Effect of structure and intramolecular distances on photoswitchable magnetic resonance imaging contrast agents

College

College of Science

Department/Unit

Chemistry

Document Type

Article

Source Title

Journal of Organic Chemistry

Volume

85

Issue

11

First Page

7333

Last Page

7341

Publication Date

6-5-2020

Abstract

Light-activated sensors are of great interest for biological applications but are limited by the depth of penetration of light. We have been interested in transducing light activation to a magnetic signal that can be detected through noninvasive imaging by magnetic resonance imaging (MRI). We have previously developed agents incorporating spiropyran derivatives as the sensing moiety and characterized features that influence photoswitching; however, we found the MRI response to be unpredictable. In this work, we delve deeper into the potential mechanisms for the observed MRI responses in an effort to better understand the structural effects on controlling magnetic properties. A series of light-activatable MRI contrast agents were synthesized and characterized to assess the effect of spiropyran positioning on contrast agent functions and properties. These compounds are based on the same spiropyran skeleton, also named 1′,3′,3′-trimethyl-6-nitrospiro[chromene-2,2-indoline], which is linked with an MRI contrast agent, gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7-triacetate (DO3A). We investigated the photo-to-magnetic conversion properties of these novel compounds by adjusting linker lengths over a range from three to seven methylene groups. The primary results indicated that the contrast agent with a five-carbon linker (25) showed the highest light-sensing ability after irradiation with visible light. The results will aid in the design of future spiropyran-based MRI sensors. Copyright © 2020 American Chemical Society.

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Digitial Object Identifier (DOI)

10.1021/acs.joc.0c00706

Disciplines

Chemistry

Keywords

Magnetic resonance imaging; Photochromism

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