Chitosan-modified silver@ruthenium hybrid nanoparticles: evaluation of physico-chemical properties and bio-affinity with sialic acid.

Hybrid nanoparticles (NPs) integrated with dye molecules have attracted interest for biomolecular detection, due to their effortless fabrication, timely operation, controllable specific recognition and low-cost. In this study, hybrid core-shell NPs made of a metal-dye complex (AgNPs@[Ru(bpy)3]2+) core and a chitosan (CS) shell exhibiting a selective fluorescence quenching effect were successfully prepared using a cost-effective wet-chemical approach. The physico-chemical properties of NPs were determined by spectroscopy and light scattering measurements. The bio-affinity of the AgNPs@[Ru(bpy)3]2+/CS was evaluated in aqueous media using sialic acid (SA) as the target molecule in the presence of different monosaccharides and anionic biomolecules as interferents. A significant fluorescence quenching of hybrid NPs was observed in aqueous solutions of SA with interferents, while no significant quenching effect was detected in SA-free interferent solutions. The selective binding of SA to the particles resulted from favorable electrostatic interactions and inter-molecular hydrogen bonding with the functional groups of CS. The hybrid NP system displayed a good sensitivity for SA with a detection limit of 5.1 nM and a concentration dependent fluorescence quenching for SA concentrations ranging from 25 nM to 3.2 μM. This hybrid NP system represents a promising alternative probe for detecting sialic acid in complex samples.