Signal-On Fluorescent Imprinted Nanoparticles for Sensing of Phenols in Aqueous Olive Leaves Extracts

Abstract

The activation of signals in fluorescent nanosensors upon interaction with their targets is highly desirable. To this aim, several molecularly imprinted nanogels have been synthetized for the recognition of tyrosol, hydroxytyrosol and oleuropein in aqueous extracts using the non-covalent approach. Two of them contain fluorescein derivatives as co-monomers, and their fluorescence emission is switched on upon binding of the target phenols. The selection of functional monomers was previously done by analyzing the interactions by nuclear magnetic resonance (NMR) in deuterated dimethylsulfoxide (DMSO-d6) of the monomers with tyrosol and hydroxytyrosol. Polymers were synthetized under high dilution conditions to obtain micro- and nano-particles, as verified by transmission electron microscopy (TEM). 1,4-Divinylbenzene (DVB) was used in the fluorescent polymers in order to enhance the interactions with the aromatic ring of the templates tyrosol and hydroxytyrosol by π-π stacking. The results were fully satisfactory as to rebinding: DVB-crosslinked molecularly imprinted polymers (MIPs) gave over 50 nmol/mg rebinding. The sensitivity of the fluorescent MIPs was excellent, with LODs in the pM range. The sensing polymers were tested on real olive leaves extracts, with very good performance and negligible matrix effects.

Oleocanthal Quantification Using 1H NMR Spectroscopy and Polyphenols HPLC Analysis of Olive Oil from the Bianchera/Belica Cultivar

“…In any case, it is evident that the leaves of the Bianchera cultivar are rich in polyphenols and can be considered as a good source of these compounds. Moreover, from our previous work [ 46 ], which was aimed at sensing phenols in aqueous olive leaves extracts by means of fluorescent imprinted nanoparticles, we verified via HPLC that the main polyphenol present in aqueous olive leaves extracts was oleuropein.…”

Fluorescent Imprinted Nanoparticles for Sensing of Chlorogenic Acid in Coffee Extracts

“…More recently, we also developed fluorescent MIPs for the analysis of tyrosol and hydroxytyrosol in aqueous olive leaves extracts using the non-covalent approach [16], as well as for the detection of irinotecan in human plasma using a napthalimide polymerisable derivative (2-allyl-6-[2-(aminoethyl)-amino]napthalimide) as a functional monomer [17].…”

“…The concentration of the free template at each time was calculated as reported in our previous work [16].…”

“…4-Vinylpyridine (4VP) has already been used as a functional monomer for interactions with 5-CQA and is one of the most common functional monomers used for the preparation of MIPs due to its commercial availability and low cost [21,22]. 4-[(2-ethylenediamine)]-N-allyl1,8-naphtalimide 7 is a fluorescent molecule synthesized from 4-chloro-1,8-naphtalic anhydride [18], and its analogues have been widely used in the literature to obtain fluorescent polymers to be used in sensor development [16,23]. The interactions between the template and each functional monomer were studied by 1 H-NMR in DMSO-d 6 by progressive addition of a solution of 5-CQA to a solution of the functional monomer in order to evaluate the variations of the chemical shift of the single protons of the monomer.…”

Biosensors and Sensing Systems for Rapid Analysis of Phenolic Compounds from Plants: A Comprehensive Review

“…Whereas the majority of fluorescent MIPs for phenolic compounds detection reported in literature are based on fluorescence quenching, very recently our group developed signal-on fluorescent imprinted nanoparticles for sensing of tyrosol, hydroxytyrosol, and oleuropein in aqueous olive leaves extracts [ 143 ]. Best results were obtained when using 4-vinylpiridine as functional monomer, a fluorescent co-monomer based on fluorescein, 1,4-divinylbenzene as crosslinker and tyrosol as template.…”