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Paramagnetic block copolymers: An effective tool for targeted radiography of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by erosive arthritis. Accurate diagnosis of RA mostly depends on the quality of magnetic resonance imaging (MRI). To obtain stable and clear imaging signals, it is necessary to design and develop a superstable and highly
 sensitive contrast agent. This study synthesized a diblock polymer polyethylene glycol–tert-butyl polyacrylate (PEG-b-PAA) by in situ polyol polymerization, coated it with ultrasmall paramagnetic iron oxide (USPIO), and conjugated folic acid to the PEG-b-PAA/USPIO surface
 to impart targeting function. The addition of USPIO effectively enhanced MRI quality in delayed T2-weighted images (T2WI), as observed through synovial signal changes other than morphological changes, early monitoring RA lesions, and drug treatment response. Enhanced T2WI helped evaluate the
 characteristics of synovial perfusion, which further confirmed the feasibility of MRI using FA-PEG-b-PAA/USPIO. These results showed that FA-PEG-b-PAA/USPIO has great potential in the clinical application of MRI for RA diagnosis.