A theoretical approach to describe monolayer-liposome lipid interaction

Comparison of cubosomes and liposomes for the encapsulation and delivery of curcumin

Inverse bicontinuous cubic phase nanoparticles (cubosomes) have attracted significant attention in recent years, owing to their potential use as delivery vehicles for chemically fragile or poorly soluble drugs and nutraceuticals. Herein we have investigated the use of lipid nanoparticles as a delivery vehicle for curcumin, a compound with demonstrated anti-cancer properties. Curcumin is encapsulated within cubosomes comprised of several different lipid formulations, as well as phospholipid-based liposomes. The entrapment efficiency of curcumin within cubosomes was observed to vary depending on both the nanoparticle architecture and the curcumin concentration. Fluorescence spectroscopy analysis revealed that penetration of curcumin into the hydrophobic region of the bilayer was dependent on lipid composition. Curcumin was typically associated with the polar headgroup region at low concentrations, but transferred to the lipid bilayer region at higher concentrations, particularly in phytantriol cubosomes. Each nanoparticle formulation was characterized using small angle X-ray scattering and dynamic light scattering to assess the structural stability subsequent to curcumin encapsulation. The structure of the cubosomes was generally robust to the addition of curcumin, while the liposomes displayed a large increase in particle size and PDI at higher curcumin concentrations. Finally, the cytotoxicity of each formulation was assessed against murine fibroblast (NIH3T3) and murine melanoma (B16F10) cell lines in order to investigate improvements in curcumin bioavailability following encapsulation in cubosomes, as well as assess potential anti-cancer applications. Increased cytotoxicity of the cubosome-loaded curcumin against the murine melanoma cell-line demonstrates the potential of these nanoparticles as delivery vehicles for curcumin and other poorly water-soluble drugs.

Magnetic properties of γ-Fe2O3 nanoparticles in a porous SiO2 shell for drug delivery

A method is presented for synthesizing core-shell nanoparticles with a magnetic core and a porous shell suitable for drug delivery and other medical applications. The core contains multiple γ-Fe2O3 nanoparticles (∼15 nm) enclosed in a SiO2 (∼100-200 nm) matrix using either methyl (denoted TMOS-γ-Fe2O3) or ethyl (TEOS-γ-Fe2O3) template groups. Low-temperature Mössbauer spectroscopy showed that the magnetic nanoparticles have the maghemite structure, γ-Fe2O3, with all the vacancies in the octahedral sites. Saturation magnetization measurements revealed that the density of γ-Fe2O3 was greater in the TMOS-γ-Fe2O3 nanoparticles than TEOS-γ-Fe2O3 nanoparticles, presumably because of the smaller methyl group. Magnetization measurements showed that the blocking temperature is around room temperature for the TMOS-γ-Fe2O3 and around 250 K for the TEOS-γ-Fe2O3. Three dimensional topography analysis shows clearly that the magnetic nanoparticles are not only at the surface but have penetrated deep in the silica to form the core-shell structure.

Interaction of curcumin with lipid monolayers and liposomal bilayers

Curcumin shows huge potential as an anticancer and anti-inflammatory agent. However, to achieve a satisfactory bioavailability and stability of this compound, its liposomal form is preferable. Our detailed studies on the curcumin interaction with lipid membranes are aimed to obtain better understanding of the mechanism and eventually to improve the efficiency of curcumin delivery to cells. Egg yolk phosphatidylcholine (EYPC) one-component monolayers and bilayers, as well as mixed systems containing additionally dihexadecyl phosphate (DHP) and cholesterol, were studied. Curcumin binding constant to EYPC liposomes was determined based on two different methods: UV/Vis absorption and fluorescence measurements to be 4.26×10(4)M(-1) and 3.79×10(4)M(-1), respectively. The fluorescence quenching experiment revealed that curcumin locates in the hydrophobic region of EYPC liposomal bilayer. It was shown that curcumin impacts the size and stability of the liposomal carriers significantly. Loaded into the EYPC/DPH/cholesterol liposomal bilayer curcumin stabilizes the system proportionally to its content, while the EYPC/DPH system is destabilized upon drug loading. The three-component lipid composition of the liposome seems to be the most promising system for curcumin delivery. An interaction of free and liposomal curcumin with EYPC and mixed monolayers was also studied using Langmuir balance measurements. Monolayer systems were treated as a simple model of cell membrane. Condensing effect of curcumin on EYPC and EYPC/DHP monolayers and loosening influence on EYPC/DHP/chol ones were observed. It was also demonstrated that curcumin-loaded EYPC liposomes are more stable upon interaction with the model lipid membrane than the unloaded ones.

Preparation and characterization of chitosan poly(acrylic acid) magnetic microspheres

Spherical microparticles, capable of responding to magnetic fields, were prepared by encapsulating dextran-coated Fe3O4 nanoparticles into chitosan poly(acrylic acid) (PAA) microspheres template. The obtained magnetic microspheres were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and thermogravimetry (TG). The results showed that the microspheres were formed and demonstrated magnetic behavior in an applied magnetic field. In addition, magnetite particles were well encapsulated and the composite particles have high magnetite content, which was more than 40%.

Anti-angiogenic perfluorocarbon nanoparticles for diagnosis and treatment of atherosclerosis

Complementary developments in nanotechnology, genomics, proteomics, molecular biology and imaging offer the potential for early, accurate diagnosis. Molecularly-targeted diagnostic imaging agents will allow noninvasive phenotypic characterization of pathologies and, therefore, tailored treatment close to the onset. For atherosclerosis, this includes anti-angiogenic therapy with specifically-targeted drug delivery systems to arrest the development of plaques before they impinge upon the lumen. Additionally, monitoring the application and effects of this targeted therapy in a serial fashion will be important. This review covers the specific application of alpha(nu)beta(3)-targeted anti-angiogenic perfluorocarbon nanoparticles in (1) the detection of molecular markers for atherosclerosis, (2) the immediate verification of drug delivery with image-based prediction of therapy outcomes, and (3) the serial, noninvasive observation of therapeutic efficacy.

Endothelial alpha(v)beta3 integrin-targeted fumagillin nanoparticles inhibit angiogenesis in atherosclerosis

OBJECTIVE

Angiogenic expansion of the vasa vasorum is a well-known feature of progressive atherosclerosis, suggesting that antiangiogenic therapies may stabilize or regress plaques. Alpha(v)beta3 integrin-targeted paramagnetic nanoparticles were prepared for noninvasive assessment of angiogenesis in early atherosclerosis, for site-specific delivery of antiangiogenic drug, and for quantitative follow-up of response.

METHODS AND RESULTS

Expression of alpha(v)beta3 integrin by vasa vasorum was imaged at 1.5 T in cholesterol-fed rabbit aortas using integrin-targeted paramagnetic nanoparticles that incorporated fumagillin at 0 microg/kg or 30 microg/kg. Both formulations produced similar MRI signal enhancement (16.7%+/-1.1%) when integrated across all aortic slices from the renal arteries to the diaphragm. Seven days after this single treatment, integrin-targeted paramagnetic nanoparticles were readministered and showed decreased MRI enhancement among fumagillin-treated rabbits (2.9%+/-1.6%) but not in untreated rabbits (18.1%+/-2.1%). In a third group of rabbits, nontargeted fumagillin nanoparticles did not alter vascular alpha(v)beta3-integrin expression (12.4%+/-0.9%; P>0.05) versus the no-drug control. In a second study focused on microscopic changes, fewer microvessels in the fumagillin-treated rabbit aorta were counted compared with control rabbits.

CONCLUSIONS

This study illustrates the potential of combined molecular imaging and drug delivery with targeted nanoparticles to noninvasively define atherosclerotic burden, to deliver effective targeted drug at a fraction of previous levels, and to quantify local response to treatment.

Targeted antiproliferative drug delivery to vascular smooth muscle cells with a magnetic resonance imaging nanoparticle contrast agent: implications for rational therapy of restenosis

BACKGROUND

Restenosis is a serious complication of coronary angioplasty that involves the proliferation and migration of vascular smooth muscle cells (VSMCs) from the media to the intima, synthesis of extracellular matrix, and remodeling. We have previously demonstrated that tissue factor-targeted nanoparticles can penetrate and bind stretch-activated vascular smooth muscles in the media after balloon injury. In the present study, the concept of VSMC-targeted nanoparticles as a drug-delivery platform for the prevention of restenosis after angioplasty is studied.

METHODS AND RESULTS

Tissue factor-targeted nanoparticles containing doxorubicin or paclitaxel at 0, 0.2, or 2.0 mole% of the outer lipid layer were targeted for 30 minutes to VSMCs and significantly inhibited their proliferation in culture over the next 3 days. Targeting of the nanoparticles to VSMC surface epitopes significantly increased nanoparticle antiproliferative effectiveness, particularly for paclitaxel. In vitro dissolution studies revealed that nanoparticle drug release persisted over one week. Targeted antiproliferative results were dependent on the hydrophobic nature of the drug and noncovalent interactions with other surfactant components. Molecular imaging of nanoparticles adherent to the VSMC was demonstrated with high-resolution T1-weighted MRI at 4.7T. MRI 19F spectroscopy of the nanoparticle core provided a quantifiable approach for noninvasive dosimetry of targeted drug payloads.

CONCLUSIONS

These data suggest that targeted paramagnetic nanoparticles may provide a novel, MRI-visualizable, and quantifiable drug delivery system for the prevention of restenosis after angioplasty.

A metastable state of high surface activity produced by sonication of phospholipids

Sonication of phosphatidylcholine dispersions generates a metastable high energy assembly of molecules, the existence of which is revealed by its conspicuous surface activity. Freshly sonicated liposome dispersions release molecules to the air/water interface at rates sufficient to produce a close-packed monolayer within minutes. In contrast, monolayers at the surface of multilamellar and extruded vesicles take hours to form. The highly surface active species appears within the first few minutes of sonication, long before a major reduction in turbidity occurs, and accumulates over the course of a few hours of sonication. It disappears upon exhaustive sonication, extrusion, addition of extruded vesicles, or, more slowly, simply on standing. Tests for extraneous substances in the lipids before as well as after sonication revealed amounts of degradation products too small to represent the observed surfactant. Direct evidence that the metastable aggregate releases intact phospholipids was provided by a novel procedure to characterize monolayer composition by comparing surface tension with surface potential, both as a function of surface density. Centrifugation and gel filtration chromatography indicate that the surface activity is associated with a particle of diameter larger than a lysophosphatidylcholine micelle but not larger than limit sonicated vesicles. The metastable material appears to be lipid molecules in other than the normal stable vesicular state, perhaps an incompletely closed vesicle, one in which the inner and outer monolayers have not equilibrated, or possibly a micellar form.