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Gas Chromatography
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
Obviously, high loadings of stationary phase will help solve the problem of absorption on the support, but such high loadings may not be desirable for the required chromatography. It is therefore more usual to inactivate the support itself, prior to coating with stationary phase, by silylating with hexamethyldisilazane or similar reagent. The glass column itself should be similarly treated.
Biotechnology
Published in Massimo Maffei, Vetiveria, 2002
Marco Mucciarelli, Ruth E. Leupin
Callus suspension cultures were established by transferring 6 g (fresh weight) callus in 80 ml of MS medium containing 2% sucrose (w/v) and modified according to Mucciarelli et al. (1993). Suspension cultures were maintained on a gyratory shaker at 25 rpm for 30 days. Amberlite XAD-4, tried as a growth elicitor, has been tested in activated and non-activated form and added sterile at 2% (w/v) in liquid cultures (Camusso et al., 1999; Camusso et al., in preparation). Glucidic compositions of cell culture and suspension media were determined by fractionating extraction and enzymatic hydrolysis and analysis by GC-MS, after resuspension in pyridine and derivatization by 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS).
Small Molecules: Process Intensification and Continuous Synthesis
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
The team focused on a metrics driven approach using cost, unit operations, and PMI (Equation 7.4) as indicators of success in their process intensification efforts. The original process relied on the coupling of the pyridine-carboxylic acid 21 with CAPIC (22), to afford amide 23. The cyclopropylamino moiety was introduced to afford CYCLOR (26) and, subsequently, cyclization produced neveripine (20). Overall, the original process demonstrated good efficiency with a 58% overall yield, 15 unit operations, and a PMI of 67. The improved approach relied on a transamination of the 2-cyclopropylamino pyridine (MeCAN, 25) with the 3-amino pyridine (CAPIC, 22). The Gupton-McQuade group initially embarked on new syntheses of both of these materials in order to reduce costs. MeCAN (25) was synthesized in an overall yield of 86% and a PMI of 12 by a series of four transformations with only one isolated intermediate, beginning from 2-chloro-3-cyano-pyridine. More importantly, CAPIC (22), a 1,2,3 trisubstituted pyridine, was derived from the commodity chemicals acetone and malononitrie. The trisubstituted pyridine core was built up from these materials, using a dimethyl formamide equivalent, followed by cyclization to complete the pyridine ring preparation. Subsequently, several high-yielding transformations produced the desired CAPIC intermediate in an excellent 80% overall yield with a PMI of 18. To affect the transamination of 25 and 22, both lithium hexamethyldisilazide (LiHMDS) and NaH were successful, with the latter being selected due to its atom economy. In the reaction, approximately two equivalents of NaH in diglyme at 65°C were used to produce the initial amide product CYCLOR (26), which was not isolated, but treated with another two equivalents of NaH in diglyme at 115 to produce nevirapine (20) in a single pot process. The authors were also able to demonstrate the conversion of this batch route into a continuous process. In the first step, CAPIC (22) was deprotonated with NaH with facilitation from a spinning disk reactor and transferred to a holding tank containing MeCAN (25), which was allowed to react to produced CYCLOR (26). This reaction is of particular note because it demonstrates the ability of the spinning disk reactor to process slurries such as NaH, without which this example of continuous chemistry may not have been achieved. The final cyclization to nevirapine was achieved by passing CYCLOR through a mixed packed bed of glass beads and NaH at 165°C. Overall, the modified process achieved a yield of 91%, four unit operations, and a PMI of 11, demonstrating the benefits of the Gupton-McQuade approach.
Hemostatic Comparison of a Polysaccharide Powder and a Gelatin Powder
Published in Journal of Investigative Surgery, 2019
Rahul K. Singh, Bernhard Baumgartner, Jason R. Mantei, Rhea N. Parreno, Paul J. Sanders, Kevin M. Lewis, John J. Barry
Liver lesions treated with MPH and BGP were excised and immersed in a fixative solution consisting of 2% glutaraldehyde in 0.1 M cacodylate buffer. Explants were sectioned to approximately 5 mm in thickness and glued to platforms using Loctite 404 tissue adhesive. After approximately 10-minutes of curing in a humid environment, these glued tissue sections were further sectioned to a thickness of 500 µm by a Vibratome 3000. These slices were washed three times with 0.1 M cacodylate buffer and processed through serial dehydrations of ethanol in water up to pure ethanol. This was followed by immersion in mixtures of hexamethyldisilazane (HMDS) and ethanol up to pure HMDS. The resulting dehydrated samples were air dried. Dry tissue slices were mounted and coated with Iridium metal. An FEI Quanta 650 FEG SEM was used to examine the samples.
The purification and functional study of new compounds produced by Escherichia coli that influence the growth of sulfate reducing bacteria
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Oluwafemi Adebayo Oyewole, Julian Mitchell, Sarah Thresh, Vitaly Zinkevich
The effect of SGI and SGE on the morphology of SRB cells and biofilm formation was investigated using an SEM, JEOL 6060LV. Glass coupon (7 x 10 mm) was placed inside 9 mL of VMR medium in a 10 mL vial. The medium was de-oxygenated using nitrogen gas for 30 min and sterilized by autoclaving for 15 min. An aliquot of the 7 days old culture of D. indonesiensis was added into the medium using 1:10 (v/v) ratio and SGI was added into the medium at 1:20 (v/v) ratio. The culture was incubated at 37°C for 1, 4 and 7 days. All the above procedures were carried out using aseptic technique. Two controls were set up one with SGI only and another comprising a culture of D. indonesiensis only. This procedure was repeated for SGE. Glass coupons containing biofilms were fixed with Gluteraldehyde (4 %) in phosphate buffer (0.1 M) overnight at 20 (±2)°C and rinsed in phosphate buffer (0.1 M) twice at 10-min interval. The glass coupons were then fixed with 3 drops of osmium tetroxide (1 %) in sodium cacodylate buffer (0.1 M) at 20 (±2)°C for 1 h and mixed gently using B7925 rotator to ensure uniform distribution of the solvent. The coupons were rinsed twice in 0.1 M phosphate buffer at 10-min interval. This was followed by 10 min sequential exposures to 30, 50, 70, 90 % (v/v) aqueous solutions of absolute ethanol (reagent grade) and final immersion for 10 min in 100 % acetone (reagent grade). Following dehydration, two drops of hexamethyldisilazane were placed on each coupon to cover the slides and the specimens were incubated overnight at 20 (±2)°C. The glass coupons were placed on aluminum stubs and sputter-coated with gold using Q150 R ES for 5 min. The Au-coated specimens were viewed at 15 kV accelerating voltage value.
Characterization and in vivo study of decellularized aortic scaffolds using closed sonication system
Published in Organogenesis, 2019
Aqilah Hazwani, Munirah Sha’Ban, Azran Azhim
To characterize the ultrastructure of the ECM surface and fibre networks of aortic scaffolds, SEM images were used. The tissue samples were fixed with McDowell-Trump fixative at 4ᵒC for 24 hours. Samples were then dehydrated with a series of increasing concentrations of ethanol (50% to 100%). Dehydrated samples were immersed in Hexamethyldisilazane (HMDS) solution for 10 minutes and leave in a desiccator to air-dry at room temperature. Next, dried samples were mounted on SEM stub of metal and coated with Gold/Palladium using Sputter Coater (Leica Biosystem, US) for 60 seconds and visualized by using Scanning electron microscope (Carl Zeiss, Germany) with 5000x magnification.