Production and investigation of some functional properties of lipid carrier systems based on organogelation

Digestible lipids increase in the number of mixed micels formed in the small intestine and promote the bioavailability of oil-soluble bioactive agents. Lipid-based delivery systems such as nano-emulsions, solid lipid nanoparticles and nano-structured lipid carriers are therefore being designed to enhance the bioavailability of bioactive components. In this study, organogel based nano-structured emulsion systems were developed by forming nano lipid particles containing a mixture of gelator and liquid oil as their oil phase. Candelilla wax, which is capable of an organogel transition via three-dimensional crystal network, was used in the composition of oil phase of nano-emulsions as gelator. The Solid Lipid Nanoparticle (SLN), Liquid Lipid Nanoparticle (LLN) and Nanostructured Lipid Carrier (NLC) systems, which were formed with the oil phases of Candelilla wax, corn oil and their mixtures respectively, the impact of lipid phase alteration on the physical properties and gastrointestinal fates of the particles were investigated using a simulated gastrointestinal tract (GIT) model. After exposure to mouth, gastric and intestinal conditions, changes in particle size, particle charge and microstructures of samples were analysed. Although the samples exhibit similar behavior in the simulated GIT in terms of their particle properties, it was observed that SLN samples could not be digested by lipase activity, and the triglyceride composition of LLN and NLC samples were completely digested, the lipase activity in the NLC sample was not inhibited in the presence of Candelilla wax. The complex mixture of 𝛾-oryzanol and 𝛽-sitosterol, which can form organogels via self-assembled nano-sized fibril networks, was used as gelator in order to structure rice bran oil phase of organogel based nano-emulsions. The effect of the gelator component, known that have antioxidant properties, on the chemical stability of 𝛽-carotene was analyzed under accelerated test conditions and it was shown that encapsulation of 𝛽-carotene with organogel based nano-emulsion system improves the stability comparing to LLN system. In addition, NLC samples containing 15% and 30% gelator mixture in the oil phase and the LLN sample were investigated at the in vitro GIT conditions in terms of particle size, particle charge and microstructurel changes. It was determined that the organojel nano-emulsion sample containing a mixture of 15% gelator in the oil phase was found to be able to reach from the mouth phase up to the small intestine phase invariably while the particle stability in NLC-30% and LLN samples could not being maintained. The highest 𝛽-carotene bioaccessibility was measured on NLC-15% sample indicating that particle stability of samples in the human GIT conditions is significantly important for high bioaccessibility. In order to investigate the effect of 𝛾-oryzanol and 𝛽-sitosterol on the oxidative stability of flaxseed oil; the nano-emulsions prepared with the oil phases of MCT (medium chain triglycerides), 𝛾-oryzanol and 𝛽-sitosterol were mixed in a 1:1 ratio with the nano-emulsions prepared with only flaxseed oil. The physical stability of the samples during the storage under accelerated oxidation conditions was determined by particle size and charge analysis and microscope images besides oxidative stability by PV (peroxide value) and TBARS (thiobarbituric acid reactive substances) analysis. At the end of storage, organogel nano-emulsion sample prepared with 𝛾-oryzanol and 𝛽-sitosterol complex was found to be physically more stable than other samples. The most effective oxidative stability due to the differences in the transfer of organogelator components between different type of nano-emulsion droplets was determined in the sample which the 𝛾-oryzanol and 𝛽-sitosterol nano-emulsions were prepared separately and mixed afterwards with flaxseed nanoemulsion.