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Marine Biopolymers
Published in Se-Kwon Kim, Marine Biochemistry, 2023
The solubility is an interesting property in commercial chitosan. This property depends on three parameters. The pH of the solution is the parameter that links to the charge of D units in the polymer chain. The ionic strength is important and relates to the salting out effect. Finally, the existence of some ions as copper or molypdate, with strong selectivity, influence the solubility of chitosan. All chitosan is soluble in the pH below 6.5 and precipitate when the pH increases from 6.5 to 8. With the same pH, the solubility increases with FA (Vårum & Smidsrød, 2004) to alginate, the relationship between intrinsic viscosity [η] and of chitosan is linear (Anthonsen et al., 1993).
Towards the Importance of Fenugreek Proteins
Published in Dilip Ghosh, Prasad Thakurdesai, Fenugreek, 2022
Salt extraction (micellization) is another frequent approach in protein extraction from legumes. The procedure lies in the salting-in and salting-out phenomena of food proteins. Accordingly, proteins solubility increases at appropriate ionic strength (salting in). This is usually followed by protein precipitation through centrifugation or filtration. Similar to other extraction methods, the procedure could be accomplished by employment of a drying method. El-Nasri and El-Tinay (2007) used the micellization method for extraction of Sudanese fenugreek seed with 28.4% protein using 1 M NaCl and flour to solvent ratio of 1:10 for 30 min. The extraction was accomplished by further precipitation of protein at pI (4.5) and drying in open air. Final protein concentrate contained 73.9% protein. Abdel-Aal et al. (1986) applied a similar procedure, using 0.5 M NaCl and stirring for 1 h, for protein extraction from Egyptian fenugreek seeds, and produced protein isolate with 94.7% protein. The influential role of salt on protein extraction from legumes like fenugreek is possibly attributed to their high amount of globulins, salt soluble proteins. Globulins are the second major fraction of fenugreek and the most dominant one in others including soybean, peas, etc. (Feyzi et al., 2015).
Drug Nanocrystals
Published in Carla Vitorino, Andreia Jorge, Alberto Pais, Nanoparticles for Brain Drug Delivery, 2021
M. Ermelinda S. Eusébio, Ricardo A. E. Castro, Joäo Canotilho
To prevent aggregation, nanocrystallisation must be carried out in the presence of stabilisers [121]. These are adsorbed at the particle surface and stabilisation may be achieved by electrostatic repulsion among particles, by steric effects, or by a combination of both. Electrostatic stabilisers typically include ionic surfactants and polymers (e.g., sodium dodecyl sulphate [122, 123], sodium alginate [54]) [124–126]. For electrostatic stabilisation of nanocrystals, the zeta potential should be in excess of 30 mV [1]. Concerning brain delivery, some authors report that negatively charged particles should be used, as highly positively charged nanoparticles displayed toxicity to the BBB [127]. Electrostatic stabilisation is effective in aqueous media, but problems may arise when converting into dry solid forms. Moreover, stability may also be affected by changes in both pH and ionic strength. Steric stabilisation is not dependent on these effects, although it shows a greater temperature dependency [1], and may be used to prepare nanocrystals both in aqueous and non-aqueous media. For steric stabilisation, non-ionic amphiphilic surfactants or polymers are used (e.g., Tween 80, poloxamers, polyvinyl alcohol, polyvinylpyrrolidone [123–125]). Nanosuspensions may also be made more stable by combining electrostatic and steric effects in the same stabiliser molecule [118] or combining non-ionic and ionic stabilisers [128].
A mechanistic review on the dissolution phase behavior and supersaturation stabilization of amorphous solid dispersions
Published in Drug Development and Industrial Pharmacy, 2021
P. Ashwathy, Akshaya T. Anto, M. S. Sudheesh
The interaction of excipients with media components can enhance or retard the drug dissolution from ASDs. Such interaction can be identified in SS assays using biorelevant media. The apparent solubility of a drug candesartan cilexetil was found to be significantly reduced in biorelevant media due to the interaction of the excipient soluplus with lecithin [58]. Surfactants used as excipients in ASDs can form mixed micelles with media components and can also enhance or retard solubilization. Interaction of Soluplus with SDS, bile salts and phospholipids have been reported [58,59]. HPMC and PVP forms aggregate with sodium taurocholate, which is an integral part of the intestinal media [60]. The interaction is influenced by the effect of ionic strength and pH of the media. Eudragit E100 has been reported to interact with sodium taurocholate and cause precipitation [61] by ionic interaction between the anionic bile salt and cationic hydrophobic polymer [62]. Surfactants can either promote the fast release of the drug from a formulation, or it can altogether abolish the SS stabilizing effect of the polymers [63]. The addition of an anionic surfactant into the media led to a complete release of the drug whereas nonionic surfactant prevented the release of the drug [64]. There is a concentration-dependent interaction below and above the CMC of bile salt that varies with fed and fasted state and the interaction promotes drug solubilization at low bile salt concentration [60].
The relationship between the Hammett acidity and the decomposition of cefotaxime sodium in the solid state
Published in Drug Development and Industrial Pharmacy, 2020
Bashar M. Altaani, Khouloud A. Alkhamis, Shaima’a Abu Baker, Razan Haddad
Solutions containing lactose monohydrate (5% w/v) and phosphate buffer (0.05 M) were prepared. In the case of acidity measurements, thymol blue was added as an indicator and case of kinetic studies cefotaxime sodium (0.01% w/v) was added as a model drug. The ionic strength of the prepared solutions was adjusted using sodium chloride. The phosphate buffer solutions were prepared using different weight ratios of sodium phosphate tribasic and dibasic to obtain solutions with different pH values (9.81–10.68). The effect of ionic strength was also evaluated by preparing a solution (pH = 9.81) without the addition of sodium chloride; lower ionic strength. The pH of all solutions was measured using a calibrated pH meter (WTW 720 GmbH, Germany). The prepared solutions were then lyophilized using a freeze dryer (Labconco corporation, Missouri, USA) according to an established procedure that was previously described [2–3].
L445P mutation on heavy chain stabilizes IgG4 under acidic conditions
Published in mAbs, 2019
Chang-Ai Xu, Andrew Z. Feng, Charan K. Ramineni, Matthew R. Wallace, Elizabeth K. Culyba, Kevin P. Guay, Kinjal Mehta, Robert Mabry, Stephen Farrand, Jin Xu, Jianwen Feng
We also evaluated both acetate and citrate buffers at pH 3.5 for the low pH hold, and the data showed that citrate induces significantly more IgG4_CDR-X HC C-terminal fragmentation and aggregation than acetate. These results are consistent with other studies regarding the potential effects of citrate and acetate buffer on IgG aggregation.20 Citrate is a trivalent chemical containing three carboxylic acids with pKas of 3.1, 4.8, and 6.4, which results in high ionic strength. Acetate has only one carboxyl group with a pKa of about 4.8, which results in weaker ionic strength. Both citrate and acetate19 interact with proteins through their negative charge, thus the effect of their specific ion on protein stability is due to differences in ion strength. It was proposed20 that citrate ions preferentially accumulate near the surface of an antibody more than acetate ions, decreasing apparent conformational stability and increasing aggregation rates. Alternatively, accumulation of citrate ions is causing weaker electrostatic repulsions between proteins under low ionic strength environment, resulting in increased aggregation. Therefore, we promote use of acetate buffer rather than citrate in ProA purification processes.