Palmitate Particle

The resulting set of line shapes allows for an easy estimation of rotational correlation times based on the solid-state spectrum of dispersed cetyl palmitate particles. 

The saponified fatty acids which are used are most often palmitic, stearic or oleic acid but the way in which they confer a hydrophobic nature to the surface of the ink particle is not well understood. If enough calcium ions are present (and these sometimes need to be added to the system) insoluble calcium salts of the fatty acids are probably produced and these may coat the surface of the print particle making it hydrophobic. The ink particle then adheres to an air bubble and can be floated out of the stock. The saponified fatty acids are often called collectors —a term which comes from mineral flotation. 

The generally low lipid content and the poor viscosity of lipid nanodispersions make these preparations, as they are, less suitable for dermal drug application. The handling of the preparation by the patient is improved by SLN incorporation into ointments, creams, and gels. Alternatively, ready-to-use preparations may be obtained by one-step production, increasing the lipid phase to at least 30%. However, increasing the lipid frequently results in an unwanted increase in particle size. Surprisingly, it has been found that very concentrated (30 to 40%) semisolid cetyl palmitate formulations preserve the colloidal particle size [10]. 

Fig. 3. A dry powder microbubble precursor agent particles of water-soluble material (e.g., galactose) are coated with a surfactant (e.g., palmitic acid). Air or other gas is located in the spaces between particles. When water is added and galactose rapidly dissolved, gas-filled spaces between particles become individual microbubbles dispersed in the aqueous phase...

The provision of fat-soluble vitamins and lipids is difficult, if not impossible, in various diseases. This is especially true for diseases that are accompanied by a lot of oxidative stress, for example, mucoviscidosis. The requirements of fat-soluble antioxidative substances are certainly high in these cases and can barely be covered by intramuscular injections because fat-soluble vitamins can hardly, if at all, be absorbed from oily preparations. Alternatively, the vitamins can administered via the buccal mucosa the fat-soluble substances have to be packaged in such a way that they can be transported in a watery compartment and are thus able to largely dissolve in the saliva. When they have an adequate size, they can then penetrate the buccal mucosa. One approach is the development of the so-called nanocolloids, that is, particles with a polar nucleus, in which the fat-soluble vitamin is dissolved, and an apolar wrapping (monolayer). This structure makes an oral application of fat-soluble substances possible. First tests demonstrated that vitamin A palmitate, a-tocopherol, as well as coenzyme Qio are thus able to enter the systemic circulation via the buccal mucosa. 

White particle f Ca Ca salt of fatty acid (Ca palmitate)... 

Solid lipids, emulsifiers, and water are generally the ingredients involved for manufacturing SLNs. The term lipids is used in a broader sense and includes triglycerides (e.g., stearin), partial glycerides (e.g., Imwitor), fatty acids (e.g., stearic acid), steroids (e.g., cholesterol), and waxes (e.g., cetyl palmitate). All categories of emulsifiers may be used to stabilize the lipid dispersion, and the combination of emulsifiers prevents particle agglomeration more efficiently. The choice of the emulsifier depends on the administration route and is more limited for parenteral administration. 

Similar results to those obtained here by the stability measurements have been reported by Roe and Brass (7.8) They studied polystyrene latex stabilized by potassium palmitate. The analysis supplied by these authors shows that the order of magnitude of the slope of the stability curves can be accounted for as an entropic effect of crowding of adsorbed molecules during an encounter between two particles. They pointed this out as a possible explanation as the amount of emulsifier adsorbed strongly affects the stability without altering the electrophoreti-cally derived double-layer potential. 

Figure 1-5. Separation of selected representatives of different lipid classes. (1) Paraffin, (2) K-hexadecyl palmitate (3) cholesterol palmitate (4) stearic acid methyl ester (5) glycerol tripalmitate (6) hexadecyl alchohol (7) stearic acid (8) cholesterol (9) glycerol-1,3-dipalmitate (10) glycerol-l,2-dipalmitate (11) glycerol monopalmitate (12) erucylamide. Column LiChrosphere Diol (125 x 3mm) 5- xm particles. Gradient from isooctane (A) to 60% methyl tritbutyl ether (MTBE) in 34min -t lOmin isocratic hold. (Reprinted from reference 14, with permission.)...

Cholesterol is formed in the liver (85%) and intestine (12%) - this constitutes 97% of the body s cholesterol synthesis of 3.2 mmol/day (= 1.25 g/day). Serum cholesterol is esterized to an extent of 70-80% with fatty acids (ca. 53% linolic acid, ca 23% oleic acid, ca 12% palmitic acid). The cholesterol pool (distributed in the liver, plasma and erythrocytes) is 5.16 mmol/day (= 2.0 g/day). Homocysteine stimulates the production of cholesterol in the liver cells as well as its subsequent secretion. Cholesterol may be removed from the pool by being channelled into the bile or, as VLDL and HDL particles, into the plasma. The key enzyme in the synthesis of cholesterol is hydroxy-methyl-glutaryl-CoA reductase (HGM-CoA reductase), which has a half-life of only 3 hours. Cholesterol is produced via the intermediate stages of mevalonate, squalene and lanosterol. Cholesterol esters are formed in the plasma by the linking of a lecithin fatty acid to free cholesterol (by means of LCAT) with the simultaneous release of lysolecithin. (s. figs. 3.8, 3.9) (s. tab. 3.8)... 

Fig. 33. Comparison of MAS proton spectra for QlO-loaded solid lipid particles (top) with corresponding spectra of the solid lipid cetyl palmitate (centre) and the active ingredient QIO (bottom) ...

Particle sizes of diazepam-loaded SLN showed similar changes after sterilization as did drug-free systems. Steam sterilization (121 °C, 20 min) did not cause changes in particle size and zeta potential of azidothymidine palmitate-loaded SLN (trilaurin, phospholipid stabilized) [47],... 

Heiati compared the influence of four cryoprotectors (trehalose, glucose, lactose, and mannitol) on the particle size of azidothymidine palmitate-loaded SLN lyophilizates [47], Trehalose was found to be the most effective cryoprotector for preventing aggregation during lyophilization and subsequent reconstitution of SLN. A sugar/lipid weight ratio of 2.6 to 3.9 was recommended. 

---