Uniform particles of pure and silica-coated cholesterol

Abstract

Uniform crystalline colloidal cholesterol particles of narrow size distribution were obtained by precipitation. The method consisted of adding a miscible non-solvent (water) into cholesterol solutions of different alcohols and acetone, without any additives. The properties of the resulting particles depended in a sensitive way on the concentration of all reactants, temperature, pH, ionic strength, and aging time. The major observed effects were due to the solubility of cholesterol, which was strongly affected by the solvent mixture and temperature. Precipitation in 1-propanol/water system yielded stable dispersions of well-defined particles, which were used to evaluate the effects of different experimental parameters on their properties. Aging of stable dispersions resulted in multi-layered aggregation of the primary platelets, the degree and rate of which process was strongly affected by temperature. Finally, it was shown that the colloidal cholesterol particles could be coated with homogeneous silica layers in order to alter their surface characteristics.

Dynamic Light Scattering Based Microelectrophoresis: Main Prospects and Limitations

“…Recently, the same concept was invoked to explain the aggregation of cholesterol particles, pointing out that a control over ζ potential may be used to prevent the formation of pathological cholesteric deposits, including atherosclerotic plaque and gallstones. [30–32] These findings are on the line of Thomas Riddick’s invoking ζ potential to explain the “salting out” effect of ions on coagulation in blood, including the effect of thrombosis. [1] It is also worth noting that Nature never disperses its entities using exceptionally high negative ζ potential values.…”

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

“…343,344,345 LaSr-manganite particles were thus coated with silica, 346 whereas cholesterol platelets were coated using sodium silicate solution and a procedure involving a reaction with an ion-exchange resin. 347 A challenge would be to coat CAP particles with Au (metal-ceramic coatings are difficult to achieve owing to different thermal expansion coefficients between the two components among other factors), but if succeeded, such particles shelled with Au could be used for photothermal therapies and diagnostics, such as optical coherence tomography. 348 The absorption efficiency of Au is a few orders of magnitude higher than that of conventional photothermal dyes, and Au surfaces can be facilely functionalized with antibodies and other bioactive molecules.…”

Surface Charge Effects Involved in the Control of Stability of Sols Comprising Uniform Cholesterol Particles

“…1), which accounts for the observed "face-to-face" aggregation of cholesterol particles. Whereas well-defined cholesterol platelets were produced within pH conditions that corresponded to either positively or negatively charged particle surfaces, precipitation at the isoelectric point due to reduced surface charge repulsion resulted in the formation of mutually stacked platelets [6]. A further confirmation of the importance of electrostatic effects in the control of stability of cholesterol dispersions came from the experiments in which increased rates of aggregation of cholesterol platelets were observed in the presence of electrolytes [ Fig.…”

“…This study appears to be the first to describe the preparation of uniform colloidal crystallites of cholesterol [6]. The dispersions obtained hereby can serve as viable model systems for the study of the effects of various physical and chemical environments on the formation, stability, and interactions of cholesterol crystals with different solutes and substrates [7].…”