Gold Nanoparticle-Functionalized Reverse Thermal Gel for Tissue Engineering Applications

Stem cells derived exosome laden oxygen generating hydrogel composites with good electrical conductivity for the tissue-repairing process of post-myocardial infarction

Acute myocardial infarction (AMI) destroys heart cells by disrupting the oxygen supply. Improving oxygen delivery to the injured area may avoid cell death and regenerate the heart. We present the creation of oxygen-producing injectable bio-macromolecular hydrogels using catalase (CAT) loaded alginate (Alg) and fibrin (Fib) incorporated with the Mesenchymal stem cells (MSCs) derived exosomes (Exo). The composite hydrogel additionally incorporates electrical stimulating qualities from gold nanoparticles (AuNPs). In vitro experiments showed that this composite hydrogel (Exo/Hydro/AuNPs/CAT) exhibits electrical conductivity similar to an actual heart and effectively releases CAT. The O2-generating hydrogel released oxygen for almost 5 days under hypoxia conditions. We showed that after 7 days of in vitro cell culture, produces the same paracrine factors as rat neonatal cardiomyocytes (RNCs), rat cardiac fibroblasts (RCFs), and Human Umbilical Vein Endothelial Cells (HUVECs), imitating capillary architecture and function. Our work demonstrated that the injectable conductive hydrogel loaded with CAT and AuNPs reduced left ventricular remodeling and myocardial dysfunction in rats after MI. Exo/Hydro/AuNPs/CAT boosted infarct margin angiogenesis, decreased cell apoptosis, and necrosis, and elevated Connexm43 (Cx43) expression. The therapeutic benefits and the ease of production of oxygen make this bioactive injectable conductive hydrogel an effective therapeutic agent for MI.

An Alginate/Gelatin Injectable Hydrogel Containing Au Nanoparticles for Transplantation of Embryonic Mouse Cardiomyocytes in Myocardial Repair

In advancing cardiac tissue engineering (CTE), the development of injectable hydrogels mirroring myocardial properties is pivotal. The designed hydrogels must not only support cardiac cell growth but also have to be conductive to properly promote the functionalities of cardiac cells. Here, a facile approach is developed to incorporate gold nanoparticles (AuNPs) into an injectable hydrogel composed of Alginate (Alg) and Gelatin (Gel). The resultant nanocomposite hydrogel boasts a porous interconnected network and superior conductivity (2.04 × 10-4 S cm-1) compared to the base Alg/Gel hydrogel. Hydrogel hydration and in vitro degradation profiles affirm their suitability as carriers for cardiac cells. Importantly, Alg/Gel+AuNPs hydrogels exhibit no toxicity to mouse Embryonic Cardiac Cells (mECCs) over 7 days, elevating connexin 43 (Cx43) and cardiac troponin T (CTnT) gene expression compared to controls. Then, the Alg/Gel+AuNPs hydrogel is used as a carrier for intramyocardial delivery of mECCs in rats with myocardial infarction. The significant increase in α-Smooth Muscle Actin (α-SMA) and cardiac troponin T (CTnT) expression along with the increase in ejection fraction (EF), smaller infarction size, less fibrosis area confirmed that the hydrogel efficiently promoted the transmission of mechanical and electrical signals between transplanted cells and surrounding tissue.

Hybrid hydrogels containing gradients in gold nanoparticles for localized delivery of mesenchymal stem cells and enhanced nerve tissues remodeling in vivo

Currently, most peripheral nerve injuries are incurable mainly due to excessive reactive oxygen species (ROS) generation in inflammatory tissues, which can further exacerbate localized tissue injury and cause chronic diseases. Although promising for promoting nerve regeneration, stem cell therapy still suffers from abundant intrinsic limitations, mainly including excessive ROS in lesions and inefficient production of growth factors (GFs). Biomaterials that scavenge endogenous ROS and promote GFs secretion might overcome such limitations and thus are being increasingly investigated. Herein, firstly reported as specific ROS scavenging agents and paracrine stimulators, gold nanoparticles (GNPs) were incorporated in the chitosan/polyvinyl alcohol hydrogel networks. The GNPs/hydrogel composite can support the survival of mesenchymal stem cells (MSCs) with excellent expansion efficiency and protect MSCs in a simulated ROS microenvironment, decreasing the intracellular ROS levels and simultaneously enhancing cell viability. Moreover, biodegradable scaffolds, along with MSCs, were implanted into sciatic nerve defects in a rat model to show good application value in vivo. Our work demonstrated that the GNPs/hydrogel shows great promise in MSCs therapy for peripheral nerve injury with convincing biological evidence.

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.

Rapid Photoinduced Self-Healing, Controllable Drug Release, Skin Adhesion Ability, and Mechanical Stability of Hydrogels Incorporating Linker-Modified Gold Nanoparticles and Nanogels

Appropriately modified thermoresponsive hydrogels, such as poly(N-isopropylacrylamide) hydrogels, bring an opportunity for a variety of biomedical applications. Incorporating compounds with different properties into poly(N-isopropylacrylamide) hydrogels offers opportunities to enhance their mechanical, self-healing ability, adhesiveness, thermal responsiveness, and drug release capabilities. In this study, we investigated the influence of Au-sulfur interactions on the properties of the poly(N-isopropylacrylamide) hydrogels after introducing N,N'-bis(acryloyl)cystine (a newly synthesized cross-linker), modified gold nanoparticles, and a p(NIPAm-BISS) nanogel into the hydrogel matrix. Our findings demonstrated that poly(N-isopropylacrylamide) hydrogels with these compounds exhibited higher mechanical strength (65% tensile stress and 25% elongation), faster thermal responsiveness, controllable self-healing [85% recovery after 2 min, using a NIR laser (800 nm, 0.75 W)], skin adhesiveness, and enhanced drug release (0.08 mg·mL-1, a 93% improvement). These results may contribute to advancements in the design of temperature-responsive hydrogels tailored for specific biomedical needs, such as targeted drug delivery with the use of a NIR laser and tissue engineering.

Optically Active, Paper-Based Scaffolds for 3D Cardiac Pacing

In this work, we report the design and fabrication of a light-addressable, paper-based nanocomposite scaffold for optical pacing and read-out of in vitro grown cardiac tissue. The scaffold consists of paper cellulose microfibers functionalized with gold nanorods (GNRs) and semiconductor quantum dots (QDs), embedded in a cell-permissive collagen matrix. The GNRs enable cardiomyocyte activity modulation through local temperature gradients induced by modulated near-infrared (NIR) laser illumination, with the local temperature changes reported by temperature-dependent QD photoluminescence (PL). The micrometer-sized paper fibers promote the tubular organization of HL-1 cardiac muscle cells, while the NIR plasmonic stimulation modulates reversibly their activity. Given the nanoscale spatial resolution and facile fabrication, paper-based nanocomposite scaffolds with NIR modulation offer excellent alternatives to electrode-based or optogenetic methods for cell activity modulation, at the single cell level, and are compatible with 3D tissue constructs. Such paper-based optical platforms can provide new possibilities for the development of in vitro drug screening assays and heart disease modeling.

Advances in injectable hydrogels for radiation-induced heart disease

Radiological heart damage (RIHD) is damage caused by unavoidable irradiation of the heart during chest radiotherapy, with a long latency period and a progressively increasing proportion of delayed cardiac damage due to conventional doses of chest radiotherapy. There is a risk of inducing diseases such as acute/chronic pericarditis, myocarditis, delayed myocardial fibrosis and damage to the cardiac conduction system in humans, which can lead to myocardial infarction or even death in severe cases. This paper details the pathogenesis of RIHD and gives potential targets for treatment at the molecular and cellular level, avoiding the drawbacks of high invasiveness and immune rejection due to drug therapy, medical device implantation and heart transplantation. Injectable hydrogel therapy has emerged as a minimally invasive tissue engineering therapy to provide necessary mechanical support to the infarcted myocardium and to act as a carrier for various bioactive factors and cells to improve the cellular microenvironment in the infarcted area and induce myocardial tissue regeneration. Therefore, this paper combines bioactive factors and cellular therapeutic mechanisms with injectable hydrogels, presents recent advances in the treatment of cardiac injury after RIHD with different injectable gels, and summarizes the therapeutic potential of various types of injectable hydrogels as a potential solution.

Nanoparticles incorporated hydrogels for delivery of antimicrobial agents: developments and trends

The prevention and treatment of microbial infections is an imminent global public health concern due to the poor antimicrobial performance of the existing antimicrobial regime and rapidly emerging antibiotic resistance in pathogenic microbes. In order to overcome these problems and effectively control bacterial infections, various new treatment modalities have been identified. To attempt this, various micro- and macro-molecular antimicrobial agents that function by microbial membrane disruption have been developed with improved antimicrobial activity and lesser resistance. Antimicrobial nanoparticle-hydrogels systems comprising antimicrobial agents (antibiotics, biological extracts, and antimicrobial peptides) loaded nanoparticles or antimicrobial nanoparticles (metal or metal oxide) constitute an important class of biomaterials for the prevention and treatment of infections. Hydrogels that incorporate nanoparticles can offer an effective strategy for delivering antimicrobial agents (or nanoparticles) in a controlled, sustained, and targeted manner. In this review, we have described an overview of recent advancements in nanoparticle-hydrogel hybrid systems for antimicrobial agent delivery. Firstly, we have provided an overview of the nanoparticle hydrogel system and discussed various advantages of these systems in biomedical and pharmaceutical applications. Thereafter, different hybrid hydrogel systems encapsulating antibacterial metal/metal oxide nanoparticles, polymeric nanoparticles, antibiotics, biological extracts, and antimicrobial peptides for controlling infections have been reviewed in detail. Finally, the challenges and future prospects of nanoparticle-hydrogel systems have been discussed.

Metal nanoparticle hybrid hydrogels: the state-of-the-art of combining hard and soft materials to promote wound healing

Wounds represent a grave affliction that profoundly impacts human well-being. Establishing barriers, preventing infections, and providing a conducive microenvironment constitute the crux of wound therapy. Hydrogel, a polymer with an intricate three-dimensional lattice, serves as a potent tool in erecting physical barriers and nurturing an environment conducive to wound healing. This enables effective control over exudation, hemostasis, accelerated wound closure, and diminished scar formation. As a result, hydrogels have gained extensive traction in the realm of wound treatment. Metallic nanoparticle carriers, characterized by their multifaceted responses encompassing acoustics, optics, and electronics, have demonstrated efficacy in wound management. Nevertheless, these carriers encounter challenges associated with swift clearance and nonuniform effectiveness. The hybridization of metallic nanoparticle carriers with hydrogels overcomes the shortcomings inherent in metallic nanoparticle-based wound therapy. This amalgamation not only addresses the limitations but also augments the mechanical robustness of hydrogels. It confers upon them attributes such as environmental responsiveness and multifunctionality, thereby synergizing strengths and compensating for weaknesses. This integration culminates in the precise and intelligent management of wounds. This review encapsulates the structural classifications, design strategies, therapeutic applications, and underlying mechanisms of metal nanoparticle hybrid hydrogels in the context of acute and chronic wound treatment. The discourse delves into the generation of novel or enhanced attributes arising from hybridization and how the current paradigm of wound therapy leverages these attributes. Amidst this continually evolving frontier, the potential of metal nanoparticle hybrid hydrogels to revolutionize wound treatment is underscored.

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.

Nanocomposite hydrogels for biomedical applications

Nanomaterials' unique structures at the nanometer level determine their incredible functions, and based on this, they can be widely used in the field of nanomedicine. However, nanomaterials do possess disadvantages that cannot be ignored, such as burst release, rapid elimination, and poor bioadhesion. Hydrogels are scaffolds with three-dimensional structures, and they exhibit good biocompatibility and drug release capacity. Hydrogels are also associated with disadvantages for biomedical applications such as poor anti-tumor capability, weak bioimaging capability, limited responsiveness, and so on. Incorporating nanomaterials into the 3D hydrogel network through physical or chemical covalent action may be an effective method to avoid their disadvantages. In nanocomposite hydrogel systems, multifunctional nanomaterials often work as the function core, giving the hydrogels a variety of properties (such as photo-thermal conversion, magnetothermal conversion, conductivity, targeting tumor, etc.). While, hydrogels can effectively improve the retention effect of nanomaterials and make the nanoparticles have good plasticity to adapt to various biomedical applications (such as various biosensors). Nanocomposite hydrogel systems have broad application prospects in biomedicine. In this review, we comprehensively summarize and discuss the most recent advances of nanomaterials composite hydrogels in biomedicine, including drug and cell delivery, cancer treatment, tissue regeneration, biosensing, and bioimaging, and we also briefly discussed the current situation of their commoditization in biomedicine.

Advancing Engineered Heart Muscle Tissue Complexity with Hydrogel Composites

A heart attack results in the permanent loss of heart muscle and can lead to heart disease, which kills more than 7 million people worldwide each year. To date, outside of heart transplantation, current clinical treatments cannot regenerate lost heart muscle or restore full function to the damaged heart. There is a critical need to create engineered heart tissues with structural complexity and functional capacity needed to replace damaged heart muscle. The inextricable link between structure and function suggests that hydrogel composites hold tremendous promise as a biomaterial-guided strategy to advance heart muscle tissue engineering. Such composites provide biophysical cues and functionality as a provisional extracellular matrix that hydrogels cannot on their own. This review describes the latest advances in the characterization of these biomaterial systems and using them for heart muscle tissue engineering. The review integrates results across the field to provide new insights on critical features within hydrogel composites and perspectives on the next steps to harnessing these promising biomaterials to faithfully reproduce the complex structure and function of native heart muscle.

Sodium Alginate/Chitosan Scaffolds for Cardiac Tissue Engineering: The Influence of Its Three-Dimensional Material Preparation and the Use of Gold Nanoparticles

Natural biopolymer scaffolds and conductive nanomaterials have been widely used in cardiac tissue engineering; however, there are still challenges in the scaffold fabrication, which include enhancing nutrient delivery, biocompatibility and properties that favor the growth, maturation and functionality of the generated tissue for therapeutic application. In the present work, different scaffolds prepared with sodium alginate and chitosan (alginate/chitosan) were fabricated with and without the addition of metal nanoparticles and how their fabrication affects cardiomyocyte growth was evaluated. The scaffolds (hydrogels) were dried by freeze drying using calcium gluconate as a crosslinking agent, and two types of metal nanoparticles were incorporated, gold (AuNp) and gold plus sodium alginate (AuNp+Alg). A physicochemical characterization of the scaffolds was carried out by swelling, degradation, permeability and infrared spectroscopy studies. The results show that the scaffolds obtained were highly porous (>90%) and hydrophilic, with swelling percentages of around 3000% and permeability of the order of 1 × 10−8 m2. In addition, the scaffolds proposed favored adhesion and spheroid formation, with cardiac markers expression such as tropomyosin, troponin I and cardiac myosin. The incorporation of AuNp+Alg increased cardiac protein expression and cell proliferation, thus demonstrating their potential use in cardiac tissue engineering.

Preparation of Various Nanomaterials via Controlled Gelation of a Hydrophilic Polymer Bearing Metal-Coordination Units with Metal Ions

We investigated the gelation of a hydrophilic polymer with metal-coordination units (HPMC) and metal ions (PdII or AuIII). Gelation proceeded by addition of an HPMC solution in N-methyl-2-pyrrolidone (NMP) to a metal ion aqueous solution. An increase in the composition ratio of the metal-coordination units from 10 mol% to 34 mol% (HPMC-34) increased the cross-linking rate with AuIII. Cross-linking immediately occurred after dropwise addition of an HPMC-34 solution to the AuIII solution, generating the separation between the phases of HPMC-34 and AuIII. The cross-linking of AuIII proceeded from the surface to the inside of the HPMC-34 droplets, affording spherical gels. In contrast, a decrease in the ratio of metal-coordination units from 10 mol% to 4 mol% (HPMC-4) decreased the PdII cross-linking rate. The cross-linking occurred gradually and the gels extended to the bottom of the vessel, forming fibrous gels. On the basis of the mechanism for the formation of gels with different morphologies, the gelation of HPMC-34 and AuIII provided nanosheets via gelation at the interface between the AuIII solution and the HPMC-34 solution. The gelation of HPMC-4 and PdII afforded nanofibers by a facile method, i.e., dropwise addition of the HPMC-4 solution to the PdII solution. These results demonstrated that changing the composition ratio of the metal-coordination units in HPMC can control the gelation behavior, resulting in different types of nanomaterials.

Bioelectricity-coupling patches for repairing impaired myocardium

Cardiac abnormalities, which account for extensive burdens on public health and economy, drive necessary attempts to revolutionize the traditional therapeutic system. Advances in cardiac tissue engineering have expanded a highly efficacious platform to address cardiovascular events, especially cardiac infarction. Current efforts to overcome biocompatible limitations highlight the constructs of a conductive cardiac patch to accelerate the industrial and clinical landscape that is amenable for patient-accurate therapy, regenerative medicine, disease modeling, and drug delivery. With the notion that cardiac tissue synchronically contracts triggered by electrical pulses, the cardiac patches based on conductive materials are developed and treated on the dysfunctional heart. In this review, we systematically summarize distinct conductive materials serving as the most promising alternatives (conductive nanomaterials, conductive polymers, piezoelectric polymers, and ionic electrolytes) to achieve electric signal transmission and engineered cardiac tissues. Existing applications are discussed considering how these patches containing conductive candidates are fabricated into diverse forms with major strategies. Ultimately, we try to define a new concept as a bioelectricity-coupling patch that provides a favorable cardiac micro-environment for cardiac functional activities. Underlying challenges and prospects are presented regarding industrial processing and cardiovascular treatment of conductive patch progress. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease.

Recent Development of Conductive Hydrogels for Tissue Engineering: Review and Perspective

In recent years, tissue engineering techniques have been rapidly developed and offer a new therapeutic approach to organ or tissue damage repair. However, most of tissue engineering scaffolds are nonconductive and cannot establish effective electrical coupling with tissue for the electroactive tissues. Electroconductive hydrogels (ECHs) have received increasing attention in tissue engineering owing to their electroconductivity, biocompatibility and high water content. In vitro, ECHs can not only promote the communication of electrical signals between cells, but also mediate the adhesion, proliferation, migration, and differentiation of different kinds of cells. In vivo, ECHs can transmit the electric signal to electroactive tissues and activate bioelectrical signaling pathways to promote tissue repair. As a result, implanting ECHs into damaged tissues can effectively reconstruct physiological functions related to electrical conduction. In this review, we first present an overview about the classifications and the fabrication methods of ECHs. And then, the applications of ECHs in tissue engineering, including cardiac, nerve, skin and skeletal muscle tissue, are highlighted. At last, we provide some rational guidelines for designing ECHs towards clinical applications. This article is protected by copyright. All rights reserved.

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.

Effects of electrically conductive nano-biomaterials on regulating cardiomyocyte behavior for cardiac repair and regeneration

Myocardial infarction (MI) represents one of the most prevalent cardiovascular diseases, with a highly relevant and impactful role in public health. Despite the therapeutic advances of the last decades, MI still begets extensive death rates around the world. The pathophysiology of the disease correlates with cardiomyocyte necrosis, caused by an imbalance in the demand of oxygen to cardiac tissues, resulting from obstruction of the coronary flow. To alleviate the severe effects of MI, the use of various biomaterials exhibit vast potential in cardiac repair and regeneration, acting as native extracellular matrices. These hydrogels have been combined with nano sized or functional materials which possess unique electrical, mechanical, and topographical properties that play important roles in regulating phenotypes and the contractile function of cardiomyocytes even in adverse microenvironments. These nano-biomaterials' differential properties have led to substantial healing on in vivo cardiac injury models by promoting fibrotic scar reduction, hemodynamic function preservation, and benign cardiac remodeling. In this review, we discuss the interplay of the unique physical properties of electrically conductive nano-biomaterials, are able to manipulate the phenotypes and the electrophysiological behavior of cardiomyocytes in vitro, and can enhance heart regeneration in vivo. Consequently, the understanding of the decisive roles of the nano-biomaterials discussed in this review could be useful for designing novel nano-biomaterials in future research for cardiac tissue engineering and regeneration. STATEMENT OF SIGNIFICANCE: This study introduced and deciphered the understanding of the role of multimodal cues in recent advances of electrically conductive nano-biomaterials on cardiac tissue engineering. Compared with other review papers, which mainly describe these studies based on various types of electrically conductive nano-biomaterials, in this review paper we mainly discussed the interplay of the unique physical properties (electrical conductivity, mechanical properties, and topography) of electrically conductive nano-biomaterials, which would allow them to manipulate phenotypes and the electrophysiological behavior of cardiomyocytes in vitro and to enhance heart regeneration in vivo. Consequently, understanding the decisive roles of the nano-biomaterials discussed in the review could help design novel nano-biomaterials in future research for cardiac tissue engineering and regeneration.

Preliminary Results of a Reverse Thermal Gel Patch for Fetal Ovine Myelomeningocele Repair

BACKGROUND

Prenatal surgical closure of Myelomeningocele (MMC) is considered part of the current age armamentarium. Clinical data has demonstrated the need for innovative patches to maximize the benefits and decrease the risks of this approach. Our team has developed a minimally invasive reverse thermal gel (RTG) patch with cellular scaffolding properties. Here, we demonstrate the initial gross and microscopic histological effects of this RTG patch in the fetal ovine model of MMC.

MATERIALS AND METHODS

A fetal ovine MMC defect was created at 68-75 days gestation, RTG patch application or untreated at 100-103 days, and harvest at 135-140 days. The RTG was applied to the defect and secured in place with an overlay sealant. Defect areas underwent gross and microscopic analysis for inflammation and skin development. Brains were analyzed for hindbrain herniation and hydrocephalus.

RESULTS

The untreated fetus (n = 1) demonstrated an open defect lacking tissue coverage, evidence of spinal cord injury, increased caspase-3, Iba1 and GFAP in spinal cord tissues, and hindbrain herniation and ventricular dilation. RTG treated fetuses (n = 3) demonstrated defect healing with well-organized dermal and epidermal layers throughout the entire healed tissue area overlaying the defect with minimal inflammation, reduced caspase-3, Iba1 and GFAP in spinal cord tissues, and no hindbrain herniation or ventricular dilation.

CONCLUSION

An RTG patch applied to MMC defects in fetal sheep promoted skin coverage over the defect, was associated with minimal inflammation of the spinal cord tissues and prevented brain abnormalities. The present findings provide exciting results for future comprehensive radiological, functional, and mechanistic evaluation of the RTG.

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.

Advances in Nanomaterials for Injured Heart Repair

Atherosclerotic cardiovascular disease (ASCVD) is one of the leading causes of mortality worldwide. Because of the limited regenerative capacity of adult myocardium to compensate for the loss of heart tissue after ischemic infarction, scientists have been exploring the possible mechanisms involved in the pathological process of ASCVD and searching for alternative means to regenerate infarcted cardiac tissue. Although numerous studies have pursued innovative solutions for reversing the pathological process of ASCVD and improving the effectiveness of delivering therapeutics, the translation of those advances into downstream clinical applications remains unsatisfactory because of poor safety and low efficacy. Recently, nanomaterials (NMs) have emerged as a promising new strategy to strengthen both the efficacy and safety of ASCVD therapy. Thus, a comprehensive review of NMs used in ASCVD treatment will be useful. This paper presents an overview of the pathophysiological mechanisms of ASCVD and the multifunctional mechanisms of NM-based therapy, including antioxidative, anti-inflammation and antiapoptosis mechanisms. The technological improvements of NM delivery are summarized and the clinical transformations concerning the use of NMs to treat ASCVD are examined. Finally, this paper discusses the challenges and future perspectives of NMs in cardiac regeneration to provide insightful information for health professionals on the latest advancements in nanotechnologies for ASCVD treatment.

Extrinsically Conductive Nanomaterials for Cardiac Tissue Engineering Applications

Myocardial infarction (MI) is the consequence of coronary artery thrombosis resulting in ischemia and necrosis of the myocardium. As a result, billions of contractile cardiomyocytes are lost with poor innate regeneration capability. This degenerated tissue is replaced by collagen-rich fibrotic scar tissue as the usual body response to quickly repair the injury. The non-conductive nature of this tissue results in arrhythmias and asynchronous beating leading to total heart failure in the long run due to ventricular remodelling. Traditional pharmacological and assistive device approaches have failed to meet the utmost need for tissue regeneration to repair MI injuries. Engineered heart tissues (EHTs) seem promising alternatives, but their non-conductive nature could not resolve problems such as arrhythmias and asynchronous beating for long term in-vivo applications. The ability of nanotechnology to mimic the nano-bioarchitecture of the extracellular matrix and the potential of cardiac tissue engineering to engineer heart-like tissues makes it a unique combination to develop conductive constructs. Biomaterials blended with conductive nanomaterials could yield conductive constructs (referred to as extrinsically conductive). These cell-laden conductive constructs can alleviate cardiac functions when implanted in-vivo. A succinct review of the most promising applications of nanomaterials in cardiac tissue engineering to repair MI injuries is presented with a focus on extrinsically conductive nanomaterials.

Endogenous Electric Signaling as a Blueprint for Conductive Materials in Tissue Engineering

Bioelectricity plays an important role in cell behavior and tissue modulation, but is understudied in tissue engineering research. Endogenous electrical signaling arises from the transmembrane potential inherent to all cells and contributes to many cell behaviors, including migration, adhesion, proliferation, and differentiation. Electrical signals are also involved in tissue development and repair. Synthetic and natural conductive materials are under investigation for leveraging endogenous electrical signaling cues in tissue engineering applications due to their ability to direct cell differentiation, aid in maturing electroactive cell types, and promote tissue functionality. In this review, we provide a brief overview of bioelectricity and its impact on cell behavior, report recent literature using conductive materials for tissue engineering, and discuss opportunities within the field to improve experimental design when using conductive substrates.

Bio-inspired surface modification of iron oxide nanoparticles for active stabilization in hydrogels

Biological materials employ a variety of dynamic interactions in sophisticated composite structures to function adaptively on different time and length scales. Inspired by such designs we develop a novel surface modification approach to promote dynamic interactions between nanoparticles and polymer chains in physical and double network hydrogels. Physical hydrogels are formed via reversible complexation of borate ions with poly(vinyl alcohol) (PVA) and chemical crosslinks are introduced by electron beam irradiation. Dopamine is used for surface modification of magnetic iron oxide nanoparticles (MNPs) in two different ways: the direct treatment results in anchoring via catechol groups, whereas the indirect method leaves the catechol group on the free surface of MNPs. Although the former particles show very good colloidal stability, they lower the network connectivity, which results in lower plateau modulus, faster terminal relaxation, and lower yield stress, presumably due to imposing an extra distance between PVA chains. In contrast to this passive design, the latter particles actively reinforce the network by forming clusters of physical bonds between catechol groups of the individual particles and the monodiol complexes of the borate ions and PVA chains. Moreover, the additional complexes formed upon the introduction of nanoparticles with active surfaces provide further energy dissipation potential and therefore enhance the toughness. This approach can help develop novel hydrogels with superior toughness and multiple stimuli-responsiveness.

Multifunctional Conductive Biomaterials as Promising Platforms for Cardiac Tissue Engineering

Adult cardiomyocytes are terminally differentiated cells that result in minimal intrinsic potential for the heart to self-regenerate. The introduction of novel approaches in cardiac tissue engineering aims to repair damages from cardiovascular diseases. Recently, conductive biomaterials such as carbon- and gold-based nanomaterials, conductive polymers, and ceramics that have outstanding electrical conductivity, acceptable mechanical properties, and promoted cell-cell signaling transduction have attracted attention for use in cardiac tissue engineering. Nevertheless, comprehensive classification of conductive biomaterials from the perspective of cardiac cell function is a subject for discussion. In the present review, we classify and summarize the unique properties of conductive biomaterials considered beneficial for cardiac tissue engineering. We attempt to cover recent advances in conductive biomaterials with a particular focus on their effects on cardiac cell functions and proposed mechanisms of action. Finally, current problems, limitations, challenges, and suggested solutions for applications of these biomaterials are presented.

Nanomaterials for Cardiac Tissue Engineering

End stage heart failure is a major cause of death in the US. At present, organ transplant and left-ventricular assist devices remain the only viable treatments for these patients. Cardiac tissue engineering presents the possibility of a new option. Nanomaterials such as gold nanorods (AuNRs) and carbon nanotubes (CNTs) present unique properties that are beneficial for cardiac tissue engineering approaches. In particular, these nanomaterials can modulate electrical conductivity, hardness, and roughness of bulk materials to improve tissue functionality. Moreover, they can deliver bioactive cargo to affect cell phenotypes. This review covers recent advances in the use of nanomaterials for cardiac tissue engineering.

Next Stage Approach to Tissue Engineering Skeletal Muscle

Large-scale muscle injury in humans initiates a complex regeneration process, as not only the muscular, but also the vascular and neuro-muscular compartments have to be repaired. Conventional therapeutic strategies often fall short of reaching the desired functional outcome, due to the inherent complexity of natural skeletal muscle. Tissue engineering offers a promising alternative treatment strategy, aiming to achieve an engineered tissue close to natural tissue composition and function, able to induce long-term, functional regeneration after in vivo implantation. This review aims to summarize the latest approaches of tissue engineering skeletal muscle, with specific attention toward fabrication, neuro-angiogenesis, multicellularity and the biochemical cues that adjuvate the regeneration process.

Nanoparticle-hydrogel superstructures for biomedical applications

The incorporation of nanoparticles into hydrogels yields novel superstructures that have become increasingly popular in biomedical research. Each component of these nanoparticle-hydrogel superstructures can be easily modified, resulting in platforms that are highly tunable and inherently multifunctional. The advantages of the nanoparticle and hydrogel constituents can be synergistically combined, enabling these superstructures to excel in scenarios where employing each component separately may have suboptimal outcomes. In this review, the synthesis and fabrication of different nanoparticle-hydrogel superstructures are discussed, followed by an overview of their use in a range of applications, including drug delivery, detoxification, immune modulation, and tissue engineering. Overall, these platforms hold significant clinical potential, and it is envisioned that future development along these lines will lead to unique solutions for addressing areas of pressing medical need.

Oriented Immobilization on Gold Nanoparticles of a Recombinant Therapeutic Zymogen

Direct immobilization of functional proteins on gold nanoparticles (AuNPs) affects their structure and function. Changes may vary widely and range from strong inhibition to the enhancement of protein function. More often though the outcome of direct protein immobilization results in protein misfolding and the loss of protein activity. Additional complications arise when the protein being immobilized is a zymogen which requires and relies on additional protein-protein interactions to exert its function. Here we describe molecular design of a glutathione-S-transferase-Staphylokinase fusion protein (GST-SAK) and its conjugation to AuNPs. The multivalent AuNP-(GST-SAK)n complexes generated show plasminogen activation activity in vitro. The methods described are transferable and could be adapted for conjugation and functional analysis of other plasminogen activators, thrombolytic preparations or other functional enzymes.

High-aspect-ratio water-dispersed gold nanowires incorporated within gelatin methacrylate hydrogels for constructing cardiac tissues in vitro

The prepared high-aspect-ratio water-dispersed gold nanowires are incorporated into GeIMA hydrogels for cardiomyocyte culture and micro-cardiac tissue formation.