colloidal stability
Dotaz
Zobrazit nápovědu
Cíl: Informace o preanalytických podmínkách pro stanovení cystatinu C jsou rozporuplné a často si protiřečí. Snažili jsme se proto ověřit stabilitu cystatinu C ve vzorcích moče za různých podmínek. Metodika: Analyzováno bylo 15 vzorků ranní moče. Bezprostředně po odběru a označení byl každý vzorek rozdělen na 4 díly, přičemž vzorek 1 byl ponechán bez úpravy (bez přídavku stabilizačního činidla), vzorek 2 byl stabilizován Tencerovým činidlem, vzorek 3 byl stabilizován stabilizačním činidlem připraveným podle vlastního návrhu a vzorek 4 byl stabilizován komerčním činidlem StabilZyme Select. Každý z těchto 4 vzorků byl dále ještě rozdělen na 3 díly (A–C), které byly různým způsobem zatíženy. První byl bezprostředně zmražen při -80 °C (A), druhý byl zatížen 5 cykly zmražení a rozmražení (B) a třetí inkubován 15 dnů při laboratorní teplotě a následně zmražen při -80 °C (C). Od každého pacienta bylo tak připraveno 12 různě upravených a/nebo zatížených vzorků, ve kterých byl následně stanoven cystatin C. Výsledky: Bylo provedeno 171 měření v dubletu, průměrný variační koeficient stanovení činil 5,6 %, přičemž jeho hodnota se mezi jednotlivými testovanými skupinami (1–4, A–C) nelišila. Přestože bylo možné sledovat po několikatýdenním skladování vzorku při laboratorní teplotě pokles koncentrací cystatinu C, nebyly změny ve srovnání s koncentrací cystatinu C ve vzorku zamraženém při -80 °C statisticky významné. Také opakované zmražení a rozmražení vzorku nemělo na hodnoty cystatinu C v moči významný vliv. I když změřené rozdíly nebyly statisticky významné, lze při individuálním hodnocení pacientů usuzovat, že nejvhodnější postup pro uskladnění vzorků po jejich příjmu do laboratoře je jejich zmražení. Závěr: Bezprostřední zmražení vzorku moče určeného pro analýzu cystatinu C při teplotě -80 °C bez přidání stabilizačního činidla lze považovat za dostatečné preanalytické opatření. Použití Tencerova nebo jiného stabilizačního koktejlu nepřineslo žádné podstatné výhody.
Objective: Information about pre-analytical preparation for urine cystatin C measurement is often contradictory; verification of cystatin C stability in urine samples. Methods: Each urine sample collected from 15 individuals was divided into 4 parts and 3 parts were treated with various stabilizers: 1-sample without stabilizer; 2-sample stabilized with Tencer reagent; 3-sample stabilized with reagent according to our own design (thimerosal-anitimicrobial agent; benzamidin-serine proteases inhibitor; aminocapronic acid-lysine proteases inhibitor, citrate buffer-modulator of pH value; BSA-suppressor of non-specific adsorption and protective colloid effect); 4-sample stabilized with StabilZyme Select. All parts were further divided into 3 aliquots and frozen at -80 °C, or treated by 5 cycles of freezing and thawing, or incubated at room temperature for 15 days. Cystatin C was subsequently determined in all samples. Results: We did not observe any significant change in samples after 5 cycles of freezing and thawing, or incubation at room temperature in samples without as well with stabilizing agent. However, storage at room temperature led to a nonsignificant reduction in cystatin C level by 13% in samples without stabiliser, by 18% with Tencer stabilizer, by 13% with our own designed stabilizer, and by 3% with StabilZyme. Conclusion: Urine samples may be frozen at -80 °C without lost of cystatin C level in that kind of sample and it may be a convenient pre-analytical precaution. Application of Tencer or other tested stabilizers does not significantly improve sample handling.
A method for the stabilization of nanoscale zero valent iron (nZVI) particles using silica was developed. Stabilization can significantly improve the performance characteristics of currently available nZVI products containing agglomerated particles. In the first step of the method, the agglomerates were broken using a sonication. A subsequent stabilizing effect was brought about by the deposition of silica onto the surface of the nZVI particles. The method was tested on three commercially available nZVI suspensions which formed agglomerates with mean sizes ranging from 1000 to 5000 nm. The application of the method resulted in a significant reduction of the mean size of the agglomerates to the values from 100 to 200 nm. The stabilizing effect of silica was also evidenced using scanning electron microscopy, zeta potential measurements and sedimentation analysis. The introduction of typical groundwater ions did not significantly affect the colloidal stability of the treated nZVI suspensions. The results of this study indicate that the silica coating have the potential to protect nZVI against agglomeration.
In pharmaceutical industry, the use of lubricants is mostly based on historical experiences or trial and error methods even these days. It may be demanding in terms of the material consumption and may result in sub-optimal drug composition. Powder rheology enables more accurate monitoring of the flow properties and because the measurements need only a small sample it is perfectly suitable for the rare or expensive substances. In this work, rheological properties of four common excipients (pregelatinized maize starch, microcrystalline cellulose, croscarmellose sodium and magnesium stearate) were studied by the FT4 Powder Rheometer, which was used for measuring the compressibility index by a piston and flow properties of the powders by a rotational shear cell. After an initial set of measurements, two excipients (pregelatinized maize starch and microcrystalline cellulose) were chosen and mixed, in varying amounts, with anhydrous colloidal silicon dioxide (Aerosil 200) used as a glidant. The bulk (conditioned and compressed densities, compressibility index), dynamic (basic flowability energy) and shear (friction coefficient, flow factor) properties were determined to find an optimum ratio of the glidant. Simultaneously, the particle size data were obtained using a low-angle laser light scattering (LALLS) system and scanning electron microscopy was performed in order to examine the relationship between the rheological properties and the inner structure of the materials. The optimum of flowability for the mixture composition was found, to correspond to empirical findings known from general literature. In addition the mechanism of colloidal silicone dioxide action to improve flowability was suggested and the hypothesis was confirmed by independent test. New findings represent a progress towards future application of determining the optimum concentration of glidant from the basic characteristics of the powder in the pharmaceutical research and development.
This paper reports on the formation of silver nanoparticles initiated by gamma and UV radiation in various aqueous solutions. Inorganic precursors were used for radiation and/or photochemical reduction of Ag(+) ions to a metallic form. The influence of various parameters on the nucleation and formation of colloid particles was studied. Attention was also focused on the composition of the irradiated solution. Aliphatic alcohols were used as scavengers of OH radicals and other oxidizing species. The influence of the stabilizers on the formation and stability of the nanoparticles was studied.
The mechanism of colloidal silica action to improve flow properties of pharmaceutical powders is known to be based on inter-particle force disruption by silica particles adhered to the particle surface. In the present article, the kinetic aspects of this action are investigated, focusing on non-spherical particles of different size. Blends comprising microcrystalline cellulose or calcium hydrogen phosphate dihydrate and colloidal silica were examined using powder rheometer. The blends were formulated to represent effects of particle size, surface texture, colloidal silica loading, and mixing time. Pre-conditioning, shear testing, compressibility, and flow energy measurements were used to monitor flow properties. Components and blends were analyzed using particle size analysis and scanning electron microscopy (SEM), using energy dispersive spectroscopy (EDS) and back-scattered electron (BSE) detection to determine surface particle arrangement. All studied parameters were found to have substantial effects on flow properties of powder blends. Those effects were explained by identifying key steps of colloidal silica action, which were found to proceed at substantially different rates, causing the flow properties change over time being dependent on the blend formulation and the component properties.
- MeSH
- časové faktory MeSH
- celulosa chemie MeSH
- farmaceutická chemie metody MeSH
- fosforečnany vápenaté chemie MeSH
- koloidy chemie MeSH
- mikroskopie elektronová rastrovací MeSH
- oxid křemičitý chemie MeSH
- pomocné látky chemie MeSH
- prášky, zásypy, pudry MeSH
- příprava léků metody MeSH
- reologie MeSH
- spektrometrie rentgenová emisní MeSH
- velikost částic MeSH
- Publikační typ
- časopisecké články MeSH
Conducting polyaniline can be prepared and modified using several procedures, all of which can significantly influence its applicability in different fields of biomedicine or biotechnology. The modifications of surface properties are crucial with respect to the possible applications of this polymer in tissue engineering or as biosensors. Innovative technique for preparing polyaniline films via in-situ polymerization in colloidal dispersion mode using four stabilizers (poly-N-vinylpyrrolidone; sodium dodecylsulfate; Tween 20 and Pluronic F108) was developed. The surface energy, conductivity, spectroscopic features, and cell compatibility of thin polyaniline films were determined using contact-angle measurement, the van der Pauw method, Fourier-transform infrared spectroscopy, and assay conducted on mouse fibroblasts, respectively. The stabilizers significantly influenced not only the surface and electrical properties of the films but also their cell compatibility. Sodium dodecylsulfate seems preferentially to combine both the high conductivity and good cell compatibility. Moreover, the films with sodium dodecylsulfate were non-irritant for skin, which was confirmed by their in-vitro exposure to the 3D-reconstructed human tissue model.
- MeSH
- aniliny škodlivé účinky chemie MeSH
- fibroblasty účinky léků MeSH
- koloidy škodlivé účinky chemie MeSH
- membrány umělé * MeSH
- myši MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- viabilita buněk účinky léků MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
A category of naked maghemite nanoparticles (γ-Fe2O3), named surface active maghemite nanoparticles (SAMNs), is characterized by biological safety, high water colloidal stability and a surface chemistry permitting the binding of ligands. In the present study, the interaction between SAMNs and an antibiotic displaying chelating properties (oxytetracycline, OxyTC) was extensively structurally and magnetically characterized. OxyTC emerged as an ideal probe for providing insights into the colloidal properties of SAMNs. At the same time, SAMNs turned out as an elective tool for water remediation from OxyTC. Therefore, a dilute colloidal suspension of SAMNs was used for the removal of OxyTC in large volume tanks where, to simulate a real in situ application, a population of zebrafish (Danio rerio) was introduced. Interestingly, SAMNs led to the complete removal of the drug without any sign of toxicity for the animal model. Moreover, OxyTC immobilized on SAMNs surface resulted safe for sensitive Escherichia coli bacteria strain. Thus, SAMNs were able to recover the drug and to suppress its antibiotic activity envisaging their feasibility as competitive option for water remediation from OxyTC in more nature related scenarios. The present contribution stimulates the use of novel smart colloidal materials to cope with complex environmental issues.
- MeSH
- antibakteriální látky chemie farmakologie MeSH
- dánio pruhované MeSH
- Escherichia coli účinky léků MeSH
- koloidy chemie MeSH
- magnetické nanočástice chemie MeSH
- mikrobiální testy citlivosti MeSH
- oxytetracyklin chemie farmakologie MeSH
- povrchové vlastnosti MeSH
- suspenze chemie MeSH
- velikost částic MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Purpose: Plasmonic photothermal cancer therapy by gold nanorods (GNRs) emerges as a promising tool for cancer treatment. The goal of this study was to design cationic oligoethylene glycol (OEG) compounds varying in hydrophobicity and molecular electrostatic potential as ligand shells of GNRs. Three series of ligands with different length of OEG chain (ethylene glycol units = 3, 4, 5) and variants of quaternary ammonium salts (QAS) as terminal functional group were synthesized and compared to a prototypical quaternary ammonium ligand with alkyl chain - (16-mercaptohexadecyl)trimethylammonium bromide (MTAB). Methods: Step-by-step research approach starting with the preparation of compounds characterized by NMR and HRMS spectra, GNRs ligand exchange evaluation through characterization of cytotoxicity and GNRs cellular uptake was used. A method quantifying the reshaping of GNRs was applied to determine the effect of ligand structure on the heat transport from GNRs under fs-laser irradiation. Results: Fourteen out of 18 synthesized OEG compounds successfully stabilized GNRs in the water. The colloidal stability of prepared GNRs in the cell culture medium decreased with the number of OEG units. In contrast, the cellular uptake of OEG+GNRs by HeLa cells increased with the length of OEG chain while the structure of the QAS group showed a minor role. Compared to MTAB, more hydrophilic OEG compounds exhibited nearly two order of magnitude lower cytotoxicity in free state and provided efficient cellular uptake of GNRs close to the level of MTAB. Regarding photothermal properties, OEG compounds evoked the photothermal reshaping of GNRs at lower peak fluence (14.8 mJ/cm2) of femtosecond laser irradiation than the alkanethiol MTAB. Conclusion: OEG+GNRs appear to be optimal for clinical applications with systemic administration of NPs not-requiring irradiation at high laser intensity such as drug delivery and photothermal therapy inducing apoptosis.
- MeSH
- biologický transport MeSH
- HeLa buňky MeSH
- hydrofobní a hydrofilní interakce MeSH
- koloidy MeSH
- kvartérní amoniové sloučeniny chemie MeSH
- lidé MeSH
- ligandy MeSH
- nanotrubičky chemie MeSH
- polyethylenglykoly chemie MeSH
- stabilita léku MeSH
- teplota * MeSH
- zlato chemie metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Gold nanoparticles represent nanosized colloidal entities with high relevance for both basic and applied research. When gold nanoparticles are functionalized with polymer-molecule ligands, hybrid nanoparticles emerge whose interactions with the environment are controlled by the polymer coating layer: Colloidal stability and structure formation on the single particle level as well as at the supracolloidal scale can be enabled and engineered by tailoring the composition and architecture of this polymer coating. These possibilities in controlling structure formation may lead to synergistic and/or emergent functional properties of such hybrid colloidal systems. Eventually, the responsivity of the polymer coating to external triggers also enables the formation of hybrid supracolloidal systems with specific dynamic properties. This review provides an overview of fundamentals and recent developments in this vibrant domain of materials science.
BACKGROUND: Conversely to common coated iron oxide nanoparticles, novel naked surface active maghemite nanoparticles (SAMNs) can covalently bind DNA. Plasmid (pDNA) harboring the coding gene for GFP was directly chemisorbed onto SAMNs, leading to a novel DNA nanovector (SAMN@pDNA). The spontaneous internalization of SAMN@pDNA into cells was compared with an extensively studied fluorescent SAMN derivative (SAMN@RITC). Moreover, the transfection efficiency of SAMN@pDNA was evaluated and explained by computational model. METHODS: SAMN@pDNA was prepared and characterized by spectroscopic and computational methods, and molecular dynamic simulation. The size and hydrodynamic properties of SAMN@pDNA and SAMN@RITC were studied by electron transmission microscopy, light scattering and zeta-potential. The two nanomaterials were tested by confocal scanning microscopy on equine peripheral blood-derived mesenchymal stem cells (ePB-MSCs) and GFP expression by SAMN@pDNA was determined. RESULTS: Nanomaterials characterized by similar hydrodynamic properties were successfully internalized and stored into mesenchymal stem cells. Transfection by SAMN@pDNA occurred and GFP expression was higher than lipofectamine procedure, even in the absence of an external magnetic field. A computational model clarified that transfection efficiency can be ascribed to DNA availability inside cells. CONCLUSIONS: Direct covalent binding of DNA on naked magnetic nanoparticles led to an extremely robust gene delivery tool. Hydrodynamic and chemical-physical properties of SAMN@pDNA were responsible of the successful uptake by cells and of the efficiency of GFP gene transfection. GENERAL SIGNIFICANCE: SAMNs are characterized by colloidal stability, excellent cell uptake, persistence in the host cells, low toxicity and are proposed as novel intelligent DNA nanovectors for efficient cell transfection.
- MeSH
- biofyzikální jevy MeSH
- DNA chemie genetika MeSH
- genetické vektory MeSH
- koloidy chemie MeSH
- lidé MeSH
- nanočástice chemie ultrastruktura MeSH
- plazmidy chemie genetika MeSH
- technika přenosu genů * MeSH
- transfekce metody MeSH
- transmisní elektronová mikroskopie MeSH
- velikost částic MeSH
- železité sloučeniny chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
