Indocyanine green nanoparticles undergo selective lymphatic uptake, distribution and retention and enable detailed mapping of lymph vessels, nodes and abnormalities

Nano-fluorescence imaging: advancing lymphatic disease diagnosis and monitoring

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

Drug Combination Nanoparticles Containing Gemcitabine and Paclitaxel Enable Orthotopic 4T1 Breast Tumor Regression

Early diagnosis, intervention, and therapeutic advancements have extended the lives of breast cancer patients; however, even with molecularly targeted therapies, many patients eventually progress to metastatic cancer. Recent data suggest that residual breast cancer cells often reside in the lymphatic system before rapidly spreading through the bloodstream. To address this challenge, an effective drug combination composed of gemcitabine (G) and paclitaxel (T) is administered intravenously in sequence at the metastatic stage, but intravenous GT infusion may limit lymphatic GT drug accessibility and asynchronous drug exposure in cancer cells within the lymph. To determine whether co-localization of intracellular gemcitabine and paclitaxel (referred to as GT) could overcome these limitations and enhance the efficacy of GT, we have evaluated a previously reported GT drug-combination formulated in nanoparticle (referred to as GT-in-DcNP) evaluated in an orthotopic breast tumor model. Previously, with indocyanine green-labeled nanoparticles, we reported that GT-in-DcNP particles after subcutaneous dosing were taken up rapidly and preferentially into the lymph instead of blood vessels. The pharmacokinetic study showed enhanced co-localization of GT within the tumors and likely through lymphatic access, before drug apparency in the plasma leading to apparent long-acting plasma time-course. The mechanisms may be related to significantly greater inhibitions of tumor growth-by 100 to 140 times-in both sub-iliac and axillary regions compared to the equivalent dosing with free-and-soluble GT formulation. Furthermore, GT-in-DcNP exhibited dose-dependent effects with significant tumor regression. In contrast, even at the highest dose of free GT combination, only a modest tumor growth reduction was notable. Preliminary studies with MDA-231-HM human breast cancer in an orthotopic xenograft model indicated that GT-in-DcNP may be effective in suppressing human breast tumor growth. Taken together, the synchronized delivery of GT-in-DcNP to mammary tumors through the lymphatic system offers enhanced cellular retention and greater efficacy.

Stepwise Ultra-pH-Sensitive Micelles Overcome a pKa Barrier for Systemic Lymph Node Delivery

While local nanoparticle delivery to lymph nodes is well studied, there are few design criteria for intravenous delivery to the entire lymph node repertoire. In this study, we investigated the effect of NP pH transition on lymph node targeting by employing a series of ultra-pH-sensitive (UPS) polymeric micelles. The UPS library responds to pH thresholds (pKa 6.9, 6.2, and 5.3) over a range of physiological pH. We observed a dependence of intravenous lymph node targeting on micelle pH transition. UPS6.9 (subscript indicates pKa) shows poor lymph node delivery, while UPS5.3 delivers efficiently to lymph node sets. We investigated targeting mechanisms of UPS5.3, observing an accumulation among lymph node lymphatics and a dependence on lymph node-resident macrophages. To overcome the pH-threshold barrier, which limits UPS6.9, we rationally designed a nanoparticle coassembly of UPS6.9 with UPS5.3, called HyUPS. The HyUPS micelle retains the constitutive pH transitions of each polymer, showing stepwise responses to discrete pH thresholds. We demonstrate that HyUPS improves UPS6.9 delivery to lymph nodes, extending this platform for disease detection of lymph node metastasis.

Physiologically based Pharmacokinetic Model Validated to Enable Predictions Of Multiple Drugs in a Long-acting Drug-combination Nano-Particles (DcNP): Confirmation with 3 HIV Drugs, Lopinavir, Ritonavir, and Tenofovir in DcNP Products

Drug-Combination Nanoparticles (DcNP) are a novel drug delivery system designed for synchronized delivery of multiple drugs in a single, long-acting, and targeted dose. Unlike depot formulations, slowly releasing drug at the injection site into the blood, DcNP allows multiple-drug-in-combination to collectively distribute from the injection site into the lymphatic system. Two distinct classes of long-acting injectables products are proposed based on pharmacokinetic mechanisms. Class I involves sustained release at the injection site. Class II involves a drug-carrier complex composed of lopinavir, ritonavir, and tenofovir uptake and retention in the lymphatic system before systemic access as a part of the PBPK model validation. For clinical development, Class II long-acting drug-combination products, we leverage data from 3 nonhuman primate studies consisting of nine PK datasets: Study 1, varying fixed-dose ratios; Study 2, short multiple dosing with kinetic tails; Study 3, long multiple dosing (chronic). PBPK validation criteria were established to validate each scenario for all drugs. The models passed validation in 8 of 9 cases, specifically to predict Study 1 and 2, including PK tails, with ritonavir and tenofovir, fully passing Study 3 as well. PBPK model for lopinavir in Study 3 did not pass the validation due to an observable time-varying and delayed drug accumulation, which likely was due to ritonavir's CYP3A inhibitory effect building up during multiple dosing that triggered a mechanism-based drug-drug interaction (DDI). Subsequently, the final model enables us to account for this DDI scenario.

Delivering CRISPR to the HIV-1 reservoirs

Human immunodeficiency virus type 1 (HIV-1) infection is well known as one of the most complex and difficult viral infections to cure. The difficulty in developing curative strategies arises in large part from the development of latent viral reservoirs (LVRs) within anatomical and cellular compartments of a host. The clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein 9 (CRISPR/Cas9) system shows remarkable potential for the inactivation and/or elimination of integrated proviral DNA within host cells, however, delivery of the CRISPR/Cas9 system to infected cells is still a challenge. In this review, the main factors impacting delivery, the challenges for delivery to each of the LVRs, and the current successes for delivery to each reservoir will be discussed.

A novel formulation enabled transformation of 3-HIV drugs tenofovir-lamivudine-dolutegravir from short-acting to long-acting all-in-one injectable

OBJECTIVE

To develop an injectable dosage form of the daily oral HIV drugs, tenofovir (T), lamivudine (L), and dolutegravir (D), creating a single, complete, all-in-one TLD 3-drug-combination that demonstrates long-acting pharmacokinetics.

DESIGN

Using drug-combination-nanoparticle (DcNP) technology to stabilize multiple HIV drugs, the 3-HIV drugs TLD, with disparate physical-chemical properties, are stabilized and assembled with lipid-excipients to form TLD-in-DcNP . TLD-in-DcNP is verified to be stable and suitable for subcutaneous administration. To characterize the plasma time-courses and PBMC concentrations for all 3 drugs, single subcutaneous injections of TLD-in-DcNP were given to nonhuman primates (NHP, M. nemestrina ).

RESULTS

Following single-dose TLD-in-DcNP , all drugs exhibited long-acting profiles in NHP plasma with levels that persisted for 4 weeks above predicted viral-effective concentrations for TLD in combination. Times-to-peak were within 24 hr in all NHP for all drugs. Compared to a free-soluble TLD, TLD-in-DcNP provided exposure enhancement and extended duration 7.0-, 2.1-, and 20-fold as AUC boost and 10-, 8.3-, and 5.9-fold as half-life extension. Additionally, DcNP may provide more drug exposure in cells than plasma with PBMC-to-plasma drug ratios exceeding one, suggesting cell-targeted drug-combination delivery.

CONCLUSIONS

This study confirms that TLD with disparate properties can be made stable by DcNP to enable TLD concentrations of 4 weeks in NHP. Study results highlighted the potential of TLD-in-DcNP as a convenient all-in-one, complete HIV long-acting product for clinical development.

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.

Laboratory scoring system to predict hepatic indocyanine green clearance ability during fluorescence imaging-guided laparoscopic hepatectomy

BACKGROUND

Indocyanine green (ICG) fluorescence played an important role in tumor localization and margin delineation in hepatobiliary surgery. However, the preoperative regimen of ICG administration was still controversial. Factors associated with tumor fluorescence staining effect were unclear.

AIM

To investigate the preoperative laboratory indexes corelated with ICG fluorescence staining effect and establish a novel laboratory scoring system to screen specifical patients who need ICG dose adjustment.

METHODS

To investigate the predictive indicators of ICG fluorescence characteristics in patients undergoing laparoscopic hepatectomy from January 2018 to January 2021 were included. Blood laboratory tests were completed within 1 wk before surgery. All patients received 5 mg ICG injection 24 h before surgery for preliminary tumor imaging. ImageJ software was used to measure the fluorescence intensity values of regions of interest. Correlation analysis was used to identify risk factors. A laboratory risk model was established to identify individuals at high risk for high liver background fluorescence.

RESULTS

There were 110 patients who were enrolled in this study from January 2019 to January 2021. The mean values of fluorescence intensity of liver background (FI-LB), fluorescence intensity of gallbladder, and fluorescence intensity of target area were 18.87 ± 17.06, 54.84 ± 33.29, and 68.56 ± 36.11, respectively. The receiver operating characteristic (ROC) curve showed that FI-LB was a good indicator for liver clearance ability [area under the ROC curve (AUC) = 0.984]. Correlation analysis found pre-operative aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transpeptidase, adenosine deaminase, and lactate dehydrogenase were positively associated with FI-LB and red blood cell, cholinesterase, and were negatively associated with FI-LB. Total laboratory risk score (TLRS) was calculated according to ROC curve (AUC = 0.848, sensitivity = 0.773, specificity = 0.885). When TLRS was greater than 6.5, the liver clearance ability of ICG was considered as poor.

CONCLUSION

Preoperative laboratory blood indicators can predict hepatic ICG clearance ability. Surgeons can adjust the dose and timing of ICG preoperatively to achieve better liver fluorescent staining.

Evaluation of Longitudinal Lymphatic Function Changes upon Injury in the Mouse Tail with Photodynamic Therapy

PURPOSE

The lymphatic system is an essential but often understudied component of the circulatory system in comparison with its cardiovascular counterpart. Such disparity could often be explained by the difficulty in imaging lymphatics and the specialized microsurgical skills that are often required for lymphatic injury models. Recently, it has been shown that verteporfin, a photosensitive drug used for photodynamic therapy (PDT) to ablate the blood vessels, provides a similar effect on lymphatic vessels. Here, we seek to administer verteporfin and perform a modified form of PDT on collecting lymphatics in the mouse tail, a commonly used location for the study of lymphatic disorders, and examine lymphatic remodeling, contractility, and transport in response to the procedure.

METHODS

Mice collecting lymphatics in the tail were injured by PDT through an intradermal injection of verteporfin in the distal tip of the tail followed by light activation on the proximal portion of the tail downstream of the injection site. Lymphatic function was evaluated using a near-infrared (NIR) imaging system weekly for up to 28 days after injury.

RESULTS

PDT resulted in a loss in lymphatic function contractile frequency that persisted for up to 7 days after injury. Packet transport and packet amplitude, measurements reflective of the strength of contraction, were significantly reduced 14 days after injury. The lymphatics showed a delayed increase in lymphatic leakage at 7 days that persisted until the study endpoint on day 28.

CONCLUSION

This technique provides an easy-to-use method for injuring lymphatics to understand their remodeling response to injury by PDT as well as potentially for screening therapeutics that seek to normalize lymphatic permeability or contractile function after injury.

Water-soluble near-infrared fluorescent heptamethine dye for lymphatic mapping applications

The identification of sentinel lymph node (SLN) is an important method for prognostic evaluation and minimally invasive staging of metastatic tumors. Here, we report a series of near-infrared fluorescent heptamethylamine dyes (series A, B and C) with central cycloalkene ring modified by tyrosine or N-Boc tyrosine via ether linkage. N-Boc tyrosine/tyrosine modification provided enhanced absorption coefficient and fluorescence quantum yield in DMSO, however with slight hypsochromic shift compared to the mother dyes in DMSO. In PBS, series A and B were found to be more fluorescent than ICG and showed brighter images. Compound A1 was found to exhibit the most favorable imaging performance among all the dyes investigated and was selected for in vivo sentinel lymph node mapping experiments in mice. A1 showed faster response and stronger fluorescence emission than FDA-approved ICG. The lymph node tracing with A1 could be assisted by MB staining. Ex vivo imaging of harvested organs indicated that similar metabolic characteristics of A1 and ICG. Overall, A1 is advantageous over ICG and is very promising for non-invasive lymph node imaging.

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.

Host-guest interactions of indocyanine green with β-cyclodextrin permit real-time characterization of the rat lymphatic system

Objective

Fluorescence contrast technology using indocyanine green (ICG) could be useful for the rapid, dynamic, and objective assessment of blood vessels and the surrounding tissues when combined with near-infrared (NIR) imaging. Although ICG is a clinically available NIR fluorescence imaging probe, it can easily aggregate and is, thus, unstable. In the present study, we examined the efficacy of a host–guest ICG–β-cyclodextrin (CD) complex, which is used in pharmaceutics to improve the water solubility, stability, and bioavailability of hydrophobic molecules, for NIR imaging after hind footpad administration in a rat model.

Methods

To verify the performance of the ICG-β-CD complex with the host–guest self-assembly method in vivo, we performed simultaneous small animal (IVIS Spectrum system; PerkinElmer, Waltham, MA) and clinical (DIGI-MIH-001 near-infrared fluorescence imaging system; Beijing Digital Precision Medical Technology Co, Ltd, Beijing, China) imaging and evaluated the fluorescent properties of the ICG-β-CD complex in the hind footpad model of Sprague-Dawley male rats.

Results

We successfully prepared the ICG-β-CD complex. Compared with ICG, in vivo experiments showed that this complex had reduced absorbance at 710 nm and increased absorbance at 780 nm, indicating that it could prevent the dimeric aggregation of ICG, and a significantly higher fluorescence intensity at 730 nm excitation. After injection of 1.25 mg/mL of ICG or ICG-β-CD complex solutions into the rat hind footpad, fluorescent NIR lymphatic images were observed with both imaging systems. During the 12-hour observation period, the signal background ratio of ICG-β-CD showed a greater acute increase and a higher signal background ratio compared with ICG. The signal background ratio of ICG-β-CD was 125 to 100 from 260 to 540 minutes. These in vivo data suggest that ICG-β-CD has greater diffusion from the injection site and faster transport to the lymphatic system compared with ICG.

Conclusions

ICG-β-CD showed faster lymphatic transport than ICG, allowing for more rapid lymphatic NIR imaging. Thus, the ICG-β-CD complex might be a promising fluorescent agent for clinical lymphatic NIR imaging.

The lymphatic system plays a crucial role in maintaining tissue fluid homeostasis by draining protein-rich fluid from the perivascular interstitial spaces back into the circulation. The lymphatic system also plays a variety of roles in the progression of some peripheral vascular diseases, including venous leg ulcers, atherosclerotic vascular disease, and severe foot infection. Understanding the dynamic changes of the lymphatic fluid is indispensable for a variety of clinical situations and research areas. We investigated the potential feasibility of the indocyanine green–β-cyclodextrin complex in clinical applications using clinically available near-infrared fluorescence imaging equipment.

Physiologically Based Pharmacokinetic Modeling of 3 HIV Drugs in Combination and the Role of Lymphatic System after Subcutaneous Dosing. Part 2: Model for the Drug-combination Nanoparticles

We previously developed a mechanism-based pharmacokinetic (MBPK) model to characterize the PK of a lymphocyte-targeted, long-acting 3 HIV drug-combination nanoparticle (DcNP) formulation of lopinavir, ritonavir, and tenofovir. MBPK describes time-courses of plasma drug concentration and has provided an initial hypothesis for the lymphatic PK of DcNP. Because anatomical and physiological interpretation of MBPK is limited, in this Part 2, we report the development of a Physiologically Based Pharmacokinetic (PBPK) model for a detailed evaluation of the systemic and lymphatic PK of drugs associated with DcNP. The DcNP model is linked to the PBPK model presented earlier in Part 1 to account for the disposition of released free drugs. A key feature of the DcNP model is the uptake of the injected dose from the subcutaneous site to the adjacent lymphoid depot, routing through the nodes within and throughout the lymphatic network, and its subsequent passage into the blood circulation. Furthermore, the model accounts for DcNP transport to the lymph by lymphatic recirculation and mononuclear cell migration. The present PBPK model can be extended to other nano-drug combinations that target or transit through the lymphatic system. The PBPK model may allow scaling and prediction of DcNP PK in humans.

Preparation of the Biodegradable Lymphatic Targeting Imaging Agent Based on the Indocyanine Green Mesoporous Silicon System

The lymphatic system plays a crucial role in the immune system’s recognition and response to disease. Therefore, the imaging of the lymphatic system, especially lymphatic vessels, has emerged as a valuable tool for the diagnosis of metastasis. FDA-approved small-molecule dyes, namely, indocyanine green (ICG), have been widely applied to lymphatic vessels imaging. However, due to the small physical size, such molecule-based agents show no selectivity, and rapid clearance from lymph nodes. Herein, a biodegradable lymphatic targeting imaging agent based on the ICG-mesoporous silicon system (ICG@HMONs-HA) was obtained, which not only could target lymph vessels but also had a long residence time. The reported work provides a practical way for lymph vessel fluorescence imaging and paves the way for clinical translation of nanomaterial-based tracers.

Innovations in lymph node targeting nanocarriers

Lymph nodes are secondary lymphoid tissues in the body that facilitate the co-mingling of immune cells to enable and regulate the adaptive immune response. They are also tissues implicated in a variety of diseases, including but not limited to malignancy. The ability to access lymph nodes is thus attractive for a variety of therapeutic and diagnostic applications. As nanotechnologies are now well established for their potential in translational biomedical applications, their high relevance to applications that involve lymph nodes is highlighted. Herein, established paradigms of nanocarrier design to enable delivery to lymph nodes are discussed, considering the unique lymph node tissue structure as well as lymphatic system physiology. The influence of delivery mechanism on how nanocarrier systems distribute to different compartments and cells that reside within lymph nodes is also elaborated. Finally, current advanced nanoparticle technologies that have been developed to enable lymph node delivery are discussed.

Physiological models for in vivo imaging and targeting the lymphatic system: Nanoparticles and extracellular vesicles

Imaging of the lymphatic vasculature has gained great attention in various fields, not only because lymphatic vessels act as a key draining system in the body, but also for their implication in autoimmune diseases, organ transplant, inflammation and cancer. Thus, neolymphangiogenesis, or the generation of new lymphatics, is typically an early event in the development of multiple tumor types, particularly in aggressive ones such as malignant melanoma. Still, the understanding of how lymphatic endothelial cells get activated at distal (pre)metastatic niches and their impact on therapy is still unclear. Addressing these questions is of particular interest in the case of immune modulators, because endothelial cells may favor or halt inflammatory processes depending on the cellular context. Therefore, there is great interest in visualizing the lymphatic vasculature in vivo. Here, we review imaging tools and mouse models used to analyze the lymphatic vasculature during tumor progression. We also discuss therapeutic approaches based on nanomedicines to target the lymphatic system and the potential use of extracellular vesicles to track and target sentinel lymph nodes. Finally, we summarize main pre-clinical models developed to visualize the lymphatic vasculature in vivo, discussing their applications with a particular focus in metastatic melanoma.

Advances in Lymphedema

Lymphedema is a common, complex, and inexplicably underappreciated human disease. Despite a history of relative neglect by health care providers and by governmental health care agencies, the last decade has seen an explosive growth of insights into, and approaches to, the problem of human lymphedema. The current review highlights the significant advances that have occurred in the investigative and clinical approaches to lymphedema, particularly over the last decade. This review summarizes the progress that has been attained in the realms of genetics, lymphatic imaging, and lymphatic surgery. Newer molecular insights are explored, along with their relationship to future molecular therapeutics. Growing insights into the relationships among lymphedema, obesity, and other comorbidities are important to consider in current and future responses to patients with lymphedema.

Study on the Design and Optimization of a Portable Monitoring and Auxiliary Treatment Device for Upper Extremity Lymphedema-Focus on the Rehabilitation Function of the Device

Female patients suffer from the risk of upper limb lymphedema after breast cancer removal surgery. At present, the detection and the adjuvant treatment of this disease are not convenient enough, leading to delay of the disease and increase in the burden of patients. This paper presents a portable monitoring and treatment device for upper extremity lymphedema, enabling patients to monitor the symptoms of upper limb lymphedema and auxiliary rehabilitation. This design utilizes the arm circumference measurement and contrast method to realize symptom monitoring. The device realizes auxiliary rehabilitation using the regional pressure method to imitate traditional manual lymphatic drainage technology. According to the MRI images of volunteers’ upper limbs, the upper arm and forearm’s finite element models are reconstructed in ANSYS. The static simulation experiment is completed. The working mode and parameter design of each rehabilitation module of the device are obtained. The experimental results show that the integrated design principle of monitoring and treatment proposed in this paper has good feasibility, has auxiliary rehabilitation effect, and meets the principle of human comfort. The device can help patients find lymphedema in time and implement auxiliary treatment, which can effectively avoid the further deterioration of lymphedema.

Imaging technology of the lymphatic system

The lymphatic system plays critical roles in tissue fluid homeostasis and immunity and has been implicated in the development of many different pathologies, ranging from lymphedema, the spread of cancer to chronic inflammation. In this review, we first summarize the state-of-the-art of lymphatic imaging in the clinic and the advantages and disadvantages of these existing techniques. We then detail recent progress on imaging technology, including advancements in tracer design and injection methods, that have allowed visualization of lymphatic vessels with excellent spatial and temporal resolution in preclinical models. Finally, we describe the different approaches to quantifying lymphatic function that are being developed and discuss some emerging topics for lymphatic imaging in the clinic. Continued advancements in lymphatic imaging technology will be critical for the optimization of diagnostic methods for lymphatic disorders and the evaluation of novel therapies targeting the lymphatic system.

Predicting drug release and degradation kinetics of long-acting microsphere formulations of tacrolimus for subcutaneous injection

Today, tacrolimus represents a cornerstone of immunosuppressive therapy for liver and kidney transplants and remains subject of preclinical and clinical investigations, aiming at the development of long-acting depot formulations for subcutaneous injection. One major challenge arises from establishing in vitro-in vivo correlations due to the absence of meaningful in vitro methods predictive for the in vivo situation, together with a strong impact of multiple kinetic processes on the plasma concentration-time profile. In the present approach, two microsphere formulations were compared with regards to their in vitro release and degradation characteristics. A novel biorelevant medium provided the physiological ion and protein background. Release was measured using the dispersion releaser technology under accelerated conditions. A release of 100% of the drug from the carrier was achieved within 7 days. The capability of the in vitro performance assay was verified by the level A in vitro-in vivo correlation analysis. The contributions of in vitro drug release, drug degradation, diffusion rate and lymphatic transport to the absorption process were quantitatively investigated by means of a mechanistic modelling approach. The degradation rate, together with release and diffusion characteristics provides an estimate of the bioavailability and therefore can be a guide to future formulation development.

Inflow Occlusion Combined With Bleomycin Sclerotherapy for Management of Macro/Mixed Cystic Lymphatic Malformation in Children

Background: The link between cystic lymphatic malformation (cLM) and normal lymphatic system has become the focus of research. This study aimed to assess the outcomes of indocyanine green (ICG) lymphography-guided inflow occlusion combined with bleomycin sclerotherapy for the management of macro or mixed cLM in children. Methods: Between June 2018 and October 2020, inflow occlusion combined with bleomycin sclerotherapy was performed in 81 cLM patients (age range from 6 months to 8 years). All cases were evaluated by the following parameters: cLM location, histological typing, number of afferent lymph vessels, dermal backflow, curative effects, treatment frequency, and postoperative complications. The duration of postoperative follow-up was from 10 to 16 months. Results: All cLM cases could be found with at least one lymphatic inflow. Excellent outcomes were observed in 68 cases (84.0%), 11 cases (13.6%) experienced good outcomes, and two (2.5%) cases had fair outcome. No case experienced repeated treatment for more than three times. Wound infection, fever, and scar hyperplasia were the independent adverse events, which were managed by symptomatic treatment. Conclusion: Inflow occlusion combined with bleomycin sclerotherapy renders a safe and efficient approach for the management of macro or mixed cLM.

Evaluation of surgical procedures of mouse urethra by visualization and the formation of fistula

Visualization of the surgically operated tissues is vital to improve surgical model animals including mouse. Urological surgeries for urethra include series of fine manipulations to treat the increasing number of birth defects such as hypospadias. Hence visualization of the urethral status is vital. Inappropriate urethral surgical procedure often leads to the incomplete wound healing and subsequent formation of urethro-cutaneous fistula or urethral stricture. Application of indocyanine green mediated visualization of the urethra was first performed in the current study. Indocyanine green revealed the bladder but not the urethral status in mouse. Antegrade injection of contrast agent into the bladder enabled to detect the urethral status in vivo. The visualization of the leakage of contrast agent from the operated region was shown as the state of urethral fistula in the current hypospadias mouse model and urethral stricture was also revealed. A second trial for contrast agent was performed after the initial operation and a tendency of accelerated urethral stricture was observed. Thus, assessment of post-surgical conditions of urogenital tissues can be improved by the current analyses on the urethral status.

Indocyanine green and its nanosynthetic particles for the diagnosis and treatment of hepatocellular carcinoma

Indocyanine green (ICG) is an amphiphilic dye, which has been used as a diagnostic agent for decades. It is becoming increasingly utilized for the diagnosis and treatment of several diseases. Primary liver cancer is a common malignancy, particularly in China. We review the published literature describing how ICG plays increasingly important roles in the diagnosis, surgical planning and treatment of hepatocellular carcinoma.

Integration of Computational and Experimental Approaches to Elucidate Mechanisms of First-Pass Lymphatic Drug Sequestration and Long-Acting Pharmacokinetics of the Injectable Triple-HIV Drug Combination TLC-ART 101

TLC-ART101 is a long-acting triple-HIV drug combination of lopinavir-ritonavir-tenofovir in one nanosuspension intended for subcutaneous injection. After a single TLC-ART 101 administration in nonhuman primates, drug concentrations in both plasma and HIV-target lymph node mononuclear cells were sustained for 2 weeks. Nevertheless, the mechanisms leading to the targeted long-acting pharmacokinetics remain elusive. Therefore, an intravenous study of TLC-ART 101 in nonhuman primates was conducted to elucidate the degree of association of drugs in vivo, estimate subcutaneous bioavailability, and refine a mechanism-based pharmacokinetic (MBPK2) model. The MBPK2 model considers TLC-ART 101 systemic drug clearances, nanoparticle-associated/dissociated species, more detailed mechanisms of lymphatic first-pass retention of associated-drugs after subcutaneous administrations, and the prediction of drug concentration time-courses in lymph node mononuclear cells. For all 3 drugs, we found a high association with the nanoparticles in plasma (>87% lopinavir-ritonavir, 97% tenofovir), and an incomplete subcutaneous bioavailability (<29% lopinavir-ritonavir, 85% tenofovir). As hypothesized by the MBPK2 model, the incomplete SC bioavailability observed is due to sequestration into a lymphatic node depot after subcutaneous absorption (unlike most intramuscular nanodrug products having near-to-injection depots), which contributes to long-acting profiles detected in plasma and target cells. This combined experimental and modeling approach may be applicable for the clinical development of other long-acting drug-combination injectables.

The Potential of Long-Acting, Tissue-Targeted Synthetic Nanotherapy for Delivery of Antiviral Therapy Against HIV Infection

Oral administration of a combination of two or three antiretroviral drugs (cART) has transformed HIV from a life-threatening disease to a manageable infection. However, as the discontinuation of therapy leads to virus rebound in plasma within weeks, it is evident that, despite daily pill intake, the treatment is unable to clear the infection from the body. Furthermore, as cART drugs exhibit a much lower concentration in key HIV residual tissues, such as the brain and lymph nodes, there is a rationale for the development of drugs with enhanced tissue penetration. In addition, the treatment, with combinations of multiple different antiviral drugs that display different pharmacokinetic profiles, requires a strict dosing regimen to avoid the emergence of drug-resistant viral strains. An intriguing opportunity lies within the development of long-acting, synthetic scaffolds for delivering cART. These scaffolds can be designed with the goal to reduce the frequency of dosing and furthermore, hold the possibility of potential targeting to key HIV residual sites. Moreover, the synthesis of combinations of therapy as one molecule could unify the pharmacokinetic profiles of different antiviral drugs, thereby eliminating the consequences of sub-therapeutic concentrations. This review discusses the recent progress in the development of long-acting and tissue-targeted therapies against HIV for the delivery of direct antivirals, and examines how such developments fit in the context of exploring HIV cure strategies.

Novel drug combination nanoparticles exhibit enhanced plasma exposure and dose-responsive effects on eliminating breast cancer lung metastasis

Early diagnosis along with new drugs targeted to cancer receptors and immunocheckpoints have improved breast cancer survival. However, full remission remains elusive for metastatic breast cancer due to dose-limiting toxicities of heavily used, highly potent drug combinations such as gemcitabine and paclitaxel. Therefore, novel strategies that lower the effective dose and improve safety margins could enhance the effect of these drug combinations. To this end, we developed and evaluated a novel drug combination of gemcitabine and paclitaxel (GT). Leveraging a simple and scalable drug-combination nanoparticle platform (DcNP), we successfully prepared an injectable GT combination in DcNP (GT DcNP). Compared to a Cremophor EL/ethanol assisted drug suspension in buffer (CrEL), GT DcNP exhibits about 56-fold and 8.6-fold increases in plasma drug exposure (area under the curve, AUC) and apparent half-life of gemcitabine respectively, and a 2.9-fold increase of AUC for paclitaxel. Using 4T1 as a syngeneic model for breast cancer metastasis, we found that a single GT (20/2 mg/kg) dose in DcNP nearly eliminated colonization in the lungs. This effect was not achievable by a CrEL drug combination at a 5-fold higher dose (i.e., 100/10 mg/kg GT). A dose-response study indicates that GT DcNP provided a therapeutic index of ~15.8. Collectively, these data suggest that GT DcNP could be effective against advancing metastatic breast cancer with a margin of safety. As the DcNP formulation is intentionally designed to be simple, scalable, and long-acting, it may be suitable for clinical development to find effective treatment against metastatic breast cancer.

Extended cell and plasma drug levels after one dose of a three-in-one nanosuspension containing lopinavir, efavirenz, and tenofovir in nonhuman primates

OBJECTIVE

To characterize a drug-combination nanoparticle (DcNP) containing water-insoluble lopinavir (LPV) and efavirenz (EFV), and water-soluble tenofovir (TFV), for its potential as a long-acting combination HIV treatment.

DESIGN

Three HIV drugs (LPV, EFV, TFV) with well established efficacy and safety were coformulated into a single DcNP suspension. Two macaques were administered one subcutaneous injection and drug concentrations in plasma and mononuclear cells (in peripheral blood and lymph nodes) were analyzed over 2 weeks. Pharmacokinetic parameters and cell-to-plasma relationships of LPV, EFV, and TFV were determined.

RESULTS

This three-in-one nanoformulation provided extended concentrations of all drugs in lymph node cells that were 57- to 228-fold higher than those in plasma. Levels of all three drugs in peripheral blood mononuclear cells persisted for 2 weeks at levels equal to or higher than those in plasma.

CONCLUSION

With long-acting characteristics and higher drug penetration/persistence in cells, this three-in-one DcNP may enhance therapeutic efficacy of these well studied HIV drugs due to colocalization and targeting of this three-drug combination to HIV host cells.

Recent developments of nanotherapeutics for targeted and long-acting, combination HIV chemotherapy

Combination antiretroviral therapy (cART) given orally has transformed HIV from a terminal illness to a manageable chronic disease. Yet despite the recent development of newer and more potent drugs for cART and suppression of virus in blood to undetectable levels, residual virus remains in tissues. Upon stopping cART, virus rebounds and progresses to AIDS. Current oral cART regimens have several drawbacks including (1) challenges in patient adherence due to pill fatigue or side-effects, (2) the requirement of life-long daily drug intake, and (3) limited penetration and retention in cells within lymph nodes. Appropriately designed injectable nano-drug combinations that are long-acting and retained in HIV susceptible cells within lymph nodes may address these challenges. While a number of nanomaterials have been investigated for delivery of HIV drugs and drug combinations, key challenges involve developing and scaling delivery systems that provide a drug combination targeted to HIV host cells and tissues where residual virus persists. With validation of the drug-insufficiency hypothesis in lymph nodes, progress has been made in the development of drug combination nanoparticles that are long-acting and targeted to lymph nodes and cells. Unique drug combination nanoparticles (DcNPs) composed of three HIV drugs-lopinavir, ritonavir, and tenofovir-have been shown to provide enhanced drug levels in lymph nodes; and elevated drug-combination levels in HIV-host cells in the blood and plasma for two weeks. This review summarizes the progress in the development of nanoparticle-based drug delivery systems for HIV therapy. It discusses how injectable nanocarriers may be designed to enable delivery of drug combinations that are long-lasting and target-selective in physiological contexts (in vivo) to provide safe and effective use. Consistent drug combination exposure in the sites of residual HIV in tissues and cells may overcome drug insufficiency observed in patients on oral cART.

Long-Acting Profile of 4 Drugs in 1 Anti-HIV Nanosuspension in Nonhuman Primates for 5 Weeks After a Single Subcutaneous Injection

Daily oral antiretroviral therapy regimens produce limited drug exposure in tissues where residual HIV persists and suffer from poor patient adherence and disparate drug kinetics, which all negatively impact outcomes. To address this, we developed a tissue- and cell-targeted long-acting 4-in-1 nanosuspension composed of lopinavir (LPV), ritonavir, tenofovir (TFV), and lamivudine (3TC). In 4 macaques dosed subcutaneously, drug levels over 5 weeks in plasma, lymph node mononuclear cells (LNMCs), and peripheral blood mononuclear cells (PBMCs) were analyzed by liquid chromatography-tandem mass spectrometry. Plasma and PBMC levels of the active drugs (LPV, TFV, and 3TC) were sustained for 5 weeks; PBMC exposures to LPV, ritonavir, and 3TC were 12-, 16-, 42-fold higher than those in plasma. Apparent T_1/2z of LPV, TFV, and 3TC were 219.1, 63.1, and 136.3 h in plasma; 1045.7, 105.9, and 127.7 h in PBMCs. At day 8, LPV, TFV, and 3TC levels in LNMCs were 4.1-, 5.0-, and 1.9-fold higher than in those in PBMCs and much higher than in plasma. Therefore, 1 dose of a 4-drug nanosuspension exhibited persistent drug levels in LNMCs, PBMCs, and plasma for 5 weeks. With interspecies scaling and dose adjustment, this 4-in-1 HIV drug-combination could be a long-acting treatment with the potential to target residual virus in tissues and improve patient adherence.