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Background Alginates have a wide variety of potential clinical applications, including use in cell encapsulation, drug delivery, and tissue engineering. Although the compounds are typically used in the form of a calcium hydrogel, alginates in this form possess several disadvantages, including low biodegradability, induction of foreign body reactions, and cytotoxicity secondary to Ca2+ efflux and contamination with bioincompatible substances. Thus, the goal of the present study was to develop a new method of obtaining sterilized, pure, highly viscous alginate sol from seaweed alginates and to determine its utility as an injectable antiadhesion drug. Methods Viscous injectable pure alginate sol was produced from a commercially available sodium alginate, and its molecular and physical characteristics were analyzed. The biological properties of the viscous injectable pure alginate sol were analyzed using cultured fibroblasts prepared from the dorsal skin of neonatal rats to determine its biocompatibility and its effects on cell proliferation, cell migration, and collagen lattice contraction. Results The mannuronic acid-to-glucuronic acid ratio of viscous injectable pure alginate sol, as determined by nuclear magnetic resonance studies, was 1.2, and its viscosity at 5 percent was 17,800 mPa. Purification used to produce viscous injectable pure alginate sol decreased contamination by insoluble particles by 20 percent and decreased polyphenol concentration by 17 percent. In vitro analyses with cultured fibroblasts demonstrated that viscous injectable pure alginate sol had excellent biodegradability and biocompatibility and that viscous injectable pure alginate sol inhibited fibroblast proliferation and migration. Furthermore, assessment of collagen contraction with floating fibroblast-loaded collagen lattices indicated that viscous injectable pure alginate sol enhanced wound healing in surrounding connective tissues. Conclusions The authors conclude that viscous injectable pure alginate sol can inhibit scar formation by presenting a physical barrier to invading fibroblasts and by enhancing wound healing of surrounding tissues.

We have developed a nerve regeneration material consisting of alginate gel crosslinked with covalent bonds. in the first part of this study, we attempted to analyze nerve regeneration through alginate gel in the early stages within 2 weeks. in the second part, we tried to regenerate cat peripheral nerve by using alginate tubular or non-tubular nerve regeneration devices, and compared their efficacies. Four days after surgery, regenerating axons grew without Schwann cell investment through the partially degraded alginate gel, being in direct contact with the alginate without a basal lamina covering. One to 2 weeks after surgery, regenerating axons were surrounded by common Schwann cells, forming small bundles, with some axons at the periphery being partly in direct contact with alginate. At the distal stump, numerous Schwann cells had migrated into the alginate 8-14 days after surgery. Remarkable restorations of the 50-mm gap in cat sciatic nerve were obtained after a long term by using tubular or non-tubular nerve regeneration material consisting mainly of alginate gel. However, there was no significant difference between both groups at electrophysiological and morphological evaluation. Although, nowadays, nerve regeneration materials being marketed mostly have a tubular structure, our results suggest that the tubular structure is not indispensable for peripheral nerve regeneration.

The fixation of fractured bone with screws is important for orthopedic surgery, however, rigid fixation often cannot be attained in elderly patients with osteoporosis. Recently, we developed a new injectable, nonresorbable bone cement (CAP) that possesses mechanical and biological properties superior to those of polymethylmethacrylate (PMMA) cement. CAP can directly bond with bone without intervening fibrous tissue, and the peak curing temperature is 46°C. In this study, we assessed the effects of CAP and PMMA cement on the augmentation of screw fixation invivo. A cancellous screw was placed in the proximal metaphysis of rabbit tibiae. One side of each tibia was randomly selected to be augmented with CAP or PMMA. The contralateral side received a screw without cement (control). Of the 36 rabbits included in this study, 9 rabbits from each group were sacrificed and the tibial constructs retrieved 1 or 3 months after the initial operation. The screws were then pulled out to failure. The values of the pullout force of the screws augmented with CAP and PMMA were higher than those of the control specimens at both 1 month (319 ± 58 N for CAP vs. 105 ± 41 N for control; p 0.05) after the operation. However, the average increase in the pullout force between CAP and PMMA augmentation was not statistically significant at either time. The values of energy absorption augmented with CAP and PMMA were also higher than those of the control specimens at both 1 month (129 ± 54 N•mm for CAP vs. 19 ± 10 N•mm for control; p 0.05) after the operation. However, there were also no significant differences in energy absorption between the two types of cement augmentation. On the other hand, a significant increase was not observed in stiffness among the CAP, PMMA, and respective control groups at either 1 month (626 ± 133 N/mm for CAP vs. 441 ± 180 N/mm for control; p 0.05) or 3 months (622 ± 144 N/mm for CAP vs. 600 ± 204 N/mm for control; p > 0.05, 633 ± 175 N/mm for PMMA vs. 630 ± 168 N/mm for control; p > 0.05) after the operation, except in the average increase between CAP augmentation and its control 1 month after the operation. These results suggested that a cancellous screw fixation augmented with CAP, as well as PMMA, was effective compared with the unaugmented control in vivo. Because of its biocompatibility and low curing temperature, CAP can be used clinically to augment cancellous screw fixation. © 2000 John Wiley & Sons, Inc. Biomed Mater Res (Appl Biomater) 53: 678–684, 2000

The presence of glycated proteins in the plasma of diabetic patients may play a role in serious complications such as nephritis, retinosis, and nerve disorders. We evaluated the adsorption properties of copolymers of styreneboronic acid and styrenesulfonic acid for glycated protein and glycated lipoprotein. Porous glass with pore sizes of 50 and 100nm and cellulose gel were coated with or bound to the copolymer of styreneboronic acid, styrenesulfonic acid, and glycidyl methacrylate. These adsorbents showed selective adsorptivity for glycated albumin and glycated lipoprotein, depending on their boronic acid content. Copolymer composition affects the adsorption properties in a different manner for glycated albumin and glycated lipoprotein, suggesting that not only boronic acid but also sulfonic acid moieties play an important role in adsorption. The copolymer of styreneboronic acid and hydroxyethyl methacrylate had a smaller adsorption capacity than the copolymer of styreneboronic acid and styrenesulfonic acid without positive participation of the hydroxyethyl methacrylate moiety, which also showed the need for sulfonic acid in selective adsorption. Furthermore, these adsorbents had less capacity to activate the intrinsic blood coagulation cascade. Therefore, it may be possible to use these adsorbents to prevent the complications of diabetes by plasmapheresis.

Clinical treatment of recurrent symptoms following peripheral nerve decompression is problematic. Removal of scar tissue can produce an inappropriately pronounced healing response and thereby lead to more serious tethering or compression of the nerve. The goal of the present study was to test the ability of viscous injectable pure alginate sol to prevent perineurial adhesion using a rat neurolysis model.The antiadhesive effect of viscous injectable pure alginate sol after neurolysis was evaluated histologically and biomechanically. A total of 40 rats were used in this study. The viscous injectable pure alginate sol was applied topically on the right side after external (six rats) or extensive internal (six rats) neurolysis, whereas the left side received no treatment. The nerves were harvested over 6 weeks, and histologic analysis was performed with hematoxylin and eosin staining and Masson trichrome staining. Functional analysis of the blood and perineurial barriers was also evaluated with Evans blue albumin (four rats). Sixteen rats were used for biomechanical analysis, and eight rats were used as a control group. The results were analyzed statistically using a post hoc test.Histologic examination showed that the use of viscous injectable pure alginate sol was associated with excellent biocompatibility and strong inhibition of perineurial granulation. Viscous injectable pure alginate sol was absorbed completely within 6 weeks without inducing inflammation. In addition, viscous injectable pure alginate sol enhanced repair of the perineurium associated with regeneration of epithelial-like cell layers, a key structure necessary for barrier function of the inner layer of the perineurium. Functional analysis with Evans blue albumin clearly demonstrated that, although blood nerve barrier function recovered by 6 weeks postoperatively in all nerves, the perineurial barrier function recovered only in the sol-treated nerves. Biomechanical study showed a significant antiadhesive effect of viscous injectable pure alginate sol.Viscous injectable pure alginate sol inhibited adhesion formation around nerves and enhanced regeneration of the perineurium with barrier function. Because excessive perineurial fibrosis and tethering at the neurolysis or neurorrhaphy site is a common postoperative problem in peripheral nerve surgery, viscous injectable pure alginate sol appears to have potentially broad clinical applications.

Graft-type copolymers composed of hydrophilic poly(hydroxyethyl methacrylate) (PHEMA) as a backbone and a small amount of hydrophobic poly(methylmethacrylate) (PMMA) as a long branch exhibit excellent thromboresistance. The interrelationship between the thromboresistance and microstructure of the graft-type copolymers as well as the water structure in the hydrated polymers has been investigated. It was concluded that both the structure of hydrophobic domain dispersed in the hydrophilic matrix and the water bound to the polymer may be responsible for the excellent thromboresistance of the graft-type copolymers.

Polarography and electron transfer equilibria of some ferrocene-containing polymers were studied in comparison with small-molecule analogs. The oxidation half-wave potentials of polyvinylferrocene and polydivinylferrocene (almost completely cyclized) in CH2Cl2 were close to those of ferrocene and [3]ferrocenophane, respectively. This is in line with structural similarity. Only one oxidation step was observed in the polarogram of triferrocenylbenzene and polyethynylferrocene, suggesting that the electronic interactions between ferrocene units are small in these compounds. Electron transfer equilibrium was observed between ferrocene units in polymer and iodine. Equilibrium constants of the [3]ferrocenophane unit were greater than those of the unbridged ferrocene unit. The ferrocene unit in polymer showed greater equilibrium constants than those of their small-molecule analogs.

Vinylferrocene was shown to undergo readily cationic polymerization by FRIEDEL-CRAFTS and other cationic catalysts. The polymers obtained possessed rather low molecular weights, the highest being 3500. In spite of the high reactivity of the ferrocene nucleus towards electrophilic substitution, no mode of propagation other than vinyl addition was detected when the infrared spectra of polymers prepared by cationic and free radical reactions were compared. The electronic spectra of polyvinylferrocene and its oxidized form were similar to those of ferrocene and ferricinium ion, respectively. In the cationie copolymerization with styrene, the latter was incorporated into the polymer only when the styrene content in the monomer feed exceeded 90%. The copolymerization with vinyl isobutyl ether (M2) by BF3OEt2 in toluene at 0°C gave the reactivity ratios: r1 = 0.1 ± 0.1, r2 = 9.7 ± 1.0. The high cationic reactivity of vinylferrocene is consistent with the stability of the α-ferrocenylearbonium ion inferred from solvolysis and other reactions. Eswurde gezeigt, das sich Vinylferrocen durch FRIEDEL-CRAFTS- und andere kationische Katalysatoren leicht polymerisieren last. Die erhaltenen Polymeren hatten jedoch nur maximale Molekulargewichte von 3500. Trotz der hohen Reaktivitat des Ferrocenkerns gegenuber einer elektrophilen Substitution wurde keine andere Wachstumsreaktion gefunden als die Vinyladdition, wie man durch Vergleich der IR-Spektren der durch kationische Polymerisation erhaltenen Polymeren mit den durch Radikalpolynierisation erhaltenen feststellen konnte. Die Elektronenspektren des Polyvinylferrocens und seiner oxydierten Form gleichen denen des Ferrocens bzw. des Ferriciniumions. Bei der kationischen Copolymerisation mit Styrol wird dieses nur dann in nennenswerter Menge eingebaut, wenn der Styrolgehalt in der Monomerenmischung 90% ubersteliat. Die Copolymerisation mit Vinylisobutylather (M2) durch BF3O(C2H5)2 in Toluol bei 0°C ergab die Copolymerisations-parameter: r1 = 0,1 ± 0,1, r2 = 9,7 ± 1,0. Die hohe kationische Reaktivitat des Vinylferrocens steht in Ubereinstimmung mit der aus der Solvolyse und anderen Reaktionen abgeleiteten Stabilitat des α-Ferrocenylearboniumions.

Polymerizations of ethinylferrocene were carried out with ZIEGLER-type catalysts. AlR3-TiCl4 catalysts gave predominantly cyclic trimers, i.e., 1.2.4- and 1.3.5-triferrocenylbenzene, and AlR3-Ti(OBu)4 catalysts gave linear polymers of comparatively low molecular weight (1000-3500). Basic organic additives like pyridine or triethylamine showed limited influence on the yield and the product distribution. The polyene may contain some irregular structures. On the other hand, polyethinylferrocene obtained by dehydrative condensation of acetylferrocene was shown by NMR spectroscopy to contain considerable amounts of aliphatic hydrogen. Polymerisationen von Athinylferrocen wurden mit ZIEGLER-Katalysatoren durchgefuhrt. AlR3-TiCl4-Katalysatoren ergaben vorwiegend cyclische Trimere, d. h. 1.2.4- und 1.3.5-Triferrocenylbenzol; mit AlR3-Ti(OC4H9)4-Katalysatoren erhielt man lineare Polymere von verhaltnismasig niedrigem Molekulargewicht (1000-3500). Der Zusatz von organischen Basen wie Pyridin oder Triathylamin zeigte einen begrenzten Einflus auf die Ausbeute und die Verteilung des Endprodukts. Das Polyen kann einige unregelmasige Strukturen enthalten; andererseits wurde NMR-spektroskopisch nachgewiesen, das Polyathinylferrocen, das durch wasserabspaltende Kondensation von Acetylferrocen erhalten worden war, betrachtliche Mengen aliphatischen Wasserstoffs enthalt.

1,1′-Divinylferrocene was polymerized with BF3OEt2 and AIBN initiators. Polymers were separated into benzene-soluble and benzene-insoluble fractions, the latter probably being crosslinked. The polymers obtained with BF3OEt2 were shown by infrared and NMR spectroscopy to contain both cyclized (70–80%) and uncyclized units, whereas the radical polymer consisted of more than 96% cyclized units. The benzene-soluble fraction of the cationically obtained polymer softened at temperatures below 150°C, but the insoluble fraction decomposed at 240°C. The radical polymers were stable up to 250–280°C (dec).

Cationic cyclopolymerizations of 1.1′-divinylferrocene with LEWIS acids and alkylaluminum catalysts were performed under various conditions. The cyclization constant rc (the ratio of rate constants of the intramolecular cyclization and the intermolecular propagation) was determined by applying the equation previously empolyed for cyclopolymerizations of o-divinylbenzene. The rc value (0°C, CH2Cl2) was approximately 1 mole/l. with BF3OEt2, SnCl4, and TiCl4, but increased to 1.8 to 2.8 mole/l. with aluminum-containing catalysts. It also increased (from 0.67 to 1.49 mole/l.) with increasing polarity of polymerization solvents. The intramolecular cyclization was shown to possess an activation energy higher than that of the intermolecular propagation by 1.2 to 1.5 kcal/mole (AlEtCl2/C6H5CH2Cl, CH2Cl2). These data were interpreted as follows: the intramolecular cyclization of the growing carbonium ion pair becomes more favorable, as the tightness of the ion pair decreases, because of the increase in reactivity. Thermal behaviors of several polymers were examined by differential scanning calorimetry and thermogravimetric analysis, and it was suggested that extensive crosslinking occurred in the molten polymer at about 200°C. Die kationische Cyclopolymerisation von 1.1′-Divinylferrocen wurde unter verschiedenen Bedingungen mit LEWIS-Sauren und Alkylaluminium-Katalysatoren durchgefuhrt. Die Cyclisierungskonstante rc (sie gibt das Verhaltnis der Geschwindigkeitskonstante der intramolekularen Cyclisierung zu der der intermolekularen Wachstumsreaktion wieder) wurde unter Heranziehung der kurzlich fur die Cyclopolymerisation von o-Divinylbenzol hergeleiteten Beziehung ermittelt. Der rc-Wert (0°C, CH2Cl2) betrug ungefahr 1 Mol/l fur BF3O(C2H5)2, SnCl4 und TiCl4 als Katalysatoren; er stieg jedoch fur Katalysatoren, die Aluminium enthielten, auf 1,8–2,8 Mol/l an. Mit steigender Polaritat des fur die Polymerisation eingesetzten Losungsmittels nimmt der rc-Wert ebenfalls zu (von 0,67–1,49 Mol/l). Die intramolekulare Cyclisierung besitzt eine um 1,2–1,5 kcal/Mol (AlC2H5Cl2/C6H5CH2Cl, CH2Cl2) grosere Aktivierungsenergie als die intermolekulare Wachstumsreaktion. Diese Daten wurden wie folgt interpretiert: die intramolekulare Cyclisierungsreaktion des wachsenden Carbonium-Ionenpaares wird in dem Mase begunstigt, in dem die Festigkeit der Ionenpaarbindung geschwacht wird; im gleichen Mase nimmt durch die Schwachung der Ionenpaarbindung die Reaktivitat zu. Das thermische Verhalten verschiedener Polymerer wurde mit der Differential-Thermoanalyse und thermogravimetrischen Analyse untersucht. Diese Untersuchungen lassen das Anftreten umfangreicher Vernetzungen innerhalb des geschmolzenen Polymeren bei 200°C naheliegend erscheinen.

To prevent engine scuffing in the field, a new laboratory test called the Hot Tube Test has been established in order to evaluate the high temperature stability of diesel engine oils. In a strip mining application field test using 47 bulldozers powered by the same engine type, half of the engines suffered from piston scuffing failures when operated on a variety of commercially available API CD quality SAE 30 Grade engine oils. All the field test oils have been investigated using the Hot Tube Test, and an analysis of the results indicates that it would be possible to accurately predict scuffing failures by this test method. Furthermore, the reliability of this analysis has been verified by bench engine testing on reference oils. The reasons why the Hot Tube Test predicts the anti-scuffing performance of engine oils are discussed.