Poly(Lactide-Co-Glycolide) Ultrasonographic Microbubbles Carrying Sudan Black for Preoperative and Intraoperative Localization of Lymph Nodes

Current strategies for lymph node (LN) examination have limitations. A novel imaging agent, poly(lactide-co-glycolide) (PLGA) ultrasonographic microbubbles carrying Sudan black B (SB) (PLGA-SB) microbubbles) has been developed. Results have shown that the SB-PLGA microbubbles could be a suitable imaging agent for preoperative and intraoperative localization of LNs as well as for ultrasonographically guided core needle biopsy of LNs.Lymph node (LN) examination plays a critical role in the staging and treatment of several kinds of cancer such as lesions of the breast. However current strategies have limitations. This study aimed to develop a novel imaging agent, a polymeric ultrasonographic contrast agent carrying Sudan black (SB), for ultrasonographic imaging of the regional LNs before surgery and to directly localize the LNs during surgery. The poly(lactide-co-glycolide) (PLGA) ultrasonographic microbubbles carrying Sudan black B (SB) (SB-PLGA microbubbles) were prepared by the double emulsion method. The SB-PLGA microbubbles had a diameter of 1.5 +/- 0.5 mu m and the SB encapsulation efficiency was (86.2 +/- 1.56%). Results from MTT assays suggested that these bubbles have little cytotoxicity to mouse macrophages after incubation. Confocal laser scanning microscopy showed that the PLGA microbubbles carrying the fluorescent dye rhodamine 6G were taken up by macrophages after 2-hour incubation. In addition, these SB-PLGA microbubbles were able to enhance ultrasonographic contrast of 12 popliteal LNs of 6 rabbits. Furthermore, the LNs were easily identifiable by the naked eye during surgery because of the blue color of the SB-PLGA microbubbles inside the LNs. By cryosectioning and hematoxylin and eosin (H&E) staining of LN tissue, our results showed that these SB-PLGA microbubbles were internalized inside the macrophages of the LNs. To conclude, the SB-PLGA microbubbles could be a suitable imaging agent for preoperative and intraoperative localization of LNs as well as for a preoperative ultrasonographically guided core needle biopsy of suspicious sentinel lymph nodes (SLNs) in cancer patients, hence enhancing treatment outcome.

淋巴结（LN）检查的现行策略存在局限性。一种新型显像剂——携带苏丹黑B（SB）的聚乳酸 - 羟基乙酸共聚物（PLGA）超声微泡（PLGA - SB微泡）已被研发出来。结果表明，SB - PLGA微泡可作为一种合适的显像剂，用于淋巴结的术前和术中定位，以及在超声引导下对淋巴结进行粗针穿刺活检。 淋巴结检查在多种癌症（如乳腺病变）的分期和治疗中起着关键作用。然而，现行策略存在局限性。本研究旨在研发一种新型显像剂，一种携带苏丹黑（SB）的聚合物超声造影剂，用于手术前对区域淋巴结进行超声成像，并在手术中直接对淋巴结进行定位。通过复乳化法制备了携带苏丹黑B（SB）的聚乳酸 - 羟基乙酸共聚物（PLGA）超声微泡（SB - PLGA微泡）。SB - PLGA微泡的直径为1.5 ± 0.5微米，SB的包封率为（86.2 ± 1.56%）。MTT检测结果表明，这些微泡在孵育后对小鼠巨噬细胞的细胞毒性很小。共聚焦激光扫描显微镜显示，携带荧光染料罗丹明6G的PLGA微泡在孵育2小时后被巨噬细胞摄取。此外，这些SB - PLGA微泡能够增强6只兔子的12个腘淋巴结的超声造影效果。而且，由于淋巴结内SB - PLGA微泡呈蓝色，在手术中肉眼很容易识别淋巴结。通过对淋巴结组织进行冷冻切片以及苏木精 - 伊红（H&E）染色，我们的结果表明这些SB - PLGA微泡被内化到淋巴结的巨噬细胞内。总之，SB - PLGA微泡可作为一种合适的显像剂，用于癌症患者淋巴结的术前和术中定位，以及对可疑前哨淋巴结（SLNs）进行术前超声引导下的粗针穿刺活检，从而提高治疗效果。