Plasmonic-doped melanin-mimic for CXCR4-targeted NIR-II photoacoustic computed tomography-guided photothermal ablation of orthotopic hepatocellular carcinoma

Effective and noninvasive diagnosis and prompt treatment of early-stage hepatocellular carcinoma (HCC) are urgently needed to reduce its mortality rate. Herein, the integration of high-resolution diagnostic second near-infrared (NIR-II) photoacoustic computed tomography (PACT) and imaging-guided targeted photothermal ablation of orthotopic small HCC (SHCC) is presented for the first time, which was enabled by a plasmonic platinum (Pt)-doped polydopamine melanin-mimic nanoagent. As designed, an antibody-modified nanoagent (designated Pt@PDA-c) with a plasmonic blackbody-like NIR absorption and superior photothermal conversion efficiency (71.3%) selectively targeted and killed CXCR4-overexpressing HCC (HepG2) cells, which was validated in in vitro experiments. The targeted accumulation properties of Pt@PDA-c in vivo were previously recognized by demonstrating effective NIR-II PA imaging and photothermal ablation in a subcutaneous HCC mouse model. Subsequently, with real-time quantitative guidance by PACT for the accurate diagnosis of intraabdominal SHCC (approximately 4 mm depth), the effective and noninvasive photothermal ablation of SHCCs was successfully demonstrated in an orthotopic tumor-bearing mouse model without damaging adjacent liver tissues. These results show a great potential of NIR-II PACT-guided noninvasive photothermal therapy as an innovative phototheranostic approach and expand the biomedical applications of melanin-mimic materials. Statement of significance: In this paper, we report the first diagnostic NIR-II photoacoustic computed tomography (PACT)-guided noninvasive photothermal ablation of small hepatocellular carcinoma (SHCC) located in deep tissues in orthotopic tumor-bearing mice; this process is empowered by a polydopamine-based melanin-mimic tumor-targeting nanoagent doped with plasmonic platinum that provides superior NIR-II (1064 nm) absorption and photothermal conversion efficiency of 71.3%. Following surface modification with anti-CXCR4 antibodies, the nanoagent (namely Pt@PDA-c) can selectively target CXCR4-overexpressed HepG2 carcinoma cells and tumor lesions, and serve as the theranostic agent for both NIR-II PACT-based diagnosis of orthotopic SHCC (diameter less than 5 mm) and efficient NIR-II PTT in vivo. This study may also extend the potential of melanin-derived blackbody materials for optical-biomedical and water distillation applications.