We designed a multifunctional
platform by coloading DOX, an antitumor
drug, and imiquimod (R837), an immune adjuvant against Toll-like-receptor-7
(TLR-7), onto polydopamine nanoparticles (PDA NPs), a photothermal
therapy (PTT) agent, to develop PDA/DOX&R837 NPs used as combined
photothermal therapy, chemotherapy, and immunotherapy in order to
enhance the cancer therapeutic effects. For a high delivery to malignant
tumors, a folate ligand–receptor recognition molecule was grafted
to the nanoparticle surface for a higher cellular uptake efficiency.
The particle size, ζ potential, morphology, drug loading content,
and drug release profiles of FA-PDA/DOX&R837 NPs were investigated.
The antitumor effects under near-infrared (NIR) laser radiation were
evaluated, and our results showed that a three-mode strategy combined
therapy was significantly superior to single-mode therapy for tumor
suppression. The synergetic toxicity of hyperthermia and DOX almost
completely eliminated tumors, and together with R837, they further
promoted the maturation of dendritic cells to induce a strong antitumor
immune response, making tumor recurrence substantially lower than
that without R837. This platform can be used as a potential targeted
drug delivery system for combined cancer therapy.