Soft hydrogel semiconductors with augmented biointeractive functions.

Hydrogels, known for their mechanical and chemical similarity to biological tissues, are widely used in biotechnologies, whereas semiconductors provide advanced electronic and optoelectronic functionalities such as signal amplification, sensing, and photomodulation. Combining semiconducting properties with hydrogel designs can enhance biointeractive functions and intimacy at biointerfaces, but this is challenging owing to the low hydrophilicity of polymer semiconductors. We developed a solvent affinity-induced assembly method that incorporates water-insoluble polymer semiconductors into double-network hydrogels. These semiconductors exhibited tissue-level moduli as soft as 81 kilopascals, stretchability of 150% strain, and charge-carrier mobility up to 1.4 square centimeters per volt per second. When they are interfaced with biological tissues, their tissue-level modulus enables alleviated immune reactions. The hydrogel's high porosity enhances molecular interactions at semiconductor-biofluid interfaces, resulting in photomodulation with higher response and volumetric biosensing with higher sensitivity.

Beyond 25 years of biomedical innovation in nano-bioelectronics.

Nano-bioelectronics, which blend the precision of nanotechnology with the complexity of biological systems, are evolving with innovations such as silicon nanowires, carbon nanotubes, and graphene. These elements serve applications from biochemical sensing to brain-machine interfacing. This review examines nano-bioelectronics' role in advancing biomedical interventions and discusses their potential in environmental monitoring, agricultural productivity, energy efficiency, and creative fields. The field is transitioning from molecular to ecosystem-level applications, with research exploring complex cellular mechanisms and communication. This fosters understanding of biological interactions at various levels, such as suggesting transformative approaches for ecosystem management and food security. Future research is expected to focus on refining nano-bioelectronic devices for integration with biological systems and on scalable manufacturing to broaden their reach and functionality.

Active biointegrated living electronics for managing inflammation.

Seamless interfaces between electronic devices and biological tissues stand to revolutionize disease diagnosis and treatment. However, biological and biomechanical disparities between synthetic materials and living tissues present challenges at bioelectrical signal transduction interfaces. We introduce the active biointegrated living electronics (ABLE) platform, encompassing capabilities across the biogenic, biomechanical, and bioelectrical properties simultaneously. The living biointerface, comprising a bioelectronics layout and a Staphylococcus epidermidis-laden hydrogel composite, enables multimodal signal transduction at the microbial-mammalian nexus. The extracellular components of the living hydrogels, prepared through thermal release of naturally occurring amylose polymer chains, are viscoelastic, capable of sustaining the bacteria with high viability. Through electrophysiological recordings and wireless probing of skin electrical impedance, body temperature, and humidity, ABLE monitors microbial-driven intervention in psoriasis.

Exploring Present and Future Directions in Nano-Enhanced Optoelectronic Neuromodulation.

Electrical neuromodulation has achieved significant translational advancements, including the development of deep brain stimulators for managing neural disorders and vagus nerve stimulators for seizure treatment. Optoelectronics, in contrast to wired electrical systems, offers the leadless feature that guides multisite and high spatiotemporal neural system targeting, ensuring high specificity and precision in translational therapies known as "photoelectroceuticals". This Account provides a concise overview of developments in novel optoelectronic nanomaterials that are engineered through innovative molecular, chemical, and nanostructure designs to facilitate neural interfacing with high efficiency and minimally invasive implantation.This Account outlines the progress made both within our laboratory and across the broader scientific community, with particular attention to implications in materials innovation strategies, studying bioelectrical activation with spatiotemporal methods, and applications in regenerative medicine. In materials innovation, we highlight a nongenetic, biocompatible, and minimally invasive approach for neuromodulation that spans various length scales, from single neurons to nerve tissues using nanosized particles and monolithic membranes. Furthermore, our discussion exposes the critical unresolved questions in the field, including mechanisms of interaction at the nanobio interface, the precision of cellular or tissue targeting, and integration into existing neural networks with high spatiotemporal modulation. In addition, we present the challenges and pressing needs for long-term stability and biocompatibility, scalability for clinical applications, and the development of noninvasive monitoring and control systems.In addressing the existing challenges in the field of nanobio interfaces, particularly for neural applications, we envisage promising strategic directions that could significantly advance this burgeoning domain. This involves a deeper theoretical understanding of nanobiointerfaces, where simulations and experimental validations on how nanomaterials interact spatiotemporally with biological systems are crucial. The development of more durable materials is vital for prolonged applications in dynamic neural interfaces, and the ability to manipulate neural activity with high specificity and spatial resolution, paves the way for targeting individual neurons or specific neural circuits. Additionally, integrating these interfaces with advanced control systems, possibly leveraging artificial intelligence and machine learning algorithms and programming dynamically responsive materials designs, could significantly ease the implementation of stimulation and recording. These innovations hold the potential to introduce novel treatment modalities for a wide range of neurological and systemic disorders.

Multimodal probing of T-cell recognition with hexapod heterostructures.

Studies using antigen-presenting systems at the single-cell and ensemble levels can provide complementary insights into T-cell signaling and activation. Although crucial for advancing basic immunology and immunotherapy, there is a notable absence of synthetic material toolkits that examine T cells at both levels, and especially those capable of single-molecule-level manipulation. Here we devise a biomimetic antigen-presenting system (bAPS) for single-cell stimulation and ensemble modulation of T-cell recognition. Our bAPS uses hexapod heterostructures composed of a submicrometer cubic hematite core (α-Fe2O3) and nanostructured silica branches with diverse surface modifications. At single-molecule resolution, we show T-cell activation by a single agonist peptide-loaded major histocompatibility complex; distinct T-cell receptor (TCR) responses to structurally similar peptides that differ by only one amino acid; and the superior antigen recognition sensitivity of TCRs compared with that of chimeric antigen receptors (CARs). We also demonstrate how the magnetic field-induced rotation of hexapods amplifies the immune responses in suspended T and CAR-T cells. In addition, we establish our bAPS as a precise and scalable method for identifying stimulatory antigen-specific TCRs at the single-cell level. Thus, our multimodal bAPS represents a unique biointerface tool for investigating T-cell recognition, signaling and function.

Monolithic silicon for high spatiotemporal translational photostimulation.

Electrode-based electrical stimulation underpins several clinical bioelectronic devices, including deep-brain stimulators1,2 and cardiac pacemakers3. However, leadless multisite stimulation is constrained by the technical difficulties and spatial-access limitations of electrode arrays. Optogenetics offers optically controlled random access with high spatiotemporal capabilities, but clinical translation poses challenges4-6. Here we show tunable spatiotemporal photostimulation of cardiac systems using a non-genetic platform based on semiconductor-enabled biomodulation interfaces. Through spatiotemporal profiling of photoelectrochemical currents, we assess the magnitude, precision, accuracy and resolution of photostimulation in four leadless silicon-based monolithic photoelectrochemical devices. We demonstrate the optoelectronic capabilities of the devices through optical overdrive pacing of cultured cardiomyocytes (CMs) targeting several regions and spatial extents, isolated rat hearts in a Langendorff apparatus, in vivo rat hearts in an ischaemia model and an in vivo mouse heart model with transthoracic optical pacing. We also perform the first, to our knowledge, optical override pacing and multisite pacing of a pig heart in vivo. Our systems are readily adaptable for minimally invasive clinical procedures using our custom endoscopic delivery device, with which we demonstrate closed-thoracic operations and endoscopic optical stimulation. Our results indicate the clinical potential of the leadless, lightweight and multisite photostimulation platform as a pacemaker in cardiac resynchronization therapy (CRT), in which lead-placement complications are common.

Bridging the Gap-Thermofluidic Designs for Precision Bioelectronics.

Bioelectronics, the merging of biology and electronics, can monitor and modulate biological behaviors across length and time scales with unprecedented capability. Current bioelectronics research largely focuses on devices' mechanical properties and electronic designs. However, the thermofluidic control is often overlooked, which is noteworthy given the discipline's importance in almost all bioelectronics processes. It is believed that integrating thermofluidic designs into bioelectronics is essential to align device precision with the complexity of biofluids and biological structures. This perspective serves as a mini roadmap for researchers in both fields to introduce key principles, applications, and challenges in both bioelectronics and thermofluids domains. Important interdisciplinary opportunities for the development of future healthcare devices and precise bioelectronics will also be discussed.

Perspectives on Multiscale Colloid-Based Materials for Biomedical Applications.

Colloid-based materials with tunable biophysical and chemical properties have demonstrated significant potential in a wide range of biomedical applications. The ability to manipulate these properties across various size scales, encompassing nano-, micro-, and macrodomains, is essential to enhancing current biomedical technologies and facilitating the development of novel applications. Focusing on material design, we explore various synthetic colloid-based materials at the nano- and microscales and investigate their correlation with biological systems. Furthermore, we examine the utilization of the self-assembly of colloids to construct monolithic and macroscopic materials suitable for biointerfaces. By probing the potential of spatial imaging and localized drug delivery, enhanced functionality, and colloidal manipulation, we highlight emerging opportunities that could significantly advance the field of colloid-based materials in biomedical applications.

Nanowired human cardiac organoid transplantation enables highly efficient and effective recovery of infarcted hearts.

Human cardiac organoids hold remarkable potential for cardiovascular disease modeling and human pluripotent stem cell-derived cardiomyocyte (hPSC-CM) transplantation. Here, we show cardiac organoids engineered with electrically conductive silicon nanowires (e-SiNWs) significantly enhance the therapeutic efficacy of hPSC-CMs to treat infarcted hearts. We first demonstrated the biocompatibility of e-SiNWs and their capacity to improve cardiac microtissue engraftment in healthy rat myocardium. Nanowired human cardiac organoids were then engineered with hPSC-CMs, nonmyocyte supporting cells, and e-SiNWs. Nonmyocyte supporting cells promoted greater ischemia tolerance of cardiac organoids, and e-SiNWs significantly improved electrical pacing capacity. After transplantation into ischemia/reperfusion-injured rat hearts, nanowired cardiac organoids significantly improved contractile development of engrafted hPSC-CMs, induced potent cardiac functional recovery, and reduced maladaptive left ventricular remodeling. Compared to contemporary studies with an identical injury model, greater functional recovery was achieved with a 20-fold lower dose of hPSC-CMs, revealing therapeutic synergy between conductive nanomaterials and human cardiac organoids for efficient heart repair.

Bioadhesive polymer semiconductors and transistors for intimate biointerfaces.

The use of bioelectronic devices relies on direct contact with soft biotissues. For transistor-type bioelectronic devices, the semiconductors that need to have direct interfacing with biotissues for effective signal transduction do not adhere well with wet tissues, thereby limiting the stability and conformability at the interface. We report a bioadhesive polymer semiconductor through a double-network structure formed by a bioadhesive brush polymer and a redox-active semiconducting polymer. The resulting semiconducting film can form rapid and strong adhesion with wet tissue surfaces together with high charge-carrier mobility of ~1 square centimeter per volt per second, high stretchability, and good biocompatibility. Further fabrication of a fully bioadhesive transistor sensor enabled us to produce high-quality and stable electrophysiological recordings on an isolated rat heart and in vivo rat muscles.

Achieving tissue-level softness on stretchable electronics through a generalizable soft interlayer design.

Soft and stretchable electronics have emerged as highly promising tools for biomedical diagnosis and biological studies, as they interface intimately with the human body and other biological systems. Most stretchable electronic materials and devices, however, still have Young's moduli orders of magnitude higher than soft bio-tissues, which limit their conformability and long-term biocompatibility. Here, we present a design strategy of soft interlayer for allowing the use of existing stretchable materials of relatively high moduli to versatilely realize stretchable devices with ultralow tissue-level moduli. We have demonstrated stretchable transistor arrays and active-matrix circuits with moduli below 10 kPa-over two orders of magnitude lower than the current state of the art. Benefiting from the increased conformability to irregular and dynamic surfaces, the ultrasoft device created with the soft interlayer design realizes electrophysiological recording on an isolated heart with high adaptability, spatial stability, and minimal influence on ventricle pressure. In vivo biocompatibility tests also demonstrate the benefit of suppressing foreign-body responses for long-term implantation. With its general applicability to diverse materials and devices, this soft-interlayer design overcomes the material-level limitation for imparting tissue-level softness to a variety of bioelectronic devices.

Periplasmic biomineralization for semi-artificial photosynthesis.

Semiconductor-based biointerfaces are typically established either on the surface of the plasma membrane or within the cytoplasm. In Gram-negative bacteria, the periplasmic space, characterized by its confinement and the presence of numerous enzymes and peptidoglycans, offers additional opportunities for biomineralization, allowing for nongenetic modulation interfaces. We demonstrate semiconductor nanocluster precipitation containing single- and multiple-metal elements within the periplasm, as observed through various electron- and x-ray-based imaging techniques. The periplasmic semiconductors are metastable and display defect-dominant fluorescent properties. Unexpectedly, the defect-rich (i.e., the low-grade) semiconductor nanoclusters produced in situ can still increase adenosine triphosphate levels and malate production when coupled with photosensitization. We expand the sustainability levels of the biohybrid system to include reducing heavy metals at the primary level, building living bioreactors at the secondary level, and creating semi-artificial photosynthesis at the tertiary level. The biomineralization-enabled periplasmic biohybrids have the potential to serve as defect-tolerant platforms for diverse sustainable applications.

Perspectives on tissue-like bioelectronics for neural modulation.

Advances in bioelectronic implants have been offering valuable chances to interface and modulate neural systems. Potential mismatches between bioelectronics and targeted neural tissues require devices to exhibit "tissue-like" properties for better implant-bio integration. In particular, mechanical mismatches pose a significant challenge. In the past years, efforts were made in both materials synthesis and device design to achieve bioelectronics mechanically and biochemically mimicking biological tissues. In this perspective, we mainly summarized recent progress of developing "tissue-like" bioelectronics and categorized them into different strategies. We also discussed how these "tissue-like" bioelectronics were utilized for modulating in vivo nervous systems and neural organoids. We concluded the perspective by proposing further directions including personalized bioelectronics, novel materials design and the involvement of artificial intelligence and robotic techniques.

A soil-inspired dynamically responsive chemical system for microbial modulation.

Interactions between the microbiota and their colonized environments mediate critical pathways from biogeochemical cycles to homeostasis in human health. Here we report a soil-inspired chemical system that consists of nanostructured minerals, starch granules and liquid metals. Fabricated via a bottom-up synthesis, the soil-inspired chemical system can enable chemical redistribution and modulation of microbial communities. We characterize the composite, confirming its structural similarity to the soil, with three-dimensional X-ray fluorescence and ptychographic tomography and electron microscopy imaging. We also demonstrate that post-synthetic modifications formed by laser irradiation led to chemical heterogeneities from the atomic to the macroscopic level. The soil-inspired material possesses chemical, optical and mechanical responsiveness to yield write-erase functions in electrical performance. The composite can also enhance microbial culture/biofilm growth and biofuel production in vitro. Finally, we show that the soil-inspired system enriches gut bacteria diversity, rectifies tetracycline-induced gut microbiome dysbiosis and ameliorates dextran sulfate sodium-induced rodent colitis symptoms within in vivo rodent models.

Nanoenabled Trainable Systems: From Biointerfaces to Biomimetics.

In the dynamic biological system, cells and tissues adapt to diverse environmental conditions and form memories, an essential aspect of training for survival and evolution. An understanding of the biological training principles will inform the design of biomimetic materials whose properties evolve with the environment and offer routes to programmable soft materials, neuromorphic computing, living materials, and biohybrid robotics. In this perspective, we examine the mechanisms by which cells are trained by environmental cues. We outline the artificial platforms that enable biological training and examine the relationship between biological training and biomimetic materials design. We place emphasis on nanoscale material platforms which, given their applicability to chemical, mechanical and electrical stimulation, are critical to bridging natural and synthetic systems.

Distributed interfacing by nanoscale photodiodes enables single-neuron light activation and sensory enhancement in 3D spinal explants.

Among emerging technologies developed to interface neuronal signaling, engineering electrodes at the nanoscale would yield more precise biodevices opening to progress in neural circuit investigations and to new therapeutic potential. Despite remarkable progress in miniature electronics for less invasive neurostimulation, most nano-enabled, optically triggered interfaces are demonstrated in cultured cells, which precludes the studies of natural neural circuits. We exploit here free-standing silicon-based nanoscale photodiodes to optically modulate single, identified neurons in mammalian spinal cord explants. With near-infrared light stimulation, we show that activating single excitatory or inhibitory neurons differently affects sensory circuits processing in the dorsal horn. We successfully functionalize nano-photodiodes to target single molecules, such as glutamate AMPA receptor subunits, thus enabling light activation of specific synaptic pathways. We conclude that nano-enabled neural interfaces can modulate selected sensory networks with low invasiveness. The use of nanoscale photodiodes can thus provide original perspective in linking neural activity to specific behavioral outcome.

Porosity-based heterojunctions enable leadless optoelectronic modulation of tissues.

Homo- and heterojunctions play essential roles in semiconductor-based devices such as field-effect transistors, solar cells, photodetectors and light-emitting diodes. Semiconductor junctions have been recently used to optically trigger biological modulation via photovoltaic or photoelectrochemical mechanisms. The creation of heterojunctions typically involves materials with different doping or composition, which leads to high cost, complex fabrications and potential side effects at biointerfaces. Here we show that a porosity-based heterojunction, a largely overlooked system in materials science, can yield an efficient photoelectrochemical response from the semiconductor surface. Using self-limiting stain etching, we create a nanoporous/non-porous, soft-hard heterojunction in p-type silicon within seconds under ambient conditions. Upon surface oxidation, the heterojunction yields a strong photoelectrochemical response in saline. Without any interconnects or metal modifications, the heterojunction enables efficient non-genetic optoelectronic stimulation of isolated rat hearts ex vivo and sciatic nerves in vivo with optical power comparable to optogenetics, and with near-infrared capabilities.

Stretchable Redox-Active Semiconducting Polymers for High-Performance Organic Electrochemical Transistors.

Organic electrochemical transistors (OECTs) represent an emerging device platform for next-generation bioelectronics owing to the uniquely high amplification and sensitivity to biological signals. For achieving seamless tissue-electronics interfaces for accurate signal acquisition, skin-like softness and stretchability are essential requirements, but they have not yet been imparted onto high-performance OECTs, largely due to the lack of stretchable redox-active semiconducting polymers. Here, a stretchable semiconductor is reported for OECT devices, namely poly(2-(3,3'-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-[2,2'-bithiophen]-5)yl thiophene) (p(g2T-T)), which gives exceptional stretchability over 200% strain and 5000 repeated stretching cycles, together with OECT performance on par with the state-of-the-art. Validated by systematic characterizations and comparisons of different polymers, the key design features of this polymer that enable the combination of high stretchability and high OECT performance are a nonlinear backbone architecture, a moderate side-chain density, and a sufficiently high molecular weight. Using this highly stretchable polymer semiconductor, an intrinsically stretchable OECT is fabricated with high normalized transconductance (≈223 S cm-1 ) and biaxial stretchability up to 100% strain. Furthermore, on-skin electrocardiogram (ECG) recording is demonstrated, which combines built-in amplification and unprecedented skin conformability.

Freestanding nanomaterials for subcellular neuronal interfaces.

Current technological advances in neural probing and modulation have enabled an extraordinary glimpse into the intricacies of the nervous system. Particularly, nanomaterials are proving to be an incredibly versatile platform for neurological applications owing to their biocompatibility, tunability, highly specific targeting and sensing, and long-term chemical stability. Among the most desirable nanomaterials for neuroengineering, freestanding nanomaterials are minimally invasive and remotely controlled. This review outlines the most recent developments of freestanding nanomaterials that operate on the neuronal interface. First, the different nanomaterials and their mechanisms for modulating neurons are explored to provide a basis for how freestanding nanomaterials operate. Then, the three main applications of subcellular neuronal engineering-modulating neuronal behavior, exploring fundamental neuronal mechanism, and recording neuronal signal-are highlighted with specific examples of current advancements. Finally, we conclude with our perspective on future nanomaterial designs and applications.