Simple D-A-D Structural Bisbithiophenyl Diketopyrrolopyrrole as Efficient Bioimaging and Photothermal Agents

Design and synthesis of biocompatible and multifunctional photothermal agents is crucial for effective cancer phototherapy. In order to achieve this ambition, simple D-A-D structural bisbithiophenyl diketopyrrolopyrrole (TDPP) was fabricated. In this molecule, the donor, 2-thiophenylboric acid, was conjugated via Suzuki coupling reaction, which could expand the emission wavelength to the red region of the spectrum. TDPP could self-assemble into stable and uniform nanoparticles (TDPP NPs) in assistant of amphiphilic Pluronic F-127 polymer. Exposing TDPP NPs (100 μg/mL) aqueous dispersion to 638 nm (0.61 W/cm²) laser irradiation resulted in a temperature elevation of approximately 30 °C within 5 min, which is high enough for inducing the cytotoxicity and tumor inhibition. Because of the bathochromic shift absorption of TDPP NPs in water, TDPP NPs could also act as a contrast agent for near-infrared fluorescence imaging (NIRF) to visualize the drug distribution in vivo. Coupled with the infrared thermal imaging properties of the photothermal agent, TDPP NPs were proven to be a multifunctional theranostic agent for dual-modal imaging-guided phototherapy.