Abstract
Photoacoustic (PA) imaging requires contrast agents which can enhance the contrast and efficiency of tumor targeting, own high thermal stability and long circulation time, and are effective in low doses in vivo. In this study, we developed magnetic porous nano-silica beads with pore-filled gold nanorods (FeAuNSBs) as a multi-functional contrast agent of photoacoustic imaging. It owns the merits of gold nanorods with silica coating – high biocompatibility, PA signal amplification and optical tunability for PA signal generation. The magnetic property of its embedded iron oxide is used to improve tumor targeting, i.e., magnetic targeting. Phantom experiments were performed to confirm the tunability of FeAuNSB’s optical absorbance in near-infrared light, which ranges from 600-900nm, which allows us to avoid the interference of blood. Experiments with exposure of the phantom to laser pulses demonsrated the higher photothermal stability of FeAuNSBs. The wavelength of peak optical absorption was also sustained. The magnetic targeting property of FeAuNSBs enhanced the contrast in tumor regions by approximately 17 dB. It was also found that the FeAuNSB aggregation caused by magnetic targeting increased the contrast in ultrasound imaging. The in-vivo experimental results showed that with the magnet targeting to a tumor, we obtained a high contrast increase of about 10 dB over the targeted region in PA and US images, which is higher than 2 dB achieved using conventional AuNRs. Overall, we proved the feasibility of FeAuNSBs as a good tumor targeting contrast agent of PA imaging. Future work will focus on verification of FeAuNSB’s performance on photothermal therapy with PA image guidance.