Diatom biosilica in plasmonics: Applications in biosensing and biomedicine.

Diatom microalgae are characterized by nano-structured silica shells, whose optical properties can be exploited in biophotonics and biomedical applications. Metallization of diatom biosilica, both in the shape of intact frustules or diatomite particles (DNPs), can trigger plasmonic effects that in turn can find application in highly sensitive SERS (surface-enhanced Raman scattering) detection platforms, allowing to obtain effective nanosensors at low cost and on a large scale. In this contribution, diatom-based plasmonic devices are developed for SERS imaging of cell membrane components with several exciting prospects including sub-diffraction resolution and single molecule sensitivity which would aid studies of trans-membrane transport dynamics. A hybrid nanoplatform of DNPs decorated by gold nanoparticles and capped by a layer of gelatin was developed for monitoring the drug release in colorectal cancer cells at a femtogram scale by SERS. The combination of the drug-loading capacity of DNPs with the strong Raman enhancement enabled combining therapeutic purposes with label-free intracellular drug monitoring.