[Show abstract][Hide abstract] ABSTRACT: Highly dynamic tubular structures in cells are responsible for exchanges between organelles. Compared with bacterial invasion, the most affordable and least toxic lipids were found in this study to be gentle and safe exogenous stimuli for the triggering of membrane tubules. A specific lipid system was internalized by NIH3T3 cells. Following cellular uptake, the constructed liposomes traveled towards the nucleus in aggregations and were gradually distributed into moving vesicles and tubules in the cytosol. The triggered tubules proceeded, retreated or fluctuated along the cytoskeleton and were highly dynamic, moving quickly (up to several microns per second), and breaking and fusing frequently. These elongated tubules could also fuse with one another, giving rise to polygonal membrane networks. These lipid systems, with the novel property of accelerating intracellular transport, provide a new paradigm for investigating cellular dynamics.
Full-text · Article · Nov 2015 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: In the present work, we characterize binary lipid mixtures consisting of a three-chain amino-functionalized cationic lipid (DiTT4) with different phospholipids, namely, 1,2-di-(9Z-oleoyl)-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The mixing behavior was investigated by differential scanning calorimetry (DSC). Additionally, aqueous dispersions of the binary mixtures were characterized by means of dynamic light scattering (DLS), laser Doppler electrophoresis, and transmission electron microscopy (TEM) to get further information about particle size, charge, and shape. The complex formation between different binary lipid mixtures and plasmid DNA (pDNA) was investigated by zeta-(ζ)-potential (laser Doppler electrophoresis) and DLS measurements, and the lipid/DNA complexes (lipoplexes) were screened for efficient DNA transfer (transfection) in cell culture. Finally, efficient lipid compositions were investigated with respect on serum stability. This work provides a detailed characterization of the cationic lipid mixtures as fundament for further research. Efficient gene transfer in presence of serum was demonstrated for selected lipoplexes showing their capability to be used as high-potent gene delivery vehicles.
No preview · Article · Oct 2015 · Bioconjugate Chemistry
[Show abstract][Hide abstract] ABSTRACT: The use of cationic lipids as gene delivery systems is a basic method in gene therapy. Through ongoing research, lipofection is currently the leader of non-viral vectors in clinical trials. However, in order to unleash the full potential of lipofection further intensive investigations are indispensable. In this study, various lipoplex formulations were compared regarding their ability to bind DNA. To obtain information about a possible premature release of DNA at the cell surface, heparin and chondroitin dependent lipoplex destabilization experiments were carried out. Complementary investigations in cell culture were performed to quantify DNA outside the cell. Additionally, DNase I stability was investigated. In this regard a multitude of methods, namely confocal laser scanning microscopy (CLSM), polymerase chain reaction (PCR), cell culture experiments, ethidium bromide assay, gel electrophoresis, Langmuir-isotherm experiments, infrared reflection absorption spectroscopy (IRRAS), Brewster angle microscopy (BAM), zeta-(ζ)-potential measurements, and dynamic light scattering (DLS), were applied. Although the complexation of DNA is a fundamental step, we show that the DNA release by biological agents (proteoglycans) and an unsuccessful cell attachment are major transfection limiting parameter.
No preview · Article · Oct 2015 · Journal of Controlled Release
[Show abstract][Hide abstract] ABSTRACT: The interactions of two fragments of the human antimicrobial LL-37 (LL-32 and LL-20) with lipid monolayers at the soft liquid/air interface have been characterized. To model the interaction with mammalian cell membranes, lipid monolayers composed of the zwitterionic DPPC and DOPC were used. To investigate the interaction with bacterial cell membranes, lipid monolayers of anionic DPPG and POPG were used. DPPC and DPPG exhibit a first-order phase transition from the disordered liquid to the ordered condensed state, whereas POPG and DOPC monolayers are in the fluid disordered state at all surface pressures studied. Therefore, the influence of the monolayer phase state on peptide-lipid interactions can be studied. To obtain insight into the peptide structure and their influence on phospholipid membranes, film balance measurements were coupled with surface sensitive Infrared Reflection-Absorption Spectroscopy (IRRAS). The results were compared to CD measurements in bulk.
LL-32 is more surface active and can better intercalate into lipid monolayers than LL-20. Even though LL-32 has no cell-selectivity, our results show how the peptide interacts differently with zwitterionic compared to anionic membrane models. The interaction with DPPC monolayers is based on simple intercalation of the peptides between the lipid molecules. However, the peptides bind in a two-step process to DPPG monolayers, which results in a fluidization of the lipid film. This can be related to a membrane thinning.
No preview · Article · Aug 2015 · Zeitschrift für Physikalische Chemie
[Show abstract][Hide abstract] ABSTRACT: Recent studies point out that bolaamphiphiles can be used in nonviral gene therapy. Due to their bipolar character, they may span a membrane and thus stabilize or destabilize it which could be relevant for DNA transfer across a biological membrane. Since there are only very few studies on bolaamphiphile application in DNA transfection, it is difficult to assess whether they will bring additional advantages to the class of nonviral vectors. A bolaamphiphile with a hydrophobic chain of 22 carbon atoms with trimethylammonium and hydroxyl groups at each end was synthesized (22-hydroxydocos-1-yl-N,N,N-trimethylammonium bromide). The bolaamphiphile conferred stability and lowered the zeta potential of vesicles of a cationic lipid. Confocal laser scanning microscopy and flow cytometry experiments have shown that this bolaamphiphile can transfect the green fluorescent protein plasmid in cells if mixed with a cationic lipid. It can compete with standard cationic lipids in terms of transfection but is at the same time less toxic. The potential of this class of molecules in gene delivery results from the fact that they will confer high stability to the DNA vector.
Full-text · Article · Aug 2015 · Colloid and Polymer Science
[Show abstract][Hide abstract] ABSTRACT: The layering transitions of mesomorphic poly[bis(2,2,3,3-tetrafluoropropoxy)phosphazene] induced by compression were found to result in the formation of stable multilayers directly at the air/water interface. This phenomenon is discussed with particular emphasis on its in situ structural characterization by Brewster angle microscopy, infrared spectroscopy, synchrotron grazing incidence X-ray diffraction, and X-ray reflectivity data. Compression of Langmuir monolayer is followed by layer-by-layer growth manifested by pronounced steps in the pressure/area isotherm. Grazing incidence X-ray diffraction reveals only one diffraction peak for the monolayer as well as for multilayers, which corresponds to an interchain spacing d = 12.3 Å. The in-plane correlation length ξxy reaches an impressive 345 Å for the uncompressed monolayer and 470 Å for the tetralayer, implying a certain mesoscale order similar to a quasi-long-range one. After formation of the four-layer thick film the transition into a 3D crystalline triclinic phase with a = 13.19 Å, b = 11.42 Å, c = 4.83 Å, α = 90°, β = 102°, and γ = 116° is observed.
[Show abstract][Hide abstract] ABSTRACT: Although monoacylglycerol monolayers have been used as highly informative systems, so far general information about their phase behavior and especially that of 1-monostearoyl-rac-glycerol monolayers has been missing. Complemented by the characteristics of the p-A isotherms and the mesoscopic domain topography, the present work focused on Grazing incidence X-ray diffraction (GIXD) measurements of 1-monostearoyl-rac-glycerol monolayers in the accessible temperature and surface pressure range to construct the phase diagram on the basis of reliable two-dimensional lattice structures. Examples for the mesoscopic topography of regularly and irregularly shaped domains obtainable in the first-order main phase transition region at temperatures T > 30°C are presented and discussed on the basis of line tension and geometric considerations. The GIXD results obtained over large pressure interval at 5, 10, 15 and 20 °C indicate impressively that also in the racemic 1-monostearoyl-rac-glycerol monolayer symmetry breaking occurs at low temperatures in a small pressure region where an oblique intermediate (Obl) phase between the NN and NNN tilted orthorhombic phases occurs. The temperature effect on the phase behavior of the 1-monostearoyl-rac-glycerol monolayers is demonstrated by the surface pressure - temperature diagram.
No preview · Article · Apr 2015 · The Journal of Physical Chemistry C
[Show abstract][Hide abstract] ABSTRACT: The phase behavior of an amphiphilic block copolymer based on a poly(aspartic acid) hydrophilic block and a poly(n-butyl acrylate) hydrophobic block was investigated at the air–water and air–buffer interface. The polymer forms stable monomolecular films on both subphases. At low pH, the isotherms exhibit a plateau. Compression–expansion experiments and infrared reflection absorption spectroscopy suggest that the plateau is likely due to the formation of polymer bi- or multilayers. At high pH the films remain intact upon compression and no multilayer formation is observed. Furthermore, the mineralization of calcium phosphate beneath the monolayer was studied at different pH. The pH of the subphase and thus the polymer charge strongly affects the phase behavior of the film and the mineral formation. After 4 h of mineralization at low pH, atomic force microscopy shows smooth mineral films with a low roughness. With increasing pH the mineral films become inhomogeneous and the roughness increases. Transmission electron microscopy confirms this: at low pH a few small but uniform particles form whereas particles grown at higher pH are larger and highly agglomerated. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirm the formation of calcium phosphate. The levels of mineralization are higher in samples grown at high pH.
[Show abstract][Hide abstract] ABSTRACT: A series of long-tail alkyl ethanolamine analogs containing amide-, urea-, and thiourea moieties was synthesized and the behavior of the corresponding monolayers was assessed on the Langmuir-Pockels trough combined with grazing incidence X-ray diffraction experiments and complemented by computer simulations. All compounds form stable monolayers at the soft air/water interface. The phase behavior is dominated by strong intermolecular headgroup hydrogen bond networks. While the amide analog forms well-defined monolayer structures, the stronger hydrogen bonds in the urea analogs lead to the formation of small three-dimensional crystallites already during spreading due to concentration fluctuations. The hydrogen bonds in the thiourea case form a two-dimensional network, which ruptures temporarily during compression and is recovered in a self-healing process, while in the urea clusters the hydrogen bonds form a more planar framework with gliding planes keeping the structure intact during compression. Because the thiourea analogs are able to self-heal after rupture, such compounds could have interesting properties as tight, ordered, and self-healing monolayers.
[Show abstract][Hide abstract] ABSTRACT: A series of 1,3-diamido phosphocholines was synthesized, and their potential to form stable bilayers was investigated. Large and giant unilamellar vesicles produced from these new lipids form a wide variety of faceted liposomes. Factors such as cooling rates and the careful choice of the liposome preparation method influence the formation of facets. Interdigitation was hypothesized as a main factor for the stabilization of facets and effectively monitored by small-angle X-ray scattering measurements.
[Show abstract][Hide abstract] ABSTRACT: The aggregation behavior of various zwitterionic helper phospholipids, such as DOPE, DOPC and DPPC, in combination with two new cationic lipids, namely TH4 and OH4 (second generation of malonic acid diamides) in different molar ratios was studied with regard to their physical-chemical properties. Additionally, lipoplexes prepared from these lipid mixtures were characterized with respect to the transfection efficacy using an EGFP-assay. The lipid mixtures with the fluid cationic lipid OH4 and DOPE have shown comparable transfection efficiency with Lipofectamine 2000®. Furthermore, this report demonstrates the huge influence of the helper lipid on the transfection efficiency. Thereby, alkyl chain fluidity, lipid miscibility and charge density have an important influence on an efficient gene transfer.Practical applications: Although lipofection is a topic of gene therapy since 1989, the optimal finding of an effective lipid system with new cationic lipids is still a process of trial and error. There is much unknown understanding the process of lipoplex formation as well as the release of the genetic cargo. Aim of the presented work is to find physical-chemical parameters which are connected with an effective gene transfer.
No preview · Article · Sep 2014 · European Journal of Lipid Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Peptide p160-conjugated mesoporous silica nanoparticles (MSN) were fabricated and loaded with photosensitizer hypocrellin B (HB). The results indicate that the nanocomposites have better selectivity for cancer cells and higher cytotoxicity in photodynamic therapy in vitro. The nanocomposites can be used as a novel candidate in photodynamic therapy. This may be a general and promising method to modify nanoparticles to improve their cell affinity.
Full-text · Article · Aug 2014 · Chemistry - An Asian Journal
[Show abstract][Hide abstract] ABSTRACT: Physico-chemical processes at air/liquid interfaces are of paramount importance in nature. The Langmuir
technique offers the possibility of forming a well-defined monolayer of amphiphilic molecules under study at
the air/liquid interface,with a unique control of the area permolecule and other experimental conditions. Despite being a traditional technique in Colloid and Interface science, there is an ever growing interest in Langmuir studies. Herein, recent developing fields of research currently taking advantage of the Langmuir technique are reviewed, comprising the interfacial structure of: water, biomolecules and inorganic/organic hybrids. The good state of the Langmuir technique at present and the foreseeable increase of its usage are discussed.
Full-text · Article · Jun 2014 · Current Opinion in Colloid & Interface Science
[Show abstract][Hide abstract] ABSTRACT: Carbon nanostructures that feature two-dimensional extended nanosheets are important components for technological applications such as high-performance composites, lithium-ion storage, photovoltaics and nanoelectronics. Chemical functionalization would render such structures better processable and more suited for tailored applications, but typically this is precluded by the high temperatures needed to prepare the nanosheets. Here, we report direct access to functional carbon nanosheets of uniform thickness at room temperature. We used amphiphiles that contain hexayne segments as metastable carbon precursors and self-assembled these into ordered monolayers at the air/water interface. Subsequent carbonization by ultraviolet irradiation in ambient conditions resulted in the quantitative carbonization of the hexayne sublayer. Carbon nanosheets prepared in this way retained their surface functionalization and featured an sp(2)-rich amorphous carbon structure comparable to that usually obtained on annealing above 800 °C. Moreover, they exhibited a molecularly defined thickness of 1.9 nm, were mechanically self-supporting over several micrometres and had macroscopic lateral dimensions on the order of centimetres.
[Show abstract][Hide abstract] ABSTRACT: Gibbs or Langmuir monolayers formed at the soft air/liquid interface are easy to handle and versatile model systems for material and life sciences. The phase state of the monolayers can be modified by lateral compression of the film while the layer structural changes are monitored by highly sensitive surface characterization techniques. The use of high brilliant synchrotron light sources for X-ray experiments is essential for the monolayer research. The present review highlights the recent achievements recorded in the monolayer field with a special emphasis on different synchrotron based X-ray characterizing methods as: grazing incidence X-ray diffraction, X-ray reflectivity and total reflection X-ray fluorescence. Some examples of single-chain surfactants, special sugar lipids, and semifluorinated compounds are given. Additionally, thin layers formed by peptides, polymers or nanoparticles are highlighted.
No preview · Article · Jun 2014 · Current Opinion in Colloid & Interface Science
[Show abstract][Hide abstract] ABSTRACT: The use of highly brilliant synchrotron light sources in the middle of the 1980s for X-ray diffraction has revolutionized the research of condensed monolayers. Since then, monolayers gained popularity as convenient quasi two-dimensional model systems widely used in biophysics and material science. This review focuses on structures observed in one-component phospholipid monolayers used as simplified two-dimensional models of biological membranes. In a monolayer system the phase transitions can be easily triggered at constant temperature by increasing the packing density of the lipids by compression. Simultaneously the monolayer structure changes are followed in situ by grazing incidence X-ray diffraction. Competing interactions between the different parts of the molecule are responsible for the different monolayer structures. These forces can be modified by chemical variations of the hydrophobic chain region, of the hydrophilic head group region or of the interfacial region between chains and head groups. Modifications of monolayer structures triggered by changes of the chemical structure of double-chain phospholipids are highlighted in this paper.
No preview · Article · May 2014 · Advances in Colloid and Interface Science