Magnetic resonance based contrast agents and devices for in vivo chemical sensing

The goal of this project is to develop injectable MRI readable materials for long-term in vivo monitoring. The materials are customized for different applications and targets based on the materials design process. The materials are designed to have quantum level responses to variations of specific target analytes in their environment. Our current development is focused on monitoring in vivo oxygen and pH levels. Our sensors are implanted through a minimally invasive injection and measured non-invasively using MRI. The changes in material properties appear in the MR scan which corresponds to absolute values oxygen content or pH. Oxygen and pH measurements offer additional information about disease state beyond what is available with current diagnostic tools. Oxygen and pH levels change during disease progression and treatment which necessitates repeated measurement to achieve accurate disease monitoring. Current clinical oxygen probes require re-insertion for each measurement which is invasive and makes sampling the same region difficult. Our sensor overcomes these challenges and provides an optimal alternative by maintaining its physical location after injection and enabling non-invasive repeat measurements.

Tracking hypoxia and/or pH provides clinicians with additional data that can be used to guide treatment in many diseases and pathologies including cancer and traumatic limb injuries. Physicians are able to select the optimal radiation dose and chemotherapeutic to maximize treatment efficacy by monitoring tumor oxygen level. Monitoring of tumor pH offers physicians a quantitative tool to monitor how tumors respond to treatment which enables dose and therapy adjustments. Tracking tissue oxygen levels allows physicians to have a direct measurement of the oxygen content in a patient’s limb following a crush or high impact limb injury. Current clinical standards rely on a pressure measurement to guide treatment. The pressure measurement is a surrogate for oxygen content and does not provide a complete picture of the patient’s injury. Oxygen content information enables physicians to make more informed decisions and avoid, potentially unnecessary, highly invasive surgeries.


C. C. Vassiliou, V. H. Liu, M. J. Cima, Miniaturized, biopsy-implantable chemical sensor with wireless, magnetic resonance readout, Lab on a Chip, 2015, DOI: 10.1039/C5LC00546A

Liu VH, Vassiliou CC, Imaad SM, and Cima MJ; Solid MRI contrast agents for long-term, quantitative in vivo oxygen sensing, Proc Natl Acad Sci USA, 2014; 111(18):6588-93.

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