Unpurified soybean lecithins impact on the chemistry of proliposomes and liposome dispersions encapsulating vitamin D3

Abstract

Vitamin D3 (VD3)-loaded proliposomes using the micronized sucrose coating (MSC) technique and mixtures of soybean lecithins with variable degrees of purity were prepared. The phospholipid powders were characterized in terms of water activity, moisture content, solubility, hygroscopicity, moisture adsorption isotherms and the retained amount of VD3. X-ray diffraction and Fourier transform infrared spectroscopy were the techniques applied to investigate molecular interactions among the ingredients during the coating process, as well as the crystalline structure of the phospholipid powders. Liposome dispersions were produced by hydration of the proliposomes. The liposomal systems were analyzed in terms of hydrodynamic diameter, size distribution, zeta potential and the amount of encapsulated VD3. The morphologies of proliposomes and liposomes were observed using scanning electron microscopy and atomic force microscopy, respectively. The VD3-proliposomes showed low values for water activity, moisture content and solubility as well as high values for hygroscopicity. Liposome dispersions were in the nanometer range and showed high values for zeta potential, but remained stable for only 15 days, probably due to the high concentrations of unpurified lecithin used throughout the process (≥50% w/w). However, the content of VD3 in proliposomes and in loaded-liposome dispersions reached 81.4 and 90.2%, respectively. The results suggested that it was feasible to prepare VD3-entrapped proliposomes using the MSC method, but storage conditions must be better controlled to maintain their stability.