Supercritical fluid anti-solvent precipitation has been attracting widespread attention due to its distinctive advantages, and has exhibited a great perspective of application in the production of polymer-based composite micro- and nanoparticles. In this study, based on the experiment results of production of carotene-loaded polymer PEG or l-PLA composite microparticles using solution enhanced dispersion by supercritical fluids through prefilming atomization (SEDS-PA) process, the possible mechanism of dispersing an active component in a polymeric carrier by the SEDS-PA co-precipitation was deduced. The mechanism is mainly the formation and growth of the active component (carotene) nuclei in the polymer-rich phase induced by mass transfer and phase transition, and the polymer capture/encapsulation of active component particles generated in an expanded solution droplet caused by the collision among these particles and polymer-rich phase. There are four factors that could influence the sizes and morphologies of the SEDS-PA precipitates. They are, respectively, atomization of solution, prompt and persistent super-saturation of the expanded droplets, breakup of the expanded droplets with interstices and the particle agglomeration caused by collision in the SEDS-PA process. The integrated effect of these factors dominates the sizes and morphologies of the SEDS precipitates.
Active Component Carotene Supercritical Fluid Baicalin Polymeric Carrier
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The authors gratefully acknowledge the financial supports of the national natural science foundation of China (Grant No. 20266004) of 863 project of China (Grant No. 2003AA2Z3533) and of natural science foundation of Inner Mongolia (China) (Grant No. 200308020203).