Oil-in-Water Nanosized Emulsions for Drug Delivery and Targeting. Tamilvanan Shunmugaperumal. Читать онлайн. Newlib. NEWLIB.NET

Автор: Tamilvanan Shunmugaperumal
Издательство: John Wiley & Sons Limited
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Жанр произведения: Химия
Год издания: 0
isbn: 9781119585251
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and Müller 2010). Another elegant way proposed by Butler and Dressman (2010) to classify the API molecules is the Developability Classification System (DCS) as this way of categorizing the API molecules is in a more biorelevant manner. According to the DCS, the API molecules can further be sub‐categorized into two types to distinguish between dissolution rate‐limited (DCS Class IIa) and solubility‐limited (DCS Class IIb) API molecules (as shown in Flowchart 1.1). More importantly, the intrinsic solubility and the related intraluminal API concentration for API molecules belonging to Class IIb and IV are too low to achieve sufficient flux over the epithelial membrane. Therefore, the API molecules belonging to DCS Class IIb and IV often utilize the complexation or other formulation approaches based on solid‐state modifications and even these approaches might be preferable compared with nanocrystals or nanosuspensions (Chen et al. 2017; Möschwitzer 2013; Shah et al. 2016).

      An emulsion is a biphasic liquid preparation consisting of two immiscible liquids, one of which (the dispersed phase) is finely and uniformly dispersed as globules throughout the second phase (the continuous phase) (Barkat et al. 2011). If the amount of oil phase is significantly low when compared to the amount of water phase, then, the final emulsion is termed as oil‐in‐water (o/w) emulsion. Conversely, when the amount of water phase is significantly lower than the oil phase, the resulting emulsion system appears to be somewhat more viscous and is called as water‐in‐oil (w/o) emulsion. Both o/w and w/o type of emulsion systems are stabilized against the aggregation, coalescence and separation of dispersed oil or water phase by the addition of a third component called as emulsifying agent or emulgent or emulgator. In fact, the therapeutic emulsions are being stabilized by the addition of more than one emulgent molecules in order to prevent random collision of‐and then the coalescence of‐dispersed oil or water phase of the o/w or w/o emulsion. Mixing of appropriate amounts of oil, water and emulgent leads to the formation of an emulsion and this whole process is being named as emulsification. Apart from the amount of dispersed oil or water phase which will determine the type of final emulsion formed (whether o/w or w/o), the amount of single or multiple emulgent molecule added during the emulsification process will obviously control the type of emulsion produced. In addition, the size‐reduction equipments such as high‐energy or low‐energy homogenizer used to mix the oil and water phases along with single or multiple emulgent molecules will also direct the final emulsion produced in terms of mean size of the dispersed phase in the final emulsion. Interestingly, both high‐and low‐energy homogenizers will generate emulsions with nano‐range droplets particle sizes of the dispersed phase.

Microemulsion Oil‐in‐Water Nanosized Emulsion
Emulsifier concentration is high, i.e., 30–40% Emulsifier concentration is comparatively less, preferably 2–5% and can be increased up to 10%
It is a thermodynamically stable isotropic mixture It is thermodynamically unstable but kinetically stable for some time with the help of emulsifier molecule's coverage onto the dispersed oil droplet surface
Particle size ranges below 10 nm or below 100 nm Particle size ranges from 200 to 700 nm
It is toxic for parenteral application but oral dosage form is possible. Any water‐soluble API can be used All routes of application are possible

       1.1.2.1. Nanosized Emulsions: Prime Candidates for Nanoparticle Engineering