% and 96.36%. The results demonstrated that sMBR was a suitable treatment for the removal of organic matter and nutrients for treating paper mill wastewater except for the problem of calcium accumulation. During the experimental studies, it was noted that the inorganic fraction of the sludge increased as a result of calcium accumulation in the reactor and increased membrane fouling was observed on the membrane surface due to the calcification problem encountered. The properties of the sludge, such as extracellular polymeric substances (EPS) and soluble microbial products (SMP), relative hydrophobicity, zeta potential and floc size distribution were also monitored. According to the obtained results, the total EPS was found to be 43.93 mg/gMLSS and the average total SMP rejection by the membrane was determined as 66.2%.

Study on the Interaction Between Cellulase and Surfactants

AbstractThe conformations of secondary and tertiary structures of cellulase in the presence of eleven commonly used surfactants were determined by Raman spectroscopy and the results were discussed. The results indicated that anionic surfactants had a stronger influence on the cellulase conformations than nonionic surfactants. Thus anionic surfactants showed a stronger inactivation on the cellulase activity. Furthermore, Zeta potential distributions of cellulase in solutions of surfactants were tested by Dynamic Light Scattering (DLS). The DLS results indicated that the interaction between anionic surfactants and cellulase was attributed to electrostatic attraction. By adding cellulase to a liquid, non-cellulase-containing detergent, the detergency of the liquid detergent could be increased. Further studies on the sample swatches by optical microscopy and scanning electron microscopy (SEM) were undertaken in this paper.

Maillard reaction in natural rubber latex: Improvement of concentration process

ABSTRACTMaillard reaction in natural rubber (NR) latex was studied by treating fresh latex with formaldehyde and glutaraldehyde. Volatile fatty acid number of the treated latex could be lower than acceptable limit (< 0.08) for more than 20 days. Attenuated total reflectance infrared spectroscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the occurrence of protein crosslinks in the treated latex. NR treated with glutaraldehyde has much higher nitrogen content than NR treated with formaldehyde and untreated NR, respectively. Colloidal stability of rubber particles, represented by pH, zeta potential, viscosity, and particle size distribution information, were unchanged after treating the latex with formaldehyde. Treatment of the fresh latex with glutaraldehyde 100 and 200 mmol/kg of latex led to the aggregation of rubber particles. Interestingly, the Maillard crosslinking of proteins in fresh latex could efficiently promote the transfer of rubber particles from the serum phase into the cream phase during centrifugation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45224.

Effect of agitation on the interaction of coal and kaolinite in flotation

In this work, the interaction behavior and underlying mechanism of coal and kaolinite particles in the presence of agitation was investigated by flotation tests, homo and hetero settling tests, turbidity meter, zeta potential distribution, focused beam reflectance measurement (FBRM) and scanning electron microscope (SEM). The results show that, in the presence of kaolinite, the flotation combustible matter recovery of coal decreases from 0rpm to 1200rpm and then increases from 1200rpm to 2000rpm, indicating that the mild agitation enhances kaolinite-coating and the high intensity agitation mitigates the kaolinite-coating, which is demonstrated by the zeta potential distribution and turbidity measurements. However, the degree of the heterocoagulation between coal and kaolinite is not serious. It is found that the kaolinite particles partially cover on the coal surface by two morphologies includes individuals and aggregates through the size-based scanning electron microscope analysis. In addition, the affinity between fine kaolinite and fine coal particles is more pronounced. The kaolinite-coating enhancement caused by the mild agitation is explained by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory.

Physical Compatibility of Propofol-Sufentanil Mixtures.

Combined infusions of propofol and sufentanil preparations are frequently used in clinical practice to induce anesthesia and analgesia. However, the stability of propofol emulsions can be affected by dilution with another preparation, sometimes leading to particle coalescence and enlargement. Such unwanted effects can lead to fat embolism syndrome after intravenous application. This study describes the physical stability of 5 commercially available propofol preparations mixed with sufentanil citrate solutions. Two common markers of emulsion stability were used in this study; namely, the zeta potential and size distribution of the emulsion droplets. Both were measured using dynamic light scattering. The data for the pure propofol preparations and their mixtures with sufentanil citrate solution were compared. The absolute value of zeta potential decreased in 4 of the 5 propofol preparations after they had been mixed with sufentanil citrate. This effect indicates a lowering of repulsive interactions between the emulsion droplets. Although this phenomenon tends to cause agglomeration, none of the studied mixtures displayed a substantial increase in droplet size within 24 hours of blending. However, our long-term stability study revealed the instability of some of the propofol-sufentanil samples. Two of the 5 studied mixtures displayed a continual increase in particle size. The same 2 preparations showed the greatest reductions in the absolute value of zeta potential, thereby confirming the correlation of both measurement methods. The increase in particle size was more distinct in the samples stored at higher temperatures and with higher sufentanil concentrations. To ensure the microbial stability of an emulsion infusion preparation, clinical regulations require that such preparations should be applied to patients within 12 hours of opening. In this respect, we can confirm that during this period, none of the studied propofol-sufentanil mixtures displayed any physical instability that could lead to particle enlargement; thus, fat embolism should not be a risk after their intravenous application. However, our long-term stability study revealed differences between commercially available preparations containing the same active ingredient; some of the mixtures showed an increase in particle size and polydispersity over a longer period. Although our results should not be generalized beyond the particular propofol-sufentanil preparations and concentrations studied here, they do suggest that, as a general principle, a compatibility study should be performed for any preparation before the first intravenous application to exclude the risk of droplet aggregation.

Synthesis of Size Controlled Spherical Silica Nanoparticles via Sol-Gel Process within Hydrophilic Solvent

In this study, based on hydrolysis and condensation via Stober process of sol-gel method, synthesis of mono-dispersed silica nanoparticles was carried out with hydrophilic solvent. This operation was expected to be a more simplified process than that with organic solvent. Based on the sol-gel method, which involves simply controlling the particle size, the particle size of the synthesized silica specimens were ranged from 30 to 300 nm by controlling the composition of tetraethylorthosilicate (TEOS), DI water and ammonia solution, and by varying the stirring speeds while maintaining a fixed amount of ethanol. Increasing the content of DI water and decreasing the content of ammonia caused the particle size to decrease, while controlling the stirring speed at a high level of RPMs enabled a decrease of the particle size. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were utilized to investigate the success factors for synthesizing process; Field emission scanning electron microscopy (FE-SEM) was used to study the effects of the size and morphology of the synthesized particles. To analyze the dispersion properties, zeta potential and particle size distribution (PSD) analyses were utilized.