Dual Chemodrug-Loaded Single-Walled Carbon Nanohorns for Multimodal Imaging-Guided Chemo-Photothermal Therapy of Tumors and Lung Metastases

Tumor combination therapy using nano formulations with multimodal synergistic therapeutic effects shows great potential for complete ablation of tumors. However, targeting tumor metastases with nano structures is a major obstacle for therapy. Therefore, developing a combination therapy system able to target both primary tumors and their metastases at distant sites with synergistic therapy is desirable for the complete eradication of tumors. To this end, a dual chemodrug-loaded theranostic system based on single walled carbon nanohorns (SWNHs) is developed for targeting both primary breast tumors and their lung metastases. Methods: SWNHs were first modified simultaneously with poly (maleic anhydride-alt-1-octadecene) (C18PMH) and methoxypolyethyleneglycol-b-poly-D, L-lactide (mPEG-PLA) via hydrophobic-hydrophobic interactions and π-π stacking. Then cisplatin and doxorubicin (DOX) (2.9:1 molar ratio) were sequentially loaded onto the modified nanohorns in a noninterfering way. After careful examinations of the release profiles of the loaded drugs and the photothermal performance of the dual chemodrug-loaded SWNHs, termed SWNHs/C18PMH/mPEG-PLA-DOX-Pt, the dual drug chemotherapeutic and chemo-photothermal synergetic therapeutic effects on tumor cells were evaluated. Subsequently, the in vivo behavior and tumor accumulation of the drug-loaded SWNHs were studied by photoacoustic imaging (PAI). For chemo-photothermal therapy of tumors, 4T1 tumor bearing mice were intravenously injected with SWNHs/C18PMH/mPEG-PLA-DOX-Pt at a dose of 10 mg/kg b.w. (in SWNHs) and tumors were illuminated by an 808 nm laser (1W/cm2 for 5 min) 24 h post-injection. Results: DOX and cisplatin were loaded onto the modified SWNHs with high efficiency (44 wt% and 66 wt%, respectively) and released in a pH-sensitive, tandem and sustainable manner. The SWNHs/C18PMH/mPEG-PLA-DOX-Pt had a hydrodynamic diameter of 182 ± 3.2 nm, were highly stable in physiological environment, and had both dual drug chemotherapeutic (CI = 0.439) and chemo-photothermal synergistic antitumor effects (CI = 0.396) in vitro. Moreover, the dual drug-loaded SWNHs had a long blood half-life (10.9 h) and could address both the primary breast tumors and their lung metastases after intravenous administration. Consequently, chemo-photothermal combination therapy ablated the primary tumors and simultaneously eradicated the metastatic lung nodules. Conclusion: Our study demonstrates that SWNHs/C18PMH/mPEG-PLA-DOX-Pt is highly potent for chemo-photothermal combination therapy of primary tumors and cocktail chemotherapy of their metastases at a distant site.