Epithelial cell behavior on alpha-particle irradiated and chemically etched polyallyldiglycol carbonate film surfaces

Abstract

A simple and convenient method was proposed to introduce micrometer-size pits on the surface of a polymer (polyallyldiglycol carbonate or PADC) by alpha-particle irradiation and subsequent chemical etching. The pits were blind-ended so they were useful for studying the topographical effects alone on cell behavior. Alpha-particle radiobiological experiments involve irradiating cells with alpha particles and require thin biocompatible materials as substrates for cell cultures, which can record alpha-particle transversals. The commercially available CR-39 solid-state nuclear track detectors (SSNTDs), which are based on PADC, with a thickness of about 20 μm are suitable substrates. In the present work, the biocompatibility enhancement of these thin etched CR-39 SSNTDs is studied through superficial pore formation by alpha-particle irradiation for 3 h. HeLa cells were cultured on these detectors and the biocompatibility was assessed through the number, morphology and average cell area of the cultured cells. For short etching time (15 min) in NaOH/H2O (with subsequent etching in NaOH/ethanol), the biocompatibility of the CR-39 detector is enhanced through superficial pore formation by alpha-particle irradiation. In contrast, for long etching time (60 min) in NaOH/H2O (with subsequent etching in NaOH/ethanol), the biocompatibility of the CR-39 detector deteriorates through superficial pore formation. Possible reasons are discussed. On the other hand, vinculin, the cell adhesion and membrane protrusion protein, was used as an indicator of cytoskeletonal reorganization on substrates, and localization of vinculin was used to demonstrate the presence of focal adhesions. In our experiments, vinculin expressed in epithelial HeLa cells cultured on 3 h etched PADC films with 3 and 6 h alpha-particle irradiated track-etch pits, but not in cells cultured on the raw or chemically etched blank films. In other words, vinculin expression was induced by the topography of track-etch pits, while etching of the substrate alone (without alpha-particle irradiation) did not cause up-regulation of vinculin protein expression. Comparing with the raw films, HeLa cells cultured on PADC films with track-etch pits also showed a reduction of cell proliferation, cell area, and were largely contained by the track-etch pits. In other words, the cell membrane edges tended to be in contact with the pits. By comparing the correlation between the positions of HeLa cells and the pits, and that between the positions of cells and computer-simulated pits, the tendency for membrane edges of HeLa cells to be in contact with the pits was recognized. This could be explained by inhibition of membrane protrusion at the pits. In conclusion, substrate track-etch pits were an important determinant of epithelial cell behavior.

Date of Award	15 Jul 2008
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Tsang CHEUNG (Supervisor)