(343c) Microfabriction of GEM Sensors for Quantitative Glucose Mapping and Multiplexing with MRI

Magnetic resonance imaging (MRI) has widespread clinical application due to its operation in the radio frequency range where distortion from biological tissue is negligible, but generally lacks quantitation and multiplexing strategies. In this work, we present recent progress in microfabricating glucose-responsive Geometrically Encoded Magnetic (GEM) sensors, a new sensor platform with inherent advantages to address the quantitation and multiplexing issues with MRI. GEM sensors are composed of size-changing ‘smart’ hydrogels that are infused with magnetic nanoparticles. The magnetic nanoparticles create a local magnetic field which in turn produces a resonance frequency offset that distinguishes local hydrogel molecules from surrounding ones on a nuclear magnetic resonance (NMR) spectrum. The smart hydrogel reversibly swells and contracts in response to analyte concentration, actuating a change in the sensor shape, a change in the strength of the locally created magnetic field, and a shift in the offset frequency. Analyte concentration can therefore be read from the relative position of the frequency shift from a starting point, giving an inherently ratiometric signal readout that is not subject to artifacts from sensor concentration. While the GEM sensor concept has been demonstrated with a pH-responsive hydrogel, current efforts are aimed at expanding the range of accessible analytes by determining the proper conditions for GEM sensor microfabrication with a glucose-responsive hydrogel formulation through a cost-effective soft lithography approach. In the future, by constructing GEM sensor shapes with different aspect ratios that correspond to various hydrogel chemistries, a suite of sensors can be built where each analyte concentration corresponds to its relative shift in distinct regions of the NMR spectra, analogous to multiplexing with optical tags.