聚多巴胺修饰的相变型对比剂的制备及体内外光声/超声显像

Preparation of polydopamine modified phase-shift contrast agents for enhanced photoacoustic/ultrasound imaging in vitro and in vivo

目的制备一种新型的聚多巴胺修饰的光声/超声双模态对比剂(PFP@PLGA@PDAs),探究其体内外光声、超声显影效果。方法①采用单乳化法一溶液氧化法合成聚多巴胺表面修饰的全氟正戊烷高分子纳米粒(PFP@PLGA@PDAs),检测PFP@PLGA@PDAs的基本性质;②以未修饰的相变型纳米粒(PFP@PLGAs)作为对照,应用琼脂糖模型测量纳米粒的体外光声和超声信号;③选取雌性BALB/c裸鼠(4~6周龄,体质量20g),构建裸鼠4T1乳腺癌动物模型,分为3组(PFP@PLGA@PDAs实验组,PFP@PLGAs对照组和PBS对照组,n=6),尾静脉注射对比剂后探究体内增强实体肿瘤的光声成像和超声成像的效果。结果@PFP@PLGA@PDAs悬液呈深褐色,纳米粒为球形的壳一核结构,粒径(209.40±36.15)nm,显微镜下见温度达43。C以上时发生液一气相变,CCK一8实验结果提示良好生物安全性。②体外光声成像显示,PFP@PLGA@PDAs的光声信号随浓度增加而明显增强(P<0.05),PFP@LGAs始终不显影;体外超声成像显示,经激光辐照后,PFP@PLGA@PDAs在基波和谐波模式下的回声信号均明显增强,不同辐照时长的谐波声强值间差异具有统计学意义(P<0.05),PFP@PLGAs的回声信号无明显变化。③体内光声成像显示,尾静脉注射PFP@PLGA@PDAs的荷瘤鼠的肿瘤部位在注射前和注射后1、4、24h的光声信号值分别为(0.12±0.03)、(0.22±0.04)、(0.67±0.08)、(0.37±0.06),差异有统计学意义(P<0.05),PFP@PLGAs和PBS组荷瘤鼠的肿瘤部位始终未见明显光声信号。体内超声成像显示,在激光辐照前,3组荷瘤鼠的肿瘤部位表现相似的超声回声信号,激光辐照后PFP@PLGA@PDAs组肿瘤的二维和造影图像均显示明显增多的点状高信号,而PFP@PLGAs和PBS组在辐照前后均未见明显回声信号改变。结论成功制备出一种聚多巴胺修饰的相变型对比剂,其具有作为一种分子探针实现肿瘤的体内外光声/超声双模态成像的潜力。

Objective To prepare a new polydopamine modified phase-shift dual-mode contrast agent(PFP@ PLGA@ PDAs) and investigate its enhanced photoacoustic and ultrasound imaging in vitro and in vivo.Methods①After PFP @ PLGA @ PDAs were prepared by sonication process and solution oxidation,the physicochemical properties were later characterized.② With unmodified PFP@ PLGAs as control,agar-based phantoms were used to assess photoacoustic and ultrasound signals of these nanoparticles in vitro.③ Eighteen female nude mice(4 ~ 6 weeks old,weighting about 20 g) were employed to establish a murine 4 T1 breast xenograft model,and were then randomly divided into PFP@ PLGA@ PDAs group,PFP@ PLGAs group and PBS group,with 6 mice in each group. The effects of above agents(tail vein injection) were observed for photoacoustic imaging and ultrasound imaging in vivo. Results① The prepared PFP @ PLGA @ PDAs solution were dark brown in color,and showed a well-defined core-shell structured spherical morphology. The mean diameter of PFP@ PLGA@ PDAs was 209. 40 ± 36. 15 nm. Vaporization was triggered at 43 ℃. CCK-8 assay suggested good biological safety.②In vitro photoacoustic imaging experiments showed that the photoacoustic signals of PFP @ PLGA @ PDAs solution were raised significantly with the increase of concentration,while PFP @ PLGAs displayed nearly no such signals. For enhanced ultrasound imaging experiments in vivo,PFP@ PLGA@ PDAs solution significantly increased the intensity of echo in B-mode and contrast-enhanced ultrasonography after laser irradiation(P < 0. 05),with obvious differences in the intensity of harmonic signals under different durations of irradiation(P < 0. 05). No such changes were seen when PFP@ PLGAs solution was employed.③In vivo photoacoustic study showed that,before and in 1,4 and 24 h after the injection of PFP@ PLGA@ PDAs solution,the intensity of photoacoustic signals was 0. 12 ± 0. 03,0. 22 ± 0. 04,0. 67 ± 0. 08 and 0. 37 ± 0. 06,respectively(P < 0. 05). No photoacoustic signal was observed in the tumors of the mice injected with PBS and PFP@ PLGA solution. In in vitro ultrasonic study,similar echo signals were observed in the tumors of the 3 groups of mice before laser irradiation,but significantly enhanced high-intensity signals were only found in 2-D and contrast images in the mice from the PFP@ PLGA@ PDAs group after laser irradiation,while,no such changes of echo intensity were found in the 2 control groups. Conclusion Phase-shift contrast agent modified by dopamine is successfully prepared,and it,as a molecular probe,presents the potential of photoacoustic/ultrasound dual-mode imaging.