Indocyanine Green-Loaded Nanobubbles Targeting Carbonic Anhydrase IX for Multimodal Imaging of Renal Cell Carcinoma

Abstract

Background and Purpose The early diagnosis and differential diagnosis of renal cell carcinoma (RCC) has always been a clinical difficulty and a research focus. Carbonic anhydrase IX (CA IX) is highly expressed on the cell membrane of RCC but is not expressed in normal renal tissues. In this study, nanobubbles (NBs) targeting CA IX with ultrasound and photoacoustic multimodal imaging capabilities were prepared to explore a new method for the diagnosis and differential diagnosis of RCC. Methods Indocyanine green (ICG)-loaded lipid NBs (ICG-NBs) were prepared by using the filming rehydration method, and anti-CA IX polypeptides (ACPs) were attached to their surfaces to prepare CA IX-targeted NBs (ACP/ICG-NBs). The particle size, zeta potential and ICG encapsulation efficiency of these nanobubbles were measured, and their specific targeting and binding abilities to RCC cells were determined. The in vitro and in vivo ultrasound, photoacoustic and fluorescence imaging characteristics of these nanobubbles were also assessed. Results The particle size of the ACP/ICG-NBs was 475.9 nm in diameter, and their zeta potential was −2.65 mV. Laser confocal microscopy and flow cytometry both confirmed that ACP/ICG-NBs had specific binding activity and ideal affinity to CA IX-positive RCC cells (786-O) but not to CA IX-negative RCC cells (ACHN). The intensities of the in vitro ultrasound, photoacoustic and fluorescence imaging were positively correlated with the concentrations of ACP/ICG-NBs. In in vivo ultrasound and photoacoustic imaging experiments, ACP/ICG-NBs exhibited specific enhanced ultrasound and photoacoustic imaging effects in 786-O xenograft tumors. Conclusion The ICG- and ACP-loaded targeted nanobubbles that we prepared had the capability of ultrasound, photoacoustic and fluorescence multimodal imaging and could specifically enhance the ultrasound and photoacoustic imaging of RCC xenograft tumors. This outcome has potential clinical application value for the diagnosis of RCC at the early stage and the differential diagnosis of benign and malignant kidney tumors.

Effective strategies to enhance the diagnosis and treatment of RCC: The application of biocompatible materials

“…ICG was the first optical contrast agent approved by the U.S. Food and Drug Administration for clinical use because of its excellent photoacoustic and fluorescent imaging capabilities [ 64 ]. Jiang et al developed lipid nanobubbles (ACP/ICG-NBs) containing ICG and conjugated with anti-CAIX polypeptide (ACP) using the filming rehydration technique [ 65 ]. These nanobubbles exhibit ultrasound, photoacoustic, and fluorescence imaging modalities, along with targeted binding to RCC cells, thereby enhancing ultrasound and photoacoustic imaging of RCC xenograft tumors.…”

“…In vivo recognition mechanism of APN–SUB as a color-convertible probe toward APN [ 72 ]; B. Synthetic procedure, anti-tumor drug loading and possible receptor-mediated endocytosis pathway of the targeted UCNPs@MOF core–shell NCs [ 68 ]; C. Illustration of the targeted NBs (ACP/ICG-NBs) that bind specifically to RCC cells expressing CA IX antigen and enhance the ultrasound, photoacoustic and fluorescence imaging of RCC xenograft [ 65 ]. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)…”