Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory.

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension.

Freeze-Fracture Electron Microscopy on Domains in Lipid Mono- and Bilayer on Nano-Resolution Scale.

Freeze-fracture electron microscopy (FFEM) as a cryofixation, replica, and transmission electron microscopy technique is unique in membrane bilayer and lipid monolayer research because it enables us to excess and visualize pattern such as domains in the hydrophobic center of lipid bilayer as well as the lipid/gas interface of lipid monolayer. Since one of the preparation steps of this technique includes fracturing the frozen sample and since during this fracturing process the fracture plane follows the area of weakest forces, these areas are exposed allowing us to explore pattern built up by lipids and/or intrinsic proteins but also initiated by peptides, drugs, and toxins reaching into these normally hard to access areas. Furthermore, FFEM as a replica technique is applicable to objects of a large size range and combines detailed imaging of fine structures down to nano-resolution scale within images of larger biological or artificial objects up to several tens of micrometers in size.

Protein-containing PEGylated cubosomic particles: freeze-fracture electron microscopy and synchrotron radiation circular dichroism study.

The purpose of this work is to investigate the entrapment of protein molecules in cubosomic nanocarriers that are sterically stabilized by an amphiphilic poly(ethylene glycol) (PEG) derivative. Toward that aim, the mechanism of fragmentation of a self-assembled, PEGylated cubic lipid phase into nanoparticles (NPs) is investigated in excess aqueous medium. The molar ratio between the cubic-phase-forming lipid monoolein (MO) and its PEGylated derivative (MO-PEG(2000)) is selected as to favor the formation of inverted-type liquid-crystalline (LC) structures (permitting one to reveal the stages of the fragmentation and bicontinuous membrane NP assembly process) rather than a phase transformation to lamellar or micellar phases.

In vitro optimization of liposomal nanocarriers prepared from breast tumor cell specific phage fusion protein.

Fusion proteins created by phage display peptides with tumor cell specificity and the pVIII major coat protein of filamentous phages have been explored recently as a simple and cost-effective means for preparing tumor-targeted liposomes that improve the cytotoxicity of anticancer drugs in vitro. The next step in the development of this approach is the optimization of the liposome composition for the maximum targeting activity and subsequent testing in vivo. This study aimed to investigate the impact of preparation protocols, lipid composition and phage protein content on the targeting efficiency of phage protein-modified liposomes.

Saposin C coupled lipid nanovesicles enable cancer-selective optical and magnetic resonance imaging.

Purpose: Nanovesicles composed of the phospholipid dioleylphosphatidylserine (DOPS) and a fusogenic protein, saposin C (SapC), selectively target and induce apoptotic cell death in a variety of human cancer cells in vitro and in vivo. We tested whether such tumor-homing nanovesicles are capable of delivering fluorescent probes and magnetic resonance (MR) contrast agents to cancerous tissue to aid in earlier detection and improve visualization.

Procedures: SapC-DOPS nanovesicles labeled with either a far-red fluorescent probe (CellVue® Maroon, CVM) or conjugated with a dextran coated MR contrast agent, ultrasmall superparamagnetic iron oxide (USPIO), were systemically administrated into xenografts for tumor detection using optical and MR imaging systems.

Enhanced binding and killing of target tumor cells by drug-loaded liposomes modified with tumor-specific phage fusion coat protein.

Aim: To explore cancer cell-specific phage fusion pVIII coat protein, identified using phage display, for targeted delivery of drug-loaded liposomes to MCF-7 breast cancer cells.

Material & Methods: An 8-mer landscape library f8/8 and a biopanning protocol against MCF-7 cells were used to select a landscape phage protein bearing MCF-7-specific peptide. Size and morphology of doxorubicin-loaded liposomes modified with the tumor-specific phage fusion coat protein (phage-Doxil) were determined by dynamic light scattering and freeze-fraction electron microscopy.

Lipid clustering by three homologous arginine-rich antimicrobial peptides is insensitive to amino acid arrangement and induced secondary structure.

Three Arg-rich nonapeptides, containing the same amino acid composition but different sequences, PFWRIRIRR-amide (PR-9), RRPFWIIRR-amide (RR-9) and PRFRWRIRI-amide (PI-9), are able to induce segregation of anionic lipids from zwitterionic lipids, as shown by changes in the phase transition properties of lipid mixtures detected by differential scanning calorimetry and freeze fracture electron microscopy. The relative Minimal Inhibitory Concentration (MIC) of these three peptides against several strains of Gram positive bacteria correlated well with the extent to which the lipid composition of the bacterial membrane facilitated peptide-induced clustering of anionic lipids. The lower activity of these three peptides against Gram negative bacteria could be explained by the retention of these peptides in the LPS layer.

Freeze-fracture electron microscopy on domains in lipid mono- and bilayer on nano-resolution scale.

Freeze-fracture electron microscopy (FFEM) as a cryo-fixation, replica, and transmission electron microscopy technique is unique in membrane bilayer and lipid monolayer research because it enables us, to excess and visualize pattern such as domains in the hydrophobic center of lipid bilayer as well as the lipid/gas interface of the lipid monolayer. Since one of the preparatory steps of this technique includes fracturing the frozen sample and, since during this fracturing process the fracture plane follows the area of weakest forces, these areas are exposed allowing us to explore the pattern built up by lipids and/or intrinsic proteins and which are also initiated by peptides, drugs, and toxins reaching into these normally hard to access areas. Furthermore, FFEM as a replica technique is applicable to objects of a large size range and combines detailed imaging of fine structures down to nano-resolution scale within images of larger biological or artificial objects up to several ten's of micrometers in size.

C3b deposition on human erythrocytes induces the formation of a membrane skeleton-linked protein complex.

Decay-accelerating factor (DAF, also known as CD55), a glycosylphosphatidylinositol-linked (GPI-linked) plasma membrane protein, protects autologous cells from complement-mediated damage by inhibiting complement component 3 (C3) activation. An important physical property of GPI-anchored complement regulatory proteins such as DAF is their ability to translate laterally in the plasma membrane. Here, we used single-particle tracking and tether-pulling experiments to measure DAF lateral diffusion, lateral confinement, and membrane skeletal associations in human erythrocyte membranes.

Self-assembling micelle-like nanoparticles based on phospholipid-polyethyleneimine conjugates for systemic gene delivery.

With few exceptions, where local administration is feasible, progress towards broad clinical application of gene therapies requires the development of effective delivery systems. Here we report a novel non-viral gene delivery vector, 'micelle-like nanoparticle' (MNP) suitable for systemic application. MNP were engineered by condensing plasmid DNA with a chemical conjugate of phospholipid with polyethylenimine (PLPEI) and then coating the complexes with an envelope of lipid monolayer additionally containing polyethylene glycol-phosphatidyl ethanolamine (PEG-PE), resulting in spherical 'hard-core' nanoparticles loaded with DNA.

Targeted tumor cell internalization and imaging of multifunctional quantum dot-conjugated immunoliposomes in vitro and in vivo.

Targeted drug delivery systems that combine imaging and therapeutic modalities in a single macromolecular construct may offer advantages in the development and application of nanomedicines. To incorporate the unique optical properties of luminescent quantum dots (QDs) into immunoliposomes for cancer diagnosis and treatment, we describe the synthesis, biophysical characterization, tumor cell-selective internalization, and anticancer drug delivery of QD-conjugated immunoliposome-based nanoparticles (QD-ILs). Pharmacokinetic properties and in vivo imaging capability of QD-ILs were also investigated.

Biophysical characterization of an integrin-targeted lipopolyplex gene delivery vector.

Nonviral gene delivery vectors now show good therapeutic potential: however, detailed characterization of the composition and macromolecular organization of such particles remains a challenge. This paper describes experiments to elucidate the structure of a ternary, targeted, lipopolyplex synthetic vector, the LID complex. This consists of a lipid component, Lipofectin (L) (1:1 DOTMA:DOPE), plasmid DNA (D), and a dual-function, cationic peptide component (I) containing DNA condensation and integrin-targeting sequences.

Carbohydrate-based micelle clusters which enhance hydrophobic drug bioavailability by up to 1 order of magnitude.

Amphiphilic chitosan-based polymers (Mw < 20 kDa) self-assemble in aqueous media at low micromolar concentrations to give previously unknown micellar clusters of 100-300 nm in size. Micellar clusters comprise smaller 10-30 nm aggregates, and the nanopolarity/drug incorporation efficiency of their hydrophobic domains can be tailored by varying the degree of lipidic derivatization and molecular weight of the carbohydrate. The extent of drug incorporation by these novel micellar clusters is 1 order of magnitude higher than is seen with triblock copolymers, with molar polymer/drug ratios of 1:48 to 1:67.

Protein driven patterning of self-assembled cubosomic nanostructures: long oriented nanoridges.

Self-assembly lipid/protein cubosomic nanostructures are generated at high hydration level (dispersion of 5% lipid only) and examined by freeze-fracture electron microscopy (FF-EM) and synchrotron X-ray diffraction (XRD). The fracture surface of the three-dimensional (3D) soft-matter membranous assembly reveals starlike nanopatterns of oriented 100-nm-long cubosomic nanoridges with lateral periodicity defined by their 21-nm diameters. The average water channel radius in these liquid crystalline cubosomic nanoarchitectures, determined by high-resolution FF-EM and XRD, is 18.

Detailed structure of diamond-type lipid cubic nanoparticles.

Supramolecular three-dimensional self-assembly of nonlamellar lipids with fragments of the protein immunoglobulin results in a bicontinuous cubic phase fragmented into nanoparticles with open water channels (cubosomes). The structure of the diamond-type cubic nanoparticles is characterized experimentally by freeze-fracture electron microscopy, and it is mathematically modeled with nodal surfaces emphasizing the fluid-like undulations of the cubosomic interfaces. Based on scaling-up and scaling-down approaches, we present stable and intermediate-kind nanoparticles resulting from the cubosomic growth.

Proteocubosomes: nanoporous vehicles with tertiary organized fluid interfaces.

Proteocubosomes are nanostructured open-nanochannel hierarchical fluid vehicles characterized by a cubic lattice periodicity of the lipid/protein supramolecular assembly (protein-loaded cubosomes). They are obtained here at very high hydration levels by a three-dimensional (3D) self-assembly process, which exploits a protein-directed 3D patterning and fragmentation to create a new, tertiary-level structural order of fluid lipid/water interfaces. Our freeze-fracture electron microscopy study reveals that the proteocubosome structures are built up by patterned assemblies of nanocubosomes, which comprise 3D nanoporous fracture surfaces throughout.

A novel system for reducing leaching from formulations of anionic herbicides: clay-liposomes.

A new approach was developed for reducing leaching of herbicides and contamination of groundwater. Liposome-clay formulations of the anionic herbicides sulfometuron and sulfosulfuron were designed for slow release by incorporating the herbicide in positively charged vesicles of didodecyldimethylammonium (DDAB), which were adsorbed on the negatively charged clay, montmorillonite. Freeze fracture electron microscopy demonstrated the existence of DDAB vesicles and aggregated structures on external clay surfaces.

Immunomicelles: targeted pharmaceutical carriers for poorly soluble drugs.

To prepare immunomicelles, new targeted carriers for poorly soluble pharmaceuticals, a procedure has been developed to chemically attach mAbs to reactive groups incorporated into the corona of polymeric micelles made of polyethylene glycol-phosphatidylethanolamine conjugates. Micelle-attached antibodies retained their ability to specifically interact with their antigens. Immunomicelles with attached antitumor mAb 2C5 effectively recognized and bound various cancer cells in vitro and showed an increased accumulation in experimental tumors in mice when compared with nontargeted micelles.

Cell transfection in vitro and in vivo with nontoxic TAT peptide-liposome-DNA complexes.

Liposomes modified with TAT peptide (TATp-liposomes) showed fast and efficient translocation into the cell cytoplasm with subsequent migration into the perinuclear zone. TATp-liposomes containing a small quantity ( View Article and Find Full Text PDF

Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite.

The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption of hexadecyltrimethylammonium (HDTMA) and octadecyltrimethylammonium (ODTMA) on montmorillonite was studied above and below their critical micelle concentrations (CMC).