Effect of oligoethylene glycol moieties in porous silicon surface functionalisation on protein adsorption and cell attachment

We report on the synthesis of two carboxy-functional alkene compounds as modifiers of porous silicon (pSi) surface chemistry by means of thermal hydrosilylation. Both alkene compounds have hydrophobic, aliphatic carbon segments, with terminal carboxylic acid functionality appended through a thioether linkage. In one of the alkene linkers, we incorporated a short oligoethylene glycol (OEG) moiety to explore its low-fouling properties when attached to porous silicon. We examined surface stability of the surface-modified porous silicon in aqueous milieu. Albumin and fibronectin were adsorbed and, using carbodiimide chemistry, covalently immobilised to linker-modified porous silicon, and the propensity for mammalian cells to attach to these surfaces investigated. Surface chemistry was characterised by infrared spectroscopy and the stability of porous silicon in an aqueous milieu was investigated by interferometric reflectance spectroscopy (IRS). Surfaces functionalised with the alkene linker containing OEG displayed greater resistance to the adsorption of albumin. This linker also facilitated higher levels of covalent protein immobilisation to the functionalised pSi surface. Higher levels of cell attachment were observed on pSi surfaces with fibronectin covalently immobilised onto the OEG linker, than for fibronectin covalently immobilised on the non-OEG linker.