Abstract
Despite the growing interest in lipid-based formulations, their polymorphism is still a challenge in the pharmaceutical industry. Understanding and controlling the polymorphic behavior of lipids is a key element for achieving the quality and preventing stability issues. This study aims to evaluate the impact of different oral-approved liquid lipids (LL) on the polymorphism, phase transitions and structure of solid lipid-based formulations and explore their influence on drug release. The LL investigated were isopropyl myristate, ethyl oleate, oleic acid, medium chain trigycerides, vitamin E acetate, glyceryl monooleate, lecithin and sorbitane monooleate. Spray-congealing was selected as an example of a melting-based solvent-free manufacturing method to produce microparticles (MPs) of tristearin (Dynasan®118). During the production process, tristearin MPs crystallized in the metastable α-form. Stability studied evidenced a slow phase transition to the stable β-polymorph overtime, with the presence of the α-form still detected after 60 days of storage at 25 °C. The addition of 10% w/w of LL promoted the transition of tristearin from the α-form to the stable β-form with a kinetic varying from few minutes to days, depending on the specific LL. The combination of various techniques (DSC, X-ray diffraction analysis, Hot-stage polarized light microscopy, SEM) showed that the addition of LL significantly modified the crystal structure of tristearin-based formulations at different length scales. Both the polymorphic form and the LL addition had a strong influence on the release behavior of a model hydrophilic drug (caffeine). Overall, the addition of LL can be considered an interesting approach to control triglyceride crystallization in the β-form. From the industrial viewpoint, this approach might be advantageous as any polymorphic change will be complete before storage, hence enabling the production of stable lipid formulations.
Highlights
The particle size distributions of MPs with liquid lipids (LL) were similar to MPs without additive, with the most representative particle size fraction corresponding to 250–355 μm, following by the fraction 355–500 μm
Our results indicated that the release of from pure tristearin
The results demonstrated that the addition of liquid lipids (LL) at a concentration of
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Lipids are applied in a wide range of products within the food, nutraceutical and pharmaceutical fields. Solid lipid-based systems, such as microparticles (MPs), pellets and tablets, are commonly used for sustained drug release [1,2]. For achieving taste masking [3]. The incorporation of active ingredients into lipid matrixes can protect labile compounds from different agents (water vapor, oxygen, and moisture) [4,5]. Lipids are widely employed for the preparation of nanocarriers including liposomes, solid lipid nanoparticles and nanostructured lipid carriers [6,7,8]
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