Hyperbranched\nPolymeric <sup>19</sup>F MRI Contrast\nAgents with Long <i>T</i><sub>2</sub> Relaxation Time Based\non β‑Cyclodextrin and Phosphorycholine

<sup>19</sup>F magnetic resonance imaging (<sup>19</sup>F MRI)\nis gaining attention as an emerging diagnostic technology. Effective <sup>19</sup>F MRI contrast agents (CAs) for in vivo applications require\na long transverse (or spin–spin) relaxation time (<i>T</i><sub>2</sub>), short longitudinal (or spin–lattice) relaxation\ntime (<i>T</i><sub>1</sub>), high fluorine content, and\nexcellent biocompatibility. Here, we present a novel hyperbranched\npolymeric <sup>19</sup>F MRI CA based on β-cyclodextrin and\nphosphorylcholine. The influence of the branching degree and fluorine\ncontent on <i>T</i><sub>2</sub> was thoroughly investigated.\nResults demonstrated a maximum fluorine content of 11.85% and a <i>T</i><sub>2</sub> of 612 ms. This hyperbranched polymeric <sup>19</sup>F MRI CA exhibited both great biocompatibility against cells\nand organs of mice and high-performance imaging capabilities both\nin vitro and in vivo. The research provides positive insights into\nthe synthesis strategies, topological design, and selection of fluorine\ntags for <sup>19</sup>F MRI CAs.