Hepatic elimination of indocyanine green with special reference to distribution kinetics and the influence of plasma protein binding

Recent Advancement of Indocyanine Green Based Nanotheranostics for Imaging and Therapy of Coronary Atherosclerosis

Atherosclerosis is a vascular intima condition in which any part of the circulatory system is affected, including the aorta and coronary arteries. Indocyanine green (ICG), a theranostic compound approved by the FDA, has shown promise in the treatment of coronary atherosclerosis after incorporation into nanoplatforms. By integration of ICG with targeting agents such as peptides or antibodies, it is feasible to increase its concentration in damaged arteries, hence increasing atherosclerosis detection. Nanotheranostics offers cutting-edge techniques for the clinical diagnosis and therapy of atherosclerotic plaques. Combining the optical properties of ICG with those of nanocarriers enables the improved imaging of atherosclerotic plaques and targeted therapeutic interventions. Several ICG-based nanotheranostics platforms have been developed such as polymeric nanoparticles, iron oxide nanoparticles, biomimetic systems, liposomes, peptide-based systems, etc. Theranostics for atherosclerosis diagnosis use magnetic resonance imaging (MRI), computed tomography (CT), near-infrared fluorescence (NIRF) imaging, photoacoustic/ultrasound imaging, positron emission tomography (PET), and single photon emission computed tomography (SPECT) imaging techniques. In addition to imaging, there is growing interest in employing ICG to treat atherosclerosis. In this review, we provide a conceptual explanation of ICG-based nanotheranostics for the imaging and therapy of coronary atherosclerosis. Moreover, advancements in imaging modalities such as MRI, CT, PET, SPECT, and ultrasound/photoacoustic have been discussed. Furthermore, we highlight the applications of ICG for coronary atherosclerosis.

Tissue perfusion in DIEP flaps using Indocyanine Green Fluorescence Angiography, Hyperspectral imaging, and Thermal imaging

Flap necrosis continues to occur in skin free flap autologous breast reconstruction. Therefore, we investigated the benefits of indocyanine green angiography (ICGA) using quantitative parameters for the objective, perioperative evaluation of flap perfusion. In addition, we investigated the feasibility of hyperspectral (HSI) and thermal imaging (TI) for postoperative flap monitoring. A single-center, prospective observational study was performed on 15 patients who underwent deep inferior epigastric perforator (DIEP) flap breast reconstruction (n=21). DIEP-flap perfusion was evaluated using ICGA, HSI, and TI using a standardized imaging protocol. The ICGA perfusion curves and derived parameters, HSI extracted oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) values, and flap temperatures from TI were analyzed and correlated to the clinical outcomes. Post-hoc quantitative analysis of intraoperatively collected data of ICGA application accurately distinguished between adequately and insufficiently perfused DIEP flaps. ICG perfusion curves identified the lack of arterial inflow (n=2) and occlusion of the venous outflow (n=1). In addition, a postoperatively detected partial flap epidermolysis could have been predicted based on intraoperative quantitative ICGA data. During postoperative monitoring, HSI was used to identify impaired perfusion areas within the DIEP flap based on deoxyHb levels. The results of this study showed a limited added value of TI. Quantitative, post-hoc analysis of ICGA data produced objective and reproducible parameters that enabled the intraoperative detection of arterial and venous congested DIEP flaps. HSI appeared to be a promising technique for postoperative flap perfusion assessment. A diagnostic accuracy study is needed to investigate ICGA and HSI parameters in real-time and demonstrate their clinical benefit.

Diagnosis of liver fibrosis and liver function reserve through non-invasive multispectral photoacoustic imaging

Liver function reserve (LFR) is the sum of remnant functional hepatic cells after liver injury. In the pathologic process of liver fibrosis (LF), LFR is impaired. LFR assessment can help determine the safe scope of liver resection or drug regimen and predict prognosis of patients with liver disease. Here, we used a photoacoustic imaging (PAI) system to assess LF and LFR in rabbit models. We performed PAI, ultrasound elastography and biopsy for 21 rabbits developing none (n = 6) and LF (n = 15). In vivo indocyanine green (ICG) measurements by PAI showed that LF group presented a significantly attenuated ICG clearance compared to control group, indicating LFR impairment of LF. Another finding was a significantly higher collagen photoacoustic signal intensity value was observed in LF both in vivo and in vitro. Our findings demonstrated that PAI was potentially effective to evaluate LFR and collagen accumulation of LF.

Handheld photoacoustic imaging of indocyanine green clearance for real-time quantitative evaluation of liver reserve function

Preoperative assessment of liver function reserve (LFR) is essential for determining the extent of liver resection and predicting the prognosis of patients with liver disease. In this paper, we present a real-time, handheld photoacoustic imaging (PAI) system-based noninvasive approach for rapid LFR assessment. A linear-array ultrasound transducer was sealed in a housing filled with water; its front end was covered with a plastic wrap. This PAI system was first implemented on phantoms to confirm that the photoacoustic (PA) intensity of indocyanine green (ICG) in blood reflects the concentration of ICG in blood. In vivo studies on normal rabbits and rabbits with liver fibrosis were carried out by recording the dynamic PA signal of ICG in their jugular veins. By analyzing the PA intensity-time curve, a clear difference was identified in the pharmacokinetic behavior of ICG between the two groups. In normal rabbits, the mean ICG clearance rate obtained by PAI at 15 min after administration (PAI-R15) was below 21.6%, whereas in rabbits with liver fibrosis, PAI-R15 exceeded 62.0% because of poor liver metabolism. The effectiveness of the proposed method was further validated by the conventional ICG clearance test and pathological examination. Our findings suggest that PAI is a rapid, noninvasive, and convenient method for LFR assessment and has immense potential for assisting clinicians in diagnosing and managing patients with liver disease.

ICG clearance test based on photoacoustic imaging for assessment of human liver function reserve: An initial clinical study

Liver function reserve (LFR) plays an extensive and important role in patients with liver disease. Indocyanine green (ICG) clearance test is the standard diagnostic approach for LFR evaluation which was performed by spectrophotometry or pulse dye densitometry (PDD). Spectrophotometry is the gold standard, it's invasive and not real-time. PDD is non-invasive, but accuracy of PDD is controversial. Taken spectrophotometry as the reference standard, this study investigated the accuracy of photoacoustic imaging (PAI) method for LFR assessment and compared to PDD in healthy volunteers. The results demonstrated a strong correlation between PAI method and spectrophotometry (r = 0.9649, p < 0.0001). No significant difference was shown in ICG clearance between PAI and spectrophotometry method (rate constant k1 vs. k2, 0.001158 +-0.00042 vs. 0.001491 +- 0.00045, p = 0.0727; half-life t1 vs. t2, 601.2 s vs. 474.4 s, p = 0.1450). These results indicated that PAI may be valuable as a noninvasive, accurate diagnostic tool for LFR assessment in human.

Nanotechnology-based photo-immunotherapy: a new hope for inhibition of melanoma growth and metastasis

Melanoma is the most aggressive form of skin cancer and there is a need for the development of effective anti-melanoma therapies as it shows high metastatic ability and low response rate. In addition, it has been identified that traditional phototherapy could trigger immunogenic cell death (ICD) to activate antitumor immune response, which could not only effectively arrest primary tumor growth, but also exhibit superior effects in terms of anti-metastasis, anti-recurrence for metastatic melanoma treatment However, the limited tumor accumulation of photosensitizers/photothermal agents and immunosuppressive tumor microenvironment severely weaken the immune effects. The application of nanotechnology facilitates a higher accumulation of photosensitizers/photothermal agents at the tumor site, which can thus improve the antitumor effects of photo-immunotherapy (PIT). In this review, we summarize the basic principles of nanotechnology-based PIT and highlight novel nanotechnologies that are expected to enhance the antitumor immune response for improved therapeutic efficacy.

Quantitative parameters obtained from gadobenate dimeglumine-enhanced MRI at the hepatobiliary phase can predict post-hepatectomy liver failure and overall survival in patients with hepatocellular carcinoma

PURPOSE

To determine the value of the quantitative parameters obtained from gadobenate dimeglumine-enhanced magnetic resonance imaging (MRI) at the hepatobiliary phase for predicting post-hepatectomy liver failure and overall survival in patients with hepatocellular carcinoma.

METHOD

This multicenter retrospective study included 307 patients who underwent gadobenate dimeglumine-enhanced MRI. The quantitative liver-to-portal vein contrast ratio (LPC) and liver-spleen contrast ratio (LSC) at the hepatobiliary phase were measured. Logistic regression analyses were used to evaluate risk factors for post-hepatectomy liver failure. The capacity of the LPC and LSC to predict post-hepatectomy liver failure was evaluated via receiver operating characteristic (ROC) curve. The Cox proportional hazards regression was used to identify prognostic factors for overall survival (OS).

RESULTS

Post-hepatectomy liver failure was observed in 69 patients (22.5%). The LPC and LSC were independent risk factors for the development of post-hepatectomy liver failure, and the areas under the ROC curves of LPC and LSC were 0.882 and 0.782, respectively. The predictive performance of LPC for post-hepatectomy liver failure was superior to LSC. The LPC and LSC were also significant prognostic factors for OS. The cut-off values for the LPC and LSC were 1.07 and 0.89, respectively. The 5-year OS rate was higher in patients with LPC > 1.07 or LSC > 0.89 than in patients with LPC ≤ 1.07 or LSC ≤ 0.89.

CONCLUSIONS

The quantitative parameters obtained from gadobenate dimeglumine-enhanced MRI at the hepatobiliary phase were effective imaging biomarkers for predicting both post-hepatectomy liver failure and overall survival in patients with hepatocellular carcinoma.

Determination of hepatic clearance by derivations of the indocyanine green retention test in cirrhosis

BACKGROUND AND AIM

The study was undertaken in order to compare single injection indocyanine green (ICG)-clearances with the steady-state ICG-clearance (ICG_Cl ) in patients with cirrhosis in order to assess the most accurate estimate for ICG-clearance and to relate the ICG-clearances to established indicators of liver dysfunction.

METHODS

Thirty-eight patients (male 29) with cirrhosis (Child-Turcotte class A 8, class B 21, and class C 9) were studied during a hemodynamic investigation. A single injection of ICG was followed by blood samples for 5, 10, 15, and 20 min. The dose/plasma area clearance (Cl_A ) and plasma volume · initial slope clearance (Cl_PV ) were determined and compared with the steady-state infusion/plasma concentration ratio clearance (ICG_Cl ).

RESULTS

The Cl_A (310; 214; 502 mL/min) and Cl_PV (294; 164; 481 mL/min) correlated closely with ICG_Cl (243; 120; 383 mL/min [median; interquartile range], R = 0.95-0.98, P < 0.000), but were significantly higher than ICG_Cl (P < 0.001). All three clearance measures correlated significantly with biochemical and hemodynamic variables of liver dysfunction (P < 0.05-0.000). All three ICG-clearances showed significantly lower values in patients with ascites compared to those without, and lower ICG-clearance values were present in patients with esophageal varices compared to those without (P < 0.05-0.002).

CONCLUSION

Single injection markers (Cl_A and Cl_PV ) of the steady-state ICG-clearance as derived from the ICG-retention curve and the plasma volume correlate with ICG_Cl and established variables of portal hypertension and liver cell bile excretory dysfunction. Therefore, these markers can safely replace the more costly ICG_Cl .

Physiologically Based Modeling of the Effect of Physiological and Anthropometric Variability on Indocyanine Green Based Liver Function Tests

Accurate evaluation of liver function is a central task in hepatology. Dynamic liver function tests (DLFT) based on the time-dependent elimination of a test substance provide an important tool for such a functional assessment. These tests are used in the diagnosis and monitoring of liver disease as well as in the planning of hepatobiliary surgery. A key challenge in the evaluation of liver function with DLFTs is the large inter-individual variability. Indocyanine green (ICG) is a widely applied test compound used for the evaluation of liver function. After an intravenous administration, pharmacokinetic (PK) parameters are calculated from the plasma disappearance curve of ICG which provide an estimate of liver function. The hepatic elimination of ICG is affected by physiological factors such as hepatic blood flow or binding of ICG to plasma proteins, anthropometric factors such as body weight, age, and sex, or the protein amount of the organic anion-transporting polypeptide 1B3 (OATP1B3) mediating the hepatic uptake of ICG. Being able to account for and better understand these various sources of inter-individual variability would allow to improve the power of ICG based DLFTs and move toward an individualized evaluation of liver function. Within this work we systematically analyzed the effect of various factors on ICG elimination by the means of computational modeling. For the analysis, a recently developed and validated physiologically based pharmacokinetics (PBPK) model of ICG distribution and hepatic elimination was utilized. Key results are (i) a systematic analysis of the variability in ICG elimination due to hepatic blood flow, cardiac output, OATP1B3 abundance, liver volume, body weight and plasma bilirubin level; (ii) the evaluation of the inter-individual variability in ICG elimination via a large in silico cohort of n = 100,000 subjects based on the NHANES cohort with special focus on stratification by age, sex, and body weight; (iii) the evaluation of the effect of various degrees of cirrhosis on variability in ICG elimination. The presented results are an important step toward individualizing liver function tests by elucidating the effects of confounding physiological and anthropometric parameters in the evaluation of liver function via ICG.

Comparison of Various Modalities Utilized for Preoperative Planning in Microsurgical Reconstructive Surgery

BACKGROUND

 The benefits of preoperative perforator imaging for microsurgical reconstruction have been well established in the literature.

METHODS

 An extensive literature review was performed to determine the most commonly used modalities, and their applicability, advantages and disadvantages.

RESULTS

 The review demonstrated varioius findings including decreases in operative time and cost with the use of CT angiography to identification of perforators for inclusion in flap design with hand-held Doppler ultrasound. Modalities like MR angiography offer alternatives for patients with contrast allergies or renal dysfunction while maintaining a high level of clarity and fidelity. Although the use of conventional angiography has decreased due to the availability of less invasive alternatives, it continues to serve a role in the preoperative evaluation of patients for lower extremity reconstruction. Duplex ultrasonography has been of great interest recently as an inexpensive, risk free, and extraordinarily accurate diagnostic tool. Emerging technologies such as indocyanine green fluorescence angiography and dynamic infrared thermography provide real-time information about tissue vascularity and perfusion without requiring radiation exposure.

CONCLUSION

 This article presents an in-depth review of the various imaging modalities available to reconstructive surgeons and includes hand held Doppler ultrasound, CT angiography, MR angiography, conventional angiography, duplex ultrasonography, Indocyanine Green Fluorescence Angiography and Dynamic Infrared Thermography.

Delayed perfusion evaluation in extremity trauma

After severe trauma to an extremity, it is essential to achieve a stable and non-infected wound in order to facilitate the best outcome following reconstruction. That said, timely, meticulous and adequate debridement is very important. To facilitate the best possible debridement of the wound, it is important to understand the tissue circulation. One available method to evaluate tissue circulation following extremity trauma is indocyanine green (ICG) angiography. Though playing an important role in flap surgeries, ICG may also provide information regarding the perfusion at the zone of injury while circulation quality diminishes. We present a case where ICG angiography initially showed good circulation in a mangled extremity, but later used in alternative way to display lack of flow in the same area of interest.

Comparison between preoperative two-dimensional shear wave elastography and indocyanine green clearance test for prediction of post-hepatectomy liver failure

Background

Post-hepatectomy liver failure (PHLF) is one of the most serious complications and major causes of liver resection mortality. The purpose of this study is to investigate and compare the performance of preoperative two-dimensional shear wave elastography (2D-SWE) and the indocyanine green (ICG) clearance test for the prediction of PHLF.

Methods

A total of 172 consecutive patients who were undergoing major liver resection were prospectively identified. Patients were evaluated by preoperative 2D-SWE and ICG clearance test. According to the International Study Group of Liver Surgery (ISGLS) recommendations, No PHLF, PHLF A, PHLF B, and PHLF C group classifications were defined. The differences in liver stiffness value (LSV) and ICG retention rate at 15 minutes (ICGR15) among the different PHLF classifications were investigated. The performance of LSV and ICGR15 for diagnosing different classifications of PHLF was compared.

Results

PHLF occurred in 43 (25.0%) patients, and 24 (14.0%) patients were grade A, 14 (8.1%) were grade B, and 5 (2.9%) were grade C. Both LSV and ICGR15 of the PHLF C group were significantly higher than those of the No PHLF group (P=0.025, P=0.001, respectively). According to univariate and multivariate logistic regression analysis, LSV and ICGR15 were significantly related to PHLF (P=0.051, P=0.084, respectively). For diagnosis of ≥ PHLF A, ≥ PHLF B, and ≥ PHLF C, the areas under the receiver operating characteristic curve (AUCs) for 2D-SWE were 0.624 [95% confidence interval (CI): 0.536-0.712, P=0.015], 0.699 (95% CI: 0.576-0.821, P=0.005), and 0.831 (95% CI: 0.737-0.925, P=0.01), respectively. The AUCs of the ICG clearance test were 0.631 (95% CI: 0.542-0.721, P=0.01), 0.570 (95% CI: 0.436-0.704, P=0.32), and 0.717 (95% CI: 0.515-0.920, P=0.098), respectively. The AUC of LSV for the diagnosis of ≥ PHLF A was comparable to that of ICGR15 (P=0.17). The AUCs of LSV were significantly higher than those of ICGR15 for the diagnosis of ≥ PHLF B (P=0.002) and C (P=0.038).

Conclusions

2D-SWE demonstrates the potential to aid in the prediction of the severity of PHLF. Our findings also suggest that the performance of 2D-SWE is better than the ICG clearance test.

"Stealth" dendrimers with encapsulation of indocyanine green for photothermal and photodynamic therapy of cancer

Poly(amido amine) dendrimers and indocyanine green have inevitable interaction with proteins and cells, which induces biological toxicity and reduces therapeutic efficacy in vivo. To overcome these shortcomings, a new drug delivery system G5MEK7C(n)-ICG with a "stealth" layer was prepared. The surface of G5MEK7C(n)-ICG was modified with double-layer super hydrophilic zwitterionic materials. In the "stealth" double-layer structure, the outer layer was consisted of zwitterionic Glu-Lys-Glu-Lys-Glu-Lys-Cys (EK7) peptide, and the inner layer was composed of amino and carboxyl groups with a ratio of 1:1. DLS results showed that the average hydrodynamic size of G5MEK7C(n)-ICG was about 25-30 nm, and the zeta potential was proven to undergo a slight charge reversal with the increasing pH values of solutions. Furthermore, G5MEK7C(n)-ICG exhibited excellent biocompatibility to red blood cells and proteins resistance. Photothermal and photodynamic experiments demonstrated that G5MEK7C(n)-ICG had a good photothermal conversion effect and generated singlet oxygen (¹O₂) under laser irradiation. The MTT and hemolysis results showed that the toxicity of G5 PAMAM was significantly reduced after modification double-layer structure. Cytotoxicity studies and flow cytometry showed G5MEK7C(70)-ICG under laser irradiation had a good effect on killing A549 cells. More importantly, the tumor inhibition rate of mice treated with G5MEK7C(70)-ICG (under laser irradiation) was 78.2% in vivo, which was higher than that of mice treated with free ICG. Compared with free ICG, G5MEK7C(70)-ICG caused less damage to the liver according to the enzyme activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Therefore, dendrimers modified with a zwitterionic double layer will be a promising candidate as a drug delivery system.

Nucleus-Targeted Photosensitizer Nanoparticles for Photothermal and Photodynamic Therapy of Breast Carcinoma

PURPOSE

The near-infrared fluorescent dye indocyanine green (ICG) has shown great potential in the photodynamic therapy (PDT) and photothermal therapy (PTT) of cancer. However, its disadvantages of instability in aqueous solution, short half-life, and non-targeting accumulation limit the effectiveness of ICG PDT/PTT. To overcome the disadvantages of ICG in tumor treatment, we designed PEGylated-human serum albumin (PHSA)-ICG-TAT. In this nanoparticle, PEG4000, the HSA package, and nuclear targeting peptide TAT (human immunodeficiency virus 1 [HIV-1]-transactivator protein) were used to improve the water solubility of ICG, prolong the life span of ICG in vivo, and target the nuclei of tumor cells, respectively.

METHODS

The PHSA-ICG-TAT was characterized in terms of morphology and size, ultraviolet spectrum, dispersion stability, singlet oxygen and cellular uptake, and colocalization using transmission electron microscopy and dynamic light scattering, and fluorescence assay, respectively. Subsequently, the anti-tumor effect of PHSA-ICG-TAT was investigated via in vitro and in vivo experiments, including cell viability, apoptosis, comet assays, histopathology, and inhibition curves.

RESULTS

The designed ICG-loaded nanoparticle had a higher cell uptake rate and stronger PDT/PTT effect than free ICG. The metabolism of PHSA-ICG-TAT in normal mice revealed that there was no perceptible toxicity. In vivo imaging of mice showed that PHSA-ICG-TAT had a good targeting effect on tumors. PHSA-ICG-TAT was used for the phototherapy of tumors, and significantly suppressed the tumor growth. The tumor tissue sections showed that the cell gap and morphology of the tumor tissue had been obviously altered after treatment with PHSA-ICG-TAT.

CONCLUSION

These results indicate that the PHSA-ICG-TAT had a significant therapeutic effect against tumors.

Recent progress in photosensitizers for overcoming the challenges of photodynamic therapy: from molecular design to application

Photodynamic therapy (PDT), a therapeutic mode involving light triggering, has been recognized as an attractive oncotherapy treatment. However, nonnegligible challenges remain for its further clinical use, including finite tumor suppression, poor tumor targeting, and limited therapeutic depth. The photosensitizer (PS), being the most important element of PDT, plays a decisive role in PDT treatment. This review summarizes recent progress made in the development of PSs for overcoming the above challenges. This progress has included PSs developed to display enhanced tolerance of the tumor microenvironment, improved tumor-specific selectivity, and feasibility of use in deep tissue. Based on their molecular photophysical properties and design directions, the PSs are classified by parent structures, which are discussed in detail from the molecular design to application. Finally, a brief summary of current strategies for designing PSs and future perspectives are also presented. We expect the information provided in this review to spur the further design of PSs and the clinical development of PDT-mediated cancer treatments.

Altered Lymphatic Vessel Anatomy and Markedly Diminished Lymph Clearance in Affected Hands of Patients With Active Rheumatoid Arthritis

OBJECTIVE

To assess differences between lymphatic function in the affected hands of rheumatoid arthritis (RA) patients with active synovitis and that of healthy controls, using indocyanine green (ICG) dye and near-infrared (NIR) imaging.

METHODS

NIR imaging of the hands of 8 patients with active RA and 13 healthy controls was performed following web space injection of 0.1 ml of 100 μM ICG. The percentage of ICG retention in the web spaces was determined by NIR imaging at baseline and at 7 days (±1 day) after the initial injections; image analysis provided contraction frequency. ICG+ lymphatic vessel (LV) length and branching architecture were assessed.

RESULTS

Retention of ICG in RA hands was higher compared to controls (P < 0.01). The average contraction frequency of ICG+ LVs in RA patients and in controls did not differ (mean ± SD 0.53 ± 0.39 contractions/minute versus 0.51 ± 0.35 contractions/minute). Total ICG+ LV length in RA hands was lower compared to healthy controls (58.3 ± 15.0 cm versus 71.4 ± 16.1 cm; P < 0.001), concomitant with a decrease in the number of ICG+ basilic LVs in the hands of RA patients (P < 0.05).

CONCLUSION

Lymphatic drainage in the hands of RA patients with active disease was reduced compared to controls. This reduction was associated with a decrease in total length of ICG+ LVs on the dorsal surface of the hands, which continued to contract at a similar rate to that observed in controls. These findings provide a plausible mechanism for exacerbation of synovitis and joint damage, specifically the accumulation and retention of inflammatory cells and catabolic factors in RA joints due to impaired efferent lymphatic flow. NIR/ICG imaging of RA hands is feasible and warrants formal investigation as a primary outcome measure for arthritis disease severity and/or persistence in future clinical trials.

The Use of Indocyanine Green Angiography for Cosmetic and Reconstructive Assessment in the Head and Neck

Reconstructive procedures in the head and neck can be a surgical challenge owing to the complex anatomical and physiological structure. Different locoregional and microvascular flaps are used for various defects to improve both function and cosmesis. Subjective clinical findings have been the mainstay for perfusion monitoring; however, areas of borderline perfusion are much more difficult to assess clinically. Multiple technologies that offer objective perfusion assessment have been developed to improve surgical outcomes. Indocyanine green (ICG) angiography has gained popularity owing to its minimal invasiveness and increased sensitivity and specificity in assessing flap perfusion particularly in the head and neck. It has been extensively used in free flaps, pedicled flaps (including nasal reconstruction), facelift procedures, random flaps, skull base reconstruction, and pharyngocutaneous fistula prediction. Its perioperative use has provided valuable qualitative and quantitative data that aid our understanding of flap hemodynamics. Clinically, this impacted decision-making in flap design, harvest, inset, and precocious salvage interventions. Though increased cost and intraoperative time could be limitations, cost-effectiveness studies have supported its use, particularly in high-risk individuals. Limitations include the lack of standardized dosing and consistent methodology agreement for data analysis. Future studies should involve larger cohorts and multi-institute studies to overcome such limitations.

Near-Infrared Responsive Phase-Shifted Nanoparticles for Magnetically Targeted MR/US Imaging and Photothermal Therapy of Cancer

Accurate diagnosis, providing guidance for early treatment, can greatly improve the survival rate of cancer patients. However, there are still some difficulties with the existing diagnostic technology and early treatment methods. Here, near-infrared responsive phase-shifted nanoparticles (NRPNs) have been designed for magnetically targeted MR/US imaging and photothermal therapy of tumors. In this study, we fabricated a multifunctional polymer nanoparticle encapsulating indocyanine green (ICG), magnetic Fe₃O₄ nanoparticles and perfluoropentane (PFP). Under laser irradiation, the NRPNs, which trigger a phase-shifted expansion effect due to the quick conversion from light to heat by ICG and Fe₃O₄, can be used for ultrasound (US) imaging. At the same time, such nanoparticles can kill cancer cells via photothermal therapy (PTT). As a kind of negative enhancement agent, magnetic Fe₃O₄ nanoparticles in NRPNs showed high spatial resolution in MR imaging. Moreover, with the help of the magnetic field, the NRPNs nanoparticles showed high cellular uptake and high tumor accumulation, indicating their magnetic targeting property without biosafety concerns. Therefore, we present a strategy for magnetically targeted MR/US imaging guided photothermal therapy for the accurate diagnosis and efficient treatment of tumors.

Microbial Composition of Oral Biofilms after Visible Light and Water-Filtered Infrared a Radiation (VIS+wIRA) in Combination with Indocyanine Green (ICG) as Photosensitizer

In view of increasing antibiotic resistance, antimicrobial photodynamic therapy (aPDT) is an alternative treatment method used to eradicate the microbial community of oral biofilms that can be responsible for different oral infections. In order to investigate changes in the microbial composition after application of aPDT with visible light and water-filtered infrared A (VIS+wIRA) in combination with indocyanine green (ICG), oral microorganisms of the initial and mature biofilm were evaluated by mass spectrometry (MALDI-TOF-MS). To determine surviving microorganisms using MALDI-TOF-MS, an in situ biofilm was irradiated with VIS+wIRA for five minutes in the presence of ICG (300 and 450 µg/mL, respectively). Treatment with chlorhexidine (0.2%) served as positive control. Identified microorganisms of the initial biofilm treated with ICG showed a clear reduction in diversity. The microbial composition of the mature oral biofilm also showed changes after the implementation of aPDT, which mainly resulted in a shift in the percentage of bacterial species. The resulting destruction of the microbial balance within the oral biofilm by aPDT using VIS+wIRA and ICG can be seen as an advantageous supplementary approach in the adjunctive treatment of periodontitis and peri-implantitis.

Assessment of liver function reserve by photoacoustic tomography: a feasibility study

Assessment of liver function reserve (LFR) is essential to determine liver resection scope and predict prognosis for patients with liver disease. Indocyanine green (ICG) concentration change is a classic marker to reflect liver function reserve as ICG is selectively taken up and eliminated by liver. Here we proposed a noninvasive approach for LFR assessment based on a real-time photoacoustic tomography (PAT) system. This feasibility study was to detect ICG concentration change by PAT in phantom and in vivo using both normal and partial hepatectomy (PH) rabbits. A linear relationship between photoacoustic signal intensity of ICG and ICG concentration was found in vitro. In vivo ICG concentration change over time after ICG injection was observed by PAT in normal rabbits, which was consistent with the findings measured by invasive spectrophotometry. Finally, clear difference in ICG clearance between the control and PH models was identified by PAT. Taken together, our study indicated the clinical potential of PAT to in vivo evaluate LFR noninvasively.

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.

Application of Fluorescent Dyes in Visceral Surgery: State of the Art and Future Perspectives

Background

Through the improvement and implementation of advanced intraoperative imaging, the indications for intraoperative fluorescence have spread to various fields of visceral surgery. Indocyanine green (ICG)-based fluorescence angiography and the imaging systems using this certain dye are currently the cornerstone of intraoperative, fluorescence-based medical imaging.

Summary

The article focuses on principles and approaches of intraoperative fluorescence in general surgery. The current clinical practice of intraoperative fluorescence and its evidence are described. Emerging new fields of application are put in a perspective. Furthermore, the technique and possible pit-falls in the performance of intraoperative ICG fluorescence angiography are described in this review article.

Key Messages

Overall growing evidence suggests that intraoperative fluorescence imaging delivers valuable additional information to the surgeon, which might help to perform surgery more exactly and reduce perioperative complications. Perfusion assessment can be a helpful tool when performing critical anastomoses. There is evidence from prospective and randomized trials for the benefit of intraoperative ICG fluorescence angiography during esophageal reconstruction, colorectal surgery, and surgery for mesenteric ischemia. Most studies suggest the administration of 2.5-10 mg of ICG. Standardized settings and documentation are essential. The benefit of ICG fluorescence imaging for gastrointestinal sentinel node detection and detection of liver tumors and colorectal metastases of the liver cannot clearly be estimated duo to the small number of prospective studies. Critical points in the use of intraoperative fluorescence imaging remain the low standardization and reproducibility of the results and the associated difficulty in comparing the results of the existing trials. Furthermore, little is known about the influence of hemodynamic parameters on the quantitative assessment of ICG fluorescence during surgery.

Neovascularization Perfusion of Melolabial Flaps Using Intraoperative Indocyanine Green Angiography

Importance

Assessment of melolabial flap perfusion using indocyanine green (ICG) angiography for nasal reconstruction has not been previously described.

Objective

To assess melolabial flap relative perfusion using ICG angiography in nasal reconstruction and highlight its clinical relevance.

Design, Setting, and Participants

In this retrospective case series at a tertiary referral center, 10 patients undergoing melolabial flap reconstruction of nasal defects between January 2015 to April 2018 with flap perfusion were assessed by ICG angiography.

Exposures

Indocyanine green angiography was performed to assess melolabial flap perfusion at second stage surgery after temporary clamping of the pedicle and after pedicle division and flap inset.

Main Outcomes and Measures

Flap perfusion in relation to a reference point on the cheek was calculated after both pedicle clamping and division by 2 methods: (1) ingress (arterial inflow) and egress (venous outflow) flap-to-cheek ratio; (2) flap-to-cheek perfusion (fluorescence) ratio at 3 time points (midpoint of ICG flap inflow, maximum [peak] fluorescence, and midpoint of ICG outflow), and their calculated mean. Correlations of perfusion with time between stages, and patient factors were performed; perfusion parameters after temporary pedicle clamping and after division and flap inset were compared.

Results

Ten patients (mean [SD] age, 66 [7.5] years) were enrolled with a mean (SD) interval of 23 (4) days between first and second surgery. No correlation existed between perfusion parameters and time interval between first and second stage, or any other patient factors. Of the different perfusion parameters, a statistically significant difference was observed when comparing temporary clamping and postdivision mean (SD) flap-to-cheek perfusion ratio (0.89 [0.22] and 0.80 [0.19]; 95% CI, 4.1-12.6; P = .001), as well as mean (SD) peak perfusion ratio (0.81 [0.2] and 0.77 [0.2]; 95% CI, 0.005-0.080; P = .02) only. No partial or complete flap necrosis was reported after pedicle division.

Conclusions and Relevance

Indocyanine green angiography is an effective method to determine neovascularization perfusion of melolabial flaps, with a mean perfusion of 89% after pedicle clamping. Future applications of this technology include use in patients at high risk for flap necrosis, or those who may benefit from early flap division to ensure adequate perfusion and minimize the time interval between staged procedures.

Level of Evidence

NA.

Utility of Indocyanine Green Angiography to Identify Clinical Factors Associated With Perfusion of Paramedian Forehead Flaps During Nasal Reconstruction Surgery

Importance

Identifying factors affecting forehead flap neovascularization during nasal reconstruction surgical procedures using quantitative dynamics of fluorescence from indocyanine green angiography may be associated with reduced vascular complications.

Objectives

To identify quantifiable forehead flap perfusion measures using indocyanine green angiography during nasal reconstruction procedures and to evaluate clinical factors associated with neovascularization.

Design, Setting, and Participants

Retrospective cohort study of 71 patients at a tertiary referral center of Stanford University, Stanford, California, between January 1, 2010, and March 31, 2018, undergoing forehead flap nasal reconstruction surgery with flap perfusion assessed by indocyanine green angiography.

Exposures

Indocyanine green angiography was performed intraoperatively to record forehead flap neovascularization during the second stage of nasal reconstruction surgery after temporary clamping of the pedicle.

Main Outcomes and Measures

With use of quantifiable data of fluorescence dynamics, flap perfusion in association with a reference point in the cheek after pedicle clamping was assessed by 2 methods: (1) ingress (arterial inflow) and egress (venous outflow) flap-to-cheek ratio and (2) flap-to-cheek perfusion (fluorescence) ratio at 3 time points (midpoint of indocyanine green flap inflow, maximum fluorescence [peak], and midpoint of indocyanine green flap outflow) and their calculated mean. Association of the perfusion measures with patient and procedural factors was performed using linear regression models.

Results

Of the 71 patients included in the study, 43 (61%) were men; the mean (SD) age was 71.1 (11.0) years. The mean (SD) flap-to-cheek inflow ratio was 0.48 (0.40), peak fluorescence ratio was 0.59 (0.34), and outflow ratio was 0.88 (0.42). The calculated mean (SD) flap-to-cheek perfusion ratio of these measures was 0.65 (0.35). The mean (SD) flap-to-cheek ingress ratio was 0.54 (0.36) and egress ratio was 0.65 (0.98). With use of a multivariable regression model, the time between stages was positively associated with flap-to-cheek ingress ratio (β, 0.015; 95% CI, 0.001 to 0.030), and cartilage grafting was negatively associated with flap-to-cheek outflow ratio (β, -0.240; 95% CI, -0.472 to -0.008).

Conclusions and Relevance

The findings suggest that indocyanine green angiography is an effective method to quantify relative neovascularization perfusion of forehead flaps. Future applications may include the use of this technology to aid in early flap division and ensure adequate perfusion among high-risk patients.

Level of Evidence

NA.

Non-alcoholic fatty liver disease causes dissociated changes in metabolic liver functions

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a major health concern affecting 25% of the world's population. It is generally held that a fatty liver does not influence liver function, but quantitative measurements of metabolic liver functions have not been systematically performed. We aimed to study selected hepatocellular metabolic functions in patients with different stages of NAFLD.

METHODS

Twenty-five non-diabetic, biopsy-proven NAFLD patients [12 with simple steatosis; 13 with non-alcoholic steatohepatitis (NASH)] and ten healthy controls were included in a cross-sectional study. Hepatocyte cytosolic function was assessed by the galactose elimination capacity (GEC), mitochondrial-cytosolic metabolic capacity by the functional hepatic nitrogen clearance (FHNC), microsomal function by the aminopyrine breath test, and excretory liver function by indocyanine green (ICG) elimination.

RESULTS

GEC was 20% higher in NAFLD than in controls [3.15 mmol/min (2.9-3.41) vs. 2.62 (2.32-2.93); P = 0.02]. FHNC was 30% lower in NAFLD [23.3 L/h (18.7-28.9) vs. 33.1 (28.9-37.9); P = 0.04], more so in simple steatosis [19.1 L/h (13.9-26.2); P = 0.003] and non-significantly in NASH [27.9 L/h (20.6-37.8); P = 0.19]. Aminopyrine metabolism was 25% lower in simple steatosis [8.9% (7.0-10.7)] and 50% lower in NASH [6.0% (4.5-7.5)] than in controls [11.9% (9.3-12.8)] (P < 0.001). ICG elimination was intact.

CONCLUSIONS

The hepatocellular metabolic functions were altered in a manner that was dissociated both by different effects on different liver functions and by different effects of different stages of NAFLD. Thus, NAFLD has widespread consequences for metabolic liver function, even in simple steatosis.

Optimizing Indocyanine Green Fluorescence Angiography in Reconstructive Flap Surgery: A Systematic Review and Ex Vivo Experiments

Background. Indocyanine green angiography (ICGA) offers the potential to provide objective data for evaluating tissue perfusion of flaps and reduce the incidence of postoperative necrosis. Consensus on ICGA protocols and information on factors that have an influence on fluorescence intensity is lacking. The aim of this article is to provide a comprehensive insight of in vivo and ex vivo evaluation of factors influencing the fluorescence intensity when using ICGA during reconstructive flap surgery. Methods. A systematic literature search was conducted to provide a comprehensive overview of currently used ICGA protocols in reconstructive flap surgery. Additionally, ex vivo experiments were performed to further investigate the practical influence of potentially relevant factors. Results. Factors that are considered important in ICGA protocols, as well as factors that might influence fluorescence intensity are scarcely reported. The ex vivo experiments demonstrated that fluorescence intensity was significantly related to dose, working distance, angle, penetration depth, and ambient light. Conclusions. This study identified factors that significantly influence the fluorescence intensity of ICGA. Applying a weight-adjusted ICG dose seems preferable over a fixed dose, recommended working distances are advocated, and the imaging head during ICGA should be positioned in an angle of 60° to 90° without significantly influencing the fluorescence intensity. All of these factors should be considered and reported when using ICGA for tissue perfusion assessment during reconstructive flap surgery.

Indocyanine green retention test in cirrhosis and portal hypertension: Accuracy and relation to severity of disease

BACKGROUND AND AIMS

Patients with cirrhosis and portal hypertension often develop complications relating to hepatic excretory dysfunction. The standard measurement of the hepatic excretion is the constant infusion indocyanine green clearance (ICG_CI ) technique. The ICG 15-min retention test (ICG-r15) is faster, more patient friendly, and cheaper. The aims were to compare the ICG-r15 test with the standard method, to assess relations to patient characteristics and survival, and to assess the ICG-r15 level in healthy control subjects.

METHODS

This study included 68 patients with cirrhosis and portal hypertension (Child class A/B/C:17/37/14). All patients underwent a full liver vein catheterization and hemodynamic evaluation with determination of ICG-r15 and ICG_CI as the reference in a subset of 38 patients. Sixteen healthy control subjects were included for compiling a reference interval.

RESULTS

The ICG-r15 was increased in the cirrhotic patients with increasing values in parallel with liver dysfunction (15/41/58%) in Child class A/B/C compared with 7% in the controls (P < 0.001). ICG-r15 correlated highly significantly with the ICG_CI (r = -0.96, P < 0.0001) and in a multivariate regression analysis with hepatic venous pressure gradient, markers of liver dysfunction and hyperdynamic circulation (P < 0.05-0.005). In the control group, normal reference values ranged from 0% to 13%. In addition, ICG-r15 was significantly related to mortality in the patient group (P = 0.02).

CONCLUSIONS

Indocyanine green-r15 reflects portal hypertension, the degree of hepatic failure, and survival and may replace the standard ICG_CI . A more elaborated reference interval needs to be compiled, and the prognostic value of ICG-r15 should be validated.

NIR-Light-Triggered Anticancer Strategy for Dual-Modality Imaging-Guided Combination Therapy via a Bioinspired Hybrid PLGA Nanoplatform

A promising approach toward cancer therapy is expected to integrate imaging and therapeutic agents into a versatile nanocarrier for achieving improved antitumor efficacy and reducing the side effects of conventional chemotherapy. Herein, we designed a poly(d,l-lactic- co-glycolic acid) (PLGA)-based theranostic nanoplatform using the double emulsion solvent evaporation method (W/O/W), which is associated with bovine serum albumin (BSA) modifications, to codeliver indocyanine green (ICG), a widely used near-infrared (NIR) dye, and doxorubicin (Dox), a chemotherapeutic drug, for dual-modality imaging-guided chemo-photothermal combination cancer therapy. The resultant ICG/Dox co-loaded hybrid PLGA nanoparticles (denoted as IDPNs) had a diameter of around 200 nm and exhibited excellent monodispersity, fluorescence/size stability, and biocompatibility. It was confirmed that IDPNs displayed a photothermal effect and that the heat induced faster release of Dox, which led to enhanced drug accumulation in cells and was followed by their efficient escape from the lysosomes into the cytoplasm and drug diffusion into the nucleus, resulting in a chemo-photothermal combinatorial therapeutic effect in vitro. Moreover, the IDPNs exhibited a high ability to accumulate in tumor tissue, owing to the enhanced permeability and retention (EPR) effect, and could realize real-time fluorescence/photoacoustic imaging of solid tumors with a high spatial resolution. In addition, the exposure of tumor regions to NIR irradiation could enhance the tumor penetration ability of IDPNs, almost eradicating subcutaneous tumors. In addition, the inhibition rate of IDPNs used in combination with laser irradiation against EMT-6 tumors in tumor-bearing nude mice (chemo-photothermal therapy) was approximately 95.6%, which was much higher than that for chemo- or photothermal treatment alone. Our study validated the fact that the use of well-defined IDPNs with NIR laser treatment could be a promising strategy for the early diagnosis and passive tumor-targeted chemo-photothermal therapy for cancer.

Minimally invasive method for the point-of-care quantification of lymphatic vessel function

Current clinical methods for the evaluation of lymphatic vessel function, crucial for early diagnosis and evaluation of treatment response of several pathological conditions, in particular of postsurgical lymphedema, are based on complex and mainly qualitative imaging techniques. To address this unmet medical need, we established a simple strategy for the painless and quantitative assessment of cutaneous lymphatic function. We prepared a lymphatic-specific tracer formulation, consisting of the clinically approved near-infrared fluorescent dye, indocyanine green, and the solubilizing surfactant Kolliphor HS15. The tracer was noninvasively delivered to the dermal layer of the skin using MicronJet600 hollow microneedles, and the fluorescence signal decay at the injection site was measured over time using a custom-made, portable detection device. The decay rate of fluorescence signal in the skin was used as a direct measure of lymphatic vessel drainage function. With this method, we could quantify impaired lymphatic clearance in transgenic mice lacking dermal lymphatics and distinguish distinct lymphatic clearance patterns in pigs in different body locations and under manual stimulus. Overall, this method has the potential for becoming a noninvasive and quantitative clinical "office test" for lymphatic function assessment.

Clearance of Indocyanine Green in Severe Pediatric Burns

BACKGROUND

Clearance of indocyanine green dye (ICGc) reflects sinusoidal perfusion and hepatocyte cell membrane function. Thus, ICGc is a reflection of the functional reserve of intact hepatocytes. The purpose of this study was to identify predictors of ICGc in severely burned children during the acute hospitalization and at the time of discharge from the intensive care unit (ICU). A secondary aim was to determine the relationship between liver size and patient ICGc.

METHODS

Twenty-six children (0.8-17 years old) with 35% or greater total body surface area burned (%TBSA-B) were included. Assessment of ICGc (in milliliters per minute per meter squared) was done during the acute hospitalization (median: 6 days after admission, median: 14 days postburn) and at the time of discharge from the ICU (median: 19 days after admission, median: 27 days postburn). Age, TBSA-B, % third-degree burns, inhalation injury, preexisting chronic malnutrition, hematocrit, liver dysfunction, and time from burn injury were incorporated in multiple linear regressions as predictive variables of ICGc. Only variables with p < 0.05 were retained in the final models.

RESULTS

Time from injury and age were the strongest predictors of ICGc during the acute admission but not at the time of discharge from the ICU. Time from injury was negatively associated with ICGc, whereas age was positively associated. At the time of discharge from the ICU, ICGc was increased in proportion to the %TBSA-B, whereas inhalation injury and preexisting chronic malnutrition were associated with lower ICGc. There was no correlation between change-to-predicted liver length and ICGc.

CONCLUSIONS

The intrinsic ability of the liver to extract ICG from plasma was lower in younger burned patients during the acute admission and in those with preexisting chronic malnutrition and inhalation injury at the time of discharge from the ICU.

LEVEL OF EVIDENCE

Prognostic/Epidemiologic, level III.

Stability and degradation of indocyanine green in plasma, aqueous solution and whole blood

Fluorescence-based imaging has evolved into an important technology during recent years. Specifically indocyanine green (ICG) has invaded most fields of diagnostic and interventional medicine. Considering the numerous advantages of the substance like the rapid degradation and rare adverse reactions, ICG is currently the most commonly used fluorescing agent. High-performance liquid chromatography (HPLC) was used for measuring absorbance and fluorescence of ICG and its potential degradation compounds. Stability and degradation were evaluated under light exposure or in darkness at various temperatures. Under these conditions, degradation of ICG was evaluated over a period of 11 days. Additional, stability measurements of ICG were performed in EDTA whole blood samples at 37 °C incubation temperature while monitoring. Furthermore, we used mass spectrometric (MS) and nuclear magnetic resonance (NMR) analyses for the identification of supposed ICG degradation compound. Potential quenching effect of ICG was examined in aqueous and plasma solutions at concentrations ranging from 0.01-100 μg ml-1. When diluted in water and stored at 4 °C in the dark, ICG is stable for three days with only 20% of fluorescence intensity lost in this time-span. ICG incubated at 37 °C in whole blood under light exposure is stable for 5 h. In our study we observed the degradation of ICG into two degradation compounds with a mass of m/z 785.32 and m/z 1501.57, respectively. Based on our observations we suggest that ICG should be used within one or two days after preparation, if the ICG solution is stored at 4 °C.

Cathepsin B-degradable, NIR-responsive nanoparticulate platform for target-specific cancer therapy

Stimuli-responsive anticancer formulations can promote drug release and activation within the target tumour, facilitate cellular uptake, as well as improve the therapeutic efficacy of drugs and reduce off-target effects. In the present work, indocyanine green (ICG)-containing polyglutamate (PGA) nanoparticles were developed and characterized. Digestion of nanoparticles with cathepsin B, a matrix metalloproteinase overexpressed in the microenvironment of advanced tumours, decreased particle size and increased ICG cellular uptake. Incorporation of ICG in PGA nanoparticles provided the NIR-absorbing agent with time-dependent altered optical properties in the presence of cathepsin B. Having minimal dark toxicity, the formulation exhibited significant cytotoxicity upon NIR exposure. Combined use of the formulation with saporin, a ribosome-inactivating protein, resulted in synergistically enhanced cytotoxicity attributed to the photo-induced release of saporin from endo/lysosomes. The results suggest that this therapeutic approach can offer significant therapeutic benefit in the treatment of superficial malignancies, such as head and neck tumours.

Indocyanine green delivery systems for tumour detection and treatments

Indocyanine green (ICG) is a cyanine compound that displays fluorescent properties in the near infrared region. This dye is employed for numerous indications but nowadays its major application field regards tumour diagnosis and treatments. Optical imaging by near infrared fluorescence provides news opportunities for oncologic surgery. The imaging of ICG can be useful for intraoperative identification of several solid tumours and metastases, and sentinel lymph node detection. In addition, ICG can be used as an agent for the destruction of malignant tissue, by virtue of the production of reactive oxygen species and/or induction of a hyperthermia effect under irradiation. Nevertheless, ICG shows several drawbacks, which limit its clinical application. Several formulative strategies have been studied to overcome these problems. The rationale of the development of ICG containing drug delivery systems is to enhance the in vivo stability and biodistribution profile of this dye, allowing tumour accumulation and resulting in better efficacy. In this review, ICG containing nano-sized carriers are classified based on their chemical composition and structure. In addition to nanosystems, different formulations including hydrogel, microsystems and others loaded with ICG will be illustrated. In particular, this report describes the preparation, in vitro characterization and in vivo application of ICG platforms for cancer imaging and treatment. The promising results of all systems confirm their clinical utility but further studies are required prior to evaluating the formulations in human trials.

Molecular imaging-guided photothermal/photodynamic therapy against tumor by iRGD-modified indocyanine green nanoparticles

Multifunctional near-infrared (NIR) nanoparticles demonstrate great potential in tumor theranostic applications. To achieve the sensitive detection and effective phototherapy in the early stage of tumor genesis, it is highly desirable to improve the targeting of NIR theranostic agents to biomarkers and to enhance their accumulation in tumor. Here we report a novel targeted multifunctional theranostic nanoparticle, internalized RGD (iRGD)-modified indocyanine green (ICG) liposomes (iRGD-ICG-LPs), for molecular imaging-guided photothermal therapy (PTT) and photodynamic therapy (PDT) therapy against breast tumor. The iRGD peptides with high affinity to αvβ3 integrin and effective tumor-internalized property were firstly used to synthesize iRGD-PEG2000-DSPE lipopeptides, which were further utilized to fabricate the targeted ICG liposomes. The results indicated that iRGD-ICG-LPs exhibited excellent stability and could provide an accurate and sensitive detection of breast tumor through NIR fluorescence molecular imaging. We further employed this nanoparticle for tumor theranostic application, demonstrating significantly higher tumor accumulation and tumor inhibition efficacy through PTT/PDT effects. Histological analysis further revealed much more apoptotic cells, confirming the advantageous anti-tumor effect of iRGD-ICG-LPs over non-targeted ICG-LPs. Notably, the targeting therapy mediated by iRGD provides almost equivalent anti-tumor efficacy at a 12.5-fold lower drug dose than that by monoclonal antibody, and no tumor recurrence and obvious treatment-induced toxicity were observed in our study. Our study provides a promising strategy to realize the sensitive detection and effective treatment of tumors by integrating molecular imaging into PTT/PDT therapy.

Current use and perspective of indocyanine green clearance in liver diseases

Indocyanine green (ICG) is a water-soluble anionic compound that binds to plasma proteins after intravenous administration. It is selectively taken up at the first pass by hepatocytes and excreted unchanged into the bile. With the development of ICG elimination measurement by spectrophotometry, the ICG retention test has become a safe, rapid, reproducible, inexpensive and noninvasive tool for the assessment of liver function. Clinical evidence suggests that the ICG retention test can enable the establishment of tailored management strategies by providing prognostic information. In particular, this method has been evaluated as a prognostic marker in patients with advanced cirrhosis or awaiting liver transplantation. In addition, it is used as a marker of portal hypertension in cirrhotic patients, as a prognostic factor in intensive care units and for the assessment of liver function in patients undergoing liver surgery. Since recent technology enables ICG-PDR to be measured noninvasively at the bedside, this parameter is an attractive addition to liver function and regional haemodynamic monitoring. However, the current state-of-the-art as concerns this technology remains at a low level of evidence and thorough assessment is required.

Micellar formulation of indocyanine green for phototherapy of melanoma

Phototherapy (PT), a light activated treatment modality, is a potential therapeutic option for the treatment of melanoma. In spite of the excellent safety profile and absorption in the near infrared (NIR) range, clinical potential of indocyanine green (ICG) as PT is limited by its short half-life and inefficient tumor accumulation. In this study, we have covalently conjugated ICG-NH2 to the pendant carboxyl groups of poly (ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate) (PEG-PCC) copolymer using carbodiimide coupling, which self-assembled into micelles with a particle size of 30-50 nm and high ICG loading. These ICG conjugated micelles exhibited significant in vitro photodynamic cytotoxicity. Use of sodium azide and NIR radiate on at 4 °C revealed photodynamic and photothermal as mechanism of cytotoxicity of ICG solution and ICG conjugated micelles, respectively. In vivo NIR imaging demonstrated that ICG conjugated micelles prolonged its circulation and increased tumor accumulation through enhanced permeability and retention (EPR) effect. Enhanced tumor accumulation improved therapeutic efficacy with complete tumor regression in NIR irradiated ICG conjugated micelles compared to ICG solution and control in a A375 human melanoma tumor model in athymic nude mice. These results suggest that ICG conjugated micelles can be potentially utilized for PT and imaging of melanoma.

Fluorescence in neurosurgery: Its diagnostic and therapeutic use. Review of the literature

Fluorescent agents, e.g. 5-aminolevulinic acid (5-ALA), fluorescein and indocyanine green (ICG) are in common use in neurosurgery for tumor resection and neurovascular surgery. Protoporphyrine IX (PPIX) as major metabolite of 5-ALA is a strong fluorescent substance accumulated within malignant glioma tissue and a very sensitive and specific tool for visualizing high grade glioma tissue during surgery. Furthermore, 5-ALA or rather PPIX also offers an intratumoral therapeutic option stimulated by laser light in specific wavelength. Fluorescein was demonstrated to show similar fluorescent reactions in neurosurgery, but is controversial in its use, especially in high grade tumor surgery. Intraoperative angiography during resection of arterio-venous malformations, extracranial-intracranial-bypass or aneurysm surgery is supported by ICG fluorescence. Generally ICG will provide beneficial information for both, exposure of the pathology and illustration of healthy structures. This manuscript shows an overview of the literature focussing fluorescence in neurosurgery.

Indocyanine green targeted micelles with improved stability for near-infrared image-guided photothermal tumor therapy

Aim: Indocyanine green (ICG) is a promising near-infrared (NIR) dye for tumor imaging and photothermal therapy; however, the poor stability and lack of targeting limit its application. In this study, ICG was encapsulated into folate-conjugated poly(2-ethyl-2-oxazoline)-b-poly(ε-caprolactone) micelles to overcome these problems. Materials & methods: ICG-loaded micelles were prepared by solvent evaporation method. Cell uptake and in vitro photothermal cytotoxicity were evaluated on KB cells. In vivo NIR imaging and photothermal therapy were conducted on KB tumor-bearing mice. Results: ICG-loaded micelles with favorable sizes and stable NIR optical properties were successfully prepared. These micelles could target to KB tumors and enabled high-resolution NIR imaging. Moreover, they could effectively convert the absorbed NIR laser energy into heat, resulting in significant tumor damage and inhibition. Conclusion: This novel micellar system, integrating stable NIR properties, excellent tumor targeting and photothermal capability, showed great potential in tumor imaging and therapy.

Indocyanine green-loaded nanoparticles for image-guided tumor surgery

Detecting positive tumor margins and local malignant masses during surgery is critical for long-term patient survival. The use of image-guided surgery for tumor removal, particularly with near-infrared fluorescent imaging, is a potential method to facilitate removing all neoplastic tissue at the surgical site. In this study we demonstrate a series of hyaluronic acid (HLA)-derived nanoparticles that entrap the near-infrared dye indocyanine green, termed NanoICG, for improved delivery of the dye to tumors. Self-assembly of the nanoparticles was driven by conjugation of one of three hydrophobic moieties: aminopropyl-1-pyrenebutanamide (PBA), aminopropyl-5β-cholanamide (5βCA), or octadecylamine (ODA). Nanoparticle self-assembly, dye loading, and optical properties were characterized. NanoICG exhibited quenched fluorescence that could be activated by disassembly in a mixed solvent. NanoICG was found to be nontoxic at physiologically relevant concentrations and exposure was not found to inhibit cell growth. Using an MDA-MB-231 tumor xenograft model in mice, strong fluorescence enhancement in tumors was observed with NanoICG using a fluorescence image-guided surgery system and a whole-animal imaging system. Tumor contrast with NanoICG was significantly higher than with ICG alone.

An integrated widefield imaging and spectroscopy system for contrast-enhanced, image-guided resection of tumors

Tumor recurrence following surgery is a common and unresolved medical problem of great importance since surgery is the most widely used treatment for solid-mass tumors worldwide. A contributing factor to tumor recurrence is the presence of residual tumor remaining at or near the surgical site following surgery.

GOAL

The primary objective of this study was to develop and evaluate an image-guided surgery system based on a near-infrared, handheld excitation source and spectrograph in combination with a widefield video imaging system.

METHODS

This system was designed to detect the fluorescence of near-infrared contrast agents and, in particular, indocyanine green (ICG). The imaging system was evaluated for its optical performance and ability to detect the presence of ICG in tumors in an ectopic murine tumor model as well as in spontaneous tumors arising in canines.

RESULTS

In both settings, an intravenous ICG infusion provided tumor contrast. In both the murine models and surgical specimens from canines, ICG preferentially accumulated in tumor tissue compared to surrounding normal tissue. The resulting contrast was sufficient to distinguish neoplasia from normal tissue; in the canine surgical specimens, the contrast was sufficient to permit identification of neoplasia on the marginal surface of the specimen.

CONCLUSION

These results demonstrate a unique concept in image-guided surgery by combining local excitation and spectroscopy with widefield imaging.

SIGNIFICANCE

The ability to readily detect ICG in canines with spontaneous tumors in a clinical setting exemplifies the potential for further clinical translation; the promising results of detecting neoplasia on the marginal specimen surface underscore the clinical utility.

Self-assembly-induced near-infrared fluorescent nanoprobes for effective tumor molecular imaging

Self-assembly-induced near-infrared fluorescent nanoprobes exhibiting spontaneous lattices were prepared and evaluated for in vitro and in vivo tumor molecular imaging.

Towards non-invasive characterization of breast cancer and cancer metabolism with diffuse optics

We review recent developments in diffuse optical imaging and monitoring of breast cancer, i.e. optical mammography. Optical mammography permits non-invasive, safe and frequent measurement of tissue hemodynamics oxygen metabolism and components (lipids, water, etc.), the development of new compound indices indicative of the risk and malignancy, and holds potential for frequent non-invasive longitudinal monitoring of therapy progression.

Near-infrared imaging of breast cancer using optical contrast agents

Breast cancer is the most common malignancy in women worldwide and the second leading cause of cancer death. On the basis of three studies performed by our group, this article reviews the current status of optical breast imaging using extrinsic contrast agents. To date, only two contrast agents have been applied in human studies, indocyanine green (ICG) and omocianine. Both contrast media were used for absorption and fluorescence imaging. Generally speaking, malignant breast lesions exhibited higher absorption contrast as well as higher fluorescence contrast compared to benign lesions or non-diseased breast tissue. Some groups consider early enhancement characteristics helpful for differentiation between malignant and benign lesions. Late fluorescence ICG imaging - capitalizing on the extravasation of the dye through the wall of tumorous vessels - seems to be a promising technique to distinguish malignant from benign breast lesions.

Gadolinium-doped silica nanoparticles encapsulating indocyanine green for near infrared and magnetic resonance imaging

Clinical applications of the indocyanine green (ICG) dye, the only near infrared (NIR) imaging dye approved by the Food and Drug Administration (FDA) in the USA, are limited due to rapid protein binding, fast clearance, and instability in physiologically relevant conditions. Encapsulating ICG in silica particles can enhance its photostability, minimize photobleaching, increase the signal-to-noise (S/N) ratio and enable in vivo studies. Furthermore, a combined magnetic resonance (MR) and NIR imaging particulate can integrate the advantage of high-resolution 3D anatomical imaging with high-sensitivity deep-tissue in-vivo fluorescent imaging. In this report, a novel synthesis technique that can achieve these goals is presented. A reverse-microemulsion-based synthesis protocol is employed to produce 25 nm ICG-doped silica nanoparticles (NPs). The encapsulation of ICG is achieved by manipulating coulombic attractions with bivalent ions and aminated silanes and carrying out silica synthesis in salt-catalyzed, mildly basic pH conditions using dioctyl sulfosuccinate (AOT)/heptane/water microemulsion system. Furthermore, paramagnetic properties are imparted by chelating paramagnetic Gd to the ICG-doped silica NPs. Aqueous ICG-dye-doped silica NPs show increased photostability (over a week) and minimal photobleaching as compared to the dye alone. The MR and optical imaging capabilities of these particles are demonstrated through phantom, in vitro and in vivo experiments. The described particles have the potential to act as theranostic agents by combining photodynamic therapy through the absorption of NIR irradiated light.

Fluorescent angiography

Fluorescent angiography is a simple and effective real-time tool for measurement of tissue perfusion both in and out of the operating room. It has multiple uses including: (1) identifying perforating vessels during flap planning; (2) locating primary and secondary angiosomes within a prepared flap; (3) as an aid in decision making for tissue debridement and flap creation; (4) intraoperative evaluation of microanastomoses; (5) postoperative flap monitoring, and (6) documentation of perfusion. The technology is easy to use in the hands of the operating surgeon and is safe for the patient, as it requires no radiation exposure.