ABSTRACT
DPPC/Cholesterol liposomes of average diameter below 100nm were used as a matrix for calcium carbonate precipitation. Adsorption of calcium ions on the vesicles was determined via zeta potential measurement. It was found that with increasing calcium ions concentration the electrokinetic potential of the vesicles varied toward more positive values. The changes became smaller with the cholesterol content increase. Accumulation of calcium ions close to the vesicles membranes lead to attraction of CO(3)(2-) ions and enhances nucleation and growth of small calcium carbonate crystals that aggregates within lipid vesicles forming porous balls aggregates. However, dipalmitoylphosphatidylcholine (DPPC) does not change the CaCO(3) crystal forms and calcite is the only form obtained during precipitation. Moreover, the influence of the phospholipid on the calcium carbonate precipitation is enhanced by the induction of cholesterol to the lipid membranes.
Subject(s)
1,2-Dipalmitoylphosphatidylcholine/chemistry , Calcium Carbonate/chemistry , Cholesterol/chemistry , Liposomes/chemistry , Drug Carriers , Electrochemistry , Membranes, Artificial , Microscopy, Electron, Scanning , Particle Size , Spectrum Analysis, Raman , SuspensionsABSTRACT
In this paper, usefulness of the Langmuir monolayer study is demonstrated for predictions of the stability of liposomes composed of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol (Chol). Thermodynamic analysis of the surface pressure (π)-area (A) isotherms of the DPPC/Chol systems was performed, which allowed for concluding on miscibility of the components, their molecular packing, and the interactions between molecules. It was found that the most stable system, in which the strongest interactions between molecules occured, was DPPC/Chol at x(Chol)=0.25. The stability of liposomes of the same composition as that in the Langmuir monolayers was analyzed by determining the size distribution of vesicles and the polydispersity as a function of time. The changes of these parameters confirmed that the system of the greatest stability is that with low Chol content.
Subject(s)
Liposomes/chemistry , 1,2-Dipalmitoylphosphatidylcholine , Cholesterol , Membranes, Artificial , ThermodynamicsABSTRACT
Electrolyte solutions were exposed for different time to weak static magnetic field (MF) generated from a stack of magnets (B = 15 mT) at the flow rate of 1.4 mL/s. The conductivity was measured as a function of time following the application of MF. It was found that the changes in conductivity depend on the kind of electrolyte and the magnetic exposure time and are related to the thermodynamic function of hydration.
ABSTRACT
Magnetic field (MF) (B = 0.4 T) effects were studied on CaCO3 precipitated from Na2CO3 and CaCl2 solutions, which at 30 degrees C were exposed for 30 min to the field. One of the impurity ions Mg2+, Zn2+, Fe2+, SO4(2-), HPO4(2-) at 10(-5) mol l(-1) concentration was also added to CaCl2 or Na2CO3, respectively. The changes of zeta potential, pH and light absorbance (at lambda = 543.2 nm) of the slurry after CaCO3 precipitation were measured on the time. In some experiments changes in the deposited amounts of CaCO3 due to MF treatment were determined on glass plates. MF affected all the parameters measured and the effects depended on the kind of impurity ion present.
Subject(s)
Calcium Carbonate/chemistry , Electromagnetic Fields , Water Supply , Chemical Precipitation , CorrosionABSTRACT
The histological pictures of the adrenal cortex of spontaneously hypertensive rats were investigated with autoradiographic and morphometric methods. No differences, between the tritiated thymidine index of SHR and controls were detected in the 3 cortex zones. In contrast to the normal fasciculated zone a decreased number of cells per area was shown in the zona fasciculata with hypertension depended findings.
