Clot-targeted micellar formulation improves anticoagulation efficacy of bivalirudin

Brain targeted polymeric micelles as drug carriers for ischaemic stroke treatment

Ischaemic stroke is a central nervous system disease with high morbidity, recurrence and mortality rates. Thrombolytic and neuroprotective therapies are the main therapeutic strategies for ischaemic stroke, however, the poor delivery efficiency of thrombolytic and neuroprotective drugs to the brain limits their clinical application. So far, the development of nanomedicine has brought opportunities for the above challenges, which can not only realise the effective accumulation of drugs in the target site, but also improve the pharmacokinetic behaviour of the drugs. Among the most rapidly developing nanoparticles, micelles gradually emerging as an effective strategy for ischaemic stroke treatment due to their own unique advantages. This review provided an overview of targeted and response-release micelles based on the physicochemical properties of the ischaemic stroke microenvironment, summarised the targeting strategies for delivering micellar formulations to the thrombus, blood-brain barrier, and brain parenchyma, and finally described the potentials and challenges of polymeric micelles in the treatment of ischaemic stroke.

Carboxyl PEGylation of magnetic nanoparticles as antithrombotic and thrombolytic agents by calcium binding

Known to be biocompatible and hemocompatible, polyethylene glycol (PEG) has been widely used as anti-fouling coating of biomaterials. Nanoparticles coated with functionalized PEG were also investigated for their nano-cell interactions, but seldomly on the coagulation system, especially with platelets. Both experiments and molecular dynamic simulations indicate that terminal carboxylation of PEG promotes its binding with calcium, especially in the ionized form, which makes it potential anticoagulants. Further, the carboxyl PEGylated magnetic nanoparticle (HOOC-PEG₂₀₀₀-MNP) exhibits significantly increased anticoagulant and antiplatelet properties, by entering the open canalicular system (OCS) of human platelets and binding with the cytoplasmic calcium ions. HOOC-PEG₂₀₀₀-MNP also acts as effective thrombolytic agents in dissolving mature blood clots under oscillating magnetic field both in vitro and in vivo. Therefore, the carboxyl PEGylated magnetic nanoparticles are prototype agents for antithrombotic and thrombolytic therapies and provide a versatile platform for targeted and effective treatments of acute cardiovascular diseases.

Current Strategies for Microbubble-Based Thrombus Targeting: Activation-Specific Epitopes and Small Molecular Ligands

Microbubbles with enhanced ultrasound represent a potentially potent evolution to the administration of a free drug in the treatment of thrombotic diseases. Conformational and expressional changes of several thrombotic biological components during active coagulation provide epitopes that allow site-specific delivery of microbubble-based agents to the thrombus for theranostic purpose. Through the interaction with these epitopes, emerging high-affinity small molecular ligands are able to selectively target the thrombi with tremendous advantages over traditional antibody-based strategy. In this mini-review, we summarize recent novel strategies for microbubble-based targeting of thrombus through epitopes located at activated platelets and fibrin. We also discuss the challenges of current targeting modalities and supramolecular carrier systems for their translational use in thrombotic pathologies.

Mechanisms of thrombosis and research progress on targeted antithrombotic drugs

Globally, the incidence of thromboembolic diseases has increased in recent years, accompanied by an increase in patient mortality. Currently, several targeting delivery strategies have been developed to treat thromboembolic diseases. In this review, we discuss the mechanisms of thrombolysis and current anticoagulant drugs, particularly those with targeting capability, highlighting advances in the accurate treatment of thrombolysis with fewer adverse effects. Such approaches include magnetic drug-loading systems combined with molecular imaging to recanalize blood vessels and systems based on chimeric Arg-Gly-Asp (RGD) sequences that can target platelet glycoprotein receptor. With such progress in targeted antithrombotic drugs, targeted thrombolysis treatment shows significant potential benefit for patients.

Aggregation propensity of therapeutic fibrin-homing pentapeptides: insights from experiments and molecular dynamics simulations

CREKA (Cys-Arg-Glu-Lys-Ala) and its engineered analogue CRMeEKA, in which Glu has been replaced by N-methyl-Glu to provide resistance against proteolysis, are emerging pentapeptides that were specifically designed to bind fibrin-fibronectin complexes accumulated in the walls of tumour vessels. However, many of the intrinsic properties of CREKA and CRMeEKA, which are probably responsible for their different behaviour when combined with other materials (such as polymers) for diagnosis and therapeutics, remain unknown yet. The intrinsic tendency of these pentapeptides to form aggregates has been analysed by combining experimental techniques and atomistic Molecular Dynamics (MD) simulations. Dynamic light scattering assays show the formation of nanoaggregates that increase in size with the peptide concentration, even though aggregation occurs sooner for CRMeEKA, independently of the peptide concentration. FTIR and circular dichroism spectroscopy studies suggest that aggregated pentapeptides do not adopt any secondary structure. Atomistic MD trajectories show that CREKA aggregates faster and forms bigger molecular clusters than CRMeEKA. This behaviour has been explained by stability of the conformations adopted by un-associated peptide strands. While CREKA molecules organize by forming intramolecular backbone - side chain hydrogen bonds, CRMeEKA peptides display main chain - main chain hydrogen bonds closing very stable γ- or β-turns. Besides, energetic analyses reveal that CRMeEKA strands are better solvated in water than CREKA ones, independent of whether they are assembled or un-associated.

Nano-Medicine for Thrombosis: A Precise Diagnosis and Treatment Strategy

Thrombosis is a global health issue and one of the leading factors of death. However, its diagnosis has been limited to the late stages, and its therapeutic window is too narrow to provide reasonable and effective treatment. In addition, clinical thrombolytics suffer from a short half-life, allergic reactions, inactivation, and unwanted tissue hemorrhage. Nano-medicines have gained extensive attention in diagnosis, drug delivery, and photo/sound/magnetic-theranostics due to their convertible properties. Furthermore, diagnosis and treatment of thrombosis using nano-medicines have also been widely studied. This review summarizes the recent advances in this area, which revealed six types of nanoparticle approaches: (1) in vitro diagnostic kits using "synthetic biomarkers"; (2) in vivo imaging using nano-contrast agents; (3) targeted drug delivery systems using artificial nanoparticles; (4) microenvironment responsive drug delivery systems; (5) drug delivery systems using biological nanostructures; and (6) treatments with external irradiation. The investigations of nano-medicines are believed to be of great significance, and some of the advanced drug delivery systems show potential applications in clinical theranotics.

Ligand-Installed Nanocarriers toward Precision Therapy

Development of drug-delivery systems that selectively target neoplastic cells has been a major goal of nanomedicine. One major strategy for achieving this milestone is to install ligands on the surface of nanocarriers to enhance delivery to target tissues, as well as to enhance internalization of nanocarriers by target cells, which improves accuracy, efficacy, and ultimately enhances patient outcomes. Herein, recent advances regarding the development of ligand-installed nanocarriers are introduced and the effect of their design on biological performance is discussed. Besides academic achievements, progress on ligand-installed nanocarriers in clinical trials is presented, along with the challenges faced by these formulations. Lastly, the future perspectives of ligand-installed nanocarriers are discussed, with particular emphasis on their potential for emerging precision therapies.

Tumor-Penetrating Nanosystem Strongly Suppresses Breast Tumor Growth

Antiangiogenic and vascular disrupting compounds have shown promise in cancer therapy, but tend to be only partially effective. We previously reported a potent theranostic nanosystem that was highly effective in glioblastoma and breast cancer mouse models, retarding tumor growth and producing some cures [ Agemy , L. et al. Proc. Natl. Acad. Sci. U.S.A. 2011 , 108 , 17450 - 17455 . Agemy , L. et al. Mol. Ther. 2013 , 21 , 2195 - 2204 .]. The nanosystem consists of iron oxide NPs ("nanoworms") coated with a composite peptide with tumor-homing and pro-apoptotic domains. The homing component targets tumor vessels by binding to p32/gC1qR at the surface or tumor endothelial cells. We sought to further improve the efficacy nanosystem by searching for an optimally effective homing peptide that would also incorporate a tumor-penetrating function. To this effect, we tested a panel of candidate p32 binding peptides with a sequence motif that conveys tumor-penetrating activity (CendR motif). We identified a peptide designated as Linear TT1 (Lin TT1) (sequence: AKRGARSTA) as most effective in causing tumor homing and penetration of the nanosystem. This peptide had the lowest affinity for p32 among the peptides tested. The low affinity may have moderated the avidity effect from the multivalent presentation on nanoparticles (NPs), such that the NPs avoid getting trapped by the so-called "binding-site barrier", which can hinder tissue penetration of compounds with a high affinity for their receptors. Treatment of breast cancer mice with the LinTT1 nanosystem showed greatly improved efficacy compared to the original system. These results identify a promising treatment modality and underscore the value of tumor penetration effect in improving the efficacy tumor treatment.

Engineered Nanoplatelets for Enhanced Treatment of Multiple Myeloma and Thrombus

A platelet-membrane-coated biomimetic nanocarrier, which can sequentially target the bone microenvironment and myeloma cells to enhance the drug availability at the myeloma site and decrease off-target effects, is developed for inhibiting multiple myeloma growth and simultaneously eradicating thrombus complication.

Tumor-Targeted Multimodal Optical Imaging with Versatile Cadmium-Free Quantum Dots

The rapid development of fluorescence imaging technologies requires concurrent improvements in the performance of fluorescent probes. Quantum dots have been extensively used as an imaging probe in various research areas because of their inherent advantages based on unique optical and electronic properties. However, their clinical translation has been limited by the potential toxicity especially from cadmium. Here, a versatile bioimaging probe is developed by using highly luminescent cadmium-free CuInSe2/ZnS core/shell quantum dots conjugated with CGKRK (Cys-Gly-Lys-Arg-Lys) tumor-targeting peptides. This probe exhibits excellent photostability, reasonably long circulation time, minimal toxicity, and strong tumor-specific homing property. The most important feature of this probe is that it shows distinctive versatility in tumor-targeted multimodal imaging including near-infrared, time-gated, and two-photon imaging in different tumor models. In a glioblastoma mouse model, the targeted probe clearly denotes tumor boundaries and positively labels a population of diffusely infiltrating tumor cells, suggesting its utility in precise tumor detection during surgery. This work lays a foundation for potential clinical translation of the probe.