Squaraine dye based prostate-specific membrane antigen probes for near-infrared fluorescence imaging of prostate cancer

Prostate cancer (PCa) is the most common cancer-related malignancy in older men worldwide, with a high mortality rate. To solve the problems of positive margins and other complications during radical prostatectomy, it is currently necessary to develop suitable optical imaging probes to distinguish tumor from normal tissue during surgery. Prostate-specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase II (GCP II) overexpressed in PCa. In this article, a new squaraine dye based probe (SQ-CN-PSMA) for PSMA has been developed, displaying suitable optical properties (λEM = 706 nm, Φ = 23%), ideal water solubility and high affinity (Ki = 0.34 nM). In vivo optical imaging in 22Rv1 xenografts in Balb/c nude mice demonstrated good visualization of PSMA-expressing tumors with higher TNR value (11.08 ± 1.59 for 24 h) at a low dosage (2 nmol). Overall, SQ-CN-PSMA holds great potential for imaging PSMA tumors and could be used in assisting surgeons performing prostatectomies for the treatment of PCa.