Solid lipid microparticles (SLMs), combined with the advantages of double emulsions (W/O/W) and water-in-oil micro emulsions, are developed for transdermal administration. A modified one-step emulsification method was introduced, which made the industrial production of SLMs easier. Variables involved in preparation that may affect the solubility, stability, and entrapment efficiency of SLMs were investigated. With vitamin C as a model active, the advantages of SLMs in transdermal administration were studied further. Vitamin C, encapsulated by SLMs, exhibited an enhanced storage stability up to 1 month under 25°C and a sustained releasing profile over 24 h. Furthermore, the SLMs was very helpful in delivering vitamin C molecules into skin through stratum corneum. The result showed 5.52-fold (p < 0.05) increased absorption of vitamin C, compared to the vitamin C solution. These studies demonstrate that SLMs could be a promising method for facilitating transdermal penetration of active ingredients with high solubility and low permeability.Practical applications: SLMs could be used as a drug delivery system for hydrophilic active ingredients with low permeability. Experiments have shown better stability and skin permeability of vitamin C incorporated in SLMs when compared with pure vitamin C. Furthermore, the method of producing SLMs is simple and can be realized in a way of industrial production. Since SLMs can dissolve in water, SLMs can be directly used on wet skin with excellent skin-touch feel. As a result, SLMs could be a practical delivery system for hydrophilic compounds with low permeability in many applications such as pharmaceuticals and cosmetics.
A novel drug delivery system, multiple solid particles (MLPs), combining the advantages of water-in-oilin-water (W/O/W) multiple emulsions and solid lipid nanoparticles (SLN) was proposed. The MLPs were produced by simply adding the solid lipid in liquid lipid of W/O/W multiple emulsions and removing the outer aqueous phase of W/O/W multiple emulsions. MLPs could form typical W/O/W multiple emulsion microstructure by self-emulsifying after dispersing in water. MLPs were used to encapsulate both coenzyme Q10 and tea polyphenols (CT-MLPs), and encapsulation efficiency measurement revealed that both coenzyme Q10 and tea polyphenols had high encapsulation efficiency (98.14% and 99.36%, respectively). The effect of the factors on viscosity, stability, and solubility of CTMLPs were investigated, and the results showed that increasing the concentration of solid lipid glycerin monostearate or hydrophilic emulsifier polyglyceryl-10 laurate, or decreasing the concentration of the inner aqueous phase could increase the viscosity of CT-MLPs. Consequently, the stability of CT-MLPs was improved by increasing the viscosity of the oil phase. Moreover, addition of glycerin monostearate also increased the water solubility of CT-MLPs. During a 60-day stability study, CT-MLPs showed terrific stability and high retention ratio (above 83.82%) at various conditions.
Practical applications:MLPs could act as a drug delivery system to encapsulate both lipophilic active compounds and hydrophilic active compounds, since the active compounds in MLPs had high encapsulation efficiency. MLPs also improved the photostability and storage stability of coenzyme Q10 and tea polyphenols. Furthermore, the production procedure of MLPs is a two-step stirring method, which is widespread and easy to handle. And the lipids for producing MLPs are physiological lipids, the choice of emulsifiers depends on the administration route. With regard to industrial production aspects, MLPs have the chance to be exploited as drug delivery system in commercial products. Hence, MLPs could be applicable delivery systems for food, cosmetic, and pharmaceutical applications.
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