Four-Photon Absorption Iron Complex for Magnetic Resonance/Photoacoustic Dual-Model Imaging and an Enhanced Ferroptosis Process

Four-photon absorption (4PA) multimodal therapeutic agent
applied
to tumor ferroptosis process tracking is rarely reported. In this
paper, two functionalized terpyridine iron complexes (TD-FeCl3, TD-Fe-TD) with four-photon
absorption properties were designed and synthesized. The four-photon
absorption cross sections of TD-FeCl3 reached 6.87 × 10–74cm8·s3·photon–3. Due to its strong near-infrared
absorption, TD-FeCl3 has excellent
photoacoustic imaging (PAI) capability for accurate PA imaging. TD-FeCl3 has an efficient longitudinal
electron relaxation rate (r1 = 2.26 mM–1 s–1) and high spatial resolution,
which can be applied as T1-weighted magnetic resonance
imaging (MRI) contrast agent for tumor imaging in vivo. In addition, Fe3+ as a natural ferroptosis tracer, TD-FeCl3, is able to deplete glutathione
(GSH) effectively, which can further enhance the ferroptosis process.
We found that the series of cheap transition metal complexes has four-photon
absorption activity and can be used as multimodal (MRI/PAI) diagnostic
agents for tumor tracing processes.