Myocardial-Infarction-Responsive Smart Hydrogels Targeting Matrix Metalloproteinase for On-Demand Growth Factor Delivery

Salvaging myocardial infarction with nanoenzyme-loaded hydrogels: Targeted scavenging of mitochondrial reactive oxygen species

Myocardial infarction resulting from coronary artery atherosclerosis is the leading cause of heart failure, which represents a significant global health burden. The limitations of conventional pharmacologic thrombolysis and flow reperfusion procedures highlight the urgent need for new therapeutic strategies to effectively treat myocardial infarction. In this study, we present a novel biomimetic approach that integrates polyphenols and metal nanoenzymes, inspired by the structure of pomegranates. We developed tannic acid-coated Mn-Co3O4 (MCT) nanoparticles in combination with an injectable collagen hydrogel for the effective treatment of myocardial infarction. The hydrogel enhanced the infarct microenvironment, while the slow-released MCT targets mitochondria to inhibit the post-infarction surge of reactive oxygen species, providing anti-apoptotic and anti-inflammatory effects. RNA sequencing revealed the potential of hydrogels to serve as an interventional mechanism during the post-infarction inflammatory phase. Notably, we found that the hydrogel, when combined with the nanopomegranate-based therapy, significantly improves adverse ventricular remodeling and restores cardiac function in early infarction management. The MCT hydrogel leverages the unique benefits of both MCT nanopomegranates and collagen, demonstrating a synergistic effect. This approach provides a promising example of the potential cooperation between nanomimetic structures and natural biomaterials in therapeutic applications.

Sequential Targeted Enzyme-Instructed Self-Assembly Supramolecular Nanofibers to Attenuate Intervertebral Disc Degeneration

As an age-related disease, intervertebral disc degeneration is closely related to inflammation and aging. Inflammatory cytokines and cellular senescence collectively contribute to the degradation of intervertebral disc. Blocking this synergy reduces disc extracellular matrix damage caused by inflammation and aging. In this study, drug-loaded nanofibers with sequential targeting functions are constructed through intelligent response, hydrophilicity, and in situ self-assembly empowerment of flurbiprofen. The peptide precursor responds to the cleavage of overexpressed MMP-2 in the degenerative intervertebral disc microenvironment (intracellular and extracellular), resulting in the formation of self-assembled nanofibers that enable the on-demand release of flurbiprofen and COX-2 response. In vitro, Comp. 1 (Flurbiprofen-GFFYPLGLAGEEEERGD) reduces the expression of inflammation-related genes and proteins and the polarization of M1 macrophages by competitively inhibiting COX-2 and increases the expression of extracellular matrix proteins COL-2 and aggrecan. Additionally, it can reduce the expression of Senescence-Associated Secretory Phenotype and DNA damage in aged nucleus pulposus cells and promote the recovery of proliferation and cell cycle. In vivo, drug-loaded nanofibers delay intervertebral disc degeneration by inhibiting inflammation and preventing the accumulation of senescent cells. Therefore, the sequentially targeted self-assembled drug-loaded nanofibers can delay intervertebral disc degeneration by blocking the synergistic effect of inflammatory cytokines and cellular senescence.

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.

Advances in Functionalized Hydrogels in the Treatment of Myocardial Infarction and Drug-Delivery Strategies

Myocardial infarction (MI) is a serious cardiovascular disease with high morbidity and mortality rates, posing a significant threat to patient's health and quality of life. Following a MI, the damaged myocardial tissue is typically not fully repaired, leading to permanent impairment of myocardial function. While traditional treatments can alleviate symptoms and reduce pain, their ability to repair damaged heart muscle tissue is limited. Functionalized hydrogels, a broad category of materials with diverse functionalities, can enhance the properties of hydrogels to cater to the needs of tissue engineering, drug delivery, medical dressings, and other applications. Recently, functionalized hydrogels have emerged as a promising new therapeutic approach for the treatment of MI. Functionalized hydrogels possess outstanding biocompatibility, customizable mechanical properties, and drug-release capabilities. These properties enable them to offer scaffold support, drug release, and tissue regeneration promotion, making them a promising approach for treating MI. This paper aims to evaluate the advancements and delivery methods of functionalized hydrogels for treating MI, while also discussing their potential and the challenges they may pose for future clinical use.

Application of Pro-angiogenic Biomaterials in Myocardial Infarction

Biomaterials have potential applications in the treatment of myocardial infarction (MI). These biomaterials have the ability to mechanically support the ventricular wall and to modulate the inflammatory, metabolic, and local electrophysiological microenvironment. In addition, they can play an equally important role in promoting angiogenesis, which is the primary prerequisite for the treatment of MI. A variety of biomaterials are known to exert pro-angiogenic effects, but the pro-angiogenic mechanisms and functions of different biomaterials are complex and diverse, and have not yet been systematically described. This review will focus on the pro-angiogenesis of biomaterials and systematically describe the mechanisms and functions of different biomaterials in promoting angiogenesis in MI.

Borate bonds-containing pH-responsive chitosan hydrogel for postoperative tumor recurrence and wound infection prevention

Chitosan has been widely used in biomedical fields due to its good antibacterial properties, excellent biocompatibility, and biodegradability. In this study, a pH-responsive and self-healing hydrogel was synthesized from 3-carboxyphenylboronic acid grafted with chitosan (CS-BA) and polyvinyl alcohol (PVA). The dynamic boronic ester bonds and intermolecular hydrogen bonds are responsible for the hydrogel formation. By changing the mass ratio of CS-BA and PVA, the tensile stress and compressive stress of hydrogel can controlled in the range of 0.61 kPa - 0.74 kPa and 295.28 kPa - 1108.1 kPa, respectively. After doping with tannic acid (TA)/iron nanocomplex (TAFe), the hydrogel successful killed tumor cells through the near infrared laser-induced photothermal conversion and the TAFe-triggered reactive oxygen species generation. Moreover, the photothermal conversion of the hydrogel and the antibacterial effect of CS and TA give the hydrogel a good antibacterial effect. The CS-BA/PVA/TAFe hydrogel exhibit good in vivo and in vitro anti-tumor recurrence and antibacterial ability, and therefore has the potential to be used as a powerful tool for the prevention of local tumor recurrence and bacterial infection after surgery.

Injectable Self-Oxygenating Cardio-Protective and Tissue Adhesive Silk-Based Hydrogel for Alleviating Ischemia After Mi Injury

Myocardial infarction (MI) is a significant cardiovascular disease that restricts blood flow, resulting in massive cell death and leading to stiff and noncontractile fibrotic scar tissue formation. Recently, sustained oxygen release in the MI area has shown regeneration ability; however, improving its therapeutic efficiency for regenerative medicine remains challenging. Here, a combinatorial strategy for cardiac repair by developing cardioprotective and oxygenating hybrid hydrogels that locally sustain the release of stromal cell-derived factor-1 alpha (SDF) and oxygen for simultaneous activation of neovascularization at the infarct area is presented. A sustained release of oxygen and SDF from injectable, mechanically robust, and tissue-adhesive silk-based hybrid hydrogels is achieved. Enhanced endothelialization under normoxia and anoxia is observed. Furthermore, there is a marked improvement in vascularization that leads to an increment in cardiomyocyte survival by ≈30% and a reduction of the fibrotic scar formation in an MI animal rodent model. Improved left ventricular systolic and diastolic functions by ≈10% and 20%, respectively, with a ≈25% higher ejection fraction on day 7 are also observed. Therefore, local delivery of therapeutic oxygenating and cardioprotective hydrogels demonstrates beneficial effects on cardiac functional recovery for reparative therapy.

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.

Electrically Conductive Collagen-PEDOT:PSS Hydrogel Prevents Post-Infarct Cardiac Arrhythmia and Supports hiPSC-Cardiomyocyte Function

Myocardial infarction (MI) causes cell death, disrupts electrical activity, triggers arrhythmia, and results in heart failure, whereby 50-60% of MI-associated deaths manifest as sudden cardiac deaths (SCD). The most effective therapy for SCD prevention is implantable cardioverter defibrillators (ICDs). However, ICDs contribute to adverse remodeling and disease progression and do not prevent arrhythmia. This work develops an injectable collagen-PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) hydrogel that protects infarcted hearts against ventricular tachycardia (VT) and can be combined with human induced pluripotent stem cell (hiPSC)-cardiomyocytes to promote partial cardiac remuscularization. PEDOT:PSS improves collagen gel formation, micromorphology, and conductivity. hiPSC-cardiomyocytes in collagen-PEDOT:PSS hydrogels exhibit near-adult sarcomeric length, improved contractility, enhanced calcium handling, and conduction velocity. RNA-sequencing data indicate enhanced maturation and improved cell-matrix interactions. Injecting collagen-PEDOT:PSS hydrogels in infarcted mouse hearts decreases VT to the levels of healthy hearts. Collectively, collagen-PEDOT:PSS hydrogels offer a versatile platform for treating cardiac injuries.

Design and evaluation of an MMP-9-responsive hydrogel for vital pulp therapy

OBJECTIVE

To design and evaluate a matrix metalloproteinase 9 (MMP-9)-responsive hydrogel for vital pulp therapy.

METHODS

A peptide linker with optimized sensitivity toward MMP-9 was crosslinked with 4-arm poly (ethylene glycol)-norbornene (PEG-NB) by thiol-norbornene photo-polymerization. This resulted in the formation of a hydrogel network in which the peptide IDR-1002 was incorporated. Hydrogel characterization and gelation kinetics were examined with Fourier-transform infrared spectroscopy, scanning electron microscopy, rheological testing, and swelling evaluation. Hydrogel degradation was examined through multiple exposure to pre-activated MMP-9, to simulate flare-ups of dental pulp inflammation. The IDR-1002 released from degraded hydrogels was measured with high-performance liquid chromatography. Effect of IDR-1002 released from hydrogels on one-week-old multispecies oral biofilms was evaluated using confocal laser scanning microscopy.

RESULTS

MMP-9-responsive, injectable, and photo-crosslinkable hydrogels were successfully synthesized. When hydrogel degradation and release of IDR-1002 were examined with exposure to pre-activated MMP-9, IDR-1002 release was significantly correlated with elevated levels of MMP-9 (p < 0.05). The effectiveness of IDR-1002 in killing bacteria in multispecies oral biofilms was significantly enhanced when the hydrogels were immersed in 10 nM or 20 nM pre-activated MMP-9, compared to immersion in phosphate-buffered saline (p < 0.05).

CONCLUSIONS

The MMP-9-responsive hydrogel is a promising candidate for on-demand delivery of bioactive agent in vital pulp therapy.

CLINICAL SIGNIFICANCE

MMP-9 is one of the most important diagnostic and prognostic biomarkers for pulpitis. An MMP-9-responsive hydrogel has potential to be used as an in-situ on-demand release system for the diagnosis and treatment of dental pulp inflammation.

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.

Comparative effectiveness of myocardial patches and intramyocardial injections in treating myocardial infarction with a MitoQ/hydrogel system

In cardiac tissue engineering, myocardial surface patches and hydrogel intramyocardial injections represent the two primary hydrogel-based strategies for myocardial infarction (MI) treatment. However, the comparative effectiveness of these two treatments remains uncertain. Therefore, this study aimed to compare the effects of the two treatment modalities by designing a simple and reproducible hydrogel cross-linked with γ-PGA and 4-arm-PEG-SG. To improve mitochondrial damage in cardiomyocytes (CMs) during early MI, we incorporated the mitochondria-targeting antioxidant MitoQ into the hydrogel network. The hydrogel exhibited excellent biodegradability, biocompatibility, adhesion, and injectability in vitro. The hydrogel was utilized for rat MI treatment through both patch adhesion and intramyocardial injections. In vivo results demonstrated that the slow release of MitoQ peptide from the hydrogel hindered ROS production in CM, alleviated mitochondrial damage, and enhanced CM activity within 7 days, effectively inhibiting MI progression. Both hydrogel intramyocardial injections and patches exhibited positive therapeutic effects, with intramyocardial injections demonstrating superior efficacy in terms of cardiac function and structure in equivalent treatment cycles. In conclusion, we developed a MitoQ/hydrogel system that is easily prepared and can serve as both a myocardial patch and an intramyocardial injection for MI treatment, showing significant potential for clinical applications.

A cigarette filter-derived biomimetic cardiac niche for myocardial infarction repair

Cell implantation offers an appealing avenue for heart repair after myocardial infarction (MI). Nevertheless, the implanted cells are subjected to the aberrant myocardial niche, which inhibits cell survival and maturation, posing significant challenges to the ultimate therapeutic outcome. The functional cardiac patches (CPs) have been proved to construct an elastic conductive, antioxidative, and angiogenic microenvironment for rectifying the aberrant microenvironment of the infarcted myocardium. More importantly, inducing implanted cardiomyocytes (CMs) adapted to the anisotropic arrangement of myocardial tissue by bioengineered structural cues within CPs are more conducive to MI repair. Herein, a functional Cig/(TA-Cu) CP served as biomimetic cardiac niche was fabricated based on structural anisotropic cigarette filter by modifying with tannic acid (TA)-chelated Cu2+ (TA-Cu complex) via a green method. This CP possessed microstructural anisotropy, electrical conductivity and mechanical properties similar to natural myocardium, which could promote elongation, orientation, maturation, and functionalization of CMs. Besides, the Cig/(TA-Cu) CP could efficiently scavenge reactive oxygen species, reduce CM apoptosis, ultimately facilitating myocardial electrical integration, promoting vascular regeneration and improving cardiac function. Together, our study introduces a functional CP that integrates multimodal cues to create a biomimetic cardiac niche and provides an effective strategy for cardiac repair.

The Combination of Bioactive Herbal Compounds with Biomaterials for Regenerative Medicine

Regenerative medicine aims to restore the function of diseased or damaged tissues and organs by cell therapy, gene therapy, and tissue engineering, along with the adjunctive application of bioactive molecules. Traditional bioactive molecules, such as growth factors and cytokines, have shown great potential in the regulation of cellular and tissue behavior, but have the disadvantages of limited source, high cost, short half-life, and side effects. In recent years, herbal compounds extracted from natural plants/herbs have gained increasing attention. This is not only because herbal compounds are easily obtained, inexpensive, mostly safe, and reliable, but also owing to their excellent effects, including anti-inflammatory, antibacterial, antioxidative, proangiogenic behavior and ability to promote stem cell differentiation. Such effects also play important roles in the processes related to tissue regeneration. Furthermore, the moieties of the herbal compounds can form physical or chemical bonds with the scaffolds, which contributes to improved mechanical strength and stability of the scaffolds. Thus, the incorporation of herbal compounds as bioactive molecules in biomaterials is a promising direction for future regenerative medicine applications. Herein, an overview on the use of bioactive herbal compounds combined with different biomaterial scaffolds for regenerative medicine application is presented. We first introduce the classification, structures, and properties of different herbal bioactive components and then provide a comprehensive survey on the use of bioactive herbal compounds to engineer scaffolds for tissue repair/regeneration of skin, cartilage, bone, neural, and heart tissues. Finally, we highlight the challenges and prospects for the future development of herbal scaffolds toward clinical translation. Overall, it is believed that the combination of bioactive herbal compounds with biomaterials could be a promising perspective for the next generation of regenerative medicine.

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.

Hydrogels for Cardio and Vascular Tissue Repair and Regeneration

Cardiovascular disease (CVD), the leading cause of death globally, affects the heart and arteries with a variety of clinical manifestations, the most dramatic of which are myocardial infarction (MI), abdominal aortic aneurysm (AAA), and intracranial aneurysm (IA) rupture. In MI, necrosis of the myocardium, scar formation, and loss of cardiomyocytes result from insufficient blood supply due to coronary artery occlusion. Beyond stenosis, the arteries that are structurally and functionally connected to the cardiac tissue can undergo pathological dilation, i.e., aneurysmal dilation, with high risk of rupture. Aneurysms of the intracranial arteries (IAs) are more commonly seen in young adults, whereas those of the abdominal aorta (AAA) are predominantly seen in the elderly. IAs, unpredictably, can undergo rupture and cause life-threatening hemorrhage, while AAAs can result in rupture, internal bleeding and high mortality rate. In this clinical context, hydrogels, three-dimensional networks of water-seizing polymers, have emerged as promising biomaterials for cardiovascular tissue repair or protection due to their biocompatibility, tunable properties, and ability to encapsulate and release bioactive molecules. This review provides an overview of the current state of research on the use of hydrogels as an innovative platform to promote cardiovascular-specific tissue repair in MI and functional recovery or protection in aneurysmal dilation.

Smart Hydrogels for Tissue Regeneration

The rapid growth in the portion of the aging population has led to a consequent increase in demand for biomedical hydrogels, together with an assortment of challenges that need to be overcome in this field. Smart hydrogels can autonomously sense and respond to the physiological/pathological changes of the tissue microenvironment and continuously adapt the response according to the dynamic spatiotemporal shifts in conditions. This along with other favorable properties, make smart hydrogels excellent materials for employing toward improving the precision of treatment for age-related diseases. The key factor during the smart hydrogel design is on accurately identifying the characteristics of natural tissues and faithfully replicating the composition, structure, and biological functions of these tissues at the molecular level. Such hydrogels can accurately sense distinct physiological and external factors such as temperature and biologically active molecules, so they may in turn actively and promptly adjust their response, by regulating their own biological effects, thereby promoting damaged tissue repair. This review summarizes the design strategies employed in the creation of smart hydrogels, their response mechanisms, as well as their applications in field of tissue engineering; and concludes by briefly discussing the relevant challenges and future prospects.

Highly Sensitive Labeling, Clickable Functionalization, and Glycoengineering of the MUC1 Neighboring System

This study introduces a novel wash-type affinity-primed proximity labeling (WAPL) strategy for labeling and surface engineering of the MUC1 protein neighboring system. The strategy entails the utilization of peroxidase in conjunction with a MUC1-selective aptamer, facilitating targeted binding to MUC1 and inducing covalent labeling of the protein neighboring system. This study reveals a novel finding that the WAPL strategy demonstrates superior labeling efficiency in comparison to nonwash-type affinity-primed proximity labeling, marking the first instance of such observations. The WAPL strategy provides signal amplification by converting a single recognition event into multiple covalent labeling events, thereby improving the detection sensitivity for subtle changes in MUC1. The WAPL platform employs two levels of labeling upgrades, modifying the biotin handles of the conventional labeling substrate, biotin-phenol. The first level involves a range of clickable molecules, facilitating dibenzoazacyclooctynylation, alkynylation, and trans-cyclooctenylation of the protein neighboring system. The second level utilizes lactose as a post-translational modification model, enabling rapid and reliable glycoengineering of the MUC1 neighboring system while remaining compatible with cell-based assays. The implementation of the WAPL strategy in protein neighboring systems has resulted in the establishment of a versatile platform that can effectively facilitate diverse monitoring and regulation techniques. This platform offers valuable insights into the regulation of relevant signaling pathways and promotes the advancement of novel therapeutic approaches, thereby bringing substantial implications for human health.

Injectable hydrogel-based combination therapy for myocardial infarction: a systematic review and Meta-analysis of preclinical trials

INTRODUCTION

This study evaluates the effectiveness of a combined regimen involving injectable hydrogels for the treatment of experimental myocardial infarction.

PATIENT CONCERNS

Myocardial infarction is an acute illness that negatively affects quality of life and increases mortality rates. Experimental models of myocardial infarction can aid in disease research by allowing for the development of therapies that effectively manage disease progression and promote tissue repair.

DIAGNOSIS

Experimental animal models of myocardial infarction were established using the ligation method on the anterior descending branch of the left coronary artery (LAD).

INTERVENTIONS

The efficacy of intracardiac injection of hydrogels, combined with cells, drugs, cytokines, extracellular vesicles, or nucleic acid therapies, was evaluated to assess the functional and morphological improvements in the post-infarction heart achieved through the combined hydrogel regimen.

OUTCOMES

A literature review was conducted using PubMed, Web of Science, Scopus, and Cochrane databases. A total of 83 papers, including studies on 1332 experimental animals (rats, mice, rabbits, sheep, and pigs), were included in the meta-analysis based on the inclusion and exclusion criteria. The overall effect size observed in the group receiving combined hydrogel therapy, compared to the group receiving hydrogel treatment alone, resulted in an ejection fraction (EF) improvement of 8.87% [95% confidence interval (CI): 7.53, 10.21] and a fractional shortening (FS) improvement of 6.31% [95% CI: 5.94, 6.67] in rat models, while in mice models, the improvements were 16.45% [95% CI: 11.29, 21.61] for EF and 5.68% [95% CI: 5.15, 6.22] for FS. The most significant improvements in EF (rats: MD = 9.63% [95% CI: 4.02, 15.23]; mice: MD = 23.93% [95% CI: 17.52, 30.84]) and FS (rats: MD = 8.55% [95% CI: 2.54, 14.56]; mice: MD = 5.68% [95% CI: 5.15, 6.22]) were observed when extracellular vesicle therapy was used. Although there have been significant results in large animal experiments, the number of studies conducted in this area is limited.

CONCLUSION

The present study demonstrates that combining hydrogel with other therapies effectively improves heart function and morphology. Further preclinical research using large animal models is necessary for additional study and validation.

Stimuli-responsive peptide hydrogels for biomedical applications

Stimuli-responsive hydrogels can respond to external stimuli with a change in the network structure and thus have potential application in drug release, intelligent sensing, and scaffold construction. Peptides possess robust supramolecular self-assembly ability, enabling spontaneous formation of nanostructures through supramolecular interactions and subsequently hydrogels. Therefore, peptide-based stimuli-responsive hydrogels have been widely explored as smart soft materials for biomedical applications in the last decade. Herein, we present a review article on design strategies and research progress of peptide hydrogels as stimuli-responsive materials in the field of biomedicine. The latest design and development of peptide hydrogels with responsive behaviors to stimuli are first presented. The following part provides a systematic overview of the functions and applications of stimuli-responsive peptide hydrogels in tissue engineering, drug delivery, wound healing, antimicrobial treatment, 3D cell culture, biosensors, etc. Finally, the remaining challenges and future prospects of stimuli-responsive peptide hydrogels are proposed. It is believed that this review will contribute to the rational design and development of stimuli-responsive peptide hydrogels toward biomedical applications.

Hydrogel-Based Growth Factor Delivery Platforms: Strategies and Recent Advances

Growth factors play a crucial role in regulating a broad variety of biological processes and are regarded as powerful therapeutic agents in tissue engineering and regenerative medicine in the past decades. However, their application is limited by their short half-lives and potential side effects in physiological environments. Hydrogels are identified as having the promising potential to prolong the half-lives of growth factors and mitigate their adverse effects by restricting them within the matrix to reduce their rapid proteolysis, burst release, and unwanted diffusion. This review discusses recent progress in the development of growth factor-containing hydrogels for various biomedical applications, including wound healing, brain tissue repair, cartilage and bone regeneration, and spinal cord injury repair. In addition, the review introduces strategies for optimizing growth factor release including affinity-based delivery, carrier-assisted delivery, stimuli-responsive delivery, spatial structure-based delivery, and cellular system-based delivery. Finally, the review presents current limitations and future research directions for growth factor-delivering hydrogels.

Hydrogels for the Treatment of Myocardial Infarction: Design and Therapeutic Strategies

Cardiovascular diseases (CVDs) have become the leading global burden of diseases in recent years and are the primary cause of human mortality and loss of healthy life expectancy. Myocardial infarction (MI) is the top cause of CVDs-related deaths, and its incidence is increasing worldwide every year. Recently, hydrogels have garnered great interest from researchers as a promising therapeutic option for cardiac tissue repair after MI. This is due to their excellent properties, including biocompatibility, mechanical properties, injectable properties, anti-inflammatory properties, antioxidant properties, angiogenic properties, and conductive properties. This review discusses the advantages of hydrogels as a novel treatment for cardiac tissue repair after MI. The design strategies of various hydrogels in MI treatment are then summarized, and the latest research progress in the field is classified. Finally, the future perspectives of this booming field are also discussed at the end of this review.

Bioresponsive Cytokine Delivery Responding to Matrix Metalloproteinases

Cytokines are regulated in acute and chronic inflammation, including rheumatoid arthritis (RA) and myocardial infarction (MI). However, the dynamic windows within which cytokine activity/inhibition is desirable in RA and MI change timely and locally during the disease. Therefore, traditional, static delivery regimens are unlikely to meet the idiosyncrasy of these highly dynamic pathophysiological and individual processes. Responsive delivery systems and biomaterials, sensing surrogate markers of inflammation (i.e., matrix metalloproteinases - MMPs) and answering with drug release, may present drug activity at the right time, manner, and place. This article discusses MMPs as surrogate markers for disease activity in RA and MI to clock drug discharge to MMP concentration profiles from MMP-responsive drug delivery systems and biomaterials.

Chemo-immunotherapy by dual-enzyme responsive peptide self-assembling abolish melanoma

Herein, we designed Comp. 1 to simultaneously respond to two enzymes: alkaline phosphatase and matrix metalloproteinase 2, which is commonly found in highly malignant cancer cell lines containing B16-F10 murine melanoma cells and CT26 murine colon carcinoma cells. We used the regional differences in the expression levels of dual-markers to accurately release immune molecule IND into tumor microenvironment for the activation of anti-tumor related immune effects, while in-situ self-assembly occurs. The dual-enzyme response process can further regulate the peptide precursors' self-assembly in the form of short rod-shaped nanofibers, enabling the delivery of the loaded chemotherapeutic drug HCPT into the cancer cells and further allowing the peptide assemblies to escape from lysosomes and return to cytoplasm in the form of tiny nanoparticles to induce apoptosis of cancer cells. This process does not occur in the single-positive breast cancer cell line MCF-7 or the normal hepatocytes cell line LO2, indicating the selectivity of the cancer cells exhibited using our strategy. In vivo studies revealed that Comp. 1 can effectively cooperate with chemotherapy to enhance the immunotherapy effect and induce immune responses associated with elevated pro-inflammatory cytokines in vivo to inhibit malignant tumors growth. Our dual-enzyme responsive chemo-immunotherapy strategy feasible in anti-tumor treatment, provides a new avenue for regulating peptide self-assembly to adapt to diverse tumor properties and may eventually be used for the development of novel multifunctional anti-tumor nanomedicines.

Enhanced protection against hypoxia/reoxygenation-induced apoptosis in H9c2 cells by puerarin-loaded liposomes modified with matrix metalloproteinases-targeting peptide and triphenylphosphonium

Based on the inhibition of mitochondrial permeability transition pore (mPTP) opening, puerarin (PUE) has a good potential to reduce myocardial ischemia/reperfusion injury (MI/RI). However, the lack of targeting of free PUE makes it difficult to reach the mitochondria. In this paper, we constructed matrix metalloproteinase-targeting peptide (MMP-TP) and triphenylphosphonium (TPP) cation co-modified liposomes loaded with PUE (PUE@T/M-L) for mitochondria-targeted drug delivery. PUE@T/M-L had a favorable particle size of 144.9 ± 0.8 nm, an encapsulation efficiency of 78.9 ± 0.6%, and a sustained-release behavior. The results of cytofluorimetric experiments showed that MMP-TP and TPP double-modified liposomes (T/M-L) enhanced intracellular uptake, escaped lysosomal capture, and promoted drug targeting into mitochondria. In addition, PUE@T/M-L enhanced the viability of hypoxia-reoxygenation (H/R) injured H9c2 cells by inhibiting mPTP opening and reactive oxygen species (ROS) production, reducing Bax expression and increasing Bcl-2 expression. It was inferred that PUE@T/M-L delivered PUE into the mitochondria of H/R injured H9c2 cells, resulting in a significant increase in cellular potency. Based on the ability of MMP-TP to bind the elevated expression of matrix metalloproteinases (MMPs), T/M-L had excellent tropism for Lipopolysaccharide (LPS) -stimulated macrophages and can significantly reduce TNF-α and ROS levels, thus allowing both drug accumulation in ischemic cardiomyocytes and reducing inflammatory stimulation during MI/RI. Fluorescence imaging results of the targeting effect using a DiR probe also indicated that DiR@T/M-L could accumulate and retain in the ischemic myocardium. Taken together, these results demonstrated the promising application of PUE@T/M-L for mitochondria-targeted drug delivery to achieve maximum therapeutic efficacy of PUE.

Versatile Biodegradable Poly(acrylic acid)-Based Hydrogels Infiltrated in Porous Titanium Implants to Improve the Biofunctional Performance

This research work proposes a synergistic approach to improve implants' performance through the use of porous Ti substrates to reduce the mismatch between Young's modulus of Ti (around 110 GPa) and the cortical bone (20-25 GPa), and the application of a biodegradable, acrylic acid-based polymeric coating to reduce bacterial adhesion and proliferation, and to enhance osseointegration. First, porous commercially pure Ti substrates with different porosities and pore size distributions were fabricated by using space-holder techniques to obtain substrates with improved tribomechanical behavior. On the other hand, a new diacrylate cross-linker containing a reduction-sensitive disulfide bond was synthesized to prepare biodegradable poly(acrylic acid)-based hydrogels with 1, 2, and 4% cross-linker. Finally, after the required characterization, both strategies were implemented, and the combination of 4% cross-linked poly(acrylic acid)-based hydrogel infiltrated in 30 vol % porosity, 100-200 μm average pore size, was revealed as an outstanding choice for enhancing implant performance.

3D Chiral Self-Assembling Matrixes for Regulating Polarization of Macrophages and Enhance Repair of Myocardial Infarction

The regulation of inflammatory response at the site of injury and macrophage immunotherapy is critical for tissue repair. Chiral self-assemblies are one of the most ubiquitous life cues, which is closely related to biological functions, life processes, and even the pathogenesis of diseases. However, the role of supramolecular chiral self-assemblies in the regulation of immune functions in the internal environment of tissues has not been fully explored yet. Herein, 3D supramolecular chiral self-assembling matrixes are prepared to regulate the polarization of macrophages and further enhance the repair of myocardial infarction (MI). Experiments studies show that M-type (left-handed) self-assembling matrixes significantly inhibit inflammation and promote damaged myocardium repair by upregulating M2 macrophage polarization and downstream immune signaling compared with P-type (right-handed), and R-type (non-chirality) self-assembling matrixes. Classical molecular dynamics (MD) simulation demonstrates that M-type self-assembling matrixes display higher stereo-affinity to cellular binding, which enhances the clustering of mechanosensitive integrin β1 (Itgβ1) and activates focal adhesion kinase (FAK) and Rho-associated protein kinase (ROCK), as well as downstream PI3K/Akt1/mTOR signaling axes to promote M2 polarization. This study of designing a 3D chiral self-assembling matrixes microenvironment suitable for regulating the polarization of macrophages will provide devise basis for immunotherapy with biomimetic materials.

Smart stimuli-responsive drug delivery systems in spotlight of COVID-19

The world has been dealing with a novel severe acute respiratory syndrome (SARS-CoV-2) since the end of 2019, which threatens the lives of many people worldwide. COVID-19 causes respiratory infection with different symptoms, from sneezing and coughing to pneumonia and sometimes gastric symptoms. Researchers worldwide are actively developing novel drug delivery systems (DDSs), such as stimuli-responsive DDSs. The ability of these carriers to respond to external/internal and even multiple stimuli is essential in creating "smart" DDS that can effectively control dosage, sustained release, individual variations, and targeted delivery. To conduct a comprehensive literature survey for this article, the terms "Stimuli-responsive", "COVID-19″ and "Drug delivery" were searched on databases/search engines like "Google Scholar", "NCBI", "PubMed", and "Science Direct". Many different types of DDSs have been proposed, including those responsive to various exogenous (light, heat, ultrasound and magnetic field) or endogenous (microenvironmental changes in pH, ROS and enzymes) stimuli. Despite significant progress in DDS research, several challenging issues must be addressed to fill the gaps in the literature. Therefore, this study reviews the drug release mechanisms and applications of endogenous/exogenous stimuli-responsive DDSs while also exploring their potential with respect to COVID-19.

Simplified α2-macroglobulin as a TNF-α inhibitor for inflammation alleviation in osteoarthritis and myocardial infarction therapy

Tumor necrosis factor α (TNF-α) is a leading proinflammatory cytokine as the master regulator of inflammation in chronic inflammation diseases. Although TNF-α antagonists such as small molecules and peptides are in development, comparable effectiveness in TNF-α neutralization is hardly achieved only with TNF-α capture. In this study, simplified α2-macroglobulin (SM) as a novel TNF-α inhibitor was fabricated to relieve inflammation response by TNF-α capture and internalization with lysosomal degradation. SM was prepared by conjugating a TNF-α-targeting peptide with a receptor binding domain (RBD) derived from α2-macroglobulin through a synthetic biology strategy. SM exhibited effective capture and bioactivity inhibition of TNF-α. Improved endocytosis of TNF-α into lysosomes was observed with SM in macrophages. Even challenged with LPS/IFNγ, the macrophages showed relieved inflammation response with SM treatment. When administrated in chronic inflammation injury in vivo, SM achieved comparable therapeutic efficacy with Infliximab, showing ameliorated cartilage degeneration with relieved inflammation in osteoarthritis (OA) and preserved cardiac function with mitigated myocardium injury in myocardial infarction (MI). These results suggest that SM functioning in TNF-α capture-internalization mechanism might be promising therapeutic alternatives of TNF-α antibodies.

Individually Tailored Modular "Egg" Hydrogels Capable of Spatiotemporally Controlled Drug Release for Spinal Cord Injury Repair

Controllable drug delivery systems (DDS) can overcome the disadvantages of conventional drug administration processes, such as high dosages or repeated administration. Herein, a smart DDS collagen hydrogel is deployed for spinal cord injury (SCI) repair based on modular designing of "egg" nanoparticles (NPs) that ingeniously accomplish controlled drug release via inducing a signaling cascade in response to external and internal stimuli. The "egg" NPs consist of a three-layered structure: tannic acid/Fe3+ /tetradecanol "eggshell," zeolitic imidazolate framework-8 (ZIF-8) "egg white," and paclitaxel "yolk." Then NPs served as a crosslinking epicenter, blending with collagen solutions to generate functional hydrogels. Remarkably, the "eggshell" efficiently converts near-infrared (NIR) irradiation into heat. Subsequently, tetradecanol can be triggered to disintegrate via heat, exposing the structure of ZIF-8. The Zn-imidazolium ion coordination bond of the "egg white" is susceptible to cleaving at the acidic SCI site, decomposing the skeleton to release paclitaxel on demand. As expected, the paclitaxel release rate upon NIR irradiation increased up to threefold on the seventh day, which matches endogenous neural stem/progenitor cell migration process. Taken together, the collagen hydrogels facilitate the neurogenesis and motor function recovery, demonstrating a revolutionary strategy for spatiotemporally controlled drug release and providing guidelines for the design of DDS.

In situ photo-crosslinked hydrogel promotes oral mucosal wound healing through sustained delivery of ginsenoside Rg1

Oral mucosal wounds exhibit an increased susceptibility to inflammation as a consequence of their direct exposure to a diverse range of microorganisms. This causes pain, slow healing, and other complications that interfere with patients' daily activities like eating and speaking. Consequently, patients experience a significant decline in their overall quality of life. Therefore, the pursuit of novel treatment approaches is of great importance. In this study, ginsenoside Rg1, a natural active substance extracted from ginseng root, was chosen as a therapeutic agent. It was encapsulated in a screened photo-crosslinked hydrogel scaffold for the treatment of mucosal defects in the rat palate. The results demonstrated that Rg1-hydrogel possessed excellent physical and chemical properties, and that oral mucosa wounds treated with Rg1-hydrogel exhibited the greatest healing performance, as evidenced by more pronounced wound re-epithelialization, increased collagen deposition, and decreased inflammatory infiltration. Subsequent investigations in molecular biology confirmed that Rg1-hydrogel stimulated the secretion of repair-related factors and inhibited the secretion of inflammatory factors. This study demonstrated that the hydrogel containing ginsenoside Rg1 significantly promotes oral mucosal tissue healing in vivo. Based on the findings, it can be inferred that the Rg1-hydrogel has promising prospects for the therapeutic management of oral mucosal wounds.

The effect of GelDex-S58 hydrogel on anti-conjunctival scarring after glaucoma filtration surgery

Excessive scarring is the main cause of surgical failure in glaucoma filtration surgery. S58 has been shown to have an excellent antifibrotic effect but its duration of action is not sufficient to achieve the desired antiscarring effect. In this study, a light-cured bioadhesive hydrogel composed of GelMA and oxidized dextran (ODex), namely, GelDex, was used to load S58 (GelDex-S58). The microscopic morphology of GelDex-S58 appeared to be a porous structure with good slow-release properties and suitable degradation time. Cell Counting Kit-8, cell scratch and transwell assays showed that GelDex-S58 significantly reduced TGF-β-induced fibroblast proliferation, increased migration and invasion ability. In in vivo studies, GelDex-S58 treatment prolonged follicular retention, reduced mean intraocular pressure, and significantly reduced collagen deposition and α-SMA expression levels in the conjunctival tissue compared to treatment with S58 alone. In conclusion, GelDex-S58 could reduce scar formation after glaucoma filtration surgery.

Application of locally responsive design of biomaterials based on microenvironmental changes in myocardial infarction

Morbidity and mortality caused by acute myocardial infarction (AMI) are on the rise, posing a grave threat to the health of the general population. Up to now, interventional, surgical, and pharmaceutical therapies have been the main treatment methods for AMI. Effective and timely reperfusion therapy decreases mortality, but it cannot stimulate myocardial cell regeneration or reverse ventricular remodeling. Cell therapy, gene therapy, immunotherapy, anti-inflammatory therapy, and several other techniques are utilized by researchers to improve patients' prognosis. In recent years, biomaterials for AMI therapy have become a hot spot in medical care. Biomaterials furnish a microenvironment conducive to cell growth and deliver therapeutic factors that stimulate cell regeneration and differentiation. Biomaterials adapt to the complex microenvironment and respond to changes in local physical and biochemical conditions. Therefore, environmental factors and material properties must be taken into account when designing biomaterials for the treatment of AMI. This article will review the factors that need to be fully considered in the design of biological materials.

Angiogenesis induction as a key step in cardiac tissue Regeneration: From angiogenic agents to biomaterials

Cardiovascular diseases are the leading cause of death worldwide. After myocardial infarction, the vascular supply of the heart is damaged or blocked, leading to the formation of scar tissue, followed by several cardiac dysfunctions or even death. In this regard, induction of angiogenesis is considered as a vital process for supplying nutrients and oxygen to the cells in cardiac tissue engineering. The current review aims to summarize different approaches of angiogenesis induction for effective cardiac tissue repair. Accordingly, a comprehensive classification of induction of pro-angiogenic signaling pathways through using engineered biomaterials, drugs, angiogenic factors, as well as combinatorial approaches is introduced as a potential platform for cardiac regeneration application. The angiogenic induction for cardiac repair can enhance patient treatment outcomes and generate economic prospects for the biomedical industry. The development and commercialization of angiogenesis methods often involves collaboration between academic institutions, research organizations, and biomedical companies.

Therapeutic Applications of Garlic and Turmeric for the Diabetic Wound Healing in Mice

Diabetes is involved in delayed wound healing that can be cured by natural products such as garlic, turmeric, and fibroin extracts. Alloxan monohydrate is used for inducing diabetes in mice. The percent wound contraction of garlic (150 mg/ml), turmeric (100 mg/ml), and fibroin (50 mg/ml), individually and in combinations garlic (150 mg/ml) + fibroin (50 mg/ml), turmeric (100 mg/ml) + fibroin (50 mg/ml), garlic (150 mg/ml) + turmeric (100 mg/ml), and garlic (150 mg/ml) + turmeric (100 mg/ml) + fibroin (50 mg/ml) was checked by evaluating the healing time, % wound contraction and histological analysis. The serum level of MMPs (MMP 2, MMP7, MMP 9), pro-inflammatory cytokines (TNF-α, IL-6, IL-8), and TIMPs were evaluated. With the combination of three extracts (Ga+Tu+Fi) garlic (150 mg/ml), turmeric (100 mg/ml) and fibroin (50 mg/ml), wounds healed in 12 days and had 97.3 ± 2.2% wound contraction. While the positive control (polyfax) and diabetic control (saline) wounds healed in 17- and 19-days with wound contraction of 96.7 ± 1.4% and 96.3 ± 1.1%, respectively. Histological analysis showed that the combination of Ga+Tu+Fi exhibited an increase in the growth of collagen fibers, fibroblasts number, and keratinocytes, and lessened inflammation of blood vessels. The combination of Ga+Tu+Fi significantly alleviated the serum concentration of TNF-α (14.2 ± 0.7 pg/ml), IL-6 (10.0 ± 1.0 pg/ml), IL-8 (16.0 ± 1.5 pg/ml), MMP2 (228.0 ± 18.1 pg/ml), MMP7 (271.0 ± 9.9 pg/ml), and MMP9 (141.0 ± 5.3 pg/ml) to diabetic control. The level of TIMPs (193.0 ± 9.1 pg/ml) was increased significantly with respect to diabetic control. We conclude that the combination of these biomaterials possessed high regenerative and healing capabilities and can be an effective remedy in the healing of chronic wounds in diabetic patients.

Stimuli-responsive hydrogels: smart state of-the-art platforms for cardiac tissue engineering

Biomedicine and tissue regeneration have made significant advancements recently, positively affecting the whole healthcare spectrum. This opened the way for them to develop their applications for revitalizing damaged tissues. Thus, their functionality will be restored. Cardiac tissue engineering (CTE) using curative procedures that combine biomolecules, biomimetic scaffolds, and cells plays a critical part in this path. Stimuli-responsive hydrogels (SRHs) are excellent three-dimensional (3D) biomaterials for tissue engineering (TE) and various biomedical applications. They can mimic the intrinsic tissues' physicochemical, mechanical, and biological characteristics in a variety of ways. They also provide for 3D setup, adequate aqueous conditions, and the mechanical consistency required for cell development. Furthermore, they function as competent delivery platforms for various biomolecules. Many natural and synthetic polymers were used to fabricate these intelligent platforms with innovative enhanced features and specialized capabilities that are appropriate for CTE applications. In the present review, different strategies employed for CTE were outlined. The light was shed on the limitations of the use of conventional hydrogels in CTE. Moreover, diverse types of SRHs, their characteristics, assembly and exploitation for CTE were discussed. To summarize, recent development in the construction of SRHs increases their potential to operate as intelligent, sophisticated systems in the reconstruction of degenerated cardiac tissues.

Cardiac-Adaptive Conductive Hydrogel Patch Enabling Construction of Mechanical-Electrical Anisotropic Microenvironment for Heart Repair

The biomimetic construction of a microstructural-mechanical-electrical anisotropic microenvironment adaptive to the native cardiac tissue is essential to repair myocardial infarction (MI). Inspired by the 3D anisotropic characteristic of the natural fish swim bladder (FSB), a novel flexible, anisotropic, and conductive hydrogel was developed for tissue-specific adaptation to the anisotropic structural, conductive, and mechanical features of the native cardiac extracellular matrix. The results revealed that the originally stiff, homogeneous FSB film was tailored to a highly flexible anisotropic hydrogel, enabling its potential as a functional engineered cardiac patch (ECP). In vitro and in vivo experiments demonstrated the enhanced electrophysiological activity, maturation, elongation, and orientation of cardiomyocytes (CMs), and marked MI repair performance with reduced CM apoptosis and myocardial fibrosis, thereby promoting cell retention, myogenesis, and vascularization, as well as improving electrical integration. Our findings offer a potential strategy for functional ECP and provides a novel strategy to bionically simulate the complex cardiac repair environment.

Chitin nanocrystal-assisted 3D bioprinting of gelatin methacrylate scaffolds

In recent years, there has been an increasing focus on the application of hydrogels in tissue engineering. The integration of 3D bioprinting technology has expanded the potential applications of hydrogels. However, few commercially available hydrogels used for 3D biological printing exhibit both excellent biocompatibility and mechanical properties. Gelatin methacrylate (GelMA) has good biocompatibility and is widely used in 3D bioprinting. However, its low mechanical properties limit its use as a standalone bioink for 3D bioprinting. In this work, we designed a biomaterial ink composed of GelMA and chitin nanocrystal (ChiNC). We explored fundamental printing properties of composite bioinks, including rheological properties, porosity, equilibrium swelling rate, mechanical properties, biocompatibility, effects on the secretion of angiogenic factors and fidelity of 3D bioprinting. The results showed that adding 1% (w/v) ChiNC to 10% (w/v) GelMA improved the mechanical properties and printability of the GelMA hydrogels, promoted cell adhesion, proliferation and vascularization and enabled the printing of complex 3D scaffolds. This strategy of incorporating ChiNC to enhance the performance of GelMA biomaterials could potentially be applied to other biomaterials, thereby expanding the range of materials available for use. Furthermore, in combination with 3D bioprinting technology, this approach could be leveraged to bioprint scaffolds with complex structures, further broadening the potential applications in tissue engineering.

Therapeutic angiogenesis based on injectable hydrogel for protein delivery in ischemic heart disease

Ischemic heart disease (IHD) remains the leading cause of death and disability worldwide and leads to myocardial necrosis and negative myocardial remodeling, ultimately leading to heart failure. Current treatments include drug therapy, interventional therapy, and surgery. However, some patients with severe diffuse coronary artery disease, complex coronary artery anatomy, and other reasons are unsuitable for these treatments. Therapeutic angiogenesis stimulates the growth of the original blood vessels by using exogenous growth factors to generate more new blood vessels, which provides a new treatment for IHD. However, direct injection of these growth factors can cause a short half-life and serious side effects owing to systemic spread. Therefore, to overcome this problem, hydrogels have been developed for temporally and spatially controlled delivery of single or multiple growth factors to mimic the process of angiogenesis in vivo. This paper reviews the mechanism of angiogenesis, some important bioactive molecules, and natural and synthetic hydrogels currently being applied for bioactive molecule delivery to treat IHD. Furthermore, the current challenges of therapeutic angiogenesis in IHD and its potential solutions are discussed to facilitate real translation into clinical applications in the future.

Effect of biomaterial stiffness on cardiac mechanics in a biventricular infarcted rat heart model with microstructural representation of in situ intramyocardial injectate

Intramyocardial delivery of biomaterials is a promising concept for treating myocardial infarction. The delivered biomaterial provides mechanical support and attenuates wall thinning and elevated wall stress in the infarct region. This study aimed at developing a biventricular finite element model of an infarcted rat heart with a microstructural representation of an in situ biomaterial injectate, and a parametric investigation of the effect of the injectate stiffness on the cardiac mechanics. A three-dimensional subject-specific biventricular finite element model of a rat heart with left ventricular infarct and microstructurally dispersed biomaterial delivered 1 week after infarct induction was developed from ex vivo microcomputed tomography data. The volumetric mesh density varied between 303 mm-3 in the myocardium and 3852 mm-3 in the injectate region due to the microstructural intramyocardial dispersion. Parametric simulations were conducted with the injectate's elastic modulus varying from 4.1 to 405,900 kPa, and myocardial and injectate strains were recorded. With increasing injectate stiffness, the end-diastolic median myocardial fibre and cross-fibre strain decreased in magnitude from 3.6% to 1.1% and from -6.0% to -2.9%, respectively. At end-systole, the myocardial fibre and cross-fibre strain decreased in magnitude from -20.4% to -11.8% and from 6.5% to 4.6%, respectively. In the injectate, the maximum and minimum principal strains decreased in magnitude from 5.4% to 0.001% and from -5.4% to -0.001%, respectively, at end-diastole and from 38.5% to 0.06% and from -39.0% to -0.06%, respectively, at end-systole. With the microstructural injectate geometry, the developed subject-specific cardiac finite element model offers potential for extension to cellular injectates and in silico studies of mechanotransduction and therapeutic signalling in the infarcted heart with an infarct animal model extensively used in preclinical research.

Recent Advances in Hydrogel-Based Phototherapy for Tumor Treatment

Phototherapeutic agent-based phototherapies activated by light have proven to be safe modalities for the treatment of various malignant tumor indications. The two main modalities of phototherapies include photothermal therapy, which causes localized thermal damage to target lesions, and photodynamic therapy, which causes localized chemical damage by generated reactive oxygen species (ROS). Conventional phototherapies suffer a major shortcoming in their clinical application due to their phototoxicity, which primarily arises from the uncontrolled distribution of phototherapeutic agents in vivo. For successful antitumor phototherapy, it is essential to ensure the generation of heat or ROS specifically occurs at the tumor site. To minimize the reverse side effects of phototherapy while improving its therapeutic performance, extensive research has focused on developing hydrogel-based phototherapy for tumor treatment. The utilization of hydrogels as drug carriers allows for the sustained delivery of phototherapeutic agents to tumor sites, thereby limiting their adverse effects. Herein, we summarize the recent advancements in the design of hydrogels for antitumor phototherapy, offer a comprehensive overview of the latest advances in hydrogel-based phototherapy and its combination with other therapeutic modalities for tumor treatment, and discuss the current clinical status of hydrogel-based antitumor phototherapy.

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.

Effect of Matrix Metalloproteinase 23 Accelerating Wound Healing Induced by Hydroxybutyl Chitosan

Skin wounds may cause severe financial and social burden due to the difficulties in wound healing. Original inert dressings cannot meet multiple needs in the process of wound healing. Therefore, the development of materials to accelerate healing progress is essential and urgent. In the previous study, we found that the homogeneously synthesized hydroxybutyl chitosan (HBCS) had an effective performance in promoting wound healing. Proteomic analysis of the same specimen suggested that matrix metalloproteinase 23 (MMP23) may play a key role in HBCS expediting the progress of wound healing. In this work, we aim to reveal the underlying mechanism of MMP23 in the dynamic process of cutaneous proliferation and repair period. In order to regulate the expression level of MMP23 in the local wound area, we leaded in adeno-associated virus (AAV) to specifically decreased expression quantity of MMP23 in rat skin. In contrast to the negative control groups, we found that the wound closed faster and the collagen fibers and neovascularization were significantly increased in AAV groups. These findings highlighted that MMP23 was involved in wound healing after traumatic injury, and managing the expression of MMP23 could be a potential intervention target to accelerate wound healing.

A Matrix-Metalloproteinase-Responsive Hydrogel System for Modulating the Immune Microenvironment in Myocardial Infarction

Injectable hydrogels carrying therapeutic factors to modulate the infarct immune microenvironment show great potential in the treatment of myocardial infarction (MI). However, conventional injectable hydrogels release therapeutic factors in an uncontrolled manner, which leads to poor treatment efficacy and acute side effects on normal tissues. In this work, a matrix metalloproteinase (MMP)2/9-responsive hydrogel system (MPGC4) is developed, considering the characteristics of the post-MI microenvironment. MPGC4 consists of tetra-poly(ethylene glycol) (PEG) hydrogels and a composite gene nanocarrier (CTL4) that is composed of carbon dots (CDots) coupled with interleukin-4 plasmid DNA via electrostatic interactions. MPGC4 can be automatically triggered to release CTL4 on demand after MI to regulate the infarct immune microenvironment. In addition, due to the photoluminescence properties of CDots, a large amount of viscoelastic MPGC4 is found to be retained in situ after injection into the infarct region without leakage. The in vitro results demonstrate that CTL4 promotes proinflammatory M1 macrophage polarization to the anti-inflammatory M2 subtype and contributes to cardiomyocyte survival through macrophage transition. In a rat model of MI, MPGC4 clears MMPs and precisely targets CTL4 to the infarcted region. In particular, MPGC4 improves cardiac function by modulating macrophage transition to reduce early inflammatory responses and proangiogenic activity.

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.

Hierarchical Materials from High Information Content Macromolecular Building Blocks: Construction, Dynamic Interventions, and Prediction

Hierarchical materials that exhibit order over multiple length scales are ubiquitous in nature. Because hierarchy gives rise to unique properties and functions, many have sought inspiration from nature when designing and fabricating hierarchical matter. More and more, however, nature's own high-information content building blocks, proteins, peptides, and peptidomimetics, are being coopted to build hierarchy because the information that determines structure, function, and interfacial interactions can be readily encoded in these versatile macromolecules. Here, we take stock of recent progress in the rational design and characterization of hierarchical materials produced from high-information content blocks with a focus on stimuli-responsive and "smart" architectures. We also review advances in the use of computational simulations and data-driven predictions to shed light on how the side chain chemistry and conformational flexibility of macromolecular blocks drive the emergence of order and the acquisition of hierarchy and also on how ionic, solvent, and surface effects influence the outcomes of assembly. Continued progress in the above areas will ultimately usher in an era where an understanding of designed interactions, surface effects, and solution conditions can be harnessed to achieve predictive materials synthesis across scale and drive emergent phenomena in the self-assembly and reconfiguration of high-information content building blocks.

CD44 promotes angiogenesis in myocardial infarction through regulating plasma exosome uptake and further enhancing FGFR2 signaling transduction

BACKGROUND

Since angiogenesis occurs as the pathological process following myocardial infarction to alleviate ischemia, therapeutic angiogenesis has been proposed to be a cardioprotective strategy. CD44 has been implicated in endothelial cell functions and its role has been well established in angiogenesis for years. Although recent studies indicate the close correlation between CD44 and exosome, as well as the two being implicated in myocardial ischemia pathological processes, the effect and the underlying mechanism of CD44 and its regulated plasma exosome in pathological angiogenesis post-myocardial infarction have not been fully elucidated.

METHODS

In this study, we used CD44 knockout mice to study the in vivo impacts of CD44 on ischemic angiogenesis in myocardial infarction. Mouse cardiac function was measured by echocardiography, histological changes were observed by Evans Blue and TTC-double staining and Masson's trichrome staining, and molecular changes were detected by immunofluorescence. In the in vitro study, CD44 knockout HUVECs were generated and CD44 inhibitor was used to study the mechanism of CD44 on angiogenesis. We performed the immunoprecipitation, proximity ligation assay, and super-resolution imaging to study the mechanistic regulation of FGFR2 signaling transduction by CD44. Importantly, we also isolated plasma exosomes from myocardial infarction model mice and studied the effect of plasma exosomes on the activation of the FGFR2 signaling pathway and the related phenotypic alterations, including exosomes uptake and angiogenic function in primary mouse microvascular endothelial cells, and further discovered the regulation mechanism of exosomal miRNAs.

RESULTS

We observed that the expression of CD44 in the border zone of the infarcted heart was tightly related to pathological angiogenesis following myocardial ischemia. The depletion of CD44 impaired angiogenesis and impacts biogenesis and proangiogenic function of plasma exosomes. Subsequently, we found that CD44 mediated the activation of the FGFR2 signaling pathway as well as the caveolin 1-dependent uptake of exosomes in vascular endothelial cells. Most importantly, the proangiogenic therapeutic effect of plasma exosomal miRNAs depended upon the participation of CD44/FGFR2 signaling transduction in vascular endothelial cells.

CONCLUSION

CD44 and its regulated plasma exosomes have crucial potent angiogenic activity. Our studies elucidate that CD44 plays a key role in plasma exosomal miRNA-enhanced angiogenic FGFR2 singling transduction and ischemic angiogenesis in the early stage of myocardial infarction.

Ultrasound Responsive Smart Implantable Hydrogels for Targeted Delivery of Drugs: Reviewing Current Practices

Over the last two decades, the process of delivering therapeutic drugs to a patient with a controlled release profile has been a significant focus of drug delivery research. Scientists have given tremendous attention to ultrasound-responsive hydrogels for several decades. These smart nanosystems are more applicable than other stimuli-responsive drug delivery vehicles (ie UV-, pH- and thermal-, responsive materials) because they enable more efficient targeted treatment via relatively non-invasive means. Ultrasound (US) is capable of safely transporting energy through opaque and complex media with minimal loss of energy. It is capable of being localized to smaller regions and coupled to systems operating at various time scales. However, the properties enabling the US to propagate effectively in materials also make it very difficult to transform acoustic energy into other forms that may be used. Recent research from a variety of domains has attempted to deal with this issue, proving that ultrasonic effects can be used to control chemical and physical systems with remarkable specificity. By obviating the need for multiple intravenous injections, implantable US responsive hydrogel systems can enhance the quality of life for patients who undergo treatment with a varied dosage regimen. Ideally, the ease of self-dosing in these systems would lead to increased patient compliance with a particular therapy as well. However, excessive literature has been reported based on implanted US responsive hydrogel in various fields, but there is no comprehensive review article showing the strategies to control drug delivery profile. So, this review was aimed at discussing the current strategies for controlling and targeting drug delivery profiles using implantable hydrogel systems.

A ROS-Responsive Liposomal Composite Hydrogel Integrating Improved Mitochondrial Function and Pro-Angiogenesis for Efficient Treatment of Myocardial Infarction

Mitochondrial dysfunction of cardiomyocytes (CMs) has been identified as a significant pathogenesis of early myocardial infarction (MI). However, only a few agents or strategies have been developed to improve mitochondrial dysfunction for the effective MI treatment. Herein, a reactive oxygen species (ROS)-responsive PAMB-G-TK/4-arm-PEG-SG hydrogel is developed for localized drug-loaded liposome delivery. Notably, the liposomes contain both elamipretide (SS-31) and sphingosine-1-phosphate (S1P), where SS-31 acts as an inhibitor of mitochondrial oxidative damage and S1P as a signaling molecule for activating angiogenesis. Liposome-encapsulated PAMB-G-TK/4-arm-PEG-SG hydrogels demonstrate myocardium-like mechanical strength and electrical conductivity, and ROS-sensitive release of SS-31 and S1P-loaded liposomes. Further liposomal release of SS-31, which can target cytochrome c in the mitochondrial inner membrane of damaged CMs, inhibits pathological ROS production, improving mitochondrial dysfunction. Meanwhile, S1P released from the liposome induces endothelial cell angiogenesis by activating the S1PR1/PI3K/Akt pathway. In a rat MI model, the resulting liposomal composite hydrogel improves cardiac function by scavenging excess ROS, improving mitochondrial dysfunction, and promoting angiogenesis. This study reports for the first time a liposomal composite hydrogel that can directly target mitochondria of damaged CMs for a feedback-regulated release of encapsulated liposomes to consume the overproduced pathological ROS for improved CM activity and enhanced MI treatment.