Nanoparticle-Assisted NMR Detection of Organic Anions: From Chemosensing to Chromatography

Abstract

Monolayer-protected nanoparticles provide a straightforward access to self-organized receptors that selectively bind different substrates in water. Molecules featuring different kinds of noncovalent interactions (namely, hydrophobic, ion pairing, and metal-ligand coordination) can be grafted on the nanoparticle surface to provide tailored binding sites for virtually any class of substrate. Not only the selectivity but also the strength of these interactions can be modulated. Such recognition ability can be exploited with new sensing protocols, based on NMR magnetization transfer and diffusion-ordered spectroscopy (DOSY), to detect and identify organic molecules in complex mixtures.

Nanoparticle-Based Receptors Mimic Protein-Ligand Recognition

“…In addition, residence time related to each recognition event was quite long, lasting tens of nanoseconds (Figure 8B). In NOE-pumping experiments, a sizable magnetization transfer between the spins of the monolayer and those of the analyte is detected only when the residence time of the analyte in the monolayer is comparable, or longer, than the rotational correlation time ( τ c ) of the nanoparticle 24 . Inspection of Figure 8B, where the binding events are sorted according to their binding residence time, reveals that many binding events of salicylate visibly exceed τ c of the nanoparticle.…”

“…In this regard, some of us recently proposed nuclear magnetic resonance (NMR) chemosensing as a protocol that exploits the molecular recognition ability of monolayer-protected gold nanoparticles (AuNPs, about 2 nm core diameter) in order to detect target analytes 21, 22, 23, 24. Typically, these analytes are small organic molecules such as salicylate.…”

Differential Attenuation of NMR Signals by Complementary Ion‐Exchange Resin Beads for De Novo Analysis of Complex Metabolomics Mixtures

“…The addition of lanthanide ions can be used to monitor molecule‐ or resonance‐specific line broadening through paramagnetic relaxation . Monolayer‐protected nanoparticles and SDS micelles have been demonstrated to allow better differentiation between different organic molecules in mixtures using DOSY. Unfortunately, in the context of complex mixtures of unknown metabolites, the discrimination power of these methods is often not sufficient to accurately attribute resonances to the molecules they belong to.…”

Knowns and unknowns in metabolomics identified by multidimensional NMR and hybrid MS/NMR methods

“…In fact, such a chemosensing strategy has been demonstrated recently for relatively simple synthetic mixtures. [42] This research direction has strong potential by exploiting synergies between synthetic chemistry, nanoscience, and metabolomics.…”