Synthesis of 5-Fluorouracil Polymer Conjugate and (19)F NMR Analysis of Drug Release for MRI Monitoring

To monitor the release of fluorinated drugs from polymeric carriers, a novel (19)F MRI enzyme-responsive contrast agent was developed and tested. This contrast agent was prepared by conjugation of 5-fluorouracil (5-FU) to hyperbranched poly(N,N-dimethylacrylamide) (HB-PDMA) via an enzyme-degradable peptide linker. Due to the different molecular sizes, the release of 5-FU from the 5-FU polymer conjugate resulted in a sufficiently substantial difference in spin-spin T(2) (19)F NMR/MRI relaxation time that enabled differentiating between attached and released drug states. The 5-FU polymer conjugate exhibited a broad signal and short T(2) relaxation time under (19)F NMR analysis. Incubation with the enzyme induced the release of 5-FU, accompanied by an extension of T(2) relaxation times and an enhancement in the (19)F MRI signal. This approach is promising for application in the convenient monitoring of 5-FU drug release and can be used to monitor the release of other fluorinated drugs.