RGD-functionalized Melanin Nanoparticles For Intraoperative Photoacoustic Imaging-guided Breast Cancer Surgery

Breast cancer ranks first among cancer incidence and mortality in women,and has become a serious threat to women’s health.Surgery is an important method for the treatment of breast cancer,and breast conserving surgery has become one of the standard treatment options for early breast cancer.Surgical margin status is a critical factor affecting local recurrence and prognosis.However,according to the post-surgical histological margin examination,20%-40%of breast cancer patients undergo reexcision to achieve tumour-free margins.Therefore,breast conserving surgery needs an accurate and reliable intraoperative margin assessment method.Photoacoustic imaging is a non-invasive and non-ionizing imaging modality offering rich optical contrast and high depth-to-resolution ratio deep-tissue imaging.It can be used to accurately locate tumour lesions and guide surgical resection in real-time visualization,which is helpful to realize real-time and accurate assessment of surgical margin status in breast conserving surgery.In this study,we describe water-soluble melanin nanoparticles(MNPs)conjugated with cyclic Arg-Gly-Asp(cRGD)peptides for breast cancer photoacoustic imaging and surgery navigation.The size of the synthesized cRGD-MNPs is about 8 nm,which has good photoacoustic properties and stability.The cRGD-MNPs exhibited excellent tumour-targeting in vitro and in vivo,with low toxicity.Intravenous administration of cRGD-MNPs to MDA-MB-231 tumour-bearing mice showed an approximately 2.1-fold enhancement in photoacoustic intensity at 2 h,and the ratio of the photoacoustic intensity at the tumour site compared to that in the surrounding normal tissue was 3.2 ± 0.04,which was much higher than that using MNPs alone(1.7±0.29).Similar results were observed in FVB/N-Tg(MMTV-PyVT)634Mul/J spontaneous breast cancer mice.The photoacoustic signal intensity of mammary glands containing tumour was enhanced(2.5±0.19-fold)after the injection of the cRGD-MNPs,while the signal intensity of normal mammary glands did not change significantly after injection.Preoperative screening by photoacoustic imaging using cRGD-MNPs could locate the tumour,assess tumour volume and offer a three-dimensional reconstruction of breast cancer for accurate surgical planning.Next,photoacoustic imaging is used to guide tumour resection and detected residual lesions in real time to ensure complete tumour resection.We found that photoacoustic imaging could identify residual lesions as small as 2 mm.Surgical resection following real-time photoacoustic imaging on the tumour bed showed high consistency with histopathological analysis.These results highlight that cRGD-MNPs combined with photoacoustic imaging provide a powerful tool for breast cancer imaging and precise tumour resection.cRGDMNPs have great potential for clinical translation.