Targeted imaging of orthotopic prostate cancer by using clinical transformable photoacoustic molecular probe

BACKGROUND: To obtain high-yield histological samples by targeted prostate cancer (PCa) biopsy is the current trend compared with transrectal ultrasound (TRUS)-guided systematic histological biopsy, which is regarded as the gold standard for prostate cancer (PCa) diagnosis. In this paper, we present a targeted PCa imaging strategy using a real-time molecular photoacoustic imaging system integrated with a handheld US probe (PAI/US) and synthesized an integrin α(v)β(3) targeted probe based on ICG (cRGD–ICG). METHODS: To prepare cRGD–ICG, ICG-NHS was linked to cRGD through carboxyl-co-reaction. In vitro PA imaging ability of cRGD–ICG was tested. Orthotopic PCa-bearing rats were used as animal models. After injected with either cRGD–ICG or non-targeted probe, rats were implemented with PA imaging to confirm the specific accumulation of cRGD–ICG at tumor region. Moreover, pathological frozen slices were made to observe distribution of the probe in prostate tissue ex vivo. RESULTS: A small molecular PAI probe was synthesized and exhibited excellent targeted imaging ability in vitro. In vivo photoacoustic imaging was carried out after intravenous injection of cRGD-ICG in orthotopic PCa-bearing rats under the facilitation of the PAI/US system. Maximum molecular photoacoustic signals were observed in the tumor area in vivo after the probe injection, which showed 3.8-fold higher signal enhancement than that in the control group (P < 0.05). Significantly higher cRGD-ICG accumulation was observed under confocal microscopy in the tumor region than in normal prostate tissue. CONCLUSIONS: All our results showed that the comprehensive strategy provided a high-yield and reliable method for PCa diagnosis and targeted prostate biopsy, with great clinical translation potential.