Morphological and functional analysis of rat hepatocyte spheroids generated on poly(L-lactic acid) polymer in a pulsatile flow bioreactor.

Liver neo-tissue suitable for transplantation has not been established. Primary rat hepatocytes were cultured on three-dimensional biodegradable polymer matrices in a pulsatile flow bioreactor with the intention of inducing tissue formation and improving cell survival. Functional and structural analysis of the hepatocytes forming liver neo-tissue was performed. Biodegradable poly(L-lactic acid) (PLLA) polymer discs were seeded with 4 x 10(6) primary rat hepatocytes each, were exposed to a pulsatile medium flow of 24 mL/min for 1, 2, 4, or 6 days and were investigated for monoethylglycinexylidine (MEGX) formation, ammonia detoxification, Cytokeratin 18 (CK18) expression, and preserved glycogen storage. Fine structural details were obtained using scanning and transmission electron microscopy. Spheroids of viable hepatocytes were formed. MEGX-specific production was maintained and ammonia removal capacity remained high during the entire flow-culture period of 6 days. CK18 distribution was normal. Periodic-acid- Schiff reaction demonstrated homogenous glycogen storage. The hepatocytes reassembled to form intercellular junctions and bile canaliculi. Functional and morphological analysis of rat hepatocytes forming spheroids in a pulsatile flow bioreactor indicated preserved and intact hepatocyte morphology and specific function. Pulsatile flow culture on PLLA scaffolds is a promising new method of hepatic tissue engineering leading to liver neo-tissue formation.

Biliary stent clogging solved by nanotechnology? In vitro study of inorganic-organic sol-gel coatings for teflon stents.

BACKGROUND & AIMS: The major drawback of plastic stents for biliary drainage is the occlusion by sludge. Sludge is accrued because the stent surface allows for the adherence of proteins, glycoproteins, or bacteria and the bile flow is insufficient to clean the surface. In this study, experience from nanotechnology to achieve a clean surface by improved soil-release characteristics is used to optimize biliary stent surface. The aim of this study was to examine sludge accumulation in relation to surface characteristics designed by nanotechnology. METHODS: A variety of inorganic-organic sol-gel-coated stents were incubated in sterilized human bile and enzyme-active Escherichia coli for 35 days. Materials were Teflon (DuPont, Wilmington, DE) coated with hydrophobic Clearcoat (NTC, Tholey, Germany), Teflon with sol-gel coating synthesized of organic epoxides of 190 g/mol or 500 g/mol, and propylaminosilane without or with fluorsilanes for increased hydrophobicity. Scanning electron microscopy and semiquantitative analysis, blinded to the type of coating, were used to determine the amount of sludge accumulated on the surface. RESULTS: Sludge deposition was reduced on the designed surfaces as compared with uncoated Teflon and Clearcoat. The performance of high molecular (500 g/mol) was superior to that of low molecular (190 g/mol) epoxide ligand. However, increasing hydrophobicity by adding fluoraminosilanes resulted in increased adherence of sludge. Less than a micrometer-thin sol-gel coating is inexpensive because very little coating material is required. This is the first published data comparing systematically modified surfaces of biliary stents using nanotechnology. CONCLUSIONS: Optimized soil release by sol-gel nanocoating of plastic stents may prevent biliary plastic stents from clogging.