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Nanoparticles — Preparation and Applications
Published in Max Donbrow, Microcapsules and Nanoparticles in Medicine and Pharmacy, 2020
The desolvation of gelatin can be achieved with ethanol or sodium sulfate.70,71 The choice of the desolvating agent depends mainly on the drug to be attached to the nanoparticle. Ethanol has the advantage that it is easily removable during lyophilization. In some cases a surfactant, polysorbate 20 or polysorbate 80, must be present in order to solubilize certain drugs. The surfactants also facilitate the redispersion of the final freeze-dried products. After desolvation, monitored by turbidity measurements as described above, the addition of a small amount of a resolvating agent yields optimal products: at the endpoint of the turbidity monitored titration, i.e., the point before the nephelometer readings increase significantly, optimal conditions for nanoparticle formation are already exceeded. Hardening of this system would cause aggregation and flocculation of the particles because the interparticulate cross-linking by the aldehyde takes place. This problem can be avoided by the above mentioned addition of a small amount of resolvating agent before hardening. Glutaraldehyde proved to be the hardening agent of choice because it is a bifunctional aldehyde.70 Excessive aldehyde has to be removed with sodium sulfite or sodium metabisulfite so that further hardening or aggregation of gelatin nanoparticles does not occur. The crude product can then be freeze-dried.
Melt Extruded Amorphous Solid Dispersions
Published in Isaac Ghebre-Sellassie, Charles Martin, Feng Zhang, James DiNunzio, Pharmaceutical Extrusion Technology, 2018
Pinak Khatri, Dipen Desai, Harpreet Sandhu, Atsawin Thongsukmak, Gaurang Patel, Jaydeep Vaghashiya, Wantanee Phuapradit, Navnit Shah
Surfactants are most commonly used as solubilizers or emulsifying agents to increase the apparent aqueous solubility and bioavailability of the drug. In the case of hot-melt extrusion, surfactants can also have a plasticizing effect, which allows processing at lower temperatures. Some of the commonly used surfactants include polysorbate 20, polysorbate 80, vitamin E polyethylene glycol succinate, polyoxyl 40 hydrogenated castor oil, etc. (Padden et al., 2011). Ghebremeskel et al. (2007) demonstrated the effect of Tween 80 and docusate sodium on the physical stability of API-PVP solid dispersions. They concluded that the two surfactants evaluated on API-PVP dispersions were very similar in their plasticization, water uptake, and consequently their physical stability. It was suggested that the surfactant's ability to lower the viscosity of the melt and increase the API solubility and homogeneity in the carrier polymer might be the reason for such observations. Since, the plasticizers lower the Tg as well as absorb water, it is possible that physical stability of the system can decrease; however, this study showed that this effect was minimal (Ghebremeskel et al., 2007).
Chemistry, food and the modern diet: what’s in food besides food?
Published in Richard J. Sundberg, The Chemical Century, 2017
Polysorbate (20, 40, 60, 80) are fatty acid monoesters of sorbitan, a sugar alcohol derived from glucose by reduction and cyclization. The monoesters can be further modified by reaction with ethylene oxide to introduce about 20 PEG on free alcohol sites, similarly to the related PEG surfactants. The number indicates the fatty acid that is used, 20 for lauric, 40 for palmitic, 60 for stearic, and 80 for oleic acid. These materials are used as emulsifiers. Brand names associated with polysorbates include, Emsorb, Liposorb, Sorlate, and Tween.
Cloud point analysis: Influence of additives on polysorbate
Published in Journal of Dispersion Science and Technology, 2018
In the literature the names polysorbate and tween are used interchangeably. While raising the temperature of nonionic surfactants, the system becomes cloudy and phase separates out at a certain value. This temperature is known as the cloud point (CP).[1,2] In general, nonionic surfactants show optimal effectiveness when they are used near/below their CP. These nonionic surfactant solutions can be strongly influenced by any type of additives present in it.[3] Many research groups have studied the effect of additives on the CP of nonionic surfactants. Mahajan et al.[3] studied the effect of glycol oligomers and triblock polymers on the clouding behaviour of tweens. It is very essential to determine the additive effect on the CP of a nonionic surfactant.[4] Recently, we had studied the clouding behaviour of mixed block-copolymers in the presence of different salts.[2] More research on the combination of nonionic surfactant with additives is required to reveal vital information. This article reports the CP measurements of polysorbates 20 and 80 in the presence of salt additives. The polysorbates are amphipathic, nonionic surfactants composed of fatty acid esters of polyoxyethylene sorbitan, being polyoxyethylene sorbitan monolaurate for polysorbate 20 (tween-20) and polyoxyethylene sorbitan monooleate for polysorbate 80 (tween-80). The chemical structures of polysorbates 20 and 80 are shown in Figure 1 [where w + x + y + z refers to the total number of oxyethylene subunits on each surfactant molecule and may not exceed 20].