An organogel library for solution NMR analysis of nanoparticle suspensions in non-aqueous samples

Sergey L Sedinkin; Yeongseo An; Pranjali Naik; Igor I Slowing; Vincenzo Venditti

doi:10.1016/j.jmr.2020.106874

An organogel library for solution NMR analysis of nanoparticle suspensions in non-aqueous samples

J Magn Reson. 2020 Dec:321:106874. doi: 10.1016/j.jmr.2020.106874. Epub 2020 Nov 10.

Authors

Sergey L Sedinkin¹, Yeongseo An¹, Pranjali Naik², Igor I Slowing², Vincenzo Venditti³

Affiliations

¹ Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
² Department of Chemistry, Iowa State University, Ames, IA 50011, USA; U.S. Department of Energy, Ames Laboratory, Ames, IA 50011, USA.
³ Department of Chemistry, Iowa State University, Ames, IA 50011, USA; Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA. Electronic address: venditti@iastate.edu.

PMID: 33221669
DOI: 10.1016/j.jmr.2020.106874

Abstract

Surface contrast solution NMR methods (scNMR) are emerging as powerful tools to investigate the adsorption of small molecule ligands to the surface of nanoparticles (NP), returning fundamental insight into the kinetics and thermodynamics of sorption, as well as structural information on the adsorbed species. A prerequisite for the acquisition of high quality solution NMR data is the preparation of homogeneous and stable samples that return consistent NMR spectra and allow extensive signal averaging. Unfortunately, this condition does not apply to NMR samples containing NPs that often show a tendency to sediment and accumulate at the bottom of the NMR tube over the course of the experiment. We have recently shown that preparing NMR samples in an agarose gel matrix inhibits sedimentation and allows the characterization of small molecule-NP interactions by scNMR. Unfortunately, as the agarose gel only forms in aqueous solution, this sample preparation method cannot be used to stabilize NP suspensions in a non-aqueous environment. Here, we introduce a library of 48 organogels, based on low molecular-mass organic gelators (LMOGs), to prepare NMR samples of small molecule/NP systems in a wide range of organic solvents. In addition, we present a simple method that takes advantage of ¹H transverse relaxation (¹H-R₂) measurements to screen the library and identify the best gelator to characterize the small molecule-NP interaction of interest in the solvent of choice. We expect the results of this study will enable the preparation of homogeneous and stable samples of NPs in non-aqueous environments, therefore dramatically increasing the applicability of scNMR to the characterization of heterogeneous interactions and to the investigation of the role played by solvent molecules in regulating the kinetics and thermodynamics of sorption.

Keywords: Heterogeneous interactions; Low molecular-mass organic gelators; Nanoparticle solution interface; Surface Contrast NMR; Surface adsorption.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't