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PubMed1983

Wound treatment with Sorbsan--an alginate fibre dressing.

This highly absorbent, biodegradable dressing derived from seaweed can be successfully applied to cleanse a wide variety of secreting lesions. The high absorption of exudate is achieved via strong hydrophilic gel formation and this serves to control wound secretion levels and to minimize bacterial contamination. Alginate fibres trapped in a wound are readily biodegraded and do not have to be removed thus avoiding disturbance of granulation tissue formation. Additional features are odour remission, conformability and ready removal of tissue adherent material.

Alginates↗

PubMed1985

Sodium alginate as a mould release agent.

The use of sodium alginate as a mould release agent during the casting of epoxy or polyester resins in plaster moulds is discussed. The optimal concentration of a retarder is determined, taking into consideration the setting behaviour and the adhesive bond strength. The above characteristics are critical for the application and efficiency of the coating.

Alginates↗

PubMed1995

Subperiosteal behaviour of alginate and cellulose wound dressing materials.

A histological comparison was undertaken of the tissue response to a new sodium calcium alginate material (Kaltostat) and an oxidized regenerated cellulose wound dressing (Surgicel) when implanted between bone and periosteum in the jaws at intervals of up to 24 wk. Both biomaterials caused a foreign body reaction, persisting up to 12 wk after surgery. New bone formation occurred along the surface of the mandible in some specimens, but was not apparently related to the implants. It was concluded that the implantation of Kaltostat or Surgicel between bone and periosteum in the jaws caused a delay in wound healing, and had no effect on bone induction.

Alginates↗

PubMed1993

Tissue response to a haemostatic alginate wound dressing in tooth extraction sockets.

Kaltostat is a new haemostatic wound dressing composed of non-woven sodium calcium alginate fibres, and was originally developed to cover exposed wounds of the skin. A histopathological study was undertaken to determine the tissue response to Kaltostat in healing tooth sockets, to obtain a comparison with oxidised regenerated cellulose (Surgicel). Tooth sockets filled with blood clot acted as controls. The results showed that both biomaterials delayed wound healing in the early phase (1-4 weeks), giving rise to foreign body reactions. At 12 weeks there was little difference between the control sockets and the sockets containing the test materials, although remnants of retained dressing materials were identified. Healing of the tooth sockets was complete at 24 weeks.

Alginates↗

PubMedDate not supplied

Gelatine-alginate complex gel: a new acoustically tissue-equivalent material.

Methods are described for the preparation of gelatine-alginate complex gels and measurements are reported of certain of their acoustic and physical properties relevant to their use as tissue-equivalent phantoms in medical ultrasonics applications. Speed of sound at 20 degrees C is 1520 ms-1 with a coefficient of +2.6 ms-1/degrees C. Attenuation coefficient in unloaded gel is 0.12 dB cm-1 MHz-1 (varying approximately linearly with frequency) but can readily be increased to at least 0.5 dB cm-1 MHz-1 by loading the gel with polyethylene or lipid microspheres. Volume stability under conditions of water immersion without an impermeable boundary layer is within about +/- 2% over a 300 day period, an improvement by a factor of at least 25 on both simple and cross-linked gelatine gels, and stability against chemical or bacterial degradation can also readily be maintained.

Alginates↗

PubMed1996

The use of calcium alginate dressings in deep hand burns.

Deep burns of the hand are a common serious surgical problem with major occupational and economic implications. Control of haemorrhage during excision and grafting is difficult and postoperative haematoma may reduce graft take. Following excision, important deep structures such as extensor tendons or joints may be exposed. Such tissues do not take free skin grafts satisfactorily. We have found calcium alginate dressings can be of immense help in minimizing these technical problems. We describe our experience in one patient; three other patients have been treated with equal success.

Adolescent↗

PubMed1989

Nucleotide sequence of a regulatory region controlling alginate synthesis in Pseudomonas aeruginosa: characterization of the algR2 gene.

Alginate (Alg), an exopolysaccharide with strong gelling properties, is produced by Pseudomonas aeruginosa primarily during its infection of the cystic fibrosis (CF) lung. The alg genes are normally not expressed in other environments. The promoter for a critical Alg biosynthetic gene, algD, encoding GDP-mannose dehydrogenase, is activated only under conditions reminiscent of the CF lung (i.e., under high osmolarity), and at least two regulatory genes, algR1 and algR2, have been implicated in this activation process. The physical mapping of a 4.4-kb region harboring algR2 has been accomplished and the complete nucleotide sequence of this fragment, including that of algR2, is presented. The cloning and complementation experiments also demonstrate the presence, on this fragment, of regulatory gene(s) different from algR1 and algR2. The expression of the algR2 gene allows a high level of activation of the algD promoter in Escherichia coli, in the presence of algR1 in a high osmotic environment, suggesting that the AlgR2 and AlgR1 proteins act cooperatively to activate the algD promoter. Hyperexpression of the algR2 gene from the tac promoter also allows the conversion of nonmucoid cells of strain 8822, a spontaneous revertant of the mucoid CF isolate strain 8821, back to mucoidy, but not that of the clinical isolate, strain PAO1.

Alcohol Oxidoreductases↗

PubMed1991

Nucleotide sequence and expression of the algE gene involved in alginate biosynthesis by Pseudomonas aeruginosa.

Alginate (Alg), a random polymer of mannuronic acid and glucuronic acid residues, is synthesized and secreted by Pseudomonas aeruginosa primarily during its infection of the lungs of cystic fibrosis patients. The molecular biology and biochemistry of the enzymatic steps leading to the production of the Alg precursor GDP-mannuronic acid have been elucidated, but the mechanism of polymer formation and export of Alg are not understood. We report the nucleotide sequence of a 2.4-kb DNA fragment containing the algE gene, previously designated alg76, encoding the AlgE protein (Mr 54,361) that is believed to be involved in these late steps of Alg biosynthesis. Expression of algE appears to occur from its own promoter. The promoter region contains several direct and inverted repeat sequences and shares structural similarity with promoters of several other alg genes from P. aeruginosa. In addition, the AlgE protein was overproduced from the tac promoter in P. aeruginosa. N-terminal amino acid sequence analysis showed that the polypeptide contains a signal peptide which is cleaved to form the mature protein during AlgE export from the cell cytoplasm.

Alginates↗

PubMed1986

Nonfatal bacteremia caused by a mucoid, alginate-producing strain of Pseudomonas aeruginosa.

The first case of mucoid Pseudomonas aeruginosa bacteremia is reported in a hospitalized 78-yr-old woman with drug-induced hepatitis attributed to antituberculous therapy. The bacteremia was successfully treated with tobramycin and carbenicillin. Furthermore, the extracellular material of this mucoid strain was extracted, purified, and characterized as an alginate of high molecular weight, similar to that of mucoid Pseudomonas aeruginosa strains from cystic fibrosis.

Aged↗

PubMed2006

Alginate-chaperoned facile refolding of Chromobacterium viscosum lipase.

Urea denatured lipase from Chromobacterium viscosum lipase could be refolded by addition of alginate with high guluronic acid content. The refolded molecule could be recovered by affinity precipitation. This approach resulted in recovery of 80% (of original activity) as compared to classical dilution method which gave only 21% activity recovery. Dynamic light scattering showed that binding required about 45 min and activity data obtained from affinity precipitation experiments indicated that refolding was almost instantaneous after binding. Circular dichroism (CD) and fluorescence data showed that refolded molecule was identical to the native molecule. It also showed that refolding takes place at the binding stage and not at the precipitation stage. Preliminary studies showed that the refolding strategy worked equally well with lipases from wheat germ and porcine pancreas.

Alginates↗

PubMed2006

A bioconjugate of Pseudomonas cepacia lipase with alginate with enhanced catalytic efficiency.

A bioconjugate of Pseudomonas cepacia lipase with alginate was prepared by simple adsorption. Atomic force microscope (AFM) images showed that this bioconjugate resulted from adsorption rather than entrapment of the enzyme as enzyme molecules were visible on the gel surface. The soluble bioconjugate exhibited increased enzyme activity in terms of high effectiveness factor (effectiveness factor was 3 for the immobilized preparation) and greater Vmax/Km value (Vmax/Km increased 25 times upon immobilization). This constitutes one of the less frequently observed instances of lipase activation by lid opening as a result of binding to a predominantly hydrophilic molecule. The bioconjugate was also more stable at 55 degrees C as compared to the free enzyme and could be reused for oil hydrolysis up to 4 cycles without any loss in activity. Fluorescence emission spectroscopy showed that the immobilized enzyme had undergone definite conformational changes.

Adsorption↗

PubMed2005

Characterization of conformational epitope of alginate-derived polymannuronates by surface plasmon resonance.

In the present study, we developed a mAb to alginate-derived polymannuronates (ADPM) and examined the antigenic epitopes using surface plasmon resonance (SPR) in conjunction with a large panel of oligomannuronate probes. We found that tetrasaccharide is the minimum-binding unit, and that increases in chain length from the tetrasaccharide to the heptsaccharide further enhance monovalent binding. A sharp increase in affinity was observed when increasing from the octasaccharide to the cosasaccharide, which is due to a further enhancement of the individual antigenic epitope combined with multivalency. Kinetic binding studies further suggested that the conformational epitope is discontinuous and infrequent and that a C6-carboxyl group is important in maintaining the conformational epitope. Moreover, CD analysis revealed there were conformational structures in epitopes. The data support our hypothesis that the conformational epitope for the mAb may be an extended helical segment of ADPM. ADPM exists mainly in linear form, but it can infrequently and spontaneously form extended helices. Although helices are not prevalent in ADPM, the immune system preferentially selects these conformational epitopes because they are unique. Together, our results indicate that the antigenic epitopes in beta-d-mannuronates are conformational and require C6-carboxyl groups.

Alginates↗

PubMed2004

Chondrogenic differentiation of adipose-derived adult stem cells in agarose, alginate, and gelatin scaffolds.

The differentiation and growth of adult stem cells within engineered tissue constructs are hypothesized to be influenced by cell-biomaterial interactions. In this study, we compared the chondrogenic differentiation of human adipose-derived adult stem (hADAS) cells seeded in alginate and agarose hydrogels, and porous gelatin scaffolds (Surgifoam), as well as the functional properties of tissue engineered cartilage constructs. Chondrogenic media containing transforming growth factor beta 1 significantly increased the rates of protein and proteoglycan synthesis as well as the content of DNA, sulfated glycosaminoglycans, and hydroxyproline of engineered constructs as compared to control conditions. Furthermore, chondrogenic culture conditions resulted in 86%, and 160% increases ( p < 0.05 ) in the equilibrium compressive and shear moduli of the gelatin scaffolds, although they did not affect the mechanical properties of the hydrogels over 28 days in culture. Cells encapsulated in the hydrogels exhibited a spherical cellular morphology, while cells in the gelatin scaffolds showed a more polygonal shape; however, this difference did not appear to hinder the chondrogenic differentiation of the cells. Furthermore, the equilibrium compressive and shear moduli of the gelatin scaffolds were comparable to agarose by day 28. Our results also indicated that increases in the shear moduli were significantly associated with increases in S-GAG content ( R2 = 0.36, p < 0.05 ) and with the interaction between S-GAG and hydroxyproline ( R2 = 0.34, p < 0.05 ). The findings of this study suggest that various biomaterials support the chondrogenic differentiation of hADAS cells, and that manipulating the composition of these tissue engineered constructs may have significant effects on their mechanical properties.

Adipose Tissue↗

PubMed2005

Alginate microcapsules prepared with xyloglucan as a synthetic extracellular matrix for hepatocyte attachment.

In this study, xyloglucan (XG) was used as a new synthetic extracellular matrix (ECM) for primary mouse hepatocyte attachment in Ca-alginate (AL) capsules. The rates of hepatocytes adhesion onto collagen type I-, XG-coated and uncoated polystyrene (PS) surface were 89.1%, 91.1% and 25.5%, respectively, at 4 h after incubation at 37 degrees C. From the inhibition study in a cell adhesion assay, the adhesion rates of freshly isolated hepatocytes and preincubated hepatocytes with 20 mm galactose onto the XG-coated surface were 55.7 and 17.3%, respectively, after 30 min incubation at 37 degrees C. Flow cytometric analysis showed that the internalization of XG by freshly isolated hepatocytes was stronger than preincubated hepatocytes with 20 mm galactose. The concentration of XG in AL/XG capsules to perform the best liver-specific functions was 0.5 mg/ml, where the highest albumin secretion rates were obtained. The albumin secretion, ammonia elimination rates and cell viability of hepatocytes were slowly decreased with culture time in AL/XG capsules, whereas those were rapidly decreased in AL capsules, indication of the more rapid formation of hepatocyte spheroids in AL/XG capsules than in AL capsules. More than 70% of the seeded hepatocytes in AL/XG capsules participated in spheroid formation after 2 days, whereas most hepatocytes in AL capsules remained as single cells and only a few cells began to form aggregates after 3 days. Intercellular molecule genes, such as connexin (Cx) 32 and E-cadherin, of hepatocyte spheroids in AL or AL/XG capsules were detected by reverse transcriptase-polymerase chain reaction. Cx32 and E-cadherin genes in AL/XG capsules were more rapidly reexpressed and expressed, respectively, than in AL ones. The results suggest that the multicellular spheroid formation of hepatocytes can enhance the liver-specific functions in the three-dimensional space in the presence of XG as a new synthetic ECM owing to the specific interaction between the galactose moieties of XG and asialoglycoprotein receptors of hepatocytes.

Alginates↗

PubMed2005

Inflammatory response to peritoneal implantation of alginate-poly-L-lysine microcapsules.

A thorough understanding of the mechanisms involved in the host reaction to alginate-poly-L-lysine microcapsules (HRM) is important to design methods for the evaluation, selection, and development of biocompatible biomaterials and microcapsules or treatments to control this reaction. The objective of this study was to identify those immune cells and cytokines involved in the pathogenesis of the HRM. The total and differential cell counts were evaluated, and the mRNA expression of TNF-alpha, IL-1beta, IL-6 and TGF-beta1 was measured in peritoneal washings at 3, 17, 48, 96 and 168 h after saline or microcapsule injections. Neutrophil number and IL-1beta and IL-6 m-RNA expression presented an early transient increase, with no differences between saline and microcapsule injections, suggesting a reaction to the procedure. Macrophages, lymphocytes and TNF-alpha were significantly more activated over a longer period of time, after microcapsule implantation than saline injection. They are likely involved in transforming the reaction into a chronic inflammatory process. TGF-beta1 and IL-1beta presented a late (day 7) significant increase after microcapsule but not saline injections. They are likely involved in transforming the reaction into a fibrogenic process. These results suggest that macrophages, lymphocytes, TNF-alpha, IL-1beta and TGF-beta1 play a role in the pathogenesis of the HRM.

Alginates↗

PubMed2005

The in vitro regulation of ovarian follicle development using alginate-extracellular matrix gels.

The extracellular matrix (ECM) provides a three-dimensional structure that promotes and regulates cell adhesion and provides signals that direct the cellular processes leading to tissue development. In this report, synthetic matrices that present defined ECM components were employed to investigate these signaling effects on tissue formation using ovarian follicle maturation as a model system. In vitro systems for follicle culture are being developed to preserve fertility for women, and cultures were performed to test the hypothesis that the ECM regulates follicle maturation in a manner that is dependent on both the ECM identity and the stage of follicle development. Immature mouse follicles were cultured within alginate-based matrices that were modified with specific ECM components (e.g., laminin) or RGD peptides. The matrix maintains the in vivo like morphology of the follicle and provides an environment that supports follicle development. The ECM components signal the somatic cells of the follicle, affecting their growth and differentiation, and unexpectedly also affect the meiotic competence of the oocyte. These effects depend upon both the identity of the ECM components and the initial stage of the follicle, indicating that the ECM is a dynamic regulator of follicle development. The development of synthetic matrices that promote follicle maturation to produce meiotically competent oocytes may provide a mechanism to preserve fertility, or more generally, provide design principles for scaffold-based approaches to tissue engineering.

Alginates↗

PubMed2005

Low-intensity pulsed ultrasound stimulates cell proliferation and proteoglycan production in rabbit intervertebral disc cells cultured in alginate.

Intervertebral disc degeneration, one of the major causes of low-back pain, is known to result from alteration in biosynthesis of proteoglycan in the disc. Therefore, upregulating the synthesis of proteoglycan in intervertebral disc cells may be one approach in treating disc degeneration. Based on the finding that low-intensity pulsed ultrasound stimulates proteoglycan synthesis in rat chondrocytes, we investigated whether low-intensity pulsed ultrasound stimulates biological properties of rabbit intervertebral disc cells in vitro. Nucleus pulposus cells and annulus fibrosus cells isolated from rabbits were cultured in alginate beads. Cells were stimulated for 20 min each day for 5-12 days, starting on the third day after seeding. An ultrasound signal consisting of a 200 micros burst sine wave of 0.5 MHz repeating at 1 kHz, with an intensity of 0, 7.5, 15, 30, 60, 120 mW/cm2 spatial and temporal average, was applied. DNA and proteoglycan synthesis were evaluated by measuring [3H]-thymidine and [35S]-sulfate incorporation. DNA and proteoglycan content in beads were measured by Hoechst 33258 dye method and dimethylmethylene blue assay. Results demonstrated positive effects on DNA synthesis and content, following low-intensity pulsed ultrasound stimulation with intensities of 7.5 and 15 mW/cm2. Furthermore, ultrasound stimulation significantly upregulated [35S]-sulfate incorporation and proteoglycan content compared to the control group, following 5 days of stimulation in both nucleus pulposus and annulus fibrosus cells. These findings suggest the possible application of low-intensity pulsed ultrasound in biological repair of intervertebral disc degeneration.

Alginates↗

PubMed2005

Evaluation of the effect of incorporation of dibutyryl cyclic adenosine monophosphate in an in situ-forming hydrogel wound dressing based on oxidized alginate and gelatin.

Cyclic adenosine monophosphate (cAMP) has long been regarded as a second messenger and a regulator of human keratinocyte proliferation. To explore more effective wound management, dibutyryl cyclic adenosine monophosphate (DBcAMP), a lipophilic analog of cAMP was incorporated into an in situ-forming hydrogel wound dressing based on periodate-oxidized alginate and gelatin. In vitro release of DBcAMP from the matrix into phosphate buffered saline was slow and increased with time. Only 50-60% of the compound was released into the medium over a period of 2 days suggestive of a sustained release into the wound bed over a period of few days. The wound-healing efficacy of the DBcAMP-incorporated dressing was evaluated on experimental full-thickness wounds in a rat model. It was found that dressing promoted wound healing leading to complete re-epithelialization of wounds within 10 days, whereas control wounds took 15 days for complete re-epithelialization. Data obtained in this study showed that the presence of DBcAMP accelerated healing and re-epithelialization of full-thickness wounds.

Alginates↗