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Gaelle Piret, Christelle Prinz, Maria-Thereza Perez; Retinal Cells Cultured on Silicon Nanowires. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4615.
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© ARVO (1962-2015); The Authors (2016-present)
Porous silicon has potential applications in the treatment of retinal diseases as it may be used in the production of prosthetic devices as well as for slow drug delivery. The purpose of the study was to investigate the short- and long-term survival of postnatal retinal cells grown on silicon nanowires (SiNW).
Control substrates consisted of flat silicon (Si). SiNW arrays were prepared by chemical etching of crystalline silicon in hydrofluoric acid/silver nitrate aqueous solution. As a function of etching time, nanowires of different length (800 nm, 1.8 µm, 4.4 µm) were produced. The arrays were washed by various methods before seeding the cells. Primary cell cultures were prepared from postnatal day 4 mouse retinas. Cells were cultured for 3 and 18 days in vitro (DIV) on SiNW and Si, and analyzed by scanning electron microscopy (SEM) and immunohistochemistry using antibodies recognizing retinal cell-specific proteins.
On Si control substrates, single cells and cell clusters were observed at 3 and 18DIV, with indications that a few cells detached over time. All retinal markers tested were detected among cultured cells at both time points. With some of the markers tested (β-tubulin III, rhodopsin, cone arrestin, recoverin, TRPV4, Brn3a), it was also possible to distinguish labelled processes. In SiNW, a single layer of cells was observed already at 3DIV covering most of the substrate surface, with no obvious signs of cell loss. Although all cell markers tested were detected also in cells cultured onto SiNW, their level of expression was lower, except that of rhodopsin. Further, labelled cell processes could, in most cases, not be found.
Retinal cells survive on both flat silicon and SiNW for at least 18DIV. However, despite good adhesion and long-term survival onto SiNW, the cells undergo phenotypic changes that suggest that on this substrate, culture conditions are suboptimal. This may be due to the presence of chemical residues derived from the nanowire fabrication and/or from the degradation of the silicon nanowires. These observations indicate that the therapeutic use of the SiNW tested in the present study may be limited, unless the nanowires are coated with thin films of other materials or are chemically functionalized in order to limit or prevent degradation and release of contaminants. It is, nevertheless, intriguing that rod photoreceptors appeared to be more resilient than the other retinal cell types.
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