High Levels of Residue within Polymeric Hollow Fiber Membranes Used for Blood Oxygenation.

A number of research teams are developing surface coatings for hollow fiber membrane (HFM) blood oxygenators to improve their biocompatibility and service life. Surface coating techniques can be quite sensitive to the presence of contaminants on the exterior surface of the hollow fibers. We found large amounts of leachable oils associated with several commercial HFMs, i.e., as much as 2.5-7.5 weight percent. Leachable residues were suspected when a surface coating, a surface-initiated atom transfer radical polymerization (s-ATRP) of poly(ethylene glycol) methacrylate, resulted in areas of 100 µm devoid of coatings on the exterior surfaces of HFMs. After leaching residual oils, s-ATRP coatings were uniform and continuous across the hollow fibers. Therefore, removal of residual material should be considered before applying coating technologies to commercial HFMs. The effects of such leachable agents on the performance of blood oxygenators are not known.

Interactions between SIRT1 and AP-1 reveal a mechanistic insight into the growth promoting properties of alumina (Al2O3) nanoparticles in mouse skin epithelial cells.

The physicochemical properties of nanomaterials differ from those of the bulk material of the same composition. However, little is known about the underlying effects of these particles in carcinogenesis. The purpose of this study was to determine the mechanisms involved in the carcinogenic properties of nanoparticles using aluminum oxide (Al(2)O(3)/alumina) nanoparticles as the prototype. Well-established mouse epithelial JB6 cells, sensitive to neoplastic transformation, were used as the experimental model. We demonstrate that alumina was internalized and maintained its physicochemical composition inside the cells. Alumina increased cell proliferation (53%), proliferating cell nuclear antigen (PCNA) levels, cell viability and growth in soft agar. The level of manganese superoxide dismutase, a key mitochondrial antioxidant enzyme, was elevated, suggesting a redox signaling event. In addition, the levels of reactive oxygen species and the activities of the redox sensitive transcription factor activator protein-1 (AP-1) and a longevity-related protein, sirtuin 1 (SIRT1), were increased. SIRT1 knockdown reduces DNA synthesis, cell viability, PCNA levels, AP-1 transcriptional activity and protein levels of its targets, JunD, c-Jun and BcL-xl, more than controls do. Immunoprecipitation studies revealed that SIRT1 interacts with the AP-1 components c-Jun and JunD but not with c-Fos. The results identify SIRT1 as an AP-1 modulator and suggest a novel mechanism by which alumina nanoparticles may function as a potential carcinogen.