Neutral Dye-Doped Silica Nanoparticles for Electrogenerated Chemiluminescence Signal Amplification

Immunoassay is probably the primary in vitro technique employed in medical diagnostics. Its different setups include often the well-known and sensitive analytical method based on electrochemiluminescence (ECL), and approaches relying on nanotechnology have the potentiality to further enhance ECL signal response and detection capability. With this intent, we studied the ECL behavior of dye-doped silica–poly­(ethylene glycol) core–shell nanoparticles (DDSNPs) doped with neutral Ru­(II) complexes in a very large doping range. We found that nanoparticles maintain comparable morphology and dimensions as the amount of Ru­(II) neutral complexes that are covalently linked to their silica matrix increases; meanwhile, ECL shows an enhanced response. The 9-fold ECL signal amplification obtained when compared with [Ru­(bpy)3]2+-doped silica nanoparticles is due to the synergy between the behavior of neutral Ru­(II) complex and the DDSNP architecture: these results pave the way for the development of more efficient probes in ECL technology.