sorbitan-monooleate and 1-2-dioleoyloxy-3-(trimethylammonium)propane

The electron paramagnetic resonance (EPR) spin labeling methodology was used to analyze the interactions of phosphatidylcholine (PC) liposomal formulations that are commonly used as transepidermal drug delivery systems with stratum corneum (SC) membranes. The lipid dynamics of five liposome formulations were evaluated to study the influences of sorbitan monooleate (Span80), cholesterol, and cholesterol with the charged lipids 2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-distearoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DSPG) on the molecular dynamics of PC vesicles. The EPR spectra of 5-doxyl-stearic acid (5-DSA) showed that the addition of Span80 to the liposomes increased the lipid fluidity, whereas cholesterol had the opposite effect, and the combination of charged lipids and cholesterol did not additionally influence the lipid bilayer dynamics. Fatty acid spin-labeled SC membranes were treated with the liposome formulations, leading to migration of the spin label to the molecular environment of the formulation and the presence of two spectral components representing distinct mobility states. In terms of molecular dynamics, these environments correspond to the lipid domains of the untreated SC and the liposome, indicating a poor interaction between the liposome and SC membranes. However, the contact was sufficient to allow a pronounced exchange of the spin-labeled fatty acid. Our data suggest that flexible liposomes may access the inner intercellular membranes of the SC and facilitate mutual lipid exchange without losing their relative liposomal integrity.

Topics: Animals; Animals, Newborn; Cholesterol; Drug Compounding; Electron Spin Resonance Spectroscopy; Fatty Acids, Monounsaturated; Hexoses; Liposomes; Molecular Dynamics Simulation; Phosphatidylcholines; Phosphatidylglycerols; Quaternary Ammonium Compounds; Rats, Wistar; Skin; Skin Absorption; Technology, Pharmaceutical

Nonionic surfactant vesicles, or SPANosomes (SPs), comprised of cationic lipid and sorbitan monooleate (Span 80) were synthesized and evaluated as small interfering RNA (siRNA) vectors. The SPs had a mean diameter of less than 100 nm and exhibited excellent colloidal stability. The SP/siRNA complexes possessed a slightly positive zeta potential of 12 mV and demonstrated a high siRNA incorporation efficiency of greater than 80%. Cryogenic transmission electron microscopy (cryo-TEM) imaging of the SP/siRNA indicated a predominantly core-shell structure. The SP/siRNA complexes were shown to efficiently and specifically silence expression of both green fluorescent protein (GFP) (66% knockdown) and aromatase (77% knockdown) genes in breast cancer cell lines. In addition, the cellular trafficking pathway of the SP/siRNA was investigated by confocal microscopy using molecular beacons as probes for cytosolic delivery. The results showed efficient endosomal escape and cytosolic delivery of the siRNA cargo following internalization of the SP/siRNA complexes. In conclusion, Span 80 is a potent helper lipid, and the SPs are promising vehicles for siRNA delivery.

Topics: Aromatase; Cell Line, Tumor; Cryoelectron Microscopy; Fatty Acids, Monounsaturated; Flow Cytometry; Gene Knockdown Techniques; Green Fluorescent Proteins; Hexoses; Humans; Liposomes; Microscopy, Electron, Transmission; Nanoparticles; Oligonucleotide Probes; Particle Size; Polyethylene Glycols; Quaternary Ammonium Compounds; RNA, Small Interfering; Surface-Active Agents; Transfection; Vitamin E