Synthesis of lenvatinib-loaded upconversion@polydopamine nanocomposites for upconversion luminescence imaging-guided chemo-photothermal synergistic therapy of anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is the most malignant and aggressive of all classifications of thyroid cancer. ATC normally has poor prognosis after classic treatments such as surgery, endocrine therapy, radiotherapy and chemotherapy. Herein, a novel nanocomposite (named as UCNP@PDA@LEN) has been synthesized for chemo-photothermal therapy of ATC, which is based on a NaErF4:Tm3+@NaYbF4@NaYF4:Nd3+ upconverting nanoparticle (UCNP) as the core, a near-infrared light (NIR)-absorbing polydopamine (PDA) as the shell, and lenvatinib (LEN) as a chemotherapeutic drug. The as-prepared multifunctional UCNP@PDA@LEN exhibits excellent photothermal conversion capability (η = 30.7%), good photothermal stability and reasonable biocompatibility. Owing to the high UCL emission and good tumor accumulation ability, the UCL imaging of mouse-bearing ATC (i.e., C643 tumor) has been achieved by UCNP@PDA@LEN. Under 808 nm NIR laser irradiation, the UCNP@PDA@LEN shows a synergistic interaction between photothermal therapy (PTT) and chemotherapy (CT), resulting in strongly suppressed mouse-bearing C643 tumor. The results provide an explicit approach for developing theranostics with high anti-ATC efficiency.