Hydrolysis of Partially Saturated Egg Phosphatidylcholine in Aqueous Liposome Dispersions and the Effect of Cholesterol Incorporation on Hydrolysis Kinetics

Abstract

Hydrolysis kinetics of partially hydrogenated egg phosphatidylcholine (PHEPC) were studied as a function of pH, temperature, buffer concentration, ionic strength, and the effect of cholesterol incorporation. Results showed that PHEPC has a maximum stability at around pH 6.5. General acid base catalysis was observed for acetate, HEPES and Tris buffers. Increasing the ionic strength of the buffer solutions did not influence the hydrolysis kinetics. The relationship between the observed hydrolysis rate constants and the temperature could adequately be described by the Arrhenius equation. Incorporation of cholesterol did not affect the hydrolysis kinetics. This result indicates that the hydrolysis kinetics of PHEPC do not depend on the changes in bilayer rigidity induced by cholesterol incorporation. Cholesterol is stable under the experimental conditions used in this study; no changes were observed in cholesterol concentration over the experimental time interval.

Effect of Charge Carrier Lipid on Skin Penetration, Retention, and Hair Growth of Topically Applied Finasteride-Containing Liposomes

“…Cholesterol was added to protect phosphatidylcholine from oxidation and to provide rigidity to the liposome vesicles (Allen et al, 1991;Grit et al, 1993). Weight percentage of the charge carrier lipid was varied from 1-10% to see the effect on physical properties and hair growth of the liposomal formulations.…”

Effect of Gamma Irradiation on the Physical Stability of DPPC Liposomes

“…These products may result from the hydrolysis process of DPPC (Vernooij et al 2002). However, it was proven in reports by Grit et al (1993aGrit et al ( , 1993bGrit et al ( , 1993c, that hydrolysis in a storage medium yielded a very low amount (<1%) of LPC when DPPC was exposed to gamma rays; indicating that hydrolysis is not the primary mode of degradation in the application of gamma irradiation. Additionally, the degradation route in this study can be explained as follows: As the irradiated samples were diluted, .…”

Stabilization of Plasmid DNA and Lipid-Based Therapeutics as Dehydrated Formulations

“…The carboxy esters which form the connection between the glycerol backbone and the fatty acid tails are most susceptible to hydrolytic degradation. Lysophospholipids can also be further hydrolyzed leading to the formation of glycerophospho compounds and fatty acids [245]. Hydrolysis can be acid or base catalyzed.…”

“…The hydrolysis of lipids leads to the formation of lysophospholipids and fatty acids [245]. The carboxy esters which form the connection between the glycerol backbone and the fatty acid tails are most susceptible to hydrolytic degradation.…”