Ultrasonography-assisted near-infrared spectroscopy imaging enhanced by gold nanorods in a xenograft mouse model of prostate cancer

Abstract

Purpose: This study aimed to develop and evaluate a near-infrared spectroscopy (NIRS) system enhanced by gold nanorods (GNRs) for the detection of prostate cancer using phantom and xenograft mouse models. Methods: A hybrid ultrasound-NIRS (US-NIRS) system was created with a 785 nm wavelength, integrating eight laser diodes and four detectors with a linear ultrasound probe. Software for processing near-infrared (NIR) signals was developed using an engineering toolkit and an image reconstruction package. Two optical phantoms simulating prostate cancer were constructed using TiO2 for scattering effects and India ink for absorption effects, each containing a cylindrical cavity for GNRs positioned at depths of 1 cm and 2 cm. A xenograft mouse model was prepared by injecting PC-3 cells into the right flank of nude mice. PEGylated GNRs (GNR-PEG) were synthesized. US-NIRS imaging was performed on mice before and after intravenous injection of GNR-PEG. Results: Ultrasonography revealed solid, vascular tumors without necrosis or hemorrhage. Preinjection NIRS showed higher baseline NIR absorbance in tumors compared to normal tissue (optical depths: 0.26, 1.52, and 0.24 for the 1.5 cm, 1.4 cm, and 0.5 cm tumors, respectively). After GNR-PEG injection, tumor optical depths significantly increased (3.36, 4.39, and 1.69 for the 1.5 cm, 1.4 cm, and 0.5 cm tumors, respectively), peaking around 5 minutes, and subsequently decreasing towards baseline levels by 60 minutes. Conclusion: A US-NIRS hybrid imaging system enhanced by GNR-PEG demonstrated increased NIR absorption in prostate cancer xenografts. This fusion imaging technique holds potential for future clinical applications in detecting prostate cancer.