Pla Microsphere Lab Report

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2.3 Fabrication of PLA microsphere
The term “microsphere” refers to small spherical particles having diameters of micrometer ranging from 1–1000 µm. Microspheres is also known as microparticles (Bao et al., 2006). Good microspheres should fulfill these requirements: (1) able to maintain the stability and biological activity of the drug during the encapsulation process, (2) the size is smaller than 250 µm, (3) the amount of drug released should not beyond the specified limit, and (4) must be in the form of pure powder without containing any impurities and form aggregates or coagulant (Jain, 2000).
There are many ways to prepare PLA microspheres including emulsification technique with single or double solvent evaporation system (Bao et al.,
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Surfactants of emulsions are amphiphilic which means it contain both hydrophilic and hydrophobic groups. So when emulsion, the surfactant covers the surface of drops with its hydrophobic part in the drop and its hydrophilic part in the water. Typically, there are four types of surfactants: anionic, cationic, amphoteric and non-ionic. The anionic surfactants such as sodium dodecyl sulphate (SDS) release a negative charge in the aqueous solution. They have a relatively high level of hydrophilicity. Conversely, cationic surfactants such as cetyltrimethyl ammonium bromide (CTAB) release a positive charge in an aqueous solution. On the other hand, in alkali pH, amphoteric surfactants act as anionic while in acid pH, it act as cationic. Non-ionic surfactants such as partially hydrolyzed PVA (polyvinyl alcohol) have no charge (Li et al, 2008). Among four types of surfactants, partially hydrolyzed PVA is most frequent used because it gives the smallest microsheres (Jeffrey et al, 1991). The amount of PVA used may affect microparticles properties. Freitas and coworkers have added 1.3% and 8% of PVA into an aqueous solution and found that both lower and higher concentrations of surfactant results in coagulation of the particles. Hence, these authors suggested to use 3% of PVA as it the most optimum concentration. (Freitas and Marchetti,
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