IR820 functionalized melanin nanoplates for dual-modal imaging and photothermal tumor eradication

Melanin as an endogenous biomolecule is widely applied in the biomedical field, focusing especially on diagnostic imaging and photothermal therapy in cancer treatment. However, its photothermal conversion efficiency, a benchmark in tumor photothermal therapy (PTT), often could not satisfy PTT requirements to some degree, and this greatly influenced its use in photothermal cancer therapy. As for fluorescence imaging, a small-molecule NIR dye as a fluorescence probe is easily and rapidly metabolized in vivo, resulting in low accumulation in a tumor. To overcome these problems, we attempt to use melanin as a carrier to conjugate a fluorochrome, a recombinant small NIR dye IR820 nanoplatform containing melanin (MNP-PEG-IR820 abbreviated to MPI). The addition of IR820 not only enhances the PTT ability of the nanoplatform, but also endows the material with excellent NIR fluorescence behavior. Most importantly, the integration of fluorescence dye and melanin improves the circulation and stability performance of IR820 while reducing its toxicity in vivo, owing to the protectivity of melanin. Thus, the diagnostic capability is enhanced. Meanwhile, the behavior of the nanoplatform in PAI/PTT is significantly improved. The in vitro investigations reveal that the MPI NPs afford a potent PTT effect and ideal resistance to photobleaching. After intravenous injection, the MPI NPs display effective PTT tumor eradication in a Hep-2 tumor bearing mouse model with excellent dual NIR-I fluorescence/photoacoustic imaging guided phototherapy. Hence, our work shows the potential of MPI NPs as nano-theranostics for biomedical application to laryngocarcinoma.