Methods and compounds for detection and binding of aldehydes

A method of detecting a freely diffusing small molecule aldehyde in a subject comprising administering an aldehyde-binding compound of Formula I to the subject and detecting the product of the compound of Formula I and the freely diffusing small molecule aldehyde using magnetic resonance imaging (MRI), CEST-MRI or positron emission tomography (PET) imaging;

• wherein:
• X is C or N;
• Z is H, alkyl, cycloalkyl, or aryl;
• Y1 and Y3 are H;
• Y2 is CHs3—O—;
• and
• Y4 is independently:
• H;
• a substituent selected from the group consisting of Br, CI, I, nitro, sulfo, carboxy, hydroxyl, alkoxy, cycloalkoxy, aryloxy, C1-6 alkyl, aryl, cycloalkyl, alkyne, propargyl, and tetrazine;
• wherein detection of said freely diffusing small molecule aldehyde is indicative of a brain injury or of cell death optionally wherein the aldehyde-binding compound additionally comprises a radio-label for use in positron emission tomography imaging.