Diagnosis of prostate cancer using anti-PSMA aptamer A10-3.2-oriented lipid nanobubbles

Abstract: In this study, the lipid targeted nanobubble carrying the A10-3.2 aptamer against prostate specific membrane antigen was fabricated, and its effect in the ultrasound imaging of prostate cancer was investigated. Materials including 2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphatidic acid, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol, carboxyl-modified 1,2-distearoyl-sn-glycero-3-phosphoethanolamine, and polyethyleneglycol-2000 were for mechanical oscillation, and nanobubbles were obtained through the centrifugal flotation method. After mice were injected with nanobubbles, abdominal color Doppler blood flow imaging significantly improved. Through left ventricular perfusion with normal saline to empty the circulating nanobubbles, nanobubbles still existed in tumor tissue sections, which demonstrated that nanobubbles could enter tissue spaces via the permeability and retention effect. Fluorinated A10-3.2 aptamers obtained by chemical synthesis had good specificity for PSMA-positive cells, and were linked with carboxyl-modified 1,2-distearoyl-sn-glycero-3-phosphoethanolamine lipid molecules from the outer shell of nanobubbles via amide reaction to construct targeted nanobubbles. Gel electrophoresis and immunofluorescence confirmed that targeted nanobubbles were fabricated successfully. Next, targeted nanobubbles could bind with PSMA-positive cells (C4-2 cells), while not with PSMA-negative cells (PC-3 cells), using in vitro binding experiments and flow cytometry at the cellular level. Finally, C4-2 and PC-3 xenografts in mice were used to observe changes in parameters of targeted and non-targeted nanobubbles in the contrast-enhanced ultrasound mode, and the distribution of Cy5.5-labeled targeted nanobubbles in fluorescent imaging of live small animals. Comparison of ultrasound indicators between targeted and non-targeted nanobubbles in C4-2 xenografts showed that they had similar peak times ( P >0.05), while the peak intensity, half time of peak intensity, and area under the curve of ½ peak intensity were significantly different ( P <0.05). In PC-3 xenografts, there were no differences in these four indicators. Fluorescent imaging indicated that targeted nanobubbles had an aggregation ability in C4-2 xenograft tumors. In conclusion, targeted nanobubbles carrying the anti-PSMA A10-3.2 aptamer have a targeted imaging effect in prostate cancer. Keywords: molecular imaging, contrast-enhanced ultrasound, aptamer, prostate specific membrane antigen, targeted imaging