A novel prostate cancer-specific fluorescent probe based on extracellular vesicles targeting STEAP1 applied in fluorescence guided surgery.

Radical prostatectomy with pelvic lymph node dissection is the best treatment for intermediate- to high-risk localized prostate cancer (PCa). However, conventional white light surgery has difficulties in identifying tumor boundary and micrometastases intraoperatively. Fluorescence guided surgery (FGS) can solve the above difficulties, but lacks tumor-specific near-infrared fluorescent (NIRF) probes in PCa. STEAP1 was an ideal target in PCa treatment and imaging. Here, we constructed a PCa specific fluorescent probe based on extracellular vesicles targeting STEAP1 (AS-EVs) loaded with NIRF dye S0456 and evaluated its preclinical profiles. In vitro and in vivo studies both showed S0456@AS-EVs was safe and showed strong targeting ability to PCa in various mice xenograft models. S0456@AS-EVs could clear rapidly from blood (half-time of 4.29 h) and retain in the STEAP1 positive tumor tissues for more than 72 h with the highest tumor background ratio (TBR) of 3:1, which was superior to ICG, free S0456, ICG@Ctrl-EVs and S0456@Ctrl-EVs (p < 0.01). Finally, S0456@AS-EVs was applied in FGS on intramuscular model, and the tumors were resected under white light and fluorescence respectively. Compared with white light surgery, mice undergoing FGS had lower positive margin rate and better postoperative survival (p = 0.0342).