Mixture Of Dextran Research Articles

Microfluidic Droplet‐Based Tailorable Porous GelMA Microspheres for 3D Spatio Controllable Cell Coculture

AbstractFor the construction of accurate 3D tissue models in vitro, the 3D coculture model formed by spatio‐controlled distribution of multiple cells is essential. Despite the benefits of porous microspheres with low density, large surface area, and high permeability, exact spatio‐controlled distribution fails to appear in 3D coculture models by using porous microspheres as carriers. Herein, a facile method is proposed to construct a 3D coculture model with heterogeneous cell spatio‐tailored distribution using GelMA microspheres with customizable porosity structure and size based on droplet microfluidics in combination with placeholders. ATPS emulsions, containing two biocompatible immiscible aqueous phases of cell/Alg /dextran (Dex) mixture and polyethylene glycol (PEG) solution, are used as the templates to generate the placeholders. The micron‐sized porous GelMA microspheres are prepared by UV crosslinking of droplets prepared in microfluidic devices, followed by chelation of the placeholders. As a proof of concept, the 3D coculture hepatocellular carcinoma (HCC) model with HepG2 encapsulated outside the pores and HUVEC inside the pores is established. Noteworthy, the cells in the 3D coculture HCC model exhibit greater cell activity and proliferation, enhanced functionalities, and drug resistance than the control group. In conclusion, this straightforward method provides a novel approach for constructing 3D coculture models in vitro.

Effect of mixture microstructure/compatibility on the properties of type-A gelatin-dextran edible films

The influence of phase separation behavior on bio-based film properties has attracted more and more attention. This work investigated the effects of microstructure and compatibility of the type-A gelatin (GE)-dextran (DE) mixtures on GE-DE edible film properties. Three kinds of GE-DE edible films with different textures were prepared via modulating the microstructure and compatibility of film-forming mixtures using the method of gelation-drying, e.g., homogeneous films, microphase separated films with relatively homogeneous texture, and microphase separated films with uneven texture. The optical, mechanical, water barrier, and thermal properties of films were characterized. Results showed that microstructure and compatibility significantly affected the film properties. In general, films with DE-in-GE microstructure exhibited the best film properties, followed by films with water-in-water-in-water/bicontinuous microstructure, and then films with GE-in-DE microstructure. And homogeneous films showed the best film properties, followed by films with relatively homogeneous texture, and then films with uneven texture. The weight loss results suggested the potential of GE-DE edible films for application in cherry tomato preservation. This work provided interesting information for the design of film with fabricated microstructure and properties.

Effect of anti-adhesion agents on cytokine profile in an experimental model of postoperative intra-abdominal adhesions

Many attempts have been made to prevent peritoneal adhesions using anti-adhesion agents, barriers and other therapeutic approaches, but their efficacy has not been widely accepted. Purpose – to determine the effects of mezogel, a mixture of metronidazole, dextran, and contrykal enriched with oxygen based on the pro- and anti-inflammatory cytokine concentration in rats with simulated postoperative peritoneal adhesions. Materials and methods. A total of 90 outbred white rats, divided into three groups of 30 animals each, underwent laparotomy and mechanical injury of the small bowel wall until a drop of blood appeared. After mechanical injury of the small bowel wall, the abdominal wound in group 1 animals (control) was closed with a layered suture technique; group 2 animals (comparison) were administered one mL of mezogel into the abdominal cavity before layer-by-layer suturing; group 3 animals (experimental) were introduced one mL of a specially prepared mixture of metronidazole, dextran, and contrykal (in a ratio of 1:1:0.1, respectively) enriched with oxygen into the abdominal cavity before the laparotomy wound was closed. Each surgical intervention lasted 15–20 minutes. On days 5, 10 and 21 of the experiment interleukin (IL) 4, IL-6, IL-10 and tumour necrosis factor alpha (TNF-α) were determined in the blood by enzyme immunoassay using corresponding test kits manufactured by Bender Medsystems (Austria). Results. The levels of the anti-inflammatory cytokines IL-4 and IL-10 increased dynamically in groups 2 and 3, while group 1 showed their decrease. The proinflammatory cytokine IL-6 and TNF-α concentration decreased in the experimental and comparison groups during the study period. On day 5 in groups 2 and 3, compared to group 1, the IL-6 concentration was reduced by 28.4% (p=0.029) and 41.0% (p=0.006), respectively. Group 3 animals had a 17.6% (p=0.043) lower IL-6 level compared to group 2 animals. On days 10 and 21 a dynamic decrease in IL-6 was observed in the animals of groups 2 and 3. Group 3 animals had the lowest TNF-α, 41.9 % (p=0.001) lower than in group 1, and 31.7 % (p=0.118) lower than in group 2. There were significant strong relationships detected between IL-10 and IL-6 in all groups on day 5 of the study. Conclusions. The administration of anti-adhesion agents, mezogel and an oxygen-enriched mixture of metronidazole, dextran, and contrykal, inhibits inflammation, which is expressed as a decrease in the concentrations of IL-6 and TNF-α. These agents lead to a negative interaction of anti-inflammatory cytokines with pro-inflammatory cytokines, in particular IL-4 with IL-6 and IL-10 with IL-6, indicating a greater prophylactic effect. The experiments with laboratory animals were provided in accordance with all bioethical norms and guidelines. No conflict of interests was declared by the authors.

Determination of Viscoelastic and Physicochemical Interactions of Dextran Type Exopolysaccharides (EPS) with Different Starch Samples

In this study, the rheological properties of three distinct dextrans with different levels of (1 → 6)-linked α-D-glucose/(1 → 3)-linked α-D-glucose units from three lactic acid bacteria (LAB) strains were determined. Dextran PDER21 was further selected following the rheological measurements and its interactions with maize, wheat and waxy maize starches were determined by characterizing the viscoelastic and pasting properties of the dextran–starch mixtures. Fourier transform infrared (FTIR) spectroscopy analysis was also applied to unveil this interaction. The presence of dextran PDER21 in the standard maize starch increased the elastic behavior, while its increased amounts enhanced the elastic properties of wheat and waxy maize starches. The temperature sweep test showed the solid-like property of starch–dextran mixtures in the studied temperature range (4–70 °C). Dextran PDER21 affected the pasting properties of starches. Especially, high levels of the peak, through and final viscosity values were reached with the blends of standard maize starch–1% dextran, wheat starch–0.5% dextran and waxy maize starch–0.5% dextran PDER21. Finally, the interactions were also confirmed by FTIR analysis as no alterations in the starch FTIR spectra were observed at different levels of dextran in different starch samples.

In situ visualization of combined membrane fouling behaviors using multi-color light sheet fluorescence imaging: A study with BSA and dextran mixture

The understanding of fouling behaviors and mechanism is critical for membrane fouling that is a bottleneck for the sustainable application of membrane technology. Therefore, it is essential to develop new analytical tools that can in situ characterize membrane fouling processes during filtration. In this work, we demonstrate a capability of high-resolution large-scale in situ visualization that can rapidly differentiate foulants and their temporal-spatial-distributions on/in/over the membrane matrix during filtration process based on multi-color light sheet fluorescence imaging platform. The rapid-evolving fouling process of different foulants were directly monitored and analyzed during the ultrafiltration of bovine serum albumin (BSA), dextran and their mixture solutions. Inner adsorption was found to play a more critical role for dextran-induced fouling on polymeric membranes compared with BSA-induced fouling. During the ultrafiltration of BSA/dextran mixture solutions, BSA was directly observed as the major contributor to the decrease of permeate flux, which could be employed as a complementary evidence for the interfacial free energy calculations during membrane fouling and vice versa. This work provides new insights into combined membrane fouling process and offers a highly-sensitive, non-invasive characterization tool for a wide range of explorations in membrane-based processes and interfacial processes. In situ large-scale characterization of combined membrane fouling behaviors Strong relations between flux decline rate and foulant distributions in/on membrane Direct observation of key foulant in combined fouling process Facilitation of exploring interfacial processes (dynamic and thermodynamic)

Effect of water sorption on glass transition and microstructural variation of dextran & sugar mixtures

Dextran is widely used as a model polysaccharide to study the interactions between polysaccharides and small molecule sugars. This study examined water sorption isotherms and glass transition temperatures (Tg) of mixtures of dextran with trehalose, lactose and sucrose for understanding how different disaccharides affect dextran's processing adaptation and storage performance relevant to water sorption. At the same chemical composition, monolayer water (m0) was dextran & sucrose (dex&suc) > dextran & trehalose (dex&tre) > dextran & lactose (dex&lac). The higher ratios of dextran, the higher was the Guggenheim constant (C) value of the mixtures. The compatibility of dextran and disaccharides was dex&tre > dex&lac > dex&suc. Gordon–Taylor model showed dex&tre (2:1) best inhibited water plasticization. Furthermore, trehalose and lactose were more effective in preventing morphological changes of hydrous matrices in the mixtures. The crystallinities of samples at 43% relative humidity (RH) were slightly lower than that at 11% RH.

A customized long acting formulation of the kisspeptin analog C6 triggers ovulation in anestrus ewe.

The modulation of the kisspeptin system holds promise as a treatment for human reproductive disorders and for managing livestock breeding. The design of analogs has overcome some unfavorable properties of the endogenous ligands. However, for applications requiring a prolongation of drug activity, such as ovulation induction in the ewe during the non-breeding season, additional improvement is required. To this aim, we designed and tested three formulations containing the kisspeptin analog C6. Two were based on polymeric nanoparticles (NP1 and NP2) and the third was based on hydrogels composed of a mixture of cyclodextrin polymers and dextran grafted with alkyl side chains (MD/pCD). Only the MD/pCD formulation prolonged C6 activity, as shown by monitoring luteinizing hormone (LH) plasma concentration (elevation duration 23.4 ± 6.1, 13.7 ± 4.7 and 12.0 ± 2.4h for MD/pCD, NP1 and NP2, respectively). When compared with the free C6 (15 nmol/ewe), the formulated (MD/pCD) doses of 10, 15 and 30 nmol/ewe, but not the 90 nmol/ewe dose, provided a more gradual release of C6 as shown by an attenuated LH release during the first 6h post-treatment. When tested during the non-breeding season without progestogen priming, only, the formulated 30 nmol/ewe dose triggered ovulation (50% of ewes). Hence, we showed that a formulation with an adapted action time would improve the efficacy of C6 with respect to inducing ovulation during the non-breeding season. This result suggests that formulations containing a kisspeptin analog might find applications in the management of livestock reproduction but also point to the possibility of their use for the treatment of some human reproductive pathologies.

Defining Endocytic Pathways of Fucoidan-Coated PIBCA Nanoparticles from the Design of their Surface Architecture.

PurposeThis work investigated the endocytic pathways taken by poly(isobutylcyanoacrylate) (PIBCA) nanoparticles differing in their surface composition and architecture, assuming that this might determine their efficiency of intracellular drug delivery.MethodsNanoparticles (A0, A25, A100, R0, R25 ) were prepared by anionic or redox radical emulsion polymerization using mixtures of dextran and fucoidan (0, 25, 100 % in fucoidan). Cell uptake was evaluated by incubating J774A.1 macrophages with nanoparticles. Endocytic pathways were studied by incubating cells with endocytic pathway inhibitors (chlorpromazine, genistein, cytochalasin D, methyl-ß-cyclodextrin and nocodazole) and nanoparticle uptake was evaluated by flow cytometry and confocal microscopy.ResultsThe fucoidan-coated PIBCA nanoparticles A25 were internalized 3-fold more efficiently than R25 due to the different architecture of the fucoidan chains presented on the surface. Different fucoidan density and architecture led to different internalization pathway preferred by the cells. Large A100 nanoparticles with surface was covered with fucoidan chains in a loop and train configuration were internalized the most efficiently, 47-fold compared with A0, and 3-fold compared with R0 and R25 through non-endocytic energy-independent pathways and reached the cell cytoplasm.ConclusionInternalization pathways of PIBCA nanoparticles by J774A.1 macrophages could be determined by nanoparticle fucoidan surface composition and architecture. In turn, this influenced the extent of internalization and localization of accumulated nanoparticles within cells. The results are of interest for rationalizing the design of nanoparticles for potential cytoplamic drug delivery by controlling the nature of the nanoparticle surface.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11095-022-03202-4.

The pH-responsive phase separation of type-A gelatin and dextran characterized with static multiple light scattering (S-MLS)

Macromolecular phase separation has attracted increasing attention due to its wide applications in food industry, such as modulating food texture and delivering bioactive compounds. The phase separation kinetics is important but rarely reported due to the limitation of current methods. This work provided an effective method, static multiple light scattering (S-MLS), for the study of phase separation kinetics, and investigated the effects of pH on the phase separation of type-A gelatin and dextran mixtures (GE/DE) using S-MLS technique, fluorescence microscopy and visual assessment. Phase diagrams of GE/DE (1.0–6.0 wt%) at pH 3.00–11.0 were measured based on the micro-phase separation. Interestingly, GE/DE mixtures were likely to be miscible at low and high pHs. GE/DE (4.0 wt%/4.0 wt%) mixture at pH 3.00–10.0 was selected for following study. Phase separation of GE/DE (4.0 wt%/4.0 wt%) mixture was pH-responsive, e.g. no phase separation at pH 3.00–4.75 and pH 10.0, only microphase separation at pH 5.00 and 5.25, and both micro- and macro-phase separation at pH 5.50–9.00. The order of phase separation rates was pH5.50 > pH6.00 > pH9.00 > pH7.00 > pH8.00. Based on the results of S-MLS, micro- and macro-phase separation images, phase separation process was proposed to be divided into four steps, including droplet coalescence, droplet migration, primary and stable phase separation. The variation of the GE/DE interaction and the self-aggregation of GE as a function of the pH might explain the pH-response of GE/DE phase separation. S-MLS is an effective method to study the phase separation kinetics of macromolecular systems.

Multifunctional carbonized nanogels to treat lethal acute hepatopancreatic necrosis disease

BackgroundShrimp aquaculture has suffered huge economic losses over the past decade due to the outbreak of acute hepatopancreatic necrosis disease (AHPND), which is mainly caused by the bacteria Vibrio parahaemolyticus (V. parahaemolyticus) with the virulence pVA1 plasmid, which encodes a secretory photorhabdus insect-related (Pir) toxin composed of PirA and PirB proteins. The Pir toxin mainly attacks the hepatopancreas, a major metabolic organ in shrimp, thereby causing necrosis and loss of function. The pandemic of antibiotic-resistant strains makes the impact worse.MethodsMild pyrolysis of a mixture of polysaccharide dextran 70 and the crosslinker 1,8-diaminooctane at 180 ℃ for 3 h to form carbonized nanogels (DAO/DEX-CNGs) through controlled cross-linking and carbonization. The multifunctional therapeutic CNGs inherit nanogel-like structures and functional groups from their precursor molecules.ResultsDAO/DEX-CNGs manifest broad-spectrum antibacterial activity against Vibrio parahaemolyticus responsible for AHPND and even multiple drug-resistant strains. The polymer-like structures and functional groups on graphitic-carbon within the CNGs exhibit multiple treatment effects, including disruption of bacterial membranes, elevating bacterial oxidative stress, and neutralization of PirAB toxins. The inhibition of Vibrio in the midgut of infected shrimp, protection of hepatopancreas tissue from Pir toxin, and suppressing overstimulation of the immune system in severe V. parahaemolyticus infection, revealing that CNGs can effectively guard shrimp from Vibrio invasion. Moreover, shrimps fed with DAO/DEX-CNGs were carefully examined, such as the expression of the immune-related genes, hepatopancreas biopsy, and intestinal microbiota. Few adverse effects on shrimps were observed.ConclusionOur work proposes brand-new applications of multifunctional carbon-based nanomaterials as efficient anti-Vibrio agents in the aquatic industry that hold great potential as feed additives to reduce antibiotic overuse in aquaculture.Graphical

Scalable, Membrane‐Based Microfluidic Passive Cross‐Flow Platform for Monodispersed, Water‐in‐Water Microdroplet Production

AbstractThe generation of water‐in‐water droplets has recently received great attention for its applicability in biological applications over traditional oil‐water droplet systems because of their high biocompatibility. An aqueous two‐phase system (ATPS), aqueous mixture of polyethylene glycol (PEG) and dextran (DEX), has an ultra‐low interfacial tension which makes monodispersed droplet formation challenging. Recent passive methods in microfluidics with flow‐focusing configurations overcome this challenge, but they suffer either from polydispersity, narrow droplet size range, or low throughput. Successful droplet formation in such passive methods occurs in jetting flow regimes with low continuous phase flowrates, Qc < 1 μL min‐1. Gravity‐driven hydrostatic or highly precise pressure flow control has been used to apply constant, low flowrates that conventional syringe pumps struggle to emulate. Here, a new passive cross‐flow configuration is introduced to generate monodispersed ATPS droplets. The microfluidic device developed by the authors is membrane‐integrated with constant flowrate syringe pumps. Additionally, the membrane with three uniform pores enables this device to operate as a parallel system capable of three controlled droplet formations simultaneously, with a wide range of monodispersed droplet diameters from ≈17 to 90 μm (coefficient of variation, CV ≤ 5%) and from ≈90 to 180 μm (CV ≤ 10%).

Water-in-Water Emulsions, Ultralow Interfacial Tension, and Biolubrication

Water-in-Water Emulsions, Ultralow Interfacial Tension, and Biolubrication

Synergistic effects of pH, temperature and glycosylation on the functional properties of rice protein

AbstractThis study investigated the effects of pH treatment, heat treatment, pH‐synergistic heat treatment and glycosylation on the functional properties of rice protein (RP). The results showed that all treatment methods could improve the functional properties of RP. Heat treatment improved functional properties by generating aggregates after RP unfolds, and pH treatment improved those by causing RP to hydrolyse and aggregate. Compared to RP, the solubility, emulsification activity (EA), emulsification stability (ES), foaming activity (FA), surface hydrophobicity and in vitro digestibility of pH‐synergistic heat treatment of RP (S‐RP) were increased by 11.47, 3.12, 3.45, 2.27, 3.36 and 2.12 times, respectively. Glycosylation mainly improved the functional properties of RP by introducing hydrophilic groups. Compared to those of S‐RP, solubility, EA, ES, FA, surface hydrophobicity and in vitro digestibility of RP–dextran conjugates (RPDCs) were increased by 2.03, 1.25, 1.97, 1.05, 1.64 and 1.48 times, respectively. Therefore, compared to glycosylated chemical modification, heat treatment and pH treatment had a weak improvement in the functional properties of RP. The comparison of pH‐treated RP (pH‐RP) and RP–dextran mixtures (RPDMs) showed that in the absence of heat treatment, carbonyl ammonia condensation almost did not occur.

Whey protein isolate-dextran conjugates: Decisive role of glycation time dependent conjugation degree in size control and stability improvement of colloidal nanoparticles

Whey protein isolate-dextran (WPI-dextran) conjugates were acquired via Maillard reaction for different durations (1–7 days) and their potential to govern the size and stability of colloidal nanoparticles formed from heating electrostatic complexes of WPI-dextran conjugates and chondroitin sulfates was assessed. The grafting degree and browning index gradually increased with the reaction time. The intensity of amide bands increased in the first 2 days and then declined. As the duration increased, the content of α-helix increased from 23.9% to 29.6%, while β-sheet and random coil decreased from 23.8% and 38.1% to 19.6% and 32.7%, respectively. Moreover, the surface hydrophobicity was reduced as the conjugation progressed, while surface and total sulfhydryl content gradually increased from 5.3 and 15.4 μmol/g to 11.0 and 17.9 μmol/g, respectively. Meanwhile, fluorescence intensity of conjugates decreased with prolonged durations. These changes with increasing grafting degree prompted greater steric hindrance, weakened hydrophobic interaction, and improved stability of protein during heating, thus facilitating the decreasing diameter of the corresponding heat-induced nanoparticles. In comparison with the nanoparticles derived from non-conjugated mixture of WPI and dextran, those from WPI-dextran conjugates showed an excellent stability to aggregation and dissociation upon synergistic influence of pH variation (1–10) and enhancing ionic strength (0–4 mol/L).

Macromolecular crowding effects on the kinetics of opposing reactions catalyzed by alcohol dehydrogenase

In order to better understand how the complex, densely packed, heterogeneous milieu of a cell influences enzyme kinetics, we exposed opposing reactions catalyzed by yeast alcohol dehydrogenase (YADH) to both synthetic and protein crowders ranging from 10 to 550 kDa. The results reveal that the effects from macromolecular crowding depend on the direction of the reaction. The presence of the synthetic polymers, Ficoll and dextran, decrease Vmax and Km for ethanol oxidation. In contrast, these crowders have little effect or even increase these kinetic parameters for acetaldehyde reduction. This increase in Vmax is likely due to excluded volume effects, which are partially counteracted by viscosity hindering release of the NAD+ product. Macromolecular crowding is further complicated by the presence of a depletion layer in solutions of dextran larger than YADH, which diminishes the hindrance from viscosity. The disparate effects from 25 g/L dextran or glucose compared to 25 g/L Ficoll or sucrose reveals that soft interactions must also be considered. Data from binary mixtures of glucose, dextran, and Ficoll support this “tuning” of opposing factors. While macromolecular crowding was originally proposed to influence proteins mainly through excluded volume effects, this work compliments the growing body of evidence revealing that other factors, such as preferential hydration, chemical interactions, and the presence of a depletion layer also contribute to the overall effect of crowding.

Impact of dextran on thermal properties, product quality attributes, and monoclonal antibody stability in freeze-dried formulations

Freeze-drying is commonly used to improve stability of liquid formulations of labile biopharmaceuticals. Lyo- and cryoprotectants such as sucrose are traditionally utilized as excipients, but have low glass transition (Tg′) and collapse temperatures (Tc). Consequently, these formulations require low primary drying temperatures making the lyophilization cycle time-consuming and costly. We investigated different dextrans (1, 40, 150, and 500 kDa) and mixtures of dextran with sucrose as alternative excipients. The influence of dextran on thermal properties, cake appearance, and other quality attributes in the solid state was studied using bovine serum albumin as model protein. Especially at higher weight ratios of dextran to sucrose, dextrans of medium to high molecular weight (MW) of 40–500 kDa showed up to 20 °C higher Tc compared to sucrose, which was reflected in elegant lyophilisates. However, this resulted in slower reconstitution times. Addition of dextran led to lower residual moisture levels and higher Tg values compared to sucrose. We confirmed the thermal properties for two monoclonal antibodies (mAb) at two weight ratios of sucrose and dextran with different MW, and tested for stability at 40 °C for 14 days. While no loss in relative potency of the antibodies was observed after storage, size exclusion chromatography and isoelectric focusing revealed a strong increase in high molecular weight species (HMWs) and acidic species, which were dependent on the MW of the dextrans. With further characterization of selected formulations (dextran 1 kDa) by boronate affinity chromatography and mass spectrometry analysis, we demonstrated that HMWs were a result of glycation by free terminal glucose of the dextran. This chemical modification was strongly reduced when adding sucrose, which protects the protein possibly by shielding its surface. Our results demonstrate that formulation scientists need to use dextrans as excipients in freeze-dried mAb formulations with caution. A binary mixture of sucrose and dextran in adequate ratio however might potentially be superior to pure sucrose formulations allowing for faster freeze-drying cycles resulting in elegant lyophilisates and good protein stability.

Second order virial coefficients from phase diagrams

The prediction of phase separation is essential to understand and control the properties of food systems. In this work, an existing theoretical model for describing phase separation between binary mixtures of hydrocolloids, using a virial approach up to second order, is extended with several new analytical expressions. These new expressions allow one to determine the three virial coefficients directly from three characteristics of the phase diagram, where the critical point plays a pivotal role and allows one to predict the complete phase diagram. The advantage of this approach is that experimental techniques, like membrane osmometry or static light scattering, to directly measure virial coefficients can be, in principle, avoided. It was found that just the location of the critical point is sufficient to determine two of the three virial coefficients, when one of the virial coefficients is known. When, in addition to the critical point, one other characteristic of the phase diagram is known with sufficient accuracy, like the slope of the tie-lines near or far away from the critical point, all three virial coefficients can be determined from the phase diagram. Using this approach, three virial coefficients for aqueous mixtures of dextran and polyethylene oxide were determined and compared to the ones obtained from membrane osmometry.

Facile Preparation of Highly Luminescent Materials by Electrostatic Immobilization of Anionic Metal Complex onto Anion-Exchanger as Exemplified with Tri-Terbium(III) Cluster Complex of Thiacalix[4]arene-p-tetrasulfonate

Abstract We propose a strategy to prepare luminescence materials via simple and organic solvent-free fashion by mixing an anionic luminescent complex with an anion exchanging support. As a proof-of-concept, we employed the heptaanionic TbIII complex Tb3TCAS2 (TCAS = thiacalix[4]arene-p-tetrasulfonate) and QAE Sephadex A-25, a dextran support bearing anion exchanging groups. By stirring a mixture of TCAS and dextran (1.0 µmol Tb3TCAS2/50 mg dextran), 99.8% of Tb3TCAS2 was successfully immobilized within 2 h. The electrostatic interactions were strong enough to irreversibly bind Tb3TCAS2 to the dextran. The material exhibited TbIII-centered luminescence upon excitation of the TCAS center. The luminescent lifetime and quantum yield were 1.18 ms and 45.5%, respectively. When the amount of Tb3TCAS2 immobilized on the dextran was reduced to 1.0 nmol/50 mg dextran, the lifetime increased to 1.32 ms, suggesting concentration quenching above 1.0 µmol Tb3TCAS2/50 mg dextran. On the other hand, the luminescence quantum yield decreased to 3.1%, suggesting that the absorption of excited light by the support was not negligible. Preparation of the materials in D2O resulted in increases in the lifetime and quantum yields to 1.32 ms and 44%, respectively.

Crosslinking dextran electrospun nanofibers via borate chemistry: Proof of concept for wound patches

Dextran-based formulations represent promising candidates for the fabrication of biocompatible scaffolds in tissue engineering or as vehicles for drug delivery. Previous investigations showed that, on its own, dextran is able to promote wound healing in vivo in rat models. Its inherent solubility in water, however, must be overcome by inserting inter-molecular junctions via the use of cross-linkers. While conventional cross-linking methods tend to utilize toxic compounds, such as glutaraldehyde, we demonstrate that simple mixtures of dextran and boric acid, in aqueous solutions, can be electrospun to obtain membranes with controlled degradation times. Boric acid covalently links to the hydroxyls moieties present in the dextran chains yielding boronate ester bridges between dextran chains. Variation in the cross-linking density enhanced the average drug release time up to 500% compared to pristine dextran electrospun scaffolds.

Mutual interaction of red blood cells assessed by optical tweezers and scanning electron microscopy imaging.

The adhesion of red blood cells (RBC) has been studied extensively in frame of cell-to-cell interaction induced by dextran macromolecules, whereas the data are lacking for native plasma solution. We apply optical tweezers to investigate the induced adhesion of RBC in plasma and in dextran solution. Two hypotheses, cross-bridges and depletion layer, are typically used to describe the mechanism of cell interaction; however, both mechanisms need to be confirmed experimentally. These interactions in fact are very much dependent on the size and concentration of dextran and proteins in plasma. The results show that in different dextran solutions, the interaction of adhering RBC agrees well with the quantitative predictions obtained based on the depletion-induced cells adhesion model, whereas the migrating cross-bridges model is more appropriate for plasma. Despite the different mechanisms of RBC interaction in a mixture of dextran with the size ranges and volume fraction proportional to plasma proteins, the dependence of RBC adhering tends to be close to the cross-bridges model. The induced aggregation of RBC in the dextran solutions and in native plasma are observed by direct visualization utilizing scanning electron microscopy.