In Vivo Pharmacokinetics Assessment of Indocyanine Green-Loaded Nanoparticles in Tumor Tissue with a Dynamic Diffuse Fluorescence Tomography System

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Illumination pattern optimization in tomography based on the Kalman estimation filter and optimal experiment design

Tomography is widely used in medical imaging or industrial non-destructive testing applications. One costly and time consuming operation in any form of tomography is the process of data acquisition where a large number of measurements are made and collected data is used for image reconstruction. Data acquisition can slow down tomography to the point that the scanner cannot catch up with the speed of changes in the medium under test. By optimizing the information content of each measurement, we can reduce the number of measurements needed to achieve the target precision. Development of algorithms to optimize the information content of tomography measurements is the main goal of this article. Here, the dynamics of the medium and tomography measurements are formulated in the form of a Kalman estimation filter. A mathematical algorithm is developed to compute the optimal measurement matrix which minimizes the uncertainty left in the estimation of the distribution the tomography scanner is reconstructing. Results, as presented in the paper, show noticeable improvement is the quality of generated images when the medium is scanned by optimal measurements instead of traditional raster or random scanning protocols.

Multi-channel Small Animal Drug Metabolism Real-Time Monitoring Fluorescence System

PURPOSE

The data acquisition of drug metabolism analysis requires a lot of time and animal resources. However, there are often many deviations in the results of pharmacokinetic analysis. Conventional methods cannot measure the blood drug concentration data in multiple tissues at the same time, and the data is obtained by in vitro measurement, which produces time errors, in vitro data errors, and individual differences between animals. In the analysis of pharmacokinetic parameters, it will seriously affect the pass rate of clinical trials of R&D drugs and the accuracy of the dosing schedule. To the best of our knowledge, we have not found the study of in vivo blood drug concentration using multi-channel equipment. Therefore, the purpose of this paper is to build a set of multi-organ monitoring and analysis instruments for synchronously monitoring the metabolism of drugs in various tissues of small animals, so as to obtain real in vivo data of blood drug concentration in real time.

PROCEDURES

Using the fluorescence properties and laser-induced fluorescence principle of drugs, we designed six channels to monitor the changes of fluorescence-labeled drugs in their main metabolic organs, a multi-channel calibration method was proposed to improve the accuracy of the time-division multiplexing, the real-time collection of drug concentration in vivo is realized, and the drug metabolism curve in vivo can be observed.

RESULTS

The instrument satisfies the collection of small doses of drugs such as microgram; the detection sensitivity can reach 10 ng/ml, and can monitor and collect the drug metabolism of multiple small animal tissues at the same time, which greatly reduces the use of animals, reduces the differences between individuals, and reduces consumption cost and improve the detection efficiency of parameters, and obtain data information that is closer to the real biology.

CONCLUSION

The real-time continuous monitoring and data collection of the drug metabolism in the plasma of living small animals and the important organs such as kidney, liver, and spleen were realized. The research and development of new drugs and clinical research have higher practical value.

Optimal data acquisition in tomography

In tomography, three-dimensional images of a medium are reconstructed from a set of two-dimensional projections. Each projection is the result of a measurement made by the scanner via radiating some form of energy and collecting the scattered field after interacting with the medium. The information content of these measurements is not equal, and one projection can be more informative than others. By choosing the most informative measurement at every step of scanning, an optimal tomography system can maximize the speed of data acquisition and temporal resolution of acquired images, reducing the operation cost and exposure to possible harmful radiations. The aim of this paper is to introduce mathematical algorithms that can be used to design measurements with optimal information content when imaging static or dynamically evolving objects.

A Light-Responsive Injectable Hydrogel with Remodeling Tumor Microenvironment for Light-Activated Chemodynamic Therapy

Chemodynamic therapy (CDT) based on Fenton-like reaction is often limited by the tumor microenvironment (TME), which has insufficient hydrogen peroxide, and single CDT treatment is often less efficacious. To overcome these limitations, a hydrogel-based system is designed to enhance the redox stress (EOH) by loading the composite nanomaterial Cu-Hemin-Au, into the agarose hydrogels. The hydrogels can reach the tumor site upon intratumoral injection, and then coagulate and stay for extended period. Once irradiated with near-infrared light, the Cu-Hemin-Au act as a photothermal agent to convert the light energy into heat, and the EOH gradually heated up and softened, releasing the Cu-Hemin-Au residing in it to achieve photothermal therapy (PTT). Benefiting from the glucose oxidase (GOx)-like activity of the Au nanoparticles, glucose in the tumor cells is largely consumed, and hydrogen peroxide (H₂ O₂ ) is generated in situ, and then Cu-Hemin-Au react with sufficient H₂ O₂ to generate a large amount of reactive oxygen species, which promote the complete inhibition of tumor growth in mice during the treatment cycle. The hydrogel system for the synergistic enhancement of oxidative stress achieves good PTT/CDT synergy, providing a novel inspiration for the next generation of hydrogels for application in antitumor therapy.

High-sensitivity dynamic diffuse fluorescence tomography system for fluorescence pharmacokinetics

SIGNIFICANCE

Dynamic diffuse fluorescence tomography (DFT) can recover the static distribution of fluorophores and track dynamic temporal events related to physiological and disease progression. Dynamic imaging indocyanine green (ICG) approved by the food and drug administration is still under-exploited because of its characteristics of low quantum yield and relatively rapid tissue metabolism.

AIM

In order to acquire the ICG tomographic image sequences for pharmacokinetic analysis, a dynamic DFT system was proposed.

APPROACH

A fiber-based dynamic DFT system adopts square-wave modulation lock-in photon-counting scheme and series-parallel measurement mode, which possesses high sensitivity, large dynamic range, high anti-ambient light ability in common knowledge, as well as good cost performance. In order to investigate the effectiveness of the proposed system, the measurement stability and the anti-crosstalk-a crucial factor affecting the system parallelization-were assessed firstly, then a series of static phantoms, dynamic phantoms and in vivo mice experiments were conducted to verify the imaging capability.

RESULTS

The system has the limited dynamic range of 100 dB, the fluctuation of photon counting within 3%, and channel-to-channel crosstalk ratio better than 1.35. Under the condition of a sufficient signal-to-noise ratio, a complete measurement time for one frame image was 10.08 s. The experimental results of static phantoms with a single target and three targets showed that this system can accurately obtain the positions, sizes, and shapes of the targets and the reconstructed images exhibited a high quantitativeness. Further, the self-designed dynamic phantom experiments demonstrated the capability of the system to capture fast changing fluorescence signals. Finally, the in vivo experiments validated the practical capability of the system to effectively track the ICG metabolism in living mice.

CONCLUSIONS

These results demonstrate that our proposed system can be utilized for assessing ICG pharmacokinetics, which may provide a valuable tool for tumor detection, drug assessment, and liver function evaluation.

Functionalized NIR-II Semiconducting Polymer Nanoparticles for Single-cell to Whole-Organ Imaging of PSMA-Positive Prostate Cancer

Development of molecular probes holds great promise for early diagnosis of aggressive prostate cancer. Here, 2-[3-(1,3-dicarboxypropyl) ureido] pentanedioic acid (DUPA)-conjugated ligand and bis-isoindigo-based polymer (BTII) are synthesized to formulate semiconducting polymer nanoparticles (BTII-DUPA SPN) as a prostate-specific membrane antigen (PSMA)-targeted probe for prostate cancer imaging in the NIR-II window. Insights into the interaction of the imaging probes with the biological targets from single cell to whole organ are obtained by transient absorption (TA) microscopy and photoacoustic (PA) tomography. At single-cell level, TA microscopy reveals the targeting efficiency, kinetics, and specificity of BTII-DUPA SPN to PSMA-positive prostate cancer. At organ level, PA tomographic imaging of BTII-DUPA SPN in the NIR-II window demonstrates superior imaging depth and contrast. By intravenous administration, BTII-DUPA SPN demonstrates selective accumulation and retention in the PSMA-positive tumor, allowing noninvasive PA detection of PSMA overexpressing prostate tumors in vivo. The distribution of nanoparticles inside the tumor tissue is further analyzed through TA microscopy. These results collectively demonstrate BTII-DUPA SPN as a promising probe for prostate cancer diagnosis by PA tomography.