Silica Coated Plasmonic Nanobone-based Tags for Safe Bioimaging

Abstract

Fluorescence tomography is a hopeful medical imaging technique. However, this method has restrictions consisting in absorbance and scattering of optical signal by tissue. The present research is devoted to overcome these challenges utilising plasmonic nanoparticles. A new type of gold nanoparticles was synthesized, having a bone-like shape which provides the maximum of unimodal absorption band just in the middle of the biological tissues transparency range (600-800 nm). The nanobones were further modified with cyanine 5.5 and 7 fluorophores by electrostatic immobilization and coated by silica shell via two different techniques to instill biocompatibility. Resulting nanoparticles were characterised by dynamic light scattering, transmission electron microscopy, fluorescent and Raman spectroscopy. It is shown that a thickness of silica shell may be tuned precisely and that the nanoparticles may also be coated directly using mercaptopropyltrimethxysilane. The registered surface-enhanced Raman scattering and fluorescent signals depend on a position of cyanine dye in nanoparticle shell. Intensive fluorescent signal from the nanoparticles covered with silicon dioxide using mercaptopropyltrimethxysilane proved an incorporation of cyanines into shell during its growth.