The Role of Temperature and Lipid Charge on Intake/Uptake of Cationic Gold Nanoparticles into Lipid Bilayers

Understanding the molecular mechanisms governing nanoparticle-membrane interactions is of prime importance for drug delivery and biomedical applications. Neutron reflectometry (NR) experiments are combined with atomistic and coarse-grained molecular dynamics (MD) simulations to study the interaction between cationic gold nanoparticles (AuNPs) and model lipid membranes composed of a mixture of zwitterionic di-stearoyl-phosphatidylcholine (DSPC) and anionic di-stearoyl-phosphatidylglycerol (DSPG). MD simulations show that the interaction between AuNPs and a pure DSPC lipid bilayer is modulated by a free energy barrier. This can be overcome by increasing temperature, which promotes an irreversible AuNP incorporation into the lipid bilayer. NR experiments confirm the encapsulation of the AuNPs within the lipid bilayer at temperatures around 55 °C. In contrast, the AuNP adsorption is weak and impaired by heating for a DSPC-DSPG (3:1) lipid bilayer. These results demonstrate that both the lipid charge and the temperature play pivotal roles in AuNP-membrane interactions. Furthermore, NR experiments indicate that the (negative) DSPG lipids are associated with lipid extraction upon AuNP adsorption, which is confirmed by coarse-grained MD simulations as a lipid-crawling effect driving further AuNP aggregation. Overall, the obtained detailed molecular view of the interaction mechanisms sheds light on AuNP incorporation and membrane destabilization.

The effect of major cations on the toxicity of cadmium to Folsomia candida in a sand-solution medium analyzed by biotic ligand modeling

The aim of this study was to assess the effect of major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺, and H⁺) on cadmium toxicity to the springtail Folsomia candida. Survival of the animals was determined after seven days exposure to different cadmium concentrations in an inert sand-solution medium, in different experimental setups with modification of the cation concentrations. Among the cations tested, Ca²⁺ and Mg²⁺ had protective effects on the toxicity of cadmium to the springtails while Na⁺, K⁺, and H⁺ showed less competition with free cadmium ions for binding to the uptake sites of the collembolans. Toxicity predicted with a biotic ligand model agreed well with the observed values. Calculated conditional binding constants and the fraction of biotic ligands occupied by cadmium to show 50% effects were similar to values reported in the literature. The results emphasize the important role of solution chemistry in determining metal toxicity to soil invertebrates.

Inhibition of glioma growth by a GOLPH3 siRNA-loaded cationic liposomes

PURPOSE

GOLPH3 has been shown to be involved in glioma proliferation. In this study, we aimed to demonstrate that GOLPH3 can serve as a target for glioma gene therapy.

METHODS

During the experiment, cationic liposomes with angiopep-2 (A2-CL) were used to deliver siGOLPH3 crossing the blood-brain barrier and reaching the glioma.

RESULTS

At the cellular level, the A2-CL/siGOLPH3 could silence GOLPH3 and then effectively inhibited the proliferation of cells. In vivo experiments, using U87-GFP-Luci-bearing BALB/c mouse models, we demonstrated that A2-CL could deliver GOLPH3-siRNA specifically to glioma and effectively inhibit glioma growth.

CONCLUSIONS

This study shows that GOLPH3 has great potential as a target for the gene therapy of glioma and is of great value in precise medical applications.

Synthesis and Preclinical Characterization of a Cationic Iodinated Imaging Contrast Agent (CA4+) and Its Use for Quantitative Computed Tomography of Ex Vivo Human Hip Cartilage

Contrast agents that go beyond qualitative visualization and enable quantitative assessments of functional tissue performance represent the next generation of clinically useful imaging tools. An optimized and efficient large-scale synthesis of a cationic iodinated contrast agent (CA4+) is described for imaging articular cartilage. Contrast-enhanced CT (CECT) using CA4+ reveals significantly greater agent uptake of CA4+ in articular cartilage compared to that of similar anionic or nonionic agents, and CA4+ uptake follows Donnan equilibrium theory. The CA4+ CECT attenuation obtained from imaging ex vivo human hip cartilage correlates with the glycosaminoglycan content, equilibrium modulus, and coefficient of friction, which are key indicators of cartilage functional performance and osteoarthritis stage. Finally, preliminary toxicity studies in a rat model show no adverse events, and a pharmacokinetics study documents a peak plasma concentration 30 min after dosing, with the agent no longer present in vivo at 96 h via excretion in the urine.

A comparative study on the effect of Curcumin and Chlorin-p6 on the transport of the LDS cation across a negatively charged POPG bilayer: Effect of pH

We report the use of interface selective Second Harmonic generation technique to investigate the transport of the LDS cation across POPG liposomes in the pH range of 4.0 to 8.0 in the presence and absence of two amphiphilic drugs, Curcumin and Chlorin-p₆ (Cp₆). Our results show that bilayer permeability of liposomes is significantly affected by the presence of the drugs and pH of the medium as evidenced by significant changes in the transport kinetics of the LDS. Studies carried out in the pH range 4.0-8.0 show that while Cp₆ significantly enhanced the transport of LDS at pH4.0, the transport of the cation was seen to increase with increasing pH, with maximum effect at pH7.4 for Curcumin. The pH dependent bilayer localization of both the drugs was investigated by conducting steady state FRET studies using DPH labeled lipids as donors. The FRET results and the relative population of the various ionic/nonionic species of the drugs at different pH suggest that distance dependent interaction between the various ionic species of the drugs and polar head groups of the lipid is responsible for the observed pH dependence enhancement of the drug induced membrane permeability. Another interesting observation was that the stability of Curcumin in presence of POPG liposomes was observed to degrade significantly near physiological pH (7.4 and 8.0). Although this degradation did not affect the liposome integrity, interestingly this was observed to enhance the transport of the LDS cation across the bilayer. That the degradation products of Curcumin are equally effective as the drug itself in enhancing the membrane permeability lends additional support to the current opinion that the bioactive degradation products of the drug may have a significant contribution to its observed pharmacological effects.

Cationic liposome-nucleic acid nanoparticle assemblies with applications in gene delivery and gene silencing

Cationic liposomes (CLs) are synthetic carriers of nucleic acids in gene delivery and gene silencing therapeutics. The introduction will describe the structures of distinct liquid crystalline phases of CL-nucleic acid complexes, which were revealed in earlier synchrotron small-angle X-ray scattering experiments. When mixed with plasmid DNA, CLs containing lipids with distinct shapes spontaneously undergo topological transitions into self-assembled lamellar, inverse hexagonal, and hexagonal CL-DNA phases. CLs containing cubic phase lipids are observed to readily mix with short interfering RNA (siRNA) molecules creating double gyroid CL-siRNA phases for gene silencing. Custom synthesis of multivalent lipids and a range of novel polyethylene glycol (PEG)-lipids with attached targeting ligands and hydrolysable moieties have led to functionalized equilibrium nanoparticles (NPs) optimized for cell targeting, uptake or endosomal escape. Very recent experiments are described with surface-functionalized PEGylated CL-DNA NPs, including fluorescence microscopy colocalization with members of the Rab family of GTPases, which directly reveal interactions with cell membranes and NP pathways. In vitro optimization of CL-DNA and CL-siRNA NPs with relevant primary cancer cells is expected to impact nucleic acid therapeutics in vivo. This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

Synthesis, binding, nuclease resistance and cellular uptake properties of 2'-O-acetalester-modified oligonucleotides containing cationic groups

We report on the synthesis and properties of oligonucleotides (ONs) with 2'-O-acetalester modifications containing cationic side chains in a prodrug-like approach. In the aim to improve cell penetration and nuclease resistance, various different amino- or guanidino-acetalester were grafted to 2'-OH of uridine and the corresponding phosphoramidites were incorporated into ONs. Introduction of 2'-O-(2-aminomethyl-2-ethyl)butyryloxymethyl (AMEBuOM) modification into 2'-OMe ONs leads to high resistance towards enzymatic degradation and to destabilization of duplexes with complementary RNA strand. Spontaneous uptake experiments of a twelve-mer containing ten 2'-O-AMEBuOM-U units into A673 cells showed moderate internalization of ON within the cells whereas substantial internalization of the corresponding lipophilic 2'-O-pivaloyloxymethyl ON was observed for the first time.

Ultrasound-Triggered Phase-Transition Cationic Nanodroplets for Enhanced Gene Delivery

Ultrasound as an external stimulus for enhanced gene transfection represents a safe, noninvasive, cost-effective delivery strategy for gene therapy. Herein, we have developed an ultrasound-triggered phase-transition cationic nanodroplet based on a novel perfluorinated amphiphilic poly(amino acid), which could simultaneously load perfluoropentane (PFP) and nucleic acids. The heptadecafluoroundecylamine (C11F17-NH2) was chosen to initiate β-benzyl-L-aspartate N-carboxyanhydride (BLA-NCA) ring-opening polymerization to prepare C11F17-poly(β-benzyl-L-aspartate) (C11F17-PBLA). Subsequently, C11F17-poly{N-[N'-(2-aminoethyl)]aspartamide} [C11F17-PAsp(DET)] was synthesized by aminolysis reaction of C11F17-PBLA with diethylenetriamine (DET). PFP/pDNA-loaded nanodroplets PFP-TNDs [PFP/C11F17-PAsp(DET)/LucDNA/γ-PGA or poly(glutamic acid)-g-MeO-poly(ethylene glycol) (PGA-g-mPEG) ternary nanodroplets] were primarily formulated by an oil/water emulsification method, followed by surface modification with PGA-g-mPEG. The average diameter of PFP-TNDs ranged from 300 to 400 nm, and transmission electron microscopy images showed that the nanodroplets were nearly spherical in shape. The ζ potential of the nanodroplets dramatically decreased from +54.3 to +15.3 mV after modification with PGA-g-mPEG, resulting in a significant increase of the stability of the nanodroplets in the serum-containing condition. With ultrasound irradiation, the gene transfection efficiency was enhanced 14-fold on HepG2 cells, and ultrasound-triggered phase-transition cationic nanodroplets also displayed a good ultrasound contrast effect. These results suggest that the PFP/DNA-loaded phase-transition cationic nanodroplets can be utilized as efficient theranostic agents for targeting gene delivery.

Comparison of bioconcentration of ionic silver and silver nanoparticles in zebrafish eleutheroembryos

The production of silver nanoparticles has reached nowadays high levels. Bioconcentration studies, information on persistence and toxicity are fundamental to assess their global risk and thus necessary to establish legislations regarding their use. Previous studies on silver nanoparticle toxicity have determined a clear correlation between their chemical stability and toxicity. In this work, experimental conditions able to assure silver nanoparticles stability have been optimized. Then, zebrafish (Danio rerio) eleutheroembryos were exposed to ionic silver and to Ag NPs for comparison purposes. A protocol alternative to the OECD 305 technical guideline was used. To determine silver concentration in both the eleutheroembryos and the exposure media, an analytical method consisting in ultrasound assisted extraction, followed by inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry, was developed. Then, bioconcentration factors were calculated. The results revealed that ionic silver was more accumulative for zebrafish eleutheroembryos than nanoparticles at the levels tested.

Preparation of a cationic nanoemulsome for intratumoral drug delivery and its enhancing effect on cellular uptake in vitro

To develop an appropriate carrier for intratumoral drug delivery, cetyltrimethylammonium bromide (CTAB) modified nanoemulsome (CTAB-NES) was designed and prepared by solvent evaporation method. Coumarin-6 was chosen as the fluorescent probe and the conventional nanoemulsome (NES) without CTAB modification served as a control. The results demonstrated that CTAB-NES had a smaller particle size of 71.9 +/- 4.32 nm, considerate positive zeta potential of +48.7 +/- 0.2 mV, preferably entrapment efficiency of 97.483 +/- 0.693% and the release of coumarin-6 in 24 h was little. The in vitro cytotoxicity of CTAB-NES to the CHO cells and MCF-7 cells increased consistently with concentrations and was higher than that of NES, especially to the cancer cells. Both the fluorescence microscopy images and HPLC assay verified that the cellular uptake of CTAB-NES in MCF-7 cells was much higher than that of NES, and the uptake was time-, concentration- and temperature- dependent. The uptake mechanism results demonstrated that the internalization of CTAB-NES and NES involved clathrin- and caveolae-mediated endocytosis while macropinocytosis only influenced the uptake of CTAB-NES in MCF-7 cells for CTAB could mediate adsorptive pinocytosis. Thus, CTAB-NES with high positive charge and good intracellular uptake ability could be a promising drug carrier for intratumoral drug delivery.

Role of the Ca-pectates on the accumulation of heavy metals in the root apoplasm

In order to better understand the processes that regulate the accumulation in the apoplasm of heavy metals and their mobilization by the plant metabolites it is essential to study the mechanisms that regulate the interactions between metal ions and pectins. In such a context, the sorption of Cd(II), Zn(II), Cu(II) and Pb(II) from single and multi-metal solutions, by a Ca-polygalacturonate gel with a degree of esterification of 18.0 (PGAM(1)) and 65.5% (PGAM(2)) was studied in the 3.0-6.0 pH range in the presence of CaCl(2) 2.5mM. The sorption of Cr(III) from single metal solution was also considered. The results show that the amount of each metal ion sorbed increases with increasing the initial metal ion concentration and pH. The data from the single metal solution tests show that at pH 6.0 the affinity of the metal ions towards the PGAM(1) matrix follows the order: Cr(III)>Cu(II)≅Pb(II)≫Zn(II)≅Cd(II). The simultaneous sorption of the bivalent metal ions by the PGAM(1) gels indicates that Pb(II) is selectively sorbed. The FT-IR spectra show that the carboxylate groups are mainly responsible for the metal ion coordination. The ability of PGAM(2) to accumulate Cr(III), Cu(II), and Pb(II) was lower than that found in the PGAM(1) systems whereas the sorption of Zn(II) and Cd(II) was negligible.

Electronic absorption spectroscopy of polycyclic aromatic hydrocarbons (PAHs) radical cations generated in oleum: a superacid medium

Oleum (fuming sulphuric acid), a well known superacid, was used as medium for the generation of the radical cation of a series of selected PAHs. The resulting radical cation spectra were studied by electronic absorption spectroscopy. Not only common PAHs like naphthalene, anthracene, tetracene, pentacene, perylene, pyrene, benzo[a]pyrene, phenanthrene and picene were studied but also the less common and very large PAHs relevant also for the astrochemical research, like coronene, hexabenzocoronene, quaterrylene, dicoronylene and a coronene oligomer. A correlation between the first ionization potential (IP1) of the PAHs studied and the energy to the so-called A-type band of the radical cations observed in oleum has led to the equation IP1=1.30EA+4.39 (in eV) which permits to estimate the energy of the PAHs radical cation transition (EA) in the VIS-NIR knowing the relative ionization potential or vice versa.

Characterization of endocytosis and exocytosis of cationic nanoparticles in airway epithelium cells

A major challenge of drug delivery using colloids via the airway is to understand the mechanism implied in their interactions with epithelial cells. The purpose of this work was to characterize the process of endocytosis and exocytosis of cationic nanoparticles (NPs) made of maltodextrin which were developed as a delivery system for antigens in vaccine applications. Confocal microscopy demonstrated that these NP are rapidly endocytosed after as little as 3 min incubation, and that the endocytosis was also faster than NP binding since most of the NPs were found in the middle of the cells around the nuclei. A saturation limit was observed after a 40 min incubation, probably due to an equilibrium becoming established between endocytosis and exocytosis. Endocytosis was dramatically reduced at 4 degrees C compared with 37 degrees C, or by NaN(3) treatment, both results suggesting an energy dependent process. Protamine pretreatment of the cells inhibited NPs uptake and we found that clathrin pathway is implied in their endocytosis. Cholesterol depletion increased NP uptake by 300% and this phenomenon was explained by the fact that cholesterol depletion totally blocked NP exocytosis. These results suggest that these cationic NPs interact with anionic sites, are quickly endocytosed via the clathrin pathway and that their exocytosis is cholesterol dependent, and are similar to those obtained in other studies with viruses such as influenza.

Tuning payload delivery in tumour cylindroids using gold nanoparticles

Nanoparticles have great potential as controllable drug delivery vehicles because of their size and modular functionality. Timing and location are important parameters when optimizing nanoparticles for delivery of chemotherapeutics. Here, we show that gold nanoparticles carrying either fluorescein or doxorubicin molecules move and localize differently in an in vitro three-dimensional model of tumour tissue, depending on whether the nanoparticles are positively or negatively charged. Fluorescence microscopy and mathematical modelling show that uptake, not diffusion, is the dominant mechanism in particle delivery. Our results indicate that positive particles may be more effective for drug delivery because they are taken up to a greater extent by proliferating cells. Negative particles, which diffuse more quickly, may perform better when delivering drugs deep into tissues. An understanding of how surface charge can control tissue penetration and drug release may overcome some of the current limitations in drug delivery.

Direct observation of cations and polynucleotides explains polyion adsorption to like-charged surfaces

We show an experimental approach for directly observing the condensation of polynucleotides and their electrolyte counterions at a liquid/solid interface. X-ray standing waves (XSW) generated by Bragg diffraction from a d = 20 nm Si/Mo multilayer substrate are used to measure the distinct distribution profiles of the polyanions and simple cations along the surface normal direction with subnanometer resolution. The 1D spatial sensitivity of this approach is enhanced by observing the XSW induced fluorescence modulations over multiple orders of Bragg peaks. We study the interesting divalent cation driven adsorption of anionic polynucleotides to anionic surfaces by exposing a hydroxyl-terminated silica surface to an aqueous solution with ZnCl2 and mercurated poly-uridylic acid (a synthetic RNA molecule). The in situ long-period XSW measurements are used to follow the evolution of both the Zn and Hg distribution profiles during the adsorption process. The conditions and physical mechanisms that govern the observed divalent cation adsorption and subsequent polynucleotide adsorption to an anionic surface are explained by a thermodynamic model that incorporates nonlinear electrostatic effects.

Targeting antioxidants to mitochondria by conjugation to lipophilic cations

Mitochondrial oxidative damage contributes to a range of degenerative diseases. Consequently, the selective inhibition of mitochondrial oxidative damage is a promising therapeutic strategy. One way to do this is to invent antioxidants that are selectively accumulated into mitochondria within patients. Such mitochondria-targeted antioxidants have been developed by conjugating the lipophilic triphenylphosphonium cation to an antioxidant moiety, such as ubiquinol or alpha-tocopherol. These compounds pass easily through all biological membranes, including the blood-brain barrier, and into muscle cells and thus reach those tissues most affected by mitochondrial oxidative damage. Furthermore, because of their positive charge they are accumulated several-hundredfold within mitochondria driven by the membrane potential, enhancing the protection of mitochondria from oxidative damage. These compounds protect mitochondria from damage following oral delivery and may therefore form the basis for mitochondria-protective therapies. Here we review the background and work to date on this class of mitochondria-targeted antioxidants.

Novel cationic vesicle platform derived from vernonia oil for efficient delivery of DNA through plant cuticle membranes

Novel cationic amphiphilic compounds were prepared from vernonia oil, a natural epoxidized triglyceride, and studied with respect to vesicle formation, encapsulation of biomaterials such as DNA, and their physical stability and transport through isolated plant cuticle membranes. The amphiphiles studied were a single-headed compound III (a quaternary ammonium head group with two alkyl chains) and a triple-headed compound IV, which is essentially three molecules of compound III bound together through a glycerol moiety. Vesicles of the two amphiphiles, prepared by sonication in water and solutions of uranyl acetate or the herbicide 2,4-D (2,4-dichloropenoxy acetic acid), were examined by TEM, SEM, AFM, and confocal laser systems and had a spherical shape which encapsulated the solutes with diameters between 40 and 110 nm. Vesicles from amphiphile IV could be made large enough to encapsulate a condensed 5.2kb DNA plasmid (pJD328). Vesicles of amphiphile IV were also shown to pass intact across isolated plant cuticle membranes and the rate of delivery of encapsulated radio-labeled 2,4-D through isolated plant cuticle membranes obtained with these vesicles was clearly greater in comparison to liposomes prepared from dipalmitopyl phosphatidylcholine (DPPC) and the control, nonencapsulated 2,4-D. Vesicles from amphiphiles III and IV were found to be more stable than those of liposomes from DPPC. The data indicate the potential of vesicles prepared from the novel amphiphile IV to be a relatively efficient nano-scale delivery system to transport DNA and other bioactive agents through plant biological barriers. This scientific approach may open the way for further development of efficient in vivo plant transformation systems.

[Cation (K+, Mg2+, Na+, Ca2+) release in Zn(II) biosorption by Saccharomyces cerevisiae]

The biosorption of Zn(II) by the intact yeast of Saccharomyces cerevisiae was investigated for different initial concentration of the metal ion (0.08 - 0.8 mmol x L(-1)) and for different time (0 - 38h) at natural pH of 5.65 without buffer. The metal uptake was 74.84 - 654.8 micromol x g(-1) when the sorbent concentration is about 1 g x L(-1). The pH value increases and the release of physiological cations occurred in the biosorption process. Potassium ion first released rapidly in the order of hundreds of micromol x g(-1), then magnesium and sodium ions release slowly with several to less a hundred of micromol x g(-1), and the release of cadmium ion were rare. The total quantity of release is often larger than that of Zn(II) uptake. Increase in pH value and release of those cations reflected the intrinsic ability of the cell, however the presence of Zn(II) would promote the release of those cations such as K+ and Mg2+, and decrease to absorb H+. Ion exchange was one of the mechanisms for Zn(II) uptake by the biomass.

Safe immobilization of Cr(III) in heat-treated zeolite tuff compacts

The possibility to remove chromium ions from a simulated electroplating wastewater by a discontinuous ion-exchange process based on phillipsite-rich Neapolitan yellow tuff (NYT) has been investigated. The immobilization of the pollutant cation in the resulting sludge through a heat-treatment has been realized, demonstrating that compacts made of Cr-loaded NYT powder, fired at temperatures of 1000 degrees C or over, are safe materials with negligible Cr3+ leaching. The set up overall process allows, in addition, a volume reduction of the waste with associated lower disposal costs or, better, the obtainment of a ceramic material, whose physical and mechanical properties are comparable to those of similar ordinary ceramics, such as bricks. In summary, the proposed strategy looks at the polluted sludge as a resource to be exploited, instead of a dangerous material to safely dispose of.

Mechanisms of the removal of hexavalent chromium by biomaterials or biomaterial-based activated carbons

Three papers published during recent 2 years in Journal of Hazardous Materials made a mistake in analyzing chromium species in aqueous solution, resulting in incorrect elucidation of Cr(VI) biosorption; the Cr(VI) was removed from aqueous solution systems by 'anionic adsorption'. However, it has been proved that Cr(VI) is easily reduced to Cr(III) by contact with organic materials under acidic conditions because of its high redox potential value (above +1.3 V at standard condition). Therefore, it is strongly possible that the mechanism of Cr(VI) removal by biomaterials or biomaterial-based activated carbons is not "anionic adsorption" but "adsorption-coupled reduction". Thus, for researches of Cr(VI) biosorption, researchers have to analyze not only Cr(VI) but also total Cr in aqueous solution and to check the oxidation state of chromium bound on the biomaterials or activated carbons.

Sono-sorption as a new method for the removal of lead ion from aqueous solution

Sorption of Pb(II) as a toxic heavy metal ion, onto styrene-divinylbenzene co-polymer resin in the presence of ultrasound (sono-sorption) and in its absence (classical method) is presented in this work. Batch experiments were conducted to study the effect of the main parameters such as the amount of sorbent, concentration of sorbate, contact time, intensity of ultrasound and temperature on this sorption process. The equilibrium between liquid and solid phase was described by Langmuir model better than the Freundlich model. The time to reach equilibrium especially in the presence of ultrasound was very fast. This indicates that the resin mentioned has a high potential for the sorption of this pollutant ion. The isotherm constants were obtained under several different conditions. These constants were used in the calculation of the thermodynamic parameters of sorption. According to the results, the kinetics of sorption was in agreement with both pseudo-first-order and first-order reversible models.

Laboratory analyses of 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations uptake by Lemna minor

The living Lemna minor vascular plant and two different sorbents obtained by chemical treatment of this plant were tested to study the removal process of 60Co2+, 65Zn2+ and (55+59)Fe3+ from low radioactive wastewaters. The most effective sorbent was the protonated biomass, indicating the decisive contribution of the complexation process in the assembly of the uptake mechanisms. The uptake performance of the biosorbent obtained from the L. minor can be increased with approximately 20% by treatment with 0.1 N HNO3. Concerning the metabolically active mechanism, it can be notice the slow elimination of 65Zn2+ and the continuously increase of (55+59)Fe3+ uptake degree. The Na2CO3 generated in situ in systems participates to a double exchange reaction with the metallic cations during the uptake. 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations prefer for coordination N-donor ligands at the expense O-donors ones.

[Liver targeting of cationic liposomes modified with soybean-derived sterylglucoside in vitro]

AIM

To construct a liposomal liver targeting delivery system by adding soybean-derived sterylglucoside (SG) to the cationic liposomes.

METHODS

The physico-chemical properties of SG modified cationic lipsomes were investigated using fluorescein sodium (FS) as a model drug, as well as the interaction of SG modified liposomes with HepG2 2. 2. 15 cells in the point of involvement of asialoglycoprotein receptor (ASGP-R) mediated transfection. Liver targeting of modified cationic liposomes were also investigated using liver perfusing technique, and hepatocytes and non-hepatocytes were separated and examined after perfusing.

RESULTS

All the formula yielded high incorporation efficiency (83.12% - 91.74%), small particle size (93.0 - 124.4 nm). The zeta potential of blank liposomes all showed positive values. The transfection efficiency of FS entrapped in SG-liposomes with HepG2 2.2. 15 was significantly higher than that of liposomes without modification. The transfection of SG-liposomes were reduced significantly by the 20/30 mmol galactose as a competitor of ASGP-R. All the cationic liposomes showed high level of liver uptake of FS. Compared with the uptake of non-hepatocytes of each respectively, only SG/Brij-35 liposomes showed difference in FS uptake by hepatocytes (P < 0.05).

CONCLUSION

It showed that SG/Brij-35 modified cationic liposomes are potentially useful drug carrier to liver but may be affected by different modification.

Dose dependency in the oral bioavailability of an organic cation model, tributylmethyl ammonium (TBuMA), in rats: Association with the saturation of efflux by the P-gp system on the apical membrane of the intestinal epithelium

The oral bioavailability of tributylmethyl ammonium (TBuMA), an organic cation (OC), exhibited a dose-dependency (i.e., 17, 27, and 35% at doses of 0.4, 4, or 12 micromol/kg, respectively) in the rat. Relevant mechanisms were investigated in the present study by estimating the mucosal to serosal (m-s) and serosal to mucosal (s-m) transport of TBuMA across the rat ileum in an Ussing chamber experiment. The m-s permeability rapidly increased with TBuMA concentration in the mucosal side, and then becoming constant at high TBuMA concentrations. Various studies, including temperature- and potential-dependency and inhibition experiments, revealed that carrier-mediated transport mechanisms (most likely OCT1, OCT3, and P-gp) are involved in the s-m transport of TBuMA, and the saturation of the transport at higher concentrations is responsible for the concentration-dependency in the m-s permeability or dose-dependency of the bioavailability of TBuMA. A nonlinear regression of the m-s transport, based on the assumption of a mixed process of linear diffusion and saturable efflux, exhibited a clearance (CLlinear) of 0.343 microL/min/cm2 for the passive diffusion, and an apparent Km of 241 microM for the saturable process. The Km value is consistent with the concentration range in the intestine which is expected to be achieved after the oral dosing of TBuMA at a dose of 0.4 micromol/kg (i.e., 68 approximately 185 microM). Interestingly, the m-s transport of TBuMA was increased by the presence of P-gp substrates or inhibitors in the mucosal side, but not by the mucosal presence of OCT substrates or inhibitors, suggesting that only efflux transport systems on the apical membrane (e.g., P-gp), but not those on the serosal membrane (e.g., OCT1 and OCT3), of the intestinal epithelial cells, are involved in the dose-dependency or concentration dependency. A similar relationship seems likely for drugs that are substrates of efflux transporters on the apical membrane of the intestinal epithelium.

Effects of dietary or injected organic cations on larval Drosophila melanogaster: mortality and elimination of tetraethylammonium from the hemolymph

This study of larval Drosophila melanogaster examined the effects of injecting the prototypical organic cation tetraethylammonium (TEA) into the hemocoel or adding TEA and/or other organic cations to the diet. Mortality, hemolymph TEA levels, and Malpighian tubule TEA secretion rates were measured. The LD50 for dietary TEA was 158.4 mM and mortality increased if competitive inhibitors of organic cation transporters were also included in the diet. Mortality increased from 24% on TEA (100 mM) alone to 83 and 67% when the diet contained both TEA and quinidine (10 mM) or cimetidine (100 mM), respectively. TEA-selective microelectrode measurements indicated that hemolymph TEA concentration was approximately 3% of that in the diet for larvae maintained on TEA-enriched diet for 24 h. Malpighian tubules isolated from larvae exposed to dietary TEA excreted more TEA than did tubules from controls fed a TEA-free diet. However, the rate of decline of hemolymph TEA concentration following ingestion or injection of TEA into the hemocoel was greater than that explicable by rates of active transport by the gut and Malpighian tubules (MTs). We propose that TEA concentrations in the hemolymph are reduced not only by active transport across the MTs and gut, but also by diffusion into the gut. The latter pathway is particularly important when larvae previously maintained upon TEA-enriched diet are transferred to a TEA-free diet. The ingestion of TEA-free food not only clears the gut lumen, but also creates a TEA-free compartment into which TEA may passively diffuse from the hemolymph.

Hepatocytes targeting of cationic liposomes modified with soybean sterylglucoside and polyethylene glycol

AIM

In this study, a hepatocyte-specific targeting technology was developed by modifying cationic liposomes with soybean sterylglucoside (SG) and polyethylene glycol (PEG) (C/SG/PEG-liposomes).

METHODS

The liposomal transfection efficiencies in HepG(2) 2.2.15 cells were estimated with the use of fluorescein sodium (FS) as a model drug, by flow cytometry. The antisense activity of C/SG/PEG-liposomes entrapped antisense oligonucleotides (ODN) was determined as HBsAg and HBeAg in HepG(2) 2.2.15 cells by ELISA. The liposome uptake by liver and liver cells in mice was carried out after intravenous injection of (3)H-labeled liposomes.

RESULTS

C/SG-liposomes entrapped FS were effectively transfected into HepG(2) 2.2.15 cells in vitro. C/SG/PEG-liposomes entrapped ODN, reduced the secretion of both HBsAg and HBeAg in HepG(2) 2.2.15 cells when compared to free ODN. After in vivo injection of (3)H-labeled C/SG/PEG-liposomes, higher radiation accumulation was observed in the hepatocytes than non-parenchymal cells of the liver.

CONCLUSION

C/SG/PEG-liposomes mediated gene transfer to the liver is an effective gene-delivery method for hepatocytes-specific targeting, which appears to have a potential for gene therapy of HBV infections.

Airway gene transfer using cationic emulsion as a mucosal gene carrier

Background

Delivery of genes to airway mucosa would be a very valuable method for gene therapy and vaccination. However, there have been few reports on suitable gene delivery systems for administration. In this study, we use a cationic emulsion system, which is physically stable and facilitates the transfer of genes in the presence of up to 90% serum, as a mucosal gene carrier.

Methods and results

Cationic lipid emulsion was formulated with squalene and 1,2‐dioleoyl‐sn‐glycero‐3‐trimethylammoniumpropane (DOTAP) as major components. Emulsions formed stable complexes with DNA and protected and transferred DNA to target cells against DNase I digestion in the presence of mucosal destabilizers such as heparin sulfate (a polysaccharide of the glycosaminoglycan family in mucosa) and Newfectan (a natural lung extract of bovine) in an in vitro system. In contrast, commercial liposomes and counter liposomes, made with an identical lipid composition of emulsions, failed. After in vivo intranasal instillation, the cationic emulsion showed at least 200 times better transfection activity than the liposomal carriers in both nasal tissue and lung.

Conclusions

These findings show that cationic emulsions can mediate gene transfection into airway epithelium, making it a good choice for transferring therapeutic genes and for genetic vaccination against an pathogenic infection via an airway route. Copyright © 2005 John Wiley & Sons, Ltd.

[Infrared spectra analysis of chromium cation biosorbed by biosorbent ZL5-2]

Biosorption of Cr( VI) by the novel biosorbent ZL5-2 produced by Agrobacterium. sp was studied, and infrared spectra of native, absorbing and desorbing ZL5-2 were compared. The initial pH was important for biosorption. The optimum effect on Cr(VI) biosorption was acquired within initial pH 0.5-1.5, then with the pH increasing, the effect on Cr6+ biosorption was reduced. The biosorption for Cr(VI) was a quick process, only within 10 min 65.4% Cr(VI) was biosorbed, and the biosorption was in equilibrium after 60 min, then all the Cr(VI) was biosorbed after 80 min. The absorbed Cr(VI) could be recovered by desorption, and the desorption rate reached 13.6%-67.9%. The absorbance peak around 3 400 cm(-1), which reflected OH stretching vibration, moved about 8 cm(-1), and its absorbance decreased; the absorbance peak around 2 900 cm(-1) decreased, which reflected C-H stretching vibration; and the absorbance peak around 1 600 cm(-1), which reflected amide I group stretching vibration, moved about 13 cm(-1), and its absorbance decreased. After desorption, the absorbance peaks which reflected OH and C-H were increased to the initial degree, and the absorbance peak which reflected NH and amide I group did not increase. Therefore, authors presumed that the process of biosorption was reversible adsorption and irreversible adsorption simultaneously, however the reversible adsorption was more important in the biosorption.

Transport of extracellular l-arginine via cationic amino acid transporter is required during in vivo endothelial nitric oxide production

In cultured endothelial cells, 70-95% of extracellular l-arginine uptake has been attributed to the cationic amino acid transporter-1 protein (CAT-1). We tested the hypothesis that extracellular l-arginine entry into endothelial cells via CAT-1 plays a crucial role in endothelial nitric oxide (NO) production during in vivo conditions. Using l-lysine, the preferred amino acid transported by CAT-1, we competitively inhibited extracellular l-arginine transport into endothelial cells during conditions of NaCl hyperosmolarity, low oxygen, and flow increase. Our prior studies indicate that each of these perturbations causes NO-dependent vasodilation. The perivascular NO concentration ([NO]) and blood flow were determined in the in vivo rat intestinal microvasculature. Suppression of extracellular l-arginine transport significantly and strongly inhibited increases in vascular [NO] and intestinal blood flow during NaCl hyperosmolarity, lowered oxygen tension, and increased flow. These results suggest that l-arginine from the extracellular space is accumulated by CAT-1. When CAT-1-mediated transport of extracellular l-arginine into endothelial cells was suppressed, the endothelial cell NO response to a wide range of physiological stimuli was strongly depressed.

Intestinal uptake of MPP+ is differently affected by red and white wine

It is becoming increasingly evident that ingested products, such as wine, may have profound effects on the therapeutic efficacy of certain drugs. As various xeno- and endobiotics are organic cations, the purpose of our study was to examine the modulation of organic cations intestinal apical uptake by red (RW) and white wine (WW). For this purpose, we used RW, WW, the same alcohol-free wines, phenolic compounds and ethanol. The uptake of the organic cation 1-methyl-4-phenylpyridinium (MPP+) was evaluated in Caco-2 cells, an intestinal epithelial cell model. RW and alcohol-free RW increased 3H-MPP+ apical uptake, although the effect of alcohol-free RW was less pronounced. On the other hand, WW and alcohol-free WW decreased the organic cation uptake but the effect of alcohol-free WW was more pronounced. Our results show that the total content in phenolic compounds was 7 times higher, and the dialysis index was about 4 times higher in RW compared to WW. Ethanol, in the same concentration found in wine, caused a significant decrease in 3H-MPP+ apical uptake. The solution containing high molecular weight compounds from dialyzed RW increased 3H-MPP+ apical uptake. In conclusion, the results suggest that RW may increase and WW may reduce the intestinal absorption of organic cations present in the diet, such as drugs or vitamins (e.g. thiamine and riboflavin). As ethanol alone decreased the uptake of MPP+, and alcohol-free RW and WW had a lower potency than intact wine upon the transport, the presence of ethanol is probably important for the solubilisation/bioavailability of the components endowed with the transport modulating activity.

Effect of a new hepatoprotective agent, YH-439, on the hepatobiliary transport of organic cations (OCS): Selective inhibition of sinusoidal OCs uptake without influencing glucose uptake and canalicular OCs excretion

The effect of a new hepatoprotective agent, YH-439, on the hepatobiliary transport of a model organic cation (OC), TBuMA (tributylmethylammonium), was investigated. The area under the plasma concentration-time curve (AUC) from time zero to 4 h following iv administration of TBuMA (6.6 micromol/kg) was increased significantly when YH-439 in corn oil (300 mg/kg) was orally administered to rats 24 h prior to the experiment. Nevertheless, the cumulative biliary excretion of TBuMA remained unchanged. As a consequence, the apparent biliary clearance (CLb) of TBuMA was decreased significantly as a result of YH-439 pretreatment, consistent with the fact that the in vivo excretion clearance of TBuMA across the canalicular membrane (CLexc) was not changed by the pretreatment. The in vitro uptake of TBuMA into isolated hepatocytes was decreased by one half by the pretreatment, owing to a decrease in the apparent Vmax and CLlinear, but the Km for the process remained constant. Most interestingly, however, the sinusoidal uptake of glucose, a nutrient, into hepatocytes was not influenced by the pretreatment, suggesting the YH-439 pretreatment specifically impaired the sinusoidal uptake of OCs. Thus, the OC-specific inhibition of hepatic uptake, without influencing the uptake of glucose, a nutrient, appeared to be associated with the hepatoprotective activity of YH-439.

Topical Application of Ionic Polymers Affects Skin Permeability Barrier Homeostasis

We previously demonstrated that the external electric potential affected skin barrier homeostasis. On the other hand, topical application of an ionic polymer formed a diffusion electric double layer on the surface of the skin. Thus, we evaluated effects of topical application of ionic polymers on the damaged skin barrier. Application of a nonionic polymer did not affect barrier recovery. Application of sodium salts of anionic polymers accelerated barrier recovery, while that of cationic polymers delayed it. Topical application of a sodium-exchange resin accelerated barrier recovery, but application of a calcium-exchange resin had no effect even when the resins had the same structure. Application of a chloride-exchange resin delayed barrier recovery. Topical application of ionic polymers influenced skin barrier homeostasis.

Nitrates and NO release: contemporary aspects in biological and medicinal chemistry

Nitroglycerine has been used clinically in the treatment of angina for 130 years, yet important details on the mechanism of action, biotransformation, and the associated phenomenon of nitrate tolerance remain unanswered. The biological activity of organic nitrates can be said to be nitric oxide mimetic, leading to recent, exciting progress in realizing the therapeutic potential of nitrates. Unequivocally, nitroglycerine and most other organic nitrates, including NO-NSAIDs, do not behave as NO donors in the most fundamental action: in vitro activation of sGC to produce cGMP. The question as to whether the biological activity of nitrates results primarily or exclusively from NO donation will not be satisfactorily answered until the location, the apparatus, and the mechanism of reduction of nitrates to NO are defined. Similarly, the therapeutic potential of nitrates will not be unlocked until this knowledge is attained. Aspects of the therapeutic and biological activity of nitrates are reviewed in the context of the chemistry of nitrates and the elusive efficient 3e- reduction required to generate NO.

Transcriptome analysis of root transporters reveals participation of multiple gene families in the response to cation stress

Plant nutrition critically depends on the activity of membrane transporters that translocate minerals from the soil into the plant and are responsible for their intra- and intercellular distribution. Most plant membrane transporters are encoded by multigene families whose members often exhibit overlapping expression patterns and a high degree of sequence homology. Furthermore, many inorganic nutrients are transported by more than one transporter family. These considerations, coupled with a large number of so-far non-annotated putative transporter genes, hamper our progress in understanding how the activity of specific transporters is integrated into a response to fluctuating conditions. We designed an oligonucleotide microarray representing 1096 Arabidopsis transporter genes and analysed the root transporter transcriptome over a 96-h period with respect to 80 mM NaCl, K+ starvation and Ca2+ starvation. Our data show that cation stress led to changes in transcript level of many genes across most transporter gene families. Analysis of transcriptionally modulated genes across all functional groups of transporters revealed families such as V-type ATPases and aquaporins that responded to all treatments, and families - which included putative non-selective cation channels for the NaCl treatment and metal transporters for Ca2+ starvation conditions - that responded to specific ionic environments. Several gene families including primary pumps, antiporters and aquaporins were analysed in detail with respect to the mRNA levels of different isoforms during ion stress. Cluster analysis allowed identification of distinct expression profiles, and several novel putative regulatory motifs were discovered within sets of co-expressed genes.

Anionic and cationic drug secretion in the isolated perfused rat kidney after neonatal surgical induction of ureteric obstruction

OBJECTIVE

To study the pathophysiological changes of renal tubular drug transport mechanisms in congenital renal obstruction, by developing a model for perfusing the isolated kidney (IPK) after neonatal surgical induction of partial ureteric obstruction in Hanover Wistar rats.

MATERIAL AND METHODS

Moderately severe obstruction of the right kidney of male rats was created by burying a segment of the right ureter under the psoas fascia at 5-7 days after birth. Different fluorescent substrates for renal organic anion and cation drug transport systems were added to the IPK, and the concentration of these substances with time analysed in perfusate and urine.

RESULTS

The reproducibility in all groups of the glomerular filtration rate (GFR) and drug excretion was remarkably good. GFR was significantly lower in obstructed kidneys than in unobstructed kidneys. 123Rhodamine, a marker for organic cation and P-glycoprotein transport, had a significantly lower maximum excretion rate in the obstructed than in unobstructed kidneys. Renal fractional clearance (123rhodamine clearance corrected for diminished GFR) was also significantly lower in obstructed kidneys. There was no significant difference in maximum excretion (absolute and corrected GFR) for Lucifer Yellow, a marker for sodium-dependent organic anion transport. The maximum excretion rate of calcein, a marker for sodium-independent organic anion transport, was significantly lower in the obstructed than in the unobstructed kidneys, but significantly higher after correcting for reduced GFR.

CONCLUSION

The IPK is a good model for studying the effect of neonatal renal obstruction on tubular drug transport. These results show that organic anion and cation transport mechanisms are affected differently by obstruction.

Myths concerning the use of cationic liposomes in vivo

Varied results have been obtained using cationic liposomes for in vivo delivery. Furthermore, optimisation of cationic liposomal complexes for in vivo applications is complicated, involving many diverse components. These components include nucleic acid purification, plasmid design, formulation of the delivery vehicle, administration route and schedule, dosing, detection of gene expression and others. Broad assumptions have frequently been made based on data obtained from focused studies using cationic liposomes. However, these assumptions do not necessarily apply to all delivery vehicles and, most likely, do not apply to many liposomal systems, when considering these other key components which influence the results obtained in vivo. Optimising all the components of the delivery system is pivotal and will allow broad use of liposomal complexes to treat or cure human diseases or disorders. This review will highlight the features of liposomes that contribute to successful delivery, gene expression and efficacy.

cDNA cloning, functional characterization, and tissue distribution of an alternatively spliced variant of organic cation transporter hOCT2 predominantly expressed in the human kidney

A cDNA coding a novel organic cation transporter, hOCT2-A, was isolated from human kidney. The hOCT2-A cDNA is an alternatively spliced variant of hOCT2 with an insertion of 1169 bp. The open reading frame encodes a 483-amino acid protein that has 81% amino acid identity with hOCT2. From hydropathy analysis, hOCT2-A is predicted to have nine transmembrane domains. hOCT2-A mRNA is expressed mainly in kidney and weakly in brain, liver, colon, skeletal muscle, bone marrow, spinal cord, testis, and placenta. When expressed in HEK293 cells, hOCT2-A stimulated the uptake of tetraethylammonium (TEA) in an electrogenic manner. The transport of TEA by hOCT2-A-transfected cells was saturable with the apparent Km value of 63 microM. hOCT2-A stimulated the uptake of TEA, 1-methyl-4-phenylpyridinium, and cimetidine as well as did hOCT2. The uptake of guanidine and choline by hOCT2-transfected cells also increased markedly but not that by hOCT2-A-transfected cells. The uptake of TEA mediated by hOCT2-A but not by hOCT2 was inhibited significantly by organic cations such as procainamide, N-acetylprocainamide, and levofloxacin, indicating that hOCT2-A differs from hOCT2 in its affinity for several compounds. These findings suggested that hOCT2-A contributes to the renal clearance of endogenous and exogenous organic cations.

Uptake of cationzied albumin coupled liposomes by cultured porcine brain microvessel endothelial cells and intact brain capillaries

The suitability of protein-coupled liposomes as drug carriers for brain specific targeting was investigated using albumin (BSA) and cationized albumin (CBSA), respectively, as model proteins. Liposomes coated with polyethylene glycol (sterically stabilized, PEG-liposomes) were prepared from phosphatidylcholine, cholesterol, and a PEG-derivatized phospholipid and covalently coupled to thiolated BSA or CBSA. Liposomes were loaded with carboxy-fluorescein and rhodamine-labeled dipalmitoyl-phosphatidylethanolamine as hydrophilic and lipophilic marker compounds, respectively. The interaction of these constructs with monolayers of porcine brain capillary endothelial cells (BCEC) and freshly isolated porcine brain capillaries was studied by means of fluorescence assays and confocal laser scanning fluorescence microscopy (CLSFM). In contrast to BSA, CBSA was rapidly taken up by cultured BCECs. BSA-coupled liposomes did not interact with endothelial cells, whereas CBSA-coupled liposomes bound to cellular surfaces and exhibited time dependently a high intracellular accumulation. CBSA-conjugated liposomes were also taken up by intact brain capillaries. Cellular uptake could be inhibited by free cationized albumin, phenylarsineoxide, nocodazole, and filipin, but not by dansylcadaverine, suggesting a caveolae-mediated incorporation process. Immunostaining demonstrated a high expression of caveolin in the capillary endothelium. In conclusion, liposomes coupled to CBSA are taken up into brain endothelium via an endocytotic pathway and may therefore be a suitable carrier for drug delivery to the brain.

Cationic drug pharmacokinetics in diseased livers determined by fibrosis index, hepatic protein content, microsomal activity, and nature of drug

The disposition kinetics of six cationic drugs in perfused diseased and normal rat livers were determined by multiple indicator dilution and related to the drug physicochemical properties and liver histopathology. A carbon tetrachloride (CCl(4))-induced acute hepatocellular injury model had a higher fibrosis index (FI), determined by computer-assisted image analysis, than did an alcohol-induced chronic hepatocellular injury model. The alcohol-treated group had the highest hepatic alpha(1)-acid glycoprotein, microsomal protein (MP), and cytochrome P450 (P450) concentrations. Various pharmacokinetic parameters could be related to the octanol-water partition coefficient (log P(app)) of the drug as a surrogate for plasma membrane partition coefficient and affinity for MP or P450, the dependence being lower in the CCl(4)-treated group and higher in the alcohol-treated group relative to controls. Stepwise regression analysis showed that hepatic extraction ratio, permeability-surface area product, tissue-binding constant, intrinsic clearance, partition ratio of influx (k(in)) and efflux rate constant (k(out)), and k(in)/k(out) were related to physicochemical properties of drug (log P(app) or pK(a)) and liver histopathology (FI, MP, or P450). In addition, hepatocyte organelle ion trapping of cationic drugs was evident in all groups. It is concluded that fibrosis-inducing hepatic disease effects on cationic drug disposition in the liver may be predicted from drug properties and liver histopathology.

Efficient intracellular drug and gene delivery using folate receptor-targeted pH-sensitive liposomes composed of cationic/anionic lipid combinations

pH-sensitive liposomes are designed to promote efficient release of entrapped agents in response to low pH. In this study, novel pH-sensitive liposomes consisting of cationic/anionic lipid combinations are evaluated for intracellular drug and gene delivery. First, liposomes composed of egg phosphatidylcholine, dimethyldioctadecylammonium bromide (DDAB), cholesteryl hemisuccinate (CHEMS), and Tween-80 (25:25:49:1, mol/mol) were shown to stably entrap calcein at pH 7.4 and undergo rapid content release and irreversible aggregation under acidic pH. Compared to pH-sensitive liposomes incorporating dioleoylphosphatidylethanolamine, these liposomes showed improved retention of pH-sensitivity in the presence of serum. The folate receptor (FR), which is amplified in a wide variety of human tumors, could be targeted by incorporating 0.1 mol% folate-polyethyleneglycol-phosphatidylethanolamine (f-PEG-PE) into liposomes. f-PEG-PE has been shown to facilitate FR-mediated endocytosis of liposomes into KB human oral cancer cells, which express amplified FR. FR-targeted pH-sensitive liposomes produced increased cytosolic release of entrapped calcein, as shown by fluorescence microscopy, and enhanced cytotoxicity of entrapped cytosine-beta-D-arabinofuranoside, as shown by an 11-fold reduction in the IC(50) in KB cells, compared to FR-targeted non-pH-sensitive liposomes. Furthermore, FR-targeted pH-sensitive liposomes composed of DDAB/CHEMS/f-PEG-PE, combined with polylysine-condensed plasmid DNA, were shown to mediate FR-specific delivery of a luciferase reporter gene into KB cells in the presence of 10% serum. These findings suggest that cationic lipid-containing pH-sensitive liposomes, combined with FR targeting, are effective vehicles for intracellular drug and gene delivery.

Controlled release of plasmid DNA from cationized gelatin hydrogels based on hydrogel degradation

This paper shows achievement of the in vivo controlled release of a plasmid DNA from a biodegradable hydrogel and the consequent regulation of gene expression period. Cationization of gelatin was preformed through introduction of ethylenediamine and the gelatin prepared was crosslinked by various concentrations of glutaraldehyde to obtain cationized gelatin (CG) hydrogels as the carrier of plasmid DNA. In vivo release of plasmid DNA from the CG hydrogels was compared with the in vivo degradation of hydrogels. When CG hydrogels incorporating 125I-labeled plasmid DNA were implanted into the femoral muscle of mice, the plasmid DNA radioactivity remaining decreased with time and the retention period prolonged with a decrease in the water content of hydrogels used. The higher the water content of 125I-labeled CG hydrogels, the faster the hydrogel radioactivity remaining decreased with time. The time profile of plasmid DNA remaining in the hydrogels was in good accordance with that of hydrogel radioactivity, irrespective of the water content. Intramuscular implantation of plasmid DNA-incorporated CG hydrogels enhanced significantly expression of the plasmid DNA around the implanted site. The retention period of gene expression became longer as the hydrogel water content decreased. Fluorescent microscopic study revealed that the plasmid DNA-CG complex was detected around the hydrogel implanted even after 7-day implantation in marked contrast to the injection of plasmid DNA solution. It was concluded that in our hydrogel system, active plasmid DNA was released accompanied with the in vivo degradation of hydrogel, resulting in extended gene expression. The time profile of plasmid DNA release and the consequent gene expression was controllable by changing the water content of hydrogels.

Plasmid delivery in the rat brain

Neurodegenerative diseases as a class do not have effective pharmacotherapies. This is due in part to a poor understanding of the pathologies of the disease processes, and the lack of effective medications. Gene delivery is an attractive possibility for treating these diseases. For the paradigm to be effective, efficient, safe and versatile vectors are required. In this study we evaluated three plasmid delivery systems for transgene expression in the rat hippocampus. Two of these systems were designed to have enhanced intracellular biodegradability. It was hypothesized that this system would be less toxic and could increase the free (non-vector) associated plasmids within the cell, leading to increased transgene activity. Polyethylenimine (PEI) and r-AAV-2 (recombinant adeno associated virus-2) were used as positive, non-viral and viral controls respectively, in the in vivo experiments. The results from the studies indicate there is a distinct difference between the various vectors in terms of total cells transfected, type of cell transfected, and toxicity. Non-viral systems were effective at transfecting both neurons and glia cells within the hippocampus, while the r-AAV-2 transfected mainly neurons. In summary, plasmid-mediated systems are effective for transgene expression within the brain and deserve further study.

Cationic liposome-mediated gene delivery in vivo

Several improvements have been made in liposomal delivery, thus making this technology potentially useful for treatment of certain diseases in the clinic. Success in non-viral delivery is complicated and requires optimization of several components. These components include nucleic acid purification, plasmid design, formulation of the delivery vehicle, administration route and schedule, dosing, detection of gene expression, and others. With further improvements, broad use of non-viral delivery systems to treat human disorders should be possible.

[Effect of different concentrations of heavy metal ions on the normal physical and chemical characteristics of the hemolymph of Palanorbarius purpura (Mollusca: Bulinidae) in the norm and during a trematode infection]

Short-term simultaneous effect of high concentrations (LC25, LC50, LC75) of heavy metal ions. (Cu2+, Zn2+, Cd2+ and Pb2+) and infection with trematode partenites Echinoparyphium aconiatum onto haemolymph of mollusk has been investigated. It was noted that low doses of toxicant (2.5 and 10 maximum admitted concentrations) have variable effect. In infected molluscs the concentration of haemoglobin decreases, while in intact ones it increases. In relation to this index, it was found, that the ion Cu2+ is highly toxic, Zn2+ and Cd(2+)--toxic, Pb(2+)--moderately toxic.

Involvement of K(Ca2+) channels in the local abnormalities and hyperkalemia following the ischemia-reperfusion injury of rat skeletal muscle

Patch-clamp technique was used to investigate the properties of the muscular Ca2+-activated K+ channel (K(Ca2+)) in the ischemic and ischemic-reperfused rat muscle fibers and the possible involvement of this ion channel in the reperfusion-dependent hyperkalemic state. The properties of the muscular K(Ca2+) channel were unaltered following 4 h of ischemia of the lower limbs and that the serum K+ level did not change following ischemia. In contrast, after 3 h of reperfusion an over-activation of K(Ca2+) channel was observed which was related to the increase in the number of functional channels per patch area. Currents from cation aselective channels were also routinely detected in these muscles and ion channel abnormalities similar to those observed in the ischemic-reperfused muscles were also found in the contralateral muscles. Significant hyperkalemia was observed following 3 h of reperfusion. Administration of L-NAME (10 mg.kg(-1)), a nitric-oxide synthase (NOS) inhibitor, during reperfusion prevented the increase of K(Ca2+) channel activity and the activation of the cation aselective channel. The L-NAME treatment also partially antagonised the characteristic hyperkalemia observed following reperfusion. In contrast, D-NAME (20 mg.kg(-1)), the inactive antipode on NOS enzyme administered to the rats during reperfusion failed to prevent the overactivation of the K(Ca2+) channel or the hyperkalemia. Our results indicate that overactivation of K(Ca2+) channel found in the muscles following reperfusion is either directly or indirectly related to NOS activation, and contributes to the hyperkalemia. Moreover, the discovery of abnormalities similar to those of the ischemic-reperfused muscles in the contralaterals suggests that proinflammatory molecules were released from the ischemic area, accentuating the pathological state.

Conformational coupling: the moving parts of an ion pump

The Na,K-ATPase carries out the coupled functions of ATP hydrolysis and cation transport. These functions are performed by two distinct regions of the protein. ATP binding and hydrolysis is mediated by the large central cytoplasmic loop of about 430 amino-acids. Transmembrane cation transport is accomplished via coordination of the Na and K ions by side-chains of the amino-acids of several of the transmembrane segments. The way in which these two protein domains interact lies at the heart of the molecular mechanism of active transport, or ion pumping. We summarize evidence obtained from protein chemistry studies of the purified renal Na,K-ATPase and from bacterially expressed polypeptides which characterize these separate functions and point to various movements which may occur as the protein transits through its reaction cycle. We then describe recent work using heterologous expression of renal Na,K-ATPase in baculovirus-infected insect cells which provides a suitable system to characterize such protein motions and which can be employed to test specific models arising from recently acquired high resolution structural information on related ion pumps.

Lipophilicity and membrane interactions of cationic-amphiphilic compounds: syntheses and structure-property relationships

This study was performed to elucidate the relationship between steric factors, lipophilicity, and the potency of cationic-amphiphilic compounds to displace calcium ions from phosphatidylserine monolayers. The latter property is considered to be a substance/phospholipid affinity measure. A series of cationic-amphiphilic 3-phenyl-N,N-dimethylpropylamine derivatives with systematic structural variations was synthesized. Lipophilicity values were determined by chromatographic (RP-HPLC, log D(7.4)), shake-flask (log P), and theoretical (CLOGP) techniques. The potency of the compounds to displace calcium ions from phosphatidylserine monolayers was determined using a radiotracer technique, employing the isotope (45)Ca(2+). The experimental lipophilicity values of several isomeric biphenyl- and diphenyl-congeners differ more than could be expected from the CLOGP-calculations and show a good correlation to the calculated molecular surface areas. Although the affinity of the substances to the phospholipid monolayer tends to increase with lipophilicity, no general interrelation between the two properties could be found. Surprisingly, the assay system (a phospholipid monolayer) was quite sensitive towards small steric changes at the 'ligand' molecules. Stereochemical factors have a considerable influence on the interaction of solutes with phospholipid membranes. It must be questioned whether lipophilicity measures alone, without taking other molecular features into account, can meaningfully be used to explain or predict the influence of solutes on membrane-related processes and properties.

Ionic selectivity of native ATP-activated (P2X) receptor channels in dissociated neurones from rat parasympathetic ganglia

1. The relative permeability of the native P2X receptor channel to monovalent and divalent inorganic and organic cations was determined from reversal potential measurements of ATP-evoked currents in parasympathetic neurones dissociated from rat submandibular ganglia using the dialysed whole-cell patch clamp technique. 2. The P2X receptor-channel exhibited weak selectivity among the alkali metals with a selectivity sequence of Na(+) > Li(+) > Cs(+) > Rb(+) > K(+), and permeability ratios relative to Cs(+) (P(X)/P(Cs)) ranging from 1.11 to 0.86. 3. The selectivity for the divalent alkaline earth cations was also weak with the sequence Ca(2+) > Sr(2+) > Ba(2+) > Mn(2+) > Mg(2+). ATP-evoked currents were strongly inhibited when the extracellular divalent cation concentration was increased. 4. The calculated permeability ratios of different ammonium cations are higher than those of the alkali metal cations. The permeability sequence obtained for the saturated organic cations is inversely correlated with the size of the cation. The unsaturated organic cations have a higher permeability than that predicted by molecular size. 5. Acidification to pH 6.2 increased the ATP-induced current amplitude twofold, whereas alkalization to 8.2 and 9.2 markedly reduced current amplitude. Cell dialysis with either anti-P2X(2) and/or anti-P2X(4) but not anti-P2X(1) antibodies attenuated the ATP-evoked current amplitude. Taken together, these data are consistent with homomeric and/or heteromeric P2X(2) and P2X(4) receptor subtypes expressed in rat submandibular neurones. 6. The permeability ratios for the series of monovalent organic cations, with the exception of unsaturated cations, were approximately related to the ionic size. The relative permeabilities of the monovalent inoganic and organic cations tested are similar to those reported previously for cloned rat P2X(2) receptors expressed in mammalian cells.

Interactions between oligonucleotides and cationic polymers investigated by fluorescence correlation spectroscopy

PURPOSE

To evaluate whether fluorescence correlation spectroscopy (FCS) can be used to characterize the complexation between oligonucleotides and cationic polymers.

METHODS

The features of the complexes between rhodamine labeled oligonucleotides (Rh-ONs) and poly(2-dimethylamino)ethyl methacrylate (pDMAEMA), poly(ethylene glycol)-poly(ethyleneimine) (pEG-pEI), and diaminobutane-dendrimer-(NH2)64 (DAB64) were characterized by light scattering, electrophoretic mobility, electrophoresis, and FCS.

RESULTS

At low polymer/Rh-ON ratios, a decrease of the fluorescence of the Rh-ONs was observed on binding of the Rh-ONs to all cationic polymers. This was explained by the creation of "multimolecular complexes" in which the Rh-labels quench each other. The multimolecular complexes, which are highly fluorescent as they carry a number of Rh-ONs, resulted in high fluorescence peaks in the fluorescence fluctuation profile as measured by FCS. For pDMAEMA and DAB64, at higher polymer/Rh-ON ratios the fluorescence of the polyplexes increased, caused by the formation of "monomolecular complexes," which consist of only one Rh-ON per polymer. In the case of pEG-pEI, the fluorescence stayed constant when the polymer/Rh-ON ratio increased, so multimolecular polyplexes remained. FCS confirmed these results as the high fluorescence peaks disappeared in case of pDMAEMA/Rh-ON and DAB64/Rh-ON dispersions, but remained present for pEG-pEI/Rh-ON dispersions.

CONCLUSIONS

FCS seems applicable for study of the interactions between ONs and different types of cationic polymers.