Alleviation of genotoxic effects of cyclophosphamide using encapsulation into liposomes in the absence or presence of vitamin C.

Tohamy AA, Abdel Azeem AA, Shafaa MW, Mahmoud WS

Gen Physiol Biophys. 2012 Mar;31(1):85-91. doi: 10.4149/gpb_2012_009.

Cyclophosphamide (CP) is a widely used anticancer and immunosuppressant that induces oxidative stress. To ameliorate the side effects resulted from CP treatment, liposomes were tested as an efficient drug delivery system with or without vitamin C as an antioxidant. CP resulted in clastogenic and cytotoxic effects that significantly increased for the total chromosomal aberrations as well as the numerical ones in the CP group (150.8 and 6, respectively) than the control group (6.6 and 0.0) as mean values at p < 0.05. Micronucleus assay showed a significant increased micronucleated polychromatic erythrocytes percentage (MNPCEs% = 11.7%) and a significant decrease of polychromatic to normochromatic erythrocytes ratio (0.551) when compared to the group treated with liposomised CP and vitamin C (3.44%; 0.795, respectively) at p < 0.05. Also, the total glutathione S-transferase activity as a body antioxidant enzyme was decreased from 52.2 in the control to 16.09 nmol/min/mg protein in CP group at p < 0.05, while the highly significant amelioration results were observed in the liposomised vitamin C and CP group (40.88 nmol/min/mg protein). Our findings support the potential use of CP in a liposomal formulation doped with vitamin C to diminish the potential side effects of the agent.

Thermally induced conformational changes in horseradish peroxidase

David G. Pina1 et al.
Eur. J. Biochem. 268, 120-126 (2001), FEBS 2001

REACTIVE OXYGEN SPECIES: Metabolism, Oxidative Stress, and Signal Transduction

Klaus Apel and Heribert Hirt

Annu. Rev. Plant Biol. 2004. 55:373–99

Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Considering recent ROS-induced genomewide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.

Free radicals and antioxidants in normal physiological functions and human disease

Marian Valko, Dieter Leibfritz, Jan Moncol, Mark T.D. Cronin, Milan Mazur, Joshua Telser

The International Journal of Biochemistry & Cell Biology 39 (2007) 44–84

Reactive oxygen species (ROS) and reactive nitrogen species (RNS, e.g. nitric oxide, NO•) are well recognised for playing a dual role as both deleterious and beneficial species. ROS and RNS are normally generated by tightly regulated enzymes, such as NO synthase (NOS) and NAD(P)H oxidase isoforms, respectively. Overproduction of ROS (arising either from mitochondrial electron transport chain or excessive stimulation of NAD(P)H) results in oxidative stress, a deleterious process that can be an important mediator of damage to cell structures, including lipids and membranes, proteins, andDNA. In contrast, beneficial effects ofROS/RNS (e.g. superoxide radical and nitric oxide) occur at low/moderate concentrations and involve physiological roles in cellular responses to noxia, as for example in defence against infectious agents, in the function of a number of cellular signalling pathways, and the induction of a mitogenic response. Ironically, various ROS-mediated actions in fact protect cells against ROS-induced oxidative stress and re-establish or maintain “redox balance” termed also “redox homeostasis”. The “two-faced” character of ROS is clearly substantiated. For example, a growing body of evidence shows that ROS within cells act as secondary messengers in intracellular signalling cascades which induce and maintain the oncogenic phenotype of cancer cells, however, ROS can also induce cellular senescence and apoptosis and can therefore function as anti-tumourigenic species. This review will describe the: (i) chemistry and biochemistry of ROS/RNS and sources of free radical generation; (ii) damage to DNA, to proteins, and to lipids by free radicals; (iii) role of antioxidants (e.g. glutathione) in the maintenance of cellular “redox homeostasis”; (iv) overview of ROS-induced signaling pathways; (v) role of ROS in redox regulation of normal physiological functions, as well as (vi) role of ROS in pathophysiological implications of altered redox regulation (human diseases and ageing). Attention is focussed on the ROS/RNS-linked pathogenesis of cancer, cardiovascular disease, atherosclerosis, hypertension, ischemia/reperfusion injury, diabetes mellitus, neurodegenerative diseases (Alzheimer’s disease and Parkinson’s disease), rheumatoid arthritis, and ageing. Topics of current debate are also reviewed such as the question whether excessive formation of free radicals is a primary cause or a downstream consequence of tissue injury.

Lipopolysaccharide Identification with Functionalized Polydiacetylene Liposome Sensors

Marianne Rangin and Amit Basu
J. AM. CHEM. SOC. 2004, 126, 5038-50

Polydiacetylene Liposome Microarray Toward Influenza A Virus Detection: Effect of Target Size on Turn-On Signaling

1. Sungbaek Seo¹, 
2. Jiseok Lee¹, 
3. Eun-Jin Choi², 
4. Eun-Ju Kim², 
5. Jae-Young Song²,
6. Jinsang Kim^3,*

Volume 34, Issue 9, pages 743–748, May 14, 2013

Target size effect on the sensory signaling intensity of polydiacetylene (PDA) liposome microarrays was systematically investigated. Influenza A virus M1 peptide and M1 antibody were selected as a probe–target pair. While red fluorescence from the PDA liposome microarrays was observed when the larger M1 antibody was used as a target, when the same M1 antibody was used as a probe to detect the smaller M1 peptide sensory signal did not appear. The results reveal that the intensity of the PDA sensory signal is mainly related to the steric repulsion between probe–target complexes not the strength of the probe–target binding force. Based on this finding, we devised a PDA sensory system that directly detects influenza A whole virus as a larger target, and confirmed the target size effect on the signaling efficiency of PDA.

A Light-Actuated Nanovalve Derived from a Channel Protein

Armagan Kocer, Martin Walko, Wim Meijberg, Ben L. Feringa

29 JULY 2005 VOL 309 SCIENCE, pp.755

Toward the realization of nanoscale device control, we report a molecular valve embedded in a membrane that can be opened by illumination with longwavelength ultraviolet (366 nanometers) light and then resealed by visible irradiation. The valve consists of a channel protein, the mechanosensitive channel of large conductance (MscL) from Escherichia coli, modified by attachment of synthetic compounds that undergo light-induced charge separation to reversibly open and close a 3-nanometer pore. The system is compatible with a classical encapsulation system, the liposome, and external photochemical control over transport through the channel is achieved.

Shape and Size of a Nonionic Surfactant Micelle. Triton X-100 in Aqueous Solution

H. Hasko Paradies

J. Phys. Chem. 1980, 84, 599-607

Phase Separation of Polymerized Mixed Liposomes: Analysis of Release Behavior of Entrapped Molecules with Skeletonization

Shinji Takeoka, Hiromi Sakai, Hiroyuki Ohno,+ and Eishun Tsuchida'

Macromolecules 1991,24, 1279-1283

The mixed liposomes, composed of a polymerizable lipid, 1,2-bis(2,4-octadecadienoyl)-snglycero-3-phosphorylcholine(D ODPC), and nonpolymerizable membrane constituents, DPPC, cholesterol, and sodium didodecyl phosphate, were prepared by an extrusion method. After polymerization, onpolymerizable constituents were removed to obtain the polymerized framework of the liposome (the skeletonized liposome). The release of small molecules from the skeletonized liposomes through resulting holes was analyzed. A 5(6)-carboxyfluorescein (CF) and saccharides with various molecular weights were applied as release molecules. The molecular weight of dextran, whose retention ratio in the skeletonized liposomes is 5096, relates to the apparent size of the holes, i.e., the apparent domain size of the phase separation of a polymerized mixed liposome. The size of the holes increases with an increase in the mole fraction of nonpolymerizable lipids. This also depends on the polymerization temperature and the structure of nonpolymerizable lipids.

Thermodynamics of micelle formation and surface chemical behavior of p-tert-Octylphenoxyethylene Ether (TritonX-100) in Aqueous Medium

J. Surface Sci. Technol., Vol 17, no.1-2, pp.1-15, 2001

LIPOSOMES OF CONTROLLABLE SIZE IN THE RANGE OF 40 TO 180 nm BY DEFINED DIALYSIS OF LIPID/DETERGENT MIXED MICELLES

OTMAR ZUMBUEHL and HANS GEORG WEDER

Biochimica et Biophysica Acta, 640 (1981) 252-262

Liposomes, in the size range of 40--180 nm, are formed when lipid and additives are solubllized with detergent, yielding defined mixed micelles, and the detergent is subsequently removed by controlled dialysis. Their most important properties are that they are indeed unilamellar with usefully large encapsulated volumes and are homogeneous in size. Liposomes have been formed from both natural and synthetic phospholipids with cholesterol and charged molecules added. This relatively simple technique may be particularly useful for encapsulating drugs, enzymes and other macromolecules and in studies of reconstitution of membrane proteins.

Direct formation of mixed micelles in the solubilization of phospholipid liposomes by Triton X-100

FEBS Letters 426 (1998) 314-318

The vesicle to micelle transition which results in the interaction of the Triton X-100 surfactant with phosphatidylcholine vesicles was studied by means of dynamic light scattering (at different reading angles) and by freeze-fracture electron microscopy techniques. Vesicle solubilization was produced by the direct formation of mixed micelles without the formation of complex intermediate aggregates. Thus, vesicle to micelle transformation was mainly governed by the progressive formation of mixed micelles within the bilayer. A subsequent separation of these micelles from the liposome surface (vesicle perforation by the formation of surfactant-stabilized holes on the vesicle surface) led to a complete solubilization of liposomes.

Temperature Dependence of Triton X-100 Micelle Size and Hydration

Kiril Streletzky and George D. J. Phillies

Langmuir 1996,11, 42-47

Quasi-elastic light scattering spectroscopy was used to measure the mutual diffusion coefficient, D of Triton X-100 micelles in aqueous solution and the translational diffusion coefficient, D, of mesoscopic probes in the same solutions. We apply conventional hydrodynamic treatments of diffision under the assumption that Triton X-100 minimal micelles are adequately represented as hard spheres. Dm and D, measured at a series of surfactant concentrations are used to infer the micelle radius, am, aggregation number, N, and degree of hydration, 6, for temperatures 10 5 T 5 50 "C. As T is increased toward the cloud point, am and N increase, the increase in N being especially dramatic above 40 "C, 6 at first increases but then tends to saturate with increasing T.

The Size, Shape, and Hydration of Nonionic Surfactant Micelles. Triton X-100

Robert J. Robson and Edward A. Dennis
The Journal of Physical Chemistry, Vol. 81, No. 11, 1977

Calculations of the size, shape, and hydration of micelles composed of the nonionic surfactant Triton X-100 were performed based on molecular weight and intrinsic viscosity data. Geometrical considerations show that if the hydrophobic core as well as the whole micelle is spherical, then its structure cannot contain the distinctpolar and apolar regions that are classically assumed for micelles. On the other hand, ellipsoids of revolution would be consistent with a classical micellar structure and an oblate rather than a prolate ellipsoid would be most consistent with intrinsic viscosity measurements and volume calculations.

Thermodynamic and Structural Studies of Triton X-100 Micelles in Ethylene Glycol-Water Mixed Solvents

C. Carnero Ruiz, J. A. Molina-Bolfvar, and J. Aguiar

Langmuir 2001, 17, 6831-6840

Micellar properties of p-tert-octyl-phenoxy (9.5) polyethylene ether (Triton X-100) in aqueous mixtures of ethylene glycol (EG) were determined using such techniques as surface tension, static and dynamic light scattering, and fluorescence spectroscopy. Thermodynamics of micellization was obtained from the temperature dependence of critical micelle concentration values. The differences in the Gibbs energies of micellization of Triton X-100 between water and binary solvent systems were calculated to evaluate the influence of cosolvent on the micellization process. From this study, it can be concluded that the structurebreaking ability of EG and its interaction with the oxyethylene groups of the surfactant are dominating factors in the micellization process. Thermodynamics of adsorption of the solution-air interface was also evaluated. It was found that the surface activity of the surfactant decreases slightly with increasing concentration of EG at a given temperature. By a combination of static and dynamic light scattering measurements, a reduction of the micelle size was observed, mainly due to a decrease of the micellar aggregation number, whereas the micellar solvation was not substantially modified in magnitude with EG addition. However, the change of the surface area per headgroup of the surfactant suggested an alteration in the nature of its solvation layer, produced probably by a certain participation of cosolvent in the micellar solvation layer. This point was corroborated from the fluorescence polarization studies of several luminescent probes, including coumarin 6, merocyanine 540, and rhodamine B. These experiments revealed a slight increase of the micellar microviscosity. Finally, the proposed mechanism was also supported by the increase observed in the cloud point of Triton X-100, induced by the EG addition.

Protection and Promotion of UV Radiation-Induced Liposome Leakage via DNA-Directed Assembly with Gold Nanoparticles

Neeshma Dave and Juewen Liu

Adv. Mater. 2011, 23, 3182–3186

Mind over myocardium

Shailaja Neelakantan
S16 | NATURE | VOL 493 | 31 JANUARY 2013
Mental factors beyond stress trigger physiological changes that can cause heart disease.

A Promising Drug Controlled-Release System Based on Diacetylene/ Phospholipid Polymerized Vesicles

Caixin Guo, Shaoqin Liu, Chang Jiang, Wenyuan Li, and Zhifei Dai
Langmuir 2009, 25(22), 13114–13119

A novel polymerized vesicular carrier loaded with paclitaxel was developed by introducing the ultraviolet (UV) crosslinkable 10,12-pentacosadiynoic acid (PCDA) into bilayered phospholipid vesicles with the purpose of improving the physicochemical stability as well as the controlled-release property of liposomes. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) results revealed the enhanced stability of PCDA-polymerized vesicles against Triton X-100. In particular, alteration in PCDA/phospholipids ratios and UV-irradiation time can modulate the cumulative paclitaxel released. For instance, vesicles composed of phospholipids only released 98.0(2.1% of paclitaxel within 24 h. Over the same time period, 72.0 ( 5.8%, 43.9 ( 6.5%, and 20.1 ( 5.4% of paclitaxel was released from polymerized PCDA/phospholipid vesicles at molar ratios of 1:3, 1:1, and 3:1, respectively. Likewise, by increasing the UV-irradiation time from 20 to 40 min, the cumulative release of paclitaxel from polymerized  CDA/phospholipid vesicles at molar ratio of 1:1 decreased from 90.5 ( 3.7% to 37.6 ( 2.3% over a time period of experimental observation of 24 h. The influences of vesicle composition (i.e., PCDA/phospholipids ratio) and UV-irradiation time on the release rates of paclitaxel were further examined by finite element (FE) analyzed using Abaqus. Our results demonstrate that novel polymerized vesicles capable of regulating the release of anticancer drugs such as paclitaxel have been developed.

Liposome−Quantum Dot Complexes Enable Multiplexed Detection of Attomolar DNAs without Target Amplification

Juan Zhou, Qiang-xin Wang, and Chun-yang Zhang
J. Am. Chem. Soc. 2013, 135, 2056−2059

Sensitive detection of DNA usually relies on target amplification approaches such as polymerase chain reaction and rolling circle amplification. Here we describe a new approach for sensitive detection of lowabundance DNA using liposome−quantum dot (QD) complexes and single-particle detection techniques. This assay allows for detection of single-stranded DNA at attomolar concentrations without the involvement of target amplification. Importantly, this strategy can be employed for simultaneous detection of multiple DNA targets.

Interaction of Ionic Surfactants with Cornea-Mimicking Anionic Liposomes

Chhavi Gupta, Andrew K. Daechsel, and Anuj Chauhan

Langmuir 2011, 27, 10840–10846

The interaction of surface-active molecules with lipid bilayers is ubiquitous both in biological systems and also in several technological applications.Here we explore the interaction of ionic surfactants with liposomes whose composition mimics the ocular epithelia. In this study, liposomes with a composition mimicking ocular epithelia are loaded with calcein dye above the self-quenching concentration. The liposomes are then exposed to surfactants, and the rate of dye leaked from the liposomes due to the interaction of surfactants is measured. Both cationic and anionic surfactants at various concentrations and ionic strengths are explored. Results show that the liposome bilayer permeability to the dye increases on exposure to the surfactants, leading to the release of the dye trapped in the core. However, the dye release stops after a finite time, suggesting a transient increase in permeability followed by healing. The leakage profiles exhibit two different timescales for the cationic surfactant but only one timescale for the anionic surfactant. The total dye leakage increases with surfactant concentration, and at a given concentration, the dye leakage is significantly higher for the cationic surfactants. The timescale for the healing decreases with increasing surfactant concentration, and increasing ionic strength increases the dye leakage for the anionic surfactant. These results show that the surfactant binding to the lipid bilayer increases the permeability while the bilayers heal likely because of the surfactant jump from the outer to the inner leaflet and/or rearrangement into tighter aggregates.