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Acid-catalyzed plasmenylcholine hydrolysis and its effect on bilayer permeability: a quantitative study
O V Gerasimov1, A Schwan, D H Thompson
1Department of Chemistry, Purdue University, West Lafayette, IN 47907-1393, USA.
Biochimica Et Biophysica Acta
|March 13, 1997
Summary
Plasmenylcholine liposomes release contents when hydrolyzed or photooxidized. Dihydrocholesterol content significantly impacts release rates, influencing the design of triggerable liposomes for drug delivery.
Area of Science:
- Biochemistry
- Physical Chemistry
- Materials Science
Background:
- Plasmenylcholine (PlsPamCho) liposomes release hydrophilic contents upon photooxidation or acid-catalyzed hydrolysis.
- Previous studies established the release phenomenon, but detailed kinetics and mechanisms were lacking.
Purpose of the Study:
- To elucidate the kinetics and chemical mechanism of acid-catalyzed hydrolysis of plasmenylcholine.
- To investigate the effect of this hydrolysis and dihydrocholesterol (DHC) content on calcein leakage rates from liposomes.
- To understand the products and mechanisms of plasmenylcholine photooxidation.
Main Methods:
- High-Performance Liquid Chromatography (HPLC) and Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy to identify hydrolysis products.
- Kinetic analysis to determine rate constants for lysolipid formation and hydrolysis.
- Calcein leakage assays to quantify the effect of hydrolysis and DHC on liposome permeability.
Main Results:
- Acid-catalyzed hydrolysis of PlsPamCho generates fatty aldehydes and lysolipid, with the lysolipid undergoing rearrangement.
- Lysolipid formation follows pH-dependent first-order kinetics.
- Calcein release is significantly reduced by the presence of dihydrocholesterol (DHC); DHC-free liposomes show rapid release (<5% hydrolysis), while 25 mol% DHC requires ~30% hydrolysis for similar release.
Conclusions:
- The study provides detailed kinetics and mechanisms for acid-catalyzed and photooxidative degradation of plasmenylcholine liposomes.
- Dihydrocholesterol content is a critical factor in modulating membrane permeability changes induced by plasmenylcholine hydrolysis.
- Findings are crucial for understanding lysolipid effects on membrane permeability and designing responsive liposomes for drug delivery applications.