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

Anti-Bacterial Effects of Poly-N-Acetyl-Glucosamine Nanofibers in Cutaneous Wound Healing: Requirement for Akt1

Treatment of cutaneous wounds with poly-N-acetyl-glucosamine nanofibers (sNAG) results in increased kinetics of wound closure in diabetic animal models, which is due in part to increased expression of several cytokines, growth factors, and innate immune activation. Defensins are also important for wound healing and anti-microbial activities. Therefore, we tested whether sNAG nanofibers induce defensin expression resulting in bacterial clearance.The role of sNAG in defensin expression was examined using immunofluoresence microscopy, pharmacological inhibition, and shRNA knockdown in vitro. The ability of sNAG treatment to induce defensin expression and bacterial clearance in WT and AKT1-/- mice was carried out using immunofluoresent microscopy and tissue gram staining. Neutralization, using an antibody directed against β-defensin 3, was utilized to determine if the antimicrobial properties of sNAG are dependent on the induction of defensin expression.sNAG treatment causes increased expression of both α- and β-type defensins in endothelial cells and β-type defensins in keratinocytes. Pharmacological inhibition and shRNA knockdown implicates Akt1 in sNAG-dependent defensin expression in vitro, an activity also shown in an in vivo wound healing model. Importantly, sNAG treatment results in increased kinetics of wound closure in wild type animals. sNAG treatment decreases bacterial infection of cutaneous wounds infected with Staphylococcus aureus in wild type control animals but not in similarly treated Akt1 null animals. Furthermore, sNAG treatment of S. aureus infected wounds show an increased expression of β-defensin 3 which is required for sNAG-dependent bacterial clearance. Our findings suggest that Akt1 is involved in the regulation of defensin expression and the innate immune response important for bacterial clearance. Moreover, these findings support the use of sNAG nanofibers as a novel method for enhancing wound closure while simultaneously decreasing wound infection

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

Original Article Using poly-N-acetyl glucosamine gel matrix to deliver IL-12 with antischistosomasis vaccination

Background: Interleukin (IL)-12 is a potential adjuvant in a variety of diseases including schistosomiasis. The clinical use of IL-12, however, is limited by the toxicity associated with its systemic administration. We have developed a novel delivery system (designated F2 gel matrix) composed of poly-N-acetyl glucosamine that has the dual properties of sustaining the release of proteins (e.g. interleukins) and adjuvant effects. The main aim of this study was to use a mouse model to test whether IL-12 released from F2 gel can induce adjuvant effects in the schistosomiasis setting as compared to those obtained after systemic delivery of IL-12. Methodology: First, we compared the toxicity induced by paracrine (delivered by F2 gel) and systemic IL-12. Second, we compared the induction of cytokines induced by paracrine and systemic IL-12. Third, we compared the adjuvant effects of paracrine and systemic IL-12based prophylactic vaccination against schistosomiasis using soluble worm antigen preparation (SWAP). Results: IL-12 released from F2 gel did not induce significant toxicity measured by alanine aminotransferase (ALT). We found similar serum levels of IFN-γ, TNF-α and IL-2 after paracrine and systemic IL-12 treatments. We also found that vaccination with F2 gel/SWAP/IL-12 induced higher anti-schistosomal effects than IL-12/SWAP as evidenced by 1) the decrease in the total liver egg counts; 2) the reduction in the granuloma size and fibrotic reaction in the liver; and 3) the amelioration of the liver functions. Conclusion: Collectively, these results indicate that IL-12-F2 gel delivery approach could be considered as a potential strategy for th