pH Responsive Hydrogen Bonding Motif to Improve the Sensitivity of Tumor Imaging
Abstract
Magnetic resonance imaging (MRI) is a powerful non-invasive medical diagnostic technique. Superparamagnetic iron oxide nanoparticles (SPIO) are effective contrast agents and provide high sensitivity contrast in MRI. Recent research has demonstrated that nanoparticle clusters exhibit significantly higher relaxivity than individual nanoparticles.
In order to increase the sensitivity of tumor imaging, supramolecular chemistry was introduced to this field and a novel conjugation method was developed using click chemistry between azide functionalized nanoparticles and pH-sensitive hydrogen bonding building blocks. This pH-sensitive hydrogen bonded complex was synthesized to cluster nanoparticles under mildly acidic biological conditions.
Due to the unexpected X-ray crystal structure of the acceptor molecule, erroneous results were obtained. An association constant (Ka) was determined via 1H NMR titration of a similar hydrogen bonding system and the resulting value of 194 M-1 in DMSO. This result indicates the potential feasibility of this project. The synthesis, characterization, and tests of functionalized SPIO and monomers are reported.