Supercritical Fluid Extraction as a Sample Preparation Tool in Analytical Toxicology
Steven H. Y. Wong, Iraving Sunshine in Handbook of Analytical Therapeutic Drug Monitoring and Toxicology, 2017
An example63 of the use of Hydromatrix as a dispersing agent is shown in Figure 5–4. A 1-g chicken muscle sample is displayed in the left petri dish. The middle dish contains 2 g of unmodified Hydromatrix, which was subsequently blended with the chicken muscle sample. The resultant mixture is displayed in the right dish. Note that the water in the tissue sample has been adsorbed by the Hydromatrix, leaving a free-flowing powder. This adsorbed water can be subsequently solubilized by SF-CO1 during the extraction process. Water can act as a co-solvent for many analytes, and its presence in the SF may be necessary for the success of the extraction (see “Applications of SFE in Analytical Toxicology”). The powdered mixture can be easily poured into an extraction vessel of the type shown at the top of the photograph. Because of the large volume of the tissue/Hydromatrix mixture, a 26-ml extraction vessel was necessary to accommodate this material. Before sealing the extraction vessel, the tissue/Hydromatrix mixture must be tightly compressed with a tamping rod to ensure uniform SF penetration of the sample matrix during SFE.
Liquid Crystals as Drug Delivery Systems for Skin Applications
Andreia Ascenso, Sandra Simões, Helena Ribeiro in Carrier-Mediated Dermal Delivery, 2017
Cubosomes and hexosomes can be prepared via several fragmentation methods of liquid crystalline systems. Some methods involve high-energy input to fragment the systems. Specifically, a mixture of the structure-forming lipid and stabilizers is hydrated to self-assemble in a viscous bulk phase. The bulk is then dispersed upon the input of high-level energy (high- pressure homogenization, ultrasonication) to form cubosomes or hexosomes [2,9]. Other methods of preparation include the reconstitution of dispersions from dried lipid/stabilizer films and precipitation upon diluting lipids in the presence of solutions containing an aqueous phase or upon dialyzing a mixed micellar solution to form nanostructured systems [9]. Cubosomes or hexosomes can be formed by the controlled addition of aqueous medium, which rapidly reduces the lipid solubility and results in particle formation [2]. Most systems require a dispersing agent or stabilizers (bile salts, amphiphilic proteins or block copolymers) because these nanostructured particles tend to aggregate [9]. The properties of these nanoparticles (such as their size, structure and stability) can be affected by their internal composition, dispersion polymer concentration and processing conditions [11].
Assay of Antibiotics in Mammalian Cell Culture
Adorjan Aszalos in Modern Analysis of Antibiotics, 2020
Culture Medium and Solutions: Balanced salt solution: Use a solution compatible with the growth medium and without bicarbonate for washing cells.Complete growth medium: Use a medium providing a maximum growth rate with 5—10% calf or horse serum.Dispersing agent: Select the agent best suited for the cell line utilized.
Role of gold and silver nanoparticles in cancer nano-medicine
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Heerak Chugh, Damini Sood, Ishita Chandra, Vartika Tomar, Gagan Dhawan, Ramesh Chandra
The stability of NPs in the solution is attributed to the adsorption of a dispersant layer around each particle in the solution. The thickness of the layer influences the stability of the NPs. A dispersant layer of appropriate thickness would result in stable particles as it would be able to successfully overcome the attractive forces among individual particles due to flow of excluded solvent between the two adsorbed layers on adjacent particles whereas a thin layer would fail to do so which results in agglomeration or aggregation of particles [64]. Generally, there are two approaches to stabilize a metallic NP formulation: steric and electrostatic stabilization. As the name suggests, electrostatic stabilization is based on same charges on the surface of the particles which causes repulsion and prevents aggregation. Steric repulsion also referred to as polymeric stabilization uses mostly polymers as capping agents which when adsorbed on the surface of the particles inhibit the particles to reach the minimum distance for the Van der Waals forces to act [56,65]. A few examples of stabilizers are N,N-dimethylformamide (DMF) [66], (4–(3-phenylpropyl)pyridine) [67] and PVA (poly(vinyl alcohol)) and PVP (polyIJvinylpyrrolidone) [55].
Investigating the toxic effects induced by iron oxide nanoparticles on neuroblastoma cell line: an integrative study combining cytotoxic, genotoxic and proteomic tools
Published in Nanotoxicology, 2019
Dalel Askri, Valérie Cunin, David Béal, Sylvie Berthier, Benoit Chovelon, Josiane Arnaud, Walid Rachidi, Mohsen Sakly, Salem Amara, Michel Sève, Sylvia G. Lehmann
To investigate how neuroblastoma cell line deals with IONPs and FeCl3, we performed a cytotoxic and genotoxic study completed by a proteomic study. When taken together, our results produce a large view of the cellular response to iron and IONPs. The IONPs used in our study showed increased size in suspension than in powder. Costa et al. in 2016 evaluated IONPs coated to silica (100 nm) or oleic acid (10.9 nm) cytotoxicity on SH-SY5Y neuroblastoma cell line and A172 glioblastoma cell line (Costa et al. 2016). The team reported that IONPs dispersed in cell culture media showed a larger size and lower stability than those dispersed in water which in concordance with our findings. This increase in size has been shown in other studies, and it is mainly due to the formation of agglomerates at physiological pH and electrolyte concentration (Bihari et al. 2008). In water, the NPs have also a much larger diameter by DLS than the one determined by the TEM (as powder NPs), indicating that these particles are not particularly stable. In our study, the results obtained by comparing the DLS measurements with or without serum revealed the importance of serum presence to prevent high nanoparticle agglomeration. Various investigations have shown the importance of serum as a dispersant product to improve particle dispersion and stability. However, they reported, simultaneously, that serum is responsible for size increase by forming corona proteins around particles, which prevents the NPs from agglomerating by providing steric hindrance (Wiogo et al. 2011).
Introducing a new standardized nanomaterial environmental toxicity screening testing procedure, ISO/TS 20787: aquatic toxicity assessment of manufactured nanomaterials in saltwater Lakes using Artemia sp. nauplii
Published in Toxicology Mechanisms and Methods, 2019
Seyed Ali Johari, Kirsten Rasmussen, Mary Gulumian, Mahmoud Ghazi-Khansari, Norihisa Tetarazako, Shosaku Kashiwada, Saba Asghari, June-Woo Park, Il Je Yu
The test container volume should be at least 5 ml per 5 animals per concentration group and control. The test can be conducted using semi-static (renewal) test medium when the test nanomaterial concentration is not stable. As already noted, an additional control containing the dispersant should be prepared when using dispersant reagents for the dispersion. At least five nauplii should be exposed to each test concentration for 48 h. At least five test concentrations should be used, arranged in a geometric series with a separation factor not exceeding ‘2.2’, and if less than five concentrations are used a justification should be provided. The highest concentration tested should result in 100% immobilization, while the lowest concentration tested should cause no observable effect. The water temperature should range between 25 °C and 28 °C and be constant for each test within ±1 °C. A 16 h light and 8 h dark cycle is recommended. The nauplii should not be fed during the test period (48 h). In addition, the number of immobilized nauplii should be counted at 24 h and 48 h from the start of the test.