Determining Protein Size Using an Electrochemically Machined Pore Gradient in Silicon

Abstract

Porous silicon films displaying a distribution of pore dimensions can be generated by electrochemically etching silicon in aqueous ethanolic HF using an asymmetric electrode configuration. The median pore size and breadth of the size‐distribution in the film can be set by adjusting the HF concentration, current density, and position of the counter electrode relative to the silicon electrode. Films with pore sizes in the range of a few nanometers are used as size‐exclusion matrices to perform an on‐chip determination of macromolecule dimensions. The test molecule used in this study is bovine serum albumin (BSA). Optical reflectivity spectra of the thin porous Si films display distinctive shifts in the Fabry–Perot fringes in regions of the film where the pore dimensions are larger than a critical size, interpreted to be the characteristic dimensions of the protein. Gating of the protein in and out of the porous films is demonstrated by adjustment of the solution pH below and above the pI (isoelectric point) value, respectively.

Control over wettability via surface modification of porous gradients

“…A surface topography within the nanometer range may not exert sufficient physicochemical effects on wettability. The physical appearances of the laterally etched pSi surface that we obtained were found to be similar to those previously attained by Sailors group [25]. For all currents used in this work we were able to avoid electropolishing the surface.…”

“…The possibility to fabricate pSi surfaces containing a distribution of pore sizes by anodisation in an asymmetrical arrangement has been described previously [25]. The current within the electrolytic solution varies as a function of distance of the electrode to the counter electrode due to resistance of the electrolyte, thus leading to a decrease in current density as the distance from the electrode increases [25,26]. This dependence can be exploited to generate a surface displaying a gradient of pore features ranging from large (1-3 µm) to small (5 nm) on a single surface [27].…”

Preparation of two-directional gradient surfaces for the analysis of cell-surface interactions

“…This confirms the current density chosen for the anodisation of the gradient is optimal and suggests that any further increase in current density will result in the collapse of the pore structure. Furthermore, the distribution in structural colour and visual characteristics were similar in comparison to previously published lateral gradients reported by Sailor et al 24 and Khung et al 4 .…”

“…The non-linear nature of the gradient could be attributed to the non-linear decrease in current density across the substrate. Previous studies have observed similar results 24,25 . Several HF/ethanol ratios were also investigated and it was found that increasing the concentration of HF led to a steeper decline in the pore size along the gradient.…”

Contribución al estudio del comportamiento de silicio poroso nano-estructurado en fluidos corporales simulados para el desarrollo de nuevos materiales biocompatibles y biodegradables.

“…En este sentido en el silicio poroso se han efectuado gran cantidad de estudios, existen publicaciones referentes a la calcificación [2][3][4][5][6][7][8][9][13][14][15][16][17], adhesión y cultivo de células [18][19][20][21], redes neuronales [22], adsorción de proteínas [23][24][25][26] y estudios de biodegradabilidad [27][28][29][30][31], así como de biocompatibilidad in Vivo [32,33]. Además se han hecho estudios sobre problemas que pueden plantearse a la hora de utilizarlo en seres humanos, como por ejemplo, la esterilización en autoclave [34] y otras técnicas de esterilizado [35], o sobre técnicas de fabricación con el objeto de que no sea perjudicial para la salud [36].…”