Annexin V-Conjugated Mixed Micelles as a Potential Drug Delivery System for Targeted Thrombolysis

REVIEW: "ISCHEMIC STROKE: From Fibrinolysis to Functional Recovery" Nanomedicine: emerging approaches to treat ischemic stroke

Stroke is responsible for 11% of all deaths worldwide, the majority of which are caused by ischemic strokes, thus making the need to urgently find safe and effective therapies. Today, these can be cured either by mechanical thrombectomy when the thrombus is accessible, or by intravenous injection of fibrinolytics. However, the latter present several limitations, such as potential severe side effects, few eligible patients and low rate of partial and full recovery. To design safer and more effective treatments, nanomedicine appeared in this medical field a few decades ago. This review will explain why nanoparticle-based therapies and imaging techniques are relevant for ischemic stroke management. Then, it will present the different nanoparticle types that have been recently developed to treat this pathology. It will also study the various targeting strategies used to bring nanoparticles to the stroke site, thereby limiting side effects and improving the therapeutic efficacy. Finally, this review will present the few clinical studies testing nanomedicine on stroke and discuss potential causes for their scarcity.

Untethered Microgrippers for Precision Medicine

Microgrippers, a branch of micro/nanorobots, refer to motile miniaturized machines that are of a size in the range of several to hundreds of micrometers. Compared with tethered grippers or other microscopic diagnostic and surgical equipment, untethered microgrippers play an indispensable role in biomedical applications because of their characteristics such as miniaturized size, dexterous shape tranformation, and  controllable motion, which enables the microgrippers to enter hard-to-reach regions to execute specific medical tasks for disease diagnosis and treatment. To date, numerous medical microgrippers are developed, and their potential in cell manipulation, targeted drug delivery, biopsy, and minimally invasive surgery  are explored. To achieve controlled locomotion and efficient target-oriented actions, the materials, size, microarchitecture, and morphology of microgrippers shall be deliberately designed. In this review, the authors summarizes the latest progress in untethered micrometer-scale grippers. The working mechanisms of shape-morphing and actuation methods for effective movement are first introduced. Then, the design principle and state-of-the-art fabrication techniques of microgrippers are discussed. Finally, their applications in the precise medicine are highlighted, followed by offering future perspectives for the development of untethered medical microgrippers.

The Relevance, Predictability, and Utility of Annexin A5 for Human Physiopathology

As an important functional protein molecule in the human body, human annexin A5 (hAnxA5) is widely found in human cells and body fluids. hAnxA5, the smallest type of annexin, performs a variety of biological functions by reversibly and specifically binding phosphatidylserine (PS) in a calcium-dependent manner and plays an important role in many human physiological and pathological processes. The free state hAnxA5 exists in the form of monomers and usually forms a polymer in a specific self-assembly manner when exerting biological activity. This review systematically discusses the current knowledge and understanding of hAnxA5 from three perspectives: physiopathological relevance, diagnostic value, and therapeutic utility. hAnxA5 affects the occurrence and development of many physiopathological processes. Moreover, hAnxA5 can be used independently or in combination as a biomarker of physiopathological phenomena for the diagnosis of certain diseases. Importantly, based on the properties of hAnxA5, many novel drug candidates have been designed and prepared for application in actual medical practice. However, there are also some gaps and shortcomings in hAnxA5 research. This in-depth study will not only expand the understanding of structural and functional relationships but also promote the application of hAnxA5 in the field of biomedicine.

Nattokinase Encapsulated Nanomedicine for Targeted Thrombolysis: Development, Improved in Vivo Thrombolytic Effects, and Ultrasound/Photoacoustic Imaging

Nattokinase (NK), a potent thrombolytic enzyme that dissolves blood clots, is highly used in the treatment of cardiovascular disorders. However, its effective delivery remains demanding because of stability and bioavailability problems owing to its high molecular weight and proteineous nature. In this research, we have developed novel NK-loaded nontargeted liposomes (NK-LS) and targeted liposomes (RGD-NK-LS and AM-NK-LS) by the reverse phase evaporation method. The physiochemical characterizations (particle size, polydispersity index, zeta potential, and morphology) were performed by a Zetasizer, SEM, TEM, and AFM. The Bradford assay and XPS analysis confirmed the successful surface conjugation of the targeting ligands. Platelet interaction studies by CLSM, photon imager optima, and flow cytometry showed significantly higher (P < 0.05) platelet binding affinity of targeted liposomes. In vitro evaluations were performed using human blood and a fibrinolysis study by CLSM imaging demonstrating the potent antithrombotic efficacy of AM-NK-LS. Furthermore, bleeding and clotting time studies revealed that the targeted liposomes were free from any bleeding complications. Moreover, the in vivo FeCl3 model on Sprague-Dawley (SD) rats using a Doppler flow meter and ultrasound/photoacoustic imaging indicated the increased % thrombolysis and potent affinity of targeted liposomes toward the thrombus site. Additionally, in vitro hemocompatibility and histopathology studies demonstrated the safety and biocompatibility of the nanoformulations.

Bacteriophage entrapped chitosan microgel for the treatment of biofilm-mediated polybacterial infection in burn wounds

Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria are most commonly present in burn wound infections. Multidrug resistance (MDR) and biofilm formation make it difficult to treat these infections. Bacteriophages (BPs) are proven as an effective therapy against MDR as well as biofilm-associated wound infections. In the present work, a naturally inspired bacteriophage cocktail loaded chitosan microparticles-laden topical gel has been developed for the effective treatment of these infections. Bacteriophages against MDR S. aureus (BPSAФ1) and P. aeruginosa (BPPAФ1) were isolated and loaded separately and in combination into the chitosan microparticles (BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs), which were later incorporated into the SEPINEO™ P 600 gel (BPSAФ1-CHMPs-gel, BPPAФ1-CHMPs-gel, and MBP-CHMPs-gel). BPs were characterized for their morphology, lytic activity, burst size, and hemocompatibility, and BPs belongs to Caudoviricetes class. Furthermore, BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs had an average particle size of 1.19 ± 0.11, 1.42 ± 0.21, and 2.84 ± 0.28 μm, respectively, and expressed promising in vitro antibiofilm eradication potency. The ultrasound and photoacoustic imaging in infected burn wounds demonstrated improved wound healing reduced inflammation and increased oxygen saturation following treatment with BPs formulations. The obtained results suggested that the incorporation of the BPs in the MP-gel protected the BPs, sustained the BPs release, and improved the antibacterial activity.

A Bacteriophage-Loaded Microparticle Laden Topical Gel for the Treatment of Multidrug-Resistant Biofilm-Mediated Burn Wound Infection

Klebsiella pneumoniae is regarded as one of the most profound bacteria isolated from the debilitating injuries caused by burn wounds. In addition, the multidrug resistance (MDR) and biofilm formation make treating burn patients with clinically available antibiotics difficult. Bacteriophage therapy has been proven an effective alternative against biofilm-mediated wound infections caused by MDR bacterial strains. In the current study, the bacteriophage (BPKPФ1) against MDR Klebsiella pneumoniae was isolated and loaded into the chitosan microparticles (CHMPs), which was later incorporated into the Sepineo P 600 to convert into a gel (BPKPФ1-CHMP-gel). BPKPФ1 was characterized for lytic profile, morphological class, and burst size, which revealed that the BPKPФ1 belongs to the family Siphoviridae. Moreover, BPKPФ1 exhibited a narrow host range with 128 PFU/host cell of burst size. The BPKPФ1-loaded CHMPs showed an average particle size of  1.96 ± 0.51 μm, zeta potential 32.16 ± 0.41 mV, and entrapment efficiency in the range of 82.44 ± 1.31%. Further, the in vitro antibacterial and antibiofilm effectiveness of BPKPФ1-CHMPs-gel were examined. The in vivo potential of the BPKPФ1-CHMPs-gel was assessed using a rat model with MDR Klebsiella pneumoniae infected burn wound, which exhibited improved wound contraction (89.22 ± 0.48%) in 28 days with reduced inflammation, in comparison with different controls. Data in hand suggest the potential of bacteriophage therapy to be developed as personalized therapy in case of difficult-to-treat bacterial infections.

Cargo-free particles divert neutrophil-platelet aggregates to reduce thromboinflammation

The combination of inflammation and thrombosis is a hallmark of many cardiovascular diseases. Under such conditions, platelets are recruited to an area of inflammation by forming platelet-leukocyte aggregates via interaction of PSGL-1 on leukocytes and P-selectin on activated platelets, which can bind to the endothelium. While particulate drug carriers have been utilized to passively redirect leukocytes from areas of inflammation, the downstream impact of these carriers on platelet accumulation in thromboinflammatory conditions has yet to be studied. Here, we explore the ability of polymeric particles to divert platelets away from inflamed blood vessels both in vitro and in vivo. We find that untargeted and targeted micron-sized polymeric particles can successfully reduce platelet adhesion to an inflamed endothelial monolayer in vitro in blood flow systems and in vivo in a lipopolysaccharide-induced, systemic inflammation murine model. Our data represent initial work in developing cargo-free, anti-platelet therapeutics specifically for conditions of thromboinflammation.

Application of Nanotechnology in Thrombus Therapy

A thrombus is a blood clot that forms in the lumen of an artery or vein, restricting blood flow and causing clinical symptoms. Thrombosis is associated with many life-threatening cardiovascular diseases. However, current clinical therapeutic technologies still have many problems in targeting, enrichment, penetration, and safety to meet the thrombosis treatment needs. Therefore, researchers devote themselves to developing nanosystems loaded with antithrombotic drugs to address this paradox in recent years. Herein, the existing thrombosis treatment technologies are first reviewed; and then, their advantages and disadvantages are outlined based on a brief discussion of thrombosis's definition and formation mechanism. Furthermore, the need and application cases for introducing nanotechnology are discussed, focusing on thrombus-specific targeted ligand modification technology and microenvironment-triggered responsive drug release technology. Then, nanomaterials that can be used to design antithrombotic nanotherapeutic systems are summarized. Moreover, a variety of drug delivery technologies driven by nanomotors in thrombosis therapy is also introduced. Last of all, a prospective discussion on the future development of nanotechnology for thrombosis therapy is highlighted.

GPIIb/IIIa Receptor Targeted Rutin Loaded Liposomes for Site-Specific Antithrombotic Effect

Rutin (RUT) is a flavonoid obtained from a natural source and is reported for antithrombotic potential, but its delivery remains challenging because of its poor solubility and bioavailability. In this research, we have fabricated novel rutin loaded liposomes (RUT-LIPO, nontargeted), liposomes conjugated with RGD peptide (RGD-RUT-LIPO, targeted), and abciximab (ABX-RUT-LIPO, targeted) by ethanol injection method. The particle size, ζ potential, and morphology of prepared liposomes were analyzed by using DLS, SEM, and TEM techniques. The conjugation of targeting moiety on the surface of targeted liposomes was confirmed by XPS analysis and Bradford assay. In vitro assessment such as blood clot assay, aPTT assay, PT assay, and platelet aggregation analysis was performed using human blood which showed the superior antithrombotic potential of ABX-RUT-LIPO and RGD-RUT-LIPO liposomes. The clot targeting efficiency was evaluated by in vitro imaging and confocal laser scanning microscopy. A significant (P < 0.05) rise in the affinity of targeted liposomes toward activated platelets was demonstrated that revealed their remarkable potential in inhibiting thrombus formation. Furthermore, an in vivo study executed on Sprague Dawley rats (FeCl₃ model) demonstrated improved antithrombotic activity of RGD-RUT-LIPO and ABX-RUT-LIPO compared with pure drug. The pharmacokinetic study performed on rats demonstrates the increase in bioavailability when administered as liposomal formulation as compared to RUT. Moreover, the tail bleeding assay and clotting time study (Swiss Albino mice) indicated a better antithrombotic efficacy of targeted liposomes than control preparations. Additionally, biocompatibility of liposomal formulations was determined by an in vitro hemolysis study and cytotoxicity assay, which showed that they were hemocompatible and safe for human use. A histopathology study on rats suggested no severe toxicity of prepared liposomal formulations. Thus, RUT encapsulated nontargeted and targeted liposomes exhibited superior antithrombotic potential over RUT and could be used as a promising carrier for future use.

Recent Advances in Nanomaterials for Diagnosis, Treatments, and Neurorestoration in Ischemic Stroke

Stroke is a major public health issue, corresponding to the second cause of mortality and the first cause of severe disability. Ischemic stroke is the most common type of stroke, accounting for 87% of all strokes, where early detection and clinical intervention are well known to decrease its morbidity and mortality. However, the diagnosis of ischemic stroke has been limited to the late stages, and its therapeutic window is too narrow to provide rational and effective treatment. In addition, clinical thrombolytics suffer from a short half-life, inactivation, allergic reactions, and non-specific tissue targeting. Another problem is the limited ability of current neuroprotective agents to promote recovery of the ischemic brain tissue after stroke, which contributes to the progressive and irreversible nature of ischemic stroke and also the severity of the outcome. Fortunately, because of biomaterials’ inherent biochemical and biophysical properties, including biocompatibility, biodegradability, renewability, nontoxicity, long blood circulation time, and targeting ability. Utilization of them has been pursued as an innovative and promising strategy to tackle these challenges. In this review, special emphasis will be placed on the recent advances in the study of nanomaterials for the diagnosis and therapy of ischemic stroke. Meanwhile, nanomaterials provide much promise for neural tissue salvage and regeneration in brain ischemia, which is also highlighted.

Engineered platelets-based drug delivery platform for targeted thrombolysis

Thrombolytic agents have thus far yielded limited therapeutic benefits in the treatment of thrombotic disease due to their short half-life, low targeting ability, and association with serious adverse reactions, such as bleeding complications. Inspired by the natural roles of platelets during thrombus formation, we fabricated a platelet-based delivery system (NO@uPA/PLTs) comprising urokinase (uPA) and arginine (Arg) for targeted thrombolysis and inhibition of re-embolism. The anchoring of uPA to the platelet surface by lipid insertion increased the thrombotic targeting and in vivo circulation duration of uPA without disturbing platelet functions. Nitric oxide (NO) generated by the loaded Arg inhibited platelet aggregation and activation at the damaged blood vessel, thereby inhibiting re-embolism. NO@uPA/PLTs effectively accumulated at the thrombi in pulmonary embolism and carotid artery thrombosis model mice and exerted superior thrombolytic efficacy. In addition, the platelet delivery system showed excellent thrombus recurrence prevention ability in a mouse model of secondary carotid artery injury. The coagulation indicators in vivo showed that the platelet-based uPA and NO co-delivery system possessed a low hemorrhagic risk, providing a promising tool for rapid thrombolysis and efficient inhibition of posttreatment re-embolism.

Ultrasound-Propelled Janus Rod-Shaped Micromotors for Site-Specific Sonodynamic Thrombolysis

Antithrombosis therapy is confronted with short half-lives of thrombolytic agents, limited therapeutic effects, and bleeding complications. Drug delivery systems of thrombolytic agents face challenges in effective penetration into thrombi, which are characterized by well-organized fibrin filled with abundant activated platelets. Herein, Janus rod (JR)-shaped micromotors are constructed by side-by-side electrospinning and cryosection, possessing advantages in controlling the Janus structure and aspect ratio of microrods. Silicon phthalocyanine (Pc) and CaO₂ nanoparticles (NPs) are loaded into the separate sides of JRs, and Arg-Gly-Asp (RGD) peptides are grafted on the surface to obtain Pc/Ca@r-JRs for the sonodynamic therapy (SDT) of thrombosis without using any thrombolytic agents. Decomposition of CaO₂ NPs ejects O₂ bubbles from one side of JRs, and ultrasonication of O₂ bubbles produces the cavitation effect, both generating mechanical force to drive the thrombus penetration. The integration of ultrasonication-propelled motion and RGD mediation effectively increases the targeting capabilities of r-JRs to activated platelets. In addition to mechanical thrombolysis, ultrasonication of the released Pc produces ¹O₂ to destruct fibrin networks of clots. In vitro thrombolysis of whole blood clots shows that ultrasonication of Pc/Ca@r-JRs has a significantly higher thrombolysis rate (73.6%) than those without propelled motion or RGD-mediated clot targeting. In a lower limb thrombosis model, intravenous administration of Pc/Ca@r-JRs indicates 3.4-fold higher accumulations at the clot site than those of JRs, and ultrasonication-propelled motion further increases thrombus retention 2.1 times. Treatment with Pc/Ca@r-JRs and ultrasonication fully removes thrombi and significantly prolongs tail bleeding time. Thus, this study has achieved precise and prompt thrombolysis through selective targeting to clots, efficient penetration into dense networks of thrombi, and SDT-executed thrombolysis.

Thrombus-specific theranostic nanocomposite for codelivery of thrombolytic drug, algae-derived anticoagulant and NIR fluorescent contrast agent

Thrombolysis is a standard treatment for rapidly restoring blood flow. However, the application of urokinase-type plasminogen activator (Uk) in clinical therapy is limited due to its nonspecific distribution and inadequate therapeutic accumulation. Precise thrombus imaging and site-specific drug delivery can enhance the diagnostic and therapeutic efficacy for thrombosis. Accordingly, we developed a P-selectin-specific, photothermal theranostic nanocomposite for thrombus-targeted codelivery of Uk and indocyanine green (ICG, a contrast agent for near-infrared (NIR) fluorescence imaging). We evaluated its capabilities for thrombus imaging and enzyme/hyperthermia combined thrombolytic therapy. Mesoporous silica-coated gold nanorods (Si-AuNRs) were functionalized with an arginine-rich peptide to create an organic template for the adsorption of ICG and fucoidan (Fu), an algae-derived anticoagulant. Uk was loaded into the SiO₂ pores of the Si-AuNRs through the formation of a Fu-Uk-ICG complex on the peptide-functionalized template. The Fu-Uk/ICG@SiAu NRs nanocomposite increased the photostability of ICG and improved its targeting/accumulation at blood clot sites with a strong NIR fluorescence intensity for precise thrombus imaging. Furthermore, ICG incorporated into the nanocomposite enhanced the photothermal effect of Si-AuNRs. Fu, as a P-selectin-targeting ligand, enabled the nanocomposite to target a thrombus site where platelets were activated. The nanocomposite enabled a faster release of Uk for rapid clearing of blood clots and a slower release of Fu for longer lasting prevention of thrombosis regeneration. The nanocomposite with multiple functions, including thrombus-targeting drug delivery, photothermal thrombolysis, and NIR fluorescence imaging, is thus an advanced theranostic platform for thrombolytic therapy with reduced hemorrhaging risk and enhanced imaging/thrombolysis efficiency. STATEMENT OF SIGNIFICANCE: Herein, for the first time, a P-selectin specific, photothermal theranostic nanocomposite for thrombus-targeted co-delivery of urokinase and NIR fluorescence contrast agent indocyanine green (ICG) was developed. We evaluated the potential of this theranostic nanocomposite for thrombus imaging and enzyme/hyperthermia combined thrombolytic therapy. The nanocomposite showed multiple functions including thrombus targeting and imaging, and photothermal thrombolysis. Besides, it allowed faster release of the thrombolytic urokinase for rapidly clearing blood clots and slower release of a brown algae-derived anticoagulant fucoidan (also acting as a P-selectin ligand) for prevention of thrombosis regeneration. The nanocomposite is thus a new and advanced theranostic platform for targeted thrombolytic therapy.

Heparin-like anticoagulant polypeptides with tunable activity: Synthesis, characterization, anticoagulative properties and clot solubilities in vitro

Due to the uncontrollable anticoagulant activity and limited source, Heparin, which is commonly used in clinical anticoagulation therapies, faces the risk of spontaneous bleeding and thrombocytopenia. Herein, a series of anionic poly(amino acid) s poly (l-Serine-ran-L-Glutamic acid-ran-L-Cysteine-SO₃) (PSEC-SO₃) were prepared by the controlled Ring Opening Polymerization (ROP) of N-Carboxyanhydrides (NCAs). The anticoagulant activities of PSEC-SO₃ can be regulated by simply adjusting the feeding ratio of monomers. In vitro tests show that these polypeptides can effectively prolong the Activated Partical Thromboplastin Time (APTT) and inhibit Factor IIa and Factor Xa, but has no significant effect on Prothrombin Time (PT) and Thrombin Time (TT), which indicates that PSEC-SO₃ mainly act on the intrinsic pathway. In summary, the activity-tunable heparin-like polypeptides are expected to have good application prospects in the anticoagulant field.

Targeted nanotherapeutics in the prophylaxis and treatment of thrombosis

Currently available anti-thrombotic therapy for the prophylaxis and treatment of arterial and venous thrombosis includes intravenous administration of anti-thrombotic drugs which lead to severe bleeding risks such as cerebral hemorrhage and stroke. Targeting approaches that utilize nanosystems to reach the thrombus sites are emerging to increase the local effect of anti-thrombotic drugs, as well as to decrease these severe bleeding complications by diminishing the systemic availability of these drugs. This review emphasizes the emerging targeted nanomedicines (liposomes, micelles, polymeric nanoparticles, material bases nanoparticles and other biological vectors) for the prophylaxis and treatment of thrombotic events as well as multifunctional nanomedicines for theranostic applications. Nanomedicine offers a promising platform for a smart, safe, and effective approach for the management of thrombosis.

Hydrogen peroxide-responsive platelet membrane-coated nanoparticles for thrombus therapy

Occlusion of blood vessels caused by thrombi is the major pathogenesis of various catastrophic cardiovascular diseases. Thrombi can be prevented or treated by antithrombotic drugs. However, free antithrombotic drugs often have relatively low therapeutic efficacy due to a number of limitations such as short half-life, unexpected bleeding complications, low thrombus targeting capability, and negligible hydrogen peroxide (H2O2)-scavenging ability. Inspired by the abundance of H2O2 and the active thrombus-targeting property of platelets, a H2O2-responsive platelet membrane-cloaked argatroban-loaded polymeric nanoparticle (PNPArg) was developed for thrombus therapy. Poly(vanillyl alcohol-co-oxalate) (PVAX), a H2O2-degradable polymer, was synthesized to form an argatroban-loaded nanocore, which was further coated with platelet membrane. The PNPArg can effectively target the blood clots due to the thrombus-homing property of the cloaked platelet membrane, and subsequently exert combined H2O2-scavenging effect via the H2O2-degradable nanocarrier polymer and antithrombotic effect via argatroban, the released payload. The PNPArg effectively scavenged H2O2 and protected cells from H2O2-induced cellular injury in RAW 264.7 cells and HUVECs. The PNPArg rapidly targeted the thrombosed vessels and remarkably suppressed thrombus formation, and the levels of H2O2 and inflammatory cytokines in the ferric chloride-induced carotid arterial thrombosis mouse model. Safety assessment indicated good biocompatibility of the PNPArg. Taken together, the biomimetic PNPArg offers multiple functionalities including thrombus-targeting, antioxidation, and H2O2-stimulated antithrombotic action, thereby making it a promising therapeutic nanomedicine for thrombosis diseases.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

Functionalized polymeric hybrid micelles as an efficient nanotheranostic agent for thrombus imaging and thrombolysis

Pathological thrombosis within a vessel hampers blood flow and is the mainspring of numerous fatal cardiovascular complications. In order to specifically image and dissolve a thrombus, we rationally designed a functionalized polymeric hybrid micelle (PHM) system self-assembled from amphiphilic polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethylene glycol (PCL-PEG). Based on a biological component of thrombi, activated coagulation factor XIII (FXIIIa), which is responsible for fibrin crosslinking, we further developed FXIIIa-targeted near infrared imaging and thrombolytic nanoparticles, termed IR780/FPHM/LK NPs, through chemical conjugation of peptides to the system. In a ferric chloride (FeCl₃)-induced mouse carotid thrombosis model, IR780/FPHM/LK NPs specifically targeted the thrombus and significantly enhanced the photoacoustic signal for an accurate diagnosis. When loaded with the fibrinolytic drug lumbrokinase (LK), FPHM remarkably dissociated the thrombus accompanied by an increase in the d-dimer level, a fibrin degradation product, and alleviation of fatal nonspecific hemorrhagic risk. Given its thrombus-specific imaging along with potent therapeutic activities, IR780/FPHM/LK NPs hold promise for developing nanotheranostic agents in preclinical thrombotic vascular disease models.

Biomimetic fibrin-targeted and H2O2-responsive nanocarriers for thrombus therapy

Thrombosis is a principle cause of various life-threatening cardiovascular diseases. However, current antithrombotic treatments using drugs only offer limited efficacy due to short half-life, low targeting ability to the thrombus site, and unexpected bleeding complications. Taking into account of the biological characteristics of thrombus including upregulation of hydrogen peroxide (H₂O₂) and abundance of fibrin, we engineered a H₂O₂-responsive nanocarrier for thrombus-targeting delivery of an antithrombotic agent (i.e., tirofiban). The nanocarrier was composed of a drug-conjugated dextran nanocore and a red blood cell (RBC) membrane shell, and its surface was functionalized with a fibrin-targeting peptide, CREKA. Tirofiban was conjugated to dextran through a H₂O₂-cleavable phenylboronic ester linkage. The fibrin-targeting RBC membrane-cloaked dextran-tirofiban conjugate nanoparticles (i.e., T-RBC-DTC NPs) can scavenge H₂O₂ and provide controlled release of tirofiban to achieve site-specific antithrombotic effects. In RAW 264.7 cells and HUVECs, the T-RBC-DTC NPs effectively scavenged H₂O₂ and protected cells from H₂O₂-induced cytotoxicity. In the ferric chloride-induced carotid thrombosis mouse model, the T-RBC-DTC NPs efficiently accumulated at the injured carotid artery and exhibited significantly enhanced antithrombotic activity compared to free drug. The T-RBC-DTC NPs also exhibited good biocompatibility according to histology analysis. Overall, our results indicated that this bioengineered nanocarrier offers a promising therapeutic strategy for thrombotic disorders.

Thrombolytic Agents: Nanocarriers in Controlled Release

Thrombosis is a life-threatening pathological condition in which blood clots form in blood vessels, obstructing or interfering with blood flow. Thrombolytic agents (TAs) are enzymes that can catalyze the conversion of plasminogen to plasmin to dissolve blood clots. The plasmin formed by TAs breaks down fibrin clots into soluble fibrin that finally dissolves thrombi. Several TAs have been developed to treat various thromboembolic diseases, such as pulmonary embolisms, acute myocardial infarction, deep vein thrombosis, and extensive coronary emboli. However, systemic TA administration can trigger non-specific activation that can increase the incidence of bleeding. Moreover, protein-based TAs are rapidly inactivated upon injection resulting in the need for large doses. To overcome these limitations, various types of nanocarriers have been introduced that enhance the pharmacokinetic effects by protecting the TA from the biological environment and targeting the release into coagulation. The nanocarriers show increasing half-life, reducing side effects, and improving overall TA efficacy. In this work, the recent advances in various types of TAs and nanocarriers are thoroughly reviewed. Various types of nanocarriers, including lipid-based, polymer-based, and metal-based nanoparticles are described, for the targeted delivery of TAs. This work also provides insights into issues related to the future of TA development and successful clinical translation.

Platelet membrane-functionalized nanoparticles with improved targeting ability and lower hemorrhagic risk for thrombolysis therapy

Intravenous injection of thrombolytic drugs is the most effective strategy for the treatment of thrombotic diseases. However, the clinical application of most thrombolytic drugs is limited by hemorrhagic risks and narrow therapeutic index. The targeted drug delivery systems may help to address these problems. Inspired by the crucial role of platelets in the process of thrombus, Platelet membrane-coated PLGA cores loading lumbrokinase (PNPs/LBK) were designed for effective thrombolysis with reduced hemorrhagic risk. Using a mouse carotid thrombosis model, the affinity of platelet membrane-coated nanoparticles to the thrombus was confirmed. Also, the PNPs/LBK exhibited excellent thrombolytic efficacy at a low dose, compared with free LBK. More importantly, PNPs/LBK showed less adverse effect on the function of the coagulation system, and thus reduced hemorrhagic risk. These results indicated that a promising thrombus-targeted drug delivery system was achieved by coating PLGA nanoparticles with platelet membrane. Such rationally designed drug delivery system will provide a broad platform for thrombus treatment.

Emerging nanotherapeutics for antithrombotic treatment

Thrombus causes insufficient blood flow and ischemia damages to brain and heart, leading to life-threatening cardio-cerebrovascular diseases. Development of efficient antithrombotic strategies has long been a high priority, owing to the high morbidity and mortality of thrombotic diseases. With the rapid development of biomedical nanotechnology in diagnosis and treatment of thrombotic disorder, remarkable progresses have been made in antithrombotic nanomedicines in recent years. Herein, we outline the recent advances in this field at the intersection of thrombus theranostics and biomedical nanotechnology. First, thrombus diagnosis techniques based on biomedical nanotechnology are presented. Then, emerging antithrombotic nanotherapeutics are overviewed, including thrombus-targeting strategies, thrombus stimuli-responsive nanosystems and phase transition-driven nanotherapeutics. Furthermore, multifunctional nanosystems for combination theranostics of thrombotic diseases are discussed. Finally, the design considerations, advantages and challenges of these biomedical nanotechnology-driven therapeutics in clinical translation are highlighted.

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.

Intrinsic Biotaxi Solution Based on Blood Cell Membrane Cloaking Enables Fullerenol Thrombolysis In Vivo

We report the construction of blood cell membrane cloaked mesoporous silica nanoparticles for delivery of nanoparticles [fullerenols (Fols)] with fibrinolysis activity which endows the active Fol with successful thrombolysis effect in vivo. In vitro, Fols present excellent fibrinolysis activity, and the Fol with the best fibrinolysis activity is screened based on the correlation between Fols' structure and their fibrinolysis activity. However, the thrombolytic effect in vivo is not satisfactory. To rectify the unsatisfactory situation and avoid the exogenous stimuli, a natural blood cell membrane cloaking strategy with loading the active Fol is chosen to explore as a novel thrombolysis drug. After cloaking, the therapeutic platform prolongs blood circulation time and enhances the targeting effect. Interestingly, compared with platelet membrane cloaking, red blood cell (RBC) membrane cloaking demonstrates stronger affinity with fibrin and more enrichment at the thrombus site. The Fol with RBC cloaking shows quick and efficient thrombolysis efficacy in vivo with less bleeding risk, more excellent blood compatibility, and better biosafety when compared with the clinical drug urokinase (UK). These findings not only validate the blood cell membrane cloaking strategy as an effective platform for Fol delivery on thrombolysis treatment, but also hold a great promising solution for other active nanoparticle deliveries in vivo.

Synthesis of Multiarm Peptide Dendrimers for Dual Targeted Thrombolysis

Current thrombolytic agents generally possess low specificity and pose a high risk of intracranial hemorrhage. Here, various generations of multiarm polylactic acid-polyglutamic acid peptide dendrimers were synthesized, and then nattokinase-combining magnetic Fe₃O₄ nanoparticles and RGD-modified dendrimers (Fe₃O₄-(4-PLA(G₃)₄)-RGD) were fabricated for targeted thrombi dissolution. Their in vitro and in vivo thrombolytic properties were determined. In vitro determination indicated that Fe₃O₄-(4-PLA(G₃)₄)-RGD/nattokinase provided 3-fold higher blood clot dissolution than that obtained with free nattokinase. An in vivo thrombolytic examination revealed that most of the thrombi were dissolved under an external magnetic field. In addition, there were many nanoparticles in vascular endothelial cells, demonstrating the RGD and magnetic dual targeting capacity of Fe₃O₄-(4-PLA(G₃)₄)-RGD/nattokinase. These results demonstrated that Fe₃O₄-(4-PLA(G₃)₄)-RGD nanoparticles not only will deliver targeted thrombolytic agents to enhance the efficacy of site-specific thrombolytic treatment but also have potential in the diagnosis of thrombotic disease in its early stages.

Nanomedicines: A Potential Treatment for Blood Disorder Diseases

Blood disorder diseases (BDDs), also known as hematologic, is one of the diseases owing to hematopoietic system disorder. Chemotherapy, bone marrow transplantation, and stem cells therapy have been used to treat BDDs. However, the cure rates are still low due to the availability of the right type of bone marrow and the likelihood of recurrence and infection. With the rapid development of nanotechnology in the field of biomedicine, artificial blood or blood substitute has shown promising features for the emergency treatment of BDDs. Herein, we surveyed recent advances in the development of artificial blood components: gas carrier components (erythrocyte substitutes), immune response components (white blood cell substitutes), and hemostasis-responsive components (platelet substitutes). Platelet-inspired nanomedicines for cancer treatment were also discussed. The challenges and prospects of these treatment options in future nanomedicine development are discussed.

E-Selectin-Binding Peptide-Modified Bovine Serum Albumin Nanoparticles for the Treatment of Acute Lung Injury

Currently, there is no specific treatment for acute lung injury (ALI). E-selectin-binding peptide (Esbp), a high-affinity peptide that delivers drugs targeting inflammatory vascular endothelial cells, can bind to E-selectin and act as a targeting ligand for selective drug delivery. In this study, we coupled the thiol groups of Esbp to the amino groups on the surface of bovine serum albumin (BSA) using succinimidyl iodoacetic acid to make Esbp-modified BSA nanoparticles (BSANPs) at the average ratio of 19.3 μg Esbp to 1 mg BSA. The Esbp-modified BSANPs were spherical in shape and had a particle size of 266.7 ± 2.7 nm, polydispersity index of 0.165 ± 0.02, zeta potential of - 33.64 ± 1.23 mV, encapsulation efficiency of 84.3 ± 2.3%, and drug loading of 6.7 ± 0.32%. The cumulative release rate of dexamethasone-loaded Esbp-modified BSANPs was 51.2% within 12 h, significantly lower than that of 88.2% of free drugs. Moreover, Esbp-modified BSANPs could be uptaken in vitro by activated human umbilical vein endothelial cells and in vivo by the lungs of the established ALI mouse model. These results indicated that our Esbp-modified BSANPs delivery system has characteristics of good targeting ability and biocompatibility and is able to inhibit inflammation. Overall, our Esbp-modified BSANPs delivery system has therapeutic potentials as a new targeting drug system for the treatment of ALI in the future.

Molecular determinants as therapeutic targets in cancer chemotherapy: An update

It is well known that cancer cells are heterogeneous in nature and very distinct from their normal counterparts. Commonly these cancer cells possess different and complementary metabolic profile, microenvironment and adopting behaviors to generate more ATPs to fulfill the requirement of high energy that is further utilized in the production of proteins and other essentials required for cell survival, growth, and proliferation. These differences create many challenges in cancer treatments. On the contrary, such situations of metabolic differences between cancer and normal cells may be expected a promising strategy for treatment purpose. In this article, we focus on the molecular determinants of oncogene-specific sub-organelles such as potential metabolites of mitochondria (reactive oxygen species, apoptotic proteins, cytochrome c, caspase 9, caspase 3, etc.), endoplasmic reticulum (unfolded protein response, PKR-like ER kinase, C/EBP homologous protein, etc.), nucleus (nucleolar phosphoprotein, nuclear pore complex, nuclear localization signal), lysosome (microenvironment, etc.) and plasma membrane phospholipids, etc. that might be exploited for the targeted delivery of anti-cancer drugs for therapeutic benefits. This review will help to understand the various targets of subcellular organelles at molecular levels. In the future, this molecular level understanding may be combined with the genomic profile of cancer for the development of the molecularly guided or personalized therapeutics for complete eradication of cancer.

Synthesis and evaluation of cationic polymeric micelles as carriers of lumbrokinase for targeted thrombolysis

To achieve targeted thrombolysis, a targeted delivery system of lumbrokinase (LK) was constructed using RGDfk-conjugated hybrid micelles. Based on the specific affinity of RGDfk to glycoprotein complex of GPⅡb/Ⅲa expressed on the surface of membrane of activated platelet, LK loaded targeted micelles (LKTM) can be delivered to thrombus. The hybrid micelles were composed of polycaprolactone-block-poly (2-(dimethylamino) ethyl methacrylate) (PCL-PDMAEMA), methoxy polyethylene glycol-block- polycaprolactone (mPEG-PCL) and RGDfk conjugated polycaprolactone-block- polyethylene glycol (PCL-PEG-RGDfk). PCL-PDMAEMA was synthesized via ring open polymerization (ROP) and atom transfer radical polymerization (ATRP). PCL-PEG-RGDfk was synthesized via ROP and carbodiimide chemistry. The prepared LKTM was characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). Colloidal stability assay showed the prepared LKTM was stable. Biocompatibility assay was performed to determine the safe concentration range of polymer. The assay of fluorescent distribution in vivo demonstrated that LKTM can be efficiently delivered to thrombi in vivo. Thrombolysis in vivo indicated the thrombolytic potency of LKTM was optimal in all groups. Notably, the laboratory mice treated with LKTM exhibited a significantly shorter tail bleeding time compared to those treated with LK or LK-loaded micelles without RGDfk, which suggested that the targeted delivery of LK using RGDfk-conjugated hybrid micelles effectively reduced the bleeding risk.

Platelet for drug delivery

Platelets play a vital physiological role in hemostasis, inflammation and tissue regeneration, which are associated with wound healing as well as cancer development and metastasis. These years, a variety of platelet-mediated drug delivery approaches have been developed due to their unique properties, such as quick replenishment and site-specific activation/adhesion. In this Current Opinion, focuses are put on strategies leveraging the physiological functions of platelets for the design of drug delivery systems, including platelet engineering, platelet hitchhiking, membrane coating, synthetic platelet fabrication and platelet-triggered drug release for different applications.

Co-delivery of Metformin and Paclitaxel Via Folate-Modified pH-Sensitive Micelles for Enhanced Anti-tumor Efficacy

Single chemotherapeutic agent like paclitaxel (PTX) has shown some limitations in anti-tumor treatment, such as undesirable side effects, multidrug resistance, and high toxicity. In order to reduce the toxicity of PTX and increase the anti-tumor effect, folate-modified amphiphilic and biodegradable biomaterial was developed to co-deliver PTX and metformin (MET) for exerting the synergistic effect. PTX was physically entrapped in the hydrophobic inner core of the amphiphilic block copolymer by a solvent evaporation method, whereas MET was chemically conjugated to the hydrophilic terminals of copolymer via a pH-sensitive cis-aconityl linkage (Cis). The in vitro release behaviors of the drugs were analyzed by high-performance liquid chromatography (HPLC), and the synergistic effect of the drugs was evaluated by a Q value method. Results showed that drug-loaded micelles with an average size about 100 nm were successfully constructed. In acidic environments, the chemically conjugated MET was rapidly released after the breakage of sensitive bond between drug and copolymer. In vitro anti-tumor studies demonstrated that MET and PTX had a synergistic effect and co-delivery micelles induced higher cytotoxicity and apoptosis against 4T1 breast cancer cells than free drugs. Furthermore, folate-targeted co-delivery micelles increased the cellular uptake of drugs and were found to be effective for the treatment of solid tumor in vivo. These findings indicated that co-delivery of MET and PTX through the polymeric micelles is a promising strategy for cancer therapy.