Dextran Derivatives Research Articles

Reactive Maleimido Dextran Thin Films for Cysteine-Containing Surfaces Adsorbing BSA

The modification of surfaces by functional coatings or postmodification of films to control the adsorption of bovine serum albumin (BSA) is carried out. Surface functionalization with maleimido groups is achieved by spin coating of dextran derivatives. The layers are stabilized on the support material during thermal treatment or cross-linking. The thin films are characterized by atomic force microscopy, quartz crystal microbalance, FTIR spectroscopy, and X-ray photoelectron spectroscopy. Surface morphology, hydrophobicity, swelling behavior, and reactivity of dextran furfuryl carbamate bismaleimide adduct are suitable for the preparation of surfaces containing cysteine by thiol-ene reaction. The different functional surfaces obtained are investigated regarding their BSA adsorption behavior. Up to 9 mg m−2 of BSA are adsorbed on the nanorough, hydrophilized films at different pH values (4, 6, and 8.5) and thus a blocking layer can be obtained. The BSA layer may resist nonspecific adsorption of biological molecules and can be interesting for prevention of biofilm formation on medical devices.

Interaction of dextran derivatives with lipid monolayers and the consequential modulation of the film properties

Polysaccharides have been associated with various biological functions through their binding to membranes, but their specific role is still under debate. The aim of this work was to study the interaction of cationic and anionic polysaccharides with anionic and zwitterionic monolayers, at different subphase compositions, thus analyzing the influence of electrostatics on the interaction. The consequent effect of the polymer-lipid binding on the film properties was studied, with special interest in monolayer dynamics. The results indicate that electrostatic interactions play an important role in polymer-membrane affinity, and that the polymers formed a sub-layer, which increased the shear viscosity of the interface. The interacting polymer, even when it did not penetrate the lipid film, induced a polymer-like behavior of the monolayer regarding its dynamics: the whole film (polymer+lipid) became very viscous. As a consequence, the dynamic of the membrane was affected, thus inducing changes in the film topography, although the energetics for phase transition and the stability of each phase were modified slightly or not at all.

Influence of molecular weight and structure on diffusion rates and mechanisms of dextran polyelectrolyte complexes

The release profiles of fluorescein isothiocyanate-dextran (FD) at various molecular weights (20–500kDa) and the swelling behaviors of polyelectrolyte complex-forming tablets were investigated. Four types of tablets were prepared using different combinations of the following chemicals: carboxymethyl dextran (CMD), dextran sulfate (DS), 2-diethylaminoethyl dextran (EA), and 2-hydroxypropyltrimethylammonium dextran (CDC). Release tests were conducted via the rotating basket method at pH 6.8. Swelling behaviors were analyzed via the front movement method. For all FDs, release rates decreased with decreasing density of charged groups in the matrix, as follows: CMD-EA, CMD-CDC, DS-EA, and DS-CDC. Front movement profiles showed that the dried core disappeared within 3h, leaving the swollen matrix. Results revealed that the tablets rapidly formed hydrated matrices, with release of the incorporated FDs by diffusion and erosion. The tablets successfully released the macromolecules, and we determined that the release rates could be controlled with a combination of dextran derivatives.

Radiation synthesis of biocompatible hydrogels of dextran methacrylate

The aim of this work was to synthesize biocompatible dextran-based hydrogels through crosslinking initiated by ionizing radiation. A series of derivatives of dextran has been synthesized by coupling of methacrylated glycidyl to the structure of this polysaccharide, yielding dextran methacrylate (Dex-MA) of the degree of methacrylate substitution (DS) up to 1.13 as characterised by FTIR and NMR spectroscopy. Chemically crosslinked hydrogels were formed by electron-beam irradiation of Dex-MA in aqueous solution in the absence of low-molecular-weight additives such as catalysts, monomers or crosslinking agents. Crosslinking of Dex-MA in aqueous solutions of 20g/l and above was an efficient process, the gels were formed at doses as low as 0.5 kGy (experiments conducted up to 100 kGy) and were characterised by high content of insoluble fraction (70–100%). Due to high crosslinking density the equilibrium degree of swelling of fabricated gels was controlled principally by the initial concentration of Dex-MA solution subjected to irradiation, and it was in the range of 20 to over 100g of water absorbed by gram of gel. Cytocompatibility of hydrogels was examined using XTT assay through evaluation of the cell viability being in indirect contact with hydrogels. The results indicated that hydrogels of Dex-MA of the average DS below 1 were not cytotoxic. Altogether, our data demonstrate that irradiation of methacrylated dextran in aqueous solution is an efficient method of fabrication of biocompatible hydrogels, which applications in regeneration medicine are anticipated.

Antimicrobial activity of chemically modified dextran derivatives

Cationic amphiphilic dextran derivatives with a long alkyl group attached to the reductive end of the polysaccharide chain and quaternary ammonium groups attached as pendent groups to the main dextran backbone were synthesized and tested for their antimicrobial properties against several bacteria and fungi strains. Dependence of antimicrobial activity on both polymer chemical composition (dextran molar mass, length of end alkyl group and chemical structure of ammonium groups) and type of microbes was highlighted by disc-diffusion method (diameter of inhibition zone) and broth microdilution method (minimum inhibitory concentrations). Polymers had antimicrobial activity for all strains studied, except for Pseudomonas aeruginosa ATCC 27853. The best activity against Staphylococcus aureus (Minimun Inhibitory Concentration 60μg/mL) was provided by polymers obtained from dextran with lower molecular mass (Mn=4500), C12H25 or C18H37 end groups, and N,N-dimethyl-N-benzylammonium pendent groups.

Synthesis and film formation of furfuryl- and maleimido carbonic acid derivatives of dextran

Carbonic acid derivatives of dextran possessing furfuryl- and maleimido moieties were synthesized and processed into thin films by spin coating. First, products with different degrees of substitution (DS) of up to 3.0 and substitution patterns were obtained and characterized by NMR- and FTIR spectroscopy, as well as elemental analysis. Thin films possessing maleimide groups were obtained by spin coating of maleimido dextran (furan-protected) and dextran furfuryl carbamate that was converted with bismaleimide. The removal of the protecting group (furan) on the thin film was monitored by QCM-D and compared with gravimetric analysis of the bulk material. Film morphology and wettability were determined by means of AFM and contact angle measurements.

Bioactive polysaccharide-based pH-sensitive polymers for cytoplasmic delivery of antigen and activation of antigen-specific immunity.

For establishment of cancer immunotherapy, antigen carriers are needed which have functions not only to deliver antigen into cytosol of dendritic cells (DCs), which induces antigen-specific cellular immune responses, but also to activate DCs. We previously reported cytoplasmic delivery of antigen using liposomes modified with pH-sensitive polymers such as carboxylated poly(glycidol)s or dextran. Modification using these polymers provides stable liposomes with pH-sensitive fusogenic/membrane-disruptive ability. For this study, bioactive polysaccharide-based pH-sensitive polymers were constructed to achieve not only cytoplasmic delivery of antigen but also activation of DCs. Curdlan and mannan were used as bioactive polysaccharides because they are known to activate DCs via their respective interactions with Dectin-1 and Dectin-2. Carboxylated curdlan and mannan promoted Th1 cytokine production from DCs, indicating the activation of DCs by these polysaccharide derivatives. These polymer-modified liposomes released their contents at weakly acidic pH and delivered model antigenic proteins into cytosol of DCs. Subcutaneous administration of curdlan derivative-modified or mannan derivative-modified liposomes induced strong antigen-specific immune responses and stronger antitumor effects than those of liposomes modified with dextran derivative. Therefore, bioactive polysaccharide-modified liposomes that achieve both cytoplasmic delivery of antigen and activation of DCs are promising for cancer immunotherapy.

In vivo imaging of systemic transport and elimination of xenobiotics and endogenous molecules in mice

We describe a two-photon microscopy-based method to evaluate the in vivo systemic transport of compounds. This method comprises imaging of the intact liver, kidney and intestine, the main organs responsible for uptake and elimination of xenobiotics and endogenous molecules. The image quality of the acquired movies was sufficient to distinguish subcellular structures like organelles and vesicles. Quantification of the movement of fluorescent dextran and fluorescent cholic acid derivatives in different organs and their sub-compartments over time revealed significant dynamic differences. Calculated half-lives were similar in the capillaries of all investigated organs but differed in the specific sub-compartments, such as parenchymal cells and bile canaliculi of the liver, glomeruli, proximal and distal tubules of the kidney and lymph vessels (lacteals) of the small intestine. Moreover, tools to image immune cells, which can influence transport processes in inflamed tissues, are described. This powerful approach provides new possibilities for the analysis of compound transport in multiple organs and can support physiologically based pharmacokinetic modeling, in order to obtain more precise predictions at the whole body scale.

Achievement of Release Mode under Combinational Stimuli by Acid and Reduction for Reduced Adverse Effect in Antitumor Efficacy

To reduce the adverse effect in antitumor therapy, a superparamagnetic doxorubicin (DOX)‐loaded nanogel with the release mode under the combinational stimuli present in intracellular environments of solid tumors is presented. Dextran is first modified to involve both thiol groups and carboxyl groups. The dextran derivative is then covalently coupled with previously thiolated and aminated magnetic iron oxide nanoparticles through both the linkage of disulfide bond and electrostatic interaction. Upon the optimal conditions, a nanogel is fabricated via the dual cross‐linking. The nanogel features the targeting release under combinational stimuli by acid and reduction environment with low release level in healthy tissues. In vitro release profiles reveal these release modes as expected. Cytotoxicity assay exhibits a much lower toxicity of the DOX‐loaded nanogel to COS‐7 cells than free DOX. Prussian blue staining and confocal laser scanning microscopy observation reveal the cellular uptake and subcellular release in nuclei of the nanogel. In vivo study exhibits that the nanogel presented 67.3% of inhibition rate of tumor growth and a healthy appearance. The present nanogel expresses high efficacy with low systemic adverse effect and is thus believed to offer a promising candidate for highly effective cancer therapy.image

Novel dextran derivatives with unconventional structure formed in an efficient one-pot reaction

An efficient one-pot synthesis of new dextran derivatives is described. The functional groups of β-alanine, i.e., the carboxyl- and amine group, are converted independently in one-step by iminium chloride to form products with a single substituent. The dextran N-[(dimethylamino)methylene]-β-alanine ester is formed selectively. The structure of the resulting polymers is unambiguously determined by means of NMR- and FTIR-spectroscopy and elemental analysis.

In situ supramolecular hydrogel based on hyaluronic acid and dextran derivatives as cell scaffold.

In this study, hyaluronic acid-β-cyclodextrin conjugate (HA-CD) and dextran-2-naphthylacetic acid conjugate (Dex-NAA) were synthesized as two gelators. The degrees of substitution (DS) of these two gelators were determined to be 15.5 and 7.4%, respectively. Taking advantages of the strong and selective host-guest interaction between β-CD and 2-NAA, the mixture of two gelators could form supramolecular hydrogel in situ. Moreover, the pore size, gelation time, swelling ratio as well as modulus of the hydrogel could be adjusted by simply varying the contents of HA-CD and Dex-NAA. NIH/3T3 cells that entrapped in hydrogel grew well as compared with that cultured in plates, indicating a favorable cytocompatibility of the hydrogel. Collectively, the results demonstrated that the HA-Dex hydrogel could potentially be applied in tissue engineering as cell scaffold. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2263-2270, 2016.

Matrix Regeneration Therapy: A Case Series of Corneal Neurotrophic Ulcers.

Treating corneal neurotrophic ulcers is challenging. Topical application of matrix regeneration therapy (RGTA), which is a dextran derivative polymer and heparan sulfate analog, is a promising regenerative therapy and an alternative or additional therapeutic regimen when corneal healing is compromised. The aim of this study was to evaluate the efficacy of RGTA (Cacicol) in the treatment of 6 patients with severe neurotrophic ulcers. We present an uncontrolled prospective case series of 6 patients (6 eyes) with severe corneal neurotrophic ulcers. Patients were treated with topical RGTA at a dose of 1 drop every second day. The main outcome measure was complete corneal epithelialization. We measured corneal thickness by anterior segment swept-source optical coherence tomography. Two patients (33%) showed complete corneal healing, one at 6 weeks and the other at 10 weeks. Treatment was considered failure in 4 patients (67%), and 1 patient had corneal perforation. None of the patients showed improvement in best-corrected visual acuity. There were no RGTA-related local or systemic side effects. Based on previous studies, RGTA seems to be a promising therapeutic agent for controlling ocular surface inflammation and promoting corneal healing. In this study, the efficacy of RGTA did not match the encouraging results from previous reports.

Reduction-sensitive amphiphilic dextran derivatives as theranostic nanocarriers for chemotherapy and MR imaging

Reduction-sensitive, amphiphilic dextran derivatives were developed from disulfide-linked dextran-g-poly-(N-ε-carbobenzyloxy-l-lysine) graft polymer (Dex-g-SS-PZLL), and used as theranostic nanocarriers for chemotherapy and MR imaging.

Determination of residual dextran sulfate in protein products by SEC-HPLC.

Dextran sulfate is a polyanionic derivative of dextran, produced by esterification of dextran with chlorosulphonic acid. Dextran sulfate with an average molecular weight of 8000Da can be added to the cell culture to inhibit binding of proteins to cells, increasing cellular growth and productivity. Residual dextran sulfate levels must be monitored during the purification process development to insure clearance. A size-exclusion chromatography based HPLC assay has been developed for the separation and quantitation of dextran sulfate in a highly concentrated purified protein drug substance sample. Trichloroacetic acid (TCA) was used to precipitate the protein and separate the dextran sulfate. Detection and quantitation of dextran sulfate was achieved by post column reaction with dimethylene blue to form a metachromatic complex that absorbs visible light at 530nm. The quantitation limit (LOQ) was determined to be 1.5μg/mL dextran sulfate in high concentration protein samples.

Biocompatible dextran-covered nanoparticles produced by Activator Generated by Electron Transfer Atom Transfer Radical Polymerization in miniemulsion

Abstract Aiming to prepare potentially biocompatible dextran-covered nanoparticles (NPs), the use of a pharmaceutically acceptable oil (Miglyol 810, M810—a medium chain saturated triglyceride) as co-stabilizer and of amphiphilic dextran derivatives (DexPτ) as stabilizers was investigated for Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (AGET ATRP) of methyl methacrylate in miniemulsion. We showed that, as compared to several oils, M810 was the most suitable co-stabilizer. Indeed, it efficiently prevented diffusional degradation and contributed to solubilize ATRP catalytic systems in organic phase (methyl methacrylate + 5 vol% of co-stabilizer). Better control over polymerization and nano-objects size was achieved for polymerization with M810 compared to a standard co-stabilizer (hexadecane). Indeed, with the appropriate formulation conditions, NPs size was very similar to the one of initial emulsion nanodroplets and more than 85% of the initial DexPτ amount was adsorbed at NPs surface. A convenient procedure to eliminate copper from the finals NPs was also experienced.

Salmonella Disrupts Host Endocytic Trafficking by SopD2-Mediated Inhibition of Rab7.

Intracellular bacterial pathogens of a diverse nature share the ability to evade host immunity by impairing trafficking of endocytic cargo to lysosomes for degradation, a process that is poorly understood. Here, we show that the Salmonella enterica type 3 secreted effector SopD2 mediates this process by binding the host regulatory GTPase Rab7 and inhibiting its nucleotide exchange. Consequently, this limits Rab7 interaction with its dynein- and kinesin-binding effectors RILP and FYCO1 and thereby disrupts host-driven regulation of microtubule motors. Our study identifies a bacterial effector capable of directly binding and thereby modulating Rab7 activity and a mechanism of endocytic trafficking disruption that may provide insight into the pathogenesis of other bacteria. Additionally, we provide a powerful tool for the study of Rab7 function, and a potential therapeutic target.

Ionic dextran derivatives for removal of Fastac 10 EC from its aqueous emulsions

Separation studies of Fastac 10 EC from model emulsions by cationic polysaccharides were followed by UV–vis spectroscopy and zeta potential measurements. Floc size measurements at the optimum polycation dose were also carried out using laser diffraction technology. The investigated polyelectrolytes contained various amounts of quaternary ammonium salt groups, N-ethyl(octyl)-N,N-dimethyl-2-hydroxypropyl ammonium chloride, attached to a dextran backbone. The effects of polycation dose, its charge density, emulsion pH and pesticide concentration on the flocculation performance were studied. The pesticide removal results (UV–vis spectroscopy) show that the optimum polycation dose decreased with increasing polymer charge density and the emulsion pH and increased with increasing pesticide concentration. The zeta potential values close to zero at the optimum polymer dose point to contribution, mainly, from charge neutralization mechanism for the flocculation process. The flocs size increase with increasing pesticide concentration was also observed.

Biophysical properties of carboxymethyl derivatives of mannan and dextran

Mannan from Candida albicans, dextran from Leuconostoc spp. and their carboxymethyl (CM)-derivatives were tested on antioxidant and thrombolytic activities. As antioxidant tests, protection of liposomes against OH radicals and reducing power assay were used. Dextran and mannan protected liposomes in dose-dependent manner. Carboxymethylation significantly increased antioxidant properties of both CM-derivatives up to concentration of 10mg/mL, higher concentrations did not change the protection of liposomes. The reducing power of CM-mannan (DS 0.92) was significantly lower (P<0.05) than underivatized mannan. No reductive activity was found for dextran and CM-dextran. All CM-derivatives demonstrated statistically significant increasing activity compared with underivatized polysaccharides. The highest thrombolytic activity was found using CM-mannan (DS 0.92). The clot lysis here amounted to 68.78±6.52% compared with 0.9% NaCl control (18.3±6.3%). Three-dimensional surface profiles of mannan, dextran, and their CM-derivatives were compared by atomic force microscopy.

Long-Term Stability of Glucose Responsive Dextran Methacrylate-Concanavalin A Methacrylamide Gels as Part of an Implantable Artificial Pancreas

A closed loop implantable insulin delivery device that delivers insulin to the peritoneum in an automated fashion linked to changing glucose levels has been developed and previously tested in diabetic rats and pigs. The device delivers insulin via a glucose-sensitive gel that comprises of photopolymerized acrylic derivatives of dextran and concanavalin A and acts as both a sensor and controller of the amount of insulin released. In this work the long-term stability of these acrylic polymerized gels and also dextran and concanavalin A mixtures has been shown at 20°C and 37°C by rheological characterization when stored with and without 0.1% w/w glucose. Acrylic gels were found to have a stable complex viscosity for over 730 days at these temperatures indicating that over time they do not undergo degradation. Mixtures and polymerized gels were also dialyzed in the presence of chymotrypsin, which is present in the peritoneum (device implant site) to assess gel integrity across a range of pore size dialysis membranes. Polymerized acrylic gels contained in dialysis membranes of 50 kDa were found to be resistant to degradation over a long time (>500 days). These results show that these gels would be ideal candidates as part of an implantable insulin delivery device.

Preparation and characterization of liposomes coated with DEAE-Dextran

Abstract Liposomes as effective drug delivery vehicles have played significant role in therapeutics. However physicochemical instability of liposomes reduces its possibilities and potentials to be used in drug delivery systems. The present work describes the stabilization of liposome via electrostatic deposition of a polycationic derivative of dextran which is Diethylaminoethyl Dextran (DEAE-Dx) on soy lecithin liposome. Liposomes were prepared by thin film hydration method. The critical vesicular concentration (CVC) of lecithin was found at 0.1% (w/v) through surface tension analysis. Zeta potential and differential scanning calorimetry (DSC) measurements were obtained to study the interaction between DEAE-Dx and liposomes. The zeta potential of liposomes changed from negative value to increasingly positive after addition of DEAE-Dx. This confirmed the coating of liposomes by DEAE-Dx. Stability of the DEAE-Dx liposome suspension was studied through particle size and zeta potential measurements over a period of 35 days. DEAE-Dx liposome suspension was found more stable than the uncoated liposomes suspension. The optimum concentration of DEAE-Dx incorporated with liposome was observed at 0.02% (w/v) compared to other examined concentration of DEAE-Dx. Encapsulation efficiency of DEAE-Dx coated liposome loaded with curcumin shows slightly higher value compared to the uncoated ones.