Changsun Kang

H2O2-triggered bubble generating antioxidant polymeric nanoparticles as ischemia/reperfusion targeted nanotheranostics.

Overproduction of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) leads to oxidative stress, causing inflammation and cellular damages and death. H2O2 is one of the most stable and abundant ROS and H2O2-mediated oxidative stress is considered as a key mediator of cellular and tissue damages during ischemia/reperfusion (I/R) injury. Therefore, H2O2 could hold tremendous potential as a diagnostic biomarker and therapeutic target for oxidative stress-associated inflammatory conditions such as I/R injury. Here, we report a novel nanotheranostic agent that can express ultrasound imaging and simultaneous therapeutic effects for hepatic I/R treatment, which is based on H2O2-triggered CO2-generating antioxidant poly(vanillin oxalate) (PVO). PVO nanoparticles generate CO2 through H2O2-triggered oxidation of peroxalate esters and release vanillin, which exerts antioxidant and anti-inflammatory activities. PVO nanoparticles intravenously administrated remarkably enhanced the ultrasound signal in the site of hepatic I/R injury and also effectively suppressed the liver damages by inhibiting inflammation and apoptosis. To our best understanding, H2O2-responsive PVO is the first platform which generates bubbles to serve as ultrasound contrast agents and also exerts therapeutic activities. We therefore anticipate that H2O2-triggered bubble-generating antioxidant PVO nanoparticles have great potential for ultrasound imaging and therapy of H2O2-associated diseases.

Hydrogen peroxide-activatable antioxidant prodrug as a targeted therapeutic agent for ischemia-reperfusion injury.

Overproduction of hydrogen peroxide (H2O2) causes oxidative stress and is the main culprit in the pathogenesis of ischemia/reperfusion (I/R) injury. Suppression of oxidative stress is therefore critical in the treatment of I/R injury. Here, we report H2O2-activatable antioxidant prodrug (BRAP) that is capable of specifically targeting the site of oxidative stress and exerting anti-inflammatory and anti-apoptotic activities. BRAP with a self-immolative boronic ester protecting group was designed to scavenge H2O2 and release HBA (p-hydroxybenzyl alcohol) with antioxidant and anti-inflammatory activities. BRAP exerted potent antioxidant and anti-inflammatory activity in lipopolysaccharide (LPS)- and H2O2-stimulated cells by suppressing the generation of ROS and pro-inflammatory cytokines. In mouse models of hepatic I/R and cardiac I/R, BRAP exerted potent antioxidant, anti-inflammatory and anti-apoptotic activities due to the synergistic effects of H2O2-scavenging boronic esters and therapeutic HBA. In addition, administration of high doses of BRAP daily for 7 days showed no renal or hepatic function abnormalities. Therefore BRAP has tremendous therapeutic potential as H2O2-activatable antioxidant prodrug for the treatment of I/R injuries.

Porous antioxidant polymer microparticles as therapeutic systems for the airway inflammatory diseases.

Inhaling steroidal anti-inflammatory drugs is the most common treatment for airway inflammatory diseases such as asthma. However, frequent steroid administration causes adverse side effects. Therefore, the successful clinical translation of numerous steroidal drugs greatly needs pulmonary drug delivery systems which are formulated from biocompatible and non-immunogenic polymers. We have recently developed a new family of biodegradable polymer, vanillyl alcohol-containing copolyoxalate (PVAX) which is able to scavenge hydrogen peroxide and exert potent antioxidant and anti-inflammatory activity. In this work, we report the therapeutic potential of porous PVAX microparticles which encapsulate dexamethasone (DEX) as a therapeutic system for airway inflammatory diseases. PVAX microparticles themselves reduced oxidative stress and suppressed the expression of pro-inflammatory tumor necrosis factor-alpha and inducible nitric oxide synthase in the lung of ovalbumin-challenged asthmatic mice. However, DEX-loaded porous PVAX microparticles showed significantly enhanced therapeutic effects than PVAX microparticles, suggesting the synergistic effects of PVAX with DEX. In addition, PVAX microparticles showed no inflammatory responses to lung tissues. Given their excellent biocompatibility and intrinsic antioxidant and anti-inflammatory activity, PVAX microparticles hold tremendous potential as therapeutic systems for the treatment of airway inflammatory diseases such as asthma.

Hydrogen Peroxide‐Responsive Nanoparticle Reduces Myocardial Ischemia/Reperfusion Injury

Background During myocardial ischemia/reperfusion (I/R), a large amount of reactive oxygen species (ROS) is produced. In particular, overproduction of hydrogen peroxide (H2O2) is considered to be a main cause of I/R‐mediated tissue damage. We generated novel H2O2‐responsive antioxidant polymer nanoparticles (PVAX and HPOX) that are able to target the site of ROS overproduction and attenuate the oxidative stress‐associated diseases. In this study, nanoparticles were examined for their therapeutic effect on myocardial I/R injury. Methods and Results The therapeutic effect of nanoparticles during cardiac I/R was evaluated in mice. A single dose of PVAX (3 mg/kg) showed a significant improvement in both cardiac output and fraction shortening compared with poly(lactic‐coglycolic acid) (PLGA) particle, a non‐H2O2‐activatable nanoparticle. PVAX also significantly reduced the myocardial infarction/area compared with PLGA (48.7±4.2 vs 14.5±2.1). In addition, PVAX effectively reduced caspase‐3 activation and TUNEL‐positive cells compared with PLGA. Furthermore, PVAX significantly decreased TNF‐α and MCP‐1 mRNA levels. To explore the antioxidant effect of PVAX by scavenging ROS, dihydroethidium staining was used as an indicator of ROS generation. PVAX effectively suppressed the generation of ROS caused by I/R, whereas a number of dihydroethidium‐positive cells were observed in a group with PLGA I/R. In addition, PVAX significantly reduced the level of NADPH oxidase (NOX) 2 and 4 expression, which favors the reduction in ROS generation after I/R. Conclusions Taken together, these results suggest that H2O2‐responsive antioxidant PVAX has tremendous potential as a therapeutic agent for myocardial I/R injury.

H2O2-responsive antioxidant polymeric nanoparticles as therapeutic agents for peripheral arterial disease.

Peripheral artery disease (PAD) is a common circulatory disorder in which narrowed arteries limit blood flow to the lower extremity and affect millions of people worldwide. Therapeutic angiogenesis has emerged as a promising strategy to treat PAD patients because surgical intervention has been showing limited success. Leg muscles of PAD patients have significantly high level of ROS (reactive oxygen species) and the increased production of ROS is a key mechanism of initiation and progression of PAD. We have recently developed H2O2-responsive polymer PVAX, which is designed to rapidly scavenge H2O2 and release vanillyl alcohol with antioxidant and anti-inflammatory activity. In this study, we investigated the therapeutic efficacy of PVAX nanoparticles for PAD using a cell culture model and a mouse model of hindlimb ischemia. PVAX nanoparticles significantly enhanced the expression of angiogenic inducers such as vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule (PECAM)-1 in human umbilical vein endothelial cells (HUVEC). PVAX nanoparticles promoted revascularization and restoration of blood perfusion into ischemic tissues by upregulating angiogenic VEGF and PECAM-1. This work demonstrates that H2O2-responsive PVAX nanoparticles facilitate therapeutic angiogenesis and hold tremendous translational potential as therapeutic systems for ischemic diseases such as PAD.

Fibrin-Targeted and H2O2-Responsive Nanoparticles as a Theranostics for Thrombosed Vessels

A thrombus (blood clot) is formed in injured vessels to maintain the integrity of vasculature. However, obstruction of blood vessels by thrombosis slows blood flow, leading to death of tissues fed by the artery and is the main culprit of various life-threatening cardiovascular diseases. Herein, we report a rationally designed nanomedicine that could specifically image obstructed vessels and inhibit thrombus formation. On the basis of the physicochemical and biological characteristics of thrombi such as an abundance of fibrin and an elevated level of hydrogen peroxide (H2O2), we developed a fibrin-targeted imaging and antithrombotic nanomedicine, termed FTIAN, as a theranostic system for obstructive thrombosis. FTIAN inhibited the generation of H2O2 and suppressed the expression of tumor necrosis factor-alpha (TNF-α) and soluble CD40 ligand (sCD40L) in activated platelets, demonstrating its intrinsic antioxidant, anti-inflammatory, and antiplatelet activity. In a mouse model of ferric chloride (FeCl3)-induced carotid thrombosis, FTIAN specifically targeted the obstructive thrombus and significantly enhanced the fluorescence/photoacoustic signal. When loaded with the antiplatelet drug tirofiban, FTIAN remarkably suppressed thrombus formation. Given its thrombus-specific imaging along with excellent therapeutic activities, FTIAN offers tremendous translational potential as a nanotheranostic agent for obstructive thrombosis.

Dual Stimuli-Activatable Oxidative Stress Amplifying Agent as a Hybrid Anticancer Prodrug

Compared to normal cells, cancer cells have a higher level of reactive oxygen species (ROS) due to aberrant metabolism and disruption of redox homeostasis which drive their proliferation and promote progression and metastasis of cancers. The altered redox balance and biological difference between normal cells and cancer cells provide a basis for the development of anticancer agents which are able to generate pharmacological ROS insults to kill cancer cells preferentially. In this study, we report a new hybrid anticancer drug, termed OSamp, which undergoes esterase- and acid-catalyzed hydrolysis to deplete antioxidant glutathione (GSH) and generate ROS, simultaneously. OSamp significantly elevated oxidative stress in cancer cells, leading to enhanced apoptotic cancer cell death through mitochondrial membrane disruption, cytochrome c release, activation of pro-caspase 3, and deactivation of STAT3 (signal transducer and activator of transcription-3). OSamp, administered intravenously, significantly suppressed the tumor growth in a mouse model of tumor xenografts without notable side effects. Oxidative stress amplifying OSamp holds tremendous potential as a new anticancer therapeutic and provides a new therapeutic paradigm which can be extended to development of hybrid anticancer drugs.

Molecularly Engineered Theranostic Nanoparticles for Thrombosed Vessels: H2O2-Activatable Contrast-Enhanced Photoacoustic Imaging and Antithrombotic Therapy

A thrombus (blood clot), composed mainly of activated platelets and fibrin, obstructs arteries or veins, leading to various life-threatening diseases. Inspired by the distinctive physicochemical characteristics of thrombi such as abundant fibrin and an elevated level of hydrogen peroxide (H2O2), we developed thrombus-specific theranostic (T-FBM) nanoparticles that could provide H2O2-triggered photoacoustic signal amplification and serve as an antithrombotic nanomedicine. T-FBM nanoparticles were designed to target fibrin-rich thrombi and be activated by H2O2 to generate CO2 bubbles to amplify the photoacoustic signal. In the phantom studies, T-FBM nanoparticles showed significant amplification of ultrasound/photoacoustic signals in a H2O2-triggered manner. T-FBM nanoparticles also exerted H2O2-activatable antioxidant, anti-inflammatory, and antiplatelet activities on endothelial cells. In mouse models of carotid arterial injury, T-FBM nanoparticles significantly enhanced the photoacoustic contrast specifically in thrombosed vessels and significantly suppressed thrombus formation. We anticipate that T-FBM nanoparticles hold great translational potential as nanotheranostics for H2O2-associated cardiovascular diseases.

Ultrasonographic Imaging and Anti-inflammatory Therapy of Muscle and Tendon Injuries Using Polymer Nanoparticles

Ultrasonography is a reliable diagnostic modality for muscle and tendon injuries, but it has been challenging to find right diagnosis of minor musculoskeletal injuries by conventional ultrasonographic imaging. A large amount of hydrogen peroxide (H2O2) are known to be generated during tissue damages such as mechanical injury and therefore H2O2 holds great potential as a diagnostic and therapeutic marker for mechanical injuries in the musculoskeletal system. We previously developed poly(vanillyl alcohol-co-oxalate) (PVAX), which rapidly scavenges H2O2 and exerts antioxidant and anti-inflammatory activity in H2O2-associated diseases. Based on the notion that PVAX nanoparticles generate CO2 bubbles through H2O2-triggered hydrolysis, we postulated that PVAX nanoparticles could serve as ultrasonographic contrast agents and therapeutic agents for musculoskeletal injuries associated with overproduction of H2O2. In the agarose gel phantom study, PVAX nanoparticles continuously generated CO2 bubbles to enhance ultrasonographic echogenicity significantly. Contusion injury significantly elevated the level of H2O2 in skeletal muscles and Achilles tendons. Upon intramuscular injection, PVAX nanoparticles significantly elevated the ultrasound contrast and suppressed inflammation and apoptosis in the contusion injury of musculoskeletal systems. We anticipate that PVAX nanoparticles hold great translational potential as theranostic agents for musculoskeletal injuries.

Ultrasound imaging and on-demand therapy of peripheral arterial diseases using H 2 O 2 -Activated bubble generating anti-inflammatory polymer particles

Muscles of peripheral artery disease (PAD) patients are under oxidative stress associated with a significantly elevated level of reactive oxygen species (ROS) including hydrogen peroxide (H2O2). Curcumin is a major active constituent of turmeric and is well known for its highly potent antioxidant, anti-inflammatory and angiogenic effects. We previously reported antioxidant vanillyl alcohol-incorporated copolyoxalate (PVAX) which is designed to rapidly scavenge H2O2 and release bioactive vanillyl alcohol and CO2 in a H2O2-triggered manner. In this work, we developed curcumin-loaded PVAX (CUR-PVAX) nanoparticles as contrast-enhanced ultrasound imaging agents as well as on-demand therapeutic agents for ischemic injuries based on the hypothesis that PVAX nanoparticles generate echogenic CO2 bubbles through H2O2-triggered oxidation of peroxalate esters and the merger of curcumin and PVAX exerts H2O2-activatable synergistic therapeutic actions. CUR-PVAX nanoparticles also displayed the drastic ultrasound signal in ischemic areas by generating CO2 bubbles. CUR-PVAX nanoparticles exhibited significantly higher antioxidant and anti-inflammatory activities than empty PVAX nanoparticles and equivalent curcumin in vascular endothelial cells. A mouse model of ischemic injury was used to evaluate the potential of CUR-PVAX nanoparticles as ultrasound imaging agents and on-demand therapeutic agents. CUR-PVAX nanoparticles significantly suppressed the expression of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). Moreover, CUR-PVAX nanoparticles significantly enhanced the level of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1, also known as CD31), leading to blood perfusion into ischemic tissues. We, therefore, believe that CUR-PVAX nanoparticles hold great translational potential as novel theranostic agents for ischemic diseases such as PAD.