Methotrexate–Camptothecin Prodrug Nanoassemblies as a Versatile Nanoplatform for Biomodal Imaging-Guided Self-Active Targeted and Synergistic Chemotherapy

"All-in-one" carrier-free-based nano-multi-drug self-delivery system could combine triple advantages of small molecules, nanoscale characteristics, and synergistic combination therapy together. Researches have showed that dual-acting small-molecular methotrexate (MTX) could target and kill the folate-receptor-overexpressing cancer cells. Inspired by this mechanism, a novel collaborative early-phase tumor-selective targeting and late-phase synergistic anticancer approach was developed for the self-assembly of chemotherapeutic drug-drug conjugate, which showed various advantages of more simplicity, efficiency, and flexibility over the conventional approach based only on single or combination cancer chemotherapy. MTX and 10-hydroxyl camptothecin (CPT) were chosen to conjugate through ester linkage. Because of the amphiphilicity and ionicity, MTX-CPT conjugates as molecular building blocks could self-assemble into MTX-CPT nanoparticles (MTX-CPT NPs) in aqueous solution, thus notably improving the aqueous solubility of CPT and the membrane permeability of MTX. The MTX-CPT NPs with a precise drug-to-drug ratio showed pH-/esterase-responsive drug release, sequential function "Targeting-Anticancer" switch, and real-time monitoring fluorescence "Off-On" switch. By doping with a lipophilic near-infrared (NIR) cyanine dye (e.g., 1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide, DiR), the prepared DiR-loaded MTX-CPT NPs acted as an effective probe for in vivo NIR fluorescence (NIRF) and photoacoustic (PA) dual-modal imaging. Both in vitro and in vivo studies demonstrated that MTX-CPT NPs could specifically codeliver multidrug to different sites of action with distinct anticancer mechanisms to kill folate-receptor-overexpressing tumor cells in a synergistic way. This novel, simple, and highly convergent self-targeting nanomulti-drug codelivery system exhibited great potential in cancer therapy.