Full-Thickness Heart Repair with an Engineered Multilayered Myocardial Patch in Rat Model

Triggerable Patches for Medical Applications

Medical patches have garnered increasing attention in recent decades for several diagnostic and therapeutic applications. Advancements in material science, manufacturing technologies, and bioengineering have significantly widened their functionalities, rendering them highly versatile platforms for wearable and implantable applications. Of particular interest are triggerable patches designed for drug delivery and tissue regeneration purposes, whose action can be controlled by an external signal. Stimuli-responsive patches are particularly appealing as they may enable a high level of temporal and spatial control over the therapy, allowing high therapeutic precision and the possibility to adjust the treatment according to specific clinical and personal needs. This review aims to provide a comprehensive overview of the existing extensive literature on triggerable patches, emphasizing their potential for diverse applications and highlighting the strengths and weaknesses of different triggering stimuli. Additionally, the current open challenges related to the design and use of efficient triggerable patches, such as tuning their mechanical and adhesive properties, ensuring an acceptable trade-off between smartness and biocompatibility, endowing them with portability and autonomy, accurately controlling their responsiveness to the triggering stimulus and maximizing their therapeutic efficacy, are reviewed.

The Current State of Extracellular Matrix Therapy for Ischemic Heart Disease

The extracellular matrix (ECM) is a three-dimensional, acellular network of diverse structural and nonstructural proteins embedded within a gel-like ground substance composed of glycosaminoglycans and proteoglycans. The ECM serves numerous roles that vary according to the tissue in which it is situated. In the myocardium, the ECM acts as a collagen-based scaffold that mediates the transmission of contractile signals, provides means for paracrine signaling, and maintains nutritional and immunologic homeostasis. Given this spectrum, it is unsurprising that both the composition and role of the ECM has been found to be modulated in the context of cardiac pathology. Myocardial infarction (MI) provides a familiar example of this; the ECM changes in a way that is characteristic of the progressive phases of post-infarction healing. In recent years, this involvement in infarct pathophysiology has prompted a search for therapeutic targets: if ECM components facilitate healing, then their manipulation may accelerate recovery, or even reverse pre-existing damage. This possibility has been the subject of numerous efforts involving the integration of ECM-based therapies, either derived directly from biologic sources or bioengineered sources, into models of myocardial disease. In this paper, we provide a thorough review of the published literature on the use of the ECM as a novel therapy for ischemic heart disease, with a focus on biologically derived models, of both the whole ECM and the components thereof.

An In Vitro Characterization of a PCL-Fibrin Scaffold for Myocardial Repair

Each year in the United States approximately 10,000 babies are born with a complex congenital heart defect (CHD) requiring surgery in the first year of after birth. Several of these operations require the implantation of a full-thickness heart patch; however, the current patch materials available to pediatric heart surgeons are exclusively non-living and non-degradable, which do not grow with the patient and are prone to fail due to an inability to integrate with the heart. In this work, the goal was to develop a full-thickness, tissue engineered myocardial patch (TEMP) that is made from biodegradable components, strong enough to withstand the mechanical forces of the heart wall, and able to integrate with the heart and drive neotissue formation. Here, a thick and porous electrospun PCL scaffold filled with high-salt PEGylated fibrin was developed. The scaffold was found to be mechanically sufficient for heart wall repair. Vascular cells were able to infiltrate more than halfway through the scaffold in static culture within three weeks. The scaffold maintained pluripotent stem cells for at least four days, supports viable iPSC-derived cardiomyocytes, and fostered tissue thickening in vitro. The TEMP developed here and tested in vitro is promising for the repair of structural CHD and will next be assessed in situ.

Recent advances in soluble decellularized extracellular matrix for heart tissue engineering and organ modeling

Despite the advent of tissue engineering (TE) for the remodeling, restoring, and replacing damaged cardiovascular tissues, the progress is hindered by the optimal mechanical and chemical properties required to induce cardiac tissue-specific cellular behaviors including migration, adhesion, proliferation, and differentiation. Cardiac extracellular matrix (ECM) consists of numerous structural and functional molecules and tissue-specific cells, therefore it plays an important role in stimulating cell proliferation and differentiation, guiding cell migration, and activating regulatory signaling pathways. With the improvement and modification of cell removal methods, decellularized ECM (dECM) preserves biochemical complexity, and bio-inductive properties of the native matrix and improves the process of generating functional tissue. In this review, we first provide an overview of the latest advancements in the utilization of dECM in in vitro model systems for disease and tissue modeling, as well as drug screening. Then, we explore the role of dECM-based biomaterials in cardiovascular regenerative medicine (RM), including both invasive and non-invasive methods. In the next step, we elucidate the engineering and material considerations in the preparation of dECM-based biomaterials, namely various decellularization techniques, dECM sources, modulation, characterizations, and fabrication approaches. Finally, we discuss the limitations and future directions in fabrication of dECM-based biomaterials for cardiovascular modeling, RM, and clinical translation.

Materials and Design Approaches for a Fully Bioresorbable, Electrically Conductive and Mechanically Compliant Cardiac Patch Technology

Myocardial infarction (MI) is one of the leading causes of death and disability. Recently developed cardiac patches provide mechanical support and additional conductive paths to promote electrical signal propagation in the MI area to synchronize cardiac excitation and contraction. Cardiac patches based on conductive polymers offer attractive features; however, the modest levels of elasticity and high impedance interfaces limit their mechanical and electrical performance. These structures also operate as permanent implants, even in cases where their utility is limited to the healing period of tissue damaged by the MI. The work presented here introduces a highly conductive cardiac patch that combines bioresorbable metals and polymers together in a hybrid material structure configured in a thin serpentine geometry that yields elastic mechanical properties. Finite element analysis guides optimized choices of layouts in these systems. Regular and synchronous contraction of human induced pluripotent stem cell-derived cardiomyocytes on the cardiac patch and ex vivo studies offer insights into the essential properties and the bio-interface. These results provide additional options in the design of cardiac patches to treat MI and other cardiac disorders.

Chitosan-Based Scaffolds for the Treatment of Myocardial Infarction: A Systematic Review

Cardiovascular diseases (CVD), such as myocardial infarction (MI), constitute one of the world's leading causes of annual deaths. This cardiomyopathy generates a tissue scar with poor anatomical properties and cell necrosis that can lead to heart failure. Necrotic tissue repair is required through pharmaceutical or surgical treatments to avoid such loss, which has associated adverse collateral effects. However, to recover the infarcted myocardial tissue, biopolymer-based scaffolds are used as safer alternative treatments with fewer side effects due to their biocompatibility, chemical adaptability and biodegradability. For this reason, a systematic review of the literature from the last five years on the production and application of chitosan scaffolds for the reconstructive engineering of myocardial tissue was carried out. Seventy-five records were included for review using the "preferred reporting items for systematic reviews and meta-analyses" data collection strategy. It was observed that the chitosan scaffolds have a remarkable capacity for restoring the essential functions of the heart through the mimicry of its physiological environment and with a controlled porosity that allows for the exchange of nutrients, the improvement of the electrical conductivity and the stimulation of cell differentiation of the stem cells. In addition, the chitosan scaffolds can significantly improve angiogenesis in the infarcted tissue by stimulating the production of the glycoprotein receptors of the vascular endothelial growth factor (VEGF) family. Therefore, the possible mechanisms of action of the chitosan scaffolds on cardiomyocytes and stem cells were analyzed. For all the advantages observed, it is considered that the treatment of MI with the chitosan scaffolds is promising, showing multiple advantages within the regenerative therapies of CVD.

Promotion of right ventricular outflow tract reconstruction using a novel cardiac patch incorporated with hypoxia-pretreated urine-derived stem cells

Approximately 25% of patients with congenital heart disease require implantation of patches to repair. However, most of the currently available patches are made of inert materials with unmatched electrical conductivity and mechanical properties, which may lead to an increased risk for arrhythmia and heart failure. In this study, we have developed a novel Polyurethane/Small intestinal submucosa patch (PSP) with mechanical and electrical properties similar to those of the native myocardial tissue, and assessed its feasibility for the reconstruction of right ventricular outflow tract. A right ventricular outflow tract reconstruction model was constructed in 40 rabbits. Compared with commercially available bovine pericardium patch, the PSP patch has shown better histocompatibility and biodegradability, in addition with significantly improved cardiac function. To tackle the significant fibrosis and relatively poor vascularization during tissue remodeling, we have further developed a bioactive patch by incorporating the PSP composites with urine-derived stem cells (USCs) which were pretreated with hypoxia. The results showed that the hypoxia-pretreated bioactive patch could significantly inhibit fibrosis and promote vascularization and muscularization, resulting in better right heart function. Our findings suggested that the PSP patch combined with hypoxia-pretreated USCs may provide a better strategy for the treatment of congenital heart disease.

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A novel cardiac patch (PSP) with mechanical and electrical properties similar to native myocardium.

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PSP patch improved cardiac function in right ventricular outflow tract reconstruction model.

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Hypoxia pretreated USCs combined PSP patch promoted vascularization and inhibited fibrosis.

A Biohybrid Material With Extracellular Matrix Core and Polymeric Coating as a Cell Honing Cardiovascular Tissue Substitute

Objective

To investigate the feasibility of a hybrid material in which decellularized pericardial extracellular matrix is functionalized with polymeric nanofibers, for use as a cardiovascular tissue substitute.

Background

A cardiovascular tissue substitute, which is gradually resorbed and is replaced by host's native tissue, has several advantages. Especially in children and young adults, a resorbable material can be useful in accommodating growth, but also enable rapid endothelialization that is necessary to avoid thrombotic complications. In this study, we report a hybrid material, wherein decellularized pericardial matrix is functionalized with a layer of polymeric nanofibers, to achieve the mechanical strength for implantation in the cardiovascular system, but also have enhanced cell honing capacity.

Methods

Pericardial sacs were decellularized with sodium deoxycholate, and polycaprolactone-chitosan fibers were electrospun onto the matrix. Tissue-polymer interaction was evaluated using spectroscopic methods, and the mechanical properties of the individual components and the hybrid material were quantified. In-vitro blood flow loop studies were conducted to assess hemocompatibility and cell culture methods were used to assess biocompatibility.

Results

Encapsulation of the decellularized matrix with 70 μm thick matrix of polycaprolactone-chitosan nanofibers, was feasible and reproducible. Spectroscopy of the cross-section depicted new amide bond formation and C–O–C stretch at the interface. An average peel strength of 56.13 ± 11.87 mN/mm2 was measured, that is sufficient to withstand a high shear of 15 dynes/cm2 without delamination. Mechanical strength and extensibility ratio of the decellularized matrix alone were 18,000 ± 4,200 KPa and 0.18 ± 0.03% whereas that of the hybrid was higher at 20,000 ± 6,600 KPa and 0.35 ± 0.20%. Anisotropy index and stiffness of the biohybrid were increased as well. Neither thrombus formation, nor platelet adhesion or hemolysis was measured in the in-vitro blood flow loop studies. Cellular adhesion and survival were adequate in the material.

Conclusion

Encapsulating a decellularized matrix with a polymeric nanofiber coating, has favorable attributes for use as a cardiovascular tissue substitute.

Electrically conductive 3D printed Ti3C2Tx MXene-PEG composite constructs for cardiac tissue engineering

Tissue engineered cardiac patches have great potential as a therapeutic treatment for myocardial infarction (MI). However, for successful integration with the native tissue and proper function of the cells comprising the patch, it is crucial for these patches to mimic the ordered structure of the native extracellular matrix and the electroconductivity of the human heart. In this study, a new composite construct that can provide both conductive and topographical cues for human induced pluripotent stem cell derived cardiomyocytes (iCMs) is developed for cardiac tissue engineering applications. The constructs are fabricated by 3D printing conductive titanium carbide (Ti₃C₂T_x) MXene in pre-designed patterns on polyethylene glycol (PEG) hydrogels, using aerosol jet printing, at a cell-level resolution and then seeded with iCMs and cultured for one week with no signs of cytotoxicity. The results presented in this work illustrate the vital role of 3D-printed Ti₃C₂T_x MXene on aligning iCMs with a significant increase in MYH7, SERCA2, and TNNT2 expressions, and with an improved synchronous beating as well as conduction velocity. This study demonstrates that 3D printed Ti₃C₂T_x MXene can potentially be used to create physiologically relevant cardiac patches for the treatment of MI. STATEMENT OF SIGNIFICANCE: As cardiovascular diseases and specifically myocardial infarction (MI) continue to be the leading cause of death worldwide, it is critical that new clinical interventions be developed. Tissue engineered cardiac patches have shown significant potential as clinical therapeutics to promote recovery following MI. Unfortunately, current constructs lack the ordered structure and electroconductivity of native human heart. In this study, we engineered a composite construct that can provide both conductive and topographical cues for human induced pluripotent stem cell derived cardiomyocytes. By 3D printing conductive Ti₃C₂T_x MXene in pre-designed patterns on polyethylene glycol hydrogels, using aerosol jet printing, at a cell-level resolution, we developed tissue engineered patches that have the potential for providing a new clinical therapeutic to combat cardiovascular disease.

A Prevascularized Polyurethane-Reinforced Fibrin Patch Improves Regenerative Remodeling in a Rat Right Ventricle Replacement Model

Congenital heart defects (CHDs) affect 1 in 120 newborns in the United States. Surgical repair of structural heart defects often leads to arrhythmia and increased risk of heart failure. The laboratory has previously developed an acellular fibrin patch reinforced with a biodegradable poly(ether ester urethane) urea mesh that result in improved heart function when tested in a rat right ventricle wall replacement model compared to fixed pericardium. However, this patch does not drive significant neotissue formation. The patch materials are modified here and this patch is prevascularized with human umbilical vein endothelial cells and c-Kit⁺ human amniotic fluid stem cells. Rudimentary capillary-like networks form in the fibrin after culture of cell-encapsulated patches for 3 d in vitro. Prevascularized patches and noncell loaded patch controls are implanted onto full-thickness heart wall defects created in the right ventricle of athymic nude rats. Two months after surgery, defect repair with prevascularized patches results in improved heart function and the patched heart area exhibited greater vascularization and muscularization, less fibrosis, and increased M2 macrophage infiltration compared to acellular patches.

Engineering Myocardium for Heart Regeneration-Advancements, Considerations, and Future Directions

Heart disease is the leading cause of death in the United States among both adults and infants. In adults, 5-year survival after a heart attack is <60%, and congenital heart defects are the top killer of liveborn infants. Problematically, the regenerative capacity of the heart is extremely limited, even in newborns. Furthermore, suitable donor hearts for transplant cannot meet the demand and require recipients to use immunosuppressants for life. Tissue engineered myocardium has the potential to replace dead or fibrotic heart tissue in adults and could also be used to permanently repair congenital heart defects in infants. In addition, engineering functional myocardium could facilitate the development of a whole bioartificial heart. Here, we review and compare in vitro and in situ myocardial tissue engineering strategies. In the context of this comparison, we consider three challenges that must be addressed in the engineering of myocardial tissue: recapitulation of myocardial architecture, vascularization of the tissue, and modulation of the immune system. In addition to reviewing and analyzing current progress, we recommend specific strategies for the generation of tissue engineered myocardial patches for heart regeneration and repair.

Human cardiac extracellular matrix-chitosan-gelatin composite scaffold and its endothelialization

The present study developed a cardiac extracellular matrix-chitosan-gelatin (cECM-CG) composite scaffold that can be used as a tissue-engineered heart patch and investigated its endothelialization potential by incorporating CD34⁺ endothelial progenitor cells (EPCs). The cECM-CG composite scaffold was prepared by blending cardiac extracellular matrix (cECM) with biodegradable chitosan-gelatin (CG). The mixture was lyophilized using vacuum freeze-drying. CD34⁺ EPCs were isolated and seeded on the scaffolds, and then the endothelialization effect was subsequently investigated. Effects of the scaffolds on CD34⁺ EPCs survival and proliferation were evaluated by immunofluorescence staining and MTT assay. Cell differentiation into endothelial cells and the influence of the scaffolds on cell differentiation were investigated by reverse transcription-quantitative PCR (RT-qPCR), immunofluorescence staining and tube formation assay. The present results indicated that most cells were removed after decellularization, but the main extracellular matrix components were retained. Scanning electron microscopy imaging illustrated three-dimensional and porous scaffolds. The present results suggested the cECM-CG composite scaffold had a higher water absorption ability compared with the CG scaffold. Additionally, compared with the CG scaffold, the cECM-CG composite scaffold significantly increased cell survival and proliferation, which suggested its non-toxicity and biocompatibility. Furthermore, RT-qPCR, immunofluorescence and tube formation assay results indicated that CD34⁺ EPCs differentiated into endothelial cells, and the cECM-CG composite scaffold promoted this differentiation process. In conclusion, the present results indicated that the human cECM-CG composite scaffold generated in the present study was a highly porous, biodegradable three-dimensional scaffold which supported endothelialization of seeded CD34⁺ EPCs. The present results suggested that this cECM-CG composite scaffold may be a promising heart patch for use in heart tissue engineering for congenital heart disease.

Current advances in biodegradable synthetic polymer based cardiac patches

The number of people affected by heart disease such as coronary artery disease and myocardial infarction increases at an alarming rate each year. Currently, the methods to treat these diseases are restricted to lifestyle change, pharmaceuticals, and eventually heart transplant if the condition is severe enough. While these treatment options are the standard for caring for patients who suffer from heart disease, limited regenerative ability of the heart restricts the effectiveness of treatment and may lead to other heart-related health problems in the future. Because of the increasing need for more effective therapeutic technologies for treating diseased heart tissue, cardiac patches are now a large focus for researchers. The cardiac patches are designed to be integrated into the patients' natural tissue to introduce mechanical support and healing to the damaged areas. As a promising alternative, synthetic biodegradable polymer based biomaterials can be easily manipulated to customize material properties, as well as possess certain desired characteristics for cardiac patch use. This comprehensive review summarizes recent works on synthetic biodegradable cardiac patches implanted into infarcted animal models. In addition, this review describes the basic requirements that should be met for cardiac patch development, and discusses the inspirations to designing new biomaterials and technologies for cardiac patches.

Evaluation of a polyurethane-reinforced hydrogel patch in a rat right ventricle wall replacement model

Congenital heart defects affect about 1% births in the United States. Many of the defects are treated with surgically implanted patches made from inactive materials or fixed pericardium that do not grow with the patients, leading to an increased risk of arrhythmia, sudden cardiac death, and heart failure. This study investigated an angiogenic poly(ethylene glycol) fibrin-based hydrogel reinforced with an electrospun biodegradable poly(ether ester urethane) urea (BPUR) mesh layer that was designed to encourage cell invasion, angiogenesis, and regenerative remodeling in the repair of an artificial defect created onto the rat right ventricle wall. Electrocardiogram signals were analyzed, heart function was measured, and fibrosis, macrophage infiltration, muscularization, vascularization, and defect size were evaluated at 4- and 8-weeks post-surgery. Compared with rats with fixed pericardium patches, rats with BPUR-reinforced hydrogel patches had fewer arrhythmias and greater right ventricular ejection fraction and cardiac output, as well as greater left ventricular ejection fraction, fractional shorting, stroke work and cardiac output. Histology and immunofluorescence staining showed less fibrosis and less patch material remaining in rats with BPUR-reinforced hydrogel patches at 4- and 8-weeks. Rats with BPUR-reinforced hydrogel patches also had a greater volume of granular tissue, a greater volume of muscularized tissue, more blood vessels, and a greater number of leukocytes, pan-macrophages, and M2 macrophages at 8 weeks. Overall, this study demonstrated that the engineered BPUR-reinforced hydrogel patch initiated greater regenerative vascular and muscular remodeling with a limited fibrotic response, resulting in fewer incidences of arrhythmia and improved heart function compared with fixed pericardium patches when applied to heal the defects created on the rat right ventricle wall. STATEMENT OF SIGNIFICANCE: The study tested a polyurethane-reinforced hydrogel patch in a rat right ventricle wall replacement model. Compared with fixed pericardium patches, these reinforced hydrogel patches initiated greater regenerative vascular and muscular remodeling with a reduced fibrotic response, resulting in fewer incidences of arrhythmia and improved heart function at 4- and 8-weeks post surgery. Overall, the new BPUR-reinforced hydrogel patches resulted in better heart function when replacing contractile myocardium than fixed pericardium patches.

Decellularized Extracellular Matrix Materials for Cardiac Repair and Regeneration

Decellularized extracellular matrix (dECM) is a promising biomaterial for repairing cardiovascular tissue, as dECM most effectively captures the complex array of proteins, glycosaminoglycans, proteoglycans, and many other matrix components that are found in native tissue, providing ideal cues for regeneration and repair of damaged myocardium. dECM can be used in a variety of forms, such as solid scaffolds that maintain native matrix structure, or as soluble materials that can form injectable hydrogels for tissue repair. dECM has found recent success in many regeneration and repair therapies, such as for musculoskeletal, neural, and liver tissues. This review focuses on dECM in the context of cardiovascular applications, with variations in tissue and species sourcing, and specifically discusses advances in solid and soluble dECM development, in vitro studies, in vivo implementation, and clinical translation.

Extracellular matrix hydrogel therapies: In vivo applications and development

Decellularized extracellular matrix (ECM) has been widely used for tissue engineering applications and is becoming increasingly versatile as it can take many forms, including patches, powders, and hydrogels. Following additional processing, decellularized ECM can form an inducible hydrogel that can be injected, providing for new minimally-invasive procedure opportunities. ECM hydrogels have been derived from numerous tissue sources and applied to treat many disease models, such as ischemic injuries and organ regeneration or replacement. This review will focus on in vivo applications of ECM hydrogels and functional outcomes in disease models, as well as discuss considerations for clinical translation.

STATEMENT OF SIGNIFICANCE

Extracellular matrix (ECM) hydrogel therapies are being developed to treat diseased or damaged tissues and organs throughout the body. Many ECM hydrogels are progressing from in vitro models to in vivo biocompatibility studies and functional models. There is significant potential for clinical translation of these therapies since one ECM hydrogel therapy is already in a Phase 1 clinical trial.

Electrospun Gelatin⁻Chondroitin Sulfate Scaffolds Loaded with Platelet Lysate Promote Immature Cardiomyocyte Proliferation

The aim of the present work was the development of heart patches based on gelatin (G) and chondroitin sulfate (CS) to be used as implants to improve heart recovery after corrective surgery for critical congenital heart defects (CHD). Patches were prepared by means of electrospinning to obtain nanofibrous scaffolds and they were loaded with platelet lysate (PL) as a source of growth factors to further enhance the repair process. Scaffolds were characterized for morphology and mechanical properties and for the capability to support in vitro adhesion and proliferation of dermal fibroblasts in order to assess the system’s general biocompatibility. Adhesion and proliferation of endothelial cells and cardiac cells (cardiomyocytes and cardiac fibroblasts from rat fetuses) onto PL-loaded patches was evaluated. Patches presented good elasticity and high stiffness suitable for in vivo adaptation to heart contraction. CS improved adhesion and proliferation of dermal fibroblasts, as proof of their biocompatibility. Moreover, they enhanced the adhesion and proliferation of endothelial cells, a crucial mediator of cardiac repair. Cell adhesion and proliferation could be related to elastic properties, which could favor cell motility. The presence of platelet lysate and CS was crucial for the adhesion and proliferation of cardiac cells and, in particular, of cardiomyocytes: G/CS scaffold embedded with PL appeared to selectively promote proliferation in cardiomyocytes but not cardiac fibroblasts. In conclusion, G/CS scaffold seems to be a promising system to assist myocardial-repair processes in young patient, preserving cardiomyocyte viability and preventing cardiac fibroblast proliferation, likely reducing subsequent uncontrolled collagen deposition by fibroblasts following repair.

PVA/Dextran hydrogel patches as delivery system of antioxidant astaxanthin: a cardiovascular approach

After myocardial infarction, the heart's mechanical properties and its intrinsic capability to recover are compromised. To improve this recovery, several groups have developed cardiac patches based on different biomaterials strategies. Here, we developed polyvinylalcohol/dextran (PVA/Dex) elastic hydrogel patches, obtained through the freeze thawing (FT) process, with the aim to deliver locally a potent natural antioxidant molecule, astaxanthin, and to assist the heart's response against the generated myofibril stress. Extensive rheological and dynamo-mechanical characterization of the effect of the PVA molecular weight, number of freeze-thawing cycles and Dex addition on the mechanical properties of the resulting hydrogels, were carried out. Hydrogel systems based on PVA 145 kDa and PVA 47 kDa blended with Dex 40 kDa, were chosen as the most promising candidates for this application. In order to improve astaxanthin solubility, an inclusion system using hydroxypropyl-β-cyclodextrin was prepared. This system was posteriorly loaded within the PVA/Dex hydrogels. PVA145/Dex 1FT and PVA47/Dex 3FT showed the best rheological and mechanical properties when compared to the other studied systems; environmental scanning electron microscope and confocal imaging evidenced a porous structure of the hydrogels allowing astaxanthin release. In vitro cellular behavior was analyzed after 24 h of contact with astaxanthin-loaded hydrogels. In vivo subcutaneous biocompatibility was performed in rats using PVA145/Dex 1FT, as the best compromise between mechanical support and astaxanthin delivery. Finally, ex vivo and in vivo experiments showed good mechanical and compatibility properties of this hydrogel. The obtained results showed that the studied materials have a potential to be used as myocardial patches to assist infarcted heart mechanical function and to reduce oxidative stress by the in situ release of astaxanthin.

Biomimetic Artificial Basilar Membranes for Next-Generation Cochlear Implants

Patients with sensorineural hearing loss can recover their hearing using a cochlear implant (CI). However, there is a need to develop next-generation CIs to overcome the limitations of conventional CIs caused by extracorporeal devices. Recently, artificial basilar membranes (ABMs) are actively studied for next-generation CIs. The ABM is an acoustic transducer that mimics the mechanical frequency selectivity of the BM and acoustic-to-electrical energy conversion of hair cells. This paper presents recent progress in biomimetic ABMs. First, the characteristics of frequency selectivity of the ABMs by the trapezoidal membrane and beam array are addressed. Second, to reflect the latest research of energy conversion technologies, ABMs using various piezoelectric materials and triboelectric-based ABMs are discussed. Third, in vivo evaluations of the ABMs in animal models are discussed according to the target position for implantation. Finally, future perspectives of ABM studies for the development of practical hearing devices are discussed.