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Electrodes implanted in the brain or spinal cord trigger the activation of resident astrocytes. In their reactive state, astrocytes surrounding the electrode form a glial scar, compromising the ability of the electrode to interface with the surrounding neural tissue. One approach to reduce the inhibiting scar tissue is to incorporate nanoarchitecture on the surface of the implanted materials to modify the astrocytic response. The incorporated nanoarchitecture changes both the surface characteristics and the material properties of the implant interface. We investigated the response of rat cortical astrocytes to nanoporous anodic aluminum oxide (AAO) surfaces. Astrocytes were seeded onto nonporous aluminum control surfaces and AAO surfaces with average nanopore diameters of 20 and 90 nm. The surfaces were characterized by assessing their nanomorphology, hydrophobicity, surface chemistry, mechanical properties, and surface roughness. For cell response characterization, calcein-based viability and adhesion studies were performed. Plasmid-assisted vinculin live cell imaging was done to characterize focal adhesion number and distribution. Immunocytochemistry was used to assess glial fibrillary acidic protein (GFAP) expression. We found that astrocyte adhesion was significantly higher on small pore surfaces compared to large pore surfaces. Astrocytes produced more focal adhesions (FA) and distributed these FA peripherally when cultured on small pore samples compared to the other groups. Astrocyte GFAP expression was lower when astrocytes were cultured on surfaces with small nanopores compared to the control and large pore surfaces. These results indicate that unique surface nanoporosities influence astrocyte adhesion and subsequent cellular response. The reduction in GFAP immunoreactivity exhibited by the smaller pore surfaces can improve the long-term performance of the implanted neurodevices, thus making them credible candidates as a coating material for neural implants.

The aim of this study was to determine the thickest slice at the lowest radiation dose for detection of colon polyps larger than 5mm in diameter at computed tomographic (CT) colonography. A colon phantom containing haustral folds, flexures, and straight segments was constructed of borosilicate. One hundred forty simulated polyps (5, 7, 10, and 12 mm) of various shapes (sessile, flat, and pedunculated) were attached at different colon locations (wall, base of fold, on the fold and fold tip). Polyps were positioned parallel, perpendicular, and oblique to the CT gantry. The air-filled phantom was scanned at different slice thicknesses (1.25–5 mm) and x-ray tube currents (5–308 mA). All polyps were identified in all data sets except one (1.25 mm slice thickness, 5 mA). In this acquisition, image noise reduced polyp visibility, and five of 140 (3%) polyps could not be identified. Unidentified polyps were 5 mm, flat or sessile in shape, located on the colon wall or base of the fold, and oblique or parallel to CT gantry. All tested CT techniques provided optimal polyp detection except settings at 1.25 mm and 5 mAs. Thin collimation (< 5 mm) scans may not be necessary to detect clinically significant polyps.