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Approaches for Identification and Validation of Antimicrobial Compounds of Plant Origin: A Long Way from the Field to the Market
Published in Mahendra Rai, Chistiane M. Feitosa, Eco-Friendly Biobased Products Used in Microbial Diseases, 2022
Lívia Maria Batista Vilela, Carlos André dos Santos-Silva, Ricardo Salas Roldan-Filho, Pollyanna Michelle da Silva, Marx de Oliveira Lima, José Rafael da Silva Araújo, Wilson Dias de Oliveira, Suyane de Deus e Melo, Madson Allan de Luna Aragão, Thiago Henrique Napoleão, Patrícia Maria Guedes Paiva, Ana Christina Brasileiro-Vidal, Ana Maria Benko-Iseppon
In addition to determining susceptibility, the growth kinetics of the microorganism in the presence of the antimicrobial agent may also be evaluated. Microbial growth involves the multiplication and population growth of a cell culture, in addition to the increase in biomass produced by such microorganisms. Several indirect methods to measure microbial biomass are being used, based on the measurement of some metabolic activity or some specific component of the biomass (Lekha and Lonsane 1994). The evaluation of the growth rate and the generation time allows to evaluate the concentration of the cells during the incubation time and to verify the cell growth in function of possible alterations of the environmental conditions, as the presence of an antimicrobial agent. Growth must be quantified by the spectrophotometric method of turbidimetry or nephelometry. In these methods, cell growth is monitored according to the turbidity of the solution. The result obtained is expressed in terms of absorbance as a function of time. The most used wavelength for turbidimetry/nephelometry readings is found in the red region (~ 660 nm), as wavelengths in this range generate less light scattering compared to shorter wavelengths (Abdallah et al. 2014; Kogawa et al. 2021).
Glycerine Analysis
Published in Eric Jungermann, Norman O.V. Sonntag, Glycerine, 2018
Because almost all commercial glycerine is distilled, inorganic chlorides are only present because of entrainment during distillation. As with sulfate, only traces of chlorides are likely to be present in refined glycerine. Simple visual turbidimetry matching methods are normally used for specifying the upper limit of chloride in glycerine. While these methods do not give absolute amounts of chloride, they are simple to perform and sensitive. Essentially, the glycerine is diluted with water, the solution is made slightly acidic with nitric acid and silver nitrate is added to it. The presence of chlorides is indicated by precipitation of silver chloride, which will make a slightly turbid solution. The turbidity of this solution is then matched with a standard aqueous solution made from sodium chloride and silver nitrate to match the upper limit. Limits and amounts of glycerine used for the various tests are listed in Table 7.9. The American Oil Chemists Society, which often provides methods that are suitable for crude glycerine where levels of inorganics are large and of interest in determining processing conditions. AOCS method Ea2–38 uses a titration with silver nitrate. Two to five grams of sample is ashed, dissolved in water, and made acid to phenolphthalein. Potassium chromate (Mohr titration method) is added as an indicator. When all the chloride has precipitated, a reddish precipitate of silver chromate is visible. Results are reported as sodium chloride. While this method is a precise determination of chloride content as opposed to a go/no go limit test, it is not so suitable for determining very small amounts of chloride, unless larger amounts of glycerine are ashed.
Validation of suPAR turbidimetric assay on Cobas® (c502 and c702) and comparison to suPAR ELISA
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2020
Thor A. Skovsted, Eva Rabing Brix Petersen, Maj-Britt Fruekilde, Andreas Kristian Pedersen, Tomasz Pielak, Jesper Eugen-Olsen
The new assay protocol developed for the c502 and the c702 on the Cobas® instruments uses two different Cobas c pack MULTI (instrument-specific), configured with nearly identical program settings. A two-point end assay using a primary wavelength of 570 nm (and secondary wavelength of 800 nm) measured the turbidimetry according to instrument-specific assay cycle (timepoints). The assay cycle was first initiated with a sample blank measured shortly after 10 µL of plasma sample was added to 150 µL buffer (R1), and 50 µL latex particles (R2) were ultrasonically mixed. The second measuring point was carried out within 10 min and the absorbance corrected by subtracting the sample blank giving the (turbidimetric) reaction absorbance. Due to the difference in the structure of the Cobas instruments, assay cycle timepoints were defined separately. The c502 Cobas® instrument measured at assay cycle (timepoints) no. 41 and no. 68. The c702 Cobas® instrument measured at assay cycle (timepoints) no. 22 and no. 37.
Selective induction of apoptosis in MCF7 cancer-cell by targeted liposomes functionalised with mannose-6-phosphate
Published in Journal of Drug Targeting, 2018
Cristina Minnelli, Laura Cianfruglia, Emiliano Laudadio, Roberta Galeazzi, Michela Pisani, Emanuela Crucianelli, Davide Bizzaro, Tatiana Armeni, Giovanna Mobbili
Physical stability of the liposomes, containing C6Cer, was monitored in the presence of serum at 0, 4 and 24 h by measuring changes in liposome particle size distribution by DLS and monitoring the change in optical density (turbidimetry) at λ > 350 nm where light absorption is negligible for vesicles containing lipids without conjugated double bonds [35]. Liposome suspensions were mixed with supplemented FBS in PBS (50% v/v) and, at the time of analyses, they were diluted at a final concentration of 2.5 × 10−2 mM with PBS. For the turbidimetry analyses, the absorbance at 400, 500 and 600 nm was measured using a BioTek Synergy HT MicroPlate Reader Spectrophotometer. The data represent the average of at least three different analyses carried out for each sample.
High concentration formulation developability approaches and considerations
Published in mAbs, 2023
Jonathan Zarzar, Tarik Khan, Maniraj Bhagawati, Benjamin Weiche, Jasmin Sydow-Andersen, Alavattam Sreedhara
To complement these methods and cover the full size range of possible aggregates, techniques for investigation of visible and subvisible particles such as optical microscopy, light obscuration, membrane microscopy, flow imaging, conductivity-based particle counter, and fluorescence microscopy, are available.55 Additionally, laser diffraction, as well as DLS, nanoparticle tracking analysis, or turbidimetry/nephelometry can be used to assess the size of particles. Den Engelsman et al.55 have made a comprehensive comparison of these methodologies regarding their power of observations, their advantages, and disadvantages.