Heike Meissner

Three-dimensional chitin-based scaffolds from Verongida sponges (Demospongiae: Porifera). Part I. Isolation and identification of chitin.

Marine invertebrate organisms including sponges (Porifera) not only provide an abundant source of biologically active secondary metabolites but also inspire investigations to develop biomimetic composites, scaffolds and templates for practical use in materials science, biomedicine and tissue engineering. Here, we presented a detailed study of the structural and physico-chemical properties of three-dimensional skeletal scaffolds of the marine sponges Aiolochroia crassa, Aplysina aerophoba, A. cauliformis, A. cavernicola, and A. fulva (Verongida: Demospongiae). We show that these fibrous scaffolds have a multilayered design and are made of chitin. (13)C solid-state NMR spectroscopy, NEXAFS, and IR spectroscopy as well as chitinase digestion and test were applied in order to unequivocally prove the existence of alpha-chitin in all investigated species.

Three-dimensional chitin-based scaffolds from Verongida sponges (Demospongiae: Porifera). Part II: Biomimetic potential and applications

In order to evaluate the biomedical potential of three-dimensional chitinous scaffolds of poriferan origin, chondrocyte culturing experiments were performed. It was shown for the first time that freshly isolated chondrocytes attached well to the chitin scaffold and synthesized an extracellular matrix similar to that found in other cartilage tissue engineering constructs. Chitin scaffolds also supported deposition of a proteoglycan-rich extracellular matrix of chondrocytes seeded bioconstructs in an in vivo environment. We suggest that chitin sponge scaffolds, apart from the demonstrated biomedical applications, are highly optimized structures for use as filtering systems, templates for biomineralization as well as metallization in order to produce catalysts.

A modern approach to demineralization of spicules in glass sponges (Porifera: Hexactinellida) for the purpose of extraction and examination of the protein matrix

Glass sponges of the class Hexactinellida are a group of the most ancient multicellular animals, whose fossil remnants from the early Proterozoic have been registered. In order to demineralize the skeletal structures of the glass sponge Hyalonema sieboldi, we have used for the first time a strategy of slow leaching of the silicon-bearing component, based on the usage of alkaline solutions of sodium hydroxide, sodium dodecyl sulfate, and an anionic biosurfactant of a rhamnolipid nature. The obtained data unequivocally corroborate the presence of a fibrillar protein matrix functioning as a basis for silicon biomineralization in the basal spicules of H. sieboldi. Also, it has been found for the first time that the protein matrix is constructed of a collagenous protein. The technical approach proposed here might appear important for the study of the structural organization of skeletons in other silicon-bearing animals and, in an applied aspect, to work out new biomaterials for implantology and biocomposites, in order to use the latter as bioactive additives.

Stability of fixation of diacapitular fractures of the mandibular condylar process by ultrasound-aided resorbable pins (SonicWeld Rx® System) in pigs

To assess the stability of osteosynthesis in diacapitular condylar fractures we compared fixation using ultrasound-aided resorbable pins with poly-(D,L)-lactide (SonicWeld® Rx, KLS Martin, Tuttlingen, Germany) with that of titanium screws in 20 pig mandibles, 10 in each group. Isolated diacapitular fractures were created using a surgical chisel. Ten fractures were each repositioned and fixed by two pins (17 and 11 mm long, 2.1mm in diameter), and 10 fractures were fixed by two titanium screws of equal length, 2.0mm in diameter. Shear tests were done immediately after treatment to measure the maximum force to disrupt the fixation. Fixation with pins resisted mean shear forces of 310N until the pins fractured, whereas fixation with titanium screws failed at 918N when the screws pulled out of the bone. Long-term stability and resorption of pins will have to be analysed in an in vivo study.

Bone block fixation by ultrasound activated resorbable pin osteosynthesis: a biomechanical in vitro analysis of stability.

OBJECTIVES The aim of this study was to determine the compound strength of the fixation between 2 blocks of synthetic bone using ultrasound activated resorbable pins (regarding drill hole diameter) and compare them to fixation with titanium miniscrews. Resorbable pins were up to 17 mm long. STUDY DESIGN Two synthetic bone blocks (Sawbone) were fixed by either a resorbable pin or miniscrew osteosynthesis. Maximum tensile forces were determined mechanically. Pin lengths of 7 mm, 11 mm, and 17 mm were analyzed in relation to different drill hole diameters. RESULTS The ideal drill hole configuration was a combination of diameters of 2.1/1.6 mm (in a lag screw configuration). Mean maximum tensile force was 80 N for 7 mm pins (105 N/11 mm, 69 N/17 mm). In comparison, tensile forces of titanium screws were 20 N (7 mm), 97 N (11 mm), and 135 N (17 mm). CONCLUSIONS Osteosynthesis by resorbable pins reached equal compound strength levels compared with titanium miniscrews. This in vitro study was the basis for a clinical trial of ultrasound-guided resorbable pin osteosynthesis.

Isolation and identification of chitin from heavy mineralized skeleton of Suberea clavata (Verongida: Demospongiae: Porifera) marine demosponge

Since the discovery of chitin in skeletal structures of sponges (Porifera) in 2007, studies on search of novel species which possess this structural aminopolysaccharide continue up today. The most potential source of chitin is suggested to be localized in the four families of sponges related to the order Verongida (Demospongiae) which nevertheless require further clarification. Here, we report for the first time the isolation and identification of α-chitin from the Suberea clavata demosponge (Aplysinidae: Verongida). Raman spectroscopy, Calcofluor White staining, chitinase test and ESI-MS techniques were used to identify chitin. We suggest that the presence of chitin within fibrous skeletons of diverse species of Verongida order, and, especially in all species of the Aplysinidae family, may be useful for the identification of novel, previously unidentified marine demosponges.

New Concept of Polymethyl Methacrylate (PMMA) and Polyethylene Terephthalate (PET) Surface Coating by Chitosan

Chitosan is known for its hemostatic and antimicrobial properties and might be useful for temporary coating of removable dentures or intraoral splints to control bleeding after oral surgery or as a supportive treatment in denture stomatitis. This study investigated a new method to adhere chitosan to polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET). There were 70 cylindrical specimens made from PMMA and 70 from PET (13 mm diameter, 6 mm thickness). The materials with ten specimens each were sandblasted at 2.8 or 4.0 bar with aluminum oxide 110 μm or/and aluminum oxide coated with silica. After sandblasting, all specimens were coated with a 2% or 4% acetic chitosan solution with a thickness of 1 mm. Then the specimens were dried for 120 min at 45 °C. The precipitated chitosan was neutralized with 1 mol NaOH. After neutralization, all specimens underwent abrasion tests using the tooth-brushing simulator with soft brushes (load 2N, 2 cycles/s, 32 °C, 3000 and 30,000 cycles). After each run, the specimen surfaces were analyzed for areas of remaining chitosan by digital planimetry under a light microscope. The best chitosan adhesion was found after sandblasting with aluminum oxide coated with silica (U-Test, p < 0.05) in both the PMMA and the PET groups. Hence, with relatively simple technology, a reliable bond of chitosan to PMMA and PET could be achieved.

First Report on Chitin in a Non-Verongiid Marine Demosponge: The Mycale euplectellioides Case

Sponges (Porifera) are recognized as aquatic multicellular organisms which developed an effective biochemical pathway over millions of years of evolution to produce both biologically active secondary metabolites and biopolymer-based skeletal structures. Among marine demosponges, only representatives of the Verongiida order are known to synthetize biologically active substances as well as skeletons made of structural polysaccharide chitin. The unique three-dimensional (3D) architecture of such chitinous skeletons opens the widow for their recent applications as adsorbents, as well as scaffolds for tissue engineering and biomimetics. This study has the ambitious goal of monitoring other orders beyond Verongiida demosponges and finding alternative sources of naturally prestructured chitinous scaffolds; especially in those demosponge species which can be cultivated at large scales using marine farming conditions. Special attention has been paid to the demosponge Mycale euplectellioides (Heteroscleromorpha: Poecilosclerida: Mycalidae) collected in the Red Sea. For the first time, we present here a detailed study of the isolation of chitin from the skeleton of this sponge, as well as its identification using diverse bioanalytical tools. Calcofluor white staining, Fourier-transform Infrared Spcetcroscopy (FTIR), electrospray ionization mass spectrometry (ESI-MS), scanning electron microscopy (SEM), and fluorescence microscopy, as well as a chitinase digestion assay were applied in order to confirm with strong evidence the finding of a-chitin in the skeleton of M. euplectellioides. We suggest that the discovery of chitin within representatives of the Mycale genus is a promising step in their evaluation of these globally distributed sponges as new renewable sources for both biologically active metabolites and chitin, which are of prospective use for pharmacology and biomaterials oriented biomedicine, respectively.

Creation and utilization of a digital database for nasal prosthesis models.

Background: The study describes the development and implementation of a digital nose database in order to provide patients with nasal prostheses following rhinectomy. Mirrored data for computer-aided design (CAD) cannot be used due to the unpaired structure of the nose. Materials and Methods: The faces of 202 people were digitized using a 3-dimension (3D) scanner. The noses were scaled, measured and classified according to objective criteria. The physician, the patient and the anaplastologist can collaborate in order to select an appropriate nose from the multitude of existing nose types and sizes. Virtual ‘fittings’ and an individual adaptation of the nose are feasible. For this purpose the epiTecture software was applied. The selected nose is then created on a 3D printer as a thermopolymer model. This model can be fitted and corrected as a physical model on the patient. The remaining steps are identical to conventional prosthesis production. Results: A digital nose database was developed at the University Hospital Dresden with the help of the epiTecture software. Instructions for usage are illustrated using the example of a patient. Conclusions: The process of providing nasal prostheses described in this paper is different from conventional processes. This is primarily due to the elimination of physical modeling, causing substantially less strain for the patient.

The demosponge Pseudoceratina purpurea as a new source of fibrous chitin

Among marine demosponges (Porifera: Demospongiae), only representatives of the order Verongiida have been recognized to synthetize both biologically active substances as well as scaffolds-like fibrous skeletons made of structural aminopolysaccharide chitin. The unique 3D architecture of such scaffolds open perspectives for their applications in waste treatment, biomimetics and tissue engineering. Here, we focus special attention to the demosponge Pseudoceratina purpurea collected in the coastal waters of Singapore. For the first time the detailed description of the isolation of chitin from the skeleton of this sponge and its identification using diverse bioanalytical tools were carried out. Calcofluor white staining, FTIR analysis, electrospray ionization mass spectrometry (ESI-MS), SEM, and fluorescence microscopy as well as a chitinase digestion assay were applied in order to confirm with strong evidence the finding of alpha-chitin in the skeleton of P. purpurea. We suggest that the discovery of chitin within representatives of Pseudoceratinidae family is a perspective step in evaluation of these verongiid sponges as novel renewable sources for both chitin and biologically active metabolites, which are of prospective use for marine oriented biomedicine and pharmacology, respectively.