Cross-linked polydimethylsiloxane colloid as novel contrast agent for gastrointestinal magnetic resonance imaging: Transient nuclear Overhauser effect within the interface

Abstract

<jats:p> With good contrast in T<jats:sub>1</jats:sub> and T<jats:sub>2</jats:sub> weighted imaging as well as low toxicity in 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, this work proposes the cross-linked polydimethylsiloxane colloids as a novel non-ionic contrast agent for gastrointestinal magnetic resonance imaging. The experiments of nuclear magnetic resonance spectra and relaxation show that within the interface of the colloids, there are nuclear Overhauser effect and transient nuclear Overhauser effect (cross-relaxation). Regarding the longitudinal relaxation experiments of CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>O segments of Tween 80, a two spins system is found and modeled well by the equation [Formula: see text] which is deduced based on the transient nuclear Overhauser effect proposed by Solomon. The arbitrary constant X is additionally added with the initial conditions ( I<jats:sub>z</jats:sub> − I<jats:sub>0</jats:sub>) <jats:sub>t</jats:sub><jats:sub>=0</jats:sub> = −2 XS<jats:sub>0</jats:sub> and ( S<jats:sub>z</jats:sub> − S<jats:sub>0</jats:sub>) <jats:sub>t</jats:sub><jats:sub>=0</jats:sub> = −2 S<jats:sub>0</jats:sub>. For the two spins system, D<jats:sub>1</jats:sub> and T<jats:sub>1</jats:sub> are corresponding to longitudinal relaxation times of the bound water and the CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>O respectively. Concerning the transverse relaxation experiments of the CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>O, they agree with the equation with three exponential decays, defined by three relaxation times, likely corresponding to three mechanisms. These mechanisms possibly are intramolecular and intermolecular dipole–dipole (DD) interactions and scalar coupling. Within the interface, hydrogen bonding causes the positive nuclear Overhauser effect of the CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>O’s nuclear magnetic resonance spectra, the transient nuclear Overhauser effect of the CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>O’s longitudinal relaxation experiments and the intermolecular dipole–dipole interactions of the CH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>O’s transverse relaxation experiments. </jats:p>