RGD-Functionalized Melanin Nanoparticles for Intraoperative Photoacoustic Imaging-Guided Breast Cancer Surgery

Abstract Purpose: Obtaining tumour-free margins is critical for avoiding re-excision and 35 reducing local recurrence following breast-conserving surgery (BCS); however, it 36 remains challenging. Imaging-guided surgery provides precise detection of residual 37 lesions and assists surgical resection. Herein, we describe water-soluble melanin 38 nanoparticles (MNPs) conjugated with cyclic Arg-Gly-Asp (cRGD) peptides for breast 39 cancer photoacoustic imaging (PAI) and surgery navigation. 40Methods: cRGD-MNPs was synthesized and characterized for morphology, 41 photoacoustic characteristics and stability. Tumour targeting and toxicity were 42 determined by cells and tumour-bearing mice. PAI was used to locate the tumour and 43 guide surgical resection in MDA-MB-231 tumour-bearing mice. 44Results: The cRGD-MNPs exhibited excellent tumour-targeting in vitro and in vivo, 45 with low toxicity. Intravenous administration of cRGD-MNPs to MDA-MB-231 46 tumour-bearing mice showed an approximately 2.1-fold enhancement in photoacoustic 47 (PA) intensity at 2 h, and the ratio of the PA intensity at the tumour site compared to 48 that in the surrounding normal tissue was 3.2 ± 0.1, which was much higher than that 49 using MNPs alone (1.7 ± 0.3). Similarly, the PA signal in the mammary glands 50 containing spontaneous breast cancer was enhanced (2.5 ± 0.3-fold) in MMTV-PyVT 51 transgenic murine model. Preoperative screening by PAI could assess tumour volume 52 and offer a three-dimensional (3D) reconstruction image for accurate surgical planning. 53 Surgical resection following real-time PAI on the tumour bed showed high consistency 54 with histopathological analysis. 55Conclusion: These results highlight that cRGD-MNPs combined with PAI provide 56 a powerful tool for breast cancer imaging and precise tumour resection. cRGD-MNPs 57 with good PA properties have great potential for clinical translation.