The Evolution of Fluorescence-Guided Surgery

A multi-modal embolic gel system for long-term fluorescence imaging and photothermal therapy

Gel embolic agents are increasingly recognized for their versatility in minimally invasive vascular interventions. However, their application in real-time imaging, post-operative monitoring, and thermal treatment remains underexplored. In this study, we present a novel transcatheter injectable nanoclay-alginate (NCA) gel embolic agent integrated with indocyanine green (ICG) for dual fluorescence imaging and thermal ablation. The NCA/ICG embolic gel exhibits excellent shear-thinning properties, transcatheter injectability, and mechanical stability. Furthermore, the mechanism to enhance fluorescence for real-time imaging enhancement and extended post-operative monitoring was discussed. A 28-day fluorescence persistence shows the NCA/ICG gel's long-lasting fluorescent signal, which was significantly stronger and longer compared to current clinically used ICG aqueous solution. Furthermore, the gel can effectively convert near-infrared (NIR) laser energy into heat for potential photothermal therapy. The biocompatibility and enhanced antibacterial properties further highlight the potential clinical benefits of this embolic agent as a multifunctional agent for vascular embolization.

Ultrasound-Assisted Blood-Brain Barrier Opening Monitoring by Photoacoustic and Fluorescence Imaging Using Indocyanine Green

OBJECTIVE

The blood-brain barrier (BBB) is a selectively permeable membrane that restricts drug delivery to the central nervous system. Focused ultrasound (FUS) combined with microbubbles (MBs) is a promising technique to transiently open the BBB, enabling therapeutic delivery. However, real-time monitoring of BBB permeability changes remains challenging. This study investigated the use of indocyanine green (ICG) as a bi-modal contrast agent for photoacoustic and fluorescence imaging to assess BBB opening and closure dynamics.

METHODS

BALB/c mice underwent FUS-mediated BBB opening with different doses of MBs and ICG administration. Photoacoustic and fluorescence imaging were performed at various time points post-FUS to evaluate ICG extravasation dynamics. Magnetic resonance imaging (MRI) with gadolinium contrast was used as the gold standard for BBB permeability assessment. The effect of MB dose and injection timing on BBB closure kinetics was analyzed.

RESULTS

Photoacoustic imaging provided reliable BBB monitoring within the first hour post-FUS, whereas fluorescence imaging was more effective at detecting ICG extravasation at 24 h. A strong correlation was observed between fluorescence intensity and MRI-based contrast enhancement, confirming BBB opening dynamics. BBB closure followed an exponential decay model, with a half-closure time of approximately 81 min. The degree of BBB opening was proportional to the MB dose administered.

CONCLUSION

ICG-based photoacoustic and fluorescence imaging provide a non-invasive and cost-effective alternative to MRI for monitoring FUS-induced BBB opening. These techniques offer complementary temporal windows for assessment, improving the precision of BBB permeability evaluation in preclinical and potentially clinical applications.

UV-Cross-Linked DNA Nanomaterials Enable Robust Nanopatterning of Folate Ligands for Enhanced Cellular Uptake

The arrangement of ligands on a nanomaterial scaffold is a powerful approach to enhance targeted cellular delivery. However, nanomaterial-mediated delivery often employs imprecise ligand conjugation, limiting the exploration of optimal ligand density and spatial organization. To address these challenges, we developed DNA nanomaterials with precisely spaced folate ligands and rigidified them via a postassembly UV-based thymine cross-linking. These materials exhibit exceptional nuclease stability and maintain structural integrity both under biologically relevant conditions and during internalization into live HeLa cells. We used these nanomaterials as scaffolds for folate patterning and identified optimal modes of folate presentation for cellular uptake. Each step of the uptake process was probed, revealing the synergistic effects of structural stabilization and precise ligand patterning on the uptake mechanism, intracellular retention, and export dynamics. We then used our nanopatterned nanomaterials as delivery vectors for a gene-silencing nucleic acid payload. By integrating optimized ligand presentation and structural immobilization, we successfully achieved targeted gene silencing in folate receptor alpha-expressing cancer cells. This work showcases the effect that DNA nanostructure fidelity and rigidity have on the presentation of ligand moieties. It introduces UV cross-linking as a critical tool for structural stabilization of DNA nanomaterials, enabling applications in therapeutic delivery, diagnostics, and nanoscale cell surface engineering. In addition, this study reveals spatial principles of folate nanopatterning to enhance future targeted delivery systems with precision, stability, and biocompatibility.

Engineering Bacterial Secretion Systems for Enhanced Tumor Imaging and Surgical Guidance

Current imaging techniques suffer from a lack of specificity and resolution, leading to inaccurate tumor imaging and limited applicability of targeted contrast agents, as they require cancer-specific development. The need for enhanced contrast through improved tumor-to-background ratio (TBR) and the toxicity from repeated injections due to fading fluorescent signals further complicate the issue. Additionally, challenges in visualizing the entire 3D tumor with surface-stained contrast agents highlight the demand for advanced imaging solutions for more precise surgical guidance. A novel approach is proposed utilizing Streptavidin Associated Salmonella (SAS) as a contrast agent for image-guided surgeries. SAS selectively proliferates in cancerous tissues and secretes streptavidin upon induction, enabling the binding of subsequently injected biotin-conjugated fluorescent dyes. This approach enhances tumor visualization with a TBR of up to 15.3, far surpassing conventional agents (TBR ∼ 2), while enabling prolonged 3-day imaging, deep tumor penetration, and precise invasive margin delineation with a single contrast agent injection. Furthermore, biosafety evaluations confirmed efficient bacterial clearance, absence of systemic toxicity, and stable physiological responses, supporting its potential for safe clinical translation. This innovative method offers substantial improvements over existing fluorescent contrast agents and holds promise for both diagnostic and therapeutic applications in cancer surgery.

Lipoprotein-inspired in situ activatable photo-theranostic nitrobenzoselenadiazole-cholesterol for overcoming glioblastoma

Photo-theranostic materials are designed for both diagnostic imaging and therapeutic applications under specific light sources, particularly in translational medicine. While various photo-theranostic materials have been developed for disease treatment, their cooperative effects on biologically abundant species, such as proteins, have rarely been studied in terms of biological activity. In this work, we disclose a photo-theranostic agent (named NBSD-Chol) based on nitrobenzoselenadiazole (NBSD) and cholesterol (Chol), which is activatable in situ through lipoprotein hybridization. NBSD-Chol demonstrates outstanding potential for cancer imaging and photodynamic therapy (PDT) due to its unique properties, including (i) tumor targeting after oral uptake, (ii) tumor visualization under light irradiation for image-guided surgery, (iii) superior PDT effects, and (iv) downgrading hazard ratios (HR) related to clinically critical proteins. Overall, this work contributes to advancing translational medicine by developing innovative treatments for cancer using visible light, ushering in a new era of intraoperative technology and photodynamic fluorescence-guided surgical agents.

Novel Near Infrared Dyes Targeting Carbonic Anhydrase IX for Fluorescence Imaging Applications

OBJECTIVES

Fluorescence tumor-targeted imaging is a sensitive technique that may assist surgeons to remove residual cancer tissue during resection. Carbonic anhydrase IX (CAIX) is a tumor-associated cell-surface glycoprotein, upregulated in hypoxic environments, and a suitable biomarker to develop targeted dyes for fluorescence-guided surgery. This study describes design, synthesis, in vitro and in vivo assessment of novel CAIX-targeting fluorescent probes based on the well-known drug acetazolamide, addressing the contribution of both targeting moiety and fluorophore structure on imaging efficacy.

MATERIALS AND METHODS

All the CAIX-targeting heptamethine cyanines synthesized and described in the present work were characterized in terms of their optical properties in different media. The affinity to human serum albumin was evaluated by UV-VIS spectrophotometry. The affinity to the CA catalytic site was determined on a recombinant bovine CAII enzyme (bCAII), with a fluorescent-based assay. Human colon adenocarcinoma HT-29 cells, highly expressing CAIX, were used for the in vitro characterization, including cell binding, uptake and competition assays, by flow cytometry. Finally, the in vivo tumor targeting efficacy of a selected group of probes was assessed by Optical Imaging in a mouse subcutaneous tumor from HT-29 cells, characterized by both expression of CAIX and a hypoxic tumor microenvironment.

RESULTS

First, a family of CAIX-targeting probes was prepared by functionalizing a novel glucamine-bearing heptamethine cyanine (Dye1) with a modified acetazolamide moiety, whose acetyl group was replaced with i) aminooctanoic acid C8, ii) phenylalanine, iii) amino-PEG2-acid and iv) the longer linker 4a, or 2 commercially available benzenesulfonamides. From the in vitro screening of this first group of compounds, the C8-AZA targeting moiety was selected due to its highest affinity. Indeed, Dye1-C8-AZA exhibited the lowest KD values for both bCAII (6.1 ± 1.6 nM) and CAIX-expressing HT-29 cells (58 ± 9 nM), even lower than HypoxyFluor-1 (HF-1), a CAIX-targeted dye already reported in the literature. Then, other heptamethine cyanines (Dye2-Dye5, linear or cyclic, with different substituents on the indolenines and different conjugation position of the targeting vector) were functionalized with C8-AZA and fully characterized both in vitro and in vivo, to evaluate the combinatory effect of vector and fluorophore on the performance of the resulting probes. The different chemical features of the cyanines influenced the optical properties, solubility, binding with albumin, biodistribution, and imaging efficacy of the probes, while leaving unaffected the high affinity to the target. When tested in vivo for the visualization of CAIX-expressing HT-29 tumors, all C8-AZA probes showed high and specific tumor accumulation, often superior to HF-1.

CONCLUSIONS

Several CAIX-targeting probes were synthesized to test the combinatory effect of different molecular vectors and dyes on the biological properties. All probes containing the C8-AZA targeting moiety displayed higher affinity and specificity to the target, while imaging efficacy in vivo was strongly influenced also by the structure of the labelling dye. All probes, and among them especially Dye1-C8-AZA, displayed efficient in vivo tumor accumulation. These results support further studies toward clinical testing of CAIX as suitable target for tumor fluorescence imaging and pave the way for future clinical applications.

Design, Synthesis, and Evaluation of Boron Dipyrromethene-Based Fluorescent Probes Targeting BRAF for Melanoma Diagnosis

Fluorescent dyes are widely applied in clinical diagnosis, detection, and treatment of diseases. Several image probes such as ICG, MB, and 5-ALA have been approved by FDA. However, the limited tumor-targeting capability of these dyes hinders their effectiveness in oncological imaging. Currently, various ligand-based targeting probes have been developed to minimize nonspecific background emission. BRAF, especially BRAF V600E, is a common cancer gene and undergoes frequent mutation in melanoma. Small molecular BRAF kinase inhibitors have been approved for the treatment of melanoma patients carrying the BRAF V600E mutation, including Vemurafenib, Dabrafenib and so on. Boron dipyrromethene (BODIPY) as an important fluorescent class has been investigated extensively. Vemurafenib-BODIPY has been reported to visualize BRAF V600E mutated cancer cells. Herein, the designed BODIPY-based Vemurafenib derivatives targeting BRAF for cancer cell imaging are reported. The fluorescent probes are characterized and evaluated of photophysical properties, targeted binding and live cell imaging. Compound 1a exhibited promising fluorescence imaging ability. To improve fluorescence quantum yield, structural optimization is performed by incorporating meso N,N'-dialkyl-substituted amides to BODIPY core. Compound 1d shows excellent fluorescence properties and nice binding affinity. It allows visualization of BRAF V600E mutated cancer cells at low concentrations.

Exploit the γ-Glutamyl hydroxymethyl rhodamine green fluorescence in surgical resection: A systematic literature review on clinical indications, fields of application and outcomes

γ-Glutamyl Hydroxymethyl Rhodamine Green (γ-GHRG) fluorescence is a novel fluorescent agent used to enhance tissue visualization during surgical resections, especially in oncological procedures. This systematic review aims to evaluate the efficacy of γ-GHRG fluorescence in improving tumor margin detection, reducing recurrence rates, and enhancing surgical precision. A comprehensive search was conducted across PubMed, Embase, and Cochrane databases up to February 2024, following PRISMA guidelines. A total of 23 studies investigating the use of γ-GHRG fluorescence in surgical resection were included. Data on tumor visualization, surgical margin detection, and postoperative outcomes were analyzed. The included studies demonstrated that γ-GHRG fluorescence significantly improved tumor visualization in a variety of cancers, including ovarian cancer (26.1%), breast cancer (8.7%), lung cancer (8.7%), colorectal cancer (8.7%), kidney cancer (8.7%), head and neck cancer (8.7%), esophageal and gastric cancer (8.7%), prostate cancer (8.7%), brain tumors (gliomas) (4.3%), and liver cancer (4.3%). The probe's high specificity for γ-glutamyl transpeptidase (GGT), which is overexpressed in cancer cells, enabled real-time visualization of tumor margins, allowing for more precise resections. Studies also reported shorter surgical times and lower recurrence rates, particularly in high-grade tumors such as gliomas (4.3%). Although the results are promising, issues related to false positives, tissue specificity, and long-term safety were noted. γ-GHRG fluorescence shows significant potential in enhancing surgical outcomes by providing real-time guidance during tumor resections. Its high specificity for GGT and rapid fluorescence activation make it a valuable tool in cancer surgery. However, further clinical studies are required to address challenges related to sensitivity, specificity, and long-term safety, as well as to explore its application across different cancer types and surgical settings.

Application of Epithelial Growth Factor Receptor-Targeted Magnetic Resonance Imaging and Near-Infrared II Dual-Modal Probe in Lung Cancer Diagnosis and Surgical Resection

There has been an increase in the use of molecular probe diagnostic techniques for lung cancer, and magnetic resonance imaging (MRI) offers specific advantages for diagnosing pulmonary carcinoma. Furthermore, advancements in near-infrared II (NIR-II) fluorescence have provided a new method for precise intraoperative tumor resection. However, few probes combine preoperative diagnosis with intraoperative imaging. This study aims to fill this research void by employing a dual-modal probe that targets the epidermal growth factor receptor for MR and NIR-II imaging, enabling the preoperative diagnosis of lung cancer using MRI and precise intraoperative tumor localization using NIR-II with a single probe. The imaging effects and targeting ability of the probe were confirmed in cell lines, mouse models, and clinical samples. The MR signal decreased within 24 h in the patient-derived xenograft mouse model. The average signal-to-background ratio of NIR-II reached 3.98 ± 0.27. The clinical sample also showed a decrease in the T2 signal using MRI, and the NIR-II optical signal-to-background ratio was 3.29. It is expected that this probe can improve the diagnostic rate of lung cancer using MRI and enable precise intraoperative tumor resection using NIR-II.

Phase 2 Clinical Trial of VGT-309 for Intraoperative Molecular Imaging During Pulmonary Resection

BACKGROUND

Advances in intraoperative molecular imaging (IMI) may improve surgical outcomes when resecting tumors in the lung. A single-center trial was conducted using VGT-309, a cathepsin-targeted near-infrared imaging agent that causes lung nodules to fluoresce during surgical resection. The end point of this phase 2 study was to evaluate the frequency that IMI with VGT-309 resulted in a clinically significant event (CSE): localization of pulmonary nodules, discovery of unsuspected additional cancers, or identification of positive margins.

METHODS

Patients undergoing surgical resection for known or suspected cancer in the lung received VGT-309 (0.32 mg/kg) preoperatively. During the surgical procedure, localization and resection of the nodules were performed using standard surgical techniques. Near-infrared imaging was then used to localize nodules, seek occult lesions, and assess resection margins. Efficacy was measured by the frequency of CSEs.

RESULTS

Of the 40 patients who underwent pulmonary resection with VGT-309, 17 (42.5%) had at least 1 CSE. Near-infrared imaging identified lesions not found by standard surgical methods in 16 patients, additional cancers not found by preoperative imaging in 1 patient, and margins within 5 mm of the closest staple line in 2 patients. VGT-309 performance was tested across a broad range of tumor types and commercial near-infrared imaging systems. VGT-309 appeared safe, well-tolerated, with no infusion reactions, and no drug-related serious adverse events.

CONCLUSIONS

This phase 2 study demonstrated the utility of IMI with VGT-309 in localizing pulmonary nodules, recognizing synchronous lesions, and identifying positive margins. A multi-institutional study will further evaluate the efficacy of VGT-309.

Tumor agnostic ultrasmall nanoprobes for fluorescence-guided surgical resection in peritoneal metastasis

PURPOSE

Surgical excision of metastases is the only curative treatment strategy in peritoneal carcinomatosis management, and the completeness of tumor resection determines the success of the surgery. Tumor-specific fluorescence-guided probes can improve the outcomes of cytoreductive surgery and thereby prognosis. This study aimed to develop and evaluate the feasibility of fluorescently labeled ultrasmall porous silica nanoparticles (UPSN) for image-guided resection of peritoneally disseminated tumors of different origins.

METHODS

Ultrasmall fluorescent nanoprobes were synthesized and characterized for their physicochemical properties and stability. Tumor-specific uptake and biodistribution profiles were evaluated in syngeneic CT26 colorectal and KPC-689 pancreatic cancer murine models. The practicability of real-time optical UPSN-guided resection was examined in the CT26 colorectal cancer model using a surgical stereomicroscope. Quantitative measurements of tumor sensitivity and specificity were performed. Histopathological examination validated in vivo findings about tumor-specific accumulation and safety of ultrasmall fluorescent probes.

RESULTS

As-synthesized UPSNs were successfully surface modified with Cy5 or Cy3 dyes maintaining sub-15 nm size and near neutral charge which is beneficial for optimized in vivo pharmacokinetics. UPSN-Cy5 demonstrated high tumor-specific uptake and favorable biodistribution profiles in peritoneal metastasis models of CT26 and KPC tumors. Dye-conjugated UPSN enabled resection of microscopic lesions and achieved a higher tumor-to-background ratios in comparison to FDA-approved indocyanine green (ICG) dye in both models. Microscopic evaluation showed tumor localization and off-target safety profile of the UPSN-Cy5.

CONCLUSION

Ultrasmall fluorescent probes were effective in surgical resection of peritoneal metastases with high sensitivity and specificity, thus emerging as promising tumor agnostic agents for image-guided cancer surgery.

Ex Vivo Human Tissue Functions as a Testing Platform for the Evaluation of a Nerve-Specific Fluorophore

SIGNIFICANCE

Selecting a nerve-specific lead fluorescent agent for translation in fluorescence-guided surgery is time-consuming and expensive. Preclinical fluorescent agent studies rely primarily on animal models, which are a critical component of preclinical testing, but these models may not predict fluorophore performance in human tissues.

AIM

The primary aim of this study was to evaluate and compare two preclinical models to test tissue-specific fluorophores based on discarded human tissues. The secondary aim was to use these models to determine the ability of a molecularly targeted fluorophore, LGW16-03, to label ex vivo human nerve tissues.

APPROACH

Patients undergoing standard-of-care transtibial or transfemoral amputation were consented and randomized to topical or systemic administration of LGW16-03 following amputation. After probe administration, nerves and background tissues were surgically resected and imaged to determine nerve fluorescence signal-to-background tissue ratio (SBR) and signal-to-noise ratio (SNR) metrics. Analysis of variance (ANOVA) determined statistical differences in metric means between administration cohorts and background tissue groups. Receiver operating characteristic (ROC) curve-derived statistics quantified the discriminatory performance of LGW16-03 fluorescence for labeling nerve tissues.

RESULTS

Tissue samples from 18 patients were analyzed. Mean nerve-to-adipose SBR was greater than nerve-to-muscle SBR (p = 0.001), but mean nerve-to-adipose SNR was not statistically different from mean nerve-to-muscle SNR (p = 0.069). Neither SBR nor SNR means were statistically different between fluorophore administration cohorts (p ≥ 0.448). When administration cohorts were combined, nerve-to-adipose SBR was greater than nerve-to-muscle SBR (mean ± standard deviation; 4.2 ± 2.9 vs. 1.8 ± 1.9; p < 0.001), but SNRs for nerve-to-adipose and nerve-to-muscle were not significantly different (5.1 ± 4.0 vs. 3.1 ± 3.4; p = 0.055). ROC curve-derived statistics to quantify LGW16-03 nerve labeling performance varied widely between patients, with sensitivities and specificities ranging from 0.2-99.9% and 0.4-100.0%.

CONCLUSION

Systemic and topical administration of LGW16-03 yielded similar fluorescence labeling of nerve tissues. Both administration approaches provided nerve-specific contrast similar to that observed in preclinical animal models. Fluorescence contrast was generally higher for nerve-to-adipose versus nerve-to-muscle. Ex vivo human tissue models provide safe evaluation of fluorophores in the preclinical phase and can aid in the selection of lead agents prior to first-in-human trials.

Intraoperative imaging of residual ovarian cancer after neoadjuvant chemotherapy using indocyanine green

OBJECTIVES

Interval debulking surgery has similar outcomes and less morbidity compared with primary debulking in advanced ovarian cancer. However, there is controversy regarding the selection of chemotherapy-resistant clones. Complete resection is an essential prerequisite, and near-infrared surgery combined with various techniques for highlighting malignant foci strives to achieve actual complete resection. This study investigated the role of indocyanine green (ICG) in identifying additional residual malignant foci during interval debulking of apparently intact peritoneum not deemed clinically suspicious under white light inspection.

METHODS

Patients diagnosed with stage III or IV high-grade serous ovarian carcinoma, older than 18 years of age, with satisfactory hepatic and renal functions who underwent neoadjuvant chemotherapy according to the institutional protocol and were scheduled to undergo interval debulking surgery between 2020 and 2022 were deemed suitable for inclusion after agreeing to the study protocol and acknowledging no contraindications for the administration of the ICG product. After laparotomy and white light inspection, using bolus administration of ICG, additional suspect peritoneal samples in near infrared (defined by clinical hyper- or hypointensity areas compared with surrounding ICG fluorescence using the Zeiss Opmi Pentero 800 surgical microscope, that were not deemed clinically suspicious under white light) were excised. Descriptive statistics were inferred and the chi-square test was used for the comparison of excised areas. The Kaplan-Meier method was deployed for computing the overall survival and progression-free survival of the cohort. All statistical analyses were performed using IBM SPSS Statistics software.

RESULTS

Fifteen patients with a median age of 56 years were included. Most cases (n=10, 66.7%) were International Federation of Gynecology and Obstetrics (FIGO) stage III, and all patients received four to seven cycles of neoadjuvant platinum chemotherapy, with 40% of regimens using bevacizumab. The mean interval between neoadjuvant treatment and surgery was 39 (median 42, range 20-78) days. A total of 39 suspect additional peritoneal samples were analyzed, with 41% confirming malignant foci. The positive predictive value (PPV) for malignant foci was 30% in ICG hyperintense areas and 46% in ICG hypointense areas. Germline BRCA1/2 mutant patients and using neoadjuvant bevacizumab led to a higher PPV for ICG hypointense areas (60% and 72.7%, respectively). Overall, the number of additionally resected pathologically confirmed malignant lesions through ICG fluorescence increased by 25%.

CONCLUSIONS

The use of ICG was associated with an increase in the resection of samples with residual malignant foci. Overall, hypointense areas had a higher positive PPV for malignant foci in comparison with hyperintense ICG areas (46% vs 30%), which could be interpreted in the context of dynamic changes in the tumor microenvironment or enhanced permeability and retention effect following neoadjuvant chemotherapy.

Combined dual-channel fluorescence depth sensing of indocyanine green and protoporphyrin IX kinetics in subcutaneous murine tumors

Significance

Fluorescence sensing within tissue is an effective tool for tissue characterization; however, the modality and geometry of the image acquisition can alter the observed signal.

Aim

We introduce a novel optical fiber-based system capable of measuring two fluorescent contrast agents through 2 cm of tissue with simple passive electronic switching between the excitation light, simultaneously acquiring fluorescence and excitation data. The goal was to quantify indocyanine green (ICG) and protoporphyrin IX (PpIX) within tissue, and the sampling method was compared with wide-field surface imaging to contrast the value of deep sensing versus surface imaging.

Approach

This was achieved by choosing filters for specific wavelengths that were mutually exclusive between ICG and PpIX and coupling these filters to two separate detectors, which allows for direct swapping of the excitation and emission channels by switching the on-time of each excitation laser between 780- and 633-nm wavelengths.

Results

This system was compared with two non-contact surface imaging systems for both ICG and PpIX, which revealed that the fluorescence depth sensing system was superior in its ability to resolve kinetics differences in deeper tissues that would normally be dominated by strong signals from skin and other surface tissues. Specifically, the system was tested using pancreatic adenocarcinoma tumors injected into murine models, which were imaged at several time points throughout tumor growth to its ∼ 6 - mm diameter. This demonstrated the system's capability to track longitudinal changes in ICG and PpIX kinetics that result from tumor growth and development, with larger tumors showing sluggish uptake and clearance of ICG, which was not observable with surface imaging. Similarly, PpIX was quantified, which showed slower kinetics over different time points, and was further compared with the wide-filed imager. These results were further validated through depth measurements in tissue phantoms and model-based interpretation.

Conclusion

This fluorescence depth sensing system can be used to sample the interior blood flow characteristics by ICG sensing of tissue as deep as 20 mm into the tissue with sensitivity to kinetics that are superior to surface imaging and may be combined with other imaging modalities such as ultrasound to provide guided deep fluorescence measurements.

Systematic comparison of fluorescence imaging in the near-infrared and shortwave-infrared spectral range using clinical tumor samples containing cetuximab-IRDye800CW

Significance

Shortwave-infrared (SWIR) imaging is reported to yield better contrast in fluorescence-guided surgery than near-infrared (NIR) imaging, due to a reduction in scattering. This benefit of SWIR was shown in animal studies, however not yet in clinical studies with patient samples.

Aim

We investigate the potential benefit of SWIR to NIR imaging in clinical samples containing cetuximab-IRDye800CW in fluorescence-guided surgery.

Approach

The potential of the epidermal growth factor-targeted NIR dye cetuximab-IRDye800CW in the shortwave range was examined by recording the absorption and emission spectrum. An ex vivo comparison of NIR and SWIR images using clinical tumor samples of patients with penile squamous cell carcinoma (PSCC) and head and neck squamous cell carcinoma (HNSCC) containing cetuximab-IRDye800CW was performed. The comparison was based on the tumor-to-background ratio and an adapted contrast-to-noise ratio (aCNR) using the standard of care pathology tissue assessment as the golden standard.

Results

Based on the emission spectrum, cetuximab-IRDye800CW can be detected in the SWIR range. In clinical PSCC samples, overall SWIR imaging was found to perform similarly to NIR imaging (NIR imaging is better than SWIR in the 2/7 criteria examined, and SWIR is better than NIR in the 3/7 criteria). However, when inspecting HNSCC data, NIR is better than SWIR in nearly all (5/7) examined criteria. This difference seems to originate from background autofluorescence overwhelming the off-peak SWIR fluorescence signal in HNSCC tissue.

Conclusion

SWIR imaging using the targeted tracer cetuximab-IRDye800CW currently does not provide additional benefit over NIR imaging in ex vivo clinical samples. Background fluorescence in the SWIR region, resulting in a higher background signal, limits SWIR imaging in HNSCC samples. However, SWIR shows potential in increasing the contrast of tumor borders in PSCC samples, as shown by a higher aCNR over a line.

Intraoperative fluorescence redefining neurosurgical precision

Surgical resection is essential for treating solid tumors, with success largely dependent on the complete excision of neoplastic cells. However, neurosurgical procedures must delicately balance tumor removal with the preservation of surrounding tissue. Achieving clear margins is particularly challenging in cases like glioblastoma due to the limitations of traditional white light visualization. These limitations often result in incomplete resections, leading to frequent recurrences, or excessive resection that harms vital neural structures, causing iatrogenic nerve damage, which can lead to sensory and functional deficits. Current statistics reveal a 90% recurrence rate for malignant gliomas. Similarly, an 8% incidence of iatrogenic nerve trauma contributes to an estimated 25 million cases of peripheral nerve injury globally each year. These figures underscore the urgent need for improved intraoperative techniques for lesion margin and nerve identification and visualization. Recent advances in neurosurgical imaging, such as fluorescence-guided surgery (FGS), have begun to address these challenges. Fluorescent agents used in FGS illuminate target tissues, although not all do so selectively. Despite the promising results of agents such as 5-aminolevulinic acid and indocyanine green, their applications are mainly limited by issues of sensitivity and specificity. Furthermore, these agents do not effectively address the need for precise nerve visualization. Nerve Peptide 41, a novel systemically administered fluorescent nerve-targeted probe, shows promise in filling this gap. This review assesses the major fluorescent imaging modalities in neurosurgery, highlighting each of their benefits, limitations, and potential.

Impact of signal-to-noise ratio and contrast definition on the sensitivity assessment and benchmarking of fluorescence molecular imaging systems

Significance

Standardization of fluorescence molecular imaging (FMI) is critical for ensuring quality control in guiding surgical procedures. To accurately evaluate system performance, two metrics, the signal-to-noise ratio (SNR) and contrast, are widely employed. However, there is currently no consensus on how these metrics can be computed.

Aim

We aim to examine the impact of SNR and contrast definitions on the performance assessment of FMI systems.

Approach

We quantified the SNR and contrast of six near-infrared FMI systems by imaging a multi-parametric phantom. Based on approaches commonly used in the literature, we quantified seven SNRs and four contrast values considering different background regions and/or formulas. Then, we calculated benchmarking (BM) scores and respective rank values for each system.

Results

We show that the performance assessment of an FMI system changes depending on the background locations and the applied quantification method. For a single system, the different metrics can vary up to ∼ 35    dB (SNR), ∼ 8.65    a . u . (contrast), and ∼ 0.67    a . u . (BM score).

Conclusions

The definition of precise guidelines for FMI performance assessment is imperative to ensure successful clinical translation of the technology. Such guidelines can also enable quality control for the already clinically approved indocyanine green-based fluorescence image-guided surgery.

Indocyanine green and near-infrared fluorescence-guided surgery for gastric cancer: a narrative review

In recent years, indocyanine green (ICG) and near-infrared (NIR) fluorescence-guided surgery has become a versatile and well-researched tool for gastric cancer treatment. Our narrative review aims to explore the applications, benefits, and challenges that are associated with this technique. Initially used to detect sentinel lymph nodes in early gastric cancer, its scope has broadened to include several clinical applications. Its most notable advantages are the ability to guide standard lymphadenectomy, intraoperatively localize tumors and define tumor margins. Despite these advantages, there are still ongoing discussions regarding its accuracy, lack of standardized administration, and oncologic safety in sentinel node navigation surgery. The limited tumor specificity of ICG has been especially put into question, hindering its ability to accurately differentiate between malignant and healthy tissue. With ongoing innovations and its integration into newer endoscopic and robotic systems, ICG-NIR fluorescence imaging shows promise in becoming a standard tool in the surgical treatment of gastric cancer.

Nano-fluorescence imaging: advancing lymphatic disease diagnosis and monitoring

The lymphatic system plays a crucial role in maintaining physiological homeostasis and regulating immune responses. Traditional imaging modalities such as magnetic resonance imaging, computerized tomography, and positron emission tomography have been widely used to diagnose disorders in the lymphatic system, including lymphedema, lymphangioma, lymphatic metastasis, and Castleman disease. Nano-fluorescence technology has distinct advantages-including naked-eye visibility, operational simplicity, portability of the laser, and real-time visibility-and serves as an innovative alternative to traditional imaging techniques. This review explores recent advancements in nano-fluorescence imaging aimed at enhancing the resolution of lymphatic structure, function, and immunity. After delineating the fundamental characteristics of lymphatic systems, it elaborates on the development of various nano-fluorescence systems (including nanoparticles incorporating fluorescent dyes and those with intrinsic fluorescence) while addressing key challenges such as photobleaching, limited tissue penetration, biocompatibility, and signal interference from biomolecules. Furthermore, this review highlights the clinical applications of nano-fluorescence and its potential integration into standard diagnostic protocols. Ongoing advancements in nanoparticle technology underscore the potential of nano-fluorescence to revolutionize the diagnosis and treatment of lymphatic disease.

Development of folate receptor targeting chimeras for cancer selective degradation of extracellular proteins

Targeted protein degradation has emerged as a novel therapeutic modality to treat human diseases by utilizing the cell's own disposal systems to remove protein target. Significant clinical benefits have been observed for degrading many intracellular proteins. Recently, the degradation of extracellular proteins in the lysosome has been developed. However, there have been limited successes in selectively degrading protein targets in disease-relevant cells or tissues, which would greatly enhance the development of precision medicine. Additionally, most degraders are not readily available due to their complexity. We report a class of easily accessible Folate Receptor TArgeting Chimeras (FRTACs) to recruit the folate receptor, primarily expressed on malignant cells, to degrade extracellular soluble and membrane cancer-related proteins in vitro and in vivo. Our results indicate that FRTAC is a general platform for developing more precise and effective chemical probes and therapeutics for the study and treatment of cancers.

Progress of fluorescence imaging in lymph node dissection surgery for prostate and bladder cancer

Fluorescence imaging is a relatively new imaging method used to visualize different tissue structures to help guide intraoperative operations, which has potential advantages with high sensitivity and contrast compared to conventional imaging. In this work, we review fluorescent contrast agents and devices used for lymphatic system imaging. Indocyanine green is the most widely utilized due to its high sensitivity, specificity, low background fluorescence, and safety profile. In prostate and bladder cancer lymph node dissection, the complex lymphatic drainage can result in missed metastatic nodes and extensive dissection increases the risk of complications like lymphocele, presenting a significant challenge for urologists. Fluorescence-guided sentinel lymph node dissection facilitates precise tumor staging. The combination of fluorescence and radiographic imaging improves the accuracy of lymph node staging. Multimodal imaging presents new potential for precisely identifying metastatic pelvic lymph nodes.

Surface-engineered erythrocyte membrane-camouflage fluorescent bioprobe for precision ovarian cancer surgery

PURPOSE

Fluorescence imaging-guided surgery has been used in oncology. However, for tiny tumors, the current imaging probes are still difficult to achieve high-contrast imaging, leading to incomplete resection. In this study, we achieved precise surgical resection of tiny metastatic cancers by constructing an engineering erythrocyte membrane-camouflaged bioprobe (AR-M@HMSN@P).

METHODS

AR-M@HMSN@P combined the properties of aggregation-induced emission luminogens (AIEgens) named PF3-PPh3 (P), with functional erythrocyte membrane modified by a modular peptide (AR). Interestingly, AR was composed of an asymmetric tripodal pentapeptide scaffold (GGKGG) with three appended modulars: KPSSPPEE (A6) peptide, RRRR (R4) peptide and cholesterol. To verify the specificity of the probe in vitro, SKOV3 cells with overexpression of CD44 were used as the positive group, and HLF cells with low expression of CD44 were devoted as the control group. The AR-M@HMSN@P fluorescence imaging was utilized to provide surgical guidance for the removal of micro-metastatic lesions.

RESULTS

In vivo, the clearance of AR-M@HMSN@P by the immune system was reduced due to the natural properties inherited from erythrocytes. Meanwhile, the A6 peptide on AR-M@HMSN@P was able to specifically target CD44 on ovarian cancer cells, and the electrostatic attraction between the R4 peptide and the cell membrane enhanced the firmness of this targeting. Benefiting from these multiple effects, AR-M@HMSN@P achieved ultra-precise tumor imaging with a signal-to-noise ratio (SNR) of 15.2, making it possible to surgical resection of tumors < 1 mm by imaging guidance.

CONCLUSION

We have successfully designed an engineered fluorescent imaging bioprobe (AR-M@HMSN@P), which can target CD44-overexpressing ovarian cancers for precise imaging and guide the resection of minor tumors. Notably, this work holds significant promise for developing biomimetic probes for clinical imaging-guided precision cancer surgery by exploiting their externally specified functional modifications.

Accurate Co-Localization of Luciferase Expression and Fluorescent Anti-CEA Antibody Targeting of Liver Metastases in an Orthotopic Mouse Model of Colon Cancer

BACKGROUND

The present study aimed to validate the accuracy of a tumor-specific antibody to target liver metastases of colorectal cancer.

METHODS

A humanized anti-CEA antibody conjugated to a fluorescent dye (M5A-IR800) was tested for targeting human colorectal cancer liver metastases (CRLMs) expressing luciferase in an orthotopic mouse model. Orthotopic mouse models of CRLMs were established by implanting fragments of a luciferase-expressing human colorectal cancer cell line, LS174T, in the liver of nude mice. Mice received 50 µg M5A-IR800 72 h prior to imaging. To test co-localization, bioluminescence imaging was performed using D-luciferin, which was given via intraperitoneal injection just prior to imaging.

RESULTS

Tumors were able to be visualized non-invasively through the skin with the luciferase-luciferin signal. Intra-abdominal imaging showed accurate labeling of CRLMs with M5A-IR800, which co-localized with the luciferase-luciferin signal.

CONCLUSIONS

The present results validate the accuracy of a tumor-specific anti-CEA antibody in targeting liver metastases of colorectal cancer.

Dual-Modal Near-Infrared Organic Nanoparticles: Integrating Mild Hyperthermia Phototherapy with Fluorescence Imaging

Purpose

Our study seeks to develop dual-modal organic-nanoagents for cancer therapy and real-time fluorescence imaging, followed by their pre-clinical evaluation on a murine model. Integrating NIR molecular imaging with nanotechnology, our aim is to improve outcomes for early-stage cutaneous melanoma by offering more effective and less invasive methods. This approach has the potential to enhance both photothermal therapy (PTT) and Sentinel Lymph Node Biopsy (SLNB) procedures for melanoma patients.

Methods

NIR-797-isothiocyanate was encapsulated in poly(D,L-lactide-co-glycolide) acid (PLGA) nanoparticles (NPs) using a two-step protocol, followed by thorough characterization, including assessing loading efficiency, fluorescence stability, and photothermal conversion. Biocompatibility and cellular uptake were tested in vitro on melanoma cells, while PTT assay, with real-time thermal monitoring, was performed in vivo on tumor-bearing mice under irradiation with an 808 nm laser. Finally, ex vivo fluorescence microscopy, histopathological assay, and TEM imaging were performed.

Results

Our PLGA NPs, with a diameter of 270 nm, negative charge, and 60% NIR-797 loading efficiency, demonstrated excellent stability and fluorescence properties, as well as efficient light-to-heat conversion. In vitro studies confirmed their biocompatibility and cellular internalization. In vivo experiments demonstrated their efficacy as photothermal agents, inducing mild hyperthermia with temperatures reaching up to 43.8 °C. Ex vivo microscopy of tumor tissue confirmed persistent NIR fluorescence and uniform distribution of the NPs. Histopathological and TEM assays revealed early apoptosis, immune cell response, ultrastructural damage, and intracellular material debris resulting from combined NP treatment and irradiation. Additionally, TEM analyses of irradiated zone margins showed attenuated cellular damage, highlighting the precision and effectiveness of our targeted treatment approach.

Conclusion

Specifically tailored for dual-modal NIR functionality, our NPs offer a novel approach in cancer PTT and real-time fluorescence monitoring, signaling a promising avenue toward clinical translation.

Targeting Patient-Derived Orthotopic Gastric Cancers with a Fluorescent Humanized Anti-CEA Antibody

BACKGROUND

Gastric cancer poses a major diagnostic and therapeutic challenge as surgical resection provides the only opportunity for a cure. Specific labeling of gastric cancer could distinguish resectable and nonresectable disease and facilitate an R0 resection, which could improve survival.

METHODS

Two patient-derived gastric cancer lines, KG8 and KG10, were established from surgical specimens of two patients who underwent gastrectomy for gastric adenocarcinoma. Harvested tumor fragments were implanted into the greater curvature of the stomach to establish patient-derived orthotopic xenograft (PDOX) models. M5A (humanized anti-CEA antibody) or IgG control antibodies were conjugated with the near-infrared dye IRDye800CW. Mice received 50 µg of M5A-IR800 or 50 µg of IgG-IR800 intravenously and were imaged after 72 hr. Fluorescence imaging was performed by using the LI-COR Pearl Imaging System. A tumor-to-background ratio (TBR) was calculated by dividing the mean fluorescence intensity of the tumor versus adjacent stomach tissue.

RESULTS

M5A-IR800 administration resulted in bright labeling of both KG8 and K10 tumors. In the KG8 PDOX models, the TBR for M5A-IR800 was 5.85 (SE ± 1.64) compared with IgG-IR800 at 0.70 (SE ± 0.17). The K10 PDOX models had a TBR of 3.71 (SE ± 0.73) for M5A-IR800 compared with 0.66 (SE ± 0.12) for IgG-IR800.

CONCLUSIONS

Humanized anti-CEA (M5A) antibodies conjugated to fluorescent dyes provide bright and specific labeling of gastric cancer PDOX models. This tumor-specific fluorescent antibody is a promising potential clinical tool to detect the extent of disease for the determination of resectability as well as to visualize tumor margins during gastric cancer resection.

Fluorescence imaging-guided surgery: current status and future directions

Surgery is one of the most important paradigms for tumor therapy, while fluorescence imaging (FI) offers real-time intraoperative guidance, greatly boosting treatment prognosis. The imaging fidelity heavily relies on not only imaging facilities but also probes for imaging-guided surgery (IGS). So far, a great number of IGS probes with emission in visible (400-700 nm) and near-infrared (NIR 700-1700 nm) windows have been developed for pinpointing disease margins intraoperatively. Herein, the state-of-the-art fluorescent probes for IGS are timely updated, with a special focus on the fluorescent probes under clinical examination. For a better demonstration of the superiority of NIR FI over visible FI, both imaging modalities are critically compared regarding signal-to-background ratio, penetration depth, resolution, tissue autofluorescence, photostability, and biocompatibility. Various types of fluorescence IGS have been summarized to demonstrate its importance in the medical field. Furthermore, the most recent progress of fluorescent probes in NIR-I and NIR-II windows is summarized. Finally, an outlook on multimodal imaging, FI beyond NIR-II, efficient tumor targeting, automated IGS, the use of AI and machine learning for designing fluorescent probes, and the fluorescence-guided da Vinci surgical system is given. We hope this review will stimulate interest among researchers in different areas and expedite the translation of fluorescent probes from bench to bedside.

Exploring flavylium-based SWIR emitters: Design, synthesis and optical characterization of dyes derivatized with polar moieties

Imaging in the shortwave infrared (SWIR, 1000-1700 nm) region is gaining traction for biomedical applications, leading to an in-depth search for fluorophores emitting at these wavelengths. The development of SWIR emitters, to be used in vivo in biological media, is mostly hampered by the considerable lipophilicity of the structures, resulting from the highly conjugated scaffold required to shift the emission to this region, that limit their aqueous solubility. In this work, we have modulated a known SWIR emitter, named Flav7, by adding hydrophilic moieties to the flavylium scaffold and we developed a new series of Flav7-derivatives, which proved to be indeed more polar than the parent compound, but still not freely water-soluble. Optical characterization of these derivatives allowed us to select FlavMorpho, a new compound with improved emission properties compared to Flav7. Encapsulation of the two compounds in micelles resulted in water-soluble SWIR emitters, with FlavMorpho micelles being twice as emissive as Flav7 micelles. The SWIR emission extent of FlavMorpho micelles proved also superior to the tail-emission of Indocyanine Green (ICG), the FDA-approved reference cyanine, in the same region, by exciting the probes at their respective absorption maxima in phosphate buffered saline (PBS) solution. The availability of optical imaging devices equipped with lasers able to excite these dyes at their maximum of absorption in the SWIR region, could pave the way for implemented SWIR imaging results.

A systematic methodology review of fluorescence-guided cancer surgery to inform the development of a core master protocol and outcome set

BACKGROUND

Fluorescence-guided precision cancer surgery may improve survival and minimize patient morbidity. Efficient development of promising interventions is however hindered by a lack of common methodology. This methodology review aimed to synthesize descriptions of technique, governance processes, surgical learning and outcome reporting in studies of fluorescence-guided cancer surgery to provide guidance for the harmonized design of future studies.

METHODS

A systematic search of MEDLINE, EMBASE and CENTRAL databases from 2016-2020 identified studies of all designs describing the use of fluorescence in cancer surgery. Dual screening and data extraction was conducted by two independent teams.

RESULTS

Of 13,108 screened articles, 426 full text articles were included. The number of publications per year increased from 66 in 2016 to 115 in 2020. Indocyanine green was the most commonly used fluorescence agent (391, 91.8%). The most common reported purpose of fluorescence guided surgery was for lymph node mapping (195, 5%) and non-specific tumour visualization (94, 2%). Reporting about surgical learning and governance processes incomplete. A total of 2,577 verbatim outcomes were identified, with the commonly reported outcome lymph node detection (796, 30%). Measures of recurrence (32, 1.2%), change in operative plan (23, 0.9%), health economics (2, 0.1%), learning curve (2, 0.1%) and quality of life (2, 0.1%) were rarely reported.

CONCLUSION

There was evidence of methodological heterogeneity that may hinder efficient evaluation of fluorescence surgery. Harmonization of the design of future studies may streamline innovation.

Dual Tumor-Selective β-Carboline-Based Fluorescent Probe for High-Contrast/Rapid Diagnosis of Clinical Tumor Tissues

Given that precise/rapid intraoperative tumor margin identification is still challenging, novel fluorescent probes HY and HYM, based on acidic tumor microenvironment (TME) activation and organic anion transporting polypeptide (OATPs)-mediated selective uptake, were constructed and synthesized. Both of them possessed acidic pH-activatable and reversible fluorescence as well as large Stokes shift. Compared with HY, HYM had a higher (over 9-fold) enhancement in fluorescence with pH ranging from 7.6 to 4.0, and the fluorescence quantum yield of HYM (ΦF = 0.49) at pH = 4.0 was 8-fold stronger than that (ΦF = 0.06) at pH = 7.4. Mechanism research demonstrated that acidic TME-induced protonation of the pyridine N atom on β-carbolines accounted for the pH-sensitive fluorescence by influencing the intramolecular charge transfer (ICT) effect. Furthermore, HYM selectively lit up cancer cells and tumor tissues not only by "off-on" fluorescence but also by OATPs (overexpressed on cancer cells)-mediated cancer cellular internalization, offering dual tumor selectivity for precise visualization of tumor mass and intraoperative guidance upon in situ spraying. Most importantly, HYM enabled rapid and high-contrast (tumor-to-normal tissue ratios > 6) human tumor margin identification in clinical tumor tissues by simple spraying within 6 min, being promising for aiding in clinical surgical resection.

In vivo imaging of prostate tumor-targeted folic acid conjugated quantum dots

Cancer is a major threat to human health; thus, early detection is imperative for successful management. Rapid diagnosis can be achieved by imaging primary (subcutaneous) tumors using fluorophores conjugated with tumor markers. Here, the application of biocompatible, quantum efficient, monodisperse, and photostable polymer-coated quantum dots (PQDs) is demonstrated for targeted prostate tumor imaging in living SCID mice. Briefly, PQDs (blue) are conjugated to folic acid (FA-PQDs) using DCC-NHS chemistry. Initially, in vitro targeted imaging via FA-PQDs is evaluated in LNCaP cells. The confocal microscopic evaluation demonstrates the uptake of FA-PQDs. To understand the dispersion of PQDs in vivo, the biodistribution of PQDs is assessed at different time intervals (1- 180 min) using whole-body fluorescence imaging and computed tomography (CT) scan. PQDs are seen to accumulate in organs like the liver, kidneys, spleen, lungs, and urinary bladder within 60 min, however, PQDs are not observed at 180 min indicating renal clearance. Further, to target the prostate tumor (~ 200 mm3) in mice, FA-PQDs are injected intravenously, and whole-body fluorescence imaging along with a CT scan is recorded. FA-PQDs are seen at the tumor site as compared to PQDs. The results confirm that the FA-PQDs function as excellent nanoprobes for targeted tumor imaging in vivo.

Fluorescent nano- and microparticles for sensing cellular microenvironment: past, present and future applications

The tumor microenvironment (TME) demonstrates distinct hallmarks, including acidosis, hypoxia, reactive oxygen species (ROS) generation, and altered ion fluxes, which are crucial targets for early cancer biomarker detection, tumor diagnosis, and therapeutic strategies. Various imaging and sensing techniques have been developed and employed in both research and clinical settings to visualize and monitor cellular and TME dynamics. Among these, ratiometric fluorescence-based sensors have emerged as powerful analytical tools, providing precise and sensitive insights into TME and enabling real-time detection and tracking of dynamic changes. In this comprehensive review, we discuss the latest advancements in ratiometric fluorescent probes designed for the optical mapping of pH, oxygen, ROS, ions, and biomarkers within the TME. We elucidate their structural designs and sensing mechanisms as well as their applications in in vitro and in vivo detection. Furthermore, we explore integrated sensing platforms that reveal the spatiotemporal behavior of complex tumor cultures, highlighting the potential of high-resolution imaging techniques combined with computational methods. This review aims to provide a solid foundation for understanding the current state of the art and the future potential of fluorescent nano- and microparticles in the field of cellular microenvironment sensing.

Intraoperative Imaging in Hepatopancreatobiliary Surgery

Hepatopancreatobiliary surgery belongs to one of the most complex fields of general surgery. An intricate and vital anatomy is accompanied by difficult distinctions of tumors from fibrosis and inflammation; the identification of precise tumor margins; or small, even disappearing, lesions on currently available imaging. The routine implementation of ultrasound use shifted the possibilities in the operating room, yet more precision is necessary to achieve negative resection margins. Modalities utilizing fluorescent-compatible dyes have proven their role in hepatopancreatobiliary surgery, although this is not yet a routine practice, as there are many limitations. Modalities, such as photoacoustic imaging or 3D holograms, are emerging but are mostly limited to preclinical settings. There is a need to identify and develop an ideal contrast agent capable of differentiating between malignant and benign tissue and to report on the prognostic benefits of implemented intraoperative imaging in order to navigate clinical translation. This review focuses on existing and developing imaging modalities for intraoperative use, tailored to the needs of hepatopancreatobiliary cancers. We will also cover the application of these imaging techniques to theranostics to achieve combined diagnostic and therapeutic potential.

BF2-Azadipyrromethene Fluorophores for Intraoperative Vital Structure Identification

A series of mono- and bis-polyethylene glycol (PEG)-substituted BF2-azadipyrromethene fluorophores have been synthesized with emissions in the near-infrared region (700-800 nm) for the purpose of fluorescence guided intraoperative imaging; chiefly ureter imaging. The Bis-PEGylation of fluorophores resulted in higher aqueous fluorescence quantum yields, with PEG chain lengths of 2.9 to 4.6 kDa being optimal. Fluorescence ureter identification was possible in a rodent model with the preference for renal excretion notable through comparative fluorescence intensities from the ureters, kidneys and liver. Ureteral identification was also successfully performed in a larger animal porcine model under abdominal surgical conditions. Three tested doses of 0.5, 0.25 and 0.1 mg/kg all successfully identified fluorescent ureters within 20 min of administration which was sustained up to 120 min. 3-D emission heat map imaging allowed the spatial and temporal changes in intensity due to the distinctive peristaltic waves of urine being transferred from the kidneys to the bladder to be identified. As the emission of these fluorophores could be spectrally distinguished from the clinically-used perfusion dye indocyanine green, it is envisaged that their combined use could be a step towards intraoperative colour coding of different tissues.

Comparison of Near-Infrared Imaging Agents Targeting the PTPmu Tumor Biomarker

PURPOSE

Maximal, safe resection of solid tumors is considered a critical first step in successful cancer treatment. The advent of fluorescence image-guided surgery (FIGS) using non-specific agents has improved patient outcomes, particularly in the case of glioblastoma. Molecularly targeted agents that recognize specific tumor biomarkers have the potential to augment these gains. Identification of the optimal combination of targeting moiety and fluorophore is needed prior to initiating clinical trials.

PROCEDURES

A 20-amino acid peptide (SBK2) recognizing the receptor protein-tyrosine phosphatase mu (PTPmu)-derived tumor-specific biomarker, with or without a linker, was conjugated to three different near-infrared fluorophores: indocyanine green (ICG), IRDye® 800CW, and Tide Fluor™ 8WS. The in vivo specificity, time course, and biodistribution were evaluated for each using mice with heterotopic human glioma tumors that express the PTPmu biomarker to identify component combinations with optimal properties for FIGS.

RESULTS

SBK2 conjugated to ICG demonstrated excellent specificity for gliomas in heterotopic tumors. SBK2-ICG showed significantly higher in vivo tumor labeling compared to the Scram-ICG control from 10 min to 24 h, p < 0.01 at all timepoints, following injection, as well as a significantly higher ex vivo tumor signal at 24 h, p < 0.001. Inserting a six-amino acid linker between the targeting peptide and ICG increased the clearance rate and resulted in significantly higher in vivo tumor signal relative to its linker-containing Scrambled control from 10 min to 8 h, p < 0.05 at all timepoints, after dosing. Agents made with the more hydrophilic IRDye® 800CW and Tide Fluor™ 8WS showed no specific tumor labeling relative to the controls. The IRDye 800CW-conjugated agents cleared within 1 h, while the non-specific fluorescent tumor signal generated by the Tide Fluor 8WS-conjugated agents persists beyond 24 h.

CONCLUSIONS

The SBK2 PTPmu-targeting peptide conjugated to ICG specifically labels heterotopic human gliomas grown in mice between 10 min and 24 h following injection. Similar molecules constructed with more hydrophilic dyes demonstrated no specificity. These studies present a promising candidate for use in FIGS of PTPmu biomarker-expressing tumors.