Synthetic Carriers Research Articles

(Invited) The Role of Electrolysis in a Renewable Energy Economy

The United Nations Framework Convention on Climate Change (COP21) in Paris last year has underlined the urgency of a fast and consequent transformation of the various energy systems from a fossil based energy feedstock towards renewable energies like photovoltaics, wind- and hydropower, in order to drastically decrease the greenhouse gas emissions (GHG). Such a transformation requires a thorough restructuring of the energy systems with all energy carriers and consumer sectors including its intersectoral dependencies, grid structures and energy storage needs. At Fraunhofer ISE we performed time-resolved studies on how to reach the main goal of the German energy transformation to decrease its GHG emissions by at least 80% until 2050 and thus, to widely decarbonize all energy related sectors. Potential transformation pathways based on various scenarios were studied and the required costs were modelled for each scenario. The results of this modelling made very obvious that the ambitious GHG reduction targets can only be fulfilled by a strong rise in electricity generation by fluctuating renewable energies and on the other hand by the installation of large plants for producing synthetic energy carriers from renewable energies. The most versatile energy carrier for such large amounts of energy is hydrogen produced from water electrolysis. Hydrogen can be stored in large amounts in gas tube fields or salt caverns and can be used directly either in fuel cell cars and buses as a fuel or in stationary combined heat and power fuel cell systems. Furthermore the hydrogen can be used in order to hydrogenate CO2 and thus to generate green liquid fuels such as oxymehylenether (OME) or other chemicals in order to replace oil based products. The conversion of electricity into hydrogen is called Power-to-Gas, the further processing of the hydrogen and CO2 towards liquid energy carriers and chemicals is called Power-to-Liquid. With the advent of various Power-to-Gas demonstration projects it becomes clear how important this technology will be in the future energy system. Distributed water electrolyzers in the Megawatt power range will stabilize the grid frequency and voltage or will deliver other ancillary services and thus, will contribute to the secondary balancing market. Alkaline water electrolyzers are applied for more than 100 years in industrial applications and are nowadays complemented by proton exchange membrane (PEM) electrolysers in order to cover the needs for a highly dynamic load in the grid. However, main challenges of the PEM technology are high costs associated with expensive materials and the durability of cells and stacks. With ongoing technological development it is expected that PEM electrolysis systems become a competitive alternative to alkaline systems in the next years. In this talk, the technological base of water electrolyzers will be described and the related performance data, life-time expectation and cost reduction potential will be discussed. Furthermore the impact of distributed water electrolyzers in the Megawatt power range as part of an increasingly renewable energy system in terms of Power-to-Gas modelling scenarios will be given. Figure 1

Abstract 034: Characterization of A Novel Maternally Restricted Pro-angiogenic Therapeutic for Preeclampsia

Background: Preeclampsia is a major obstetrical health concern, affecting 5-8% of all pregnancies. Hallmarked by hypertension and endothelial dysfunction the origin of the disease remains obscure, though it is generally accepted that placental insufficiency/ischemia is a central cause. In response, the placenta secretes pathogenic factors, in particular the anti-angiogenic protein sFlt-1. Currently, there is no effective therapy for the management of the preeclampsia patient. We have recently produced a novel synthetic peptide based on placental growth factor (PlGF) which is maternally restricted by fusion to the synthetic carrier elastin like polypeptide (ELP). Here, we describe its in vivo pharmacokinetics and biodistribution. Methods: Fluorescently labeled ELP-PLGF was administered i.v. and blood sampled serially to determine clearance kinetics. Long-term pharmacokinetics and biodistribution was performed after subcutaneous administration of labeled peptide. Measurements were made on serially drawn blood, and in the whole animal by in vivo imaging. Results: ELP-PlGF exhibited markedly more favorable pharmacokinetics than the normal half life of PlGF, with a terminal half-life of ~10 hours as opposed to ~30 minutes for PlGF alone. Chronic administration found highest levels accumulating in placenta and kidney (two favorable targets for preeclampsia) and liver. A single subcutaneous administration at 100mg/kg resulted in sustained therapeutic plasma concentrations for over 10 days. Conclusion: These data demonstrate that ELP-PlGF has favorable pharmacokinetic and biodistribution profiles. Previous data suggest ELP-PlGF directly antagonizes sFlt-1 in culture. Future studies to assess the in vivo effectiveness of ELP-PlGF in managing placental ischemia induced hypertension and endothelial dysfunction are currently in progress. Acknowledgment: This work was supported by NIH grants R0121527 (GLB), T32HL105324 (OCL), P01HL51971, P20GM104357 (EMG), and R00HL116774 (EMG)

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'.

Enhanced gene delivery to the lung using biodegradable polyunsaturated cationic phosphatidylcholine-detergent conjugates

Lung diseases are among the more representative causes of mortality and morbidity worldwide and gene therapy is considered as a promising therapeutic approach for their treatment. However the design of efficient nucleic acid carriers for airway administration still is a challenge and there is a pressing need for new developments in this field. Herein, new synthetic DNA carriers based on the conjugation of a phospholipid and C12E4, a nonionic detergent, are developed. DNA complexes with phosphatidylcholine-detergent conjugates are administered in mouse airways, and transgene expression and inflammatory activity as an index of toxicity are investigated as a function of time, DNA dose, and presence of helper and stealth lipids. Introduction of a biodegradable linker between the phosphatidylcholine and detergent moieties significantly attenuates the severity of inflammatory response that characterizes cationic lipid-mediated gene transfer. Concurrent introduction of polyunsaturated fatty acid chains in the carrier scaffold improves transgene expression and further reduces airway inflammation. Finally, the biodegradable phosphatidylcholine-detergent conjugates favorably compare to GL67A, the gold standard for DNA delivery to the airway that is currently under clinical evaluation. Our findings indicate that the lipid formulations described herein may have great potential as nucleic acid carriers for gene therapy.

PH-Regulated Nonelectrogenic Anion Transport by Phenylthiosemicarbazones.

Gated ion transport across biological membranes is an intrinsic process regulated by protein channels. Synthetic anion carriers (anionophores) have potential applications in biological research; however, previously reported examples are mostly nonspecific, capable of mediating both electrogenic and electroneutral (nonelectrogenic) transport processes. Here we show the transmembrane Cl(-) transport studies of synthetic phenylthiosemicarbazones mimicking the function of acid-sensing (proton-gated) ion channels. These anionophores have remarkable pH-switchable transport properties with up to 640-fold increase in transport efficacy on going from pH 7.2 to 4.0. This "gated" process is triggered by protonation of the imino nitrogen and concomitant conformational change of the anion-binding thiourea moiety from anti to syn. By using a combination of two cationophore-coupled transport assays, with either monensin or valinomycin, we have elucidated the fundamental transport mechanism of phenylthiosemicarbazones which is shown to be nonelectrogenic, inseparable H(+)/Cl(-) cotransport. This study demonstrates the first examples of pH-switchable nonelectrogenic anion transporters.

Synthesis of a novel archaeal tetraether-type lipid containing a diorthoester group as a helper lipid for gene delivery

As an alternative to recombinant virus, synthetic carriers are widely developed for providing efficient and safe DNA delivery. To reach the nucleus where nucleic acid (NA) constructs are transcripted, chemical complexes have to overcome serious cellular traps such as endosomal escape and intracellular trafficking. Here, the design and the multi-step synthesis of a stabilizing tetraether lipid analogue of archaeal counterparts containing a diorthoester moiety in the middle of the bridging chain were described. The key step involved a double coupling reaction between two diether alcohols and a diketene acetal. Under aqueous acidic conditions, the diorthoester function of the tetraether lipid can be hydrolysed to yield two monopolar diether lipids. Applied to gene delivery in association with a cationic lipid, this new helper bipolar tetraether lipid led to lipid–DNA complexes with sizes and potential zeta values depending on the charge ratios (+/−). In addition, preliminary in vitro transfection assays supported the interest of these novel bipolar lipid-based lipoplex formulations compared to standard Lipofectamine-based formulations.

The hypoxia-induced dehydrogenase HorA is required for coenzyme Q10 biosynthesis, azole sensitivity and virulence of Aspergillus fumigatus.

Aspergillus fumigatus is the predominant airborne pathogenic fungus causing invasive aspergillosis in immunocompromised patients. During infection A.fumigatus has to adapt to oxygen-limiting conditions in inflammatory or necrotic tissue. Previously, we identified a mitochondrial protein to be highly up-regulated during hypoxic adaptation. Here, this protein was found to represent the novel oxidoreductase HorA. In Saccharomyces cerevisiae a homologue was shown to play a role in biosynthesis of coenzyme Q. Consistently, reduced coenzyme Q content in the generated ΔhorA mutant indicated a respective function in A. fumigatus. Since coenzyme Q is involved in cellular respiration and maintaining cellular redox homeostasis, the strain ΔhorA displayed an impaired response to both oxidative and reductive stress, a delay in germination and an accumulation of NADH. Moreover, an increased resistance against antifungal drugs was observed. All phenotypes were completely reversed by the addition of the synthetic electron carrier menadione. The deletion strain ΔhorA showed significantly attenuated virulence in two murine infection models of invasive pulmonary aspergillosis. Therefore, the biosynthesis of coenzyme Q and, particularly, the fungal-specific protein HorA play a crucial role in virulence of A. fumigatus. Due to its absence in mammals, HorA might represent a novel therapeutic target against fungal infections.

Evaluation of a Gelatin-Modified Poly(ε-Caprolactone) Film as a Scaffold for Lung Disease

ABSTRACTLung transplantation is a necessary step for the patients with the end stage of chronic obstructive pulmonary disease. The use of artificial lungs is a promising alternative to natural lung transplantation which is complicated and is restricted by low organ donations. For successful lung engineering, it is important to choose the correct combination of specific biological cells and a synthetic carrier polymer. The focus of this study was to investigate the interactions of human lung epithelial cell line NCl-H292 that is involved in lung tissue development with the biodegradable poly(ε-caprolactone) before and after its chemical modification to evaluate potential for use in artificial lung formation. Also, the effect of polymer chemical modification on its mechanical and surface properties has been investigated. The poly(ε-caprolactone) surface was modified using aminolysis followed by immobilization of gelatin. The unmodified and modified polymer surfaces were characterized for roughness, tensile strength, and NCl-H292 metabolic cell activity. The results showed for the first time the possibility for NCI-H292 cells to adhere on this polymeric material. The resazurin assay showed that the metabolic activity at 24 h postseeding of 80% in the presence of the unmodified and greater than 100% in the presence of the modified polymer was observed. The roughness of the poly(ε-caprolactone) increased from 4 to 26 nm and the film strength increased from 0.01 to 0.045 kN when the material was chemically modified. The results obtained to date show potential for using modified poly(ε-caprolactone) as a scaffold for lung tissue engineering.

Biochemical indicators of nephrotoxicity in blood serum of rats treated with novel 4-thiazolidinone derivatives or their complexes with polyethylene glycol-containing nanoscale polymeric carrier

The aim of this study was to compare the effect of new synthetic 4-thiazolidinone derivatives (potential anticancer compounds denoted as 3882, 3288 and 3833) and doxorubicin (positive control) in free form and in their complexes with synthetic polyethylene glycol-containing nanoscale polymeric carrier on the biochemical indicators of nephrotoxicity in blood serum of rats. The concentration of total protein, urea, creatinine, glucose, ions of sodium, potassium, calcium, iron and chloride was measured. It was found that after injection of the investigated compounds, the concentration of sodium cations and chloride anions in blood serum was increased compared with control (untreated animals). Doxorubicin’s injection was accompanied by a decrease in the concentration of iron cations. The concentration of total protein, urea and creatinine decreased under the influence of the studied compounds. Complexation of these аntineoplastic substances with a synthetic polymeric nanocarrier lowered the concentration of the investigated metabolites substantially compared to the effect of these compounds in free form. The normalization of concentration of total protein, urea and creatinine in blood serum of rats treated with complexes of the studied compounds with the polymeric carrier comparing with increased concentration of these indicators at the introduction of such compounds in free form was found.

Novel polymeric nanoparticles targeting the lipopolysaccharides of Pseudomonas aeruginosa

Considering outburst of various infectious diseases globally, nanoparticle assisted targeted drug delivery has emerged as a promising strategy that can enhance the therapeutic efficacy and minimize the undesirable side effects of an antimicrobial agents. Molecular imprinting is a newly developed strategy that can synthesize a drug carrier with highly stable ligand-like ‘cavity’, may serve as a new platform of ligand-free targeted drug delivery systems. In this study, we use the amphiphilic lipopolysaccharides, derived from Pseudomonas aeruginosa as imprinting template and obtained an evenly distributed sub-40nm polymeric nanoparticles by using inverse emulsion method. These molecularly imprinted nanoparticles (MIPNPs) showed specific binding to the lipopolysaccharide as determined by fluorescence polarization and microscale thermophoresis. MIPNPs showed selective recognition of target bacteria as detected by flow cytometry. Additionally, MIPNPs exhibited the in vivo targeting capabilities in both the keratitis model and meningitis model. Moreover, the photosensitizer methylene blue-loaded MIPNPs presented significantly strong inhibition of bacterial Growth, compared to non-imprinted controls for in vitro model of the photodynamic therapy. Our study shows an attempt to design a magic bullet by molecular imprinting that may provide a novel approach to generate synthetic carrier for targeting pathogen and treatment for a variety of infectious human diseases.

Formulation of Nanoparticles Against TB--A Review.

Tuberculosis is a major public health concern. The present article reviews the current updates on the usage of nanoparticles against tuberculosis and recent patents that could develop into novel therapeutics available to the clinical armamentarium for the TB management. The drug delivery systems involving nanoparticles are suitable against chronic diseases such as tuberculosis. Polymers in many forms like liposomes, dendrimers, Nanoemulsions can be used as synthetic and natural carriers for first line and second line drugs employed for chemotherapy. Not only are the drugs sustainably released in organs and plasma, but also their dosages as well as adverse effects have been reduced, the drug interaction has increased and the drug resistant bacteria have been targeted. The hurdles in the development of anti-tuberculosis have made Nano medicines to act as a silver lining.

Tilting and Tumbling in Transmembrane Anion Carriers: Activity Tuning through n-Alkyl Substitution.

Anion transport by synthetic carriers (anionophores) holds promise for medical applications, especially the treatment of cystic fibrosis. Among the factors which determine carrier activity, the size and disposition of alkyl groups is proving remarkably important. Herein we describe a series of dithioureidodecalin anionophores, in which alkyl substituents on one face are varied from C0 to C10 in two‐carbon steps. Activities increase then decrease as the chain length grows, peaking quite sharply at C6. Molecular dynamics simulations showed the transporter chloride complexes releasing chloride as they approach the membrane‐aqueous interface. The free transporter then stays at the interface, adopting an orientation that depends on the alkyl substituent. If chloride release is prevented, the complex is positioned similarly. Longer chains tilt the binding site away from the interface, potentially freeing the transporter or complex to move through the membrane. However, chains which are too long can also slow transport by inhibiting movement, and especially reorientation, within the phospholipid bilayer.

Properties and potential application of modern adsorbents in formulation of solid drug delivery systems

In latest years, many natural and synthetic solid carriers attract increasing attention, due to theirs biocompatibility, acceptable ecological and toxicological properties, possible modification of physico-chemical properties, simple production, high stability and relatively low price. These carriers have similar chemical structure, mostly based on silicon-dioxide, magnesium aluminometasilicate and calcium phosphate, and differ from each other in structure porosity, specific surface area, size, volume and shape of pores, and possibility of surface functionalization. Ordered mesoporous materials like MCM - 41 and SBA - 15, as well as porous materials from Neusilin® and Sylysia® groups, represent the most common adsorbents evaluated in order to increase drug dissolution rate, and its bioavailability, and also in modifiedand targeted drug release formulations. Also, natural silica material, isolated from diatomites, diatom microshells, with its unique characteristics, represents relatively cheap solid carrier used in formulation of oral dosage forms and implants. Modern adsorbents are mostly used in formulations of solid dispersions with low water-soluble drugs, or as solid carriers for lipid formulations. In latest years, modern porous carriers are evaluated for possible surface functionalization in order to achieve prolonged or signal-initiated drug release.

Electrospun Food-Grade Ultrafine Fibers from Pectin and Pullulan Blends

Electrospinning was used to produce ultrafine fibers and fibrous mats from aqueous solutions containing two edible polysaccharides: pectin (PEC) and pullulan (PUL). The process excluded the use of a synthetic carrier polymer or non-aqueous solvents thus maintaining the food-grade status of the components. The inclusion of PUL reduced the surface tension and electric conductivity of pectin solution, and promoted molecular entanglement between PEC and PUL as confirmed by rheological analysis. The spinnability of either polysaccharide was promoted by inclusion of the other. Cross-linking PEC networks were obtained by soaking the fibrous mats in successive Ca2+ solution. The fibrous mats can be used to carry bioactive compounds as demonstrated using probiotic bacteria Lactobacillus rhamnosus GG (LGG) as a model bioactive compound. The research is significant for the development of food products with unique textures and functionalities.

Quantitative Intracellular Localization of Cationic Lipid-Nucleic Acid Nanoparticles with Fluorescence Microscopy.

Current activity in developing synthetic carriers of nucleic acids (NA) and small molecule drugs for therapeutic applications is unprecedented. One promising class of synthetic vectors for the delivery of therapeutic NA is PEGylated cationic liposome (CL)-NA nanoparticles (NPs). Chemically modified PEG-lipids can be used to surface-functionalize lipid-NA nanoparticles, allowing researchers to design active nanoparticles that can overcome the various intracellular and extracellular barriers to efficient delivery. Optimization of these functionalized vectors requires a comprehensive understanding of their intracellular pathways. In this chapter we present two distinct methods for investigating the intracellular activity of PEGylated CL-NA NPs using quantitative analysis with fluorescence microscopy.The first method, spatial localization, describes how to prepare fluorescently labeled CL-NA NPs, perform fluorescence microscopy and properly analyze the data to measure the intracellular distribution of nanoparticles and fluorescent signal. We provide software which allows data from multiple cells to be averaged together and yield statistically significant results. The second method, fluorescence colocalization, describes how to label endocytic organelles via Rab-GFPs and generate micrographs for software-assisted NP-endocytic marker colocalization measurements. These tools will allow researchers to study the endosomal trafficking of CL-NA NPs which can guide their design and improve their efficiency.

Magnetotactic bacterial cages as safe and smart gene delivery vehicles

In spite of the huge advances in the area of synthetic carriers, their efficiency still poorly compares to natural vectors. Herein, we report the use of unmodified magnetotactic bacteria as a guidable delivery vehicle for DNA functionalized gold nanoparticles (AuNPs). High cargo loading is established under anaerobic conditions (bacteria is alive) through endocytosis where AuNPs are employed as transmembrane proteins mimics (facilitate endocytosis) as well as imaging agents to verify and quantify loading and release. The naturally bio-mineralized magnetosomes, within the bacteria, induce heat generation inside bacteria through magnetic hyperthermia. Most importantly after exposing the system to air (bacteria is dead) the cell wall stays intact providing an efficient bacterial vessel. Upon incubation with THP-1 cells, the magnetotactic bacterial cages (MBCs) adhere to the cell wall and are directly engulfed through the phagocytic activity of these cells. Applying magnetic hyperthermia leads to the dissociation of the bacterial microcarrier and eventual release of cargo.

Membrane Perturbation-Associated Ca2+ Signaling and Incoming Genome Sensing Are Required for the Host Response to Low-Level Enveloped Virus Particle Entry.

The type I interferon (IFN) response is an important aspect of innate antiviral defense, and the transcription factor IRF3 plays an important role in its induction. Membrane perturbation during fusion, a necessary step for enveloped virus particle entry, appears sufficient to induce transcription of a subset of IFN-stimulated genes (ISGs) in an IRF3-dependent, IFN-independent fashion. IRF3 is emerging as a central node in host cell stress responses, although it remains unclear how different forms of stress activate IRF3. Here, we investigated the minimum number of Sendai virus (SeV) and human cytomegalovirus (HCMV) particles required to activate IRF3 and trigger an antiviral response. We found that Ca(2+) signaling associated with membrane perturbation and recognition of incoming viral genomes by cytosolic nucleic acid receptors are required to activate IRF3 in response to fewer than 13 particles of SeV and 84 particles of HCMV per cell. Moreover, it appears that Ca(2+) signaling is important for activation of STING and IRF3 following HCMV particle entry, suggesting that Ca(2+) signaling sensitizes cells to recognize genomes within incoming virus particles. To our knowledge, this is the first evidence that cytosolic nucleic acid sensors recognize genomes within incoming virus particles prior to virus replication. These studies highlight the exquisite sensitivity of the cellular response to low-level stimuli and suggest that virus particle entry is sensed as a stress signal. The mechanism by which replicating viruses trigger IRF3 activation and type I IFN induction through the generation and accumulation of viral pathogen-associated molecular patterns has been well characterized. However, the mechanism by which enveloped virus particle entry mediates a stress response, leading to IRF3 activation and the IFN-independent response, remained elusive. Here, we find that Ca(2+) signaling associated with membrane perturbation appears to sensitize cells to recognize genomes within incoming virus particles. To our knowledge, this is the first study to show that cytosolic receptors recognize genomes within incoming virus particles prior to virus replication. These findings not only highlight the sensitivity of cellular responses to low-level virus particle stimulation, but provide important insights into how nonreplicating virus vectors or synthetic lipid-based carriers used as clinical delivery vehicles activate innate immune responses.

Storing Renewable Energy in the Hydrogen Cycle.

An energy economy based on renewable energy requires massive energy storage, approx. half of the annual energy consumption. Therefore, the production of a synthetic energy carrier, e.g. hydrogen, is necessary. The hydrogen cycle, i.e. production of hydrogen from water by renewable energy, storage and use of hydrogen in fuel cells, combustion engines or turbines is a closed cycle. Electrolysis splits water into hydrogen and oxygen and represents a mature technology in the power range up to 100 kW. However, the major technological challenge is to build electrolyzers in the power range of several MW producing high purity hydrogen with a high efficiency. After the production of hydrogen, large scale and safe hydrogen storage is required. Hydrogen is stored either as a molecule or as an atom in the case of hydrides. The maximum volumetric hydrogen density of a molecular hydrogen storage is limited to the density of liquid hydrogen. In a complex hydride the hydrogen density is limited to 20 mass% and 150 kg/m(3) which corresponds to twice the density of liquid hydrogen. Current research focuses on the investigation of new storage materials based on combinations of complex hydrides with amides and the understanding of the hydrogen sorption mechanism in order to better control the reaction for the hydrogen storage applications.

Synthetic and Biological Vesicular Nano-Carriers Designed for Gene Delivery.

Synthetic and biological vesicular carriers have been recognized as attractive and intelligent systems for delivery of a verity of bioactive molecules. The importance of such delivery systems can be mostly due to their physicochemical properties, i.e. a lipid bilayer surrounding an aqueous core which allows encapsulation and protection of active hydrophilic molecules such as nucleic acids. Synthetic vesicles such as liposomes have been studied as gene delivery systems for decades. However, due to their fast clearance, toxicity and immunogenicity which impose restrictions on clinical applications, some other natural lipid vesicles such as exosomes have been considered as alternatives. Attractive features of nature's own 'nano-vesicles' such as exosomes, virosomes, bacterial ghosts and erythrocyte ghosts include efficient cellular entry, physicochemical properties and evading immune responses. Nevertheless, there are advantages and disadvantages with both synthetic and biological vesicular systems. Here, we provide an overview into different vesicle-based gene delivery systems and discuss how various modifications in their structure and formulations could improve the transfection efficiency and decrease the toxicity.

Efficient, non-toxic anion transport by synthetic carriers in cells and epithelia.

Transmembrane anion transporters (anionophores) have potential for new modes of biological activity, including therapeutic applications. In particular they might replace the activity of defective anion channels in conditions such as cystic fibrosis. However, data on the biological effects of anionophores are scarce, and it remains uncertain whether such molecules are fundamentally toxic. Here, we report a biological study of an extensive series of powerful anion carriers. Fifteen anionophores were assayed in single cells by monitoring anion transport in real time through fluorescence emission from halide-sensitive yellow fluorescent protein. A bis-(p-nitrophenyl)ureidodecalin shows especially promising activity, including deliverability, potency and persistence. Electrophysiological tests show strong effects in epithelia, close to those of natural anion channels. Toxicity assays yield negative results in three cell lines, suggesting that promotion of anion transport may not be deleterious to cells. We therefore conclude that synthetic anion carriers are realistic candidates for further investigation as treatments for cystic fibrosis.