Abstract
The interactions between carotenoids and membrane constituents are vital for understanding the mechanism of their dynamic action. Lutein and beta-carotene were loaded separately into the bilayer of dipalmitoylphosphatidylcholine (DPPC) mixed at a molar ratio with l-α-phosphatidylethanolamine derived from sheep brain (cephalin) and stearylamine (SA) to form cationic liposomes. The molecular interaction between lutein or beta-carotene with cationic liposomes was studied using transmission electron microscopy (TEM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. Encapsulation efficiency (EE %) and in vitro drug release were determined. The DLS measurements confirmed the mono-dispersity of all samples. TEM results revealed that liposomal samples were oval-shaped and there was a change in their morphology and size upon encapsulation of lutein or beta-carotene. Beta-carotene was observed to adhere to the boundary surface within the liposomal assembly with external morphological alterations. EE% of lutein and beta-carotene exceeded 98.8 ± 0.3% and 87 ± 4%, respectively. Lutein doped with cationic liposomes shows better in vitro release stability (about 30%) than beta-carotene (about 45%) between the 3rd and the 6th hour manifested by lower leakage rate percentage of lutein which would lead to higher lutein retention. The incorporated lutein resulted in broadening and shifting of the major endothermic peak of the co-liposomes, while the incorporation of beta-carotene did not induce a noticeable shift. An FTIR study was employed to reveal structure alterations in the vesicles after the encapsulation of lutein or beta-carotene into liposomes. Encapsulation of lutein or beta-carotene into liposomes induced a change in the frequency of the symmetric and asymmetric CH2 stretching bands in the acyl chain that may influence the order of the membrane.
Highlights
Membranes are biological barriers which protect cells from the exterior environment
EE% values of lutein and beta-carotene, respectively, exceeded 98.8 Æ 0.3% and 87 Æ 4% even though the molar ratio to lipid was at 2 : 7. The LC of lutein and beta-carotene were exceeded 22% and 18% which are very close to their IC values (2 : 7 correspond to 28.57%), indicating that the added carotenoids can be effectively incorporated into a liposomal membrane Table 1
Lutein or beta-carotene leakage from liposomes formulation imparted with the positive surface charge was examined versus time in hours by the incubation in Phosphate buffer saline (PBS) at 37 C
Summary
Membranes are biological barriers which protect cells from the exterior environment. On the other hand, they selectively allow the permeation of ions and other small molecules to facilitate cellular signaling and promote cell homeostasis.[1,2,3] they have the ability to selectivity degrade toxins (such as free radicals) that pass into the cell, which can result in damage to DNA and other cellular components. Carotenoids are lipophilic pigments which are found in the tissues of bacteria, plants and animals.[4,5] Dietary carotenoids play an important role in vision, as antioxidants and as preventive actors in cancer, cardiovascular or skin diseases. They are biosynthesized in plants and microorganisms and play a role in photosynthesis and photoprotection. Liposomes have long been receiving much consideration owing to their biocompatibility and interesting ability to carry hydrophobic and hydrophilic compounds. Due to their similarity with the bilayer structure of natural membranes, liposomes are used as a membrane model. The similarity between the liposomal and membrane bilayer core makes liposomes a very useful tool to inspect the consequence of carotenoids–membrane interactions.[8,9]
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