Design of a 3D interfacial SERS liquid sensing platform based on Au-nanobones for discrimination and quantitation of quercetin loaded nanoemulsions

Characterization, and discrimination between free quercetin and quercetin-loaded nanoemulsions (Q-NEs) are described, as well as the design of a plasmonic metal liquid platform for their quantitation. First, reproducible Q-NEs synthesis using GRAS (Generally Recognized as Safe) components and a low-energy method as phase inversion temperature was used. Q-NEs were fully characterized being the resulting droplet size of 73.1 ± 2.4 nm and 69.7 ± 2.3 nm by DLS and SEM, respectively, with spherical morphology and encapsulation efficiency of 96.5%. Based on UV-Vis, Raman and SERS characterization studies, a discrimination between free quercetin and Q-NEs was achieved. Secondly, a new 3D-platform was developed based on tuned gold nanorods-bone shaped with fitted aspect ratios for Q-NEs quantification without altering its native nanostructure using the enhanced stretching at 1600 cm -1 as analytical signal. The developed plasmonic sensing platform allows to reach intensification factors up to 10 3 and 10 5 for the target analyte and methylene blue as Raman reporter, respectively. It was also submitted to an exhaustive evaluation of analytical performance characteristics in terms of linear dynamic range (0.5 – 30 µM), detection limit (0.2 µM) with good precision (RSD = 2.6%). The nanometrological 3D SERS approach was reliably implemented and validated on commercial nutritional supplements containing declared encapsulated quercetin as nanosized formulations by means of a statistical comparison with those ones obtained by a µHPLC-DAD method.