Mechanism of Collaborative Enhancement of Binding of Paired Antibodies to Distinct Epitopes of Platelet Endothelial Cell Adhesion Molecule-1

Novel Multifunctional Meta-Surface Plasmon Resonance Chip Microplate for High-Throughput Molecular Screening

The utilization of surface plasmon resonance (SPR) sensors for real-time label-free molecular interaction analysis is already being employed in the fields of in vitro diagnostics and biomedicine. However, the widespread application of SPR technology is hindered by its limited detection throughput and high cost. To address this issue, this study introduces a novel multifunctional MetaSPR high-throughput microplate biosensor featuring 3D nanocups array structure, aiming to achieve high-throughput screening with a reduced cost and enhanced speed. Different types of MetaSPR sensors and analytical detection methods have been developed for accurate antibody subtype identification, epitope binding, affinity determination, antibody collocation, and quantitative detection， greatly promoting the screening and analysis of early-stage antibody drugs. The MetaSPR platform combined with nano-enhanced particles amplifies the detection signal and improves the detection sensitivity, making it more convenient, sensitive, and efficient than traditional ELISA. The findings demonstrate that the MetaSPR biosensor is a new practical technology detection platform that can improve the efficiency of biomolecular interaction studies with unlimited potential for new drug development.

Precise nanodrug delivery systems with cell-specific targeting for ALI/ARDS treatment

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common acute and critical diseases in clinics and have no effective treatment to date. With the concept of "precision medicine", research into the precise drug delivery of therapeutic and diagnostic drugs has become a frontier in nanomedicine research and has entered the era of design of precise nanodrug delivery systems (NDDSs) with cell-specific targeting. Owing to the distinctive characteristics of ALI/ARDS, designing NDDSs for specific focal sites is an important strategy for changing drug distribution in the body and specifically increasing drug concentration at target sites while decreasing drug concentration at non-target sites. This strategy enhances drug efficacy, reduces adverse reactions, and ensures accurate nano-targeted treatment. On the basis of the characteristics of pathological ALI/ARDS microenvironments, this paper reviews NDDSs targeting vascular endothelial cells, neutrophils, alveolar macrophages, and alveolar epithelial cells to provide reference for designing accurate NDDSs for ALI/ARDS and novel insights into targeted treatments for ALI/ARDS.

Reactive Oxygen Species Scavenging Nanomedicine for the Treatment of Ischemic Heart Disease

Ischemic heart disease (IHD) is the leading cause of disability and mortality worldwide. Reactive oxygen species (ROS) have been shown to play key roles in the progression of diabetes, hypertension, and hypercholesterolemia, which are independent risk factors that lead to atherosclerosis and the development of IHD. Engineered biomaterial-based nanomedicines are under extensive investigation and exploration, serving as smart and multifunctional nanocarriers for synergistic therapeutic effect. Capitalizing on cell/molecule-targeting drug delivery, nanomedicines present enhanced specificity and safety with favorable pharmacokinetics and pharmacodynamics. Herein, the roles of ROS in both IHD and its risk factors are discussed, highlighting cardiovascular medications that have antioxidant properties, and summarizing the advantages, properties, and recent achievements of nanomedicines that have ROS scavenging capacity for the treatment of diabetes, hypertension, hypercholesterolemia, atherosclerosis, ischemia/reperfusion, and myocardial infarction. Finally, the current challenges of nanomedicines for ROS-scavenging treatment of IHD and possible future directions are discussed from a clinical perspective.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

Expanding the arsenal against pulmonary diseases using surface-functionalized polymeric micelles: breakthroughs and bottlenecks

Pulmonary diseases such as lung cancer, asthma and tuberculosis have remained one of the common challenges globally. Polymeric micelles (PMs) have emerged as an effective technique for achieving targeted drug delivery for a local as well as a systemic effect. These PMs encapsulate and protect hydrophobic drugs, increase pulmonary targeting, decrease side effects and enhance drug efficacy through the inhalation route. In the current review, emphasis has been placed on the different barriers encountered by the drugs given via the pulmonary route and the mechanism of PMs in achieving drug targeting. The applications of PMs in different pulmonary diseases have also been discussed in detail.

Dual Affinity to RBCs and Target Cells (DART) Enhances Both Organ- and Cell Type-Targeting of Intravascular Nanocarriers

A long-standing goal of nanomedicine is to improve a drug's benefit by loading it into a nanocarrier that homes solely to a specific target cell and organ. Unfortunately, nanocarriers usually end up with only a small percentage of the injected dose (% ID) in the target organ, due largely to clearance by the liver and spleen. Further, cell-type-specific targeting is rarely achieved without reducing target organ accumulation. To solve these problems, we introduce DART (dual affinity to RBCs and target cells), in which nanocarriers are conjugated to two affinity ligands, one binding red blood cells and one binding a target cell (here, pulmonary endothelial cells). DART nanocarriers first bind red blood cells and then transfer to the target organ's endothelial cells as the bound red blood cells squeeze through capillaries. We show that within minutes after intravascular injection in mice nearly 70% ID of DART nanocarriers accumulate in the target organ (lungs), more than doubling the % ID ceiling achieved by a multitude of prior technologies, finally achieving a majority % ID in a target organ. Humanized DART nanocarriers in ex vivo perfused human lungs recapitulate this phenomenon. Furthermore, DART enhances the selectivity of delivery to target endothelial cells over local phagocytes within the target organ by 6-fold. DART's marked improvement in both organ- and cell-type targeting may thus be helpful in localizing drugs for a multitude of medical applications.

Bivalent engagement of endothelial surface antigens is critical to prolonged surface targeting and protein delivery in vivo

Targeted drug delivery to the endothelium has the potential to generate localized therapeutic effects at the blood-tissue interface. For some therapeutic cargoes, it is essential to maintain contact with the bloodstream to exert protective effects. The pharmacokinetics (PK) of endothelial surface-targeted affinity ligands and biotherapeutic cargo remain a largely unexplored area, despite obvious translational implications for this strategy. To bridge this gap, we site-specifically radiolabeled mono- (scFv) and bivalent (mAb) affinity ligands specific for the endothelial cell adhesion molecules, PECAM-1 (CD31) and ICAM-1 (CD54). Radiotracing revealed similar lung biodistribution at 30 minutes post-injection (79.3% ± 4.2% vs 80.4% ± 10.6% ID/g for αICAM and 58.9% ± 3.6% ID/g vs. 47.7% ± 5.8% ID/g for αPECAM mAb vs. scFv), but marked differences in organ residence time, with antibodies demonstrating an order of magnitude greater area under the lung concentration vs. time curve (AUC_inf 1698 ± 352 vs. 53.3 ± 7.9 ID/g*hrs for αICAM and 1023 ± 507 vs. 114 ± 37 ID/g*hrs for αPECAM mAb vs scFv). A physiologically based pharmacokinetic model, fit to and validated using these data, indicated contributions from both superior binding characteristics and prolonged circulation time supporting multiple binding-detachment cycles. We tested the ability of each affinity ligand to deliver a prototypical surface cargo, thrombomodulin (TM), using one-to-one protein conjugates. Bivalent mAb-TM was superior to monovalent scFv-TM in both pulmonary targeting and lung residence time (AUC_inf 141 ± 3.2 vs 12.4 ± 4.2 ID/g*hrs for ICAM and 188 ± 90 vs 34.7 ± 19.9 ID/g*hrs for PECAM), despite having similar blood PK, indicating that binding strength is more important parameter than the kinetics of binding. To maximize bivalent target engagement, we synthesized an oriented, end-to-end anti-ICAM mAb-TM conjugate and found that this therapeutic had the best lung residence time (AUC_inf 253 ± 18 ID/g*hrs) of all TM modalities. These observations have implications not only for the delivery of TM, but also potentially all therapeutics targeted to the endothelial surface.

Targeting drug delivery in the vascular system: Focus on endothelium

The bloodstream is the main transporting pathway for drug delivery systems (DDS) from the site of administration to the intended site of action. In many cases, components of the vascular system represent therapeutic targets. Endothelial cells, which line the luminal surface of the vasculature, play a tripartite role of the key target, barrier, or victim of nanomedicines in the bloodstream. Circulating DDS may accumulate in the vascular areas of interest and in off-target areas via mechanisms bypassing specific molecular recognition, but using ligands of specific vascular determinant molecules enables a degree of precision, efficacy, and specificity of delivery unattainable by non-affinity DDS. Three decades of research efforts have focused on specific vascular targeting, which have yielded a multitude of DDS, many of which are currently undergoing a translational phase of development for biomedical applications, including interventions in the cardiovascular, pulmonary, and central nervous systems, regulation of endothelial functions, host defense, and permeation of vascular barriers. We discuss the design of endothelial-targeted nanocarriers, factors underlying their interactions with cells and tissues, and describe examples of their investigational use in models of acute vascular inflammation with an eye on translational challenges.

Targeting therapeutics to endothelium: are we there yet?

Vascular endothelial cells represent an important therapeutic target in many pathologies, including inflammation, oxidative stress, and thrombosis; however, delivery of drugs to this site is often limited by the lack of specific affinity of therapeutics for these cells. Selective delivery of both small molecule drugs and therapeutic proteins to the endothelium has been achieved through the use of targeting ligands, such as monoclonal antibodies, directed against endothelial cell surface markers, particularly cell adhesion molecules (CAMs). Careful selection of target molecules and targeting agents allows for precise delivery to sites of inflammation, thereby maximizing therapeutic drug concentrations at the site of injury. A good understanding of the physiological and pathological determinants of drug and drug carrier pharmacokinetics and biodistribution may allow for a priori identification of optimal properties of drug carrier and targeting agent. Targeted delivery of therapeutics such as antioxidants and antithrombotic agents to the injured endothelium has shown efficacy in preclinical models, suggesting the potential for translation into clinical practice. As with all therapeutics, demonstration of both efficacy and safety are required for successful clinical implementation, which must be considered not only for the individual components (drug, targeting agent, etc.) but also for the sum of the parts (e.g., the drug delivery system), as unexpected toxicities may arise with complex delivery systems. While the use of endothelial targeting has not been translated into the clinic to date, the preclinical results summarized here suggest that there is hope for successful implementation of these agents in the years to come.

Vascular Targeting of Radiolabeled Liposomes with Bio-Orthogonally Conjugated Ligands: Single Chain Fragments Provide Higher Specificity than Antibodies

Liposomes are a proven, versatile, and clinically viable technology platform for vascular delivery of drugs and imaging probes. Although targeted liposomes have the potential to advance these applications, complex formulations and the need for optimal affinity ligands and conjugation strategies challenge their translation. Herein, we employed copper-free click chemistry functionalized liposomes to target platelet-endothelial cell adhesion molecule (PECAM-1) and intracellular adhesion molecule (ICAM-1) by conjugating clickable monoclonal antibodies (Ab) or their single chain variable fragments (scFv). For direct, quantitative tracing, liposomes were surface chelated with ¹¹¹In to a >90% radiochemical yield and purity. Particle size and distribution, stability, ligand surface density, and specific binding to target cells were characterized in vitro. Biodistribution of liposomes after IV injection was characterized in mice using isotope detection in organs and by noninvasive imaging (single-photon emission computed tomography/computed tomography, SPECT/CT). As much as 20-25% of injected dose of liposomes carrying PECAM and ICAM ligands, but not control IgG accumulated in the pulmonary vasculature. The immunospecificity of pulmonary targeting of scFv/liposomes to PECAM-1 and ICAM-1, respectively, was 10-fold and 2.5-fold higher than of Ab/liposomes. Therefore, the combination of optimal ligands, benign conjugation, and labeling yields liposomal formulations that may be used for highly effective and specific vascular targeting.

Vascular endothelial effects of collaborative binding to platelet/endothelial cell adhesion molecule-1 (PECAM-1)

Targeting drugs to endothelial cells has shown the ability to improve outcomes in animal models of inflammatory, ischemic and thrombotic diseases. Previous studies have revealed that certain pairs of ligands (antibodies and antibody fragments) specific for adjacent, but distinct, epitopes on PECAM-1 enhance each other’s binding, a phenomenon dubbed Collaborative Enhancement of Paired Affinity Ligands, or CEPAL. This discovery has been leveraged to enable simultaneous delivery of multiple therapeutics to the vascular endothelium. Given the known role of PECAM-1 in promoting endothelial quiescence and cell junction integrity, we sought here to determine if CEPAL might induce unintended vascular effects. Using a combination of in vitro and in vivo techniques and employing human and mouse endothelial cells under physiologic and pathologic conditions, we found only modest or non-significant effects in response to antibodies to PECAM-1, whether given solo or in pairs. In contrast, these methods detected significant elevation of endothelial permeability, pro-inflammatory vascular activation, and systemic cytokine release following antibody binding to the related endothelial junction protein, VE-Cadherin. These studies support the notion that PECAM-1-targeted CEPAL provides relatively well-tolerated endothelial drug delivery. Additionally, the analysis herein creates a template to evaluate potential toxicities of vascular-targeted nanoparticles and protein therapeutics.