Macrophage-Targeted Indocyanine Green-Neomannosyl Human Serum Albumin for Intraoperative Sentinel Lymph Node Mapping in Porcine Esophagus

Detection of metastatic lymph node and sentinel lymph node mapping ​using mannose receptor targeting in in vivo mouse footpad tumor models and rabbit uterine cancer models

BACKGROUND

This study aimed to evaluate the effectiveness of neo-mannosyl human serum albumin-indocyanine green (MSA-ICG) for detecting metastatic lymph node (LN) and mapping sentinel lymph node (SLN) using mouse footpad uterine tumor models. Additionally, the authors assessed the feasibility of MSA-ICG in SLN mapping in rabbit uterine cancer models.

MATERIALS AND METHODS

The authors compared the LN targeting ability of MSA-ICG with ICG. Six mouse footpad tumor models and two normal mice were each assigned to MSA-ICG and ICG, respectively. After the assigned tracers were injected, fluorescence images were taken, and the authors compared the signal-to-background ratio (SBR) of the tracers. A SLN biopsy was performed to confirm LN metastasis status and CD206 expression level. Finally, an intraoperative SLN biopsy was performed in rabbit uterine cancer models using MSA-ICG.

RESULTS

The authors detected 14 groin LNs out of 16 in the MSA-ICG and ICG groups. The SBR of the MSA-ICG group was significantly higher than that of the ICG group. The metastatic LN subgroup of MSA-ICG showed a significantly higher SBR than that of ICG. CD206 was expressed at a high level in metastatic LN, and the signal intensity difference increased as the CD206 expression level increased. SLN mapping was successfully performed in two of the three rabbit uterine cancer models.

CONCLUSIONS

MSA-ICG was able to distinguish metastatic LN for an extended period due to its specific tumor-associated macrophage-targeting property. Therefore, it may be a more distinguishable tracer for identifying metastatic LNs and SLNs during uterine cancer surgery. Further research is needed to confirm these results.

Indocyanine green dye and its application in gastrointestinal surgery: The future is bright green

Indocyanine green (ICG) is a water-soluble fluorescent dye that is minimally toxic and widely used in gastrointestinal surgery. ICG facilitates anatomical identification of structures (e.g., ureters), assessment of lymph nodes, biliary mapping, organ perfusion and anastomosis assessment, and aids in determining the adequacy of oncological margins. In addition, ICG can be conjugated to artificially created antibodies for tumour markers, such as carcinoembryonic antigen for colorectal, breast, lung, and gastric cancer, prostate-specific antigen for prostate cancer, and cancer antigen 125 for ovarian cancer. Although ICG has shown promising results, the optimization of patient factors, dye factors, equipment, and the method of assessing fluorescence intensity could further enhance its utility. This review summarizes the clinical application of ICG in gastrointestinal surgery and discusses the emergence of novel dyes such as ZW-800 and VM678 that have demonstrated appropriate pharmacokinetic properties and improved target-to-background ratios in animal studies. With the emergence of robotic technology and the increasing reporting of ICG utility, a comprehensive review of clinical application of ICG in gastrointestinal surgery is timely and this review serves that aim.

Fluorescence Imaging-Guided Identification of Thymic Masses Using Low-Dose Indocyanine Green

BACKGROUND

Indocyanine green (ICG) fluorescence imaging has been used to detect many types of tumors during surgery; however, there are few studies on thymic masses and the dose and time of ICG injection have not been optimized.

OBJECTIVE

We aimed to evaluate the optimal ICG injection dose and timing for detecting thymic masses during surgery.

METHOD

Forty-nine consecutive patients diagnosed with thymic masses on preoperative computed tomography (CT) and scheduled to undergo thymic cystectomy or thymectomy were included. Patients were administered 1, 2, or 5 mg/kg of ICG at different times. Thymic masses were observed during and after surgery using a near-infrared fluorescence imaging system, and the fluorescence signal tumor-to-normal ratio (TNR) was analyzed.

RESULTS

Among the 49 patients, 14 patients with thymic cysts showed negative fluorescence signals, 33 patients with thymoma or thymic carcinoma showed positive fluorescence signals, and 2 patients showed insufficient fluorescence signals. The diagnosis of thymic masses based on CT was correct in 32 (65%) of 49 cases; however, the differential diagnosis of thymic masses based on NIR signals was correct in 47 of 49 cases (96%), including 14 cases of thymic cysts (100%) and 33 cases of thymomas or thymic carcinomas (94%). In addition, TNR was not affected by the time or dose of ICG injection, histological type, stage, or tumor size.

CONCLUSIONS

Low-dose intravenous injection of ICG at flexible time can detect thymic tumors. In addition, thymic cysts can be distinguished from thymomas or thymic carcinomas during surgery by the absence of ICG fluorescence signals.

Design and Testing of Augmented Reality-Based Fluorescence Imaging Goggle for Intraoperative Imaging-Guided Surgery

The different pathways between the position of a near-infrared camera and the user's eye limit the use of existing near-infrared fluorescence imaging systems for tumor margin assessments. By utilizing an optical system that precisely matches the near-infrared fluorescence image and the optical path of visible light, we developed an augmented reality (AR)-based fluorescence imaging system that provides users with a fluorescence image that matches the real-field, without requiring any additional algorithms. Commercial smart glasses, dichroic beam splitters, mirrors, and custom near-infrared cameras were employed to develop the proposed system, and each mount was designed and utilized. After its performance was assessed in the laboratory, preclinical experiments involving tumor detection and lung lobectomy in mice and rabbits by using indocyanine green (ICG) were conducted. The results showed that the proposed system provided a stable image of fluorescence that matched the actual site. In addition, preclinical experiments confirmed that the proposed system could be used to detect tumors using ICG and evaluate lung lobectomies. The AR-based intraoperative smart goggle system could detect fluorescence images for tumor margin assessments in animal models, without disrupting the surgical workflow in an operating room. Additionally, it was confirmed that, even when the system itself was distorted when worn, the fluorescence image consistently matched the actual site.

Fluorescence-guided surgery of the esophagus

The use of indocyanine green (ICG) fluorescence near-infrared (NIR) imaging during gastrointestinal surgery has surged in recent years. Its use in esophageal surgery is actively being studied both in the clinical setting and in the lab. NIR imaging has several important applications in esophageal surgery including assessing perfusion of the gastrointestinal-esophageal anastomosis, lymphatic drainage and tracheal blood flow after mediastinal dissection. This is a review of the modern literature summarizing the current knowledge on fluorescence-guided surgery of the esophagus.

Preparation of a multi-modal agent for sentinel lymph node mapping using Evans blue and 99mTc-labeled mannosylated human serum albumin conjugate

INTRODUCTION

The identification of sentinel lymph nodes (SLNs) is important in deciding the resection range during surgery. ^99mTc-labeled mannosylated human serum albumin ([^99mTc]Tc-MSA) is a radiopharmaceutical developed for SLN detection by targeting macrophages. Evans blue (EB) is a blue dye binding strongly to albumin and has been used for SLN detection. [^99mTc]Tc-MSA-EB conjugate was prepared as a multi-modal imaging agent and tested its performance by visual investigation, fluorescence imaging and SPECT/CT for SLN mapping in mice.

METHODS

EB was mixed with various concentration of MSA to prepare MSA-EB conjugates. The binding efficiencies were determined using thin-layer chromatography. The UV-VIS spectra and molar extinction coefficient of the conjugate were obtained. The fluorescence was monitored at the excitation wavelength range 420-780 nm and the emission wavelength range 520-845 nm. The [^99mTc]Tc-MSA-EB conjugate and EB were injected into the footpads of normal BALB/c mice to check the lymph node (LN) uptakes. The visible, fluorescence, and SPECT/CT images were obtained after injection.

RESULTS

The conjugation of EB with MSA increased by time and was saturated within 10 min. The molar extinction coefficient of the conjugate was 99,259.3/M/cm at 620 nm. The uptake of conjugate into the popliteal LN after injection into the footpads of mice was investigated visually and fluorescence imaging. SPECT/CT images showed that the standardized uptake values of [^99mTc]Tc-MSA-EB conjugate in popliteal LN were about 4 times higher than in sciatic LN at all timepoints. It was confirmed by investigating resected LN that the blue color, fluorescence, and radioactivity of the [^99mTc]Tc-MSA-EB conjugate were retained only on the LN and did not spread to adjoining tissues.

CONCLUSION

[^99mTc]Tc-MSA-EB conjugate has a great potential as a multi-modal SLN mapping agent which could be detected by visual investigation, fluorescence imaging, and SPECT/CT.

Naphthol Blue Black and 99mTc-Labeled Mannosylated Human Serum Albumin (99mTc-MSA) Conjugate as a Multimodal Lymph Node Mapping Nanocarrier

^99mTc-labeled mannosylated human serum albumin (MSA) has been reported as a sentinel lymph node (SLN)-imaging agent by binding to macrophages in the LNs. By conjugating it with blue dye, we developed a new multimodal radio-nanocarrier by visual investigation, fluorescence imaging, and single photon emission computed tomography (SPECT)/computed tomography (CT). Binding affinities of seven blue dyes to MSA were tested. According to the spectroscopic study and visual inspection of MSA-bound dyes, naphthol blue black (NBB) was selected as the best candidate of multimodal agent. Thus, ^99mTc-MSA-NBB conjugate was prepared and further investigated using mice. After footpad injection, it showed high popliteal LN accumulation at 1 h. SPECT/CT also showed high popliteal as well as inguinal LN uptakes at 10 min that sustained until 2 h. In conclusion, we prepared a multimodal SLN imaging radio-nanocarrier, ^99mTc-MSA-NBB conjugate, and confirmed its excellency as a multimodal probe for SLN mapping.

Fluorescent image-based evaluation of gastric conduit perfusion in a preclinical ischemia model

Background

This study evaluated near-infrared (NIR) fluorescent images to assess gastric conduit perfusion after an esophagectomy in a porcine model of gastric conduit ischemia. The time necessary to acquire a sufficient fluorescent signal to confirm ischemia in the gastric conduit after peripheral or central venous injection of indocyanine green (ICG) was also investigated.

Methods

A reversible gastric conduit ischemic pig model was established through ligation and release of the right gastroepiploic artery (RGEA, n=10). The esophageal reconstruction was performed to create an esophagogastric anastomosis. After ligation of the RGEA, ICG was injected into an ear vein (n=6) or the inferior vena cava (n=4). Under fluorescent imaging system guidance, the fluorescent signal-to-background ratio (SBR) in the gastric conduit or esophagus was measured during the entire procedure. We estimated the time necessary to acquire fluorescent signals in the gastric conduit using two different injection routes.

Results

When the RGEA was ligated, the SBR in the esophagus was significantly higher than that in the gastric conduit (P=0.02), and the SBR in the gastric conduit recovered within 180 s after release of the ligation. The time to acquire a fluorescent signal was faster with a central route than with a peripheral route (P=0.04).

Conclusions

We successfully created an ischemic animal model of the gastric conduit. Using this animal model, we evaluated the sensitivity and applicability of the fluorescent imaging system for observation and identification of ischemic areas during an esophagectomy.

An opportunistic route to success: Towards a change of paradigm to fully exploit the potential of cell-penetrating peptides

About 25years ago it was demonstrated that certain peptides possess the ability to cross the plasma membrane. This led to the development of cell-penetrating peptides (CPPs) as vectors to mediate the cellular entry of (macro-)molecules that do not show cell entry by themselves. Nonetheless, in spite of an early bloom of promising pre-clinical studies, not a single CPP-based drug has been approved, yet. It is a paradigm in CPP research that the peptides are taken up by virtually all cells. In exploratory research and early preclinical development, this assumption guides the choice of the therapeutic target. However, while this indiscriminatory uptake may be the case for tissue culture experiments, in an organism this is clearly not the case. Biodistribution analyses demonstrate that CPPs only target a very limited number of cells and many tissues are hardly reached at all. Here, we review biodistribution analyses of CPPs and CPP-based drug delivery systems. Based on this analysis we propose a paradigm change towards a more opportunistic approach in CPP research. The application of CPPs should focus on those pathophysiologies for which the relevant target cells have been shown to be reached in vivo.