Webprotein hydrodynamic radius was observed with increasing protein concentration (in the range 0.25-2 mM) in both the absence and presence of 8 M urea. PubMedGoogle Scholar. Ubbelohde, Leo. A novel high dextran yielding Weissella cibaria JAG8 for cereal food application. Journal Argentine Chemical Society 100 (2013) 25-34. The solution was measured using an Anton Paar DMA35N densitometer. WebHydrodynamic radius = variable size of an analyte with specific MW based on dynamical properties. Not for use in diagnostic procedures. Bohdanecky, Miloslav (1996). Comparison of single-point and dilution procedures. For a given polymer-solvent pair, the theta condition is satisfied at a certain temperature, called the theta () temperature or theta point. Chem. Armstrong, J. K.; Wenby, R. B.; Meiselman, H. J.; Fisher, T. C. (2004). The particular dextrans which were used initially for conversion into synthetic blood-volume expanders [6, 7], human red blood cells aggregation for increasing the degree of polymerization and hence the molecular weight [8, 9, 10], hydrogels and microspheres [11], in drug transport system and its modifications as nanoparticles [12], in the removal through absorption of contaminant effluents such as heavy metals, organic molecules and inks [13], in the formation of biodegradable films [14, 15]. The formula is verified for different systems of polymer-solvent and the values are in accord with those obtained by extrapolation. The great deviation at 2000kDa occurs due to the large hyperbranched structure of the macromolecule, generating a change in its conformation and, therefore, a change in the way it flows [73]. All possible degrees of curling can be displayed by any molecule, but there will be an average configuration which will depend on the solvent. Colloid and Polymer Science, 286, 1223-1231. Im Tiefkhlgert (-5 bis -30C) lagern und vor Licht schtzen. Advanced Drug Delivery Reviews, 60, 1650-1662. Actually, everything depends on solvent you want to use and temperature. If you want to know gyration (Rg)or hydrodynamic (Rh) radius, you should sharing sensitive information, make sure youre on a federal Using the polymer standards, a plot of the ln [] vs ln Mw usually gives a straight line. Drug Deliv. Monosaccharide analysis revealed that the polysaccharide comprised only glucose units. In summary, we demonstrated effective enhancement of skin permeability and delivery of macromolecules lower than 20KM.W., and regeneration of human cadaver skin after microporation with an RF-based microporation device. Pavlov, G.M. One day before the experiment, the skin was stabilized in the skin culture medium. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. TEWL measurements were taken 30min after microporation of the human and pig skin. 2000;3(9):31826. Nat Biotechnol. In a good solvent, which shows a zero or negative heat of mixing with the polymer, the molecule is less-extended, and the intrinsic viscosity is high. Ind. Charge: Anionic. The lack of data on the uniformity of intrinsic viscosity measurements in the system water/dextran, highlights the significant influence of the solvent and temperature [74]. MeSH Macromolecules, 33, 5730-5739. In this sense, the largest deviations were obtained for the highest molecular weight (580-2000kDa with values from 0.8467 to 0.7346). Ioan, C.E. To improve drug permeability, micropore ablation using RF is performed by passing an alternating electrical current through the skin at a frequency higher than 100kHz. Prausnitz MR, Langer R. Transdermal drug delivery. Increased TEWL values are evidence of micropores formation. 24h after microporation, the pore sizes reduced from 64.8817.20m (0h) to 48.854.27m (24h), and the pore depths reduced from 83.9120.56m (0h) to 63.9527.61m (24h). In the case of a poor solvent, a temperature increase causes an increase in entropy and intrinsic viscosity and is favorable for the extended conformation. The equation 4 can be rearranged and resulted in a modified M-H equation as follows: where the value qM-H is the polydispersity correction factor, and it is a statistical function of the molecular weight distribution. Typical examples are the classical size-independent combinations like the Flory parameter, which that combine the intrinsic viscosity, [], and the gyration radius, Rg: These quantities have been proposed along the years, by different eminent scientists, after whom they are named. Polymolecularity and polydispersity in Molecular weight determinations. Here we have the hydrodynamic radius estimate for the 3kDa dextran and 1.5 kDa dextran by the Zetasizer calculator, thanks to Alan. Alan F Rawle, t Challenges in analysis of high-molar mass dextrans: Comparison of HPSEC, AsFlFFF and DOSY NMR spectroscopy. Exp Cell Res. Pig skins (Micropig Franz cell membrane) were supplied by Medi Kinetics Co., Ltd. (Pyeongtaek, Korea). The most widely applied coatings for FDA-approved SPIONs are dextran and carboxydextran. (2007). (2003). A lot of research has been devoted to dextrans modification in order to describe special characteristics relevant to specific applications such as surfactants [16], as visible marker [17], polysaccharides-based nanoparticles, covalent crosslinking [18], ionic crosslinking, polyelectrolyte complex, and the self-assembly of hydrophobically modified polysaccharides, and hydrophilic modified polysaccharides [19]. 8600 Rockville Pike In vitro studies with human cadaver skin is a viable, ethical, and economical alternative for in vivo animal studies. ACS Nano. Barshtein, G.; Tamir, I.; Yedgar, S. (1998). Unperturbed dimensions and theta temperature of dextran in aqueous solutions. Hydrodynamic radii were measured using Dynamic Light Scattering (DLS) in a Malvern Zetasizer NanoZS DLS (Malvern Instruments, Malvern, UK) at high scattering angle (173) to minimise the effects of dust and supramolecular contamination (NIBS, 173). The permeability of fluorescein isothiocyanate-dextrans (FITC-dextrans) with different molecular weights through the pig and human cadaver skins were measured using Franz diffusion cell. Vemulapalli V, Bai Y, Kalluri H, Herwadkar A, Kim H, Davis SP, Friden PM, Banga AK. Biomaterials. The hydrodynamic radius of 2-NBDG glucose was too small to measure. Huang S, Huang G. Preparation and drug delivery of dextran-drug complex. Chem. eCollection 2015. Human cadaver skins (fresh human full-thickness skin disc, 12~20mm) were supplied by Biopredic International (Saint-Grgoire, France). Determination of constants, kM-H and a, from the intrinsic viscosity data, requires a series of monodisperse polymer samples with known molecular weight or a series of polydisperse polymer samples with known viscosity average molecular weights, Mv. Journal of American Chemical Society, 76 (20), 5041-5052. In this work, we evaluate the maximum radius of macromolecules able to enter into HeLa cells following a plasma treatment using a size exclusion approach with dextran molecules. 2012;101(8):28619. ; Patel, T.R. 4K, b M.W. The a value is higher than calculated in this work, because these calculations were performed with number average molecular weight (Mn) which rearranges the value of a and forces him to enter into unbranched or linear molecules (a > 0.5), on the other hand, if molecular weights (Mw) ware used to value would be less than 0.5. Physicochemical studies of oligodextran. Dextran is soluble in water, methyl sulphoxide, formamide, ethylene glycol, glycerol, 4-methylmorpholine-4-oxide, and hexamethyl phosphamide [4]. The numerical value of a indicates that dextrans acquire the shape of a rigid sphere in aqueous solution; and kM-H demonstrates that under water the value decreases with temperature [71, 72]. For a values from 0-0.5 a rigid sphere is predicted in a ideal solvent, from 0.5-0.8 a random coil in good solvent, and from 0.8-2 a rigid or rod like shape is expected (stiff chain). Format), Citation-(EndNote Transdermal drug delivery: overcoming the skins barrier function. The exponent a is a function of polymer geometry, and varies from 0.5 to 2 and exponent is dimensionless. 4h after microporation, the sizes of the micropore decreased slightly. GYA primarily conducted research. The M-H equation is empirical and valid for monodisperse polymers, and it is applied to biomacromolecules (complex, hyperbranched, crosslink), taking the precaution of comparing the value of Mv with the polydispersity index (qM-H). 2012;9(2):14754. After the pore closure examination, each sample was stored in a 10% neutral buffered formalin awaiting haematoxylin/eosin (H&E) staining. Molecular weight, molecular weight distribution and molecular size of a native dextran. Chapter 2.1.4 Suspended level viscometers for transparent liquid, Ubbelohde Viscometer page 28-31. Working with the molecular weights given by the manufacturer and compare them with the molecular weights, calculated from the Mark-Houwink parameters in this work; can be seen that the %RE obtained, see Table 6. All authors have consented to the submission of this manuscript for publication. European Biophysical Journal, 36, 85-94. WebThomas Gutberlet works at Jlich Centre for Neutron Science (JCNS-2), Forsch and is well known for Lipoteichoic Acid, Neutron Reflectometry and Neutron Reflectivity. (2013). Schematic illustration of transdermal delivery after the application of the microporation device. Harding, Stephen E. (2005). Int J Pharm Investig. The genus Weissella: taxonomy, ecology and biotechnological potential. (1999). WebDextran 40 Pharmaceutical Quality. Keywords: Die Makromolekulare Chemie, 148(1), 229-238. The site is secure. Journal of Polymer Science, 17, 527-546. ; Fran, H.P. (more or less, with a hydrodynamic radius of less than 100 nm) to cross from the vasculature into the interstitium. The dextran used is from Leuconostoc mesenteroides B-512F which is essentially a linear -(1-6)-linked glucose chain with however a low percentage (2-5%) of -(1-3) branches distributed along the chain4. Nair SS. High Manufacturing Standards of Molecular Probes Dextrans. 2009;301(8):60913. WebThe micelles produced at pH 4.6 have a spherical shape and their size is dependent on the Maillard reaction: reaction time, molar ratio of casein to dextran, and molecular weight of dextran used. Google Scholar. 20K. * shows a significant difference between the M.W. The lower molecular weight of FITC-dextran permeated more on both human and pig skin. ; Garca de , J. Dextran Triple Detector Application Note 1, Viscotek GmbH, USA. For data requests, please contact the authors. It is well tolerated on parenteral infusion by most people but a very low incidence Walkenhorst, S.; Olivier, R. (2002). Microneedles and their applications. The Intrinsic Viscosity of Biological Macromolecules. Hi Sir Alexander Malm , Thank you very much! Really appreciate your help! Format). Effect of temperature on the intrinsic viscosity and conformation of chitosan in dilute HCl solution. The solution viscosity () is related to the solvent viscosity (o), resulting in the relative viscosity. Microporations were performed 2, 5, and 10 times and the skin damage was confirmed using the TEWL measurement. (1990). The Dextrans intrinsic viscosity is determined as a function of the molecular weight in water and NaOH 0.5 M see reference [1]. WebDiffusivity of 2000 kDa Dextran was significantly lower for both hydrogel formulations, but was insensitive to collagen concentration, likely due to a larger hydrodynamic diameter (d h ~ 70 nm) on order of the collagen mesh size. government site. We will also conduct further studies on the regeneration of human cadaver skin and evaluate the possibilities of clinical trials. For simplicity, macromolecules are treated as rigid molecules for a hydrodynamic study. eCollection 2018 Feb. Molecules. 2015 Mar 17;6:155. doi: 10.3389/fmicb.2015.00155. 2005;22(4):5505. ; van Nostrum, C.F. Pore closure examination was performed using an optical microscope (BX43, Olympus, Japan) immediately (time 0), 4, 8, and 24h following device application. Alternatives to animal testing: a review. These vibrations heat the skin tissue, triggering water vapor and cell ablation, forming microchannels from the SC through to the outer dermis. Intrinsic viscosity determination offers a simple and useful method that requires low cost equipment and yields useful information on soluble macromolecules. The Mark-Houwink. Salunkhe SS, Bhatia NM, Pokharkar VB, Thorat JD, Bhatia MS. Topical delivery of idebenone using nanostructured lipid carriers: evaluations of sun-protection and anti-oxidant effects. WebThe micelles produced at pH 4.6 have a spherical shape and their size is dependent on the Maillard reaction: reaction time, molar ratio of casein to dextran, and molecular weight of dextran used. Article Hydrodynamic radii ( RH) were determined by dynamic light scattering. 2023 Feb 17;12(4):861. doi: 10.3390/foods12040861. WebR H Hydrodynamic radius [m] The basic DLS setup. The values of 0 decreases from 2.5429 to 2.3326 x 1023mol-1 demonstrating a relative flexibility of particles. Table 2 shows that comparing the intrinsic viscosity data obtained from the Huggins method and the Solomon-Ciuta single-point method, a similar values are obtained and the %RE is lower for low Mw and it increases for higher Mw. Disclaimer. Global hydrodynamic analysis of the molecular flexibility of galactomannans. DLS tests were conducted at detection angle of 90 (standard) and 173 (backscatter) to measure protein hydrodynamic radius, while protein charge was examined in phase analysis light scattering (PALS) mode at detection angle of 15 (forward). The intrinsic viscosity can be easily calculated by the Solomon-Ciuta single-point equation [44, 45]. (2003). In general, Mv is not experimentally accessible, whereas other average molecular weights are accessible. The qM-H values given by equation 13, these vary from 0.9993 to 0.9841 for the range between 8.8 to 200kDa in a temperature range of 20 to 40C. WebTo address this perception, in the current study, FITC-dextran of different MWs (10, 70 and 150 kDa) was used to model the transdermal delivery of low MW biotherapeutics and mAbs with MWs of approximately 150 kDa. The most widely used method for the characterization of macromolecules is the capillary viscometry, as it is a simple and economic method. Advances in chemistry series Washington, DC: American Chemical Society., pp. Saudi Pharm J. The Hydrodynamic Radii of Macromolecules and Their Effect on Red Blood Cell Aggregation. Kano S, Todo H, Furui K, Kenichi S, Tokudome Y, Hashimoto F, Kojima H, Sugibayashi K. Comparison of several reconstructed cultured human skin models by microscopic observation: their usefulness as an alternative membrane for skin in drug permeation experiments. ; Veldhuis, T.F.J. Thermo Fisher Scientific. The first term on the left-hand side of equation 2 (i/c) has a linear relation as a function of the concentration (c in g/cm3), where is the intrinsic viscosity [] is given by (c0) [42, 43]. Rotureau, E.; Dellacherie, E.; Durand, A. Liu Zonghua; Yanpeng Jiao; Yifei Wang; Changren Zhou; Ziyong Zhang (2008). FITC-derivatives have been used for a variety of biological applications for more than 40 yeras. Solution properties of branched dextran. The term f/f0 is sometimes denoted as P, Perrin constant. Dextran Fractions. Rissmann R, Oudshoorn MHM, Hennink WE, Ponec M, Bouwstra JA. 4K was 10.611.68 and 13.440.18M in human and pig skin, respectively. Molecular weight determination of polysaccharides. This method utilizes promising strategies that have made a significant impact in transdermal delivery [6], they include: iontophoresis, microneedles, sonophoresis, radiofrequency (RF), and chemical enhancers [7,8,9,10,11]. In the future, we plan to investigate the possibility of enhancing the delivery of other macromolecular drugs such as peptides and siRNAs using the RF-based microporation device. Masuelli, M. A. For rigid macromolecules, it is also conventional to combine a solution property with the volume of the particle itself, or with a quantity directly derived from it [54, 55, 56]. Typically, the hydrodynamic diameter of the micelles is about 100 nm and the critical micelle concentration is about 10 mg/L. The results are shown to be in good agreement with available hydrodynamic models for spherical solutes in cylindrical pores with the effective solute to pore size ratio evaluated using a partitioning model which implicitly AATEX. Journal of Pharmaceutical and Biomedical Analysis, 41, 1260-1267. Determination of intrinsic viscosities of macromolecules and nanoparticles. Transdermal delivery of FITC-Dextrans with different molecular weights using radiofrequency microporation. Degrees of long-chain branching in dextrans. Hrabchak C, Flynn L, Woodhouse KA. From Table 1, It is worth noting that the value of 2 is above 0.95, being an acceptable value for viscosimetric measurement. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. WebLabeled dextrans are hydrophilic polysaccharides most commonly used in microscopy studies to monitor cell division, track the movement of live cells, and to report the The cumulative permeation of FITC-dextran 10K was 4.820.32M, in the human skin and 5.920.46M in the pig skin. Web54 we estimated that the hydrodynamic radii of 3-5 kDa dextran, 20 kDa dextran, and 70 kDa dextran are 2 55 nm, 5 nm, and 6 nm, respectively. The hydrodynamic radius (Rh) of individual samples of dextran, polyvinylpyrrolidone, and polyoxyethylene over a range of molecular weights (1,500 Peptide and protein transdermal drug delivery. Elias, Hans-Georg (1975). (1969). The dextran has the advantage in terms of low cytotoxicity, excellent biocompatibility, and water-solubility. Analyzing the values of the hydrodynamic properties of dextran in aqueous solution, it can be seen in Table 7, that all vary with the temperature. At 20C data "a" value obtained in this work is intermediate to those given by references [1, 37] while the value of kM-H is lower. These results could be attributed to the differences in the in vivo and in vitro skin nutrients supply; with in vivo studies, the skin tissue is supplied nutrients directly from the blood vessels, but the human cadaver skin is supplied from the media, therefore, the skin tissue regeneration efficiency is low [26,27,28]. Monosaccharide analysis revealed that the polysaccharide comprised only glucose units. Careers. Drug Discov Today Technol. Gold MH, Biron JA. ; Bos, G.W. Curvale, R.; Masuelli, M.; Perez Padilla, A. FITC-dextran solution (600L) was added to the donor chamber. 20K groups (n=3, *: p<0.05, **: p<0.01). (2000). Qi P, Caoa M, Songa L, Chena C, Liua M, Li N, Wua D, Penga J, Hub G, Zhao J. The most widely applied coatings for FDA-approved SPIONs are dextran and carboxydextran. WebThis value is sensible given that i j = 0 and that the search radius of the clustering algorithm is slightly larger than the average segment length of our Dextran model (b 5.5 nm). Probiotics Antimicrob Proteins. Arch Dermatol Res. Dextrans can function efficiently as anterograde or retrograde tracers, 2009;6(4):34354. Fusco V, Quero GM, Cho GS, Kabisch J, Meske D, Neve H, Bockelmann W, Franz CM. Pharm Res. 2005;304(1):27486. The fast increasing of these polyglucosans for medical, industrial and research purposes motivated a survey of the types obtainable. ; Picout, D.R. Rheology of dextran solutions. Unable to load your collection due to an error, Unable to load your delegates due to an error. The relative browning for dextran from W. cibaria JAG8 was similar to commercial prebiotic Nutraflora P-95 and 3-fold lower than Raftilose P-95. TEWL measurements were performed before and 30min after microporation. After 24h the micropores were either closed or reduced further to smaller sizes, 37.5020.41, 50.5718.07, and 58.5814.99m, for 2, 5, and 10 times microporation, respectively. In this study, we investigated the effectiveness of RF microporation technology in vitro, by evaluating the permeation of fluorescent-conjugated dextran (FITC-dextran) of various molecular weights through the human and pig skin after microporation, using a transdermal diffusion cell system. CAS 2003;10:33847. On single point determination of intrinsic viscosity. Increased epidermal laser fluence through simultaneous ultrasonic microporation. ; Rjumtsev, E.I. Kirkland, J. J.; Dilks, C. H.; Rementer, S. W. (1992). Learn More. The Solomon-Ciuta single-point method is used for calculating dextran intrinsic viscosity and the error relative is calculated, and %RE respect to Huggins method is >4.18% for 2000kDa, and >2.06% for 8.8kDa (Table 2). CAS Synthesis of dextran by dextransucrase treated, sucrose-supplemented skimmed milk revealed the promising potential of dextran as a food additive. A simple and rapid method for evaluation of MarkHouwinkSaturada constants of linear random coil polysaccharides using molecular weight and intrinsic viscosity determined by high performance size exclusin chromatography: application to guar galactomannan. The authors declare that they have no competing interests. ; Grishchenko, A.E. After 8h, the micropore became more distorted from the previous circle, suggesting that the micropores were closing. The 70-kDa FITC dextran reached the jejunum after 15 min and passed the entire small intestine within 1 h after its administration, demonstrating that 4-kDa FITC dextran measured in plasma 1 h after its oral application is a marker of small intestinal permeability. The measurements of the transepidermal water loss (TEWL) were taken using the Tewameter (Courage-Khazaka Electronic GmbH, Cologne, Germany) to evaluate the skin barrier function after microporation. TdB Labs produce a wide range of FITC-derivatives (490 nm/520 nm) with a mean molecular weight ranging from 4 kDa to 2000 kDa. ; Weisz, J. Human cadaver skin has been confirmed as alive skin tissue through analysis of its morphology and enzymes, and its usefulness as an alternative skin membrane in drug permeation experiments has been verified [20]. WebFITC Products. The polymer molecule assumes a tighter configuration, and the solution has a lower intrinsic viscosity. Guner, Ali (1999). The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Figure 2 shows the classical method for calculating Mark-Houwink parameters, where a linear relation between the intrinsic viscosity and the molecular weight is established for each temperature. FITC-dextran molecular weights; 4, 10, and 20kDa molecular weight were purchased from Sigma (St. Louis, MO, USA). GPC Symp. 4K and M.W. Carbohydrate Research, 160, 205-214. Arond L.H. MeSH terms Transdermal drug delivery system for non-steroidal anti inflammatory drugs: a review. Karmarkar, S.; Garber, R.: Kluza, J.; Koberda, M. (2006). Journal of American Chemical Society, 64(11), 2716-2718. Although, intrinsic viscosity is a molecular parameter that can be interpreted in terms of molecular conformation, it does not offer as high resolution on molecular structure as other methods such as Light Scattering, Circular Dichroism, Sedimentation Velocity, Sedimentation Equilibrium, Size Exclusion Chromatography Coupled to Multi-Angle Laser Light Scattering (SEC-MALLS), High-performance Size Exclusion Chromatography (HPSEC), Gel Permeation Chromatography (GPC), NMR, X-rays, etc. ; Tsuchiya, H.M.; Rist, C.E. European Journal of Pharmaceutics and Biopharmaceutics, 68, 319-329. They concluded that a power law behavior seems to be approached only in the small molecular weight region. Viet, D.; Beck-Candanedo, S.; Gray D. G. (2008). WebDextran 670 GPC Standard Normative Mw - 670000 Da GPC standards can be used for calibration and molecular weight determination. Our portfolio includes for example derivatives of dextran, polysucrose, inulin and more. Webdextran hydrodynamic radius. ; Prasad, D.H.L. TEWL values before and immediately after microporation on human cadaver skin according to the number of times microproration was done (n=3). Skin barrier disruption by acetone: observations in a hairless mouse skin model. Weissella: An Emerging Bacterium with Promising Health Benefits. The same way, many of these authors emphasize the non-linear or hyperbranched of dextran molecular weight range from 9 to 2000kDa [3,5,8,16, 37,38]. National Library of Medicine Mainaa, Ndegwa Henry; Pitknen, Leena; Heikkinen, Sami; Tuomainen; Pivi; Virkki, Liisa; Tenkanen, Maija (2014). Ther. Carbohydrate Polymers 99, 199-207. There is a formula that used to calculate the radius (in Angstrom) from the molar mass (in g/mol) of dextran, a=0.33*(MM^0.46) where, a and MM are Fixable: Fixable via Lysine. Changes in the Mark-Houwink hydrodynamic volume of chitosan molecules in solutions of different organic acids, at different temperatures and ionic strengths. A single frequency laser is directed to the sample contained in a cuvette. Journal of Applied Polymer Science, 72, 871-876. 2018 Aug 9;23(8):1984. doi: 10.3390/molecules23081984. Named after George Gabriel Stokes, it is closely related to solute mobility, factoring in not only size but also solvent effects.A smaller ion with stronger hydration, for example, may have a greater Stokes radius than a larger ion with 1994, 95-0355. These constants can be determined experimentally by measuring the intrinsic viscosity of several polymer samples for which the molecular weight has been determined by an independent method (i.e. These structural differences can significantly affect FITC-dextran delivery due to even after microporation [30]. The correct way to interpret what Mark-Houwink parameters is determined graphically ln [] versus ln Mw, where Mw is the molecular weight provided by manufacturer, and calculate the percentage relative error (%RE) respect to Mw. 2.It can be found from the figure that at the start-up stage of the shaft, the hydrodynamic effect (HE) is weak, so the HP is not enough to support the shaft, which 2023 BioMed Central Ltd unless otherwise stated. Thus, typically, the dextran glomerular for a molecule with a Stokes-Einstein (SE) radius of 30 is approximately sevenfold higher than that of neutral horseradish Equivalent Radii and Ratios of Radii from Solution Properties as Indicators of Macromolecular Conformation, Shape, and Flexibility. dextran hydrodynamic radius. Ortega, A.; Garca de la Torre, J. Surface morphology study of dextran by scanning electron microscopy showed the porous web like structure.