Can intra-operative fluorescence play a significant role in hepatobiliary surgery?

A novel prostate cancer-specific fluorescent probe based on extracellular vesicles targeting STEAP1 applied in fluorescence guided surgery

Radical prostatectomy with pelvic lymph node dissection is the best treatment for intermediate- to high-risk localized prostate cancer (PCa). However, conventional white light surgery has difficulties in identifying tumor boundary and micrometastases intraoperatively. Fluorescence guided surgery (FGS) can solve the above difficulties, but lacks tumor-specific near-infrared fluorescent (NIRF) probes in PCa. STEAP1 was an ideal target in PCa treatment and imaging. Here, we constructed a PCa specific fluorescent probe based on extracellular vesicles targeting STEAP1 (AS-EVs) loaded with NIRF dye S0456 and evaluated its preclinical profiles. In vitro and in vivo studies both showed S0456@AS-EVs was safe and showed strong targeting ability to PCa in various mice xenograft models. S0456@AS-EVs could clear rapidly from blood (half-time of 4.29 h) and retain in the STEAP1 positive tumor tissues for more than 72 h with the highest tumor background ratio (TBR) of 3:1, which was superior to ICG, free S0456, ICG@Ctrl-EVs and S0456@Ctrl-EVs (p < 0.01). Finally, S0456@AS-EVs was applied in FGS on intramuscular model, and the tumors were resected under white light and fluorescence respectively. Compared with white light surgery, mice undergoing FGS had lower positive margin rate and better postoperative survival (p = 0.0342).

Detection of Hepatocellular Carcinoma in an Orthotopic Patient-Derived Xenograft with an Epithelial Cell Adhesion Molecule-Specific Peptide

Hepatocellular carcinoma (HCC) has emerged as a major contributor to the worldwide cancer burden. Improved methods are needed for early cancer detection and image-guided surgery. Peptides have small dimensions that can overcome delivery challenges to achieve high tumor concentrations and deep penetration. We used phage display methods to biopan against the extra-cellular domain of the purified EpCAM protein, and used IRDye800 as a near-infrared (NIR) fluorophore. The 12-mer sequence HPDMFTRTHSHN was identified, and specific binding to EpCAM was validated with HCC cells in vitro. A binding affinity of kd = 67 nM and onset of k = 0.136 min-1 (7.35 min) were determined. Serum stability was measured with a half-life of T1/2 = 2.6 h. NIR fluorescence images showed peak uptake in vivo by human HCC patient-derived xenograft (PDX) tumors at 1.5 h post-injection. Also, the peptide was able to bind to foci of local and distant metastases in liver and lung. Peptide biodistribution showed high uptake in tumor versus other organs. No signs of acute toxicity were detected during animal necropsy. Immunofluorescence staining of human liver showed specific binding to HCC compared with cirrhosis, adenoma, and normal specimens.

hHEPATO-Cy5, a Bimodal Tracer for Image-Guided Hepatobiliary Surgery

Liver cancer is a leading cause of cancer deaths worldwide. Surgical resection of superficial hepatic lesions is increasingly guided by the disrupted bile excretion of the fluorescent dye indocyanine green (ICG). To extend this approach to deeper lesions, a dedicated bimodal tracer that facilitates both fluorescence guidance and radioguidance was developed. Methods: A tracer comprising a methylated cyanine-5 (Cy5) fluorescent dye and a mercaptoacetyltriserine chelate (hHEPATO-Cy5) was synthesized and characterized. Cellular uptake and excretion were evaluated in hepatocyte cultures (2-dimensional culture and in vitro lesion model), using a fluorescent bile salt, MitoTracker dye, and methylated Cy5 as a control. After radiolabeling, the pharmacokinetics of 99mTc-hHEPATO-Cy5 were assessed in mice over 24 h (percentage injected dose and percentage injected dose per gram of tissue, SPECT/CT imaging and fluorescence imaging). The ability to provide real-time fluorescence guidance during robot-assisted hepatobiliary surgery was evaluated in a porcine model using ICG as a reference. Results: The unique molecular signature of hHEPATO-Cy5 promotes hepatobiliary excretion. In vitro studies on hepatocytes showed that where methylated Cy5 remained internalized, hHEPATO-Cy5 showed fast clearance (10 min) similar to that of fluorescent bile salt. In vivo use of 99mTc-hHEPATO-Cy5 in mice revealed liver accumulation and rapid biliary clearance. The effectiveness of bile clearance was best exemplified by the 2-orders-of-magnitude reduction in count rate for the gallbladder (P = 0.008) over time. During hepatobiliary surgery in a porcine model, hHEPATO-Cy5 enabled fluorescence-based lesion identification comparable to that of ICG. Conclusion: The bimodal 99mTc-hHEPATO-Cy5 provides an effective means to identify liver lesions. Uniquely, it helps overcome the shortcomings of fluorescence-only approaches by allowing for an extension to in-depth radioguidance.

Developments in the Use of Indocyanine Green (ICG) Fluorescence in Colorectal Surgery

Indocyanine Green (ICG) has significantly advanced minimally invasive surgery. It is widely recognized for its ability to visualize blood vessel patency in real-time across various surgical specialties. While its primary use in colorectal surgery is to evaluate anastomoses for leaks, numerous other applications have been documented in the literature. In this review, we aim to explore both established and emerging applications of ICG fluorescence in colorectal surgery, with the goal of improving patient outcomes. This includes preoperative tumor marking and the detection of metastatic disease. Some applications, such as lymphatic mapping, require further research to determine their impact on clinical practices. Conversely, others, like the intraoperative localizations of ureters, necessitate additional procedures and are not yet widely accepted by the surgical community. However, the development of alternative compounds could offer better solutions. Future research should focus on areas like quantitative ICG and protocol standardization in prospective multicenter studies.

Use of Near-Infrared Fluorescence Techniques in Minimally Invasive Surgery for Colorectal Liver Metastases

Colorectal liver metastases (CRLM) afflict a significant proportion of patients with colorectal cancer (CRC), ranging from 25% to 30% of patients throughout the course of the disease. In recent years, there has been a surge of interest in the application of near-infrared fluorescence (NIRF) imaging as an intraoperative imaging technique for liver surgery. The utilisation of NIRF-guided liver surgery, facilitated by the administration of fluorescent dye indocyanine green (ICG), has gained traction in numerous medical institutions worldwide. This innovative approach aims to enhance lesion differentiation and provide valuable guidance for surgical margins. The use of ICG, particularly in minimally invasive surgery, has the potential to improve lesion detection rates, increase the likelihood of achieving R0 resection, and enable anatomically guided resections. However, it is important to acknowledge the limitations of ICG, such as its low specificity. Consequently, there has been a growing demand for the development of tumour-specific fluorescent probes and the advancement of camera systems, which are expected to address these concerns and further refine the accuracy and reliability of intraoperative fluorescence imaging in liver surgery. While NIRF imaging has been extensively studied in patients with CRLM, it is worth noting that a significant proportion of published research has predominantly focused on the detection of hepatocellular carcinoma (HCC). In this study, we present a comprehensive literature review of the existing literature pertaining to intraoperative fluorescence imaging in minimally invasive surgery for CRLM. Moreover, our analysis places specific emphasis on the techniques employed in liver resection using ICG, with a focus on tumour detection in minimal invasive surgery (MIS). Additionally, we delve into recent developments in this field and offer insights into future perspectives for further advancements.

Fluorescent Conjugates Based on Prostate-Specific Membrane Antigen Ligands as an Effective Visualization Tool for Prostate Cancer

Fluorescent dyes are widely used in histological studies and in intraoperative imaging, including surgical treatment of prostate cancer (PC), which is one of the most common types of cancerous tumors among men today. Targeted delivery of fluorescent conjugates greatly improves diagnostic efficiency and allows for timely correct diagnosis. In the case of PC, the protein marker is a prostate-specific membrane antigen (PSMA). To date, a large number of diagnostic conjugates targeting PSMA have been created based on modified urea. The review focuses on the conjugates selectively binding to PSMA and answers the following questions: What fluorescent dyes are already in use in the field of PC diagnosis? What factors influence the structure-activity ratio of the final molecule? What features should be considered when selecting a fluorescent tag to create new diagnostic conjugates? And what could be suggested to further development in this field at the present time?

Multi-modal imaging for uptake of peptide ligand specific for CD44 by hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is rising steadily in incidence, and more effective methods are needed for early cancer detection and image-guided surgery.

METHODS

We used a structural model to optimize the peptide sequence. Specific binding was validated in vitro with knockdown, competition, and co-localization assays. Multi-modal imaging was performed to validate specific binding in vivo in orthotopically-implanted human xenograft tumors.

RESULTS

Binding properties of WKGWSYLWTQQA were characterized by an apparent dissociation constant of k_d = 43 nM, and an apparent association time constant of k = 0.26 min^-1. The target-to-background ratio was significantly higher for the target versus control for both modalities. Ex-vivo evaluation using human HCC specimens supported the ability of the peptide to distinguish HCC from other liver pathologies.

CONCLUSIONS

We have identified a peptide specific for CD44 with properties that are promising for clinical translation to image HCC in vivo.

Multi-Modal Imaging Probe for Glypican-3 Overexpressed in Orthotopic Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is rising steadily in incidence, and more effective methods are needed for early detection and image-guided surgery. Glypican-3 (GPC3) is a cell surface biomarker that is overexpressed in early-stage cancer but not in cirrhosis. An IRDye800-labeled 12-mer amino acid sequence was identified, and specific binding to GPC3 was validated in vitro and in orthotopically implanted HCC tumors in vivo. Over 4-fold greater binding affinity and 2-fold faster kinetics were measured by comparison with previous GPC3 peptides. Photoacoustic images showed peak tumor uptake at 1.5 h post-injection and clearance within ∼24 h. Laparoscopic and whole-body fluorescence images showed strong intensity from tumor versus adjacent liver with about a 2-fold increase. Immunofluorescence staining of human liver specimens demonstrated specific binding to HCC versus cirrhosis with 79% sensitivity and 79% specificity, and normal liver with 81% sensitivity and 84% specificity. The near-infrared peptide is promising for early HCC detection in clinical trials.

Photosensitizer-based multimodal PSMA-targeting ligands for intraoperative detection of prostate cancer

Incomplete resection of prostate cancer (PCa) occurs in 15%-50% of PCa patients. Disease recurrence negatively impacts oncological outcome. The use of radio-, fluorescent-, or photosensitizer-labeled ligands to target the prostate-specific membrane antigen (PSMA) has become a well-established method for the detection and treatment of PCa. Methods: Here, we developed and characterized multimodal [¹¹¹In]In-DOTA(GA)-IRDye700DX-PSMA ligands, varying in their molecular composition, for use in intraoperative radiodetection, fluorescence imaging and targeted photodynamic therapy of PCa lesions. PSMA-specificity of these ligands was determined in xenograft tumor models and on fresh human PCa biopsies. Results: Ligand structure optimization showed that addition of the photosensitizer (IRDye700DX) and additional negative charges significantly increased ligand uptake in PSMA-expressing tumors. Moreover, an ex vivo incubation study on human tumor biopsies confirmed the PSMA-specificity of these ligands on human samples, bridging the gap to the clinical situation. Conclusion: We developed a novel PSMA-targeting ligand, optimized for multimodal image-guided PCa surgery combined with targeted photodynamic therapy.

Targeted Nanobubbles Carrying Indocyanine Green for Ultrasound, Photoacoustic and Fluorescence Imaging of Prostate Cancer

Objective

To construct prostate-specific membrane antigen (PSMA)-targeting, indocyanine green (ICG)-loaded nanobubbles (NBs) for multimodal (ultrasound, photoacoustic and fluorescence) imaging of prostate cancer.

Methods

The mechanical oscillation method was used to prepare ICG-loaded photoacoustic NBs (ICG NBs). Then, PSMA-binding peptides were connected to the surface of ICG NBs using the biotin–avidin method to make targeted photoacoustic NBs, namely, PSMAP/ICG NBs. Their particle sizes, zeta potentials, and in vitro ultrasound, photoacoustic and fluorescence imaging were examined. Confocal laser scanning microscopy and flow cytometry were used to detect the binding ability of the PSMAP/ICG NBs to PSMA-positive LNCaP cells, C4-2 cells, and PSMA-negative PC-3 cells. The multimodal imaging effects of PSMAP/ICG NBs and ICG NBs were compared in nude mouse tumor xenografts.

Results

The particle size of the PSMAP/ICG NBs was approximately 457.7 nm, and the zeta potential was approximately −23.5 mV. Both confocal laser scanning microscopy and flow cytometry confirmed that the PSMAP/ICG NBs could specifically bind to both LNCaP and C4-2 cells, but they rarely bound to PC-3 cells. The ultrasound, photoacoustic and fluorescence imaging intensities of the PSMAP/ICG NBs in vitro positively correlated with their concentrations. The ultrasound and photoacoustic imaging effects of the PSMAP/ICG NBs in LNCaP and C4-2 tumor xenografts were significantly enhanced compared with those in PC-3 tumor xenografts, which were characterized by a significantly increased duration of ultrasound enhancement and heightened photoacoustic signal intensity (P < 0.05). Fluorescence imaging showed that PSMAP/ICG NBs could accumulate in LNCaP and C4-2 tumor xenografts for a relatively long period.

Conclusion

The targeted photoacoustic nanobubbles prepared in this study can specifically bind to PSMA-positive prostate cancer cells and have the ability to enhance ultrasound, photoacoustic and fluorescence imaging of PSMA-positive tumor xenografts. Photoacoustic imaging could visually display the intensity of the red photoacoustic signal in the tumor region, providing a more intuitive imaging modality for targeted molecular imaging. This study presents a potential multimodal contrast agent for the accurate diagnosis and assessment of prostate cancer.

PSMA-targeting agents for radio- and fluorescence-guided prostate cancer surgery

Despite recent improvements in imaging and therapy, prostate cancer (PCa) still causes substantial morbidity and mortality. In surgical treatment, incomplete resection of PCa and understaging of possible undetected metastases may lead to disease recurrence and consequently poor patient outcome. To increase the chance of accurate staging and subsequently complete removal of all cancerous tissue, prostate specific membrane antigen (PSMA) targeting agents may provide the surgeon an aid for the intraoperative detection and resection of PCa lesions. Two modalities suitable for this purpose are radionuclide detection, which allows sensitive intraoperative localization of tumor lesions with a gamma probe, and fluorescence imaging, allowing tumor visualization and delineation. Next to fluorescence, use of photosensitizers may enable intraoperative targeted photodynamic therapy to eradicate remaining tumor lesions. Since radiodetection and optical imaging techniques each have their own strengths and weaknesses, a combination of both modalities could be of additional value. Here, we provide an overview of recent preclinical and clinical advances in PSMA-targeted radio- and fluorescence-guided surgery of PCa.