3D Columnar Phase of Stacked Short DNA Organized by Coherent Membrane Undulations.

We report on the discovery of a new organized lipid-nucleic acid phase upon intercalation of blunt duplexes of short DNA (sDNA) within cationic multilayer fluid membranes. End-to-end interactions between sDNA leads to columnar stacks. At high membrane charge density, with the inter-sDNA column spacing () comparable but larger than the diameter of sDNA, a 2D columnar phase (i.

Inhibition of Microtubule Depolymerization by Osmolytes.

Microtubule dynamics play a critical role in the normal physiology of eukaryotic cells as well as a number of cancers and neurodegenerative disorders. The polymerization/depolymerization of microtubules is regulated by a variety of stabilizing and destabilizing factors, including microtubule-associated proteins and therapeutic agents (e.g.

Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments.

We describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors.

Single filament behavior of microtubules in the presence of added divalent counterions.

Microtubules (MTs) are hollow biopolymeric filaments that function to define the shape of eukaryotic cells, serve as a platform for intracellular vesicular transport, and separate chromosomes during mitosis. One means of physiological regulation of MT mechanics and dynamics, critical to their adaptability in such processes, is through electrostatics due to the strong polyelectrolyte nature of MTs. Here, we show that in the presence of physiologically relevant amounts of divalent salts, MTs experience a dramatic increase in persistence length or stiffness, which is counter to theoretical expectations and experimental observations in similar systems (e.

Biomolecular motors in nanoscale materials, devices, and systems.

Biomolecular motors are a unique class of intracellular proteins that are fundamental to a considerable number of physiological functions such as DNA replication, organelle trafficking, and cell division. The efficient transformation of chemical energy into useful work by these proteins provides strong motivation for their utilization as nanoscale actuators in ex vivo, meso- and macro-scale hybrid systems. Biomolecular motors involved in cytoskeletal transport are quite attractive models within this context due to their ability to direct the transport of nano-/micro-scale objects at rates significantly greater than diffusion, and in the absence of bulk fluid flow.

Stacking of Short DNA Induces the Gyroid Cubic-to-Inverted Hexagonal Phase Transition in Lipid-DNA Complexes.

Lyotropic phases of amphiphiles are a prototypical example of self-assemblies. Their structure is generally determined by amphiphile shape and their phase transitions are primarily governed by composition. In this paper, we demonstrate a new paradigm for membrane shape control where the electrostatic coupling of charged membranes to short DNA (sDNA), with tunable temperature-dependent end-to-end stacking interactions, enables switching between the inverted gyroid cubic structure (Q) and the inverted hexagonal phase (H).

A continuous network of lipid nanotubes fabricated from the gliding motility of kinesin powered microtubule filaments.

Synthetic interconnected lipid nanotube networks were fabricated on the millimeter scale based on the simple, cooperative interaction between phospholipid vesicles and kinesin-microtubule (MT) transport systems. More specifically, taxol-stabilized MTs, in constant 2D motion via surface absorbed kinesin, extracted and extended lipid nanotube networks from large Lα phase multilamellar liposomes (5-25 μm). Based on the properties of the inverted motility geometry, the total size of these nanofluidic networks was limited by MT surface density, molecular motor energy source (ATP), and total amount and physical properties of lipid source material.

Synthesis and characterization of degradable multivalent cationic lipids with disulfide-bond spacers for gene delivery.

Gene therapy provides powerful new approaches to curing a large variety of diseases, which are being explored in ongoing worldwide clinical trials. To overcome the limitations of viral gene delivery systems, synthetic nonviral vectors such as cationic liposomes (CLs) are desirable. However, improvements of their efficiency at reduced toxicity and a better understanding of their mechanism of action are required.

Nanogyroids incorporating multivalent lipids: enhanced membrane charge density and pore forming ability for gene silencing.

The self-assembly of a custom-synthesized pentavalent cationic lipid (MVL5) and glycerol monooleate (GMO) with small interfering RNA (siRNA) results in the formation of a double-gyroid bicontinuous inverted cubic phase with colocalized lipid/siRNA domains as shown by synchrotron X-ray scattering and fluorescence microscopy. The high charge density (due to MVL5) and positive Gaussian modulus of the GMO-containing membranes confer optimal electrostatic and elastic properties for endosomal escape, enabling efficient siRNA delivery and effective, specific gene silencing.

Two-dimensional packing of short DNA with nonpairing overhangs in cationic liposome-DNA complexes: from Onsager nematics to columnar nematics with finite-length columns.

We report the formation of liquid crystalline (LC) phases of short double-stranded DNA with nonpairing (nonsticky) overhangs, confined between two-dimensional (2D) lipid bilayers of cationic liposome-DNA complexes. In a landmark study (Science2007, 318, 1276), Nakata et al. reported on the discovery of strong end-to-end stacking interactions between short DNAs (sDNAs) with blunt ends, leading to the formation of 3D nematic (N) and columnar LC phases.

Highly efficient gene silencing activity of siRNA embedded in a nanostructured gyroid cubic lipid matrix.

RNA interference (RNAi) is an evolutionarily conserved sequence-specific post-transcriptional gene silencing pathway with wide-ranging applications in functional genomics, therapeutics, and biotechnology. Cationic liposome-small interfering RNA (CL-siRNA) complexes have emerged as vectors of choice for delivery of siRNA, which mediates RNAi. However, siRNA delivery by CL-siRNA complexes is often inefficient and accompanied by lipid toxicity.

Structural responses of DNA-DDAB films to varying hydration and temperature.

The structure of a DNA-dimethyldidodecylammonium bromide (DDAB) film was recently described to undergo a distinctive transition in response to the water content in the surrounding environment. The existence, preparation, and basic properties of DNA-surfactant films have been known in the literature for some time. Here, we describe the structural response of DNA-DDAB films to environmental changes, particularly temperature and humidity, in greater detail revealing new structural states.

Cationic liposome-nucleic acid complexes for gene delivery and silencing: pathways and mechanisms for plasmid DNA and siRNA.

Motivated by the promises of gene therapy, there is great interest in developing non-viral lipid-based vectors for therapeutic applications due to their low immunogenicity, low toxicity, ease of production, and the potential of transferring large pieces of DNA into cells. In fact, cationic liposome (CL) based vectors are among the prevalent synthetic carriers of nucleic acids (NAs) currently used in gene therapy clinical trials worldwide. These vectors are studied both for gene delivery with CL-DNA complexes and gene silencing with CL-siRNA (short interfering RNA) complexes.

Non-viral gene delivery with cationic liposome-DNA complexes.

A large amount of research activity worldwide is currently directed towards developing lipid- or polymer-based, non-viral gene vectors for therapeutic applications. This strong interest is motivated by their low toxicity, ease of production, ability to transfer large pieces of DNA into cells, and lack of immunogenic protein components. Cationic liposomes (CLs) are one of the most powerful non-viral vectors.

Structure and gene silencing activities of monovalent and pentavalent cationic lipid vectors complexed with siRNA.

Small interfering RNAs (siRNAs) of 19-25 bp mediate the cleavage of complementary mRNA, leading to post-transcriptional gene silencing. We examined cationic lipid (CL)-mediated delivery of siRNA into mammalian cells and made comparisons to CL-based DNA delivery. The effect of lipid composition and headgroup charge on the biophysical and biological properties of CL-siRNA vectors was determined.

Dendritic cationic lipids with highly charged headgroups for efficient gene delivery.

Gene therapy is expected to lead to powerful new approaches for curing many diseases, a potential that is currently explored in worldwide clinical trials. Nonviral DNA delivery systems are desirable to overcome the inherent problems of viral vectors, but their current efficiency requires improvement and the understanding of their mechanism of action is incomplete. We have synthesized new multivalent cationic lipids with highly charged dendritic headgroups to probe the structure-transfection efficiency relationships of cationic liposome (CL)-DNA complexes, a prevalent nonviral vector.

A columnar phase of dendritic lipid-based cationic liposome-DNA complexes for gene delivery: hexagonally ordered cylindrical micelles embedded in a DNA honeycomb lattice.

Gene therapy holds great promise as a future approach to fighting disease and is explored in worldwide clinical trials. Cationic liposome (CL)-DNA complexes are a prevalent nonviral delivery vector, but their efficiency requires improvement and the understanding of their mechanism of action is incomplete. As part of our effort to investigate the structure-transfection efficiency relationships of self-assembled CL-DNA vectors, we have synthesized a new, highly charged (16+) multivalent cationic lipid, MVLBG2, with a dendritic headgroup.