Thrombus targeting aspirin particles for near infrared imaging and on-demand therapy of thrombotic vascular diseases

pH-Responsive Theranostic Colloidosome Drug Carriers Enable Real-Time Imaging of Targeted Thrombolytic Process with Near-Infrared-II for Deep Venous Thrombosis

Thrombosis can cause life-threatening disorders. Unfortunately, current therapeutic methods for thrombosis using injecting thrombolytic medicines systemically resulted in unexpected bleeding complications. Moreover, the absence of practical imaging tools for thrombi raised dangers of undertreatment and overtreatment. This study develops a theranostic drug carrier, Pkr(IR-Ca/Pda-uPA)-cRGD, that enables real-time monitoring of the targeted thrombolytic process of deep vein thrombosis (DVT). Pkr(IR-Ca/Pda-uPA)-cRGD, which is prepared from a Pickering-emulsion-like system, encapsulates both near-infrared-II (NIR-II) contrast agent (IR-1048 dye, loading capacity: 28%) and urokinase plasminogen activators (uPAs, encapsulation efficiency: 89%), pioneering the loading of multiple drugs with contrasting hydrophilicity into one single-drug carrier. Upon intravenous injection, Pkr(IR-Ca/Pda-uPA)-cRGD considerably targets to thrombi selectively (targeting rate: 91%) and disintegrates in response to acidic thrombi to release IR-1048 dye and uPA for imaging and thrombolysis, respectively. Investigations indicate that Pkr(IR-Ca/Pda-uPA)-cRGD enabled real-time visualization of targeted thrombolysis using NIR-II imaging in DVT models, in which thrombi were eliminated (120 min after drug injection) without bleeding complications. This may be the first study using convenient NIR-II imaging for real-time visualization of targeted thrombolysis. It represents the precision medicine that enables rapid response to acquire instantaneous medical images and make necessary real-time adjustments to diagnostic and therapeutic protocols during treatment.

Selective binding of cationic fibrinogen-mimicking chitosan nanoparticles to activated platelets and efficient drug release for antithrombotic therapy

Thrombosis is the main cause of catastrophic events including ischemic stroke, myocardial infarction and pulmonary embolism. Acetylsalicylic acid (ASA) therapy offers a desirable approach to antithrombosis through a reduction of platelet reactivity. However, major bleeding complications, severe off-target side effects, and resistance or nonresponse to ASA greatly attenuate its clinical outcomes. Herein, we report a cationic fibrinogen-mimicking nanoparticle, denoted as ASA-RGD-CS@TPP, to achieve activated-platelet-targeted delivery and efficient release of ASA for safer and more effective antithrombotic therapy. This biomimetic antithrombotic system was prepared by one-pot ionic gelation between cationic arginine-glycine-aspartic acid (RGD)-grafted chitosan (RGD-CS) and anionic tripolyphosphate (TPP). The platform exhibited selective binding to activated platelets, leading to efficient release of ASA and subsequent attenuation of platelet functions, including the remarkable inhibition of platelet aggregation through a potent blockage of cyclooxygenase-1 (COX-1). After intravenous administration, ASA-RGD-CS@TPP displayed significantly prolonged circulation time and successful prevention of thrombosis in a mouse model. ASA-RGD-CS@TPP was demonstrated to significantly enhance antithrombotic therapy while showing minimal coagulation and hemorrhagic risks and excellent biocompatibility in vivo as compared to free ASA. This platform provides a simple, safe, effective and targeted strategy for the development of antithrombotic nanomedicines.

A microthrombus-driven fixed-point cleaved nanosystem for preventing post-thrombolysis recurrence via inhibiting ferroptosis

Thrombus-induced cardiovascular diseases threaten human health. Current treatment strategies often rely on urokinase plasminogen activator (uPA) for its efficacy, yet it has such limiting factors as short half-life, lack of thrombus targeting, and systemic side effects leading to unintended bleeding. In addition, thrombolytic interventions can trigger inflammation-induced damage at thrombus sites, which affects endothelial function. To address these challenges, Fer-1/uPA@pep-CREKA-Lipo (Fu@pep-CLipo) has been developed. This system achieves precise and efficient thrombolysis while enhancing the thrombus microenvironment and mitigating ischemia-reperfusion injury, with exceptional thrombus targeting ability via the strong affinity of the Cys-Arg-Glu-Lys-Ala (CREKA) peptide for fibrin. The Cys-Nle-TPRSFL-DSPE (pep) could respond to the thrombus microenvironment and fixed-point cleavage. The uPA component linked to the liposome surface is strategically cleaved upon exposure to abundant thrombin at thrombus sites. Importantly, the inclusion of Fer-1 within Fu@pep-CLipo contributes to reactive oxygen species (ROS) scavenging and significantly improves the thrombus microenvironment. This innovative approach not only achieves highly efficient and precise thrombolysis but also positively influences the expression of eNOS protein while suppressing inflammatory factors like TNF-α and IL-6. This dual action contributes to improved thrombus inflammatory microenvironment and mitigated ischemia-reperfusion injury.

Nanocarrier Design for Dual-Targeted Therapy of In-Stent Restenosis

The injury-triggered reocclusion (restenosis) of arteries treated with angioplasty to relieve atherosclerotic obstruction remains a challenge due to limitations of existing therapies. A combination of magnetic guidance and affinity-mediated arterial binding can pave the way to a new approach for treating restenosis by enabling efficient site-specific localization of therapeutic agents formulated in magnetizable nanoparticles (MNPs) and by maintaining their presence at the site of arterial injury throughout the vulnerability period of the disease. In these studies, we investigated a dual-targeted antirestenotic strategy using drug-loaded biodegradable MNPs, surface-modified with a fibrin-avid peptide to provide affinity for the injured arterial wall. The MNPs were characterized with regard to their magnetic properties, efficiency of surface functionalization, disassembly kinetics, and interaction with fibrin-coated substrates. The antiproliferative effects of MNPs formulated with paclitaxel were studied in vitro using a fetal cell line (A10) exhibiting the defining characteristics of neointimal smooth muscle cells. Animal studies examined the efficiency of combined (physical/affinity) MNP targeting to stented arteries in Sprague Dawley rats using fluorimetric analysis and fluorescent in vivo imaging. The antirestenotic effect of the dual-targeted therapy was determined in a rat model of in-stent restenosis 28 days post-treatment. The results showed that MNPs can be efficiently functionalized to exhibit a strong binding affinity using a simple two-step chemical process, without adversely affecting their size distribution, magnetic properties, or antiproliferative potency. Dual-targeted delivery strongly enhanced the localization and retention of MNPs in stented carotid arteries up to 7 days post-treatment, while minimizing redistribution of the carrier particles to peripheral tissues. Of the two targeting elements, the effect of magnetic guidance was shown to dominate arterial localization (p = 0.004 vs. 0.084 for magnetic targeting and peptide modification, respectively), consistent with the magnetically driven MNP accumulation step defining the extent of the ultimate affinity-mediated arterial binding and subsequent retention of the carrier particles. The enhanced arterial uptake and sustained presence of paclitaxel-loaded MNPs at the site of stent deployment were associated with a strong inhibition of restenosis in the rat carotid stenting model, with both the neointima-to-media ratio (N/M) and % stenosis markedly reduced in the dual-targeted treatment group (1.62 ± 0.2 and 21 ± 3 vs. 2.17 ± 0.40 and 29 ± 6 in the control animals; p < 0.05). We conclude that the dual-targeted delivery of antirestenotic agents formulated in fibrin-avid MNPs can provide a new platform for the safe and effective treatment of in-stent restenosis.

Recent theranostic applications of hydrogen peroxide-responsive nanomaterials for multiple diseases

It is well established that hydrogen peroxide (H2O2) is associated with the initiation and progression of many diseases. With the rapid development of nanotechnology, the diagnosis and treatment of those diseases could be realized through a variety of H2O2-responsive nanomaterials. In order to broaden the application prospects of H2O2-responsive nanomaterials and promote their development, understanding and summarizing the design and application fields of such materials has attracted much attention. This review provides a comprehensive summary of the types of H2O2-responsive nanomaterials including organic, inorganic and organic-inorganic hybrids in recent years, and focused on their specific design and applications. Based on the type of disease, such as tumors, bacteria, dental diseases, inflammation, cardiovascular diseases, bone injury and so on, key examples for above disease imaging diagnosis and therapy strategies are introduced. In addition, current challenges and the outlook of H2O2-responsive nanomaterials are also discussed. This review aims to stimulate the potential of H2O2-responsive nanomaterials and provide new application ideas for various functional nanomaterials related to H2O2.

Small diameter expanded polytetrafluoroethylene vascular graft with differentiated inner and outer biomacromolecules for collaborative endothelialization, anti-thrombogenicity and anti-inflammation

Without differentiated inner and outer biological function, expanded polytetrafluoroethylene (ePTFE) small-diameter (<6 mm) artificial blood vessels would fail in vivo due to foreign body rejection, thrombosis, and hyperplasia. In order to synergistically promote endothelialization, anti-thrombogenicity, and anti-inflammatory function, we modified the inner and outer surface of ePTFE, respectively, by grafting functional biomolecules, such as heparin and epigallocatechin gallate (EGCG), into the inner surface and polyethyleneimine and rapamycin into the outer surface via layer-by-layer self-assembly. Fourier-transform infrared spectroscopy showed the successful incorporation of EGCG, heparin, and rapamycin. The collaborative release profile of heparin and rapamycin lasted for 42 days, respectively. The inner surface promoted human umbilical vein endothelial cells (HUVECs) adhesion and growth and that the outer surface inhibited smooth muscle cells growth and proliferation. The modified ePTFE effectively regulated the differentiation behavior of RAW264.7, inhibited the expression of proinflammatory mediator TNF-α, and up-regulated the expression of anti-inflammatory genes Arg1 and Tgfb-1. The ex vivo circulation results indicated that the occlusions and total thrombus weight of modified ePTFE was much lower than that of the thrombus formed on the ePTFE, presenting good anti-thrombogenic properties. Hence, the straightforward yet efficient synergistic surface functionalization approach presented a potential resolution for the prospective clinical application of small-diameter ePTFE blood vessel grafts.

Clot-Targeted Antithrombotic Liposomal Nanomedicine Containing High Content of H2O2-Activatable Hybrid Prodrugs

Liposomes have been extensively explored as drug carriers, but their clinical translation has been hampered by their low drug-loading content and premature leakage of drug payloads. It was reasoned that vesicle-forming prodrugs could be incorporated into the lipid bilayer at a high molar fraction and therefore serve as a therapeutic agent as well as a structural component in liposomal nanomedicine. Boronated retinoic acid (BORA) was developed as a prodrug, which can self-assemble with common lipids to form liposomes at a high molar fraction (40%) and release all-trans retinoic acid (atRA) and hydroxybenzyl alcohol (HBA) simultaneously, in response to hydrogen peroxide (H2O2). Here, we report fucoidan-coated BORA-incorporated liposomes (f-BORALP) as clot-targeted antithrombotic liposomal nanomedicine with H2O2-triggered multiple therapeutic actions. In the mouse model of carotid arterial thrombosis, f-BORALP preferentially accumulated in the injured blood vessel and significantly suppressed thrombus formation, demonstrating their potential as targeted antithrombotic nanomedicine. This study also provides valuable insight into the development of vesicle-forming and self-immolative prodrugs to exploit the benefits of liposomal drug delivery.

Precision Navigation of Venous Thrombosis Guided by Viscosity-Activatable Near-Infrared Fluorescence

Thrombus are blood clots formed by abnormal hemostasis in blood vessels and are closely associated with various diseases such as pulmonary embolism, myocardial infarction and stroke. Early diagnosis and treatment of thrombus is the key to reducing the high risk of thrombotic disease. Given that early thrombus is small in early size, free instability, wide regional distribution and fast formation, it is urgent to develop all-inclusive detection methods that combine high signal-to-noise ratio, in situ dynamic and rapid in-depth tissue imaging. Near-infrared (NIR) fluorescence imaging, with its excellent high spatiotemporal resolution and tissue penetration depth, is a powerful technique for direct visualization of thrombotic events in situ. Considering the fibrin highly expressed in the thrombus is a typical thrombotic target. Moreover, the viscosity of the thrombus is markedly higher than its surroundings. Therefore, we developed a fibrin-targeting and viscosity-activating thrombus NIR fluorescent probe (TIR-V) for high-resolution and high-sensitivity in situ lighten-up thrombus. TIR-V has the advantages of good thrombus targeting, significant "off-on" fluorescence specific response to viscosity, bright NIR fluorescence and good biocompatibility. The thrombus is clearly delineated by a high signal-to-noise ratio NIR fluorescence imaging, enabling imaging detection and precise navigation of thrombotic regions. This work demonstrates the potential of TIR-V as a bifunctional probe for definitive diagnostic imaging and direct navigation of thrombotic lesions in clinical applications.

Thrombus-targeted nano-agents for NIR-II diagnostic fluorescence imaging-guided flap thromboembolism multi-model therapy

In oral and maxillofacial surgery, flap repair is essential to the quality of postoperative life. Still, thrombosis is fatal for the survival of the flaps. Besides, some postoperative thrombotic diseases, such as pulmonary embolism, also intimidate patients’ life. The traditional diagnostic methods are still limited by a large amount of hardware and suffer from inconvenience, delay, and subjectivity. Moreover, the treatments mainly rely upon thrombolytics, such as urokinase (UK) plasminogen activator, which may cause bleeding risk, especially intracerebral hemorrhage. Herein, a kind of poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) containing a first near-infrared window (NIR-I) phototheranostic agent Y8 and urokinase plasminogen activator (UK) as the core, and modified with the fibrin-targeting peptide Gly–Pro–Arg–Pro–Pro (GPRPP) were developed for the flap and postoperative thromboembolism treatment (named GPRPP-Y8U@P). The conjugated molecule Y8 endows GPRPP-Y8U@P with the capacity of NIR-II imaging and excellent photothermal/photodynamic therapeutic effects. In vivo experiments demonstrated that GPRPP-Y8U@P could quickly locate thrombus by NIR-II fluorescence imaging, and semi-quantitative analysis of the embolized blood vessels' paraffin section verified its thrombolytic efficiency. Additionally, the urokinase trapped in the NPs would not result in nonspecific bleeding, tremendously improving physical security and curative effects with minimizing side effects. Overall, the advantages of GPRPP-Y8U@P, such as precise localization of the thrombus, thrombus ablation in the site, and mild side effects, demonstrated the attractiveness of this approach for effective clinical monitoring of thrombus therapy.

Progress in Stimuli-Responsive Biomaterials for Treating Cardiovascular and Cerebrovascular Diseases

Cardiovascular and cerebrovascular diseases (CCVDs) describe abnormal vascular system conditions affecting the brain and heart. Among these, ischemic heart disease and ischemic stroke are the leading causes of death worldwide, resulting in 16% and 11% of deaths globally. Although several therapeutic approaches are presented over the years, the continuously increasing mortality rates suggest the need for more advanced strategies for their treatment. One of these strategies lies in the use of stimuli-responsive biomaterials. These "smart" biomaterials can specifically target the diseased tissue, and after "reading" the altered environmental cues, they can respond by altering their physicochemical properties and/or their morphology. In this review, the progress in the field of stimuli-responsive biomaterials for CCVDs in the last five years, aiming at highlighting their potential as early-stage therapeutics in the preclinical scenery, is described.

H2O2-Activatable Antioxidant Polymeric Prodrug Nanoparticles for the Prevention of Renal Ischemia/Reperfusion Injury

Renal ischemia-reperfusion (IR) injury is an inevitable complication in various clinical settings including kidney transplantation and major vascular surgeries. Renal IR injury is a major risk factor for acute kidney injury, which still remains a major clinical challenge without effective therapy. The main cause of renal IR injury is the massive production of reactive oxygen species (ROS) including hydrogen peroxide (H₂O₂) that initiate inflammatory signaling pathways, leading to renal cell death. In this study, we developed fucoidan-coated polymeric prodrug (Fu-PVU73) nanoparticles as renal IR-targeting nanotherapeutics that can rapidly eliminate H₂O₂ and exert anti-inflammatory and antiapoptotic effects. Fu-PVU73 nanoparticles were composed of H₂O₂-activatable antioxidant and anti-inflammatory polymeric prodrug (PVU73) that incorporated H₂O₂-responsive peroxalate linkages, ursodeoxycholic acid (UDCA), and vanillyl alcohol (VA) in its backbone. Fu-PVU73 nanoparticles rapidly scavenged H₂O₂ and released UDCA and VA during H₂O₂-triggered degradation. In the study of renal IR injury mouse models, Fu-PVU73 nanoparticles preferentially accumulated in the IR injury-induced kidney and markedly protected the kidney from IR injury by suppressing the generation of ROS and the expression of proinflammatory cytokines. We anticipate that Fu-PVU73 nanoparticles have tremendous therapeutic potential for not only renal IR injury but also various ROS-associated inflammatory diseases.

Nanocarrier-Based Management of Venous and Arterial Thrombosis

Cardiovascular diseases represent the leading cause of mortality worldwide, with recent epidemiological studies revealing an increasing trend of prevalence and incidence globally. Among cardiovascular disorders, both arterial and venous thrombosis and particularly their acute life-threating complications such as ischemic stroke, acute myocardial infarction, deep venous thrombosis and pulmonary embolism are responsible for more than 25% of all deaths worldwide. The modern approach following progresses in anticoagulant, thrombolytic and antiaggregant therapies has significantly improved the prognoses of these conditions in the last past decades. However, several challenges still remain such as achieving the optimal drug concentration at the injured site, reducing the shortcomings of drug resistance and the incidence of life-threatening hemorrhages. Nanomedicine is a well-known field of medicine in which atomic and molecular structures ranging between 0.1–100 nm are used in various domains due to their specific mechanical, electrical, thermal and magnetic properties. Recent experimental and clinical evidence have shown that nanotechnology could be a safe, effective and an appealing approach for various non-cardiovascular and cardiovascular diseases such as thromboembolic conditions. In this review, we have described the most promising nanotechnology-based approaches not only for the diagnosis, but also for the treatment of vascular thrombotic diseases.

Sol-Gel Co-Precipitation Synthesis, Anticoagulant and Anti-Platelet Activities of Copper-Doped Nickel Manganite Nanoparticles

Copper-substituted nickel manganites Ni_(1−x)Cu_xMn₂O₄ (Ni-TCE-NPs) were produced by co-precipitation route (sol–gel) at room temperature. Ni_(1−x)CuxMn₂O₄-Bio (NCB) NPs were studied by powder X-ray diffraction technique, scanning electron microscopy and Raman spectroscopy. XRD spectra authenticated the copper-doped nickel manganites’ formation with particle size 23–28 nm. A significant decrease in the lattice parameter confirmed the doping of copper ions into the nickel manganites. Microscopy (SEM) was used to estimate the grain size, shape and uniformity, revealing the non-uniform agglomerated polygon and plate-like microstructure. The NCB-NPs showed anticoagulant activity by enhancing the coagulation time of citrated plasma of human beings. NCB-NPs with x = 0.35 and 0.45 have increased clotting time from control 133 ± 4 s to 401 ± 7 s and 3554 ± 80 s, respectively, and others around 134 s. Additionally NCB-NPs with x = 0.35, 0.45 inhibited the platelet aggregation by 80% and 92%, while remaining inhibited with only 30%. NCB-NPs did not show hemolytic activity in RBC cells intimate its non-toxic nature. Finally, NCB-NPs were non-toxic and known to exhibit anti-blood-clotting and antiplatelet activities, which can be used in the field of biomedical applications, especially as antithrombotic agents.

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.

Organic Fluorophores for 1064 nm Excited NIR-II Fluorescence Imaging

Second near-infrared window (NIR-II) fluorescence imaging has shown great potential in the field of bioimaging. However, the excitation wavelengths of most NIR-II fluorescence dyes are in the first near-infrared (NIR-I) region, which leads to limited imaging depth and resolution. To address such issue, NIR-II fluorescence dyes with 1,064 nm excitation have been developed and applied for in vivo imaging. Compared with NIR-I wavelength excited dyes, 1,064 nm excited dyes exhibit a higher tissue penetration depth and resolution. The improved performance makes these dyes have much broader imaging applications. In this mini review, we summarize recent advances in 1,064 nm excited NIR-II fluorescence fluorophores for bioimaging. Two kinds of organic fluorophores, small molecule dye and semiconducting polymer (SP), are reviewed. The general properties of these fluorophores are first introduced. Small molecule dyes with different chemical structures for variety of bioimaging applications are then discussed, followed by the introduction of SPs for NIR-II phototheranostics. Finally, the conclusion and future perspective of this field is given.

Biomaterial-based immunotherapeutic strategies for rheumatoid arthritis

Rheumatoid arthritis (RA) is an extremely painful autoimmune disease characterized by chronic joint inflammation leading to the erosion of adjacent cartilage and bone. Rheumatoid arthritis pathology is primarily driven by inappropriate infiltration and activation of immune cells within the synovium of the joint. There is no cure for RA. As such, manifestation of symptoms entails lifelong management via various therapies that aim to generally dampen the immune system or impede the function of immune mediators. However, these treatment strategies lead to adverse effects such as toxicity, general immunosuppression, and increased risk of infection. In pursuit of safer and more efficacious therapies, many emerging biomaterial-based strategies are being developed to improve payload delivery, specific targeting, and dose efficacy, and to mitigate adverse reactions and toxicity. In this review, we highlight biomaterial-based approaches that are currently under investigation to circumvent the limitations of conventional RA treatments.

Nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke

Ischemic stroke leads to high disability and mortality. The limited delivery efficiency of most therapeutic substances is a major challenge for effective treatment of ischemic stroke. Inspired by the prominent merit of nanoscale particles in brain targeting and blood-brain barrier (BBB) penetration, various functional nanoparticles have been designed as promising drug delivery platforms that are expected to improve the therapeutic effect of ischemic stroke. Based on the complex pathological mechanisms of ischemic stroke, this review outline and summarize the rationally designed nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke, including recanalization therapy, neuroprotection therapy, and combination therapy. On this bases, the potentials and challenges of nanoparticles in the treatment of ischemic stroke are revealed, and new thoughts and perspectives are proposed for the design of feasible nanoparticles for effective treatment of ischemic stroke.

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.

Recent advances in prodrug-based nanoparticle therapeutics

Extensive research into prodrug modification of active pharmaceutical ingredients and nanoparticle drug delivery systems has led to unprecedented levels of control over the pharmacological properties of drugs and resulted in the approval of many prodrug or nanoparticle-based therapies. In recent years, the combination of these two strategies into prodrug-based nanoparticle drug delivery systems (PNDDS) has been explored as a way to further advance nanomedicine and identify novel therapies for difficult-to-treat indications. Many of the PNDDS currently in the clinical development pipeline are expected to enter the market in the coming years, making the rapidly evolving field of PNDDS highly relevant to pharmaceutical scientists. This review paper is intended to introduce PNDDS to the novice reader while also updating those working in the field with a comprehensive summary of recent efforts. To that end, first, an overview of FDA-approved prodrugs is provided to familiarize the reader with their advantages over traditional small molecule drugs and to describe the chemistries that can be used to create them. Because this article is part of a themed issue on nanoparticles, only a brief introduction to nanoparticle-based drug delivery systems is provided summarizing their successful application and unfulfilled opportunities. Finally, the review's centerpiece is a detailed discussion of rationally designed PNDDS formulations in development that successfully leverage the strengths of prodrug and nanoparticle approaches to yield highly effective therapeutic options for the treatment of many diseases.

Targeting Contrast Agents With Peak Near-Infrared-II (NIR-II) Fluorescence Emission for Non-invasive Real-Time Direct Visualization of Thrombosis

Thrombosis within the vasculature arises when pathological factors compromise normal hemostasis. On doing so, arterial thrombosis (AT) and venous thrombosis (VT) can lead to life-threatening cardio-cerebrovascular complications. Unfortunately, the therapeutic window following the onset of AT and VT is insufficient for effective treatment. As such, acute AT is the leading cause of heart attacks and constitutes ∼80% of stroke incidences, while acute VT can lead to fatal therapy complications. Early lesion detection, their accurate identification, and the subsequent appropriate treatment of thrombi can reduce the risk of thrombosis as well as its sequelae. As the success rate of therapy of fresh thrombi is higher than that of old thrombi, detection of the former and accurate identification of lesions as thrombi are of paramount importance. Magnetic resonance imaging, x-ray computed tomography (CT), and ultrasound (US) are the conventional non-invasive imaging modalities used for the detection and identification of AT and VT, but these modalities have the drawback of providing only image-delayed indirect visualization of only late stages of thrombi development. To overcome such limitations, near-infrared (NIR, ca. 700-1,700 nm) fluorescence (NIRF) imaging has been implemented due to its capability of providing non-invasive real-time direct visualization of biological structures and processes. Contrast agents designed for providing real-time direct or indirect visualization of thrombi using NIRF imaging primarily provide peak NIR-I fluorescence emission (ca. 700-1,000 nm), which affords limited tissue penetration depth and suboptimal spatiotemporal resolution. To facilitate the enhancement of the visualization of thrombosis via providing detection of smaller, fresh, and/or deep-seated thrombi in real time, the development of contrast agents with peak NIR-II fluorescence emission (ca. 1000-1,700 nm) has been recently underway. Currently, however, most contrast agents that provide peak NIR-II fluorescence emissions that are purportedly capable of providing direct visualization of thrombi or their resultant occlusions actually afford only the indirect visualization of such because they only provide for the (i) measuring of the surrounding vascular blood flow and/or (ii) simple tracing of the vasculature. These contrast agents do not target thrombi or occlusions. As such, this mini review summarizes the extremely limited number of targeting contrast agents with peak NIR-II fluorescence emission developed for non-invasive real-time direct visualization of thrombosis that have been recently reported.

Near-infrared Fluorophores for Thrombosis Diagnosis and Therapy

Thrombosis is an adverse physiological event wherein the resulting thrombus and thrombus-induced diseases collectively result in high morbidity and mortality rates. Currently, nano-medicines that incorporate fluorophores emitting in the near-infrared-I (NIR-I, 700-900 nm) spectral region into their systems have been adopted to afford thrombosis theranostics. However, several unsolved problems such as limited penetration depth and image quality severely impede further applications of such nano-medicine systems. Fortunately, the ability to incorporate fluorophores emitting in the NIR-II (1000-1700 nm) window into nano-medicine systems can unambiguously identify biological processes with high signal-to-noise, deep tissue penetration depth, and high image resolution. Considering the inherently favorable properties of NIR-II fluorophores, we believe such have enormous potential to quickly become incorporated into nano-medicine systems for thrombosis theranostics. In this review, we i) discuss the development of NIR fluorescence as an imaging modality and fluorescent agents; ii) comprehensively summarize the recent development of NIR-I fluorophore-based nano-medicine systems for thrombosis theranostics; iii) highlight the state-of-the-art NIR-II fluorophores that have been designed for the specific purpose of affording thrombotic diagnosis; iv) speculate on possible forward avenues for the use of NIR-II fluorophores towards thrombosis diagnosis and therapy; and v) discuss the potential for their clinical translation.

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.

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.

Brave new world revisited: Focus on nanomedicine

Nanomedicine is at a crossroads: with relatively few success stories in terms of clinical translation despite more and more research on increasingly sophisticated nanomaterials, it is important to consider whether we are on the right track. Indeed, it is crucial that we address the fact that while considerable efforts are being made to overcome barriers to translation from the bench to the clinic, scientists are still struggling to decipher fundamental aspects of nanomaterial interactions with biological systems. We believe that a key to the successful adoption of nanomedicines in oncology and beyond lies in a deeper understanding of underlying biological processes and in decoding interactions between engineered nanomaterials and biological systems. Here we provide an overview of progress in nanomedicine during the past 5 years.

Preparation of amphiphilic magnetic polyvinyl alcohol targeted drug carrier and drug delivery research

Currently, magnetic applications have great potential for development in the field of drug carriers. In this paper, Fe₃O₄-PVA@SH, an amphiphilic magnetically targeting drug carrier, was prepared by using Fe₃O₄ and PVA with thiohydrazide-iminopropyltriethoxysilane(TIPTS). The loading capacity of Fe₃O₄-PVA@SH on Aspirin and the drug release kinetics of loaded drugs were studied. The obtained Fe₃O₄-PVA@SH exhibits excellent drug release properties in simulating the human body fluid environment (pH 7.2). Since magnetically targeting drug carriers are readily available and have excellent biocompatibility and the characteristics of drug release. This work’s development, preparing amphiphilic magnetically targeting drug carriers in drug delivery and other fields, has great significance.

Expanded Poly(tetrafluoroethylene) Blood Vessel Grafts with Embedded Reactive Oxygen Species (ROS)-Responsive Antithrombogenic Drug for Elimination of Thrombosis

Treatment of cardiovascular diseases suffers from the lack of transplantable small-diameter blood vessel (SDBV) grafts that can prohibit/eliminate thrombosis. Although expanded poly(tetrafluoroethylene) (ePTFE) has the potential to be used for SDBV grafts, recurrence of thrombus remains the biggest challenge. In this study, a reactive oxygen species (ROS)-responsive antithrombogenic drug synthesis and a bulk coating process were employed to fabricate functional ePTFE grafts capable of prohibiting/eliminating blood clots. The synthesized drug that would release antiplatelet ethyl salicylate (ESA), in responding to ROS, was dissolved in a polycaprolactone (PCL) solution, followed by a bulk coating of the as-fabricated ePTFE grafts with the PCL/drug solution. Nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were employed to investigate and confirm the synthesis and presence of the ROS-responsive drug in the ePTFE grafts. The ESA release functions were demonstrated via the drug-release profile and dynamic anticoagulation tests. The biocompatibility of the ROS-responsive ePTFE grafts was demonstrated via lactate dehydrogenase (LDH) cytotoxicity assays, live and dead cell assays, cell morphology, and cell-graft interactions. The ROS-responsive, antithrombogenic ePTFE grafts provide a feasible way for maintaining long-term patency, potentially solving a critical challenge in SDBV applications.

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.