Fluorescence contrast-enhanced proliferative lesion imaging by enema administration of indocyanine green in a rat model of colon carcinogenesis

Mechanisms of delayed indocyanine green fluorescence and applications to clinical disease processes

BACKGROUND

Delayed indocyanine green fluorescence imaging is under investigation in various clinical disease processes. Understanding the mechanisms of indocyanine green accumulation and retention is essential to correctly interpreting and analyzing imaging data. The purpose of this scoping review was to synthesize what is known about the mechanism of indocyanine green retention at the cellular level to better understand the clinical nuances of delayed indocyanine green imaging and identify critical gaps in our knowledge to guide future studies.

METHODS

We performed a scoping review of 7,087 citations after performing database searches of PubMed, Scopus, the Cochrane Library, and the Web of Science Core Collection electronic databases. Studies were eligible for inclusion if they were peer-reviewed original research discussing the mechanism of indocyanine green retention in the results section in disease processes involving inflammation and/or necrosis, including cancer, and were available in English. Data were extracted using Covidence software.

RESULTS

Eighty-nine studies were included in the final analysis. Several features of indocyanine green retention were identified.

CONCLUSION

We identified several mechanistic features involved in indocyanine green accumulation in diseased tissue that overall had distinct mechanisms of indocyanine green retention in tumors, nontumor inflammation, and necrosis. Our study also reveals new insights on how inflammatory infiltrate influences indocyanine green fluorescence imaging. These findings are noteworthy because they add to our understanding of how fluorescence-guided surgery may be optimized based on the pathology of interest via specific indocyanine green dosing and timing of image acquisition.

Fluorescence imaging for real-time detection of breast cancer tumors using IV injection of indocyanine green with non-conventional imaging: a systematic review of preclinical and clinical studies of perioperative imaging technologies

BACKGROUND

This review summarizes the available data on the effectiveness of indocyanine green fluorescence imaging (ICG-FI) for real-time detection of breast cancer (BC) tumors with perioperative imaging technologies.

METHODS

PubMed and Scopus databases were exhaustively searched for publications on the use of the real-time ICG-FI evaluation of BC tumors with non-conventional breast imaging technologies.

RESULTS

Twenty-three studies were included in this review. ICG-FI has been used for BC tumor identification in 12 orthotopic animal tumor experiences, 4 studies on animal assessment, and for 7 human clinical applications. The BC tumor-to-background ratio (TBR) was 1.1-8.5 in orthotopic tumor models and 1.4-3.9 in animal experiences. The detection of primary human BC tumors varied from 40% to 100%. The mean TBR reported for human BC varied from 2.1 to 3.7. In two studies evaluating BC surgical margins, good sensitivity (93.3% and 100%) and specificity (60% and 96%) have been reported, with a negative predictive value of ICG-FI to predict margin involvement intraoperatively of 100% in one study.

CONCLUSIONS

The use of ICG-FI as a guiding tool for the real-time identification of BC tumors and for the assessment of tumor boundaries is promising. There is great variability between the studies with regard to timing and dose. Further evidence is needed to assess whether ICG-guided BC surgery may be implemented as a standard of care.

Near infrared conjugated polymer nanoparticles (CPN™) for tracking cells using fluorescence and optoacoustic imaging

Tracking the biodistribution of cell therapies is crucial for understanding their safety and efficacy. Optical imaging techniques are particularly useful for tracking cells due to their clinical translatability and potential for intra-operative use to validate cell delivery. However, there is a lack of appropriate optical probes for cell tracking. The only FDA-approved material for clinical use is indocyanine green (ICG). ICG can be used for both fluorescence and photoacoustic imaging, but is prone to photodegradation, and at higher concentrations, undergoes quenching and can adversely affect cell health. We have developed novel near-infrared imaging probes comprising conjugated polymer nanoparticles (CPNs™) that can be fine-tuned to absorb and emit light at specific wavelengths. To compare the performance of the CPNs™ with ICG for in vivo cell tracking, labelled mesenchymal stromal cells (MSCs) were injected subcutaneously in mice and detected using fluorescence imaging (FI) and a form of photoacoustic imaging called multispectral optoacoustic tomography (MSOT). MSCs labelled with either ICG or CPN™ 770 could be detected with FI, but only CPN™ 770-labelled MSCs could be detected with MSOT. These results show that CPNs™ show great promise for tracking cells in vivo using optical imaging techniques, and for some applications, out-perform ICG.

Investigation of artificial intelligence integrated fluorescence endoscopy image analysis with indocyanine green for interpretation of precancerous lesions in colon cancer

Indocyanine green (ICG) has been used in clinical practice for more than 40 years and its safety and preferential accumulation in tumors has been reported for various tumor types, including colon cancer. However, reports on clinical assessments of ICG-based molecular endoscopy imaging for precancerous lesions are scarce. We determined visualization ability of ICG fluorescence endoscopy in colitis-associated colon cancer using 30 lesions from an azoxymethane/dextran sulfate sodium (AOM/DSS) mouse model and 16 colon cancer patient tissue-samples. With a total of 60 images (optical, fluorescence) obtained during endoscopy observation of mouse colon cancer, we used deep learning network to predict four classes (Normal, Dysplasia, Adenoma, and Carcinoma) of colorectal cancer development. ICG could detect 100% of carcinoma, 90% of adenoma, and 57% of dysplasia, with little background signal at 30 min after injection via real-time fluorescence endoscopy. Correlation analysis with immunohistochemistry revealed a positive correlation of ICG with inducible nitric oxide synthase (iNOS; r > 0.5). Increased expression of iNOS resulted in increased levels of cellular nitric oxide in cancer cells compared to that in normal cells, which was related to the inhibition of drug efflux via the ABCB1 transporter down-regulation resulting in delayed retention of intracellular ICG. With artificial intelligence training, the accuracy of image classification into four classes using data sets, such as fluorescence, optical, and fluorescence/optical images was assessed. Fluorescence images obtained the highest accuracy (AUC of 0.8125) than optical and fluorescence/optical images (AUC of 0.75 and 0.6667, respectively). These findings highlight the clinical feasibility of ICG as a detector of precancerous lesions in real-time fluorescence endoscopy with artificial intelligence training and suggest that the mechanism of ICG retention in cancer cells is related to intracellular nitric oxide concentration.

Substituent directed cellular imaging in the 800-850 nm range with BF2-azadipyrromethene fluorophores

Three bis(anilino)-substituted NIR-AZA fluorophores have been designed, synthesized and tested to bridge the availability gap of molecular fluorophores for live-cell microscopy imaging in the 800-850 nm spectral range. The concise synthetic route allows for the later stage introduction of three tailored peripheral substituents which guides the sub-cellular localization and imaging. Live-cell fluorescence imaging of lipid droplets, plasma membrane and cytosolic vacuoles was successfully achieved. Photophysical and internal charge transfer (ICT) properties of each fluorophore were examined through solvent studies and analyte responses.

Combinatorial therapeutic approaches of photodynamic therapy and immune checkpoint blockade for colon cancer treatment

Photodynamic therapy (PDT) has shown impressive therapeutic effects on various types of cancers by reactive oxygen species (ROS) generation and induction of immune responses. However, under certain conditions, the immune responses induced by PDT are not always sufficient to eradicate the remaining tumor cells. On the other hand, the photosensitizer indocyanine green (ICG) can mediate PDT under near-infrared (NIR) illumination, thereby enhancing the penetration depth of the excitation light into the tumor. We found that ICG is rapidly taken up in vitro by colorectal MC38 and CT26 tumor cells and it promotes PDT-mediated cell-killing effects. Our results furthermore revealed that ICG induces immunogenic cell death (ICD), as dendritic cells (DCs) were found to engulf ICG-PDT-treated tumor cells and undergo phenotypic maturation. ICG accumulated in tumors 2 h after administration, as measured by fluorescence and photoacoustic imaging. Considering the advantages of ICG as a photosensitizer, we sought to design a therapy that combines PDT and immune checkpoint blockade to maximize tumor control. To this end, a 25% thermosensitive polymer 407 hydrogel was included as a co-delivery platform for this treatment scheme. NIR-PDT under 808 nm irradiation in combination with cytotoxic T-lymphocyte-associated protein 4 (CTLA4)/programmed death-ligand 1 (PD-L1) checkpoint blockade prolonged survival rate of colorectal tumor-bearing mice by inducing a series of immune responses, like the phagocytosis of tumor debris by macrophages and DCs, and induction of acute inflammation, leukocyte infiltration, maturation and activation of DCs. Altogether, our work presents a NIR-triggered PDT strategy in combination with immune checkpoint blockade. Compared to a single treatment, the combination treatment increased efficiency to inhibit solid tumor growth and improved the survival rate of tumor-bearing mice.

Progresses in Fluorescence Imaging Guidance for Bone and Soft Tissue Sarcoma Surgery

R0 surgical resection is the preferred treatment for bone and soft tissue sarcoma. However, there is still a lack of precise technology that can visualize bone and soft tissue sarcoma during surgery to assist the surgeon in judging the tumor surgical boundary. Fluorescence imaging technology has been used in the diagnosis of cancer. It is a simple and essentially safe technique that takes no additional time during the operation. Intraoperative fluorescence imaging has potential application prospects in assisting the surgeons in judging the tumor boundary and improving the accuracy of surgical resection. This review mainly starts with clinical studies, animal experimentation, and newly designed probes of intraoperative fluorescence imaging of bone and soft tissue sarcoma, to appraise the application prospects of fluorescence imaging technology in bone and soft tissue sarcoma.

Photoacoustic nanodroplets for oxygen enhanced photodynamic therapy of cancer

Photodynamic therapy (PDT) is a well-known cancer therapy that utilizes light to excite a photosensitizer and generate cytotoxic reactive oxygen species (ROS). The efficacy of PDT primarily depends on the photosensitizer and oxygen concentration in the tumor. Hypoxia in solid tumors promotes treatment resistance, resulting in poor PDT outcomes. Hence, there is a need to combat hypoxia while delivering sufficient photosensitizer to the tumor for ROS generation. Here we showcase our unique theranostic perfluorocarbon nanodroplets as a triple agent carrier for oxygen, photosensitizer, and indocyanine green that enables light triggered spatiotemporal delivery of oxygen to the tumors. We evaluated the characteristics of the nanodroplets and validated their ability to deliver oxygen via photoacoustic monitoring of blood oxygen saturation and subsequent PDT efficacy in a murine subcutaneous tumor model. The imaging results were validated with an oxygen sensing probe, which showed a 9.1 fold increase in oxygen content inside the tumor, following systemic administration of the nanodroplets. These results were also confirmed with immunofluorescence. In vivo studies showed that nanodroplets held higher rates of treatment efficacy than a clinically available benzoporphyrin derivative formulation. Histological analysis showed higher necrotic area within the tumor with perfluoropentane nanodroplets. Overall, the photoacoustic nanodroplets can significantly enhance image-guided PDT and has demonstrated substantial potential as a valid theranostic option for patient-specific photodynamic therapy-based treatments.

Digital dynamic discrimination of primary colorectal cancer using systemic indocyanine green with near-infrared endoscopy

As indocyanine green (ICG) with near-infrared (NIR) endoscopy enhances real-time intraoperative tissue microperfusion appreciation, it may also dynamically reveal neoplasia distinctively from normal tissue especially with video software fluorescence analysis. Colorectal tumours of patients were imaged mucosally following ICG administration (0.25 mg/kg i.v.) using an endo-laparoscopic NIR system (PINPOINT Endoscopic Fluorescence System, Stryker) including immediate, continuous in situ visualization of rectal lesions transanally for up to 20 min. Spot and dynamic temporal fluorescence intensities (FI) were quantified using ImageJ (including videos at one frame/second, fps) and by a bespoke MATLAB® application that provided digitalized video tracking and signal logging at 30fps (Fluorescence Tracker App downloadable via MATLAB® file exchange). Statistical analysis of FI-time plots compared tumours (benign and malignant) against control during FI curve rise, peak and decline from apex. Early kinetic FI signal measurement delineated discriminative temporal signatures from tumours (n = 20, 9 cancers) offering rich data for analysis versus delayed spot measurement (n = 10 cancers). Malignant lesion dynamic curves peaked significantly later with a shallower gradient than normal tissue while benign lesions showed significantly greater and faster intensity drop from apex versus cancer. Automated tracker quantification efficiently expanded manual results and provided algorithmic KNN clustering. Photobleaching appeared clinically irrelevant. Analysis of a continuous stream of intraoperatively acquired early ICG fluorescence data can act as an in situ tumour-identifier with greater detail than later snapshot observation alone. Software quantification of such kinetic signatures may distinguish invasive from non-invasive neoplasia with potential for real-time in silico diagnosis.

Metal-Free Organo-Theranostic Nanosystem with High Nitroxide Stability and Loading for Image-Guided Targeted Tumor Therapy

The desire for all-organic-composed nanoparticles (NPs) of considerable biocompatibility to simultaneously diagnose and treat cancer is undeniably interminable. Heretofore, metal-based agents dominate the landscape of available magnetic resonance imaging (MRI) contrast agents and photothermal therapeutic agents, but with associated metal-specific downsides. Here, an all-organic metal-free nanoprobe, whose appreciable biocompatibility is synergistically contributed by its tetra-organo-components, is developed as a viable alternative to metal-based probes for MRI-guided tumor-targeted photothermal therapy (PTT). This rationally entails a glycol chitosan (GC)-linked polypyrrole (PP) nanoscaffold that provides abundant primary and secondary amino groups for amidation with the carboxyl groups in a nitroxide radical (TEMPO) and folic acid (FA), to obtain GC-PP@TEMPO-FA NPs. Advantageously, the appreciably benign GC-PP@TEMPO-FA features high nitroxide loading (r₁ = 1.58 mM^-1 s^-1) and in vivo nitroxide-reduction resistance, prolonged nitroxide-systemic circulation times, appreciable water dispersibility, potential photodynamic therapeutic and electron paramagnetic resonance imaging capabilities, considerable biocompatibility, and ultimately achieves a 17 h commensurate MRI contrast enhancement. Moreover, its GC component conveys a plethora of PP to tumor sites, where FA-mediated tumor targeting enables substantial NP accumulation with consequential near-complete tumor regression within 16 days in an MRI-guided PTT. The present work therefore promotes the engineering of organic-based metal-free biocompatible NPs in synergism, in furtherance of tumor-targeted image-guided therapy.

Surface modified NIR magnetic nanoprobes for theranostic applications

Objectives: Near-Infrared based imaging modalities integrated with thermotherapy can facilitate detection of cancer at early stages and mediate high-resolution image-guided hyperthermia. In this work, fluorescent iron oxide nanoparticles (FIO) have been developed possessing deep tissue penetrable NIR imaging and site-specific magnetic hyperthermia characteristics for the elimination of cancer cells.Methods: One-pot synthesis of amine-functionalized superparamagnetic iron oxide nanoparticles (HIO) were achieved using ethylenediamine (EDA) facilitated conjugation of indocyanine green (ICG) mediated by electrostatic interactions.Results: EDA acts as a capping and reducing agent to direct the structural growth of hydrophilic Fe₃O₄ nanocrystals with high saturation magnetization, specific absorption rate, and T₂ value of 118 emu/g, 329.8 ± 5.96 W/g, and 40.17 mM^-1s^-1, respectively. Here, Fe²⁺/Fe³⁺ of two was maintained to achieve magnetite nanocrystals contradictory to the gold standard ratio of 0.5 without additives for nucleation and growth. Developed FIO showed excellent cytocompatibility even at higher concentrations and on subjecting to magnetic hyperthermia reduced its survival percentage. FIO biodistribution in mice showed enhanced half-life than free ICG with preferential localization in the brain and liver.Conclusion: Developed FIO using a facile technique is a potential clinical alternative for cellular tracking, imaging, and hyperthermia.

A Hybrid Organo-Nanotheranostic Platform of Superlative Biocompatibility for Near-Infrared-Triggered Fluorescence Imaging and Synergistically Enhanced Ablation of Tumors

The quest for an all-organic nanosystem with negligible cytotoxicity and remarkable in vivo tumor theranostic capability is inescapably unending. Hitherto, the landscape of available photothermal agents is dominated by metal-based nanoparticles (NPs) with attendant in vivo negatives. Here, an all-organic-composed theranostic nanosystem with outstanding biocompatibility for fluorescence image-guided tumor photothermal therapy, and as a potential alternative to metal-based photothermal agents is developed. This is rationally achieved by compartmentalizing indocyanine green (ICG) in glycol chitosan (GC)-polypyrrole (PP) nanocarrier to form hybrid ICG@GC-PP NPs (≈65 nm). The compartmentalization strategy, alongside the high photothermal conversion ability of PP jointly enhances the low photostability of free ICG. Advantageously, ICG@GC-PP is endowed with an impeccable in vivo performance by the well-known biocompatibility track records of its individual tri organo-components (GC, PP, and ICG). As a proof of concept, ICG@GC-PP NPs enables a sufficiently prolonged tumor diagnosis by fluorescence imaging up to 20 h post-injection. Furthermore, owing to the complementary heating performances of PP and ICG, ICG@GC-PP NPs-treated mice by one-time near-infrared irradiation exhibit total tumor regression within 14 days post-treatment. Therefore, leveraging the underlying benefits of this study will help to guide the development of new all-organic biocompatible systems in synergism, for safer tumor theranostics.

Fluorescence tumor imaging by i.v. administered indocyanine green in a mouse model of colitis-associated colon cancer

Fluorescence tumor imaging using exogenous fluorescent tumor‐targeting agents has potential to improve early tumor detection. The fluorescent contrast agent indocyanine green (ICG) is used in medical diagnostics. The aim of the present study is to investigate the tumor imaging capability and the imaging mechanism of i.v. administered ICG in a mouse model of colitis‐associated colon cancer. To do this, an azoxymethane/dextran sodium sulfate‐induced colon cancer mouse model was used. Ex vivo imaging experiments were carried out 1 hour after i.v. injection of ICG. The ICG fluorescence was observed in the colon tumor tissues, with sufficient tumor to normal tissue ratio, correlating with tumor malignancy. In the tumor tissues, ICG fluorescence was localized in the vascular interstitial tissue. Immunofluorescence microscopy revealed that tumor cells formed tight junctions normally, suggesting an inability of tumor cellular uptake of ICG. In contrast, tumor tissues increased the CD31‐immunoreactive endothelial cell area, and accumulated stromal cells immunoreactive for COX‐2 and tumor cell population immunoreactive for inducible nitric oxide synthase. In vivo vascular permeability assay revealed that prostaglandin E₂ promoted the endothelial cell permeability of ICG. In conclusion, our data indicated that fluorescence contrast‐enhanced imaging following i.v. administered ICG can be applied to the detection of colon tumors in a mouse colitis‐associated colon cancer model. The tumor tissue preference of ICG in the present model can be attributed to the enhanced vascular leakage of ICG involving inflammatory mediators, such as COX‐2 and inducible nitric oxide synthase, in conjunction with increased tumor vascularity.