Cat flu: Broad spectrum polymeric antivirals

Feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV) are considered as main causes of feline upper respiratory tract disease and the most common clinical manifestations include rhinotracheitis, conjunctivitis, and nasal/facial ulcerations. While the primary infection is relatively mild, secondary infections pose a threat to young or immunocompromised cats and may result in a fatal outcome. In this study, we made an effort to evaluate antiviral potency of poly(sodium 4-styrenesulfonates) (PSSNa) as potent FHV-1 and FCV inhibitors for topical use. Mechanistic studies showed that PSSNa exhibits a different mechanism of action depending on target species. While PSSNa acts directly on FHV-1 particles blocking their interaction with the host's cell and preventing the infection, the antiviral potency against FCV is based on inhibition at late stages of the viral replication cycle. Altogether, PSSNa polymers are promising drug candidates to be used in the treatment and prevention of the viral upper respiratory tract disease (URTD), regardless of the cause.

Genipin crosslinked bioactive collagen/chitosan/hyaluronic acid injectable hydrogels structurally amended via covalent attachment of surface-modified silica particles

Collagen, chitosan and hyaluronic acid based multicomponent injectable and in situ gellating biomimetic hybrid materials for bone tissue engineering applications were prepared in one-step procedure. The bioactive phase in the form of surface-modified silica particles was introduced to the solutions of biopolymers and simultaneously crosslinked with genipin both the biopolymer matrix and dispersed particles at 37 °C. The novel approach presented here involved the use of silica particles which surfaces were priory functionalized with amino groups. That modification makes possible the covalent attachment of silica particles to the polymeric hydrogel network on crosslinking with genipin. That methodology is especially important as it makes possible to obtain the hybrid materials (biopolymer-silica particles) in which the problems related to the potential phase separation of mineral particles, hindering their in vivo application can be eliminated. The hybrids of various compositions were obtained and their physicochemical and biological properties were determined. The in vitro experiments performed under simulated body fluid conditions revealed that the amino-functionalized silica particles covalently attached to the biopolymeric network are still bioactive. Finally, the in vitro cell culture studies shown that the materials developed are biocompatible as they supported MG-63 cells adhesion, proliferation as well as Alkaline phosphatase (ALP) expression.

The antiatherogenic effect of new biocompatible cationically modified polysaccharides: chitosan and pullulan - the comparison study

Pullulan and chitosan are biocompatible polysaccharides obtained from natural sources with many biomedical applications. Cationically modified polymers, such as chitosan and pullulan after covalent attachment of glycidyltrimethylammonium chloride (GTMAC), showed beneficial biological properties. In the present study, it was clearly demonstrated and confirmed that both cationically modified polysaccharides (chitosan-GTMAC and pullulan-GTMAC) have the antiatherosclerotic potential by inhibition of atherosclerotic plaque development and controlling the expression of genes involved in lipid metabolism. It has also been shown that the cationically modified chitosan (HTCC) at a dose of 200 mg/kg b.w./day in male apoE-knockout mice acted as hypolipidaemic agent. It was observed that a statistically significant decrease in low-density lipoprotein (LDL) cholesterol level by 32% occurred under the influence of HTCC at a dose of 200 mg/kg b.w./day after 16 weeks of the experiment compared to the control group of apoE(-/-) mice. Moreover, under the influence of cationically modified chitosan administered orally to female apoE-knockout mice at a dose of 300 mg/kg b.w./day for 18 weeks a statistically significant reduction by 33% in the area of atherosclerotic plaque was observed compared to the control group, i.e., apoE-knockout mice whose diet was not supplemented with the cationically modified polysaccharide. Current in vivo studies connected with cationically modified pullulan showed a statistically significant 22% reduction of the area of atherosclerotic plaque in the apoE(-/-) mice fed with a feed containing Pull-GTMAC at a dose of 500 mg/kg b.w./day for 18 weeks in comparison to the control group of apoE-knockout mice. In the in vitro studies it was also shown that cationically modified chitosan acted therapeutically by reduction of the level of the expression of human 3-hydroxy-3-methylglutaryl-CoA reductase (human HMG-CoAR) after 24 hours of incubation with HepG2 cells. However, cationically modified pullulan did not show this effect in the experiment on HepG2 cell line. On the other hand, Pull-GTMAC caused a statistically significant increase in insulin induced gene 1 (INSIG1) expression and increase in mRNA level of LDL receptor in brown fat tissue of female apoE-knockout mice after oral administration with feed at a dose of 300 mg/kg b.w./day for 18 weeks in comparison to the control group of apoE(-/-) mice, that was crearly demonstrated the effect of cationically modified pullulan on the expression of lipid metabolism genes in in vivo conditions. In the present article we have shown for first time that cationically modified pullulan and chitosan have some similarities in their antiatherogenic action but there are also some minor differences in mechanism of their effect on lipid metabolism.

Comparison of Effects of Anti-thrombin Aptamers HD1 and HD22 on Aggregation of Human Platelets, Thrombin Generation, Fibrin Formation, and Thrombus Formation Under Flow Conditions

HD1 and HD22 are two of the most-studied aptamers binding to thrombin exosite I and exosite, respectively. To complete of their pharmacological profiles, the effects of HD1 and HD22 on thrombin-, ristocetin-, and collagen-induced human platelet aggregation, on thrombin generation and fibrin formation in human plasma, as well as on thrombus formation in human whole blood under flow conditions were assessed. The dissociation constants for HD1 and HD22 complexes with thrombin in simulated plasma ionic buffer were also evaluated. HD1 was more potent than HD22 in terms of inhibiting thrombin-induced platelet aggregation in platelet-rich plasma (PRP; 0.05-3 μM) and in washed platelets (WPs; 0.005-3 μM): approximately 8.31% (±6.99% SD) and 89.53% (±11.38% SD) for HD1 (0.5 μM) and HD22 (0.5 μM), respectively. Neither HD1 nor HD22 (3 μM) did influence platelets aggregation induced by collagen. Both of them inhibited ristocetin-induced aggregation in PRP. Surprisingly, HD1 and HD22 aptamers (3 μM) potentiated ristocetin-induced platelet aggregation in WP. HD1 reduced thrombin generation in a concentration-dependent manner [ETP at 3 μM: 1677.53 ± 55.77 (nM⋅min) vs. control 2271.71 ± 423.66 (nM⋅min)], inhibited fibrin formation (lag time at 3 μM: 33.70 min ± 8.01 min vs. control 7.91 min ± 0.91 min) and reduced thrombus formation under flow conditions [AUC30 at 3 μM: 758.30 ± 344.23 (kPa⋅min) vs. control 1553.84 ± 118.03 (kPa⋅min)]. HD22 (3 μM) also delayed thrombin generation but increased the thrombin peak. HD22 (3 μM) shortened the lag time of fibrin generation (5.40 min ± 0.26 min vs. control 7.58 min ± 1.14 min) but did not modify thrombus formation (3, 15 μM). K d values for the HD1 complex with thrombin was higher (257.8 ± 15.0 nM) than the K d for HD22 (97.6 ± 2.2 nM). In conclusion, HD1 but not HD22 represents a potent anti-thrombotic agent, confirming the major role of exosite I in the action of thrombin. HD22 aptamer blocking exosite II displays weaker anti-platelet and anti-coagulant activity, with surprising activating effects on thrombin and fibrin generation most likely induced by HD22-induced allosteric changes in thrombin dynamic structure.

The neutralization of heparan sulfate by heparin-binding copolymer as a potential therapeutic target

Besides regulating ligand–receptor and cell–cell interactions, heparan sulfate (HS) may participate in the development of many diseases, such as cancer, bacterial or viral infections, and their complications, like bleeding or inflammation. In these cases, the neutralization of HS could be a potential therapeutic target. The heparin-binding copolymer (HBC, PEG41-PMAPTAC53) was previously reported by us as a fully synthetic compound for efficient and safe neutralization of heparins and synthetic anticoagulants. In a search for molecular antagonists of HS, we examined the activity of HBC as an HS inhibitor both in vitro and in vivo and characterized HBC/HS complexes. Using a colorimetric Azure A method, isothermal titration calorimetry and dynamic light scattering techniques we found that HBC binds HS by forming complexes below 200 nm with less than 1 : 1 stoichiometry. We confirmed the HBC inhibitory effect in rats by measuring activated partial thromboplastin time, prothrombin time, anti-factor Xa activity, anti-factor IIa activity, and platelet aggregation. HBC reversed the enhancement of all tested parameters caused by HS demonstrating that cationic synthetic block copolymers may have a therapeutic value in various disorders involving overproduction of HS.

The neutralization of heparan sulfate (HS) by a heparin-binding copolymer (HBC) could be a promising treating option for bacterial or viral infections or bleeding related to overproduction of HS in cancer or other diseases.

Molecular Mechanism of Polycation-Induced Pore Formation in Biomembranes

Polycations are an attractive class of macromolecules with promising applications as drug/gene carriers and biocides. The chemical structure and concentration of a polycation determine its interaction with cellular membranes and, hence, are crucial parameters for designing efficient nontoxic polycations. However, the interaction of polycations with biomembranes at the molecular level and the corresponding free-energy landscape is not well understood. In this work, we investigate the molecular mechanism of interaction between a strong polycation substituted with alkyl moieties and zwitterionic membranes via long-time-scale all-atom molecular dynamics simulations and free-energy calculations combined with Langmuir monolayer, atomic force microscopy, and calcein-release experimental measurements. We found that the membrane activity of the polycation and its ability to induce pores in the membranes can be attributed to the polycation-induced changes in the bilayer organization, such as reduced membrane thickness, increased disorder of the acyl chains, reduced packing, and electrostatic field gradients between membrane leaflets. These changes facilitate the penetration of water into the membrane and the formation of aqueous defects/pores. The calculated free-energy profiles indicate that the polycation lowers the nucleation barrier for pore opening and the free energy for pore formation in a concentration-dependent manner. Above the critical coverage of the membrane, the polycation nucleates spontaneous pores in zwitterionic membranes. Our work demonstrates the potential of combining enhanced sampling methods in MD simulations with experiments for a quantitative description of various events in the polycation-membrane interaction cycle, such as strong adsorption on the membrane due to hydrophobic and electrostatic interactions, and pore formation.

Cell proliferation induced by modified cationic dextran

The interaction between oppositely charged membranes and polycations causes cell aggregation, loss of membrane fluidity, and membrane degeneration and may cause an increase of its permeability. Unfortunately, the interaction is the reason why the use of polycations in medicine is severely limited. Therefore, in this paper, we share our observations related to the action of 40-kDa dextran modified using glycidyltrimethylammonium chloride, resulting in increased fibroblast cell proliferation. Using viability and proliferation tests [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, crystal violet, 3H-thymidine incorporation], we have observed that cationic dextran derivatives exert a positive impact on nonepithelial cell proliferation in vitro. This phenomenon has been noted for human and mouse fibroblasts and several other nonepithelial cell lines. However, the effect seems to be most pronounced for fibroblast cell lines. The presented studies allow to examine the impact of the polymer structure and the methods of its cationic modification on this newly observed phenomenon. The observation is unique because positively charged macromolecules usually exhibit high toxicity in all cell types in vitro.

Molecular Insight into Drug-Loading Capacity of PEG-PLGA Nanoparticles for Itraconazole

Nanoparticles made of amphiphilic block copolymers comprising biodegradable core-forming blocks are very attractive for the preparation of drug-delivery systems with sustained release. Their therapeutic applications are, however, hindered by low values of the drug-loading content (DLC). The compatibility between the drug and the core-forming block of the copolymer is considered the most important factor affecting the DLC value. However, the molecular picture of the hydrophobic drug-copolymer interaction is still not fully recognized. Herein, we examined this complex issue using a range of experimental techniques in combination with atomistic molecular dynamics simulations. We performed an analysis of the interaction between itraconazole, a model hydrophobic drug, and a poly(ethylene glycol)-poly(lactide- co-glycolide) (PEG-PLGA) copolymer, a biodegradable copolymer commonly used for the preparation of drug-delivery systems. Our results clearly show that the limited capacity of the PEG-PLGA nanoparticles for the accumulation of hydrophobic drugs is due to the fact that the drug molecules are located only at the water-polymer interface, whereas the interior of the PLGA core remains empty. These findings can be useful in the rational design and development of amphiphilic copolymer-based drug-delivery systems.

Tuning of elasticity and surface properties of hydrogel cell culture substrates by simple chemical approach

When designing materials for tissue engineering applications various parameters characterizing both materials and tissue have to be taken into account. The characteristics such as chemistry, elasticity, wettability, roughness and morphology of the substrate's surface have significant impact on cell behavior. The paper presents biopolymer (collagen/chitosan) based hydrogel materials with tunable elasticity and surface properties useful for fabrication of substrates for cell culture. Using simple chemical approach involving the change in concentration of crosslinking agent (genipin) and composition of the reaction mixture the hydrogels characterized with various features were obtained. Detailed analysis of morphology, topography, roughness and elasticity of surface performed using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and rheological measurements has shown that the topographical aspects and roughness parameter can be modulated in nanoscale regime (13-47 nm). Substrate's elasticity could be modified in a wide range (0.2-270 kPa). Biological in vitro studies on fibroblasts behavior revealed that the materials prepared provide satisfactory conditions for cell culture, ensuring their high viability, good adhesion and normal morphology. The genipin crosslinked collagen-chitosan hydrogels characterized by denser fiber structure, higher elasticity and lower surface roughness are the most attractive supports for fibroblasts cultivation. The results obtained indicate that the properties of the materials developed can be easily tailored to the needs of the given type of cells.

Visible-Light Photoactive, Highly Efficient Triplet Sensitizers Based on Iodinated Aza-BODIPYs: Synthesis, Photophysics and Redox Properties

A series of novel iodinated NO₂ -substituted aza-BODIPYs have been synthesized and characterized. Highly desirable photophysical and photochemical properties were induced in NO₂ -substituted aza-BODIPYs by iodination of the pyrrole rings. In particular, high values of singlet oxygen quantum yields (Φ_Δ ) ranging from 0.79 to 0.85 were measured. The photooxygenation process proceeds via a Type II mechanism under the experimental conditions applied. The compounds studied exhibited an absorption band within the so-called "therapeutic window", with λ_max located between 645 nm to 672 nm. They were non-fluorescent at room temperature with excited singlet-state lifetimes within the picosecond range as measured by femtosecond transient absorption. Nanosecond laser flash photolysis experiments revealed T₁ →T_n absorption spanning from ca. 400 nm to ca. 500 nm and allowed determination of the triplet-state lifetimes. The estimated triplet lifetimes (τ_T ) in deaerated acetonitrile ranged between 2.74 μs and 3.50 μs. As estimated by CV/DPV measurements, all iodinated aza-BODIPYs studied exhibited one irreversible oxidation and two quasi-reversible reductions processes. Estimation of the E_HOMO gave the value of -6.06 to -6.26 eV while the E_LUMO was found to be located at ca. -4.6 eV. Thermogravimetric (TGA) analysis revealed that iodinated aza-BODIPYs were stable up to approximately 300 °C. All compounds studied exhibit high photostability in toluene solution.