Nanobubbles for Precision Oncology: Preclinical Evaluation of Molecular Targeted Ultrasound Contrast Agents in a Rabbit Model

PurposeTo evaluate the use of prostate-specific membrane antigen-targeted nanobubbles (PSMA-NBs) for contrast-enhanced ultrasound (CEUS) in a rabbit model, aiming to enhance prostate cancer imaging and guide clinical translation. Materials and MethodsPSMA-NBs were formulated using lipid encapsulation and PSMA-targeting ligands. Human PSMA-positive PC3pip-GFP cells were injected into the prostates of immunosuppressed rabbits to establish tumors. Tumor growth was monitored via B-mode ultrasound (US) and MRI. CEUS was conducted with PSMA-NBs and commercial microbubbles (MBs). Time-intensity curve (TIC) analysis, parametric mapping, and post-mortem histological correlation were performed. ResultsPSMA-NBs demonstrated 1.60-fold (p = 0.013) and 1.50-fold (p = 0.016) higher peak signal intensities in the tumor core and rim, respectively, compared to MBs, with significantly longer mean transit times (MTTs) in the core (4.20-fold; p = 0.001) and rim (4.50-fold; p < 0.001). At 10 minutes, PSMA-NBs retained detectable signals in tumor rim (7.0 {+/-} 3.0 a.u.), core (3.0 {+/-} 1.0 a.u.), and surrounding tissues (12.0 {+/-} 5.0 a.u.), unlike MBs. Larger tumors showed prolonged MTTs in the rim (3.70 {+/-} 0.50 min) and surrounding tissues (4.60 {+/-} 0.50 min) compared to the core (2.10 {+/-} 0.40 min, p < 0.001). TIC parameters (MTT, AUCwo) correlated with tumor viability, emphasizing PSMA-NBs ability to delineate viable regions. ConclusionPSMA-NBs significantly enhanced prostate cancer imaging, correlating with tumor viability and outperforming MBs. These findings support their potential to improve diagnostic precision and guide targeted therapy in prostate cancer.