Fabrication of scalable and structured tissue engineering scaffolds using water dissolvable sacrificial 3D printed moulds

One of the major challenges in producing large scale engineered tissue is the lack of ability to create large highly perfused scaffolds in which cells can grow at a high cell density and viability. Here, we explore 3D printed polyvinyl alcohol (PVA) as a sacrificial mould in a polymer casting process. The PVA mould network defines the channels and is dissolved after curing the polymer casted around it. The printing parameters determined the PVA filament density in the sacrificial structure and this density resulted in different stiffness of the corresponding elastomer replica. It was possible to achieve 80% porosity corresponding to about 150 cm2/cm3 surface to volume ratio. The process is easily scalable as demonstrated by fabricating a 75 cm3 scaffold with about 16,000 interconnected channels (about 1 m2 surface area) and with a channel to channel distance of only 78 μm. To our knowledge this is the largest scaffold ever to be produced with such small feature sizes and with so many structuredchannels. The fabricated scaffoldswere applied for in-vitro culturing of hepatocytes over a 12-day culture period. Smaller scaffolds (6× 4mm) were tested for cell culturing and could support homogeneous cell growth throughoutthe scaffold. Presumably, the diffusion of oxygen and nutrient throughout the channel network is rapid enough to support cell growth. In conclusion, the described process is scalable, compatible with cell culture, rapid, and inexpensive

Design, Synthesis and Biological testing of Novel ligands for Ghrelin Receptor

Abstract G-protein coupled receptors (GPCRs) are having the high medical importance since almost half of the medicinal drugs are designed as modulators of receptor molecules. Crystal structure or NMR structures of GPCRs are very difficult to determine because all GPCRs are typically bound to the cell membrane and thus their molecular activation mechanism is still unclear. The recent publication of the crystal structure of the 2-adrenoreceptor will provide new insights in the field of GPCR research. Ghrelin is a peptide growth hormone which binds to the growth hormone secretagogue receptor (GHS-R) and stimulates the release of growth hormone. Based on the known ghrelin receptor binding core sequences wFwLL (upper letter and lower letter representative for L-form and D-form of the amino acids respectively), we prepared two novel peptide analogs with terminal S-(2-aminoethylsulfenyl) cysteine residues. These peptides were tested for their ability to suppress the binding of ghrelin to transfected COS7 cell-line (Kidney fibroblast line from the green African monkey) cells expressing the ghrelin wild-type receptor or certain mutants thereof. As a result we observed a significant reduction of the total number of binding sites accessible for ghrelin, which increased with the time the cells were incubated with our test compounds. This observations support our hypothesis that the peptides we tested form a covalent bond with free thiols located closely to the ligand binding-site of the receptor protein by disulfide thiol exchange which is an interesting target for development of anti-obesity drugs