Mesoporous silicon photonic crystal microparticles: Towards single-cell optical biosensors

In this paper we demonstrate the possibility of modifying porous silicon (PSi) particles with surface chemistry and recognition molecules (antibodies) such that these devices could potentially be used for single-cell identification or sensing. This is achieved by modifying PSi Rugate filters via hydrosilylation with surface chemistry that serves firstly, to protect the silicon surfaces from oxidation; secondly, renders the surfaces resistant to nonspecific adsorption of proteins and cells and thirdly, allows further functionality to be added such as the coupling of antibodies. The surface chemistry remained unchanged after sonication of the PSi to form PSi microparticles. The ability to monitor the spectroscopic properties of microparticles, and shifts in the optical signature due to changes in the refractive index of the material within the pore space, is demonstrated. The particles are shown to remain stable in physiological buffers and human blood for longer than one week. Finally, the modification of the PSi particles with functional antibodies is achieved.