An imaging/therapeutic molecular probe for ultrasound and photoacoustic dual modality system

Gold nanorods (AuNRs) have been used as contrast enhancement agents for photoacoustic (PA) imaging as well as effective photothermal therapy agents. In the literature, pulsed ultrasound exposures have shown to enhance delivery of fluorescently labeled polystyrene nanoparticles. Microbubbles (MBs) can also substantially enhance the ablation effects. In this study, we develop a US/PA imaging/therapeutic multimodality molecular probe - encapsulated gold nanorods albumin microbubbles (AuMBs) for US/PA imaging. The AuNR solution containing 0.4-M Cysteamine dihydrochloride (5 ml) and 16 mM HNO3 (10 ml) is aged for 30 min. Next, the solution is centrifuged at 5500 rpm for 15 min to remove excess cysteamine. Human serum albumin is added into the AuNR solution and then aged for 24 hour at 4°C. AuNR targeted MBs were generated by sonicating 4 mL of solution containing 1.2% AuNR-HSA, 0.04% avidin, and C₃F₈ gas in phosphate-buffered saline. The AuMBs concentration was 2.41×10⁹ /ml, and their mean diameter was 1319 nm. Phantom experiments were performed to characterize the AuMBs using Polyacrylic Acid gels with a chamber to load the samples. The property of the AuMBs for US/PA dual imaging system was estimated, and modified as a molecular probe. The optical characteristics of the AuMBs were presented. In addition, the potential of the AuMBs in the enhancement of the AuNR based hyperthermia was investigated.