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1 februari 2010, Contains fulltext : 88467.pdf (Publisher’s version ) (Closed access), Glucuronic acid (GlcA) and phosphoserine (pS) carrying acidic functional groups were used as model molecules for glycosaminoglycans and phosphoproteins, respectively to mimic effects of native biomolecules and influence the mineralization behaviour of collagen I. Collagen substrates modified with GlcA showed a stable interaction between GlcA and collagen fibrils. Substrates were mineralized using the electrochemically assisted deposition (ECAD) in a Ca(2+)/H( x )PO (4) ((3-x)) electrolyte at physiological pH and temperature. During mineralization of collagen-GlcA matrices, crystalline hydroxyapatite (HA) formed earlier with increasing GlcA content of the collagen matrix, while the addition of pS to the electrolyte succeeded in inhibiting the transformation of preformed amorphous calcium phosphate (ACP) to HA. The lower density of the resulting mineralization and the coalesced aggregates formed at a certain pS concentration suggest an interaction between calcium and the phosphate groups of pS involving the formation of complexes. Combining GlcA-modified collagen and pS-modified electrolyte showed dose-dependent cooperative effects.

The Porifera (sponges) are often regarded as the oldest, extant metazoan phylum, also bearing the ancestral stage for most features occurring in higher animals. The absence of chitin in sponges, except for the wall of peculiar resistance bodies produced by a highly derived fresh-water group, is puzzling, since it points out chitin to be an autapomorphy for a particular sponge family rather than the ancestral condition within the metazoan lineage. By investigating the internal proteinaceous (spongin) skeleton of two demosponges (Aplysina sp. and Verongula gigantea) using a wide array of techniques (Fourier transform infrared (FTIR), Raman, X-ray, Calcofluor White Staining, Immunolabeling, and chitinase test), we show that chitin is a component of the outermost layer (cuticle) of the skeletal fibers of these demosponges. FTIR and Raman spectra, as well as X-ray difractograms consistently revealed that sponge chitin is much closer to the a-chitin known from other animals than to b-chitin. These findings support the view that the occurrence of a chitinproducing system is the ancestral condition in Metazoa, and that the a-chitin is the primitive form in animals.

Contains fulltext : 49055.pdf (publisher's version ) (Closed access), In this work the osteoconductive potential of coatings for titanium implants using different extracellular matrix components was evaluated. Cylindrical implants with two defined cavities A and B were coated with collagen type I, type III, or RGD peptide, and placed in the femur of goats together with an uncoated reference state. Bone contact and volume were determined after 5 and 12 weeks implantation, using both histomorphometry and synchrotron radiation micro computed tomography (SR muCT) as the methods complement each other: SR muCT allows for a high precision of bone detection due to the large number of analysed slices per sample, while histology offers a better lateral resolution and the possibility of additionally determining bone contact. Both methods revealed similar tendencies in bone formation for the differently bio-functionalized implants, with the SR muCT data resulting in significant differences. After 5 and 12 weeks, all three coatings showed a significant increase in bone volume over the uncoated reference, with the highest results for the collagen coatings. The coating consisting of just the RGD-sequence to improve cell adhesion showed only a slight improvement compared with the reference material. For uncoated titanium, RGD, and especially collagen type I, the response in cavity A, situated in denser bone, was stronger than in cavity B. Collagen type III, on the other hand, appeared to be the more effective coating in areas of lesser bone density as represented by cavity B. These results indicate that matrix molecules (or combinations thereof) are capable of generating the appropriate signals for the specific microenvironment around implants and can thus accelerate the bone formation process and increase the stability of implants.