Influence Of Lipid Concentration Research Articles

Influence of lipid concentration on encapsulation and particle size in the development of liposomal irinotecan

Purpose. For creation of liposomal irinotecan form, the influence of lipid concentration on the encapsulation of the active substance and nanoparticle size was necessary to investigate. Materials and methods . We used «chemical gradient method for liposomes formulation, in the variety of “pH gradient”. Ammonium citrate at pH 2.5 was used as internal buffer. Lipid film was obtained, by evaporation technics with further high pressure homogenization with Microfluidics Microfluidizer M-110P apparatus. “Chemical gradient” was created by ultrafiltration, with “Minim 2” apparatus. Ultrafiltration cartridge with an upper cut-off 30 kDa was used. Encapsulation was measured using HPLC methods developed in variant of gel chromatography, with Shimadzu LC-20 instrument. The particle size was measured by laser diffraction method withe “Zetasizer Nano ZS” instrument. Results. For the preparation of liposomes was applied a constant lipid ratio with varying of total lipid concentration. The ratio of lipids in the experiment was a phosphatidylcholine / cholesterol 80/20 % by weight. A total concentration was investigated in range from 10 mg/ml to 30 mg/ml. The number of extrusion cycles consisted from 3 cycles at 1500 bar, in case of 10 mg/ml concentration, to 17 cycles at 1500 bar, in case of 30 mg/ml concentration. Conclusions . It was shown that the lipid concentration from 25 mg/ml led to particles formation with size more than 5000 nm, and it was not possible to reduce them by high pressure homogenization method. It was proven that the most optimal, in terms of technology and the final characteristics of liposomes, was lipids in concentration 20 mg/ml. The degree of encapsulation in this case was 82 ± 0.98 %. The size of the liposomes was 106 nm, 5000 nm particles were absent.

The effect of a lipid composition and a surfactant on the characteristics of the solid lipid microspheres and nanospheres (SLM and SLN)

Solid lipid microparticles (SLM) were produced by a two-step process that, firstly, involved the emulsification of the molten lipid phase in a heated aqueous phase and, secondly, the system cooling. Compritol 888 ATO and Precirol ATO 5, including their mixtures with Miglyol 812 or Witepsol H15 were used as lipid components (10–30% w/w). The average size of the SLM prepared with Compritol and Tween 80 as an emulsifier was 3–7μm and the influence of lipid concentration and thermal sterilization was not large. Dispersions of SLM with Precirol (10–20% w/w) gellified upon storage. SLM stabilized with another surfactant, Tego Care 450, were larger in size and measured 40μm on average. The use of the sonication step (5–15min) in hot formulations containing 5% w/w of Compritol resulted in the formation of the solid lipid nanoparticles (SLN) with average size 200–300nm. The smallest SLN size (below 100nm on average) was obtained in SLN that contained Tego Care and an antimicrobial agent Euxyl PE 9010; such combination evoked synergism between the surfactant and Euxyl components.

Preparation of a New Oligolamellar Stratum Corneum Lipid Model.

In this study, we present a preparation method for a new stratum corneum (SC) model system, which is closer to natural SC than the commonly used multilayer models. The complex setup of the native SC lipid matrix was mimicked by a ternary lipid mixture of ceramide [AP], cholesterol, and stearic acid. A spin coating procedure was applied to realize oligo-layered samples. The influence of lipid concentration, rotation speed, polyethylenimine, methanol content, cholesterol fraction, and annealing on the molecular arrangement of the new SC model was investigated by X-ray reflectivity measurements. The new oligo-SC model is closer to native SC in the total number of lipid membranes found between corneocytes. The reduction in thickness provides the opportunity to study the effects of drugs and/or hydrophilic penetration enhancers on the structure of SC in full detail by X-ray or neutron reflectivity. In addition, the oligo-lamellar systems allows one to infer not only the lamellar spacing, but also the total thickness of the oligo-SC model and changes thereof can be monitored. This improvement is most helpful for the understanding of transdermal drug administration on the nanoscale. The results are compared to the commonly used multilamellar lipid model systems and advantages and disadvantages of both models are discussed.

Impact of Lipid Content on the Ability of Excipient Emulsions to Increase Carotenoid Bioaccessibility from Natural Sources (Raw and Cooked Carrots)

The influence of lipid concentration on the ability of excipient emulsions to increase carotenoid bioaccessibility from raw and cooked carrots was investigated using a simulated gastrointestinal tract (GIT). Excipient emulsions were fabricated using whey protein as a natural emulsifier and a long chain triglyceride (corn oil) as a digestible lipid. Changes in particle size, charge, and microstructure were determined as the carrot-emulsion mixtures were passed through simulated mouth, stomach, and small intestine. Carotenoid bioaccessibility increased with increasing digestible lipid concentration in the excipient emulsions (from 0 to 8 %). Carotenoid bioaccessibility was higher from boiled carrots than for raw carrots, which was attributed to disruption of plant cell structure facilitating carotenoid release. In conclusion, excipient emulsions are highly effective at increasing carotenoid bioaccessibility from carrots, which can be attributed to the ability of the small lipid droplets to rapidly solubilize the carotenoids.

Anaerobic digestion of lipid-rich waste—Effects of lipid concentration

The influence of lipid concentration on hydrolysis and biomethanation of a lipid-rich (triolein) model waste was evaluated in batch. The effect of increasing the concentration of lipid from 5% to 47% (w/w), based on chemical oxygen demand (COD), was investigated. The methane recovery observed was above 93% for all tests. An initial lag phase of approximately 6–10 days was observed for all tests. The methane production rate observed was similar for tests with 5%, 10% and 18% lipid (w/w, COD basis). For higher amounts of lipid (31%, 40% and 47%), a stronger inhibition was observed. However, the process was able to recover from the inhibition. When the effect of addition of lipase on enzymatic hydrolysis of lipids was studied, the results showed that the higher the enzyme concentration, the more accentuated was the inhibition of methane production. The enzyme appears to enhance the hydrolysis but the intermediates produced caused inhibition of the later steps in the degradation process. Since the volatile fatty acid (VFA) profiles presented similar trends for the different concentrations of lipid tested, the major obstacle to methane production was the long-chain fatty acids (LCFA) formation.

Hydrogen Peroxide/Oxygen Biosensor Based on Supported Phospholipid Bilayer

Abstract The influence of lipid concentration, lipid composition, pH and temperature on the stability and function of metal-supported phospolipid bilayer membranes (s-BLM) was studied and the potential applicability of this system in biosensor development was explored. Parameters to be measured were the resistance as well as the amperometric response of the system to oxygen and hydrogen peroxide. Stability and function of the s-BLM system are inversely related to the lipid concentration. Cholesterol exerts a stabilizing effect at a molar ratio of 4:1 to 1:3 (PC : choiesterol). The effect of stearylamine on membrane stability depends on the sign of the polarizing voltage. Ascorbic acid, but not citric acid nor glutathion nor uric acid interferes with measurements of hydrogen peroxide. The s-BLM is remarkably stable in urine. Its use as a simple but sensitive oxygen sensor for measuring the respiration rate of rat liver mitochondria is demonstrated.