Chronological adhesive cardiac patch for synchronous mechanophysiological monitoring and electrocoupling therapy

A biodegradable, microstructured, electroconductive and nano-integrated drug eluting patch (MENDEP) for myocardial tissue engineering

We produced a microstructured, electroconductive and nano-functionalized drug eluting cardiac patch (MENDEP) designed to attract endogenous precursor cells, favor their differentiation and counteract adverse ventricular remodeling in situ. MENDEP showed mechanical anisotropy and biaxial strength comparable to porcine myocardium, reduced impedance, controlled biodegradability, molecular recognition ability and controlled drug release activity. In vitro, cytocompatibility and cardioinductivity were demonstrated. Migration tests showed the chemoattractive capacity of the patches and conductivity assays showed unaltered cell-cell interactions and cell beating synchronicity. MENDEP was then epicardially implanted in a rat model of ischemia/reperfusion (I/R). Histological, immunofluorescence and biomarker analysis indicated that implantation did not cause damage to the healthy myocardium. After I/R, MENDEP recruited precursor cells into the damaged myocardium and triggered their differentiation towards the vascular lineage. Under the patch, the myocardial tissue appeared well preserved and cardiac gap junctions were correctly distributed at the level of the intercalated discs. The fibrotic area measured in the I/R group was partially reduced in the patch group. Overall, these results demonstrate that MENDEP was fully retained on the epicardial surface of the left ventricle over 4-week implantation period, underwent progressive vascularization, did not perturb the healthy myocardium and showed great potential in repairing the infarcted area.

Engineering functional electroconductive hydrogels for targeted therapy in myocardial infarction repair

Myocardial infarction (MI) is characterized by a paucity of cardiomyocyte regeneration, leading to significant morbidity and mortality. Contemporary therapeutic modalities, while mitigating ischemic effects, fail to reconstitute the impaired electromechanical coupling within the infracted myocardium. Emerging evidence supports the utility of electroconductive hydrogels (ECHs) in facilitating post-MI cardiac function recovery by restoring the conductive microenvironment of the infarcted tissue. This comprehensive review delineates the taxonomy of ECHs predicated on their constituent conductive materials. It also encapsulates prevailing research trends in ECH-mediated MI repair, encompassing innovative design paradigms and microenvironment-sensitive strategies. The review also provides a critical appraisal of various implantation techniques, underscored by a thorough examination of the attendant considerations. It elucidates the mechanistic underpinnings by which hydrogels exert salutary effects on myocardial repair, namely by augmenting mechanical and electrical integrity, exerting anti-inflammatory actions, fostering angiogenesis, and curtailing adverse remodeling processes. Furthermore, the review engages with the pressing challenge of optimizing ECH functionality to achieve superior reparative outcomes post-MI. The discourse concludes with an anticipatory perspective on the evolution of ECH scaffolds, advocating for a tailored approach that integrates multifaceted physicochemical properties to cater to the nuances of personalized medicine.

Velcro-Inspired Poly(ethylene glycol) Gel (PEGgel) for Robust Interface Adhesion Between Hydrogel, Device, and Tissue

Hydrogel bioadhesive is widely used in tissue engineering, flexible electronics, and other fields because of its mechanical softness and good biocompatibility. However, due to the differences in the mechanical strength of various biological tissues, the mechanical properties of specific hydrogel bioadhesives are difficult to easily adjust to adapt to different tissue strengths. Here, we propose a poly(methacrylamide-polyethylene glycol-N-hydroxysuccinimide ester-co-acrylic acid) PEGgel (MAP) bioadhesive based on the drying cross-linking mechanism and a polymer platform with PEG as the solvent. Compared with the reported hydrogel adhesives, MAP can adjust the tensile strength from 130 kPa to 1 MPa and the fracture strain from 149% to 2653% by modifying the molecular weight and proportion of solvent PEG. It also exhibits robust adhesion to tissues and various substrates, with its shear strength on pigskin and glass reaching 130 kPa and 6.8 MPa, respectively. The application of MAP for tendon healing and movement monitoring demonstrates the tough and compliant adhesion between hydrogel, device, and tissues. Combined with long-term storage capability, 3D-printable ability, self-healing ability, and biocompatibility, MAP represents a promising approach for the development of bioadhesives.

Highly Conductive, Adhesive and Biocompatible Hydrogel for Closed-Loop Neuromodulation in Nerve Regeneration

Developing conductive hydrogels has led to significant advancements in bioelectronics, especially in the realms of neural interfacing and neuromodulation. Despite this progress, the synthesis of hydrogels that simultaneously exhibit superior mechanical stretchability, robust bioadhesion, and high conductivity remains a significant challenge. Traditional approaches often resort to high filler concentrations to achieve adequate electrical conductivity, which detrimentally affects the hydrogel's mechanical integrity and biocompatibility. In this study, we present a multifunctional conductive hydrogel, designated as PAACP, which is engineered from a polyacrylamide-poly(acrylic acid) (PAM-PAA) matrix and enhanced with polydopamine-modified carbon nanotubes (CNT-PDA). This composition ensures an exceptional conductivity of 9.52 S/m with a remarkably low carbon nanotube content of merely 0.33 wt %. The hydrogel exhibits excellent mechanical properties, including low tensile modulus (∼100 kPa), high stretchability (∼1000%), and high toughness (7.33 kJ m-2). Moreover, the synergistic action of catechol and NHS ester functional groups provides strong tissue adhesive strength (107.14 kPa), ensuring stable bioelectronic-neural interfaces. As a cuff electrode, it enables suture-free implantation and bidirectional electrical communication with the sciatic nerve, which is essential for neuromodulation. Leveraging these capabilities, our hydrogel is integrated into a closed-loop system for sciatic nerve repair, significantly enhancing real-time feedback driven nerve regeneration and accelerating functional recovery. This work offers a strategy for dynamic, personalized neuromodulation in nerve repair and clinical applications.

Bioelectric and physicochemical foundations of bioelectronics in tissue regeneration

Understanding and exploiting bioelectric signaling pathways and physicochemical properties of materials that interface with living tissues is central to advancing tissue regeneration. In particular, the emerging field of bioelectronics leverages these principles to develop personalized, minimally invasive therapeutic strategies tailored to the dynamic demands of individual patients. By integrating sensing and actuation modules into flexible, biocompatible devices, clinicians can continuously monitor and modulate local electrical microenvironments, thereby guiding regenerative processes without extensive surgical interventions. This review provides a critical examination of how fundamental bioelectric cues and physicochemical considerations drive the design and engineering of next-generation bioelectronic platforms. These platforms not only promote the formation and maturation of new tissues across neural, cardiac, musculoskeletal, skin, and gastrointestinal systems but also precisely align therapies with the unique structural, functional, and electrophysiological characteristics of each tissue type. Collectively, these insights and innovations represent a convergence of biology, electronics, and materials science that holds tremendous promise for enhancing the efficacy, specificity, and long-term stability of regenerative treatments, ushering in a new era of advanced tissue engineering and patient-centered regenerative medicine.

Hydrogel tissue adhesive: Adhesion strategy and application

Hydrogel tissue adhesives have emerged as a promising alternative to conventional wound closure methods such as sutures and staples due to their operational simplicity demonstrated biocompatibility and capacity for multifunctional integration. However, complex and variable tissue microenvironments and dynamic adhesion surfaces still challenge the actual adhesion performance of adhesives, especially natural polymer-based adhesives. In addition, to expand the application of adhesives in biomedical fields, there is an urgent need to further improve tissue adhesion performance through composition design, adhesion mechanism research and bioeffect development. This review focuses on the adhesive properties of adhesives and their applications in biomedical fields. Adhesion-cohesion equilibria, forms of adhesion failure, methods for improving cohesion and various interfacial adhesion mechanisms are presented. Moreover, practical biomedical applications of tissue adhesives are reviewed, focusing on skin, heart, stomach, liver, and cornea. Finally, this review looks ahead to a new generation of multi-functional, strong adhesion tissue adhesives, in the hope of providing inspiration to those working in the field.

Recent Progress of Soft and Bioactive Materials in Flexible Bioelectronics

Materials that establish functional, stable interfaces to targeted tissues for long-term monitoring/stimulation equipped with diagnostic/therapeutic capabilities represent breakthroughs in biomedical research and clinical medicine. A fundamental challenge is the mechanical and chemical mismatch between tissues and implants that ultimately results in device failure for corrosion by biofluids and associated foreign body response. Of particular interest is in the development of bioactive materials at the level of chemistry and mechanics for high-performance, minimally invasive function, simultaneously with tissue-like compliance and in vivo biocompatibility. This review summarizes the most recent progress for these purposes, with an emphasis on material properties such as foreign body response, on integration schemes with biological tissues, and on their use as bioelectronic platforms. The article begins with an overview of emerging classes of material platforms for bio-integration with proven utility in live animal models, as high performance and stable interfaces with different form factors. Subsequent sections review various classes of flexible, soft tissue-like materials, ranging from self-healing hydrogel/elastomer to bio-adhesive composites and to bioactive materials. Additional discussions highlight examples of active bioelectronic systems that support electrophysiological mapping, stimulation, and drug delivery as treatments of related diseases, at spatiotemporal resolutions that span from the cellular level to organ-scale dimension. Envisioned applications involve advanced implants for brain, cardiac, and other organ systems, with capabilities of bioactive materials that offer stability for human subjects and live animal models. Results will inspire continuing advancements in functions and benign interfaces to biological systems, thus yielding therapy and diagnostics for human healthcare.

Materials Advances in Devices for Heart Disease Interventions

Heart disease encompasses a range of conditions that affect the heart, including coronary artery disease, arrhythmias, congenital heart defects, heart valve disease, and conditions that affect the heart muscle. Intervention strategies can be categorized according to when they are administered and include: 1) Monitoring cardiac function using sensor technology to inform diagnosis and treatment, 2) Managing symptoms by restoring cardiac output, electrophysiology, and hemodynamics, and often serving as bridge-to-recovery or bridge-to-transplantation strategies, and 3) Repairing damaged tissue, including myocardium and heart valves, when management strategies are insufficient. Each intervention approach and technology require specific material properties to function optimally, relying on materials that support their action and interface with the body, with new technologies increasingly depending on advances in materials science and engineering. This review explores material properties and requirements driving innovation in advanced intervention strategies for heart disease and highlights key examples of recent progress in the field driven by advances in materials research.

Flexible Patterned Fuel Cell Patches Stimulate Nerve and Myocardium Restoration

The distribution of electrical potentials and current in exogenous electrostimulation has significant impacts on its effectiveness in promoting tissue repair. However, there is still a lack of a flexible, implantable power source capable of generating customizable patterned electric fields for in situ electrostimulation(electrical stimulation). Herein, this study reports a fuel cell patch (FCP) that can provide in situ electrostimulation and a hypoxic microenvironment to promote tissue repair synergistically. Stable and highly efficient PtNi nanochains and PtNi nanocages electrocatalysts with anti-interference properties catalyze glucose oxidation and oxygen reduction respectively in an encapsulation-free fuel cell. The laser-induced graphene (LIG) electrode loaded with PtNi electrocatalysts is transferred to the surface of a flexible chitosan hydrogel. The resulting flexible FCP can adapt to tissues with different morphologies, firmly adhere to prevent suturing, and provide potent electrostimulation (0.403 V, 51.55 µW cm-2). Additionally, it consumes oxygen in situ to create a hypoxic microenvironment, increasing the expression of hypoxia-inducible factor-1α (HIF-1α). Based on the different pattern requirements of exogenous electrostimulation during the repair of various types of tissue, an axial FCP for peripheral nerves and a flower-patterned FCP for myocardial tissue are constructed and transplanted into animals, showing significant tissue repair in both models.

Tissue-Adaptable Hydrogel for Mechanically Compliant Bioelectronic Interfaces

A hydrogel with tissue-like softness and ideal biocompatibility has emerged as a promising candidate for bioelectronics, especially in bidirectional bioelectrical transduction and communication. Conformal standardized hydrogel biointerfaces are in urgent demand to bridge electronic devices and irregular tissue surfaces. Herein, we presented a shape-adaptative electroactive hydrogel with tissue-adapted conductivity (≈1.03 S/m) by precisely regulating molecular chains and polymer networks of multisource gelatin at the molecular scale. Local amine-carboxylate electrostatic domains formed by ion interactions between gelatin and sodium citrate significantly enhance the physiological adaptability and regulate the biodegradation period. Benefiting from the reversible fluid-gel transition property, the hydrogel can be in situ gelatinized and establish a dynamic compliance bioelectronic interface with tissues by chemical bonding and the physical topological effect. Further, the mechanical-electrical coupling capacity of the hydrogel interface allows for bioelectrical conduction function reconstruction and electrical stimulation therapy after mechanical bridging at tissue defects to boost tissue regeneration and sensory restoration.

A Bioinspired Defect-Tolerant Hydrogel Medical Patch for Abdominal Wall Defect Repair

Point-wise suturing is the standard method for ensuring that patches effectively perform mechanically supportive functions in tissue repair. However, stress concentrations around suture holes can compromise the mechanical stability of patches. In this study, we develop a suturable hydrogel patch with flaw-tolerance capabilities by leveraging multiscale stress deconcentration, inspired by natural silk. This design mitigates stress concentration across two scales through the synergistic integration of nanoscale high-energy crystalline domains and intermolecular interactions. The resulting integral hydrogel patch exhibits superior flaw resistance compared to conventional patches and effectively addresses tissue adhesion issues. To validate the efficacy of the patch, we demonstrate successful in vivo repair of abdominal wall defects in rats, comparing the performance of the proposed patch to commercial mesh patches (Prolene). The integral patch design strategy present here offers a valuable approach for developing patches that can be tailored to meet the mechanical support needs of various tissue repair applications.

Adhesive and Conductive Hydrogels for the Treatment of Myocardial Infarction

Myocardial infarction (MI) is a leading cause of mortality among cardiovascular diseases. Following MI, the damaged myocardium is progressively being replaced by fibrous scar tissue, which exhibits poor electrical conductivity, ultimately resulting in arrhythmias and adverse cardiac remodeling. Due to their extracellular matrix-like structure and excellent biocompatibility, hydrogels are emerging as a focal point in cardiac tissue engineering. However, traditional hydrogels lack the necessary conductivity to restore electrical signal transmission in the infarcted regions. Imparting conductivity to hydrogels while also enhancing their adhesive properties enables them to adhere closely to myocardial tissue, establish stable electrical connections, and facilitate synchronized contraction and myocardial tissue repair within the infarcted area. This paper reviews the strategies for constructing conductive and adhesive hydrogels, focusing on their application in MI repair. Furthermore, the challenges and future directions in developing adhesive and conductive hydrogels for MI repair are discussed.

Flexible circuit-free system via passive modulated ultrasound for wireless thoracic pressure monitoring

Implantable medical devices (IMDs) provide effective medical solutions for diverse health care applications. Electrical circuits are crucial for implantable devices due to the requirement of intended functions, such as communication with external devices. Circuits have several risks, such as biocompatibility issues, power limitations, or size constraints. In this work, we propose a passive modulated ultrasound (PMU) principle for IMDs and develop a circuit-free ultrasonic system (CUS) for thoracic pressure monitoring. The PMU principle can passively modulate monitored physiological signals into ultrasound pulses without using electrical circuits or power supply. The size of the developed CUS is only 2.5 millimeters in radius and 850 micrometers in height. Animal experiments demonstrated that the CUS, with a high sensitivity (-22.96 millivolts per kilopascal), can monitor thoracic pressure to assist in diagnosing different heart diseases, including cardiac arrest and myocardial infarction. The PMU provides a human-friendly wireless sensing and communication strategy for IMDs, which promotes advancements in health care applications within the human body.

Flexible Electronic Patch Utilizing Gelatin Film for Heart and Brain Signal Detection

Flexible electronic patches have been widely studied in various fields. However, they still face serious challenges in cardio-brain signaling monitoring to achieve accurate adhesion and detection with compatibility in mildly humid environments. To tackle these challenges, we engineered a gelatin hydrogel film cross-linked with a biocompatible matrix factor and combined it with a blend of liquid metal and PVP to create the flexible electronic patch. The flexible patch has good biocompatibility and fatigue resistance due to the incorporation of liquid metal and natural gelatin, with the conductivity of liquid metal and minimal toxicity of the gelatin film. It is possible to securely insert it into the body for a duration of 3 weeks while maintaining monitoring functionality and withstanding 10 000 cycles of flexural fatigue. This research provides an innovative approach to the future advancement of flexible electronic patches.

Multifunctional Adhesive Hydrogels: From Design to Biomedical Applications

Adhesive hydrogels characterized by structural properties similar to the extracellular matrix, excellent biocompatibility, controlled degradation, and tunable mechanical properties have demonstrated significant potential in biomedical applications, including tissue engineering, biosensors, and drug delivery systems. These hydrogels exhibit remarkable adhesion to target substrates and can be rationally engineered to meet specific requirements. In recent decades, adhesive hydrogels have experienced significant advancements driven by the introduction of numerous multifunctional design strategies. This review initially summarizes the chemical bond-based design strategies for tissue adhesion, encompassing static covalent bonds, dynamic covalent bonds, and non-covalent interactions. Subsequently, the multiple functionalities imparted by these diverse design strategies, including highly stretchable and tough performances, responsiveness to microenvironments, anti-freezing/heating properties, conductivity, antibacterial activity, and hemostatic properties are discussed. In addition, recent advances in the biomedical applications of adhesive hydrogels, focusing on tissue repair, drug delivery, medical devices, and wearable sensors are reviewed. Finally, the current challenges are highlighted and future trends in this rapidly evolving field are discussed.

Design Strategy, On-Demand Control, and Biomedical Engineering Applications of Wet Adhesion

The adhesion of tissues to external devices is fundamental to numerous critical applications in biomedical engineering, including tissue and organ repair, bioelectronic interfaces, adhesive robotics, wearable electronics, biomedical sensing and actuation, as well as medical monitoring, treatment, and healthcare. A key challenge in this context is that tissues are typically situated in aqueous and dynamic environments, which poses a bottleneck to further advancements in these fields. Wet adhesion technology (WAT) presents an effective solution to this issue. In this review, we summarize the three major design strategies and control methods of wet adhesion, comprehensively and systematically introducing the latest applications and advancements of WAT in the field of biomedical engineering. First, single adhesion mechanism under the frameworks of the three design strategies is systematically introduced. Second, control methods for adhesion are comprehensively summarized, including spatiotemporal control, detachment control, and reversible adhesion control. Third, a systematic summary and discussion of the latest applications of WAT in biomedical engineering research and education were presented, with a particular focus on innovative applications such as tissue-electronic interface devices, ingestible devices, end-effector components, in vivo medical microrobots, and medical instruments and equipment. Finally, opportunities and challenges encountered in the design and development of wet adhesives with advanced adhesive performance and application prospects are discussed.

Hydrogels in wearable neural interfaces

The integration of wearable neural interfaces (WNIs) with the human nervous system has marked a significant progression, enabling progress in medical treatments and technology integration. Hydrogels, distinguished by their high-water content, low interfacial impedance, conductivity, adhesion, and mechanical compliance, effectively address the rigidity and biocompatibility issues common in traditional materials. This review highlights their important parameters-biocompatibility, interfacial impedance, conductivity, and adhesiveness-that are integral to their function in WNIs. The applications of hydrogels in wearable neural recording and neurostimulation are discussed in detail. Finally, the opportunities and challenges faced by hydrogels for WNIs are summarized and prospected. This review aims to offer a thorough examination of hydrogel technology's present landscape and to encourage continued exploration and innovation. As developments progress, hydrogels are poised to revolutionize wearable neural interfaces, offering significant enhancements in healthcare and technological applications.

Graphical Abstract

Phage probe on RAFT polymer surface for rapid enumeration of E. coli K12

This study presents a simple, fast, and sensitive label-free sensing assay for the precise enumeration of modeled pathogenic Escherichia coli K12 (E. coli K12) bacteria for the first time. The method employs the covalent binding bacteriophage technique on the surface of a reversible addition-fragmentation chain transfer (RAFT) polymer film. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) identified the charge transfer resistance Rct was calculated from a suitable electrochemical circuit model through an evaluation of the relevant parameter after the immobilization of the bacteriophage and the binding of specific E. coli K12. The impedimetric biosensor reveals specific and reproducible detection with sensitivity in the linear working range of 104.2-107.0 CFU/mL, a limit of detection (LOD) of 101.3 CFU/mL, and a short response time of 15 min. The SERS response validates the surface roughness and interaction of the SERS-tag with E. coli K12-modified electrodes. Furthermore, the covalently immobilized active phage selectivity was proved against various non-targeting bacterial strains in the presence of targeted E.coli K12 with a result of 94 % specificity and 98 % sensitivity. Therefore, the developed phage-based electrode surface can be used as a disposable, label-free impedimetric biosensor for rapid and real-time monitoring of serum samples.

Electroactive Nanomaterials for the Prevention and Treatment of Heart Failure: From Materials and Mechanisms to Applications

Heart failure (HF) represents a cardiovascular disease that significantly threatens global well-being and quality of life. Electroactive nanomaterials, characterized by their distinctive physical and chemical properties, emerge as promising candidates for HF prevention and management. This review comprehensively examines electroactive nanomaterials and their applications in HF intervention. It presents the definition, classification, and intrinsic characteristics of conductive, piezoelectric, and triboelectric nanomaterials, emphasizing their mechanical robustness, electrical conductivity, and piezoelectric coefficients. The review elucidates their applications and mechanisms: 1) early detection and diagnosis, employing nanomaterial-based sensors for real-time cardiac health monitoring; 2) cardiac tissue repair and regeneration, providing mechanical, chemical, and electrical stimuli for tissue restoration; 3) localized administration of bioactive biomolecules, genes, or pharmacotherapeutic agents, using nanomaterials as advanced drug delivery systems; and 4) electrical stimulation therapies, leveraging their properties for innovative pacemaker and neurostimulation technologies. Challenges in clinical translation, such as biocompatibility, stability, and scalability, are discussed, along with future prospects and potential innovations, including multifunctional and stimuli-responsive nanomaterials for precise HF therapies. This review encapsulates current research and future directions concerning the use of electroactive nanomaterials in HF prevention and management, highlighting their potential to innovating in cardiovascular medicine.

A Multifunctional Anisotropic Patch Manufactured by Microfluidic Manipulation for the Repair of Infarcted Myocardium

Engineered hydrogel patches have shown promising therapeutic effects in the treatment of myocardial infarction (MI), especially anisotropic patches that mimic the characteristics of native myocardium have attracted widespread attention. However, it remains a great challenge to develop cardiac patches with long-range and orderly electrical conduction based on an effective, mild, and rapid strategy. Here, a multifunctional anisotropic cardiac patch is presented based on microfluidic manipulation. The anisotropic alginate-gelatin methacrylate hydrogel patches are easily and rapidly prepared through microfluidic focusing, ion-photocrosslinking, and parallel packing processes. The fluid-based anisotropic realization process does not involve complex machining and strong field stimulation and is compatible with the loading of macromolecular biological agents. The anisotropic hydrogel patch can mimic the anisotropy of the myocardium and guide the directional polarization of cardiomyocytes. In animal model experiments, it also exhibits significant effects in inhibiting ventricular remodeling, fibrosis, and enhancing cardiac function recovery after MI. These comprehensive features make the multifunctional hydrogel patch a promising candidate for cardiac tissue repair and future provide a new paradigm for expanding microfluidic technology to solve tissue engineering challenges.

Advances in Biointegrated Wearable and Implantable Optoelectronic Devices for Cardiac Healthcare

With the prevalence of cardiovascular disease, it is imperative that medical monitoring and treatment become more instantaneous and comfortable for patients. Recently, wearable and implantable optoelectronic devices can be seamlessly integrated into human body to enable physiological monitoring and treatment in an imperceptible and spatiotemporally unconstrained manner, opening countless possibilities for the intelligent healthcare paradigm. To achieve biointegrated cardiac healthcare, researchers have focused on novel strategies for the construction of flexible/stretchable optoelectronic devices and systems. Here, we overview the progress of biointegrated flexible and stretchable optoelectronics for wearable and implantable cardiac healthcare devices. Firstly, the device design is addressed, including the mechanical design, interface adhesion, and encapsulation strategies. Next, the practical applications of optoelectronic devices for cardiac physiological monitoring, cardiac optogenetics, and nongenetic stimulation are presented. Finally, an outlook on biointegrated flexible and stretchable optoelectronic devices and systems for intelligent cardiac healthcare is discussed.

Orbit symmetry breaking in MXene implements enhanced soft bioelectronic implants

Bioelectronic implants featuring soft mechanics, excellent biocompatibility, and outstanding electrical performance hold promising potential to revolutionize implantable technology. These biomedical implants can record electrophysiological signals and execute direct therapeutic interventions within internal organs, offering transformative potential in the diagnosis, monitoring, and treatment of various pathological conditions. However, challenges remain in improving excessive impedance at the bioelectronic-tissue interface and thus the efficacy of electrophysiological signaling and intervention. Here, we devise orbit symmetry breaking in MXene (a low-cost scalability, biocompatible, and conductive two dimensionally layered material, which we refer to as OBXene), which exhibits low bioelectronic-tissue impedance, originating from the out-of-plane charge transfer. Furthermore, the Schottky-induced piezoelectricity stemming from the asymmetric orbital configuration of OBXene facilitates interlayered charge transport in the device. We report an OBXene-based cardiac patch applied on the left ventricular epicardium of both rodent and porcine models to enable spatiotemporal epicardium mapping and pacing while coupling the wireless and battery-free operation for long-term real-time recording and closed-loop stimulation.

3D printed multi-coupled bioinspired skin-electronic interfaces with enhanced adhesion for monitoring and treatment

Skin-electronic interfaces have broad applications in fields such as diagnostics, therapy, health monitoring, and smart wearables. However, they face various challenges in practical use. For instance, in wet environments, the cohesion of the material may be compromised, and under dynamic conditions, maintaining conformal adhesion becomes difficult, leading to reduced sensitivity and fidelity of electrical signal transmission. The key scientific issue lies in forming a stable and tight mechanical-electronic coupling at the tissue-electronic interface. Here, inspired by octopus sucker structures and snail mucus, we propose a strategy for hydrogel skin-electronic interfaces based on multi-coupled bioinspired adhesion and introduce an ultrasound (US)-mediated interfacial toughness enhancement mechanism. Ultimately, using digital light processing micro-nano additive manufacturing technology (DLP 3D), we have developed a multifunctional, diagnostic-therapeutic integrated patch (PAMS). This patch exhibits moderate water swelling properties, a maximum deformation of up to 460%, high sensitivity (GF = 4.73), and tough and controllable bioadhesion (shear strength increased by 109.29%). Apart from outstanding mechanical and electronic properties, the patch also demonstrates good biocompatibility, anti-bacterial properties, photothermal properties, and resistance to freezing at -20 °C. Experimental results show that this skin-electronic interface can sensitively monitor temperature, motion, and electrocardiogram signals. Utilizing a rat frostbite model, we have demonstrated that this skin-electronic interface can effectively accelerate the wound healing process as a wound patch. This research offers a promising strategy for improving the performance of bioelectronic devices, sensor-based educational reforms and personalized diagnostics and therapeutics in the future. STATEMENT OF SIGNIFICANCE: Establishing stable and tight mechanical-electronic coupling at the tissue-electronic interface is essential for the diverse applications of bioelectronic devices. This study aims to develop a multifunctional, diagnostic-therapeutic integrated hydrogel skin-electronic interface patch with enhanced interfacial toughness. The patch is based on a multi-coupled bioinspired adhesive-enhanced mechanism, allowing for personalized 3D printing customization. It can be used as a high-performance diagnostic-therapeutic sensor and effectively promote frostbite wound healing. We anticipate that this research will provide new insights for constructing the next generation of multifunctional integrated high-performance bioelectronic interfaces.

Soft Bioelectronics for Heart Monitoring

Cardiovascular diseases (CVDs) are a predominant global health concern, accounting for over 17.9 million deaths in 2019, representing approximately 32% of all global fatalities. In North America and Europe, over a million adults undergo cardiac surgeries annually. Despite the benefits, such surgeries pose risks and require precise postsurgery monitoring. However, during the postdischarge period, where monitoring infrastructures are limited, continuous monitoring of vital signals is hindered. In this area, the introduction of implantable electronics is altering medical practices by enabling real-time and out-of-hospital monitoring of physiological signals and biological information postsurgery. The multimodal implantable bioelectronic platforms have the capability of continuous heart sensing and stimulation, in both postsurgery and out-of-hospital settings. Furthermore, with the emergence of machine learning algorithms into healthcare devices, next-generation implantables will benefit artificial intelligence (AI) and connectivity with skin-interfaced electronics to provide more precise and user-specific results. This Review outlines recent advancements in implantable bioelectronics and their utilization in cardiovascular health monitoring, highlighting their transformative deployment in sensing and stimulation to the heart toward reaching truly personalized healthcare platforms compatible with the Sustainable Development Goal 3.4 of the WHO 2030 observatory roadmap. This Review also discusses the challenges and future prospects of these devices.

Introductory Review of Soft Implantable Bioelectronics Using Conductive and Functional Hydrogels and Hydrogel Nanocomposites

Interfaces between implantable bioelectrodes and tissues provide critical insights into the biological and pathological conditions of targeted organs, aiding diagnosis and treatment. While conventional bioelectronics, made from rigid materials like metals and silicon, have been essential for recording signals and delivering electric stimulation, they face limitations due to the mechanical mismatch between rigid devices and soft tissues. Recently, focus has shifted toward soft conductive materials, such as conductive hydrogels and hydrogel nanocomposites, known for their tissue-like softness, biocompatibility, and potential for functionalization. This review introduces these materials and provides an overview of recent advances in soft hydrogel nanocomposites for implantable electronics. It covers material strategies for conductive hydrogels, including both intrinsically conductive hydrogels and hydrogel nanocomposites, and explores key functionalization techniques like biodegradation, bioadhesiveness, injectability, and self-healing. Practical applications of these materials in implantable electronics are also highlighted, showcasing their effectiveness in real-world scenarios. Finally, we discuss emerging technologies and future needs for chronically implantable bioelectronics, offering insights into the evolving landscape of this field.

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.

Highly-stable, injectable, conductive hydrogel for chronic neuromodulation

Electroceuticals, through the selective modulation of peripheral nerves near target organs, are promising for treating refractory diseases. However, the small sizes and the delicate nature of these nerves present challenges in simplifying the fixation and stabilizing the electrical-coupling interface for neural electrodes. Herein, we construct a robust neural interface for fine peripheral nerves using an injectable bio-adhesive hydrogel bioelectronics. By incorporating a multifunctional molecular regulator during network formation, we optimize the injectability and conductivity of the hydrogel through fine-tuning reaction kinetics and multi-scale interactions within the conductive network. Meanwhile, the mechanical and electrical stability of the hydrogel is achieved without compromising its injectability. Minimal tissue damage along with low and stable impedance of the injectable neural interface enables chronic vagus neuromodulation for myocardial infarction therapy in the male rat model. Our highly-stable, injectable, conductive hydrogel bioelectronics are readily available to target challenging anatomical locations, paving the way for future precision bioelectronic medicine.

Temporal modulation of inflammation and chondrogenesis through dendritic nanoparticle-mediated therapy with diclofenac surface modification and strontium ion encapsulation

Cartilage tissue engineering holds great promise for efficient cartilage regeneration. However, early inflammatory reactions to seed cells and/or scaffolds impede this process. Consequently, managing inflammation is of paramount importance. Moreover, due to the body's restricted chondrogenic capacity, inducing cartilage regeneration becomes imperative. Thus, a controlled platform is essential to establish an anti-inflammatory microenvironment before initiating the cartilage regeneration process. In this study, we utilized fifth-generation polyamidoamine dendrimers (G5) as a vehicle for drugs to create composite nanoparticles known as G5-Dic/Sr. These nanoparticles were generated by surface modification with diclofenac (Dic), known for its potent anti-inflammatory effects, and encapsulating strontium (Sr), which effectively induces chondrogenesis, within the core. Our findings indicated that the G5-Dic/Sr nanoparticle exhibited selective Dic release during the initial 9 days and gradual Sr release from days 3 to 15. Subsequently, these nanoparticles were incorporated into a gelatin methacryloyl (GelMA) hydrogel, resulting in GelMA@G5-Dic/Sr. In vitro assessments demonstrated GelMA@G5-Dic/Sr's biocompatibility with bone marrow stem cells (BMSCs). The enclosed nanoparticles effectively mitigated inflammation in lipopolysaccharide-induced RAW264.7 macrophages and significantly augmented chondrogenesis in BMSCs cocultures. Implanting BMSCs-loaded GelMA@G5-Dic/Sr hydrogels in immunocompetent rabbits for 2 and 6 weeks revealed diminished inflammation and enhanced cartilage formation compared to GelMA, GelMA@G5, GelMA@G5-Dic, and GelMA@G5/Sr hydrogels. Collectively, this study introduces an innovative strategy to advance cartilage regeneration by temporally modulating inflammation and chondrogenesis in immunocompetent animals. Through the development of a platform addressing the temporal modulation of inflammation and the limited chondrogenic capacity, we offer valuable insights to the field of cartilage tissue engineering.

Recent Advances of Stretchable Nanomaterial-Based Hydrogels for Wearable Sensors and Electrophysiological Signals Monitoring

Electrophysiological monitoring is a commonly used medical procedure designed to capture the electrical signals generated by the body and promptly identify any abnormal health conditions. Wearable sensors are of great significance in signal acquisition for electrophysiological monitoring. Traditional electrophysiological monitoring devices are often bulky and have many complex accessories and thus, are only suitable for limited application scenarios. Hydrogels optimized based on nanomaterials are lightweight with excellent stretchable and electrical properties, solving the problem of high-quality signal acquisition for wearable sensors. Therefore, the development of hydrogels based on nanomaterials brings tremendous potential for wearable physiological signal monitoring sensors. This review first introduces the latest advancement of hydrogels made from different nanomaterials, such as nanocarbon materials, nanometal materials, and two-dimensional transition metal compounds, in physiological signal monitoring sensors. Second, the versatile properties of these stretchable composite hydrogel sensors are reviewed. Then, their applications in various electrophysiological signal monitoring, such as electrocardiogram monitoring, electromyographic signal analysis, and electroencephalogram monitoring, are discussed. Finally, the current application status and future development prospects of nanomaterial-optimized hydrogels in wearable physiological signal monitoring sensors are summarized. We hope this review will inspire future development of wearable electrophysiological signal monitoring sensors using nanomaterial-based hydrogels.

Flexible Conformally Bioadhesive MXene Hydrogel Electronics for Machine Learning-Facilitated Human-Interactive Sensing

Wearable epidermic electronics assembled from conductive hydrogels are attracting various research attention for their seamless integration with human body for conformally real-time health monitoring, clinical diagnostics and medical treatment, and human-interactive sensing. Nevertheless, it remains a tremendous challenge to simultaneously achieve conformally bioadhesive epidermic electronics with remarkable self-adhesiveness, reliable ultraviolet (UV) protection ability, and admirable sensing performance for high-fidelity epidermal electrophysiological signals monitoring, along with timely photothermal therapeutic performances after medical diagnostic sensing, as well as efficient antibacterial activity and reliable hemostatic effect for potential medical therapy. Herein, a conformally bioadhesive hydrogel-based epidermic sensor, featuring superior self-adhesiveness and excellent UV-protection performance, is developed by dexterously assembling conducting MXene nanosheets network with biological hydrogel polymer network for conformally stably attaching onto human skin for high-quality recording of various epidermal electrophysiological signals with high signal-to-noise ratios (SNR) and low interfacial impedance for intelligent medical diagnosis and smart human-machine interface. Moreover, a smart sign language gesture recognition platform based on collected electromyogram (EMG) signals is designed for hassle-free communication with hearing-impaired people with the help of advanced machine learning algorithms. Meanwhile, the bioadhesive MXene hydrogel possesses reliable antibacterial capability, excellent biocompatibility, and effective hemostasis properties for promising bacterial-infected wound bleeding.

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.

Characterizing collagen scaffold compliance with native myocardial strains using an ex-vivo cardiac model: The physio-mechanical influence of scaffold architecture and attachment method

Applied to the epicardium in-vivo, regenerative cardiac patches support the ventricular wall, reduce wall stresses, encourage ventricular wall thickening, and improve ventricular function. Scaffold engraftment, however, remains a challenge. After implantation, scaffolds are subject to the complex, time-varying, biomechanical environment of the myocardium. The mechanical capacity of engineered tissue to biomimetically deform and simultaneously support the damaged native tissue is crucial for its efficacy. To date, however, the biomechanical response of engineered tissue applied directly to live myocardium has not been characterized. In this paper, we utilize optical imaging of a Langendorff ex-vivo cardiac model to characterize the native deformation of the epicardium as well as that of attached engineered scaffolds. We utilize digital image correlation, linear strain, and 2D principal strain analysis to assess the mechanical compliance of acellular ice templated collagen scaffolds. Scaffolds had either aligned or isotropic porous architecture and were adhered directly to the live epicardial surface with either sutures or cyanoacrylate glue. We demonstrate that the biomechanical characteristics of native myocardial deformation on the epicardial surface can be reproduced by an ex-vivo cardiac model. Furthermore, we identified that scaffolds with unidirectionally aligned pores adhered with suture fixation most accurately recapitulated the deformation of the native epicardium. Our study contributes a translational characterization methodology to assess the physio-mechanical performance of engineered cardiac tissue and adds to the growing body of evidence showing that anisotropic scaffold architecture improves the functional biomimetic capacity of engineered cardiac tissue. STATEMENT OF SIGNIFICANCE: Engineered cardiac tissue offers potential for myocardial repair, but engraftment remains a challenge. In-vivo, engineered scaffolds are subject to complex biomechanical stresses and the mechanical capacity of scaffolds to biomimetically deform is critical. To date, the biomechanical response of engineered scaffolds applied to live myocardium has not been characterized. In this paper, we utilize optical imaging of an ex-vivo cardiac model to characterize the deformation of the native epicardium and scaffolds attached directly to the heart. Comparing scaffold architecture and fixation method, we demonstrate that sutured scaffolds with anisotropic pores aligned with the native alignment of the superficial myocardium best recapitulate native deformation. Our study contributes a physio-mechanical characterization methodology for cardiac tissue engineering scaffolds.

Reconstruction of zinc-metal battery solvation structures operating from -50 ~ +100 °C

Serious solvation effect of zinc ions has been considered as the cause of the severe side reactions (hydrogen evolution, passivation, dendrites, and etc.) of aqueous zinc metal batteries. Even though the regulation of cationic solvation structure has been widely studied, effects of the anionic solvation structures on the zinc metal were rarely examined. Herein, co-reconstruction of anionic and cationic solvation structures was realized through constructing a new multi-component electrolyte (Zn(BF4)2-glycerol-boric acid-chitosan-polyacrylamide, simplified as ZGBCP), which incorporates double crosslinking network via the esterification, protonation and polymerization reactions, thereby combining multiple advantages of 'liquid-like' high conductivity, 'gel-like' robust interface, and 'solid-like' high Zn2+ transfer number. Based on the ZGBCP electrolyte, the Zn anodes achieve record-low polarization and stable cycling. Furthermore, the ZGBCP electrolyte renders the AZMBs ultrawide working temperature (-50 °C ~ +100 °C) and ultralong cycle life (30000 cycles), which further validates the feasibility of the dual solvation structure strategy and provides a innovative perspective for the development of high-performance AZMBs.

Advanced Cardiac Patches for the Treatment of Myocardial Infarction

Myocardial infarction is a cardiovascular disease characterized by a high incidence rate and mortality. It leads to various cardiac pathophysiological changes, including ischemia/reperfusion injury, inflammation, fibrosis, and ventricular remodeling, which ultimately result in heart failure and pose a significant threat to global health. Although clinical reperfusion therapies and conventional pharmacological interventions improve emergency survival rates and short-term prognoses, they are still limited in providing long-lasting improvements in cardiac function or reversing pathological progression. Recently, cardiac patches have gained considerable attention as a promising therapy for myocardial infarction. These patches consist of scaffolds or loaded therapeutic agents that provide mechanical reinforcement, synchronous electrical conduction, and localized delivery within the infarct zone to promote cardiac restoration. This review elucidates the pathophysiological progression from myocardial infarction to heart failure, highlighting therapeutic targets and various cardiac patches. The review considers the primary scaffold materials, including synthetic, natural, and conductive materials, and the prevalent fabrication techniques and optimal properties of the patch, as well as advanced delivery strategies. Last, the current limitations and prospects of cardiac patch research are considered, with the goal of shedding light on innovative products poised for clinical application.

In Situ-Sprayed Bioinspired Adhesive Conductive Hydrogels for Cavernous Nerve Repair

Cavernous nerve injury (CNI), resulting in erectile dysfunction (ED), poses a significant threat to the quality of life for men. Strategies utilizing conductive hydrogels have demonstrated promising results for the treatment of peripheral nerves with a large diameter (>2 mm). However, integrating convenient minimally invasive operation, antiswelling and immunomodulatory conductive hydrogels for treating small-diameter injured cavernous nerves remains a great challenge. Here, a sprayable adhesive conductive hydrogel (GACM) composed of gelatin, adenine, carbon nanotubes, and mesaconate designed for cavernous nerve repair is developed. Multiple hydrogen bonds provide GACM with excellent adhesive and antiswelling properties, enabling it to establish a conformal electrical bridge with the damaged nerve and aiding in the regeneration process. Additionally, mesaconate-loaded GACM suppresses the release of inflammatory factors by macrophages and promotes the migration and proliferation of Schwann cells. In vivo tests demonstrate that the GACM hydrogel repairs the cavernous nerve and restores erectile function and fertility. Furthermore, the feasibility of sprayable GACM in minimally invasive robotic surgery in beagles is validated. Given the benefits of therapeutic effectiveness and clinical convenience, the research suggests a promising future for sprayable GACM materials as advanced solutions for minimally invasive nerve repair.

Chronological-Programmed Black Phosphorus Hydrogel for Responsive Modulation of the Pathological Microenvironment in Myocardial Infarction

Electroactive hydrogels have garnered extensive interest as a promising approach to myocardial tissue engineering. However, the challenges of spatiotemporal-specific modulation of individual pathological processes and achieving nontoxic bioresorption still remain. Herein, inspired by the entire postinfarct pathological processes, an injectable conductive bioresorbable black phosphorus nanosheets (BPNSs)-loaded hydrogel (BHGD) was developed via reactive oxide species (ROS)-sensitive disulfide-bridge and photomediated cross-linking reaction. Significantly, the chronologically programmed BHGD hydrogel can achieve graded modulation during the inflammatory, proliferative, and maturation phases of myocardial infarction (MI). More details, during early infarction, the BHGD hydrogel can effectively reduce ROS levels in the MI area, inhibit cellular oxidative stress damage, and promote macrophage M2 polarization, creating a favorable environment for damaged myocardium repair. Meanwhile, the ROS-responsive structure can protect BPNSs from degradation and maintain good conductivity under MI microenvironments. Therefore, the BHGD hydrogel possesses tissue-matched modulus and conductivity in the MI area, facilitating cardiomyocyte maturation and electrical signal exchange, compensating for impaired electrical signaling, and promoting vascularization in infarcted areas in the maturation phase. More importantly, all components of the hydrogel degrade into nontoxic substances without adverse effects on vital organs. Overall, the presented BPNS-loaded hydrogel offers an expandable and safe option for clinical treatment of MI.