In vivo photoacoustic imaging with multiple selective targeting using bioconjugated gold nanorods

In this study, photoacoustic imaging is utilized to probe information from oncogene surface molecules of cancer cell with the aid of specific targeting. The ultimate goal is to provide prediction of clinical outcome and treatment response of anti-cancer drugs. Different from single targeting in most research, we accomplished multiple targeting to obtain a molecular profile potentially representing tumor characteristics or to locate the heterogeneous population in one lesion. By conjugating different antibodies to gold nanorods corresponding to different peak absorption bands, multiple targeting and simultaneous detection with photoacoustic imaging can be achieved with laser irradiation at the respective peak optical absorption wavelength. Her2 and EGFR were chosen as our primary target molecules. The targeting complex was evaluated in two types of oral cancer cells, OECM1 and Cal27. The OECM1 cell line overexpresses Her2 but has low expression of EGFR, while Cal27 cell line expresses both antibodies. Also, the targeting efficacy to OECM1 can be further improved by using mixed nanoprobes. The cancer cells were induced on the back of the mice by subcutaneous injection. The captured images show that both cancer cells exhibit a higher photoacoustic response (maximum 3 dB) than control groups with specific targeting, thus demonstrating the feasibility of multiple selective targeting with bioconjugated gold nanorods. Images of multiple targeting with mixed nanoprobes of OECM1 cells also reveal further enhancement of targeting (4 dB). The results showed potential of in vivo photoacoustic molecular imaging, providing a better guidance for diagnosis and treatment of cancer.