Nanostructural organization of naturally occurring composites - part II: silica-chitin-based biocomposites

Investigations of the micro- and nanostructures and chemical composition of the sponge skeletons as examples for natural structural biocomposites are of fundamental scientific relevance. Recently, we show that some demosponges (Verongula gigantea, Aplysina sp.) and glass sponges (Farrea occa, Euplectella aspergillum) possess chitin as a component of their skeletons. The main practical approach we used for chitin isolation was based on alkali treatment of corresponding external layers of spicules sponge material with the aim of obtaining alkali-resistant compounds for detailed analysis. Here, we present a detailed study of the structural and physicochemical properties of spicules of the glass sponge Rossella fibulata. The structural similarity of chitin derived from this sponge to invertebrate alpha chitin has been confirmed by us unambiguously using physicochemical and biochemical methods. This is the first report of a silica-chitin composite biomaterial found in Rossella species. Finally, the present work includes a discussion related to strategies for the practical application of silica-chitin-based composites as biomaterials

The design and testing of a dual fiber textile matrix for accelerating surface hemostasis

The standard treatment for severe traumatic injury is frequently compression and application of gauze dressing to the site of hemorrhage. However, while able to rapidly absorb pools of shed blood, gauze fails to provide strong surface (topical) hemostasis. The result can be excess hemorrhage-related morbidity and mortality. We hypothesized that cost-effective materials (based on widespread availability of bulk fibers for other commercial uses) could be designed based on fundamental hemostatic principles to partially emulate the wicking properties of gauze while concurrently stimulating superior hemostasis. A panel of readily available textile fibers was screened for the ability to activate platelets and the intrinsic coagulation cascade in vitro. Type E continuous filament glass and a specialty rayon fiber were identified from the material panel as accelerators of hemostatic reactions and were custom woven to produce a dual fiber textile bandage. The glass component strongly activated platelets while the specialty rayon agglutinated red blood cells. In comparison with gauze in vitro, the dual fiber textile significantly enhanced the rate of thrombin generation, clot generation as measured by thromboelastography, adhesive protein adsorption and cellular attachment and activation. These results indicate that hemostatic textiles can be designed that mimic gauze in form but surpass gauze in ability to accelerate hemostatic reactions

Vascular effects of poly-N-acetylglucosamine in isolated rat aortic rings

Background. Poly-N-acetylglucosamine (p-GlcNAc) is a secretion of marine diatoms that is known to be useful in controlling bleeding. As a component of promoting hemostasis, p-GlcNAc is thought to exert vasoconstrictor effects in arteries. The present study was undertaken to determine whether p-GlcNAc induced a significant vasoconstrictor effect and, if so, what the mechanism of this effect might be. Materials and methods. We examined vascular effects of p-GlcNAc on isolated aortic rings obtained from Sprague-Dawley rats. The rings were suspended in organ baths and precontracted with U46619, a thromboxane A2 mimetic. Results. p-GlcNAc produced a concentration-dependent vasoconstriction over the range of 14 to 100 μg/ml. At a concentration of 100 μg/ml, p-GlcNAc significantly contracted aortic rings by 133 ± 20 mg of developed force (P \u3c 0.01). Neither a deacetylated derivative of p-GlcNAc nor a structurally related macromolecule, chitin, contracted rat aortic rings, indicating a specificity for p-GlcNAc. The vasoconstriction to p-GlcNAc was totally abolished in deendothelialized rat aortic rings, suggesting that an endothelial component is essential to the vasoconstriction. Pretreatment with the endothelin ETA receptor antagonist, JKC-301 (0.5 and 1 μM), significantly diminished p-GlcNAc-induced vasoconstriction by 57 to 61% (P \u3c 0.01). However, p-GlcNAc did not significantly diminish nitric oxide release from rat aortic endothelium. Conclusion. These results provide evidence that p-GlcNAc significantly contracts isolated rat aortic rings via an endothelium-dependent mechanism, partly via enhancement of endothelin-1 release from endothelial cells. © 2001 Elsevier Science

Nanostructural Organization of Naturally Occurring Composites—Part I: Silica-Collagen-Based Biocomposites

Glass sponges, as examples of natural biocomposites, inspire investigations aiming at both a better understanding of biomineralization mechanisms and novel developments in the synthesis of nanostructured biomimetic materials. Different representatives of marine glass sponges of the class Hexactinellida (Porifera) are remarkable because of their highly flexible basal anchoring spicules. Therefore, investigations of the biochemical compositions and the micro- and nanostructure of the spicules as examples of naturally structured biomaterials are of fundamental scientific relevance. Here we present a detailed study of the structural and biochemical properties of the basal spicules of the marine glass sponge Monorhaphis chuni. The results show unambiguously that in this glass sponge a fibrillar protein of collagenous nature is the template for the silica mineralization in all silica-containing structural layers of the spicule. The structural similarity and homology of collagens derived from M. chuni spicules to other sponge and vertebrate collagens have been confirmed by us using FTIR, amino acid analysis and mass spectrometric sequencing techniques. We suggest that nanomorphology of silica formed on proteinous structures could be determined as an example of biodirected epitaxial nanodistribution of amorphous silica phase on oriented fibrillar collagen templates. Finally, the present work includes a discussion relating to silica-collagen-based hybrid materials for practical applications as biomaterials