Cholesterol encapsulated

One frozen dessert is made with Simplesse, a protein-based fat mimetic that contains no fat (37). Other dairy product developments include a fat flavor, produced by encapsulating milk fatty acids in maltodextrins (38) fat-free cottage cheeses and 2% fat milk, prepared by steam stripping cream with partial fat addback, with a cholesterol level about 60% lower than the starting material (39). 

Data about curcunfin encapsulated in liposomes have been reported recently. The authors encapsulated curcumin into a liposomal delivery system in order to study the in vitro and in vivo effects of this compound on proliferation, apoptosis, signaling, and angiogenesis using human pancreatic carcinoma cells. Carotenoids of different polarities and in competition with cholesterol were specifically incorporated into liposomes in order to mimic the physiological uptake by cells and monitor their antioxidant capacities. ... 

Li, L., Braiteh, F.S., and Kurzrock, R., Liposome-encapsulated curcumin in vitro and in vivo effects on proliferation, Apopf. Signal. Angiogen. Cancer, 104, 1322, 2005. Socaciu, C., Jessel, R., and Diehl, H.A., Competitive carotenoid and cholesterol incorporation into liposomes effects on membrane phase transition, fluidity, polarity... 

Probucol, another di-r-butyl phenol, is an anti-atherosclerotic agent that can suppress the oxidation of low-density lipoprotein (LDL) in addition to lowering cholesterol levels. The antioxidant activity of probucol was measured, using EPR, with oxidation of methyl linoleate that was encapsulated in liposomal membranes or dissolved in hexane. Probucol suppressed ffee-radical-mediated oxidation. Its antioxidant activity was 17-fold less than that of tocopherol. This difference was less in liposomes than in hexane solution. Probucol suppressed the oxidation of LDL as efficiently as tocopherol. This work implies that physical factors as well as chemical reactivity are important in determining overall lipid peroxidation inhibition activity (Gotoh et al., 1992). 

The fate of injected liposomes is drastically altered by administration route, dose and size, lipid composition, surface modification, and encapsulated drugs. Liposomes encapsulating drugs are often administered iv, therefore, the stability of liposomes in plasma is important. When liposomes composed of PC with unsaturated fatty acyl chains are incubated in the presence of serum, an efflux of internal solute from the liposomes is observed. This increase in permeability is caused by the transfer of phospholipids to high density lipoprotein (HDL) in serum (55). To reduce the efflux of liposomal contents, cholesterol is added as a liposomal component... 

Fig. 23 Saliva and serum IgA (primary and secondary) response following orally administered soluble antigen Streptococcus mutans cell wall extract (open circles, soluble antigen solid circles, liposome-encapsulated material) (phosphatidylcholine, phosphatidic acid, cholesterol). (From Ref. 277).

Liposomes made from pure phosphatidylcholine or containing lipids that are found in the cell membrane complex of wool (e.g. cholesterol) have been used to encapsulate aqueous chlorine solutions in chlorination processes [61,62]. The results showed improvements in... 

The correct ratio of lipid constituents is important to form stable liposomes. For instance, a reliable liposomal composition for encapsulating aqueous substances may contain molar ratios of lecithin cholesterol negatively charged phospholipid (e.g., phosphatidyl glycerol (PG)) of 0.9 1 0.1. A composition that is typical when an activated phosphatidylethanolamine (PE) derivative is included may contain molar ratios of phosphatidylcholine (PC) cholesterol PG derivatized PE of 8 10 1 1. Another typical composition using a maleimide derivative of PE without PG is PC male-imide-PE cholesterol of 85 15 50 (Friede et al., 1993). In general, to maintain membrane stability, the PE derivative should not exceed a concentration ratio of about l-10mol PE per lOOmol of total lipid. 

Figure 2 Encapsulation as a function of ethanol concentration. Oligonucleotides were added to distearoyl-phosphatidyl-choline/cholesterol/l-0-(2 -(co-methoxy-poly-ethylene-glycol)succinoyl)-2-iV-myristoyl-sphingosine /1,2-dioleoyl-3-dimethylam-monium propane liposomes in varying concentrations of ethanol at an initial oligonucleotide-to-lipid ratio of 0.24mg/mg. Abbreviations AS, antisense oligonucleotide %EtOH(v/v), percentage of ethanol in volume/volume.

Recently, this method was adapted to label two commercially available liposomal formulations doxorubicin encapsulated in polyethylene glycol (PEG)-coated liposomes (Caelyx /Doxil ) (14) and daunorubicin encapsulated in small distearoyl-phosphatidyl-choline/cholesterol liposomes (Daunoxome ) (15). Although no DTPA was encapsulated in these liposomes, the labeling efficiency was typically between 70% and 80% and the radiolabeled preparations were stable in vivo during the time course of the experiment (four hours). Most likely, the lipophilic In-oxine avidly associates with the lipid bilayer and encapsulation of DTPA might not be necessary when the experimental observation period does not exceed four to six hours. 

The exact mechanism responsible for the uptake of liposomes by KCs and SECs is not clear. Most studies confirm internalization of whole liposomes in an energy-dependent phagocytic process in which the liposomes are delivered to the lysosomes. The liposomal lipids are completely degraded and the encapsulated solutes released. Neutral liposomes consisting of lipids such as cholesterol and phosphatidylcholine are probably cleared by receptor-mediated mechanisms, due to the adsorption of opsonizing proteins onto the hpid bi-... 

Practically all available iodinated extracellular X-ray contrast agents have been encapsulated into liposomes using different lipids and methods of preparation. Table 1 gives a short and intentionally incomplete overview of some of the approaches. The first liposomal contrast agent preparation that was tested in humans contained diatrizoate [48]. The injected dose was up to 0.5 ml kg k The preparation was effective even in plain radiography where lesions down to 0.8-1.0 cm could be detected in patients. However, adverse events such as fever and hyperthermia, which occurred in 30% of the patients, limited further use. We have incorporated iopromide into MLVs that were prepared from phosphatidyl choline (PC), cholesterol and stearic acid at a molar ratio of 4 5 1 using the ethanol-evaporation technique [44]. The liposomes can be stored freeze-dried and they are reconstituted before use by... 

Fig. 1 Schematic illustration of a liposome encapsulating a hydrophilic drug. The membrane contains phospholipid and cholesterol molecules. (Reprinted with permission from Ref. 3 with slight modification. Copyright 1998 Adis International.)... 

Cheese, for example, has been demonstrated in clinical trials to have a smaller effect in raising LDL-cholesterol in comparison to butter and even milk (Tholstrup et al., 2004). Cheese is unique from other dairy products due to its physical structure, whereby its fat content is encapsulated within a casein structure (Fellows, 2000). 

A number of works investigated the interaction between niosomes and human skin. With niosomes prepared from Ci2 alcohol polyoxyethylene ether and cholesterol, vesicular structures of about 100 nm size have been observed between the first and second layers of human corneocytes 48 h after incubation as well as in the deeper strata of the skin [37], The authors concluded that the structures visualized in the deeper regions could be vesicles reorganized from individual molecules that penetrated the skin. In another study, electron micrographs illustrated that niosomes containing surfactants and cholesterol affected only the most superficial corneocytes. Moreover, two-photon fluorescence microscopy confirmed that fluorescent probe encapsulated in niosomes was confined to the intercellular spaces within the apical stratum corneum layers [56]. 

More recently, Carafa et al. showed that niosomes could be obtained from polyoxyethylene sorbitan monolaurate-cholesterol in aqueous environment. These authors investigated the delivery of lidocaine HC1 and lidocaine base from vesicles through silicone membrane and nude mice skin [44]. It was found that only the charged molecule (loading pH 5.5) could be encapsulated within the vesicles ( 30%). This behavior was explained by the entrapment ability of the hydrophilic moiety within the aqueous core of the vesicles. The lipophilic unionized form of lidocaine (loading pH 8.6) remained unattached. The amount of lidocaine permeated through nude mice skin from these niosomes was similar to liposomes and only about twofold greater than from a micellar system. 

The stability of various niosomal formulations depends on factors such as preparation methods, storage temperature, the encapsulated drug, the surfactants, and additive mixture [41,52,64,65], It may be possible to stabilize niosomes by a variety of methods such as the use of membrane-spanning lipids, the interfacial polymerization of surfactant monomers in situ, addition of polymerized surfactants, cholesterol, steric and electrostatic stabilizers to the formulation [41,52]. In general, vesicle aggregation may be prevented by inclusion of... 

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