The second near-infrared (NIR-II) window (1000~1350 nm) is a new “transparent” window for biomedical imaging in deep-tissue, since the light absorption and scattering are significantly reduced. However, only limited types of materials can achieve absorption in the NIR-II window, and the majority is inorganic materials. In addition, conventional NIR-II absorbers can only achieve absorption of certain frequencies of NIR-II light, but not effective for the entire NIR-II region. We will present a thienoisoindigo (TII) based semiconducting polymer nanoparticle (SPN) with strong absorption in 1000 ~ 1350 nm for photoacoustic imaging (PAI) in the NIR-II window, where background signals from endogenous contrast agents, including blood and lipid, are at the local minima. An imaging depth of more than 5 cm at 1064 nm excitation has been achieved in chicken breast tissue, with a contrast agent concentration as low as 40 µg/mL. The TSPNs under the skin or in tumor were clearly visualized at 1100 nm and 1300 nm, with negligible interference from tissue background. In vivo PAI showed that compared to the images of the mouse tumor without TSPNs, the signal was enhanced ≈7.0-fold at 1100 nm and ≈13.3-fold at 1300 nm. A prostate-specific membrane antigen (PSMA) targeting ligand (DUPA) was further conjugated to the SPN (SPN-DUPA) for targeted PAI of prostate cancer. PSMA over-expresses on the most prostate cancer cell surface and the expression level increases with the aggressiveness of the cancer. Our preliminary data show that the LNCaP cell line (PSMA-positive) has specific uptake of SPN-DUPA, while PC-3 cell line (PSMA-negative) does not. This demonstrates that TSPN-DUPA can specifically label the aggressive prostate cancer tumor for imaging and diagnosis. The targeted PAI with TSPN-DUPA is a promising new tool for the sensitive and specific detection of aggressive prostate cancer in the early stage, which is challenging with the current clinical diagnosis methods.

Semiconducting polymer nanoparticles for photoacoustic imaging in the second near-infrared window

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.