Characterization and comparison of shear and extensional flow of sodium hyaluronate and human synovial fluid.

The focus of this work is on a comparative rheological characterization of sodium hyaluronate (NaHA) samples from fermentative production (NaHA-1, Mw = 1.7 × 106 g/mol) and from rooster comb (NaHA-2, Mw = 4.6 × 106 g/mol) with synovial fluid (SF) taken post mortem from different patients above 60 years. Steady state shear flow and uniaxial extension experiments were carried out for different concentrations of NaHA in 0.01 M phosphate-buffered saline (PBS) and on several SF samples.The synovial fluid of older patients was found to have a viscoelasticity comparable to that of younger patients investigated in earlier studies. Comparison of steady state shear experiments revealed a comparable progression for the viscosity curves of NaHA-2 and SF. This behavior was also observed in extensional flow, where comparable results for NaHA-2 and different SF samples were obtained.

Single and multi-step carboxymethylation of water yam (Dioscorea alata) starch: synthesis and characterization.

Water yam (Dioscorea alata) starch was carboxymethylated by single and multi-step processes for nine times successively. Optimal degree of substitution (DS) of 0.98 and reaction efficiency (RE) of 70.5% were obtained in the single-step carboxymethylation at 40 degrees C, 3 h in isopropanol-water reaction mixture ratio 1:0.16. The ratio of sodium hydroxide and sodium monochloroacetate moles to anhydroglucose unit moles for the optimal DS and RE were 1.62 and 1.39, respectively. The DS increased progressively as the steps of carboxymethylation increased from 2 to 9 and an optimal DS of 2.24 was obtained. Initial increases in carboxymethylation step increased the RE progressively up to 82.1% after the seventh carboxymethylation step but declined with further increases in the carboxymethylation step. The wide angle X-ray diffractometry and the DSC revealed remarkable changes after carboxymethylation because starch crystallinity reduced significantly. Thermogram of native starch showed a characteristic three-step decomposition with 13.16%, 61.54% and 24.79% weight losses progressively while carboxymethyl derivative showed four decomposition stages with 9.86%, 36.57%, 3.04% and 23.07% weight losses progressively. Studies revealed that carboxymethylation improved thermal stability of the native starch. IR spectrometry revealed that carboxymethyl starch showed new bands at nu=1600, 1426 and 1324 cm(-1). The broad band (13)C NMR spectra of the ultrasonically degraded carboxymethyl starch showed a peak at delta=180 ppm which was assigned to carbonyl carbon.

Cationic starches as substitute for synthetic cationic flocculants in solid-liquid separation of harbor sludge.

Harbor sludge (about 25% total solid) has to be dredged to keep the waterways free. Thus, annually 1.2 million m3 of dredged material has to be cleaned. For this process, three different synthetic flocculants with optimal molar masses, ionogenities, and concentrations are added in order to get a good dewatering efficiency and shear strength of the flocs. But as synthetic flocculants bring about unwanted fish toxicity and insufficient biodegradability, this study intends to check whether these flocculants can successively be substituted by cationic starches which have already been proven to be less toxic than synthetic flocculants. Five different starch derivatives with an average degree of substitution higher than 0.5 were characterized, especially in terms of the molar mass and coil size distribution, and flocculation tests, zeta potential measurements and filtrate turbidity tests were carried out in order to create optimum flocculation conditions. The flocculation and dewatering measurements clearly show that the synthetic cationic flocculant PA (0.2 kg/tTS) can be best substituted by cationic starch KS 2 (c = 0.1 kg/tTS, Mw = 1.1 e+08). For substitution of PTAC (c = 0.3 kg/tTS) by cationic starches, we observed that a maximal dewatering efficiency is reached with an approximately 3-fold dose of KS 1 (1 kg/tTS, Mw = 8.1 e+07).

Formation and characterization of chitosan membranes.

In this paper, hydrophilic polymer membranes based on macromolecular chitosan networks have been synthesized and characterized. The structure of the membrane has been altered in several ways during the formation to adjust the properties, particularly with regard to the elasticity, tensile strength, permeability, and surface structure. An alteration of the network structure was achieved by addition of flexibilizer, cross-linking with dialdehydes, symplex formation of the chitosan with the polyanion sulfoethyl cellulose, and the introduction of artificial pores on the micro- and nanometer scale into the chitosan matrix with silica particles or poly(ethylene glycol). The resulting network structures and morphologies of these unique membranes that combine the novel alteration techniques have been characterized in detail and correlated with molecular parameters of the chitosan as degree of deacetylation, molar mass, and charge density. Finally, we report on the impact of the new network structures on physical properties of the membranes, the water vapor and gas permeability and the tensile strength, to evaluate possible application of the membranes as a wet wound dressing material with microbial barrier function that actively assists the healing process of problematic wounds. Parts of the novel combined membrane alteration and formation techniques are now covered by the patent DE 102004047115.

Correlation between immunological activity, molar mass, and molecular structure of different (1-->3)-beta-D-glucans.

(1-->3)-beta-D-Glucans are said to be potential biomedical drugs against bacterial or viral infections and also show antitumour activity. These substances seem to enhance the activity of the immune system, but today there is no accepted mechanism, and not even any agreement on the parameters which influence the activity. Therefore, glucans with different structures and/or varying molar mass were characterized by multi-angle laser-light scattering coupled with size-exclusion chromatography in order to obtain the molar mass distribution and to gain an idea of the structure in solution. After ensuring that all samples were free of pyrogens, the Tumour-necrosis-factor-alpha release activity and the superoxide-anion released from human blood monocytes were measured in groups of samples with comparable polydispersity and degree of substitution. All glucans investigated, regardless of molar mass and solution structure, stimulate the investigated immunological measures more than a commercially available biomedical drug used for comparison. The greatest magnitude of molar mass was found to be about 550,000 g/mol for all the glucans investigated. Contrary to the cited literature, helical structures were not essential, and not even advantageous, for immunological activity.

On-line coupling of flow field-flow fractionation and multiangle laser light scattering for the characterization of macromolecules in aqueous solution as illustrated by sulfonated polystyrene samples.

Seven sulfonated polystyrene standards (18 000-3 000 000 g/mol), taken as model substances for macromolecular polyelectrolytes, were dissolved in aqueous 0.1 M sodium nitrate solution and characterized by multiangle laser light scattering coupled on-line to flow field-flow fractionation. The distributions of molar mass and root mean square radius and the diffusion coefficients were obtained for each sample using a constant field of force for separation. Relationships between molar mass and root mean square radius [〈R(G)(2)〉(z)(0.5) = (2.71 × 10(-)(2))M(w)(0.56)] or diffusion coefficient [D = (7.10 × 10(-)(8))M(w)(-)(0.68)] were calculated. To investigate the static analytical range of this novel hyphenated technique a mixture of all seven samples was fractionated applying a programmed field. The relationship obtained between root mean square radius and molar mass was used to calculate a Mark-Houwink equation [[η]calcd = (2.99 × 10(-)(2))M(w)(0.68)]. To verify this result, the intrinsic viscosities for all samples were measured at low shear rate and found to be in good agreement [[η]calcd = (2.77 × 10(-)(2))M(w)(0.67)].