Analytical Sciences

MRI-based Glucose Assay Using Magnetic Nanoparticle Sensors

Satoshi OKADA,*1,*2,*3 Satoko TAKAYASU,*3 Akira SUMIYOSHI,*4 Ichio AOKI,*4 and Hiroyuki NAKAMURA*1

*1 Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503, Japan
*2 JST, PRESTO, 4259 Nagatsuta, Midori, Yokohama, Kanagawa 226-8503, Japan
*3 Health Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
*4 Institute for Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage, Chiba, Chiba 263-8555, Japan

Glucose sensors for NMR relaxometry and magnetic resonance imaging (MRI) can be used for the direct measurement of glucose in turbid biological specimens. Here, we proposed a magnetic glucose sensor based on superparamagnetic iron oxide (SPIO) nanoparticles conjugated to a mannopyranoside derivative and concanavalin A (ConA). The binding of mannopyranoside groups to ConA produced a nanoparticle cluster that was dissociated by competitive binding of glucose to ConA, resulting in changes in the transverse relaxation time (T₂) in a glucose-dependent manner. The sensor gave rise to significant T₂ changes in physiological glucose levels of 3 – 8 mM at a nanoparticle concentration of 0.5 nM. Significant T₂ responses were observed within 6 min of 5 mM glucose detection. Sensor-based MRI by a benchtop 1 tesla scanner permitted a measurement of multiple samples within 8 min. These results demonstrate that the relaxometric glucose sensor could lead to high throughput direct assay of blood samples by using a compact MRI scanner for point-of-care testing.

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