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

Ada Stavro Santarosa,Federico Berti,Antonella Calabretti,Martina Tommasini,Cristina Forzato

doi:10.3390/nano10061011

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.

Highlights

The development of simple sensors able to detect and quantify specific analytes is a continually expanding sector
The interactions of the template with the functional monomers is the key step in formulating the molecularly imprinted polymers (MIPs) composition, based on weak non-covalent interactions such as hydrogen bonding, ionic interactions or van der Waals forces depending on the structure of the template
Both TY and HT have an aromatic ring that could be involved in π-π stacking with other aromatic functions or unsaturated systems, while the phenolic groups could act as donors or receptors for hydrogen bonds

Summary

Introduction

The development of simple sensors able to detect and quantify specific analytes is a continually expanding sector. Among the several recognition elements that are necessary to build up a sensor, the molecularly imprinted polymers (MIPs) approach has received great attention in recent years toward obtaining sensing nanomaterials, since it is specific, cheap and stable to different conditions, albeit with lower sensitivity and selectivity in comparison to antibodies or other recognition elements [1]. Due to their enzyme and antibody mimicking approach, the “lock and key” mechanism, MIPs are usually defined as biosensors. MIPs have been prepared for the detection of natural toxins, residues of pesticides, veterinary drugs, environmental contaminants from soil and water, abused additives and contaminants from processing and packaging [3]

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