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.
Keywords: Chemo-photothermal therapy; Photoacoustic imaging; Single walled carbon nanohorns; Tumor metastasis.