Rebuilding Postinfarcted Cardiac Functions by Injecting TIIA@PDA Nanoparticle-Cross-linked ROS-Sensitive Hydrogels

Progress of nanomaterials in the treatment of ischemic heart disease

Medical or surgical interventions are commonly used to alleviate the clinical symptoms of individuals suffering from ischemic heart disease (IHD), but global morbidity and mortality remain high. This is due to the complexity of disease progression and the pathological basis of IHD, which primarily includes myocardial infarction (MI), myocardial ischemia-reperfusion injury (IRI), and heart failure (HF), as well as underlying mechanisms, such as mitochondrial damage, inflammation, oxidative stress, and cardiomyocyte death. However, many drugs have limitations, such as poor stability and low bioavailability, and surgical strategies are often ineffective in preventing disease recurrence. To overcome these problems, it is necessary to develop effective drug delivery systems and technologies. Due to their advantages in enhancing drug utilization, nanomaterials are being used to control drug biodistribution and achieve targeted accumulation, addressing the therapeutic needs of IHD. In this work, we first described the clinical aspects of MI, IRI, and HF in the context of IHD as well as their shared pathological origins. Next, clinical interventional procedures for IHD are summarized. Finally, recent developments in the use of nanomaterials for the treatment of MI, IRI, and HF are highlighted, along with potential directions for future research.

Stimuli-Responsive Nanomedicines for the Treatment of Non-cancer Related Inflammatory Diseases

Nanomedicines offer a means to overcome the limitations associated with traditional drug dosage formulations by affording drug protection, enhanced drug bioavailability, and targeted drug delivery to affected sites. Inflamed tissues possess unique microenvironmental characteristics (including excessive reactive oxygen species, low pH levels, and hypoxia) that stimuli-responsive nanoparticles can employ as triggers to support on-demand delivery, enhanced accumulation, controlled release, and activation of anti-inflammatory drugs. Stimuli-responsive nanomedicines respond to physicochemical and pathological factors associated with diseased tissues to improve the specificity of drug delivery, overcome multidrug resistance, ensure accurate diagnosis and precision therapy, and control drug release to improve efficacy and safety. Current stimuli-responsive nanoparticles react to intracellular/microenvironmental stimuli such as pH, redox, hypoxia, or specific enzymes and exogenous stimuli such as temperature, magnetic fields, light, and ultrasound via bioresponsive moieties. This review summarizes the general strategies employed to produce stimuli-responsive nanoparticles tailored for inflammatory diseases and all recent advances, reports their applications in drug delivery, and illustrates the progress made toward clinical translation.

Design and advances in antioxidant hydrogels for ROS-induced oxidative disease

Reactive oxygen species (ROS) play a crucial role in human physiological processes, but oxidative stress caused by excessive ROS may lead to a variety of acute and chronic diseases. Despite the development of various strategies and biomaterials, an efficiently and broadly applied method for treatment of ROS-induced oxidative disease remains a bottleneck. Aiming to improve the local oxidative stress environment, numerous bioactive hydrogels with antioxidant properties have emerged and are proven to quickly and continuously eliminate excessive ROS. To deeply understand the design principles and applications of antioxidant hydrogels is highly beneficial for designing antioxidant hydrogels for treatment of oxidative disease. This review provides a detailed summary of recent advances in design and applications of antioxidant hydrogels for various ROS-induced oxidative diseases. In this review, the kinds of antioxidant components in antioxidant hydrogels are outlined in detail. Additionally, the crosslinking methods and the biomedical applications of antioxidant hydrogels are widely summarized and discussed, especially focusing on their usage in different types of diseases and the attention given to the treatment of diseases such as skin wounds, myocardial infarction, and osteoarthritis. Finally, the future development direction of antioxidant hydrogel is further proposed. STATEMENT OF SIGNIFICANCE: Oxidative stress is a pivotal biochemical process that plays a critical role in cellular homeostasis. Excessive cellular oxidative stress triggers an inflammatory response, which is implicated in a spectrum of associated diseases. Given the critical need for managing oxidative stress, antioxidant therapies have become a vital focus in medical research. Hydrogels have garnered substantial interest among biomaterial scientists due to their hydrophilic nature and biocompatibility. The review delves into the realm of antioxidant hydrogels, encompassing the classification of antioxidant components, the synthesis and fabrication of hydrogels, and a comprehensive overview of the biological applications and challenges of these antioxidant hydrogels. Aiming to provide new perspectives for researchers in developing cutting-edge therapeutic approaches that leverage antioxidant hydrogels.

X-ray Responsive Antioxidant Drug-Free Hydrogel for Treatment of Radiation Skin Injury

Radiotherapy (RT) is widely applied in tumor therapy, but inevitable side effects, especially for skin radiation injury, are still a fatal problem and life-threatening challenge for tumor patients. The main components of topical radiation protection preparations currently available on the market are antioxidants, such as SOD, which are limited by their unstable activity and short duration of action, making it difficult to achieve the effects of radiation protection and skin radiation damage treatment. Therefore, we designed a drug-free antioxidant hydrogel patch with encapsulated bioactive epidermal growth factor (EGF) for the treatment of radiation skin injury. The X-ray responsive hydrogel formed by copolymerization of the disulfide-containing hyperbranched poly(β-hydrazide ester) macromer polymer (PBAE), methacryloylated hyaluronic acid, and acrylamide exhibits continuous antioxidant activity through the oxidation of disulfide bonds in PBAE as well as the triggered release of EGF after X-ray responsive breakage of the polymer network to finally promote radioactive wound healing. Upon radiotherapy, the antioxidant hydrogel is able to alleviate local oxidative stress by continuously eliminating excessive ROS and can prevent deterioration of radiation skin injury. Moreover, the drug-free hydrogel with its excellent antioxidant property can overcome the disadvantages of traditional medicine (such as poor solubility, random diffusion, rapid drug clearance, and interference with tumor efficacy). Notably, the drug-free hydrogel exhibits a negligible effect for tumor therapy because the antioxidant hydrogel acts only on the epidermis and displays no shielding effect for ionization radiation. Ultimately, in vivo animal studies affirm the efficacy of our methodology, wherein the administration of the antioxidant hydrogel on acute irradiated skin attenuates the progression of radiation skin injury and promotes radioactive wound healing. This innovative strategy points out a new inspiration for the precise treatment of skin radiation damage with X-ray responsive antioxidant drug-free hydrogels.

Inhalation of macrophage membrane-coated hydrogel microparticles for inflammation alleviation of acute lung injury in vivo

Hydrogel microparticles (HMPs) have many advantages for biomedical applications, particularly for minimally invasive therapy, for example, acute lung injury (ALI) that is characterized by high levels of reactive oxygen species (ROS) and pro-inflammatory mediators in the microenvironment. In this study, ROS-scavenging and pro-inflammatory cytokine-neutralizing HMPs were designed and prepared by using a membrane emulsification device. The HMPs were composed of double bond-modified hyaluronic acid and ROS-cleavable hyperbranched poly(acrylate-capped thioketone-containing ethylene glycol) (HBPAK) containing thioketal linkages and unsaturated double bonds. Surface-coating of inflammatory macrophage (M1) cell membranes was performed to obtain the membrane-coated HBPAK HMPs (mem HMPs) via electrostatic force. The mem HMPs exhibited strong ROS-scavenging and anti-inflammatory properties both in vitro and in vivo. After administered by inhalation in an ALI mouse model, the mem HMPs reduced neutrophil infiltration and tissue oxidative damage, thereby alleviating lung inflammation. Our results suggest that the mem HMPs could serve as a potential therapeutic platform for treating inflammatory diseases with high efficiency. STATEMENT OF SIGNIFICANCE: Hydrogel microparticles (HMPs) with minimally invasive delivery are advantageous for acute lung injury (ALI) characterized by high levels of reactive oxygen species (ROS) and pro-inflammatory mediators. Herein, ROS-scavenging and pro-inflammatory cytokine-neutralizing HMPs were prepared by copolymerizing double bond-modified hyaluronic acid and ROS-cleavable hyperbranched poly(acrylate-capped thioketone-containing ethylene glycol) (HBPAK) containing thioketal bonds and unsaturated double bonds in a membrane emulsification device. The HMPs covered with inflammatory macrophage (M1) cell membranes (mem HMPs) exhibited strong ROS-scavenging and anti-inflammation properties, reduced neutrophil infiltration and tissue oxidative damage, thereby alleviating lung inflammation.

Hydrogel encapsulating gold nanoparticles for targeted delivery of nitroglycerin to reduce post-cardiac dysfunction inflammation by inhibiting the Wnt/β-catenin signaling pathway

The discovery of nitric oxide's role in biological processes like platelet function, vasodilation, cell permeability, and inflammation has advanced our understanding of organic nitrate therapy's hemodynamic and nonhemodynamic effects. Short-term use of organic nitrates prevents left ventricular enlargement and infarct expansion. However, information on their long-term impact on LV remodeling in post-acute cardiac dysfunction patients is limited. In this study, we utilized an innovative active hydrogel with gelatin (Gel)/polyethylene glycol (PEG)/polylactic acid (PLA) encapsulating gold nanoparticles (AuNPs)-based drug delivery system for the sustained release of nitroglycerin (NTG). Gel/PEG/PLA/NTG/AuNPs hydrogel-based system is a non-transplant surgical method that can adhere to the surface of the heart and deliver the drug directly to the epicardium. Cardiac dysfunction was induced by ligating the left anterior descending coronary artery. Echocardiograms were used to study the pre- and post-operative hemodynamics. Hematoxylin and eosin (H&E) and Masson's trichrome stain (MTS) staining revealed that the acute myocardial infarction (AMI) rats' group had irregularly shaped fibers and a lack of transverse striations, whereas Gel/PEG/PLA/NTG/AuNPs hydrogel group showed significant improvement. Rats in the Gel/PEG/PLA hydrogel group demonstrated marked vasodilation, compared to the AMI group. Mechanistically, we determined that hydrogel disrupts the initiation of post-cardiac dysfunction via inhibiting Wnt/β-catenin transcriptional activation. Hence, the Gel/PEG/PLA/NTG/AuNPs hydrogel group effectively protected against ischemic injury and inflammation in AMI, demonstrating a novel method for treating acute cardiac dysfunction.

Drug-Loaded Mesoporous Polydopamine Nanoparticles in Chitosan Hydrogels Enable Myocardial Infarction Repair through ROS Scavenging and Inhibition of Apoptosis

In this study, we synthesized mesoporous polydopamine nanoparticles (MPDA NPs) using an emulsion-induced interface assembly strategy and loaded epigallocatechin gallate (EGCG) into MPDA NPs via electrostatic attraction to form EGCG@MPDA NPs. In the post myocardial infarction (MI) environment, these interventions specifically aimed to eliminate reactive oxygen species (ROS) and facilitate the repair of MI. We further combined them with a thermosensitive chitosan (CS) hydrogel to construct an injectable composite hydrogel (EGCG@MPDA/CS hydrogel). Utilizing in vitro experiments, the EGCG@MPDA/CS hydrogel exhibited excellent ROS-scavenging ability of H9C2 cells under the oxidative stress environment and also could inhibit their apoptosis. The EGCG@MPDA/CS hydrogel significantly promoted left ventricular ejection fraction (LVEF) in infarcted rat models post injection for 28 days compared to the PBS group (51.25 ± 1.73% vs 29.31 ± 0.78%, P < 0.05). In comparison to the PBS group, histological analysis revealed a substantial increase in left ventricular (LV) wall thickness in the EGCG@MPDA/CS hydrogel group (from 0.58 ± 0.03 to 1.39 ± 1.11 mm, P < 0.05). This work presents a novel approach to enhance MI repair by employing the EGCG@MPDA/CS hydrogel. This hydrogel effectively reduces local oxidative stress by ROS and stimulates the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway.

Nanomedicine: A great boon for cardiac regenerative medicine

Cardiovascular disease (CVD) represents a significant global health challenge, remaining the leading cause of illness and mortality worldwide. The adult heart's limited regenerative capacity poses a major obstacle in repairing extensive damage caused by conditions like myocardial infarction. In response to these challenges, nanomedicine has emerged as a promising field aimed at improving treatment outcomes through innovative drug delivery strategies. Nanocarriers, such as nanoparticles (NPs), offer a revolutionary approach by facilitating targeted delivery of therapeutic agents directly to the heart. This precise delivery system holds immense potential for treating various cardiac conditions by addressing underlying mechanisms such as inflammation, oxidative stress, cell death, extracellular matrix remodeling, prosurvival signaling, and angiogenic pathways associated with ischemia-reperfusion injury. In this review, we provide a concise summary of the fundamental mechanisms involved in cardiac remodeling and regeneration. We explore how nanoparticle-based drug delivery systems can effectively target the afore-mentioned mechanisms. Furthermore, we discuss clinical trials that have utilized nanoparticle-based drug delivery systems specifically designed for cardiac applications. These trials demonstrate the potential of nanomedicine in clinical settings, paving the way for future advancements in cardiac therapeutics through precise and efficient drug delivery. Overall, nanomedicine holds promise in revolutionizing the treatment landscape of cardiovascular diseases by offering targeted and effective therapeutic strategies that address the complex pathophysiology of cardiac injuries.

Epicardial transplantation of antioxidant polyurethane scaffold based human amniotic epithelial stem cell patch for myocardial infarction treatment

Myocardial infarction (MI) is a leading cause of death globally. Stem cell therapy is considered a potential strategy for MI treatment. Transplantation of classic stem cells including embryonic, induced pluripotent and cardiac stem cells exhibited certain repairing effect on MI via supplementing cardiomyocytes, however, their clinical applications were blocked by problems of cell survival, differentiation, functional activity and also biosafety and ethical concerns. Here, we introduced human amniotic epithelial stem cells (hAESCs) featured with immunomodulatory activities, immune-privilege and biosafety, for constructing a stem cell cardiac patch based on porous antioxidant polyurethane (PUR), which demonstrated decent hAESCs compatibility. In rats, the administration of PUR-hAESC patch significantly reduced fibrosis and facilitated vascularization in myocardium after MI and consequently improved cardiac remodeling and function. Mechanistically, the patch provides a beneficial microenvironment for cardiac repair by facilitating a desirable immune response, paracrine modulation and limited oxidative milieu. Our findings may provide a potential therapeutic strategy for MI.

Tanshinone IIA Loaded Inhaled Polymer Nanoparticles Alleviate Established Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal respiratory disease characterized by chronic, progressive scarring of the lung parenchyma, leading to an irreversible decline in lung function. Apart from supportive care, there is currently no specific treatment available to reverse the disease. Based on the fact that tanshinone IIA (TAN) had an effect on protecting against TGF-β1-induced fibrosis through the inhibition of Smad and non-Smad signal pathways to avoid myofibroblasts activation, this study reported the development of the inhalable tanshinone IIA-loaded chitosan-oligosaccharides-coated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (CPN@TAN) for enhancing the pulmonary delivery of tanshinone IIA to treat pulmonary fibrosis. The CPN@TAN with a size of 206.5 nm exhibited excellent in vitro aerosol delivery characteristics, featuring a mass median aerodynamic diameter (MMAD) of 3.967 ± 0.025 μm and a fine particle fraction (FPF) of 70.516 ± 0.929%. Moreover, the nanoparticles showed good stability during atomization and enhanced the mucosal penetration capabilities. The results of confocal spectroscopy confirmed the potential of the nanoparticles as carriers that facilitated the uptake of drugs by NIH3T3, A549, and MH-S cells. Additionally, the nanoparticles demonstrated good in vitro biocompatibility. In a mouse model of bleomycin-induced pulmonary fibrosis, noninvasive inhalation of aerosol CPN@TAN greatly suppressed collagen formation and facilitated re-epithelialization of the destroyed alveolar epithelium without causing systemic toxicity compared with intravenous administration. Consequently, our noninvasive inhalation drug delivery technology based on polymers may represent a promising paradigm and open the door to overcoming the difficulties associated with managing pulmonary fibrosis.

Silver Nanowire Reinforced Conductive and Injectable Colloidal Gel for Effective Wound Healing Via Electrical Stimulation

The remarkable biocapacity, injectability, and adaptability of colloidal gels lead to their widespread use in tissue engineering as irregular defect implants. However, multifunctionalities including electroconductivity and antibacterial property are highly required for colloidal gels. In addition, the inherently weak mechanical property of physically crosslinked colloidal gels limits their application. Herein, Ag nanowires (Ag NWs)-reinforced colloidal gels composed of biocompatible gelatin nanoparticles and polydopamine-modified Ag NWs through the controlled electrostatic assembly, which are injectable and conductive, are presented. 1D Ag NWs can significantly improve the mechanical and electrical properties of the colloidal gel while maintaining its inherent excellent injectability. Owing to the network of Ag NWs, the storage modulus and conductivity of the optimized Ag NW colloidal gel are 7.5 and 13 times higher, respectively, than those of the colloidal gel made up of polydopamine-modified Ag nanoparticles with equivalent Ag concentration. Further, this Ag NW colloidal gel can adapt to sharp wounds on skin, which accelerates the healing of an MRSA-infected wound via electrical stimulation.

Chemically Programmed Hydrogels for Spatiotemporal Modulation of the Cardiac Pathological Microenvironment

After myocardial infarction (MI), sustained ischemic events induce pathological microenvironments characterized by ischemia-hypoxia, oxidative stress, inflammatory responses, matrix remodeling, and fibrous scarring. Conventional clinical therapies lack spatially targeted and temporally responsive modulation of the infarct microenvironment, leading to limited myocardial repair. Engineered hydrogels have a chemically programmed toolbox for minimally invasive localization of the pathological microenvironment and personalized responsive modulation over different pathological periods. Chemically programmed strategies for crosslinking interactions, interfacial binding, and topological microstructures in hydrogels enable minimally invasive implantation and in situ integration tailored to the myocardium. This enhances substance exchange and signal interactions within the infarcted microenvironment. Programmed responsive polymer networks, intelligent micro/nanoplatforms, and biological therapeutic cues contribute to the formation of microenvironment-modulated hydrogels with precise targeting, spatiotemporal control, and on-demand feedback. Therefore, this review summarizes the features of the MI microenvironment and chemically programmed schemes for hydrogels to conform, integrate, and modulate the cardiac pathological microenvironment. Chemically programmed strategies for oxygen-generating, antioxidant, anti-inflammatory, provascular, and electrointegrated hydrogels to stimulate iterative and translational cardiac tissue engineering are discussed.

Polyphosphazene Microparticles with High Free Radical Scavenging Activity for Skin Photoprotection

Ultraviolet (UV) filters are the core ingredients in sunscreens and protect against UV-induced skin damage. Nevertheless, their safety and effectiveness have been questioned in terms of their poor photostability, skin penetration, and UV-induced generation of deleterious reactive oxygen species (ROS). Herein, an organic UV filter self-framed microparticle sunblock was exploited, in which quercetin (QC) and hexachlorocyclotriphosphazene (HCCP) were self-constructed into microparticles (HCCP-QC MPs) by facile precipitation polymerization without any carriers. HCCP-QC MPs could not only significantly extend the UV shielding range to the whole UV region but also remarkably reduce UV-induced ROS while avoiding direct skin contact and the resulting epidermal penetration of small-molecule QC. Meanwhile, HCCP-QC MPs possess a high QC-loading ability (697 mg g-1) by QC itself as the microparticles' building blocks. In addition, there is no leakage issue with small molecules due to its covalently cross-linked structure. In vitro and vivo experiments also demonstrated that the HCCP-QC MPs have excellent UV protection properties and effective ROS scavenging ability without toxicity. In summary, effective UV-shielding and ROS scavenging ability coupled with excellent biocompatibility and nonpenetration of small molecules make it a broad prospect in skin protection.

Advanced Nanomedicine Approaches for Myocardial Infarction Treatment

Myocardial infarction, usually caused by the rupture of atherosclerotic plaque, leads to irreversible ischemic cardiomyocyte death within hours followed by impaired cardiac performance or even heart failure. Current interventional reperfusion strategies for myocardial infarction still face high mortality with the development of heart failure. Nanomaterial-based therapy has made great progress in reducing infarct size and promoting cardiac repair after MI, although most studies are preclinical trials. This review focuses primarily on recent progress (2016-now) in the development of various nanomedicines in the treatment of myocardial infarction. We summarize these applications with the strategy of mechanism including anti-cardiomyocyte death strategy, activation of neovascularization, antioxidants strategy, immunomodulation, anti-cardiac remodeling, and cardiac repair.

Organic Nanoparticles in Progressing Cardiovascular Disease Treatment and Diagnosis

Cardiovascular diseases (CVDs), the world's most prominent cause of mortality, continue to be challenging conditions for patients, physicians, and researchers alike. CVDs comprise a wide range of illnesses affecting the heart, blood vessels, and the blood that flows through and between them. Advances in nanomedicine, a discipline focused on improving patient outcomes through revolutionary treatments, imaging agents, and ex vivo diagnostics, have created enthusiasm for overcoming limitations in CVDs' therapeutic and diagnostic landscapes. Nanomedicine can be involved in clinical purposes for CVD through the augmentation of cardiac or heart-related biomaterials, which can be functionally, mechanically, immunologically, and electrically improved by incorporating nanomaterials; vasculature applications, which involve systemically injected nanotherapeutics and imaging nanodiagnostics, nano-enabled biomaterials, or tissue-nanoengineered solutions; and enhancement of sensitivity and/or specificity of ex vivo diagnostic devices for patient samples. Therefore, this review discusses the latest studies based on applying organic nanoparticles in cardiovascular illness, including drug-conjugated polymers, lipid nanoparticles, and micelles. Following the revised information, it can be concluded that organic nanoparticles may be the most appropriate type of treatment for cardiovascular diseases due to their biocompatibility and capacity to integrate various drugs.

Injectable and Conductive Nanomicelle Hydrogel with α-Tocopherol Encapsulation for Enhanced Myocardial Infarction Repair

Substantial advancements have been achieved in the realm of cardiac tissue repair utilizing functional hydrogel materials. Additionally, drug-loaded hydrogels have emerged as a research hotspot for modulating adverse microenvironments and preventing left ventricular remodeling after myocardial infarction (MI), thereby fostering improved reparative outcomes. In this study, diacrylated Pluronic F127 micelles were used as macro-cross-linkers for the hydrogel, and the hydrophobic drug α-tocopherol (α-TOH) was loaded. Through the in situ synthesis of polydopamine (PDA) and the incorporation of conductive components, an injectable and highly compliant antioxidant/conductive composite FPDA hydrogel was constructed. The hydrogel exhibited exceptional stretchability, high toughness, good conductivity, cell affinity, and tissue adhesion. In a rabbit model, the material was surgically implanted onto the myocardial tissue, subsequent to the ligation of the left anterior descending coronary artery. Four weeks postimplantation, there was discernible functional recovery, manifesting as augmented fractional shortening and ejection fraction, alongside reduced infarcted areas. The findings of this investigation underscore the substantial utility of FPDA hydrogels given their proactive capacity to modulate the post-MI infarct microenvironment and thereby enhance the therapeutic outcomes of myocardial infarction.

Hydrogel-based cardiac repair and regeneration function in the treatment of myocardial infarction

A life-threatening illness that poses a serious threat to human health is myocardial infarction. It may result in a significant number of myocardial cells dying, dilated left ventricles, dysfunctional heart function, and ultimately cardiac failure. Based on the development of emerging biomaterials and the lack of clinical treatment methods and cardiac donors for myocardial infarction, hydrogels with good compatibility have been gradually applied to the treatment of myocardial infarction. Specifically, based on the three processes of pathophysiology of myocardial infarction, we summarized various types of hydrogels designed for myocardial tissue engineering in recent years, including natural hydrogels, intelligent hydrogels, growth factors, stem cells, and microRNA-loaded hydrogels. In addition, we also describe the heart patch and preparation techniques that promote the repair of MI heart function. Although most of these hydrogels are still in the preclinical research stage and lack of clinical trials, they have great potential for further application in the future. It is expected that this review will improve our knowledge of and offer fresh approaches to treating myocardial infarction.

Exploring Cutting-Edge Approaches to Potentiate Mesenchymal Stem Cell and Exosome Therapy for Myocardial Infarction

Cardiovascular diseases (CVDs) continue to be a significant global health concern. Many studies have reported promising outcomes from using MSCs and their secreted exosomes in managing various cardiovascular-related diseases like myocardial infarction (MI). MSCs and exosomes have demonstrated considerable potential in promoting regeneration and neovascularization, as well as exerting beneficial effects against apoptosis, remodeling, and inflammation in cases of myocardial infarction. Nonetheless, ensuring the durability and effectiveness of MSCs and exosomes following in vivo transplantation remains a significant concern. Recently, novel methods have emerged to improve their effectiveness and robustness, such as employing preconditioning statuses, modifying MSC and their exosomes, targeted drug delivery with exosomes, biomaterials, and combination therapy. Herein, we summarize the novel approaches that intensify the therapeutic application of MSC and their derived exosomes in treating MI.

Overview of Injectable Hydrogels for the Treatment of Myocardial Infarction

Myocardial infarction (MI) triggers adverse remodeling mechanisms, thus leading to heart failure. Since the application of biomaterial-based scaffolds emerged as a viable approach for providing mechanical support and promoting cell growth, injectable hydrogels have garnered substantial attention in MI treatment because of their minimally invasive administration through injection and diminished risk of infection. To fully understand the interplay between injectable hydrogels and infarcted myocardium repair, this review provides an overview of recent advances in injectable hydrogel-mediated MI therapy, including: I) material designs for repairing the infarcted myocardium, considering the pathophysiological mechanism of MI and design principles for biomaterials in MI treatment; II) the development of injectable functional hydrogels for MI treatment, including conductive, self-healing, drug-loaded, and stimulus-responsive hydrogels; and III) research progress in using injectable hydrogels to restore cardiac function in infarcted myocardium by promoting neovascularization, enhancing cardiomyocyte proliferation, decreasing myocardial fibrosis, and inhibiting excessive inflammation. Overall, this review presents the current state of injectable hydrogel research in MI treatment, offering valuable information to facilitate interdisciplinary knowledge transfer and enable the development of prognostic markers for suitable injectable materials.

In Situ Deposition of Drug and Gene Nanoparticles on a Patterned Supramolecular Hydrogel to Construct a Directionally Osteochondral Plug

The integrated repair of bone and cartilage boasts advantages for osteochondral restoration such as a long-term repair effect and less deterioration compared to repairing cartilage alone. Constructing multifactorial, spatially oriented scaffolds to stimulate osteochondral regeneration, has immense significance. Herein, targeted drugs, namely kartogenin@polydopamine (KGN@PDA) nanoparticles for cartilage repair and miRNA@calcium phosphate (miRNA@CaP) NPs for bone regeneration, were in situ deposited on a patterned supramolecular-assembled 2-ureido-4 [lH]-pyrimidinone (UPy) modified gelation hydrogel film, facilitated by the dynamic and responsive coordination and complexation of metal ions and their ligands. This hydrogel film can be rolled into a cylindrical plug, mimicking the Haversian canal structure of natural bone. The resultant hydrogel demonstrates stable mechanical properties, a self-healing ability, a high capability for reactive oxygen species capture, and controlled release of KGN and miR-26a. In vitro, KGN@PDA and miRNA@CaP promote chondrogenic and osteogenic differentiation of mesenchymal stem cells via the JNK/RUNX1 and GSK-3β/β-catenin pathways, respectively. In vivo, the osteochondral plug exhibits optimal subchondral bone and cartilage regeneration, evidenced by a significant increase in glycosaminoglycan and collagen accumulation in specific zones, along with the successful integration of neocartilage with subchondral bone. This biomaterial delivery approach represents a significant toward improved osteochondral repair.

Cardiac tissue engineering for myocardial infarction treatment

Myocardial infarction is one of the major causes of morbidity and mortality worldwide. Current treatments can relieve the symptoms of myocardial ischemia but cannot repair the necrotic myocardial tissue. Novel therapeutic strategies based on cellular therapy, extracellular vesicles, non-coding RNAs and growth factors have been designed to restore cardiac function while inducing cardiomyocyte cycle re-entry, ensuring angiogenesis and cardioprotection, and preventing ventricular remodeling. However, they face low stability, cell engraftment issues or enzymatic degradation in vivo, and it is thus essential to combine them with biomaterial-based delivery systems. Microcarriers, nanocarriers, cardiac patches and injectable hydrogels have yielded promising results in preclinical studies, some of which are currently being tested in clinical trials. In this review, we cover the recent advances made in cellular and acellular therapies used for cardiac repair after MI. We present current trends in cardiac tissue engineering related to the use of microcarriers, nanocarriers, cardiac patches and injectable hydrogels as biomaterial-based delivery systems for biologics. Finally, we discuss some of the most crucial aspects that should be addressed in order to advance towards the clinical translation of cardiac tissue engineering approaches.

Conductive Hydrogel Patches with High Elasticity and Fatigue Resistance for Cardiac Microenvironment Remodeling

Remodeling the conductive zone to assist normal myocardial contraction and relaxation during myocardial fibrosis has become the primary concern of myocardial infarction (MI) regeneration. Herein, we report an unbreakable and self-recoverable hyaluronic acid conductive cardiac patch for MI treatment, which can maintain structural integrity under mechanical load and integrate mechanical and electrical conduction and biological cues to restore cardiac electrical conduction and diastolic contraction function. Using the free carboxyl groups and aldehyde groups in the hydrogel system, excellent adhesion properties are achieved in the interface between the myocardial patch and the tissue, which can be closely integrated with the rabbit myocardial tissue, reducing the need for suture. Interestingly, the hydrogel patch exhibits sensitive conductivity (ΔR/R0 ≈ 2.5) for 100 cycles and mechanical stability for 500 continuous loading cycles without collapse, which allows the patch to withstand mechanical damage caused by sustained contraction and relaxation of the myocardial tissue. Moreover, considering the oxidative stress state caused by excessive ROS in the MI area, we incorporated Rg1 into the hydrogel to improve the abnormal myocardial microenvironment, which achieved more than 80% free radicalscavenging efficiency in the local infarcted region and promoted myocardial reconstruction. Overall, these Rg1-loaded conductive hydrogels with highly elastic fatigue resistance have great potential in restoring the abnormal electrical conduction pathway and promoting the myocardial microenvironment, thereby repairing the heart and improving the cardiac function.

Wet adhesive hydrogel cardiac patch loaded with anti-oxidative, autophagy-regulating molecule capsules and MSCs for restoring infarcted myocardium

Hydrogel patch-based stem cell transplantation and microenvironment-regulating drug delivery strategy is promising for the treatment of myocardial infarction (MI). However, the low retention of cells and drugs limits their therapeutic efficacies. Here, we propose a prefixed sponge carpet strategy, that is, aldehyde-dextran sponge (ODS) loading anti-oxidative/autophagy-regulating molecular capsules of 2-hydroxy-β-cyclodextrin@resveratrol (HP-β-CD@Res) is first bonded to the rat's heart via capillary removal of interfacial water from the tissue surface, and the subsequent Schiff base reaction between the aldehyde groups on ODS and amino groups on myocardium tissue. Then, an aqueous biocompatible hydrazided hyaluronic acid (HHA) solution encapsulating mesenchymal stem cells (MSCs) is impregnated into the anchored carpet to form HHA@ODS@HP-β-CD@Res hydrogel in situ via click reaction, thus prolonging the in vivo retention time of therapeutic drug and cells. Importantly, the HHA added to outer surface consumes the remaining aldehydes to contribute to nonsticky top surface, avoiding adhesion to other tissues. The embedded HP-β-CD@Res molecular capsules with antioxidant and autophagy regulation bioactivities can considerably improve cardiac microenvironment, reduce cardiomyocyte apoptosis, and enhance the survival of transplanted MSCs, thereby promoting cardiac repair by facilitating angiogenesis and reducing cardiac fibrosis.

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Developing a wet adhesive hydrogel cardiac patch through a prefixed sponge carpet strategy.

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2-Hydroxy-β-cyclodextrin@resveratrol molecular capsules improve myocardial microenvironment.

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Post-adding of MSCs into the prefixed sponge carpet prolongs the in vivo retention time.

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The hydrogel patch loading molecular capsules and MSCs restores cardiac functions.

Insight into Heart-Tailored Architectures of Hydrogel to Restore Cardiac Functions after Myocardial Infarction

With permanent heart muscle injury or death, myocardial infarction (MI) is complicated by inflammatory, proliferation and remodeling phases from both the early ischemic period and subsequent infarct expansion. Though in situ re-establishment of blood flow to the infarct zone and delays of the ventricular remodeling process are current treatment options of MI, they fail to address massive loss of viable cardiomyocytes while transplanting stem cells to regenerate heart is hindered by their poor retention in the infarct bed. Equipped with heart-specific mimicry and extracellular matrix (ECM)-like functionality on the network structure, hydrogels leveraging tissue-matching biomechanics and biocompatibility can mechanically constrain the infarct and act as localized transport of bioactive ingredients to refresh the dysfunctional heart under the constant cyclic stress. Given diverse characteristics of hydrogel including conductivity, anisotropy, adhesiveness, biodegradability, self-healing and mechanical properties driving local cardiac repair, we aim to investigate and conclude the dynamic balance between ordered architectures of hydrogels and the post-MI pathological milieu. Additionally, our review summarizes advantages of heart-tailored architectures of hydrogels in cardiac repair following MI. Finally, we propose challenges and prospects in clinical translation of hydrogels to draw theoretical guidance on cardiac repair and regeneration after MI.

Antibacterial Conductive UV-Blocking Adhesion Hydrogel Dressing with Mild On-Demand Removability Accelerated Drug-Resistant Bacteria-Infected Wound Healing

The on-demand replacement of multifunctional hydrogel wound dressings helps to avoid bacterial colonization, and the on-demand painless peeling of tissue adhesive hydrogels on the wound site remains a major challenge to be solved. In this work, we design and develop a series of multifunctional dynamic Schiff base network hydrogels composed of cystamine-modified hyaluronic acid, benzaldehyde-functionalized poly(ethylene glycol)-co-poly(glycerol sebacate), and polydopamine@polypyrrole nanocomposite (PDA@PPy) with mild on-demand removability to enhance drug-resistant bacteria-infected wound healing. These hydrogels exhibited ideal injectable and self-healing properties, excellent tissue adhesion, in vivo hemostasis, good antioxidation, and conductivity. PDA@PPy inspired by melanin endows hydrogels with excellent antioxidant capacity, UV-blocking ability, and photothermal anti-infection ability. Based on the dynamic oxidation-reduction response of disulfide bonds inspired by the dissociation of the tertiary spatial structure transformation of poly-polypeptide chains, these hydrogels can achieve rapid painless on-demand removal under mild conditions by adding dithiothreitol. These multifunctional hydrogels significantly promoted collagen deposition and angiogenesis in the MRSA-infected full-thickness skin repair experiment. All the results showed that these multifunctional hydrogels with painless on-demand removal property showed great potential in clinical treatment of infected wounds.

Combination wound healing using polymer entangled porous nanoadhesive hybrids with robust ROS scavenging and angiogenesis properties

Nanoadhesives can achieve tight wound closure by connecting biomacromolecules from both sides. However, previously developed adhesive systems suffered from suboptimal wound healing efficiency due to the lack of interparticle cohesion, sufficient reactive oxygen species (ROS)-scavenging sites, and angiogenesis consideration. Herein, we developed a polymer entangled porous nanoadhesive system to address the above challenge by synergy of three functional components. Firstly, hybrid mesoporous silica nanoparticles with highly integrated polydopamine (MS-PDA) were prepared by templated synthesis. The entangling between PVA polymer and MS-PDA contributed to much stronger cohesion between nanoparticles, which led to 75% larger adhesion strength. As confirmed by in vitro and in vivo evaluations, the highly exposed catechol groups boosted the scavenging activity of ROS (1.8-4.1 fold enhancement as compared with nonporous counterpart). Consequently, more macrophages exhibited anti-inflammatory phenotype, leading to 2-2.6 fold lower pro-inflammatory cytokine levels. Moreover, the sustained release of bioactive SiO₄^4- by the disintegration of nanoparticles contributed to ∼3-fold higher expression of VEGF and enhanced new blood vessel formation, as well as better wound repair. This platform can provide a new paradigm for developing multifunctional nanoadhesive systems in treating skin wounds. STATEMENT OF SIGNIFICANCE: PVA polymer entangled mesoporous nanoadhesives of polydopamine (PDA)/silica hybrids with the combination of excellent wound closure effect, boosted ROS-scavenging activity, and significant angiogenesis ability were developed for improving the suboptimal skin wound healing efficiency. This strategy not only greatly advances our ability to rationally integrate repairing elements in nanoadhesives for manipulating combined processes of interfacial events during wound healing, but also offers general implications toward application of polymers to reinforce the adhesion strength in nanoadhesive systems. In addition, our findings on the impacts of pore effects mediated ROS species conversion and polymer entanglement may also trigger great interests and facilitate the development/broad application of therapeutic adhesives.

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.

Responsive Hydrogels Based on Triggered Click Reactions for Liver Cancer

Globally, liver cancer, which is one of the major cancers worldwide, has attracted the growing attention of technological researchers for its high mortality and limited treatment options. Hydrogels are soft 3D network materials containing a large number of hydrophilic monomers. By adding moieties such as nitrobenzyl groups to the network structure of a cross-linked nanocomposite hydrogel, the click reaction improves drug-release efficiency in vivo, which improves the survival rate and prolongs the survival time of liver cancer patients. The application of a nanocomposite hydrogel drug delivery system can not only enrich the drug concentration at the tumor site for a long time but also effectively prevents the distant metastasis of residual tumor cells. At present, a large number of researches have been working toward the construction of responsive nanocomposite hydrogel drug delivery systems, but there are few comprehensive articles to systematically summarize these discoveries. Here, this systematic review summarizes the synthesis methods and related applications of nanocomposite responsive hydrogels with actions to external or internal physiological stimuli. With different physical or chemical stimuli, the structural unit rearrangement and the controlled release of drugs can be used for responsive drug delivery in different states.

Research Advances of Injectable Functional Hydrogel Materials in the Treatment of Myocardial Infarction

Myocardial infarction (MI) has become one of the serious diseases threatening human life and health. However, traditional treatment methods for MI have some limitations, such as irreversible myocardial necrosis and cardiac dysfunction. Fortunately, recent endeavors have shown that hydrogel materials can effectively prevent negative remodeling of the heart and improve the heart function and long-term prognosis of patients with MI due to their good biocompatibility, mechanical properties, and electrical conductivity. Therefore, this review aims to summarize the research progress of injectable hydrogel in the treatment of MI in recent years and to introduce the rational design of injectable hydrogels in myocardial repair. Finally, the potential challenges and perspectives of injectable hydrogel in this field will be discussed, in order to provide theoretical guidance for the development of new and effective treatment strategies for MI.

Tregs biomimetic nanoparticle to reprogram inflammatory and redox microenvironment in infarct tissue to treat myocardial ischemia reperfusion injury in mice

Background

At present, patients with myocardial infarction remain an increased risk for myocardial ischemia/reperfusion injury (MI/RI). There lacks effectively method to treat MI/RI in clinic. For the treatment of MI/RI, it is still a bottleneck to effectively deliver drug to ischemic myocardium. In this paper, a regulatory T cells (Tregs) biomimetic nanoparticle (CsA@PPTK) was prepared by camouflaging nanoparticle with platelet membrane.

Results

CsA@PPTK actively accumulated in ischemic myocardium of MI/RI mice. CsA@PPTK significantly scavenged reactive oxygen species (ROS) and increased the generation of Tregs and the ratio of M2 type macrophage to M1 type macrophage in ischemic myocardium. Moreover, CsA@PPTK significantly attenuated apoptosis of cardiomyocytes and reduced the infarct size and fibrosis area in ischemic myocardium. CsA@PPTK markedly decreased the protein expression of MMP-9 and increased the protein expression of CX43 in ischemic myocardium tissue. Subsequently, the remodeling of the left ventricle was significant alleviated, and heart function of MI/RI mice was markedly improved.

Conclusion

CsA@PPTK showed significant therapeutic effect on MI/RI, and it has great potential application in the treatment of MI/RI.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01445-2.

Nano-traditional Chinese medicine: a promising strategy and its recent advances

Traditional Chinese Medicine (TCM) has been applied to the prevention and treatment of numerous diseases and has an irreplaceable role in rehabilitation and health care. However, the application of TCMs is drastically limited by their defects, such as single administration, poor water solubility, low bioavailability, and weak targeting capability. Recently, nanoparticles have been extensively used in resolving pharmaceutical obstacles in consideration of their large specific surface area, strong targeting capability, good sustained-release effect, etc. In this review, we first describe the limitations of TCM ingredients and two significant forms of nanotechnology applied in TCM, nanometerization of TCMs and nano-drug delivery systems for TCMs. Then, we discuss the preparation methods of nanometerization: mechanical crushing, spray drying, and high-pressure homogenization, which have been utilized to conquer the various weaknesses of TCMs. Then, recent advances in nano-drug delivery systems for TCM ingredients are discussed, including lipid-based nanocarriers, polymeric nanoparticles, inorganic nanocarriers, hybrid nanoparticles, and TCM self-assembled nanoparticles. Finally, the future challenges and perspectives of TCM formula complexity and the limitations of nanocarriers are also discussed. Better understanding the function of nanotechnology in TCM will help to modernize Chinese medicine and broaden the application of nano-TCM in the clinic.

Recent Advances in KEAP1/NRF2-Targeting Strategies by Phytochemical Antioxidants, Nanoparticles, and Biocompatible Scaffolds for the Treatment of Diabetic Cardiovascular Complications

Significance: Modulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated antioxidant response is a key aspect in the onset of diabetes-related cardiovascular complications. With this review, we provide an overview of the recent advances made in the development of Nrf2-targeting strategies for the treatment of diabetes, with particular attention toward the activation of Nrf2 by natural antioxidant compounds, nanoparticles, and oxidative stress-modulating biocompatible scaffolds. Recent Advances: In the past 30 years, studies addressing the use of antioxidant therapies to treat diabetes have grown exponentially, showing promising but yet inconclusive results. Animal studies and clinical trials on the Nrf2 pathway have shown promising results, suggesting that its activation can delay or reverse some of the cardiovascular impairments in diabetes. Critical Issues: Hyperglycemia- and oscillating glucose levels-induced reactive oxygen species (ROS) accumulation is progressively emerging as a central factor in the onset and progression of diabetes-related cardiovascular complications, including endothelial dysfunction, retinopathy, heart failure, stroke, critical limb ischemia, ulcers, and delayed wound healing. In this context, accumulating evidence suggests a central role for Nrf2-mediated antioxidant response, one of the most studied cellular defensive mechanisms against ROS accumulation. Future Directions: Innovative approaches such as tissue engineering and nanotechnology are converging toward targeting oxidative stress in diabetes. Antioxid. Redox Signal. 36, 707-728.

Advances in the stimuli-responsive injectable hydrogel for controlled release of drugs

The stimuli-responsiveness of injectable hydrogel has been drastically developed for the controlled release of drugs and achieved encouraging curative effects in a variety of diseases including wounds, cardiovascular diseases and tumors. The gelation, swelling and degradation of such hydrogels respond to endogenous biochemical factors (such as pH, reactive oxygen species, glutathione, enzymes, glucose) and/or to exogenous physical stimulations (like light, magnetism, electricity and ultrasound), thereby accurately releasing loaded drugs in response to specifically pathological status and as desired for treatment plan and thus improving therapeutic efficacy effectively. In this paper, we give a detailed introduction of recent progresses in responsive injectable hydrogels and focus on the design strategy of various stimuli-sensitivities and their resultant alteration of gel dissociation and drug liberation behaviour. Their application in disease treatment is also discussed. This article is protected by copyright. All rights reserved.

Nanoparticles Targeting the Molecular Pathways of Heart Remodeling and Regeneration

Cardiovascular diseases are the main cause of death worldwide, a trend that will continue to grow over the next decade. The heart consists of a complex cellular network based mainly on cardiomyocytes, but also on endothelial cells, smooth muscle cells, fibroblasts, and pericytes, which closely communicate through paracrine factors and direct contact. These interactions serve as valuable targets in understanding the phenomenon of heart remodeling and regeneration. The advances in nanomedicine in the controlled delivery of active pharmacological agents are remarkable and may provide substantial contribution to the treatment of heart diseases. This review aims to summarize the main mechanisms involved in cardiac remodeling and regeneration and how they have been applied in nanomedicine.

Polymeric nanoparticles in the diagnosis and treatment of myocardial infarction: Challenges and future prospects

Myocardial infarction (MI) is the leading cause of morbidity and mortality worldwide. Despite extensive efforts to provide early diagnosis and adequate treatment regimens, detection of MI still faces major limitations and pathological MI complications continue to threaten the recovery of survivors. Polymeric nanoparticles (NPs) represent novel noninvasive drug delivery systems for the diagnosis and treatment of MI and subsequent prevention of fatal heart failure. In this review, we cover the recent advances in polymeric NP-based diagnostic and therapeutic approaches for MI and their application as multifunctional theranostic tools. We also discuss the in vivo behavior and toxicity profile of polymeric NPs, their application in noninvasive imaging, passive, and active drug delivery, and use in cardiac regenerative therapy. We conclude with the challenges faced with polymeric nanosystems and suggest future efforts needed for clinical translation.

Reactive Oxygen Species-Based Biomaterials for Regenerative Medicine and Tissue Engineering Applications

Reactive oxygen species (ROS), acting as essential mediators in biological system, play important roles in the physiologic and pathologic processes, including cellular signal transductions and cell homeostasis interference. Aberrant expression of ROS in tissue microenvironment can be caused by the internal/external stimuli and tissue injury, which may leads to an elevated level of oxidative stress, inflammatory response, and cellular damage as well as disruption in the tissue repair process. To prevent the formation of excess ROS around the injury site, advanced biomaterials can be remodeled or instructed to release their payloads in an injury microenvironment-responsive fashion to regulate the elevated levels of the ROS, which may also help downregulate the oxidative stress and promote tissue regeneration. A multitude of scaffolds and bioactive cues have been reported to promote the regeneration of damaged tissues based on the scavenging of free radicals and reactive species that confer high protection to the cellular activity and tissue function. In this review, we outline the underlying mechanism of ROS generation in the tissue microenvironment and present a comprehensive review of ROS-scavenging biomaterials for regenerative medicine and tissue engineering applications, including soft tissues regeneration, bone and cartilage repair as well as wound healing. Additionally, we highlight the strategies for the regulation of ROS by scaffold design and processing technology. Taken together, developing ROS-based biomaterials may not only help develop advanced platforms for improving injury microenvironment but also accelerate tissue regeneration.

ROS-Scavenging Therapeutic Hydrogels for Modulation of the Inflammatory Response

Although reactive oxygen species (ROS) are essential for cellular processes, excessive ROS could be a major cause of various inflammatory diseases because of the oxidation of proteins, DNA, and membrane lipids. It has recently been suggested that the amount of ROS could thus be regulated to treat such physiological disorders. A ROS-scavenging hydrogel is a promising candidate for therapeutic applications because of its high biocompatibility, 3D matrix, and ability to be modified. Approaches to conferring antioxidant properties to normal hydrogels include embedding ROS-scavenging catalytic nanoparticles, modifying hydrogel polymer chains with ROS-adsorbing organic moieties, and incorporating ROS-labile linkers in polymer backbones. Such therapeutic hydrogels can be used for wound healing, cardiovascular diseases, bone repair, ocular diseases, and neurodegenerative disorders. ROS-scavenging hydrogels could eliminate oxidative stress, accelerate the regeneration process, and show synergetic effects with other drugs or therapeutic molecules. In this review, the mechanisms by which ROS are generated and scavenged in the body are outlined, and the effects of high levels of ROS and the resulting oxidative stress on inflammatory diseases are described. Next, the mechanism of ROS scavenging by hydrogels is explained depending on the ROS-scavenging agents embedded within the hydrogel. Lastly, the recent achievements in the development of ROS-scavenging hydrogels to treat various inflammation-associated diseases are presented.

Polydopamine nanoparticles attenuate retina ganglion cell degeneration and restore visual function after optic nerve injury

Background

Oxidative stress contributes to retina ganglion cells (RGCs) loss in variety of ocular diseases, including ocular trauma, ocular vein occlusion, and glaucoma. Scavenging the excessed reactive oxygen species (ROS) in retinal neurovascular unit could be beneficial to RGCs survival. In this study, a polydopamine (PDA)-based nanoplatform is developed to protect RGCs.

Results

The PDA nanoparticles efficiently eliminate multi-types of ROS, protect endothelia and neuronal cells from oxidative damage, and inhibit microglia activation in retinas. In an optic nerve crush (ONC) model, single intravitreal injection of PDA nanoparticles could significantly attenuate RGCs loss via eliminating ROS in retinas, reducing the inflammatory response and maintaining barrier function of retinal vascular endothelia. Comparative transcriptome analysis of the retina implied that PDA nanoparticles improve RGCs survival probably by altering the expression of genes involved in inflammation and ROS production. Importantly, as a versatile drug carrier, PDA nanoparticles could deliver brimonidine (a neuroprotection drug) to synergistically attenuate RGCs loss and promote axon regeneration, thus restore visual function.

Conclusions

The PDA nanoparticle-based therapeutic nanoplatform displayed excellent performance in ROS elimination, providing a promising probability for treating retinal degeneration diseases.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01199-3.

Restoring Cardiac Functions after Myocardial Infarction-Ischemia/Reperfusion via an Exosome Anchoring Conductive Hydrogel

Both myocardial infarction (MI) and the follow-up reperfusion will lead to an inevitable injury to myocardial tissues, such as cardiac dysfunctions, fibrosis, and reduction of intercellular cell-to-cell interactions. Recently, exosomes (Exo) derived from stem cells have demonstrated a robust capability to promote angiogenesis and tissue repair. However, the short half-life of Exo and rapid clearance lead to insufficient therapeutic doses in the lesion area. Herein, an injectable conductive hydrogel is constructed to bind Exo derived from human umbilical cord mesenchymal stem cells to treat myocardial injuries after myocardial infarction-ischemia/reperfusion (MI-I/R). To this end, a hyperbranched epoxy macromer (EHBPE) grafted by an aniline tetramer (AT) was synthesized to cross-link thiolated hyaluronic acid (HA-SH) and thiolated Exo anchoring a CP05 peptide via an epoxy/thiol "click" reaction. The resulting Gel@Exo composite system possesses multiple features, such as controllable gelation kinetics, shear-thinning injectability, conductivity matching the native myocardium, soft and dynamic stability adapting to heartbeats, and excellent cytocompatibility. After being injected into injured hearts of rats, the hydrogel effectively prolongs the retention of Exo in the ischemic myocardium. The cardiac functions have been considerably improved by Gel@Exo administration, as indicated by the enhancing ejection fraction and fractional shortening, and reducing fibrosis area. Immunofluorescence staining and reverse transcription-polymerase chain reaction (RT-PCR) results demonstrate that the expression of cardiac-related proteins (Cx43, Ki67, CD31, and α-SMA) and genes (VEGF-A, VEGF-B, vWF, TGF-β1, MMP-9, and Serca2a) are remarkably upregulated. The conductive Gel@Exo system can significantly improve cell-to-cell interactions, promote cell proliferation and angiogenesis, and result in a prominent therapeutic effect on MI-I/R, providing a promising therapeutic method for injured myocardial tissues.

Therapeutic Acellular Scaffolds for Limiting Left Ventricular Remodelling-Current Status and Future Directions

Myocardial infarction (MI) is one of the leading causes of heart-related deaths worldwide. Following MI, the hypoxic microenvironment triggers apoptosis, disrupts the extracellular matrix and forms a non-functional scar that leads towards adverse left ventricular (LV) remodelling. If left untreated this eventually leads to heart failure. Besides extensive advancement in medical therapy, complete functional recovery is never accomplished, as the heart possesses limited regenerative ability. In recent decades, the focus has shifted towards tissue engineering and regenerative strategies that provide an attractive option to improve cardiac regeneration, limit adverse LV remodelling and restore function in an infarcted heart. Acellular scaffolds possess attractive features that have made them a promising therapeutic candidate. Their application in infarcted areas has been shown to improve LV remodelling and enhance functional recovery in post-MI hearts. This review will summarise the updates on acellular scaffolds developed and tested in pre-clinical and clinical scenarios in the past five years with a focus on their ability to overcome damage caused by MI. It will also describe how acellular scaffolds alone or in combination with biomolecules have been employed for MI treatment. A better understanding of acellular scaffolds potentialities may guide the development of customised and optimised therapeutic strategies for MI treatment.

Remodeling the periodontitis microenvironment for osteogenesis by using a reactive oxygen species-cleavable nanoplatform

Modestly removing the excessive reactive oxygen species (ROS) plays a crucial role in regulating the microenvironment of periodontitis and provides favorable conditions for osteogenesis. However, the current strategy for scavenging ROS is not controllable, substantially limiting the outcomes in periodontitis. Herein, we introduced a controllable ROS-scavenging nanoplatform by encasing N-acetylcysteine (NAC, (a well-known ROS scavenger) into tailor-made ROS-cleavable amphiphilic polymer nanoparticles (PEG-ss-PCL NPs) as an intracellular delivery carrier. The existing ROS in the inflammatory microenvironment facilitated polymer degradation via breakage of thioketal bonds, and then led to encapsulated NAC release. NAC eliminated all ROS induced by lipopolysaccharide (LPS), while PssL-NAC adjusted the ROS level slightly higher than that of the control group. The percentage of apoptotic cells cultured with NAC and PssL-NAC decreased observably compared with that of cells cultured with 10 µg/ml LPS. The microenvironment regulated by PssL-NAC was highly suitable for osteogenic differentiation based on PCR and Western blot results, which showed higher expression levels of BMP2, Runx2, and PKA. Analysis of ALP activity and Alizarin red S staining showed consistent results. Additionally, the injection of PssL-NAC into the periodontitis area could alleviate the tissue destruction induced by ligation of the maxillary second molar. PssL-NAC showed a better ability to decrease osteoclast activity and inflammation, consequently improving the restoration of destroyed tissue. Our study suggests that ROS-responsive polymer nanoparticles loaded with NAC (PssL-NAC) can be new promising materials for the treatment of periodontitis. STATEMENT OF SIGNIFICANCE: More and more studies indicate that periodontal tissue damage is closely related to the high reactive oxygen species (ROS) environment. Excessive ROS will aggravate periodontal tissue damage and is not conducive to tissue repair. However, as an essential signal molecule in human physiological activities, ROS absence is also useless for tissue repair. In this study, we proposed to improve ROS imbalance in the environment of periodontitis as a strategy to promote periodontal regeneration and successfully synthesized a smart drug-releasing nanoplatform that can respond to ROS. Besides, we validated its ability to regulate the ROS environment and promote osteogenesis through experimental data in vivo and in vitro.

Nanoparticles: Promising Tools for the Treatment and Prevention of Myocardial Infarction

Despite several recent advances, current therapy and prevention strategies for myocardial infarction are far from satisfactory, owing to limitations in their applicability and treatment effects. Nanoparticles (NPs) enable the targeted and stable delivery of therapeutic compounds, enhance tissue engineering processes, and regulate the behaviour of transplants such as stem cells. Thus, NPs may be more effective than other mechanisms, and may minimize potential adverse effects. This review provides evidence for the view that function-oriented systems are more practical than traditional material-based systems; it also summarizes the latest advances in NP-based strategies for the treatment and prevention of myocardial infarction.

Natural Melanin/Alginate Hydrogels Achieve Cardiac Repair through ROS Scavenging and Macrophage Polarization

The efficacy of cardiac regenerative strategies for myocardial infarction (MI) treatment is greatly limited by the cardiac microenvironment. The combination of reactive oxygen species (ROS) scavenging to suppress the oxidative stress damage and macrophage polarization to regenerative M2 phenotype in the MI microenvironment can be desirable for MI treatment. Herein, melanin nanoparticles (MNPs)/alginate (Alg) hydrogels composed of two marine-derived natural biomaterials, MNPs obtained from cuttlefish ink and alginate extracted from ocean algae, are proposed. Taking advantage of the antioxidant property of MNPs and mechanical support from injectable alginate hydrogels, the MNPs/Alg hydrogel is explored for cardiac repair by regulating the MI microenvironment. The MNPs/Alg hydrogel is found to eliminate ROS against oxidative stress injury of cardiomyocytes. More interestingly, the macrophage polarization to regenerative M2 macrophages can be greatly promoted in the presence of MNPs/Alg hydrogel. An MI rat model is utilized to evaluate the feasibility of the as-prepared MNPs/Alg hydrogel for cardiac repair in vivo. The antioxidant, anti-inflammatory, and proangiogenesis effects of the hydrogel are investigated in detail. The present study opens up a new way to utilize natural biomaterials for MI treatment and allows to rerecognize the great value of natural biomaterials in cardiac repair.

Antioxidative and Angiogenic Hyaluronic Acid-Based Hydrogel for the Treatment of Peripheral Artery Disease

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by blockages of the arteries supplying the lower extremities. Ischemia initiates oxidative damage and mitochondrial dysfunction in the legs of PAD patients, causing injury to the tissues of the leg, significant decline in walking performance, leg pain while walking, and in the most severe cases, nonhealing ulcers and gangrene. Current clinical trials based on cells/stem cells, the trophic factor, or gene therapy systems have shown some promising results for the treatment of PAD. Biomaterial matrices have been explored in animal models of PAD to enhance these therapies. However, current biomaterial approaches have not fully met the essential requirements for minimally invasive intramuscular delivery to the leg. Ideally, a biomaterial should present properties to ameliorate oxidative stress/damage and failure of angiogenesis. Recently, we have created a thermosensitive hyaluronic acid (HA) hydrogel with antioxidant capacity and skeletal muscle-matching stiffness. Here, we further optimized HA hydrogels with the cell adhesion peptide RGD to facilitate the development of vascular-like structures in vitro. The optimized HA hydrogel reduced intracellular reactive oxygen species levels and preserved vascular-like structures against H₂O₂-induced damage in vitro. HA hydrogels also provided prolonged release of the vascular endothelial growth factor (VEGF). After injection into rat ischemic hindlimb muscles, this VEGF-releasing hydrogel reduced lipid oxidation, regulated oxidative-related genes, enhanced local blood flow in the muscle, and improved running capacity of the treated rats. Our HA hydrogel system holds great potential for the treatment of the ischemic legs of patients with PAD.