Indocyanine green: physicochemical factors affecting its fluorescence in vivo

Intraoperative bladder visualization by indocyanine green filling and subsequent washout in endoscopic hysterectomy: ICG-Washout method

INTRODUCTION

Despite a potential risk of bladder injury in laparoscopic hysterectomy (LH) and robot-assisted LH (RaLH), an intraoperative method for delineating the entire bladder with indocyanine green (ICG) has not been established.

METHODS

We conducted a preliminary experiment using porcine bladders to verify the appropriate amount of ICG for intraoperative bladder visualization. Afterward, intraoperative bladder visualization was tried in LH and RaLH in two patients suspected of having adhesions around the bladder after previous abdominal surgery.

RESULTS

Although near-infrared (NIR) fluorescence was well observed through the wall of the porcine bladder filled with ICG solution at a concentration of 0.024 mg/mL, the subsequent replacement of the ICG solution with saline made the NIR fluorescence brighter. In both patients, the bladder was successfully delineated by NIR fluorescence after filling the bladder with ICG solution and the subsequent washout with saline.

CONCLUSION

The ICG-Washout method for locating the bladder by NIR fluorescence could be useful in LH and RaLH.

Indocyanine Green-Labeled Platelets for Survival and Recovery Studies

Introduction

Before being implemented in daily clinical routine, new production strategies for platelet concentrates (PCs) must be validated for their efficacy. Besides in vitro testing, the establishment of new methods requires the labeling of platelets for in vivo studies of platelets' survival and recovery. Indocyanine green (ICG) is a Food and Drug Administration-approved near-infrared (NIR) fluorescent dye for diagnostic use in vivo, suitable for non-radioactive direct cell labeling of platelets.

Methods

Platelets from PCs in storage solutions with different plasma concentrations were labeled with ICG up to concentrations of 200 μm. Whole blood (WB) was used as an ex vivo matrix to monitor the labeling stability of ICG-labeled platelets. The impact of labeling processes was assessed by the quantification of CD62P expression and PAC-1 binding as platelet function markers. Platelet aggregation was analyzed by light transmission aggregometry. ICG-labeling efficiency and stability of platelets were determined by flow cytometry.

Results

Platelets from PCs could be successfully labeled with 10 μm ICG after 1 and 4 days of storage. The best labeling efficiency of 99.8% ± 0.1% (immediately after labeling) and 81% ± 6.2% (after 24 h incubation with WB) was achieved by plasma replacement by 100% platelet additive solution for the labeling process. Since the washing process slightly impaired platelet function, ICG labeling itself did not affect platelets. Immediately after the ICG-labeling process, plasma was re-added, resulting in a recovered platelet function.

Conclusion

We developed a Good Manufacturing Practice compatible protocol for ICG fluorescent platelet labeling suitable for survival and recovery studies in vivo as a non-radioactive labeling alternative.

Azaphosphinate Dyes: A Low Molecular Weight Near-Infrared Scaffold for Development of Photoacoustic or Fluorescence Imaging Probes

Near-infrared (NIR) dyes are desirable for biological imaging applications including photoacoustic (PA) and fluorescence imaging. Nonetheless, current NIR dyes are often plagued by relatively large molecular weights, poor water solubility, and limited photostability. Herein, we provide the first examples of azaphosphinate dyes which display desirable properties such as low molecular weight, absorption/emission above 750 nm, and remarkable water solubility. In PA imaging, an azaphosphinate dye exhibited a 4.1-fold enhancement in intensity compared to commonly used standards, the ability to multiplex with existing dyes in whole blood, imaging depths of 2.75 cm in a tissue model, and contrast in mice. An improved derivative for fluorescence imaging displayed a >10-fold reduction in photobleaching in water compared to the FDA-approved indocyanine green dye and could be visualized in mice. This new dye class provides a robust scaffold for the development of photoacoustic or NIR fluorescence imaging agents.

Optimizing Indocyanine Green Dosage for Near-Infrared Fluorescence Perfusion Assessment in Bowel Anastomosis: A Prospective, Systematic Dose-Ranging Study

BACKGROUND

Indocyanine green (ICG) near-infrared fluorescence (NIRF) has emerged as a promising technique for visualizing tissue perfusion. However, within the wide range of dosages and imaging conditions currently being applied, the optimal dosage of ICG remains unclear. This study aimed to investigate the feasibility and implications of implementing lower dosages of ICG than commonly used for visual and quantitative perfusion assessment in a standardized setting.

METHODS

A prospective single-center cohort study was conducted on patients undergoing ileostomy reversal by hand-sewn anastomosis. ICG-NIRF visualization was performed before (T1) and after (T2) anastomosis with one of four different dosages of ICG (5 mg, 2.5 mg, 1.25 mg, or 0.625 mg) and recorded. Postoperatively, each visualization was evaluated for signal strength, completeness, and homogeneity of fluorescence. Additionally, perfusion graphs were generated by a software-based quantitative perfusion assessment, allowing an analysis of perfusion parameters. Statistical analysis comparing the effect of the investigated dosages on these parameters was performed.

RESULTS

In total, 40 patients were investigated. Visual evaluation demonstrated strong, complete, and homogeneous fluorescence signals across all dosages. Perfusion graph assessment revealed a consistent shape for all dosages (ingress followed by egress phase). While the average signal intensity decreased with dosage, it was sufficient to enable perfusion assessment even at the lowest dosages of 1.25 mg and 0.625 mg of ICG. The baseline intensity at T2 (the second intraoperative visualization) significantly decreased with dosage. The slope of the egress phase steepened with decreasing dosage.

CONCLUSIONS

Lower dosages of ICG were sufficient for intraoperative perfusion assessment, while causing lower residual fluorescence and quicker egress in subsequent visualizations.

APOB100 transgenic mice exemplify how the systemic circulation content may affect the retina without altering retinal cholesterol input

Apolipoprotein B (APOB) is a constituent of unique lipoprotein particles (LPPs) produced in the retinal pigment epithelium (RPE), which separates the neural retina from Bruch's membrane (BrM) and choroidal circulation. These LPPs accumulate with age in BrM and contribute to the development of age-related macular degeneration, a major blinding disease. The APOB100 transgenic expression in mice, which unlike humans lack the full-length APOB100, leads to lipid deposits in BrM. Herein, we further characterized APOB100 transgenic mice. We imaged mouse retina in vivo and assessed chorioretinal lipid distribution, retinal sterol levels, retinal cholesterol input, and serum content as well as tracked indocyanine green-bound LPPs in mouse plasma and retina after an intraperitoneal injection. Retinal function and differentially expressed proteins were also investigated. APOB100 transgenic mice had increased serum LDL content and an additional higher density HDL subpopulation; their retinal cholesterol levels (initially decreased) became normal with age. The LPP cycling between the RPE and choroidal circulation was increased. Yet, LPP trafficking from the RPE to the neural retina was limited, and total retinal cholesterol input did not change. There were lipid deposits in the RPE and BrM, and retinal function was impaired. Retinal proteomics provided mechanistic insights. Collectively, our data suggested that the serum LDL/HDL ratio may not affect retinal pathways of cholesterol input as serum LPP load is mainly handled by the RPE, which offloads LPP excess to the choroidal circulation rather than neural retina. Different HDL subpopulations should be considered in studies linking serum LPPs and age-related macular degeneration.

Real-time fluorescence-guided adhesiolysis with indocyanine green in intra-abdominal surgery (with video)

Intra-abdominal adhesions have consistently posed a challenge for surgeons during procedures. This study aims to investigate the feasibility of utilizing indocyanine green (ICG) in conjunction with near-infrared imaging for the detection of intra-abdominal adhesions. In vitro, we analyzed factors affecting ICG fluorescence. We divided SD rats into groups to study ICG excretion in different digestive tract regions. Additionally, we reviewed surgical videos from previous cholecystectomy cases, categorizing them by ICG injection timing and assessing fluorescence imaging in various digestive tract regions. Finally, we preoperatively injected ICG into two cholecystectomized patients with abdominal adhesions, guiding intraoperative adhesiolysis with near-infrared fluorescence imaging. In vitro, we observed a significant influence of protein and ICG concentrations on ICG fluorescence intensity. Our rat experiments unveiled a strong and highly significant correlation (Kendall's tau-b = 1, P < 0.001) between the timing of ICG injection and the farthest point of intestinal fluorescence. A retrospective case analysis further validated this finding (Kendall's tau-b = 0.967, P < 0.001). Under the guidance of fluorescence navigation, two cholecystectomized patients with intra-abdominal adhesions successfully underwent adhesiolysis, and no postoperative complications occurred. The intraoperative combination of ICG with near-infrared fluorescence imaging effectively enhances the visibility of the liver, bile ducts, and various segments of the gastrointestinal tract while providing real-time navigation. This real-time fluorescence guidance has the potential to aid surgeons in the dissection of intra-abdominal adhesions.

Laparoscopic indocyanine green fluorescence imaging technique in rare type II cystic biliary atresia

In recent years, it has been reported that indocyanine green can be used for intraoperative navigation in Kasai surgery. However, there are no reports of its application in surgery for rare type II cystic biliary atresia. We report a girl presented with jaundice and light-colored stools. Laboratory tests showed impaired liver function with elevated serum bilirubin and bile acid levels. The abdominal ultrasound and MRCP suggested a common hepatic duct cyst. A diagnosis of choledochal cyst was suspected and biliary atresia could not be excluded. Conservative treatment was unsatisfactory. Laparoscopic exploration with indocyanine green fluorescence was performed on the 38th day of her life, and intraoperative diagnosis of type II CBA was made because the common hepatic duct cyst and its downstream anatomical structures did not show fluorescence. The postoperative bilirubin and bile acid levels decreased significantly and she was discharged two weeks after surgery. This result suggests that indocyanine green can be safely used in laparoscopic surgery for type II CBA, which not only helps in the differential diagnosis of CBA and choledochal cyst, but also confirms bile flow in real time.

Advancing glioblastoma imaging: Exploring the potential of organic fluorophore-based red emissive carbon dots

Over time, the interest in developing stable photosensitizers (PS) which both absorb and emit light in the red region (650 and 950 nm) has gained noticeable interest. Recently, carbon dots (CDs) have become the material of focus to act as a PS due to their high extinction coefficient, low cytotoxicity, and both high photo and thermal stability. In this work, a Federal and Drug Association (FDA) approved Near Infra-Red (NIR) organic fluorophore used for photo-imaging, indocyanine green (ICG), has been explored as a precursor to develop water-soluble red emissive CDs which possess red emission at 697 nm. Furthermore, our material was found to yield favorable red-imaging capabilities of glioblastoma stem-like cells (GSCs) meanwhile boasting low toxicity. Additionally with post modifications, our CDs have been found to have selectivity towards tumors over healthy tissue as well as crossing the blood-brain barrier (BBB) in zebrafish models.

Recent advances in the nanoarchitectonics of metal-organic frameworks for light-activated tumor therapy

Metal-organic frameworks (MOFs) have received extensive attention in tumor therapy because of their advantages, including large specific surface area, regular pore size, adjustable shape, and facile functionalization. MOFs are porous materials formed by the coordination bonding of metal clusters and organic ligands. This review summarized the most recent advancements in tumor treatment based on nMOFs. First, we discuss the classification of MOFs, which primarily include the series of isoreticular MOF (IRMOF), zeolitic imidazolate framework (ZIF), coordination pillared-layer (CPL), Materials of Institute Lavoisier (MIL), porous coordination network (PCN), University of Oslo (UiO) and Biological metal-organic frameworks (BioMOFs). Then, we discuss the use of nMOFs in antitumor therapy, including drug delivery strategies, photodynamic therapy (PDT), photothermal therapy (PTT), and combination therapy. Finally, the obstacles and opportunities in nMOFs are discussed.

Development of novel tracers for sentinel node identification in cervical cancer

Indocyanine green (ICG) with near-infrared (NIR) fluorescence imaging is used for lymphatic mapping. However, binding of ICG to blood proteins like serum albumin can shorten its retention time in sentinel lymph nodes (SLNs). Here, we investigated the efficacy and safety of a new fluorescence tracer comprising phytate and liposome (LP)-encapsulated ICG. Coadministration of phytate with LP containing phosphatidic acid promotes chelation mediated by Ca2+ in bodily fluids to enhance SLN retention. Uniformly sized LPs (100 nm) encapsulating ICG under conditions that minimized fluorescence self-quenching during storage were produced. We analyzed the behavior of the new tracer (ICG-phytate-LP) and control tracers (ICG and ICG-LP) in the lymphatic flow of mice in terms of lymph node retention time. We also tested lymphatic flow and safety in pigs that have a more human-like lymphatic system. LPs encapsulating stabilized ICG were successfully prepared. Mixing LP with phytate in the presence of Ca2+ increased both the particle size and negative surface charge. In mice, ICG-phytate-LP had the best lymph node retention, with a fluorescence intensity ratio that increased over 6 h and then decreased slowly over the next 24 h. In pigs, administration of ICG and ICG-phytate-LP resulted in no death or weight loss. There were no obvious differences between blood test results for the ICG and ICG-phytate-LP groups, and the overall safety was good. ICG-phytate-LP may be a useful new tracer for gynecological cancers that require time for lymph node identification due to a retroperitoneal approach.

Suppression of subgingival bacteria by antimicrobial photodynamic therapy using transgingival irradiation: A randomized clinical trial

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) is an effective method for eradicating bacteria in periodontal therapy. Standard aPDT requires the insertion of a laser tip into a periodontal pocket, in which the direction of irradiation is limited. Therefore, we devised an aPDT method that uses a transgingival near-infrared wavelength and indocyanine green-encapsulated and chitosan-coated nanoparticles as a photosensitizer.

METHODS

Forty patients undergoing supportive periodontal therapy, who had a single root tooth with a pocket of 5 mm or deeper, were used as subjects. In the test group, aPDT was performed by laser irradiation from outside the gingiva using photosensitizer nanoparticles. In the control group, pseudo aPDT without photosensitizer was performed by transgingival irradiation. Subgingival plaque was sampled from inside the pocket before, immediately after, and 1 week after treatment, and evaluated by colony counting and real-time polymerase chain reaction.

RESULTS

There were no significant differences in age, sex, periodontal pocket depth, and bleeding on probing between the test and control groups. Compared with the colony count before treatment, the count in the test group was significantly reduced immediately after treatment. The number of patients with colony reduction to ≤50% and ≤10% was significantly higher in the test group than in the control group. None of the participants reported pain, although one participant reported discomfort.

CONCLUSION

As a bacterial control method for residual pockets in patients undergoing supportive periodontal therapy, transgingival aPDT is a promising treatment strategy that is not generally accompanied by pain or discomfort.

DNA-Based Near-Infrared Voltage Sensors

Indocyanine green (ICG) is an FDA approved dye widely used for fluorescence imaging in research, surgical navigation, and medical diagnostics. However, ICG has a few drawbacks, such as concentration-dependent aggregation and absorbance, nonspecific cellular targeting, and rapid photobleaching. Here, we report a novel DNA-based nanosensor platform that utilizes monomers of ICG and cholesterol. Using DNA origami, we can attach ICG to a DNA structure, maintaining its concentration, preserving its near-infrared (NIR) absorbance, and allowing attachment of targeting moieties. We characterized the nanosensors' absorbance, stability in blood, and voltage sensing in vitro. This study presents a novel DNA-based ICG nanosensor platform for cellular voltage sensing for future in vivo applications.

Enhanced stability and photothermal efficiency of Indocyanine Green J-aggregates by nanoformulation with Calix[4]arene for photothermal therapy of cancers

Photothermal therapy (PTT) is a method of growing attention, owing to its controllable process, high efficiency and minimal side effect. Indocyanine Green (ICG) is as Food and Drug Administration (FDA) approved agent that stands on the frontline of further developments of PTT toward clinics. However, the applicability of ICG-mediated PTT is limited by the rapid in vivo clearance and photo-degradation of ICG. To improve those parameters, nanosized ICG-loaded nanoparticles (ICG-J/CX) were fabricated in this study by co-assembly of anionic ICG J-aggregates (ICG-J) with cationic tetraguanidinium calix[4]arene (CX). This very simple approach produces ICG-J/CX with a well-defined nanometer range size and a close to neutral charge. The nanoparticles demonstrate high photothermal conversion efficiency (PCE) and dramatically improved photostability, as compared with ICG. The in vitro cellular uptake and cytotoxicity studies further demonstrated that the ICG-J/CX nanoparticles enhance uptake and photothermal efficiency in comparison with ICG or non-formulated ICG-J, overall demonstrating that ICG-J/CX mediated photothermal therapy have significant potential for attaining cancer treatment.

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.

Optimizing Axial and Peripheral Substitutions in Si-Centered Naphthalocyanine Dyes for Enhancing Aqueous Solubility and Photoacoustic Signal Intensity

Photoacoustic imaging using external contrast agents is emerging as a powerful modality for real-time molecular imaging of deep-seated tumors. There are several chromophores, such as indocyanine green and IRDye800, that can potentially be used for photoacoustic imaging; however, their use is limited due to several drawbacks, particularly photostability. There is, therefore, an urgent need to design agents to enhance contrast in photoacoustic imaging. Naphthalocyanine dyes have been demonstrated for their use as photoacoustic contrast agents; however, their low solubility in aqueous solvents and high aggregation propensity limit their application. In this study, we report the synthesis and characterization of silicon-centered naphthalocyanine dyes with high aqueous solubility and near infra-red (NIR) absorption in the range of 850-920 nm which make them ideal candidates for photoacoustic imaging. A series of Silicon-centered naphthalocyanine dyes were developed with varying axial and peripheral substitutions, all in an attempt to enhance their aqueous solubility and improve photophysical properties. We demonstrate that axial incorporation of charged ammonium mesylate group enhances water solubility. Moreover, the incorporation of peripheral 2-methoxyethoxy groups at the α-position modulates the electronic properties by altering the π-electron delocalization and enhancing photoacoustic signal amplitude. In addition, all the dyes were synthesized to incorporate an N-hydroxysuccinimidyl group to enable further bioconjugation. In summary, we report the synthesis of water-soluble silicon-centered naphthalocyanine dyes with a high photoacoustic signal amplitude that can potentially be used as contrast agents for molecular photoacoustic imaging.

Imaging of Indocyanine Green-Human Serum Albumin (ICG-HSA) Complex in Secreted Protein Acidic and Rich in Cysteine (SPARC)-Expressing Glioblastoma

Glioblastoma is the most common and fatal primary glioma and has a severe prognosis. It is a challenge for neurosurgeons to remove brain tumor tissues completely by resection. Meanwhile, fluorescence-guided surgery (FGS) is a technique used in glioma surgery to enhance the visualization of tumor edges to clarify the extent of tumor resection. Indocyanine green (ICG) is the only FDA-approved NIR fluorescent agent. It non-covalently binds to human serum albumin (HSA). Secreted protein acidic and rich in cysteine (SPARC) is an extracellular glycoprotein expressed in gliomas and binds to albumin, suggesting that it plays an important role in tumor uptake of the ICG-HSA complex. Here we demonstrate the binding properties of HSA or SPARC to ICG using surface plasmon resonance and saturation binding assay. According to in vitro and in vivo studies, the results showed that the uptake of ICG-HSA complex was higher in SPARC-expressing glioblastoma cell line and tumor region compared with the uptake of free ICG. Here, we visualized the SPARC-dependent uptake of ICG and ICG-HSA complex in U87MG. Our results demonstrated that the ICG-HSA complex is likely to be used as an efficient imaging agent targeting SPARC-expressing tumors, especially glioblastoma.

NIR Fluorescence lifetime macroscopic imaging with a novel time-gated SPAD camera

SwissSPAD3 is the latest of a family of widefield time-gated SPAD imagers developed for fluorescence lifetime imaging (FLI) applications. Its distinctive features are (i) the ability to define shorter gates than its predecessors (width W < 1 ns), (ii) support for laser repetition rates up to at least 80 MHz and (iii) a dual-gate architecture providing an effective duty cycle of 100%. We present widefield macroscopic FLI measurements of short lifetime NIR dyes, analyzed using the phasor approach. The results are compared with those previously obtained with SwissSPAD2 and to theoretical predictions.

Photo-sonodynamic therapy mediated with OLI_NPs to induce HPV16E7-specific immune response and inhibit cervical cancer in a Tc-1-grafted murine model

Cervical carcinoma is the fourth most common gynecological cancer. Here we reported the synthesis of oxygen-carried and lipopolysaccharide (LPS)/ indocyanine green (ICG)-loaded nanoparticles (OLI_NPs) for photo-sonodynamic therapy (PSDT) mediated combination therapy to induce systemic antitumor immune responses. We effectively built a new nanoparticle system, a multifunctional nanoagent that integrated the ability of dual-model imaging and therapy for tumors. In this study, we confirmed that OLI_NPs can act as a multifunctional platform that enables not only to diagnose tumors conveniently but also to efficiently provide treatment of in situ tumors, permitting simultaneous dual-mode imaging and localization of the therapy in combination with PSDT-mediated drug release. Furthermore, our combined strategy could effectively depress the tumor development and extend mouse life by the combination of inducing immunogenic cell death (ICD) with encapsulated LPS. In conclusion, combining therapy of OLI_NPs plus PSDT can induce anti-tumor immune responses and tumor antigen-specific immunity in a common TC-1 graft tumor model. Therefore, this combination therapy is a viable technique for cervical cancer treatment.

Optical Characteristics of Indocyanine Green J-Aggregates Induced by Cisplatin for Phototheranostic Applications

The development of an optical system for combinatorial theranostics is of significant interest. Clinical translation of such theranostic agents need to cross several barriers. Herein, we have developed a facile method for the preparation of J-aggregates using FDA approved agents, namely, NIR fluorophore indocyanine green (ICG) and a chemotherapeutic drug, cisplatin (CDDP), which induces ICG to form indocyanine green J-aggregates (IJAs). The formation of IJAs has been characterized by the formation of a new absorption peak centered at ∼896 nm. The existing methods to synthesize IJAs have used several harsh reaction conditions, such as elevated temperatures, for a prolonged time duration (∼60 days). To the best of our knowledge, for the first time, we have reported the formation of IJAs assisted by CDDP at 37 °C temperature within 12 h. The presence of CDDP in ICG favors IJA formation and thereby reduces the harshness of the reaction conditions in the conventionally followed protocols. Moreover, the presence of CDDP can facilitate photoactivated combinatorial therapy. The as synthesized IJA optical system has superior properties to those of free ICG, in terms of diagnostic and therapeutic capabilities (being activatable at ∼896 nm wavelength, which can achieve deeper tissue penetration) and excellent optical and storage stability. The facile synthesis proposed along with CDDP incorporation makes the optical system a clinically relevant one-component theranostic agent.

Acute mesenteric ischemia: updated guidelines of the World Society of Emergency Surgery

Acute mesenteric ischemia (AMI) is a group of diseases characterized by an interruption of the blood supply to varying portions of the intestine, leading to ischemia and secondary inflammatory changes. If untreated, this process may progress to life-threatening intestinal necrosis. The incidence is low, estimated at 0.09-0.2% of all acute surgical admissions, but increases with age. Although the entity is an uncommon cause of abdominal pain, diligence is required because if untreated, mortality remains in the range of 50%. Early diagnosis and timely surgical intervention are the cornerstones of modern treatment to reduce the high mortality associated with this entity. The advent of endovascular approaches in parallel with modern imaging techniques is evolving and provides new treatment options. Lastly, a focused multidisciplinary approach based on early diagnosis and individualized treatment is essential. Thus, we believe that updated guidelines from World Society of Emergency Surgery are warranted, in order to provide the most recent and practical recommendations for diagnosis and treatment of AMI.

Indocyanine green conjugated phototheranostic nanoparticle for photodiagnosis and photodynamic reaciton

BACKGROUND

Phototheranostics represents a highly promising paradigm for cancer therapy, although selecting an appropriate optical imager and sensitizer for clinical use remains challenging.

METHODS

Liposomally formulated phospholipid-conjugated indocyanine green, denoted as LP-iDOPE, was developed as phototheranostic nanoparticle and its cancer imaging-mediated photodynamic reaction, defined as the immune response induced by photodynamic and photothermal effects, was evaluated with a near-infrared (NIR)-light emitting diode (LED) light irradiator.

RESULTS

Using in vivo NIR fluorescence imaging, we demonstrated that LP-iDOPE was selectively delivered to tumor sites with high accumulation and a long half-life. Following low-intensity NIR-LED light irradiation on the tumor region of LP-iDOPE accumulated, effector CD8⁺ T cells were activated at the secondary lymphoid organs, migrated, and subsequently released cytokines including interferon-γ and tumor necrosis factor-α, resulting in effective tumor regression.

CONCLUSIONS

Our anti-cancer strategy based on tumor-specific LP-iDOPE accumulation and low-intensity NIR-LED light irradiation to the tumor regions, i.e., photodynamic reaction, represents a promising approach to noninvasive cancer therapy.

Fluorescent Tracers for In Vivo Imaging of Lymphatic Targets

The lymphatic system continues to gain importance in a range of conditions, and therefore, imaging of lymphatic vessels is becoming more widespread for research, diagnosis, and treatment. Fluorescent lymphatic imaging offers advantages over other methods in that it is affordable, has higher resolution, and does not require radiation exposure. However, because the lymphatic system is a one-way drainage system, the successful delivery of fluorescent tracers to lymphatic vessels represents a unique challenge. Each fluorescent tracer used for lymphatic imaging has distinct characteristics, including size, shape, charge, weight, conjugates, excitation/emission wavelength, stability, and quantum yield. These characteristics in combination with the properties of the target tissue affect the uptake of the dye into lymphatic vessels and the fluorescence quality. Here, we review the characteristics of visible wavelength and near-infrared fluorescent tracers used for in vivo lymphatic imaging and describe the various techniques used to specifically target them to lymphatic vessels for high-quality lymphatic imaging in both clinical and pre-clinical applications. We also discuss potential areas of future research to improve the lymphatic fluorescent tracer design.

Optimization and use of near infrared imaging to guide lymph node collection in rhesus macaques (Macaca mulatta)

Background

Identification of lymph nodes (LNs) draining a specific site or in obese macaques can be challenging.

Methods

Indocyanine Green (ICG) was administered intradermal (ID), intramuscular, in the oral mucosa, or subserosal in the colon followed by Near Infrared (NIR) imaging.

Results

After optimization to maximize LN identification, intradermal ICG was successful in identifying 50–100% of the axillary/inguinal LN at a site. Using NIR, collection of peripheral and mesenteric LNs in obese macaques was 100% successful after traditional methods failed. Additionally, guided collection of LNs draining the site of intraepithelial or intramuscular immunization demonstrated significantly increased numbers of T follicular helper (Tfh) cells in germinal centers of draining compared to nondraining LNs.

Conclusion

These imaging techniques optimize our ability to evaluate immune changes within LNs over time, even in obese macaques. This approach allows for targeted serial biopsies that permit confidence that draining LNs are being harvested throughout the study.

Qualitative features of esophageal fluorescence angiography and anastomotic outcomes in children

BACKGROUND

Indocyanine green (ICG) is commonly used to assess perfusion, but quality defining features are lacking. We sought to establish qualitative features of esophageal ICG perfusion assessments, and develop an esophageal anastomotic scorecard to risk-stratify anastomotic outcomes.

METHODS

Single institution, retrospective analysis of children with an intraoperative ICG perfusion assessment of an esophageal anastomosis. Qualitative perfusion features were defined and a perfusion score developed. Associations between perfusion and clinical features with poor anastomotic outcomes (PAO, leak or refractory stricture) were evaluated with logistic and time-to-event analyses. Combining significant features, we developed and tested an esophageal anastomotic scorecard to stratify PAO risk.

RESULTS

From 2019 to 2021, 53 children (median age 7.4 months) underwent 55 esophageal anastomoses. Median (IQR) follow-up was 14 (10-19.9) months; mean (SD) perfusion score was 13.2 (3.4). Fifteen (27.3%) anastomoses experienced a PAO and had significantly lower mean perfusion scores (11.3 (3.3) vs 14.0 (3.2), p = 0.007). Unique ICG perfusion features, severe tension, and primary or rescue traction-induced esophageal lengthening [Foker] procedures were significantly associated with PAO on both logistic and Cox regression. The scorecard (range 0-7) included any Foker (+2), severe tension (+1), no arborization on either segment (+1), suture line hypoperfusion >twice expected width (+2), and segmental or global areas of hypoperfusion (+1). A scorecard cut-off >3 yielded a sensitivity of 73% and specificity of 93% (AUC 0.878 [95%CI 0.777 to 0.978]) in identifying a PAO.

CONCLUSIONS

A scoring system comprised of qualitative ICG perfusion features, tissue quality, and anastomotic tension can help risk-stratify esophageal anastomotic outcomes accurately.

LEVELS OF EVIDENCE

Diagnostic - II.

Near infra-red fluorescence imaging to demonstrate reflux in the superficial microvenous network of the leg

OBJECTIVE

Reflux within the superficial microvenous network may play a critical role in the development of skin changes which can be associated with chronic venous insufficiency. This study aimed to determine if near infra-red fluorescence (NIRF) imaging could be used to accurately determine superficial venous reflux in the leg.

METHODS

A total of nine limbs were examined ex vivo from patients undergoing limb amputation for peripheral arterial disease. Cannulation of the distal great saphenous vein was used to sequentially perform X-ray contrast enhanced venography, NIRF imaging and venous corrosion casts.

RESULTS

Fluorescence imaging visualised a range of different microvenous reflux patterns ex vivo, which were generally not evident by x-ray venography, but were consistent with retrograde resin vascular casts. These included both focal and diffuse regions of fluorescence within the skin and, consistent with previous observations, the vascular casts indicated that regions of venous reflux were typically associated with incompetent valves.

CONCLUSION

The findings from this study suggest a potential method for investigating early stage superficial venous disease, prior to the appearance of visible signs of advanced venous disease, such as skin changes. However, further studies are required to confirm the, in vivo, clinical utility of these observations.

Dual-functional alginate and collagen–based injectable hydrogel for the treatment of cancer and its metastasis

Background

Immunotherapies have been gaining attention for the prevention of cancer recurrence and metastasis. Cancer immunotherapy can induce memory cells to target cancer-specific antigens and, thus, selectively kill cancer cells. However, there are difficulties in inducing cancer antigen–specific immunity due to limited knowledge regarding cancer antigens. In this study, we synthesized a dual-functional hydrogel to induce antigen generation and immune activation.

Results

To elicit a cancer self-antigen–specific immune response, we synthesized an alginate-collagen–based injectable hydrogel, called thermally responsive hydrogel (pTRG), which was incorporated with indocyanine green and the immune stimulator polyinosinic:polycytidylic acid (poly I:C). pTRG was evaluated for its anticancer and anti-metastatic effects against CT-26 carcinoma and 4T1 breast tumor in mice by combining photothermal therapy (PTT) and immunotherapy. Near-infrared (NIR) irradiation promoted temperature elevation in pTRG, consequently exerting a therapeutic effect on mouse tumors. Lung metastasis was prevented in cured CT-26 tumor-injected mice following pTRG treatment via cancer antigen–specific T cell immunity. Moreover, pTRG successfully eliminated the original tumor in 4T1 tumor-bearing mice via PTT and protected them from lung metastasis. To further evaluate the carrier function of TRGs, different types of immunotherapeutic molecules were incorporated into TRGs, which led to the effective elimination of the first CT-26 tumor and the prevention of lung metastasis.

Conclusions

Our data demonstrate that TRG is a efficient material not only for treating primary tumors but also for preventing metastasis and recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01458-x.

Acute Mesenteric Ischemia

The surgical treatment of occlusive acute mesenteric ischemia (AMI) without revascularization is associated with an 80% overall mortality. Early diagnosis is crucial, and revascularization may reduce overall mortality in AMI by up to 50%. A diagnosis of AMI requires a high index of clinical suspicion and the collaborative effort of emergency department physicians, general and vascular surgeons, and radiologists. This article provides an overview of the etiology, physiology, evaluation, and management of acute mesenteric ischemia.

Antimicrobial Behavior and Cytotoxicity of Indocyanine Green in Combination with Visible Light and Water-Filtered Infrared A Radiation against Periodontal Bacteria and Subgingival Biofilm

The widespread increase of antibiotic resistance highlights the need for alternative treatments such as antimicrobial photodynamic therapy (aPDT). This study aimed to evaluate the antimicrobial behavior and cytotoxicity of aPDT with indocyanine green (ICG) in combination with visible light (Vis) and water-filtered infrared A (wIRA). Representative periodontal bacteria (Parvimonas micra, Atopobium riame, Slackia exigua, Actinomyces naeslundii, Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Prevotella nigrescens) and subgingival in situ biofilms from periodontal patients were treated with aPDT for 5 min. ICG was used at different concentrations (50–500 µg/mL) and the number of viable cells was determined in colony forming units (CFU). Untreated negative controls and 0.2% chlorhexidine as a positive control were also prepared. The cytotoxicity test on human keratinocytes in vitro was analyzed with the AlamarBlue assay after 5, 10, and 20 min, with four ICG concentrations, and at two temperatures (room temperature and 37 °C). The tested periodontal pathogens treated with aPDT were eliminated in a range between 1.2 and 6.7 log₁₀ CFU, except for A. naeslundii, which was killed at a lower range. The subgingival biofilm treated with aPDT expressed significant differences to the untreated controls except for at 300 µg/mL ICG concentration. The cytotoxicity was directly related to the concentration of ICG and irradiation time. These observations raise questions concerning the use of this specific aPDT as an adjuvant to periodontal treatments due to its possible toxicity towards human gingival cells.

Near infrared indocyanine green fluorescent cholangiography versus intraoperative cholangiography to improve safety in laparoscopic cholecystectomy for gallstone disease-a systematic review protocol

BACKGROUND

Laparoscopic cholecystectomy has become the standard surgical approach in the treatment of cholelithiasis. Diverse surgical techniques and different imaging modalities have been described to evaluate the biliary anatomy and prevent or early detect bile duct injuries. X-ray intraoperative cholangiography (IOC) and near infrared indocyanine green fluorescent cholangiography (NIR-ICG) are safe and feasible techniques to assess biliary anatomy. The aim of this systematic review will be to evaluate if NIR-ICG can visualize extrahepatic biliary anatomy more efficiently and safer than IOC in minimally invasive cholecystectomy for gallstone disease.

METHODS

Literature search will be performed via MEDLINE (PubMed), Embase, Scopus, the Cochrane Central Register of Controlled Trials, and Web of Science Core Collection from 2009 to present. All randomized controlled clinical trials and prospective non-randomized controlled trials which report on comparison of NIR-ICG versus IOC will be included. All patients over 18 years old who require elective or urgent minimally invasive cholecystectomy (undergoing NIR-ICG during this procedure) due to gallstone disease both acute and chronic will be included. Since BDI has a low incidence, the primary outcome will be the ability to visualize extrahepatic biliary anatomy and the time to obtain relevant images of these structures. Two researchers will individually screen the identified records, according to a list of inclusion and exclusion criteria. Bias of the studies will be evaluated with the Newcastle-Ottawa score for non-randomized studies and with The Cochrane Risk of Bias Tool for randomized controlled trials. Quality of evidence for all outcomes will be determined with the GRADE system. The data will be registered in a predesigned database. If selected studies are sufficiently homogeneous, we will perform a meta-analysis of reported results. In the event of a substantial heterogeneity, a narrative synthesis will be provided. Subgroup analysis will be used to investigate possible sources of heterogeneity.

DISCUSSION

Understanding the benefits of this technique is critical to ensuring policymakers can make informed decisions as to where preventive efforts should be focused regarding specific imaging techniques. If ICG is proven to be faster and non-invasive, its routine use could be encouraged.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020177991 .

Fluorescence Imaging Using Methylene Blue Sentinel Lymph Node Biopsy in Melanoma

Introduction

Fluorescence imaging of sentinel node biopsy in melanoma is a novel method. Both indocyanine green (ICG) and methylene blue (MB) have fluorescent properties. The aim of this study was to present, for the first time in a clinical series of patients, the possible usage of MB as a fluorescent dye for sentinel node biopsy during surgery for melanoma.

Material and methods

Twenty patients with skin melanoma, who were candidates for sentinel node biopsy were enrolled in our study. All patients underwent simultaneous use of standard nanocolloid and blue dye. Transcutaneous visualization of the sentinel node, visualization of lymphatic channels as well as sentinel node fluorescent visualization were all measured. We also performed calculations of Signal to Background ratios (SBR).

Results

In 15% (3/20) of patients, the fluorescent sentinel node was visible through the skin. The median SBR for the sentinel node visualization by fluorescence was 3.15 (range, 2.7–3.5). Lymphatic channels were visible in lymphatic tissue via fluorescence before visualization by the naked eye in 4 patients (20%). The median SBR ratio was 3.69 (range, 2.7–4.2). Sentinel nodes were visible by fluorescence in 13 cases (65%). The median SBR ratio was 2.49 (range, 1.5–5.7). No factors were found to be associated with fluorescent MB visualization of a sentinel node during biopsy.

Conclusion

This is the first clinical study presenting the usefulness of fluorescent sentinel node biopsy in melanoma patients using MB as a fluorophore. Further studies are necessary to provide methods for its’ clinical implementation.

Indocyanine Green Angiography Features in Acute Syphilitic Posterior Placoid Chorioretinitis

PURPOSE

Acute syphilitic posterior placoid chorioretinitis (ASPPC) is a rare clinical manifestation of ocular syphilis. The cause of the placoid lesion is still up for debate but could be caused by an impaired choriocapillaris perfusion. However, less attention has been paid to the hypofluorescence of the plaque on late-phase indocyanine green angiography (ICGA). The aim of this study was to comprehensively analyze multimodal imaging findings in patients with ASPPC and to highlight the value of ICGA for the diagnosis of ASPPC.

DESIGN

Retrospective observational case study.

METHODS

The medical records of patients with uveitis who consulted our tertiary center between 2012 and December 2015 were reviewed. Patients who were diagnosed with uveitis related to syphilis infection with posterior placoid lesions seen on multimodal imaging were included. We compared the aspect of ASPPC on fundus color photography, blue autofluorescence, fluorescein angiography, optical coherence tomography, and early-, mid- and late-phase ICGA.

RESULTS

Fifteen eyes of 12 patients were included in the study. Hypofluorescent plaques were seen on late-phase ICGA in all eyes, corresponding to the placoid lesions visible on blue autofluorescence, while the choriocapillaris filling was normal on fluorescein angiography and ICGA. Within the plaques, optical coherence tomography showed ellipsoid zone disruptions, outer retinal disruptions, and retinal pigment epithelium granulations.

CONCLUSION

ASPPC could be caused by retinal pigment epithelium dysfunction secondary to an infectious or inflammatory disorder, characterized by a hypofluorescence visible only on late-phase ICGA, and resulting in photoreceptor disruptions. The RPE impairment was reversible after prompt antibiotic treatment.

The Impact of Temporal Variation in Indocyanine Green Administration on Tumor Identification During Fluorescence Guided Breast Surgery

BACKGROUND

On average, 21% of women in the USA treated with Breast Conserving Surgery (BCS) undergo a second operation because of close positive margins. Tumor identification with fluorescence imaging could improve positive margin rates through demarcating location, size, and invasiveness of tumors. We investigated the technique's diagnostic accuracy in detecting tumors during BCS using intravenous indocyanine green (ICG) and a custom-built fluorescence camera system.

METHODS

In this single-center prospective clinical study, 40 recruited BCS patients were sub-categorized into two cohorts. In the first 'enhanced permeability and retention' (EPR) cohort, 0.25 mg/kg ICG was injected ~ 25 min prior to tumor excision, and in the second 'angiography' cohort, ~ 5 min prior to tumor excision. Subsequently, an in-house imaging system was used to image the tumor in situ prior to resection, ex vivo following resection, the resection bed, and during grossing in the histopathology laboratory to compare the technique's diagnostic accuracy between the cohorts.

RESULTS

The two cohorts were matched in patient and tumor characteristics. The majority of patients had invasive ductal carcinoma with concomitant ductal carcinoma in situ. Tumor-to-background ratio (TBR) in the angiography cohort was superior to the EPR cohort (TBR = 3.18 ± 1.74 vs 2.10 ± 0.92 respectively, p = 0.023). Tumor detection reached sensitivity and specificity scores of 0.82 and 0.93 for the angiography cohort and 0.66 and 0.90 for the EPR cohort, respectively (p = 0.1051 and p = 0.9099).

DISCUSSION

ICG administration timing during the angiography phase compared with the EPR phase improved TBR and diagnostic accuracy. Future work will focus on image pattern analysis and adaptation of the camera system to targeting fluorophores specific to breast cancer.

Intraoperative ICG-based fluorescence-angiography in head and neck reconstruction: Predictive value for impaired perfusion of free flaps

The aim of this study was to prove the hypothesis that intraoperative fluorescence-angiography using indocyanine-green (ICGFA) can be used to predict the occurrence of perfusion-associated complications following microvascular reconstruction. Consecutively perioperative data of patients who received microvascular reconstruction of the head and neck region and underwent ICGFA immediately after anastomosis was established were analyzed. The flow parameters analyzed in the investigation were (1) the baseline (Int_Min) and (2) peak intensity (Int_Max) of fluorescence, (3) the quotient of the two aforementioned parameters (F_max/min) as an expression of the relative total increase, (4) the absolute difference in the two parameters (Diff_Int) in terms of amplitude, (5) the duration of the intensity increase (T_Rise) until the peak, and (6) the percent intensity increase per second (Rise/sec_rel). Within the first 2 weeks postoperatively, every flap complication was documented. Subsequently, statistical analysis of the flap outcome was performed based on the flow parameters obtained intraoperatively. Data of 67 patients (male/female: 41/26) with an average age of 64 years (range 29-84 years) were analyzed. In 10 of these patients, postoperative perfusion-associated complications were observed (arterial/venous/microcirculatory: 4/3/3; p = 0.12). The analysis of the intraoperatively obtained flow parameters showed a significant difference in the ratio of maximum and minimum intensity in arterial pedicle perfusion (F_max/min) of patients with and without complications (with vs. without complications: 2.3 ± 1.0 vs. 5.0 ± 4.9; p < 0.01) and strong correlation of the mentioned parameter with the occurrence of perfusion-associated complications (odds ratio = 0.27; p = 0.01). The ratio of maximum and minimum intensity (F_max/min) is a predictor for postoperative venous stasis, arterial hypoperfusion and impaired microcirculation of a microvascular flap. Anastomoses with F_max/min <2.85 should be revised. However, a high technique sensitivity has to be considered, due to which sufficient hemostasis and reduction of motion artefacts have to be taken into account in order to obtain useable data.

Recent Advances in Molecular Imaging of Colorectal Tumors

BACKGROUND

Recent endoscopic studies have revealed that small colorectal tumors are often overlooked during colonoscopy, indicating that more sensitive detection methods are needed.

SUMMARY

Molecular imaging has received considerable attention as a new endoscopic technique with high sensitivity. It generally employs a fluorescence-labeled compound that specifically binds to a molecule on the tumor. Fluorescent probes for molecular imaging are largely classified as 2 types: a fluorescence-labeled antibody targeting a molecule specifically expressed on the tumor cell surface such as epidermal growth factor receptor or vascular endothelial growth factor (VEGF); and a fluorescence-labeled small molecule compound targeting a molecule specifically expressed in tumor cells including c-Met, glutathione S-transferase, γ-glutamyltranspeptidase, cathepsin, or endothelin A receptor. These probes successfully detected colorectal tumors in several animal studies. Moreover, 3 recent human clinical trials evaluating endoscopic molecular imaging for colorectal tumors have been reported. In one study, a Cy5-labeled synthetic peptide against c-Met was developed, and fluorescent endoscopic observation with this probe detected a greater number of colorectal adenomas than with white light observation. Another trial used IR800-labeled anti-VEGF antibody, which sensitively detected human colorectal adenomas by fluorescent endoscopy. Last, a fluorescent probe with synthetic peptide against BRAF-positive cells was able to visualize sessile serrated lesions. The fluorescent probes accumulated at very high levels in colorectal tumor cells but at lower levels in surrounding nonneoplastic mucosa. Key Messages: We expect that molecular imaging techniques with fluorescent probes will soon lead to the establishment of a highly sensitive endoscopic method for colorectal tumor detection.

Photophysical Properties of Indocyanine Green in the Shortwave Infrared Region

With the growing development of new contrast agents for optical imaging using near-infrared and shortwave infrared (SWIR) wavelengths, it is essential to have consistent bench-marks for emitters in these regions. Indocyanine green (ICG), a ubiquitous and FDA-approved organic dye and optical imaging agent, is commonly employed as a standard for photophysical properties and biological performance for imaging experiments at these wavelengths. Yet, its reported photophysical properties across organic and aqueous solvents vary greatly in the literature, which hinders its ability to be used as a consistent benchmark. Herein, we measure photophysical properties in organic and aqueous solvents using InGaAs detection (~950-1,700 nm), providing particular relevance for SWIR imaging.

Comparison of indocyanine green dye fluorescent cholangiography with intra-operative cholangiography in laparoscopic cholecystectomy: a meta-analysis

OBJECTIVE

To compare indocyanine green dye fluorescence cholangiography (ICG-FC) with intra-operative cholangiography (IOC) in minimal access cholecystectomy for visualization of the extrahepatic biliary tree.

BACKGROUND

Although studies have shown that ICG-FC is safe, feasible, and comparable to IOC to visualize the extrahepatic biliary tree, there is no comparative review.

METHODS

We searched The Embase, PubMed, Cochrane Library, and Web of Science databases up to 8 April 2020 for all studies comparing ICG-FC with IOC in patients undergoing minimal access cholecystectomy. The primary outcomes were percentage visualization of the cystic duct (CD), common bile duct (CBD), CD-CBD junction, and the common hepatic duct (CHD). We used RevMan v5.3 software to analyze the data.

RESULTS

Seven studies including 481 patients were included. Five studies, comprising 275 patients reported higher CD (RR = 0.90, p = 0.12, 95% CI 0.79-1.03, I² = 74%) and CBD visualization rates (RR = 0.82, p = 0.09, 95% CI 0.65-1.03, I² = 87%) by ICG-FC. Four studies, comprising 223 patients, reported higher CD-CBD junction visualization rates using ICG-FC compared to IOC (RR = 0.68, p = 0.06, 95% CI = 0.45-1.02, I² = 94%). Four studies, comprising 210 patients, reported higher CHD visualization rates using ICG-FC compared to IOC (RR = 0.58, p = 0.03, 95% CI 0.35-0.93, I² = 91%).

CONCLUSION

ICG-FC is safe, and it improves visualization of CHD.

Aptamer-Targeted Calcium Phosphosilicate Nanoparticles for Effective Imaging of Pancreatic and Prostate Cancer

Purpose

Accurate tumor identification and staging can be difficult. Aptamer-targeted indocyanine green (ICG)-nanoparticles can enhance near-infrared fluorescent imaging of pancreatic and prostate tumors and could improve early cancer detection. This project explored whether calcium-phosphosilicate nanoparticles, also known as NanoJackets (NJs), that were bioconjugated with a tumor-specific targeting DNA aptamer could improve the non-invasive detection of pancreatic and prostate tumors.

Methods

Using in vivo near-infrared optical imaging and ex vivo fluorescence analysis, DNA aptamer-targeted ICG-loaded NJs were compared to untargeted NJs for detection of tumors.

Results

Nanoparticles were bioconjugated with the DNA aptamer AP1153, which binds to the CCK-B receptor (CCKBR). Aptamer bioconjugated NJs were not significantly increased in size compared with unconjugated nanoparticles. AP1153-ICG-NJ accumulation in orthotopic pancreatic tumors peaked at 18 h post-injection and the ICG signal was cleared by 36 h with no evidence on uptake by non-tumor tissues. Ex vivo tumor imaging confirmed the aptamer-targeted NJs accumulated to higher levels than untargeted NJs, were not taken up by normal pancreas, exited from the tumor vasculature, and were well-dispersed throughout pancreatic and prostate tumors despite extensive fibrosis. Specificity for AP1153-NJ binding to the CCK-B receptor on pancreatic tumor cells was confirmed by pre-treating tumor-bearing mice with the CCK receptor antagonist proglumide. Proglumide pre-treatment reduced the in vivo tumoral accumulation of AP1153-NJs to levels comparable to that of untargeted NJs.

Conclusion

Through specific interactions with CCK-B receptors, tumor-targeted nanoparticles containing either ICG or rhodamine WT were well distributed throughout the matrix of both pancreatic and prostate tumors. Tumor-targeted NJs carrying various imaging agents can enhance tumor detection.

Near-Infrared Fluorescence Imaging and Photodynamic Therapy for Liver Tumors

Surgery with fluorescence equipment has improved to treat the malignant viscera, including hepatobiliary and pancreatic neoplasms. In both open and minimally invasive surgeries, optical imaging using near-infrared (NIR) fluorescence is used to assess anatomy and function in real time. Here, we review a variety of publications related to clinical applications of NIR fluorescence imaging in liver surgery. We have developed a novel nanoparticle (indocyanine green lactosome) that is biocompatible and can be used for imaging cancer tissues and also as a drug delivery system. To date, stable particles are formed in blood and have an ~10–20 h half-life. Particles labeled with a NIR fluorescent agent have been applied to cancer tissues by the enhanced permeability and retention effect in animals. Furthermore, this article reviews recent developments in photodynamic therapy with NIR fluorescence imaging, which may contribute and accelerate the innovative treatments for liver tumors.

NIR-II bioimaging of small organic molecule

In recent years, people have been actively exploring new imaging methods with high biological imaging performance because the clinical image definition and depth in vivo cannot meet the requirements of early diagnosis and prognosis. Based on the traditional near-infrared region I (NIR-I), the molecular probe of the near-infrared region II (NIR-II) is further explored and developed. In the NIR-II region due to the wavelength is longer than the NIR-I region can effectively reduce the molecular scattering, optical absorption of the organization, the organization of spontaneous fluorescence negligible, thus the NIR-II Fluorescence imaging (FI) can get deeper penetration depth, higher signal-to-background ratio (SBR) and better spatiotemporal resolution, FI in NIR-II region are an important and rapidly developing research region for future imaging. In the NIR-II fluorophore, small organic molecule fluorophore has attracted much attention because of its good biocompatibility and good pharmacokinetic properties. In this review, we briefly introduced the existing NIR-II organic small molecule fluorophores, and introduced the existing relatively mature methods for improving quantum yield and water solubility, and the small molecule dyes on FI of various improvement methods, also briefly introduces the small molecules of photoacoustic imaging (PAI), and a brief introduction of imaging-guided surgery (IGS) for some small organic molecules, finally, a reasonable prospect is made for the development of small organic molecules.

Extrahepatic biliary tract visualization using near-infrared fluorescence imaging with indocyanine green: optimization of dose and dosing time

BACKGROUND

The dose and dosing time of indocyanine green (ICG) vary among fluorescence cholangiography (FC) studies. The purpose of this prospective, randomized, exploratory clinical trial was to optimize the dose and dosing time of ICG.

METHODS

PubMed was searched to determine the optimal dose. To optimize the dosing time of ICG, a clinical trial was designed with two parts. The first part included patients with T tubes for more than 1 month. After the patient was injected with ICG, bile was collected at 10 time points to explore the change and trends of bile fluorescence intensity (FI). In addition, the results of the first experiment were used to setup a randomized controlled trial (RCT) that aimed to find the optimal dosing timing for ICG injections for laparoscopic cholecystectomy (LC). During surgery, imaging data were collected for analysis.

RESULTS

After performing a systematic review, the ICG injection dose for each patient in the clinical trial was 10 mg. Five patients were included in the first part of the study. Bile collected 8 h after ICG injection had a higher FI than bile collected at other time points (p < 0.05), and the FI of bile collected 20 h after ICG injection was nearly zero. In the second part of the experiment, 4 groups of patients (6 patients per group) were injected with 10 mg ICG at 8, 10, 12 and 14 h prior to surgery. The distribution of bile duct FI (p = 0.001), liver FI (p < 0.001), and common bile duct (CBD)-to-liver contrast (p = 0.001) were not the same in each group. Further analysis with the Bonferroni method revealed the following: (1) the FI of the CBD in the 8 h group was significantly different from that in the 14 h group (adjusted p < 0.001); (2) the liver FI of the 8 h group was higher than that of the 10 h group (adjusted p = 0.042) and the 14 h group (adjusted p < 0.001); and (3) the CBD-to-liver contrast of the 8 h group was lower than that of the 10 h group (adjusted p = 0.013) and the 14 h group (adjusted p = 0.001).

CONCLUSION

ICG FC enables the real-time identification of extrahepatic bile ducts. The optimal effect of FC can be achieved by performing 10 mg ICG injections 10 to 12 h prior to surgery.

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.

A Review of Endogenous and Exogenous Contrast Agents Used in Photoacoustic Tomography with Different Sensing Configurations

Optical-based sensing approaches have long been an indispensable way to detect molecules in biological tissues for various biomedical research and applications. The advancement in optical microscopy is one of the main drivers for discoveries and innovations in both life science and biomedical imaging. However, the shallow imaging depth due to the use of ballistic photons fundamentally limits optical imaging approaches’ translational potential to a clinical setting. Photoacoustic (PA) tomography (PAT) is a rapidly growing hybrid imaging modality that is capable of acoustically detecting optical contrast. PAT uniquely enjoys high-resolution deep-tissue imaging owing to the utilization of diffused photons. The exploration of endogenous contrast agents and the development of exogenous contrast agents further improve the molecular specificity for PAT. PAT’s versatile design and non-invasive nature have proven its great potential as a biomedical imaging tool for a multitude of biomedical applications. In this review, representative endogenous and exogenous PA contrast agents will be introduced alongside common PAT system configurations, including the latest advances of all-optical acoustic sensing techniques.

Near-Infrared Activated Cyanine Dyes As Agents for Photothermal Therapy and Diagnosis of Tumors

Today, it has become apparent that innovative treatment methods, including those involving simultaneous diagnosis and therapy, are particularly in demand in modern cancer medicine. The development of nanomedicine offers new ways of increasing the therapeutic index and minimizing side effects. The development of photoactivatable dyes that are effectively absorbed in the first transparency window of biological tissues (700-900 nm) and are capable of fluorescence and heat generation has led to the emergence of phototheranostics, an approach that combines the bioimaging of deep tumors and metastases and their photothermal treatment. The creation of near-infrared (NIR) light-activated agents for sensitive fluorescence bioimaging and phototherapy is a priority in phototheranostics, because the excitation of drugs and/or diagnostic substances in the near-infrared region exhibits advantages such as deep penetration into tissues and a weak baseline level of autofluorescence. In this review, we focus on NIR-excited dyes and discuss prospects for their application in photothermal therapy and the diagnosis of cancer. Particular attention is focused on the consideration of new multifunctional nanoplatforms for phototheranostics which allow one to achieve a synergistic effect in combinatorial photothermal, photodynamic, and/or chemotherapy, with simultaneous fluorescence, acoustic, and/or magnetic resonance imaging.

Development of Tumor-Targeted Indocyanine Green-Loaded Ferritin Nanoparticles for Intraoperative Detection of Cancers

Indocyanine green (ICG) is a fluorescent dye with a strong emission in the near-infrared spectral range that allows deep signal penetration and minimal interference of tissue autofluorescence. It has been employed in clinics for different applications, among which the more interesting is certainly near-infrared fluorescence image-guided surgery. This technique has found wide application in surgical oncology for lymph node mapping or for laparoscopic surgery. Despite ICG being useful for tracking loco-regional lymph nodes, it does not provide any information about cancer involvement of such lymph nodes or lymphatic vessels, lacking any tumor-targeting specificity. However, the clinical need in surgical oncology is not only a specific tracking of metastatic nodes but also the intraoperative detection of micrometastatic deposits. Here, we have exploited a nanotechnological solution to improve ICG usefulness by its encapsulation in H-ferritin (HFn) nanocages. They are natural protein-based nanoparticles that exhibit some very interesting features as delivery systems in oncological applications because they display specific tumor homing. We show that HFn loaded with ICG exhibits specific uptake into different cancer cell lines and is able to deliver ICG to the tumor more efficiently than the free dye in an in vivo model of TNBC. Our results pave the way for the application of ICG-loaded HFn in fluorescence image-guided surgery of cancer.

Fluorescence-guided surgery using indocyanine green in dogs with superficial solid tumours

BACKGROUND

Near-infrared fluorescence (NIRF) imaging is a relatively novel technique that can aid surgeons during intraoperative tumour identification.

METHODS

Nine canine oncology patients (five mammary gland tumours, three mast cell tumours and one melanoma) received intravenous indocyanine green (ICG). After 24 hours, tumours were resected and fluorescence intensities of tumours and surroundings were evaluated. Additional wound bed tissue was resected if residual fluorescence was present after tumour resection. Ex vivo, fluorescence-guided dissection was performed to separate tumour from surrounding tissue.

RESULTS

Intraoperative NIRF-guided tumour delineation was feasible in four out of nine dogs. Wound bed imaging after tumour removal identified nine additional fluorescent lesions, of which four contained tumour tissue. One of these four true positive in vivo lesions was missed by standard-of-care inspection. Ex vivo fluorescence-guided tumour dissection showed a sensitivity of 72 per cent and a specificity of 80 per cent in discriminating between tumour and surrounding tissue.

CONCLUSION

The value of ICG for intraoperative tumour delineation seems more limited than originally thought. Although NIRF imaging using ICG did identify remaining tumour tissue in the wound bed, a high false positive rate was also observed.

Intracholecystic administration of indocyanine green for fluorescent cholangiography during laparoscopic cholecystectomy-A two-case report

•

It is difficult to visualize extra-hepatic biliary anatomy clearly because of long-presence of ICG in liver when administered intravenously.

•

Intracholecystic ICG injection illuminates extra-hepatic biliary tree preferentially thus reducing background hepatic noise.

•

Surgeons can experience more satisfaction with the use of fluorescent cholangiography during laparoscopic cholecystectomy when the intracystic route of ICG administration is utilized.

Introduction

The utility of intracystic administration of indocyanine green for near-infrared fluorescent cholangiography in acute calculous cholecystitis initially treated with percutaneous transhepatic gallbladder drainage (PTGBD) was described in this report.

Presentation of case

Two cases who underwent near-infrared fluorescent cholangiography guided interval laparoscopic cholecystectomy two weeks post-PTGBD were studied retrospectively. Both patients were diagnosed with moderate acute calculous cholecystitis based on diagnostic criteria of the Tokyo guidelines. Two routes of indocyanine green administration were utilized during surgery, first through direct intracystic administration through PTGBD tube (5 ml of 12.5 mg ICG) to achieve critical view of safety and then intravenous administration (1 ml of 2.5 mg ICG) to visualize cystic artery.

Discussion

Both patients had critical view of safety visualized clearly with ICG with the operation time of 84 and 125 min in cases 1 and 2, respectively without any intra or postoperative complications.

Conclusion

In comparison with intravenous ICG administration, trans-PTGBD ICG route can provide better signal-to-noise ratio by avoiding hepatic fluorescence and thus increasing the bile duct to liver contrast. However, ICG may enter the lymphatic system through necrotic and inflammatory gallbladder mucosa, of which lymph spillage during gallbladder dissection can obscure the fluorescent view.

Fluorescence optical imaging for the detection of potential psoriatic arthritis in comparison to musculoskeletal ultrasound

OBJECTIVE

Comparison of fluorescence optical imaging (FOI) with grayscale (GS) and power Doppler ultrasound (PDUS) to detect joint inflammation in patients with confirmed or suspected psoriatic arthritis (PsA).

METHODS

Patients (n = 60) with psoriasis and tenderness and/or swelling of joints were separated into two groups: diagnosis confirmed by the treating dermatologist before the start of the study (n = 26), and suspected PsA (n = 34). GS/PDUS of the hand most clinically affected was performed with a dorsal/palmar view (wrist, MCP, PIP, DIP2-5). FOI examination was carried out in a standardized manner by analyzing the predefined Phases 1-3.

RESULTS

FOI was found to be more sensitive than ultrasound (US) for detection of inflammation in PIP/DIP joints (p = 0.035). Confirmed PsA patients showed more findings in FOI P2 and P3, while suspected PsA patients showed more findings in P1. In the confirmed PsA group, most involved joints were MCP joints, while in the suspected PsA group, more involved wrist joints and DIP joints (p = 0.006) were detected with FOI.

CONCLUSIONS

The differences between the confirmed and suspected groups indicate that FOI is helpful in the detection of early PsA since P1 may correspond to acute inflammation, whereas P2 and P3 enhancement reflect chronic inflammation. Fluorescence optical imaging might therefore be a novel diagnostic tool for early PsA diagnosis.

Mutual impact of clinically translatable near-infrared dyes on photoacoustic image contrast and in vitro photodynamic therapy efficacy

Photodynamic therapy (PDT), a spatially localized phototoxic therapy that involves irradiation of a photosensitizer (PS) with specific wavelengths of light, has shown exceptional promise in impacting cancer treatment outcomes, particularly oral cancer. To reduce PDT outcome variability, attempts toward image-guided personalized PDT are being pursued by monitoring PS uptake either via fluorescence or photoacoustic imaging (PAI), a nonionizing modality dependent on optical absorption properties of the tissue. PAI-guided PDT requires a near-infrared contrast agent for deep tissue imaging with minimal photobleaching effect. We evaluate the impact of PDT agent, benzoporphyrin derivative (BPD), on PAI agent indocyanine green (ICG) and vice versa, given that they have different optical absorption properties and singlet oxygen quantum yields for PDT. Specifically, we demonstrate in two oral squamous cell carcinoma lines (FaDu and SCC4) that ICG has minimal effect on BPD PDT efficacy when irradiated with either a continuous or pulsed laser. Furthermore, the impact of BPD on ICG photodegradation was monitored with PAI in tissue-mimicking phantoms. These studies inform us that the combination of BPD and ICG can be utilized for PAI-guided PDT. However, researchers need to consider the photodegradation effects of ICG in the presence of BPD when designing their drug delivery strategies for PAI-guided PDT.

Techniques for intraoperative evaluation of bowel viability in mesenteric ischemia: A review

Acute mesenteric ischemia (AMI) is a deadly and common surgical emergency. While several imaging modalities aid in the diagnosis of AMI preoperatively, there are limited intraoperative tools for surgeon decision making regarding bowel viability. Here we offer a review of the utility and limitations of the many extensively studied techniques. We classify each of these modalities into three hallmarks of healthy bowel: oxygenation, myoelectric activity and perfusion. Finally, we offer a brief discussion of emerging and promising techniques to assist surgeons in intraoperative decision making for patients with mesenteric ischemia.