cRGD-Functionalized Calcium Carbonate Nanoprobe for Enhanced NIR-II Fluorescence Imaging and Tumor-Targeted Navigation

Abstract Indocyanine green (ICG) holds promise for near-infrared-II (NIR-II) fluorescence imaging but is hindered by poor photostability, rapid clearance, and lack of targeting specificity. To address these challenges, we engineered a tumor-targeted nanoprobe (cRGD@ICN) by encapsulating ICG within a calcium carbonate (CaCO3) core, followed by surface functionalization with phospholipids and cyclic RGD (cRGD) peptides. The CaCO3 encapsulation enhanced ICG photostability and amplified NIR-II emission by 9.21-fold relative to free ICG. Meanwhile, cRGD conjugation enabled active targeting of integrin αvβ3, a receptor overexpressed on diverse tumor types. cRGD@ICN showed receptor-mediated endocytosis with specific uptake in HCT116, 4T1, and U87 cells in vitro, along with selective accumulation in human ex vivo colorectal cancer tissues. In vivo NIR-II fluorescence imaging revealed that cRGD@ICN achieved high-contrast tumor monitoring with a signal-to-background ratio (SBR) of 6.54 at 16 h postinjection in HCT116 tumor-bearing mice─markedly outperforming the nontargeted control. More importantly, it also exhibited remarkable tumor-targeting ability across other tumor models (U87, 4T1). With precise tumor imaging, we performed real-time NIR-II fluorescence-guided resection of colorectal tumors, confirmed by the absence of residual tumor in the surgical cavity by H&E analysis. Moreover, primary biosafety assessments confirmed favorable biocompatibility. This work provides a promising strategy to transform ICG into a high-performance NIR-II fluorescent nanoprobe and offers a potential approach for precision image-guided oncologic surgery.