Metal-dielectric nanostructures for on-chip Surface Enhanced Raman Scattering based biomolecular detection

Chiara NOVARA, Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino

The exploitation in nanomedicine of emerging, ultrasensitive, label free diagnostic techniques, such as Surface Enhanced Raman Scattering (SERS), requires the development of suitable platforms, in terms of high sensitivity and repeatability, together with the possibility of miniaturization for point-of-care applications and full compatibility to biological protocols. Recently, metal-dielectric nanostructures based on silver nanoparticles synthesized on polymers or semiconductors have been studied as SERS active substrates for biodetection. The deposition of silver by sputtering or immersion plating on TiO2 nanotubes, polydimethylsiloxane, porous silicon and monolayer graphene has been optimized, allowing to approach the single molecule detection regime. Each substrate confers peculiar advantages, such as electromagnetic and chemical enhancement, tunability of the plasmonic resonances, and/or high surface area. Strategies for the integration of the above discussed metal-dielectric SERS substrates in microfluidic chips are presented, enabling in some cases all-microfluidic processes, from the synthesis of the nanoparticles to the bioanalyte detection. In particular, the nanostructures are tested for their compatibility to a tailored bioassay for the profiling of microRNA biomarkers, whose over- or under-expression is a hallmark of cancer diseases. The detection of miRNA222 is proved in real cell extracts demonstrating the potential of the SERS-based chips in early cancer diagnosis.

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