Polyanionic Charge Research Articles

Electro-templating of prussian blue nanoparticles in PEDOT:PSS and soluble silkworm protein for hydrogen peroxide sensing

Herein, we demonstrate a high-accuracy H2O2 selective organic-inorganic 3D-heterointerface based on catalytically in-situ reduced Prussian-blue nanoparticles (PBNPs), Poly (3,4-ethylene dioxythiophene):poly (styrene sulfonic acid) (PEDOT:PSS) and water-soluble Silkworm protein (SWp). PBNPs were immobilized on an indium tin oxide-coated glass (ITO) electrode through the electrochemical polymerization process of PEDOT:PSS and the yielding intertwining composite was templated by the use of SWp, simultaneously. Since PSS and SWp act as poly-anionic and poly-cationic charge compensating elements, the sensing system's potential cycling and amperometric response stability have been significantly enhanced thanks to the arising physical blockage effect. Constructed sensing system showed a substantially high sensitivity (1031.7 μA mM−1 cm−2) and a low limit of detection value (LOD, 0.29 μM) between 1 and 130 μM H2O2. Eliminating the possible signal disruptions by common anion and cations in tap water, the (PEDOT:PSS:PB):SWp interface successfully selected H2O2 between the concentration of 10–40 μM with high recovery and relatively low RSDs oscillating between 94.2-110.9% and 2.9–5.1%, respectively. It is thought that the proposed heterointerface can be used in the field of sensor, biosensor and fuel cell systems run by H2O2 assay based on 3D scaffold-templated conductive polymer-PBNPs network.

Revisiting the Extinction of the RNA World

The ribozyme world is thought to have evolved the burdensome complexity of peptide and protein synthesis because the 20 amino acid side chains are catalytically superior. Instead, I propose that the Achilles heel of the RNA world that led to the extinction of riboorganisms was RNA’s polyanionic charges that could not be covalently neutralized stably by phosphotriester formation. These charges prevented development of hydrophobic cores essential for integration into membranes and many enzymatic reactions. In contrast, the phosphotriester modification of DNA is stable. So, the fact that the charge was never removed in DNA evolution gives further credence to proteins coming before DNA.

Inhibitory mechanisms of humic substances and polyacrylic acid during the initial stage of polycation-induced flocculation

Although natural organic matter (NOM) is known to reduce the efficiency of polycationic flocculants used for solid-liquid separation in water treatment processes, mechanisms underlying this inhibitory effect are not yet fully understood. In this study, the inhibitory effects of naturally occurring humic substances and a synthetic polyelectrolyte (as a comparison), polyacrylic acid (PAA), on the initial stage of colloidal flocculation induced by the addition of a cationic linear polyelectrolyte are investigated under a standardized mixing flow condition. Flocculation enhancement is hindered by all the tested polyanions, while electrophoretic mobility experiments reveal that the polyanions affect the isoelectric point of particles. At the same polycation to polyanion charge ratio, the degree of inhibition decreases in the order PAA > Suwannee River humic acid > Suwannee River fulvic acid, corresponding to their affinity toward the polycations and particles. We propose that the inhibitory mechanism is mainly driven by the electrostatic attractions between the flocculant and polyanions, and this mechanism involves three stages. The influence of polyanion affinity on the complexation with polycations is also discussed. The insights gained in this study can be useful in predicting the flocculation behavior of suspended solids co-existing with NOM in natural environments when flocculants are added.

Processable and nanofibrous polyaniline:polystyrene-sulphonate (nano-PANI:PSS) for the fabrication of catalyst-free ammonium sensors and enzyme-coupled urea biosensors

Tailoring conducting polymers (CPs) such as polyaniline (PANI) to deliver the appropriate morphology, electrochemical properties and processability is essential for the development of effective polymer-based electrochemical sensors and biosensors. Composite PANI electrodes for the detection of ammonium (NH4+) have been previously reported, but have been limited by their reliance on the electrocatalytic reaction between NH4+ and a metal/nano-catalyst. We report an advanced processable and nanofibrous polyaniline:polystyrene-sulphonate (nano-PANI:PSS) as a functional ink for the fabrication of catalyst-free NH4+ sensors and enzyme-coupled urea biosensors. The PSS provides both a soft-template for nanofibre formation and a poly-anionic charge compensator, enabling the detection of NH4+ based on an intrinsic doping/de-doping mechanism. The nanostructured morphology, chemical characteristics and electrochemical properties of the nano-PANI:PSS were characterised. We fabricated 3D-hierarchical sensor interfaces composed of inter-connected nano-PANI:PSS fibres (diameter of ~50.3 ± 4.8 nm) for the detection of NH4+ with a wide linear range of 0.1–11.5 mM (R2 = 0.996) and high sensitivity of 106 mA M−1 cm−2. We further demonstrated the coupling of the enzyme urease with the nano-PANI:PSS to create a urea biosensor with an innovative biocatalytic product-to-dopant relay mechanism for the detection of urea, with a linear range of 0.2–0.9 mM (R2 = 0.971) and high sensitivity of 41 mA M−1 cm−2. Moreover, the nano-PANI:PSS-based sensors show good selectivity for the detection of NH4+and urea in a urine model containing common interfering molecules. This processable and fibrous nano-PANI:PSS provides new advance on CP-based transducer materials in the emerging field of printed organic sensors and biosensors.

Promoting the Delivery of Nanoparticles to Atherosclerotic Plaques by DNA Coating.

Many nanoparticle-based carriers to atherosclerotic plaques contain peptides, lipoproteins, and sugars, yet the application of DNA-based nanostructures for targeting plaques remains infrequent. In this work, we demonstrate that DNA-coated superparamagnetic iron oxide nanoparticles (DNA-SPIONs), prepared by attaching DNA oligonucleotides to poly(ethylene glycol)-coated SPIONs (PEG-SPIONs), effectively accumulate in the macrophages of atherosclerotic plaques following an intravenous injection into apolipoprotein E knockout (ApoE-/-) mice. DNA-SPIONs enter RAW 264.7 macrophages faster and more abundantly than PEG-SPIONs. DNA-SPIONs mostly enter RAW 264.7 cells by engaging Class A scavenger receptors (SR-A) and lipid rafts and traffic inside the cell along the endolysosomal pathway. ABS-SPIONs, nanoparticles with a similarly polyanionic surface charge as DNA-SPIONs but bearing abasic oligonucleotides also effectively bind to SR-A and enter RAW 264.7 cells. Near-infrared fluorescence imaging reveals evident localization of DNA-SPIONs in the heart and aorta 30 min post-injection. Aortic iron content for DNA-SPIONs climbs to the peak (∼60% ID/g) 2 h post-injection (accompanied by profuse accumulation in the aortic root), but it takes 8 h for PEG-SPIONs to reach the peak aortic amount (∼44% ID/g). ABS-SPIONs do not appreciably accumulate in the aorta or aortic root, suggesting that the DNA coating (not the surface charge) dictates in vivo plaque accumulation. Flow cytometry analysis reveals morepronounced uptake of DNA-SPIONs by hepatic endothelial cells, splenic macrophages and dendritic cells, and aortic M2 macrophages (the cell type with the highest uptake in the aorta) than PEG-SPIONs. In summary, coating nanoparticles with DNA is an effective strategy of promoting their systemic delivery to atherosclerotic plaques.

Chemical and biological methods for probing the structure and functions of polysialic acids.

Owing to its poly-anionic charge and large hydrodynamic volume, polysialic acid (polySia) attached to neural cell adhesion molecule regulates axon-axon and axon-substratum interactions and signalling, particularly, in the development of the central nervous system (CNS). Expression of polySia is spatiotemporally regulated by the action of two polysialyl transferases, namely ST8SiaII and ST8SiaIV. PolySia expression peaks during late embryonic and early post-natal period and maintained at a steady state in adulthood in neurogenic niche of the brain. Aberrant polySia expression is associated with neurological disorders and brain tumours. Investigations on the structure and functions, over the past four decades, have shed light on the physiology of polySia. This review focuses on the biological, biochemical, and chemical tools available for polySia engineering. Genetic knockouts, endo-neuraminidases that cleave polySia, antibodies, exogenous expression, and neuroblastoma cells have provided deep insights into the ability of polySia to guide migration of neuronal precursors in neonatal brain development, neuronal clustering, axonal pathway guidance, and axonal targeting. Advent of metabolic sialic acid engineering using ManNAc analogues has enabled reversible and dose-dependent modulation polySia in vitro and ex vivo. In vivo, ManNAc analogues readily engineer the sialoglycans in peripheral tissues, but show no effect in the brain. A recently developed carbohydrate-neuroactive hybrid strategy enables a non-invasive access to the brain in living animals across the blood-brain barrier. A combination of recent advances in CNS drugs and imaging with ManNAc analogues for polySia modulation would pave novel avenues for understanding intricacies of brain development and tackling the challenges of neurological disorders.

In‐situ Complex and Sb–N Bond Formation in an Antimonato Polyoxovanadate Reaction System

The self‐assembly reaction towards the archetypal antimonato polyoxovanadate {V15Sb6} in the presence of two organic amines, 1‐(2‐aminoethyl)piperazine (aep) and diethylenetriamine (dien), and a simple NiII salt yields the compound {Ni(dien)2}2[(aepH)2V15Sb6O42(H2O)]·7.5H2O in which secondary [Ni(dien)2]2+ coordination complexes and covalent Sb–Naep bonds coexist. The latter augment the spherical [V15Sb6O42(H2O)]6– cluster core by two protonated aep groups that effectively reduce the polyanion's charge. The terminal NH3 groups of the two crystallographically independent aep units interlink two adjacent cluster anions through strong N–H···O interactions. In the solid state, this results in a tight 3D network of Sb–N and hydrogen bonds, which only starts to release its crystal water above 150 °C. As anticipated from its structure, the magnetic properties of the title compounds can be modeled using an additive approach.

Interactions between Oppositely Charged Polyelectrolytes by Isothermal Titration Calorimetry: Effect of Ionic Strength and Charge Density

In this study, binding of linear poly(l-lysine) to a series of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate copolymers was examined by isothermal titration calorimetry (ITC). Binding constant and stoichiometry were systematically determined at different ionic strengths and for different polyanion charge densities varying between 15% and 100%. The range of investigated ionic strengths was carefully adjusted according to the polyanion charge densities to get measurable binding constants (i.e., formation binding constant typically comprised between 104 and 106 M-1) by isothermal titration calorimetry (ITC). The number of released counterions during the polyelectrolyte complex formation was determined from the log-log dependence of the binding constant according to the ionic strength and was compared to the total number of condensed counterions estimated from the Manning theory. Experimental results obtained by ITC are in very good agreement with those previously obtained by frontal analysis continuous capillary electrophoresis (FACCE) and can be used to model and predict the binding parameters at any ionic strength or any polyanion charge density. Thermodynamic parameters of the complexation between the oppositely charged polyelectrolytes confirm that the complex formation was entropically driven together with a favorable (but minor) enthalpic contribution. For the first time, specificities, advantages/disadvantages of ITC, and FACCE techniques for studying polyelectrolyte complexations are compared and discussed, using the same experimental conditions.

Angiotensin converting-enzyme inhibition restores glomerular glycosaminoglycans in rat puromycin nephrosis

BackgroundAberrant glomerular polyanionic charge of glycosaminoglycans (GAGs) and sialic acid expression has been observed in proteinuric human and experimental glomerular diseases. Angiotensin-converting enzyme inhibitors (ACEI) lower proteinuria and amend renal function deterioration via hemodynamic mechanisms. We tested the hypothesis that ACEI modulate proteinuria additionally by modifying glomerular GAGs. MethodsIn this study, we explored the effects of the ACEI enalapril on proteinuria and GAG synthesis in puromycin aminonucleoside (PAN)-treated rats. We employed cationic colloidal gold (CCG) localization in glomerular basement membranes (GBM) to identify GAGs by electron microscopy and determined sialic acid residues by immunohistochemical staining with lectins. To clarify ACEI effects on GAG production in vitro, we studied de novo GAG synthesis into newly synthesized proteoglycans in podocytes and mesangial cells using 35S incorporation. Cells were incubated with or without PAN, and with increasing doses of the ACEI enalaprilat. ResultsPAN rats developed severe proteinuria that was significantly improved by enalapril treatment. In non-treated PAN rats GBM GAGs were reduced, whereas in the enalapril-treated group GBM GAGs were significantly increased to control levels. Enalapril did not affect glomerular sialic acid. Furthermore, in cultured podocytes and mesangial cells PAN decreased de novo GAG synthesis, an effect which was significantly ameliorated by enalaprilat treatment. ConclusionTreatment with ACEI improves permselectivity properties of the glomerular capillary wall by maintaining its GAG content. This finding provides an additional new mechanism, whereby ACEI exert anti-proteinuric effects.

Hexacyano octahedral metallic clusters as versatile building blocks in the design of extended polymeric framework and clustomesogens

Self-assembling abilities of Katn[M6Qi8(CN)a6] hybrid nanomaterials are tailored by the metallic cluster polyanionic charge while the latter keeps its intrinsic properties within the liquid crystal phases.

Contribution of syndecans to lipoplex-mediated gene delivery

The long awaited breakthrough of gene therapy significantly depends on the in vivo efficiency of targeted intracellular delivery. Hidden details of cellular uptake present a great hurdle for non-viral gene delivery with liposomes. Growing scientific evidence supports the involvement of polyanionic cell surface carbohydrates in cellular internalization of cationic liposomes. Syndecans, a highly conserved family of transmembrane heparan sulfate proteoglycans serve attachment sites for great variety of cationic ligands including growth factors, cytokines and even parasites. In the present study we quantitatively measured the contribution of various syndecan isoforms to liposome-mediated gene transfer. The obtained data show the superiority of syndecan-4, the ubiquitously expressed isoform of the syndecan family, in cellular uptake of liposomes. Applied mutational analysis demonstrated that gene delivery could be abolished by mutating the glycosaminoglycan attachment site of syndecans, highlighting the importance of polyanionic heparan sulfate side chains in the attachment of cationic liposomes. Blocking sulfation of syndecans also diminished gene delivery, a finding that confirms the essential role of polyanionic charges in binding cationic liposomes. Mutating other parts of the syndecan extracellular domain, including the cell-binding domain, had clearly smaller effect on liposome internalization. Mutational analyses also revealed that superiority of syndecan-4 in liposome-mediated gene delivery is significantly influenced by its cytoplasmic domain that orchestrates signaling pathways leading to macropinocytosis. In summary our study present a mechanistic insight into syndecan-mediated macropinocytic uptake of lipoplexes and highlights syndecan-4 as a superior target for cationic liposomes.

A Multiunit Catalyst with Synergistic Stability and Reactivity: A Polyoxometalate–Metal Organic Framework for Aerobic Decontamination

A combination of polyanion size and charge allows the Keggin-type polyoxometalate (POM), [CuPW(11)O(39)](5-), a catalyst for some air-based organic oxidations, to fit snuggly in the pores of MOF-199 (HKUST-1), a metal-organic framework (MOF) with the POM countercations residing in alternative pores. This close matching of POM diameter and MOF pore size in this POM-MOF material, [Cu(3)(C(9)H(3)O(6))(2)](4)[{(CH(3))(4)N}(4)CuPW(11)O(39)H] (1), results in a substantial synergistic stabilization of both the MOF and the POM. In addition, this heretofore undocumented POM-MOF interaction results in a dramatic increase in the catalytic turnover rate of the POM for air-based oxidations. While 1 catalyzes the rapid chemo- and shape-selective oxidation of thiols to disulfides and, more significantly, the rapid and sustained removal of toxic H(2)S via H(2)S + 1/2 O(2) → 1/8 S(8) + H(2)O (4000 turnovers in <20 h), the POM or the MOF alone is catalytically slow or inactive. Three arguments are consistent with the catalytic reactions taking place inside the pores. POM activation by encapsulation in the MOF likely involves electrostatic interactions between the two components resulting in a higher reduction potential of the POM.

On the quantification of intracellular proteins in multifluorescence‐labeled rat brain slices using slide‐based cytometry

In several brain regions, a subpopulation of neurons exists being characterized by the expression of a peculiar form of extracellular matrix, a so-called perineuronal net (PNN). We have previously shown that the PNN can bind large amounts of iron due to its polyanionic charge. Because free iron can generate reactive oxygen species thus being potentially toxic, the PNN may have a protective function by "scavenging" this free iron. Because of this ability, we have hypothesized that PNN-related neurons have an altered iron-specific metabolism. Thus, to compare the intracellular concentrations of iron containing proteins, specifically, the iron storage protein ferritin H between neurons with and without a PNN, we have used slide-based cytometry with image-based threshold-boundary cell detection on brain sections. In tissue sections, the integrity of the extracellular matrix, especially the characteristic PNNs, is preserved, which is necessary for the identification of the two neuronal subpopulations. A multilabeling approach was chosen to select neurons (neuronal marker NeuN), to classify the neurons according to their subtype (matrix marker Wisteria floribunda agglutinin), and to quantify the protein concentration (protein marker). Using this novel method, we were able to detect a relative difference in protein concentration as low as 12% between the two subpopulations of neurons in the neuronal population of the rat parietal cortex.

The factors affecting on the assembly of Ag–H2biim system: size, charge or shape of polyanions?

By introducing different polyoxotungstates into the Ag–H2biim system, four new compounds with distinct architectures, Ag2(H2biim)4(W6O19)·2H2O (1), Ag6(H2biim)6(SiW12O40)(OH)2·2H2O (2), Ag6(H2biim)6(PW12O40)(OH)3·H2O (3) and Ag6(H2biim)6(P2W18O62)·12H2O (4) (H2biim = 2,2′-biimidazole), have been hydrothermally synthesized, and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, the Lindqvist type polyoxotungstate {W6} combines with the chelate Ag–H2biim complex forming a discrete “dumbbell-like” motif. Isostructural compounds 2 and 3 are obtained by introducing Keggin polyoxotungstates ({SiW12} and {PW12}, respectively), which show a 2D layer structure. The 2D layers parallel each other to form a 3D supramolecular framework. The larger Wells–Dawson polyoxotungstate {P2W18} directs the formation of compound 4, in which one 2D layer is the inversion of the neighboring ones. Furthermore, there exist infinite Ag chains in compounds 2–4, which are quite unusual in POM-based compounds. The distinction among the final four architectures is ascribed to the structure-directing effect of different polyanions. The electrochemical properties of compounds 1–4 are studied. In addition, the antibacterial properties of the four compounds against negative Escherichia coli (E. coli) and positive Staphylococcus aureus are investigated.

Adipocytokine Orosomucoid Integrates Inflammatory and Metabolic Signals to Preserve Energy Homeostasis by Resolving Immoderate Inflammation

Orosomucoid (ORM), also called alpha-1 acid glycoprotein, is an abundant plasma protein that is an immunomodulator induced by stressful conditions such as infections. In this study, we reveal that Orm is induced selectively in the adipose tissue of obese mice to suppress excess inflammation that otherwise disturbs energy homeostasis. Adipose Orm levels were elevated by metabolic signals, including insulin, high glucose, and free fatty acid, as well as by the proinflammatory cytokine tumor necrosis factor-alpha, which is found in increased levels in the adipose tissue of morbid obese subjects. In both adipocytes and macrophages, ORM suppressed proinflammatory gene expression and pathways such as NF-kappaB and mitogen-activated protein kinase signalings and reactive oxygen species generation. Concomitantly, ORM relieved hyperglycemia-induced insulin resistance as well as tumor necrosis factor-alpha-mediated lipolysis in adipocytes. Accordingly, ORM improved glucose and insulin tolerance in obese and diabetic db/db mice. Taken together, our results suggest that ORM integrates inflammatory and metabolic signals to modulate immune responses to protect adipose tissue from excessive inflammation and thereby from metabolic dysfunction.

Third generation of focusing: Gel matrices with immobilized cation gradients

A novel method is reviewed here for separation of polyanions, based not on conventional zone electrophoretic means, but on a "steady-state" process by which said polyanions are driven to stationary zones along the migration path against a gradient of positive charges affixed to the neutral polyacrylamide matrix. As the total negative surface charge of such polyanions matches the surrounding charge density of the matrix, they stop migrating and remain stationary, as typical of steady-state separation techniques. This technique has been successfully applied to SDS-protein micelles, DNAs, RNAs and heparins, with remarkable separations, often much superior than those obtained in conventional techniques. Additionally, by exploiting constant plateaus of charges, rather than gradients, it is possible to amplify the separation between species having closely spaced charge densities. This technique resembles a classical IEF process, with the proviso that the polyanions cannot be applied at any position along the gel matrix, but only at the point of low (or zero) charge density. The merits and limits of the technique are assessed.

The systemic delivery of siRNAs by a cell penetrating peptide, low molecular weight protamine

Small interfering RNAs (siRNAs), used for specific down-regulation of targeted genes, have garnered considerable interest as an attractive new class of drugs for broad clinical applications. The polyanionic charges carried by these siRNAs, however, restrain cellular uptake and consequently limit effects on gene regulation. Herein the authors describe a peptide/siRNA complex containing the cell penetrating peptide derived from natural protamine, termed low molecular weight protamine (LMWP), for the treatment of cancer. Fluorescently-tagged siRNAs were localized with the peptide in the cytoplasm shortly after incubation of LMWP/siRNA complex with carcinoma cells. The increased cell uptake of siRNA that was achieved using the LMWP resulted in significant down-regulation of model protein luciferase as well as therapeutic cancer target, vascular endothelial growth factor (VEGF) expression. In vivo studies with tumor-bearing mice further demonstrated that the peptide could carry and localize siRNA inside tumors and inhibit the expression of VEGF through systemic application of the peptide complex, thereby suppressing tumor growth. In addition, no detectable increase in the serum level of inflammatory cytokines including interferon (IFN)-α and interleukin (IL)-12 was observed under the LMWP/siRNA complex treatment, indicating systemic delivery of LMWP/siRNA did not exert measurable immunostimulatory effect. The LMWP-based systemic delivery method could be a reliable and safe approach to maximize effectiveness of therapeutic siRNA for treatment of cancer and other diseases.

Pharmacokinetics and Pharmacodynamics of Oral Heparin Solid Dosage Form in Healthy Human Subjects.

Heparin is not orally absorbed, presumably because of its size and polyanionic charge and hence is administered parenterally, either by continuous or intermittent infusion or by subcutaneous (SC) injection. However, a formulation that would result in absorption of heparin after oral administration would provide an attractive alternative to parenteral heparin. In that regard several attempts to develop effective non-parenteral heparin formulations have been reported, but they have met with limited success. The present investigation determined the molecular structure, pharmacokinetic (PK), and pharmacodynamic (PD) profiles of oral unfractionated heparin (UFH) containing oral absorption enhancer Sodium N-[8-(2-hydroxybenzoyl) amino] caprylate, salcaprozate sodium (SNAC) and assessed the safety and tolerability of orally dosed heparin solid dosage form versus other routes. Sixteen healthy men were included in this single-dose, three-way crossover, randomized, open-label study. The different arms of the study were as follow: Treatment A- Subjects randomized to Treatment A received two capsules of UFH/SNAC soft gelatin capsules for a total dose of 75,000 U heparin sodium with 150 mL of water; Treatment B: Subjects randomized to Treatment B received 1 mL of heparin sodium USP parenteral 10,000 U/mL via SC injection; Treatment C: Subjects randomized to receive 75,000 U heparin sodium milled powder for oral solution with 150 mL of water; and Treatment D: Subjects randomized to receive 0.5 mL of heparin sodium USP parenteral 5,000 U/mL via IV bolus. Each subject was randomly assigned to receive three of the four treatments so that a total of 12 subjects received each treatment. To characterize the PK of SNAC after oral heparin/SNAC administration and the PD of heparin following the administration of heparin IV, SC, PO alone and PO as heparin/SNAC, 21 blood samples were drawn from all of the subjects receiving treatment A, B, C, and D at the following time points: within 30 minutes pre-dose, at 2, 5, 10, 15, 20, 25, 30, 35, 40, 45 minutes, and at 1,1.5, 2, 2.5, 3, 3.5, 4, 5, 6, and 8 hours post-dose. Blood was drawn into sodium citrate tubes for assessment of anti-factor Xa, anti-factor IIa, aPTT, and SNAC. Disaccharide compositional analysis was performed using capillary high-performance liquid chromatography with electrospray ionization mass spectrometry detection. The PD of heparin was obtained from analysis of plasma anti-factor Xa, anti-factor IIa, aPTT, and total tissue factor pathway inhibitor (TFPI) data. The molecular weight properties and the disaccharide composition of orally administered UFH/SNAC and parenterally administered UFH are identical and consistent with the starting standard UFH administered and achieved anti-factor Xa: anti-factor IIa of 1:1. This is the first true pharmacokinetic study to measure the chemical compositions of heparin administered by different routes.

Delivery of different length poly( l-lysine)-conjugated ODN to HepG2 cells using N-stearyllactobionamide-modified liposomes and their enhanced cellular biological effects

Short (14–20-mer range) synthetic oligodeoxynucleotides (ODNs) allow specific modulation of cellular gene expression at various stages, thus providing a versatile tool for fundamental studies and a rational approach to anticancer chemotherapy. However, several problems, such as metabolic stability, efficient cell internalization of ODNs and their efficient entrapment into liposomes continue to markedly limit this approach. To improve the target specificity and biological activity of ODN, three different length of poly( l-lysine) (PLL) were conjugated to ODN and these conjugates were encapsulated in N-stearyllactobionamide (N-SLBA)-modified liposomes, N-SLBA is a ligand for the asialoglycoprotein receptor. Then, we investigated their effects on cell cycle and survivin protein levels of HepG2 cells. The results showed that the encapsulation efficiency was improved because the polycationic charges of PLL neutralized the polyanionic charges of ODN. Among them, PLL ( M W 2000 and 10,000)-conjugated ODN encapsulated in N-SLBA liposomes induced apoptosis of HepG2 cells and highly inhibited survivin gene expression.

Cationic charge-preferential IgG reabsorption in the renal proximal tubules

The brush border of the renal proximal tubules has a polyanionic charge. Since immunoglobulin G (IgG) molecules have a wide range of charge diversity, reabsorption of urinary IgG molecules are supposed to be influenced by the electrostatic interaction. Charge diversity of serum and urinary IgG molecules in patients with various renal diseases (N= 12) and premature neonates (N= 3) were analyzed by isoelectric focusing and Immunoblotting. In patients with glomerular diseases, urinary IgG was solely composed of neutral and anionic IgG, whereas that of the cationic part (isoelectric point >8) was not observed. By contrast, in patients with proximal tubular diseases (Dent's disease and idiopathic Fanconi syndrome), the proportion of the cationic IgG was similar to that of serum IgG. In addition, the cationic part of IgG in the urine was found in the neonates with a gestational age of 28 and 31 weeks, but not found in those of 35 weeks. The results suggest that renal proximal tubules reabsorb the urinary IgG in a cationic preferential way, and this mechanism requires renal maturation.