Perylene Diimide-Grafted Polymeric Nanoparticles Chelated with Gd³⁺ for Photoacoustic/T₁-Weighted Magnetic Resonance Imaging-Guided Photothermal Therapy

Developing versatile and easily prepared nanomaterials with both imaging and therapeutic properties have received significant attention in cancer diagnostics and therapeutics. Here, we facilely fabricated Gd³⁺-chelated poly(isobutylene-alt-maleic anhydride) (PMA) framework pendent with perylene-3,4,9,10-tetracarboxylic diimide (PDI) derivatives and poly(ethylene glycol) (PEG) as an efficient theranostic platform for dual-modal photoacoustic imaging (PAI) and magnetic resonance imaging (MRI)-guided photothermal therapy. The obtained polymeric nanoparticles (NPs) chelated with Gd³⁺ (PMA-PDI-PEG-Gd NPs) exhibited a high T₁ relaxivity coefficient (13.95 mM^-1 s^-1) even at the higher magnetic fields. After 3.5 h of tail vein injection of PMA-PDI-PEG-Gd NPs, the tumor areas showed conspicuous enhancement in both photoacoustic signal and T₁-weighted MRI intensity, indicating the efficient accumulation of PMA-PDI-PEG-Gd NPs owing to the enhanced permeation and retention effect. In addition, the excellent tumor ablation therapeutic effect in vivo was demonstrated with living mice. Overall, our work illustrated a straightforward synthetic strategy for engineering multifunctional polymeric nanoparticles for dual-modal imaging to obtain more accurate information for efficient diagnosis and therapy.