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Preparation and Multilayered Aggregation of Uniform Colloidal
Cholesterol Particles
Vuk Uskoković, Egon Matijević
Center for Advanced Materials Processing
Clarkson University, Potsdam, NY, USA
Results of a typical precipitation of cholesterol
Procedure for the Preparation of Uniform Cholesterol Particles:
After dissolving cholesterol in 1-propanol, water was added to supersaturate the solution. After 10 min, a few drops of the suspension were deposited onto an SEM sample carrier, dried in air and analyzed. Throughout the entire procedure, the suspension was kept undisturbed, i.e. without any agitation.
Laser Diffraction Analysis:
X-Ray Diffraction pattern
d = 33.4 Å (bilayer reflection)
d = 16.7 Å (monolayer reflection)
1.7 nm
Zeta Potential measurement:
DSC analysis:
melting
re-crystallization
Studied effects:
• Solvent effect
• Concentration effect
• pH effect
• Time effect
• Temperature effect
• Ionic strength effect
Solvent effect
2-propanol instead of 1-propanol
Methanol instead of 1-propanol
Ethanol instead of 1-propanol
Acetone instead of 1-propanol
Tech. grade isopropanol (90% purity) instead of 1-propanol
Concentration Effects
1.25 times higher solvent/non-solvent ratio
2.7 times lower solvent/non-solvent ratio
4 times lower concentration of cholesterol
4 times higher concentration of cholesterol
pH effect
pH = 7.7 (in comparison with pH = 6.3 in the “standard” procedure)
pH = 1.8 (isoelectric point)
pH = 1.3 (positively charged particles)
Aging effects
Particles sampled out from the “standard” procedure after 10 seconds of aging
Particles sampled out after 3 min of aging time
Particles sampled out after 5 min of aging time
Particles aged for one month at atmospheric conditions
Particles aged for one month at atmospheric conditions
Particles aged for one month at atmospheric conditions
Particles aged for four months at atmospheric conditions
Particles aged for four months at atmospheric conditions
Temperature effects
Particles aged for 2 days at 34 oC
Particles aged for 2 days at room T
Particles aged for 15 min at 37 oC
Particles precipitated at 31 oC and aged for 5h at 37 oC
Effect of the addition of salt
Particles obtained with the addition of 0.5 M of NaCl
Particles obtained with the addition of 0.5 M of NaCl, aged for 2.5 h
Particles obtained with the addition of 0.5 M of NaCl, aged for 2.5 h
Particles obtained with the addition of 0.05 M of BaCl2, aged for 2.5 h
Particles obtained with the addition of NaCl in c = 0.5 M after 10 min aging, aged for 2.5 h
Particles coated with silica
žžžžžž
Precipitation by solvent/non-solvent evaporation
• Particles prepared by evaporation of the unsaturated “standard” cholesterol solution
Conclusions/Achievements
1. The first reported method for preparation of uniform cholesterol particles and their stable dispersions, that can be used as models for the further aggregation and deposition studies
“Amazingly small means leading to extraordinarily satisfying results”
Ernst Fritz Schumacher, Small is Beautiful, 1973.
2. Surface charge effects evidenced as
crucial in stabilization of cholesterol dispersions
3. Increases in ionic strength (NaCl concentration) proven as leading to an increased rate of aggregation of cholesterol platelets. The direct link between artherosclerosis and high blood pressure as two major health threats in the developed world evidenced for the first time at the physicochemical level.
Preparation and Multilayered Aggregation of Uniform Colloidal
Cholesterol Particles
Vuk Uskoković, Egon Matijević
Center for Advanced Materials Processing
Clarkson University, Potsdam, NY, USA
Bile Salt
PhosphatidylcholineC
hole
ster
ol
100
80
60
40
20
100 80 60 40 20 (mol %)
20
40
60
80
100
micellar zone
Phase diagram of cholesterol in Bile (to be healthy, the composition of this 3-component system has to correspond to the micellar zone) Nick Myant (Cholesterol Metabolism, Ldl, and the Ldl Receptor)