MRI can provide anatomical details and high-quality three-dimensional images of soft tissue, but its sensitivity is low. The two highly complementary imaging combinations, magnetic resonance and photoacoustic, can yield more and more comprehensive information to achieve accurate photothermal treatment. The Zhifei Dai's group linked four nitrogen twelve ring four gadolinium acetate to polypyrrole nanoparticles via polyethylene glycol, the site of the tumor can be selectively attached to the tumor after intravenous injection, the near-infrared laser was used to irradiate the tumor accurately, and the complete ablation of the tumor was achieved after two weeks, and the damage to the normal cells around the tumor was reduced. The paper had been published in Advanced Functional Materials and highlighted.
The above work has been supported by the National Outstanding Youth Science Foundation and the National Natural Science Key fund of China.
Polypyrrole nanoparticles conjugating gadolinium chelates were successfully fabricated for dual-modal magnetic resonance imaging (MRI) and photoa- coustic imaging guided photothermal therapy of cancer, from a mixture
of pyrrole and pyrrole-1-propanoic acid through a facile one-step aqueous dispersion polymerization, followed by covalent attachment of gadolinium chelate, using polyethylene glycol as a linker. The obtained PEGylated poly- pyrrole nanoparticles conjugating gadolinium chelates (Gd-PEG-PPy NPs), sized around around 70 nm, exhibited a high T1 relaxivity coefficient of 10.61 L mM-¹s-¹, more than twice as high as that of the relating free Gd3+ complex (4.2 L mM-¹s-¹). After 24 h intravenous injection of Gd-PEG-PPy NPs, the tumor sites exhibited obvious enhancement in both T1-weighted MRI intensity and photoacoustic signal compared with that before injection, indicating the efficient accumulation of Gd-PEG-PPy NPs due to the introduc- tion of the PEG layer onto the particle surface. In addition, tumor growth could be effectively inhibited after treatment with Gd-PEG-PPy NPs in combination with near-infrared laser irradiation. The passive targeting and high MRI/photo- acoustic contrast capability of Gd-PEG-PPy NPs are quite favorable for precise cancer diagnosing and locating the tumor site to guide the external laser irra- diation for photothermal ablation of tumors without damaging the surrounding healthy tissues. Therefore, Gd-PEG-PPy NPs may assist in better monitoring the therapeutic process, and contribute to developing more effective “personal- ized medicine,” showing great potential for cancer diagnosis and therapy.