Nano-Bioelectronics

Hydrogel facilitated bioelectronic integration

The recent advances in bio-integratable electronics are creating new opportunities for investigating and directing biologically significant processes, yet their performance to date is still limited by the inherent physiochemical and signaling mismatches at the heterogeneous interfaces. Hydrogels represent a unique category of materials to bridge the gap between biological and electronic systems because of their structural/functional similarity to biological tissues and design versatility to accommodate cross-system communication. In this review, we discuss the latest progress in the engineering of hydrogel interfaces for bioelectronics development that promotes (1) structural compatibility, where the mechanical and chemical properties of hydrogels can be modulated to achieve coherent, chronically stable biotic-abiotic junctions; and (2) interfacial signal transduction, where the charge and mass transport within the hydrogel mediators can be rationally programmed to condition/amplify the bioderived signals and enhance the electrical/electrochemical coupling. We will further discuss the application of functional hydrogels in complex physiological environments for bioelectronic integration across different scales/biological levels. These ongoing research efforts have the potential to blur the distinction between living systems and artificial electronics, and ultimately decode and regulate biological functioning for both fundamental inquiries and biomedical applications.

Amino-acid interactions with the Au(111) surface: adsorption, band alignment, and interfacial electronic coupling

The charge transport properties of biological molecules like peptides and proteins are intensively studied for the great flexibility, redox-state variability, long-range efficiency, and biocompatibility of potential bioelectronic applications. Yet, the electronic interactions of biomolecules with solid metal surfaces, determining the conductivities of the biomolecular junctions, are hard to predict and usually unavailable. Here, we present accurate adsorption structures and energies, electronic band alignment, and interfacial electronic coupling data for all 20 natural amino acids computed using the DFT+Σ scheme based on the vdW-DF and OT-RSH functionals. For comparison, data obtained using the popular PBE functional are provided as well. Tryptophan, compared to other amino acids, is shown to be distinctly exceptional in terms of the electronic properties related to charge transport. Its high adsorption energy, frontier-orbital levels aligned relatively close to the Fermi energy of gold and strong interfacial electronic coupling make it an ideal candidate for facilitating charge transfer on such heterogeneous interfaces. Although the amino acids in peptides and proteins are affected by the structural interactions hindering their contact with the surface, knowledge of the single-molecule surface interactions is necessary for a detailed understanding of such structural effects and tuning of potential applications.

Symbiotic assembly of peptide nano-mosaics at solid interfaces

The spontaneous co-organization of distinct biomolecules at interfaces enables many of Nature's hierarchical organizations involving both hard and soft materials. Engineering efforts to mimic such hybrid complexes rely on our ability to rationally structure biomolecules at inorganic interfaces. Control over the nanoscale structure of patterned biomolecules remains challenging due to difficulties in controlling the multifarious interactions involved. This work discusses binary peptide assembly as a means to fabricate biomolecular nano-mosaics at graphite surfaces with predictable structures. Distinct peptide-substrate interactions lead to divergent crystallographic growth directions, molecular scale immiscibility, and a symbiotic assembly phenomenon. We present a symbiotic assembly model that accurately predicts the binary assembly structure relying solely on the constituent peptide nucleation kinetics and molar fractions. The ability to tune such biomolecular nano-mosaic structures facilitates the bottom up fabrication of high-density, multifunctional interfaces for nanotechnology.

A digital nervous system aiming toward personalized IoT healthcare

Body area networks (BANs), cloud computing, and machine learning are platforms that can potentially enable advanced healthcare outside the hospital. By applying distributed sensors and drug delivery devices on/in our body and connecting to such communication and decision-making technology, a system for remote diagnostics and therapy is achieved with additional autoregulation capabilities. Challenges with such autarchic on-body healthcare schemes relate to integrity and safety, and interfacing and transduction of electronic signals into biochemical signals, and vice versa. Here, we report a BAN, comprising flexible on-body organic bioelectronic sensors and actuators utilizing two parallel pathways for communication and decision-making. Data, recorded from strain sensors detecting body motion, are both securely transferred to the cloud for machine learning and improved decision-making, and sent through the body using a secure body-coupled communication protocol to auto-actuate delivery of neurotransmitters, all within seconds. We conclude that both highly stable and accurate sensing-from multiple sensors-are needed to enable robust decision making and limit the frequency of retraining. The holistic platform resembles the self-regulatory properties of the nervous system, i.e., the ability to sense, communicate, decide, and react accordingly, thus operating as a digital nervous system.

Integrated contact lens sensor system based on multifunctional ultrathin MoS2 transistors

Smart contact lenses attract extensive interests due to their capability of directly monitoring physiological and ambient information. However, previous demonstrations usually lacked efficient sensor modalities, facile fabrication process, mechanical stability, or biocompatibility. Here, we demonstrate a flexible approach for fabrication of multifunctional smart contact lenses with an ultrathin MoS₂ transistors-based serpentine mesh sensor system. The integrated sensor systems contain a photodetector for receiving optical information, a glucose sensor for monitoring glucose level directly from tear fluid, and a temperature sensor for diagnosing potential corneal disease. Unlike traditional sensors and circuit chips sandwiched in the lens substrate, this serpentine mesh sensor system can be directly mounted onto the lenses and maintain direct contact with tears, delivering high detection sensitivity, while being mechanically robust and not interfering with either blinking or vision. Furthermore, the in vitro cytotoxicity tests reveal good biocompatibility, thus holding promise as next-generation soft electronics for healthcare and medical applications.

Graphene for Biosensing Applications in Point-of-Care Testing

Graphene and graphene-related materials (GRMs) exhibit a unique combination of electronic, optical, and electrochemical properties, which make them ideally suitable for ultrasensitive and selective point-of-care testing (POCT) devices. POCT device-based applications in diagnostics require test results to be readily accessible anywhere to produce results within a short analysis timeframe. This review article provides a summary of methods and latest developments in the field of graphene and GRM-based biosensing in POCT and an overview of the main applications of the latter in nucleic acids and enzymatic biosensing, cell detection, and immunosensing. For each application, we discuss scientific and technological advances along with the remaining challenges, outlining future directions for widespread use of this technology in biomedical applications.

Toward nanobioelectronic medicine: Unlocking new applications using nanotechnology

Bioelectronic medicine aims to interface electronic technology with biological components and design more effective therapeutic and diagnostic tools. Advances in nanotechnology have moved the field forward improving the seamless interaction between biological and electronic components. In the lab many of these nanobioelectronic devices have the potential to improve current treatment approaches, including those for cancer, cardiovascular disorders, and disease underpinned by malfunctions in neuronal electrical communication. While promising, many of these devices and technologies require further development before they can be successfully applied in a clinical setting. Here, we highlight recent work which is close to achieving this goal, including discussion of nanoparticles, carbon nanotubes, and nanowires for medical applications. We also look forward toward the next decade to determine how current developments in nanotechnology could shape the growing field of bioelectronic medicine. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Biosensing.

Intrinsically Conductive Microbial Nanowires for 'Green' Electronics with Novel Functions

Intrinsically conductive protein nanowires, microbially produced from inexpensive, renewable feedstocks, are a sustainable alternative to traditional nanowire electronic materials, which require high energy inputs and hazardous conditions/chemicals for fabrication and can be highly toxic. Pilin-based nanowires can be tailored for specific functions via the design of synthetic pilin genes to tune wire conductivity or introduce novel functionalities. Other microbially produced nanowire options for electronics may include cytochrome wires, curli fibers, and the conductive fibers of cable bacteria. Proof-of-concept protein nanowire electronics that have been successfully demonstrated include biomedical sensors, neuromorphic devices, and a device that generates electricity from ambient humidity. Further development of applications will require interdisciplinary teams of engineers, biophysicists, and synthetic biologists.

Novel Nanofluidic Cells Based on Nanowires and Nanotubes for Advanced Chemical and Bio-Sensing Applications

Since the first introduction of one-dimensional nanochannels for single-molecule detection, there has been increasing interest in modern nanofluidic systems, such as chemical and biological sensing applications. Recently developed nanowires (NWs) and nanotubes (NTs) have received tremendous attention due to their unique geometrical, physical and chemical properties, which are very attractive in this field. Here, we review the recent research activities in the field of novel nanofluidic cells based on NWs and NTs. First, we give a brief introduction of this field. Then the common synthesis methods of NWs and NTs are summarized. After that, we discuss the working principle and sensing mechanism of nanofluidic devices, which is fundamental to the interaction between these nanostructures and small molecules. Finally, we present the NW- and NT-based devices for chemical and bio-sensing applications, such as gas sensing, pathogen detection, DNA sequencing, and so forth.

Two-Dimensional Material-Based Biosensors for Virus Detection

Viral infections are one of the major causes of mortality and economic losses worldwide. Consequently, efficient virus detection methods are crucial to determine the infection prevalence. However, most detection methods face challenges related to false-negative or false-positive results, long response times, high costs, and/or the need for specialized equipment and staff. Such issues can be overcome by access to low-cost and fast response point-of-care detection systems, and two-dimensional materials (2DMs) can play a critical role in this regard. Indeed, the unique and tunable physicochemical properties of 2DMs provide many advantages for developing biosensors for viral infections with high sensitivity and selectivity. Fast, accurate, and reliable detection, even at early infection stages by the virus, can be potentially enabled by highly accessible surface interactions between the 2DMs and the analytes. High selectivity can be obtained by functionalization of the 2DMs with antibodies, nucleic acids, proteins, peptides, or aptamers, allowing for specific binding to a particular virus, viral fingerprints, or proteins released by the host organism. Multiplexed detection and discrimination between different virus strains are also feasible. In this Review, we present a comprehensive overview of the major advances of 2DM-based biosensors for the detection of viruses. We describe the main factors governing the efficient interactions between viruses and 2DMs, making them ideal candidates for the detection of viral infections. We also critically detail their advantages and drawbacks, providing insights for the development of future biosensors for virus detection. Lastly, we provide suggestions to stimulate research in the fast expanding field of 2DMs that could help in designing advanced systems for preventing virus-related pandemics.

Environmentally Benign, Intrinsically Coordinated, Lithium-Based Solid Electrolyte with a Modified Purine as Supporting Ligand

Bioinspired materials have become increasingly competitive for electronic applications in recent years owing to the environment-friendly alternatives they offer. The notion of biocompatible solid organic electrolytes addresses the issues concerning potential leakage of corrosive liquids, volatility and flammability of electrolyte solvents. This study presents a new intrinsically coordinated Li^I adenine complex that exhibits electrical conductivity as a solid electrolyte capable of self-sustained supply of Li^I ions. It exhibits conductivity through moisture-assisted Li^I ion motion up to 373 K, and possibly by an ion-hopping mechanism beyond 373 K. This purine-derived solid electrolyte shows enhanced conductivity and transference number demonstrating the potential of purine-based ligands and their coordination complexes in interesting materials applications.

On the intersection of molecular bioelectronics and biosensors: 20 Years of C3B

Formed in 2000 at Virginia Commonwealth University, the Center for Bioelectronics, Biosensors and Biochips (C3B®) has subsequently been located at Clemson University and at Texas A&M University. Established as an industry-university collaborative center of excellence, the C3B has contributed new knowledge and technology in the areas of i) molecular bioelectronics, ii) responsive polymers, iii) multiplexed biosensor systems, and iv) bioelectronic biosensors. Noteworthy contributions in these areas include i) being the first to report direct electron transfer of oxidoreductase enzymes enabled by single walled carbon nanotubes and colloidal clays, ii) the molecular level integration of inherently conductive polymers with bioactive hydrogels using bi-functional monomers such as poly(pyrrole-co-3-pyrrolylbutyrate-conj-aminoethylmethacrylate) [PyBA-conj-AEMA] and 3-(1-ethyl methacryloylate)aniline to yield hetero-ladder electroconductive hydrogels, iii) the development of a multi-analyte physiological status monitoring biochip, and iv) the development of a bioanalytical Wien-bridge oscillator for the fused measurement to lactate and glucose. The present review takes a critical look of these contributions over the past 20 years and offers some perspective on the future of bioelectronics-based biosensors and systems. Particular attention is given to multiplexed biosensor systems and data fusion for rapid decision making.

Advances in Multidimensional Cardiac Biosensing Technologies: From Electrophysiology to Mechanical Motion and Contractile Force

Cardiovascular disease is currently a leading killer to human, while drug-induced cardiotoxicity remains the main cause of the withdrawal and attrition of drugs. Taking clinical correlation and throughput into account, cardiomyocyte is perfect as in vitro cardiac model for heart disease modeling, drug discovery, and cardiotoxicity assessment by accurately measuring the physiological multiparameters of cardiomyocytes. Remarkably, cardiomyocytes present both electrophysiological and biomechanical characteristics due to the unique excitation-contraction coupling, which plays a significant role in studying the cardiomyocytes. This review mainly focuses on the recent advances of biosensing technologies for the 2D and 3D cardiac models with three special properties: electrophysiology, mechanical motion, and contractile force. These high-performance multidimensional cardiac models are popular and effective to rebuild and mimic the heart in vitro. To help understand the high-quality and accurate physiologies, related detection techniques are highly demanded, from microtechnology to nanotechnology, from extracellular to intracellular recording, from multiple cells to single cell, and from planar to 3D models. Furthermore, the characteristics, advantages, limitations, and applications of these cardiac biosensing technologies, as well as the future development prospects should contribute to the systematization and expansion of knowledge.

Recent advances in bioelectronics chemistry

Research in bioelectronics is highly interdisciplinary, with many new developments being based on techniques from across the physical and life sciences. Advances in our understanding of the fundamental chemistry underlying the materials used in bioelectronic applications have been a crucial component of many recent discoveries. In this review, we highlight ways in which a chemistry-oriented perspective may facilitate novel and deep insights into both the fundamental scientific understanding and the design of materials, which can in turn tune the functionality and biocompatibility of bioelectronic devices. We provide an in-depth examination of several developments in the field, organized by the chemical properties of the materials. We conclude by surveying how some of the latest major topics of chemical research may be further integrated with bioelectronics.

Recent advances in bioelectronics chemistry

Research in bioelectronics is highly interdisciplinary, with many new developments being based on techniques from across the physical and life sciences. Advances in our understanding of the fundamental chemistry underlying the materials used in bioelectronic applications have been a crucial component of many recent discoveries. In this review, we highlight ways in which a chemistry-oriented perspective may facilitate novel and deep insights into both the fundamental scientific understanding and the design of materials, which can in turn tune the functionality and biocompatibility of bioelectronic devices. We provide an in-depth examination of several developments in the field, organized by the chemical properties of the materials. We conclude by surveying how some of the latest major topics of chemical research may be further integrated with bioelectronics.

Two-dimensional materials in biomedical, biosensing and sensing applications

Two-dimensional (2D) materials are at the forefront of materials research. Here we overview their applications beyond graphene, such as transition metal dichalcogenides, monoelemental Xenes (including phosphorene and bismuthene), carbon nitrides, boron nitrides along with transition metal carbides and nitrides (MXenes). We discuss their usage in various biomedical and environmental monitoring applications, from biosensors to therapeutic treatment agents, their toxicity and their utility in chemical sensing. We highlight how a specific chemical, physical and optical property of 2D materials can influence the performance of bio/sensing, improve drug delivery and photo/thermal therapy as well as affect their toxicity. Such properties are determined by crystal phases electrical conductivity, degree of exfoliation, surface functionalization, strong photoluminescence, strong optical absorption in the near-infrared range and high photothermal conversion efficiency. This review conveys the great future of all the families of 2D materials, especially with the expanding 2D materials' landscape as new materials emerge such as germanene and silicene.

100th Anniversary of Macromolecular Science Viewpoint: Soft Materials for Microbial Bioelectronics

Bioelectronics brings together the fields of biology and microelectronics to create multifunctional devices with the potential to address longstanding technological challenges and change our way of life. Microbial electrochemical devices are a growing subset of bioelectronic devices that incorporate naturally occurring or synthetically engineered microbes into electronic devices and have broad applications including energy harvesting, chemical production, water remediation, and environmental and health monitoring. The goal of this Viewpoint is to highlight recent advances and ongoing challenges in the rapidly developing field of microbial bioelectronic devices, with an emphasis on materials challenges. We provide an overview of microbial bioelectronic devices, discuss the biotic-abiotic interface in these devices, and then present recent advances and ongoing challenges in materials related to electron transfer across the abiotic-biotic interface, microbial adhesion, redox signaling, electronic amplification, and device miniaturization. We conclude with a summary and perspective of the field of microbial bioelectronics.

Bioinspired Materials for In Vivo Bioelectronic Neural Interfaces

The success of in vivo neural interfaces relies on their long-term stability and large scale in interrogating and manipulating neural activity after implantation. Conventional neural probes, owing to their limited spatiotemporal resolution and scale, face challenges for studying the massive, interconnected neural network in its native state. In this review, we argue that taking inspiration from biology will unlock the next generation of in vivo bioelectronic neural interfaces. Reducing the feature sizes of bioelectronic neural interfaces to mimic those of neurons enables high spatial resolution and multiplexity. Additionally, chronic stability at the device-tissue interface is realized by matching the mechanical properties of bioelectronic neural interfaces to those of the endogenous tissue. Further, modeling the design of neural interfaces after the endogenous topology of the neural circuitry enables new insights into the connectivity and dynamics of the brain. Lastly, functionalization of neural probe surfaces with coatings inspired by biology leads to enhanced tissue acceptance over extended timescales. Bioinspired neural interfaces will facilitate future developments in neuroscience studies and neurological treatments by leveraging bidirectional information transfer and integrating neuromorphic computing elements.

Engineering control circuits for molecular robots using synthetic biology

The integration of molecular robots and synthetic biology allows for the creation of sophisticated behaviors at the molecular level. Similar to the synergy between bioelectronics and soft robotics, synthetic biology provides control circuitry for molecular robots. By encoding perception-action modules within synthetic circuits, molecular machines can advance beyond repeating tasks to the incorporation of complex behaviors. In particular, cell-free synthetic biology provides biomolecular circuitry independent of living cells. This research update reviews the current progress in using synthetic biology as perception-action control modules in robots from molecular robots to macroscale robots. Additionally, it highlights recent developments in molecular robotics and cell-free synthetic biology and suggests their combined use as a necessity for future molecular robot development.

Interfacial Electrofabrication of Freestanding Biopolymer Membranes with Distal Electrodes

Using electrical signals to guide materials' deposition has a long-standing history in metal coating, microchip fabrication, and the integration of organics with devices. In electrodeposition, however, the conductive materials can be deposited only onto the electrode surfaces. Here, an innovative process is presented to electrofabricate freestanding biopolymer membranes at the interface of electrolytes without any supporting electrodes at the fabrication site. Chitosan, a derivative from the naturally abundant biopolymer chitin, has been broadly explored in electrodeposition for integrating biological entities onto microfabricated devices. It is widely believed that the pH gradients generated at the cathode deprotonate the positively charged chitosan chains into a film on the cathode surface. The interfacial electrofabrication with pH indicators, however, demonstrated that the membrane growth was driven by the instantaneous flow of hydroxyl ions from the ambient alginate solution, rather than the slow propagation of pH gradients from the cathode surface. This interfacial electrofabrication produces freestanding membrane structures and can be expanded to other materials, which presents a new direction in using electrical signals for manufacturing.

Nanocytometer for smart analysis of peripheral blood and acute myeloid leukemia: a pilot study

We realize an ultracompact nanocytometer for real-time impedimetric detection and classification of subpopulations of living cells. Nanoscopic nanowires in a microfluidic channel act as nanocapacitors and measure in real time the change of the amplitude and phase of the output voltage and, thus, the electrical properties of living cells. We perform the cell classification in the human peripheral blood (PBMC) and demonstrate for the first time the possibility to discriminate monocytes and subpopulations of lymphocytes in a label-free format. Further, we demonstrate that the PBMC of acute myeloid leukemia and healthy samples grant the label free identification of the disease. Using the algorithm based on machine learning, we generated specific data patterns to discriminate healthy donors and leukemia patients. Such a solution has the potential to improve the traditional diagnostics approaches with respect to the overall cost and time effort, in a label-free format, and restrictions of the complex data analysis.

Redox Electrochemistry to Interrogate and Control Biomolecular Communication

Cells often communicate by the secretion, transport, and perception of molecules. Information conveyed by molecules is encoded, transmitted, and decoded by cells within the context of the prevailing microenvironments. Conversely, in electronics, transmission reliability and message validation are predictable, robust, and less context dependent. In turn, many transformative advances have resulted by the formal consideration of information transfer. One way to explore this potential for biological systems is to create bio-device interfaces that facilitate bidirectional information transfer between biology and electronics. Redox reactions enable this linkage because reduction and oxidation mediate communication within biology and can be coupled with electronics. By manipulating redox reactions, one is able to combine the programmable features of electronics with the ability to interrogate and modulate biological function. In this review, we examine methods to electrochemically interrogate the various components of molecular communication using redox chemistry and to electronically control cell communication using redox electrogenetics.

Proliferation and Cluster Analysis of Neurons and Glial Cell Organization on Nanocolumnar TiN Sub-Strates

Biomaterials employed for neural stimulation, as well as brain/machine interfaces, offer great perspectives to combat neurodegenerative diseases, while application of lab-on-a-chip devices such as multielectrode arrays is a promising alternative to assess neural function in vitro. For bioelectronic monitoring, nanostructured microelectrodes are required, which exhibit an increased surface area where the detection sensitivity is not reduced by the self-impedance of the electrode. In our study, we investigated the interaction of neurons (SH-SY5Y) and glial cells (U-87 MG) with nanocolumnar titanium nitride (TiN) electrode materials in comparison to TiN with larger surface grains, gold, and indium tin oxide (ITO) substrates. Glial cells showed an enhanced proliferation on TiN materials; however, these cells spread evenly distributed over all the substrate surfaces. By contrast, neurons proliferated fastest on nanocolumnar TiN and formed large cell agglomerations. We implemented a radial autocorrelation function of cellular positions combined with various clustering algorithms. These combined analyses allowed us to quantify the largest cluster on nanocolumnar TiN; however, on ITO and gold, neurons spread more homogeneously across the substrates. As SH-SY5Y cells tend to grow in clusters under physiologic conditions, our study proves nanocolumnar TiN as a potential bioactive material candidate for the application of microelectrodes in contact with neurons. To this end, the employed K-means clustering algorithm together with radial autocorrelation analysis is a valuable tool to quantify cell-surface interaction and cell organization to evaluate biomaterials' performance in vitro.

Accurate modeling of a biological nanopore with an extended continuum framework

Despite the broad success of biological nanopores as powerful instruments for the analysis of proteins and nucleic acids at the single-molecule level, a fast simulation methodology to accurately model their nanofluidic properties is currently unavailable. This limits the rational engineering of nanopore traits and makes the unambiguous interpretation of experimental results challenging. Here, we present a continuum approach that can faithfully reproduce the experimentally measured ionic conductance of the biological nanopore Cytolysin A (ClyA) over a wide range of ionic strengths and bias potentials. Our model consists of the extended Poisson-Nernst-Planck and Navier-Stokes (ePNP-NS) equations and a computationally efficient 2D-axisymmetric representation for the geometry and charge distribution of the nanopore. Importantly, the ePNP-NS equations achieve this accuracy by self-consistently considering the finite size of the ions and the influence of both the ionic strength and the nanoscopic scale of the pore on the local properties of the electrolyte. These comprise the mobility and diffusivity of the ions, and the density, viscosity and relative permittivity of the solvent. Crucially, by applying our methodology to ClyA, a biological nanopore used for single-molecule enzymology studies, we could directly quantify several nanofluidic characteristics difficult to determine experimentally. These include the ion selectivity, the ion concentration distributions, the electrostatic potential landscape, the magnitude of the electro-osmotic flow field, and the internal pressure distribution. Hence, this work provides a means to obtain fundamental new insights into the nanofluidic properties of biological nanopores and paves the way towards their rational engineering.

Non-Carbon 2D Materials-Based Field-Effect Transistor Biosensors: Recent Advances, Challenges, and Future Perspectives

In recent years, field-effect transistors (FETs) have been very promising for biosensor applications due to their high sensitivity, real-time applicability, scalability, and prospect of integrating measurement system on a chip. Non-carbon 2D materials, such as transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), black phosphorus (BP), and metal oxides, are a group of new materials that have a huge potential in FET biosensor applications. In this work, we review the recent advances and remarkable studies of non-carbon 2D materials, in terms of their structures, preparations, properties and FET biosensor applications. We will also discuss the challenges facing non-carbon 2D materials-FET biosensors and their future perspectives.

Recent advances in developing biosensing based platforms for neonatal sepsis

Neonatal sepsis is a bloodstream infection primarily caused by Escherichia coli (E. coli), Group B Streptococcus (GBS), Listeria monocytogenes, Haemophilus influenzae, S. aureus, Klebsiella spp. and non-typhoidal Salmonella bacteria. Neonatal Sepsis is referred as a critical response to the infection in the neonatal period that can lead to the failure of body organs and thereby causing damage to the tissues resulting in death of the neonates. Nearly 4 million deaths across the world are occurred due to neonatal sepsis infections. In order to prevent the bloodstream infections in the neonates, it is indispensable to diagnose the disease properly for appropriate treatment during the point of care. Numerous studies have been reported to identify major biomarkers associated with neonatal sepsis including Serum Amyloid A (SAA), C - reactive protein (CRP), Procalcitonin (PCT) and Lipopolysaccharide-binding protein (LBP). Distinct diagnostic platforms have also been developed detecting the presence of bloodstream infections including electrochemical, potentiometric, and impedimetric sensors. Recently, electrochemical biosensors with the integration of nanomaterials have emerged as a better platform for neonatal sepsis biomarkers detection. This review article summarizes the diverse screening platforms, evaluation parameters, and new advances based on implications of nanomaterials for the development of biosensors detecting neonatal sepsis infections. The review further elucidates the significance and future scope of distinctive platforms which are predominantly associated with detection of neonatal sepsis.

Recent Advances in Biomolecule-Nanomaterial Heterolayer-Based Charge Storage Devices for Bioelectronic Applications

With the acceleration of the Fourth Industrial Revolution, the development of information and communications technology requires innovative information storage devices and processing devices with low power and ultrahigh stability. Accordingly, bioelectronic devices have gained considerable attention as a promising alternative to silicon-based devices because of their various applications, including human-body-attached devices, biomaterial-based computation systems, and biomaterial-nanomaterial hybrid-based charge storage devices. Nanomaterial-based charge storage devices have witnessed considerable development owing to their similarity to conventional charge storage devices and their ease of applicability. The introduction of a biomaterial-to-nanomaterial-based system using a combination of biomolecules and nanostructures provides outstanding electrochemical, electrical, and optical properties that can be applied to the fabrication of charge storage devices. Here, we describe the recent advances in charge storage devices containing a biomolecule and nanoparticle heterolayer including (1) electrical resistive charge storage devices, (2) electrochemical biomemory devices, (3) field-effect transistors, and (4) biomemristors. Progress in biomolecule-nanomaterial heterolayer-based charge storage devices will lead to unprecedented opportunities for the integration of information and communications technology, biotechnology, and nanotechnology for the Fourth Industrial Revolution.

Vertical nanowire array-based biosensors: device design strategies and biomedical applications

Biosensors have been extensively studied in the areas of biology, electronics, chemistry, biotechnology, medicine, and various engineering fields. The interdisciplinarity creates an ideal platform for scientists to analyze biological species and chemical materials in a direct, efficient, and sensitive manner; this is expected to revolutionize the life sciences, basic medicine, and the healthcare industry. To carry out high-performance biosensing, nanoprobes - with specific nanoscale properties - have been proposed for ultrasensitive and in situ monitoring/detection of tracer biomolecules, cellular behavior, cellular microenvironments, and electrophysiological activity. Here, we review the development of vertical nanowire (VNW) array-based devices for the effective collection of biomedical information at the molecular level, extracellular level, and intracellular level. In particular, we summarize VNW-based technologies in the aspects of detecting biochemical information, cellular information, and bioelectrical information, all of which facilitate the understanding of fundamental biology and development of therapeutic techniques. Finally, we present a conclusion and prospects for the development of VNW platforms in practical biomedical applications, and we identify the challenges and opportunities for VNW-based biosensor systems in future biological research.

Wafer-Scale Uniform Carbon Nanotube Transistors for Ultrasensitive and Label-Free Detection of Disease Biomarkers

Carbon nanotube (CNT) field-effect transistor (FET)-based biosensors have shown great potential for ultrasensitive biomarker detection, but challenges remain, which include unsatisfactory sensitivity, difficulty in stable functionalization, incompatibility with scalable fabrication, and nonuniform performance. Here, we describe ultrasensitive, label-free, and stable FET biosensors built on polymer-sorted high-purity semiconducting CNT films with wafer-scale fabrication and high uniformity. With a floating gate (FG) structure using an ultrathin Y₂O₃ high-κ dielectric layer, the CNT FET biosensors show amplified response and improved sensitivity compared with those sensors without Y₂O₃, which is attributed to the chemical gate-coupling effect dominating the sensor response. The CNT FG-FETs are modified to selectively detect specific disease biomarkers, namely, DNA sequences and microvesicles, with theoretical record detection limits as low as 60 aM and 6 particles/mL, respectively. Furthermore, the biosensors exhibit highly uniform performance over the 4 in. wafer as well as superior bias stress stability. The FG CNT FET biosensors could be extended as a universal biosensor platform for the ultrasensitive detection of multiple biological molecules and applied in highly integrated and multiplexed all CNT-FET-based sensor architectures.

Photo-cross-linkable, insulating silk fibroin for bioelectronics with enhanced cell affinity

Bioelectronic scaffolds that support devices while promoting tissue integration could enable tissue hybrids with augmented electronic capabilities. Here, we demonstrate a photo-cross-linkable silk fibroin (PSF) derivative and investigate its structural, electrical, and chemical properties. Lithographically defined PSF films offered tunable thickness and <1-µm spatial resolution and could be released from a relief layer yielding freestanding scaffolds with centimeter-scale uniformity. These constructs were electrically insulating; multielectrode arrays with PSF-passivated interconnects provided stable electrophysiological readouts from HL-1 cardiac model cells, brain slices, and hearts. Compared to SU8, a ubiquitous biomaterial, PSF exhibited superior affinity toward neurons which we attribute to its favorable surface charge and enhanced attachment of poly-d-lysine adhesion factors. This finding is of significant importance in bioelectronics, where tight junctions between devices and cell membranes are necessary for electronic communication. Collectively, our findings are generalizable to a variety of geometries, devices, and tissues, establishing PSF as a promising bioelectronic platform.

Schottky-Contacted Nanowire Sensors

The progress of the Internet-of-Things in the past few years has necessitated the support of high-performance sensors. Schottky-contacted nanowire sensors have attracted considerable attention owing to their high sensitivity and fast response time. Their progress is reviewed here, based on several kinds of important nanowires, for applications such as bio/chemical sensors, gas sensors, photodetectors, and strain sensors. Although Schottky-contacted nanowire sensors deliver excellent performance in these fields, they can be further improved by various methods, including defect engineering, surface modification, the piezotronic effect, and the piezophototronic effect, all of which are discussed here. With regard to practical applications, further efforts are required to address challenges such as the stability, selectivity, ultrafast response, multifunctionality, flexibility, distributed energy supply, and sustainability of Schottky-contacted nanowire sensors. Finally, future perspectives and solutions are discussed.

Planar Growth, Integration, and Applications of Semiconducting Nanowires

Silicon and other inorganic semiconductor nanowires (NWs) have been extensively investigated in the last two decades for constructing high-performance nanoelectronics, sensors, and optoelectronics. For many of these applications, these tiny building blocks have to be integrated into the existing planar electronic platform, where precise location, orientation, and layout controls are indispensable. In the advent of More-than-Moore's era, there are also emerging demands for a programmable growth engineering of the geometry, composition, and line-shape of NWs on planar or out-of-plane 3D sidewall surfaces. Here, the critical technologies established for synthesis, transferring, and assembly of NWs upon planar surface are examined; then, the recent progress of in-plane growth of horizontal NWs directly upon crystalline or patterned substrates, constrained by using nanochannels, an epitaxial interface, or amorphous thin film precursors is discussed. Finally, the unique capabilities of planar growth of NWs in achieving precise guided growth control, programmable geometry, composition, and line-shape engineering are reviewed, followed by their latest device applications in building high-performance field-effect transistors, photodetectors, stretchable electronics, and 3D stacked-channel integration.

Hofmeister-Effect-Guided Ionohydrogel Design as Printable Bioelectronic Devices

Bioelectronic platforms convert biological signals into electrical signals by utilizing biocatalysts that provide tools to monitor the activity of cells and tissues. Traditional conducting materials such as solid conductors and conducting polymers are confronted with a great challenge in sophisticated production processes and mismatch at biological tissues-machine interfaces. Furthermore, the biocatalyst, the key functional component in the electron-transfer reaction for bio-signal detection denatures easily in an ionic conductive solution. Herein, a bionic strategy is elaborately developed to synthesize an ionohydrogel bioelectronic platform that possesses extracellular-matrix-like habitat by employing hydrated ionic liquids (HILs) as ionic solvent and bioprotectant. This strategy realizes an integration of ionic and enzymatic electronic circuits and minimization of the disparities between tissues and artificial machines. The Hofmeister effect of HILs on enzyme proteins and polymer chains ensures the high bioactivity of the enzymes and greatly improves the mechanical properties of the ionohydrogels. Moreover, hydrogen bonds formed by ILs, water, and polymer chains greatly improve the water-retention of the ionohydrogel and give it more practical significance. Consequently, the promising ionohydrogel is partly printed and fabricated into wearable devices as a pain-free humoral components monitor and a wireless motion-sensor.

Dual-emission fluorescent silicon nanoparticle-based nanothermometer for ratiometric detection of intracellular temperature in living cells

In this article, we present a kind of dual-emission fluorescent nanothermometer, which is made of europium (Eu3+)-doped silicon nanoparticles (Eu@SiNPs), allowing the detection of intracellular temperature in living cells with high accuracy. In particular, the presented SiNP-based thermometer features dual-emission fluorescence (blue (455 nm) and red (620 nm) emission), negligible toxicity (cell viability of treated cells remains above 90% during 24 h of treatment) and robust photostability in living cells (i.e., preserving >90% of fluorescence intensity after 45 min of continuous UV irradiation). More significantly, the fluorescence intensity of the Eu@SiNPs exhibits a linear ratiometric temperature response in a broad range from 25 to 70 °C. Taking advantage of these attractive merits, the Eu@SiNP-based nanothermometer is able to accurately (∼4.5% change per °C) determine dynamic changes in intracellular temperature in a quantitative and long-term (i.e., 30 min) manner.

Soft-Hard Composites for Bioelectric Interfaces

Bioelectric devices can probe fundamental biological dynamics and improve the lives of human beings. However, direct application of traditional rigid electronics onto soft tissues can cause signal transduction and biocompatibility issues. One common mitigation strategy is the use of soft-hard composites to form more biocompatible interfaces with target cells or tissues. Here, we identify several soft-hard composite designs in naturally occurring systems. We use these designs to categorize the existing bioelectric interfaces and to suggest future opportunities. We discuss the utility of soft-hard composites for a variety of interfaces, such as in vitro and in vivo electronic or optoelectronic sensing and genetic and non-genetic modulation. We end the review by proposing new soft-hard composites for future bioelectric studies.

Molecular Features for Probing Small Amphiphilic Molecules with Self-Assembled Monolayer-Protected Nanoparticles

The sensing of small molecules poses the challenge of developing devices able to discriminate between compounds that may be structurally very similar. Here, attention has been paid to the use of self-assembled monolayer (SAM)-protected gold nanoparticles since they enable a modular approach to tune single-molecule affinity and selectivity simply by changing functional moieties (i.e., covering ligands), along with multivalent molecular recognition. To date, the discovery of monolayers suitable for a specific molecular target has relied on trial-and-error approaches, with ligand chemistry being the main criterion used to modulate selectivity and sensitivity. By using molecular dynamics, we showcase that either individual molecular characteristics and/or collective features such as ligand flexibility, monolayer organization, ligand local ordering, and interfacial solvent properties can also be exploited conveniently. The knowledge of the molecular mechanisms that drive the recognition of small molecules on SAM-covered nanoparticles will critically expand our ability to manipulate and control such supramolecular systems.

Biological Interfaces, Modulation, and Sensing with Inorganic Nano-Bioelectronic Materials

The last several years have seen a large and increasing interest in scientific developments that combine methods and materials from nanotechnology with questions and applications in bioelectronics. This follows with a number of broader trends: the rapid increase in functionality for materials at the nanoscale; a growing recognition of the importance of electric fields in diverse physiological processes; and continuous improvements in technologies that are naturally complementary with bioelectronics, such as optogenetics. Here, a progress report is provided on several of the most exciting recent developments in this field. The three critical functions of biointerface formation, biological modulation, and biological sensing using newly developed nanoscale materials are considered.

Nano-enabled cellular engineering for bioelectric studies

Engineered cells have opened up a new avenue for scientists and engineers to achieve specialized biological functions. Nanomaterials, such as silicon nanowires and quantum dots, can establish tight interfaces with cells either extra- or intracellularly, and they have already been widely used to control cellular functions. The future exploration of nanomaterials in cellular engineering may reveal numerous opportunities in both fundamental bioelectric studies and clinic applications. In this review, we highlight several nanomaterials-enabled non-genetic approaches to fabricating engineered cells. First, we briefly review the latest progress in engineered or synthetic cells, such as protocells that create cell-like behaviors from nonliving building blocks, and cells made by genetic or chemical modifications. Next, we illustrate the need for non-genetic cellular engineering with semiconductors and present some examples where chemical synthesis yields complex morphology or functions needed for biointerfaces. We then provide discussions in detail about the semiconductor nanostructure-enabled neural, cardiac, and microbial modulations. We also suggest the need to integrate tissue engineering with semiconductor devices to carry out more complex functions. We end this review by providing our perspectives for future development in non-genetic cellular engineering.

3D printed nanomaterial-based electronic, biomedical, and bioelectronic devices

The ability to seamlessly integrate functional materials into three-dimensional (3D) constructs has been of significant interest, as it can enable the creation of multifunctional devices. Such integration can be achieved with a multiscale, multi-material 3D printing strategy. This technology has enabled the creation of unique devices such as personalized tissue regenerative scaffolds, biomedical implants, 3D electronic devices, and bionic constructs which are challenging to realize with conventional manufacturing processes. In particular, the incorporation of nanomaterials into 3D printed devices can endow a wide range of constructs with tailorable mechanical, chemical, and electrical functionalities. This review highlights the advances and unique possibilities in the fabrication of novel electronic, biomedical, and bioelectronic devices that are realized by the synergistic integration of nanomaterials with 3D printing technologies.

Multi-Frequency Resonance Behaviour of a Si FractalNEMS Resonator

Novel Si-based nanosize mechanical resonator has been top-down fabricated. The shape of the resonating body has been numerically derived and consists of seven star-polygons that form a fractal structure. The actual resonator is defined by focused ion-beam implantation on a SOI wafer where its 18 vertices are clamped to nanopillars. The structure is suspended over a 10 μm trench and has width of 12 μm. Its thickness of 0.040 μm is defined by the fabrication process and prescribes Young’s modulus of 76 GPa which is significantly lower than the value of the bulk material. The resonator is excited by the bottom Si-layer and the interferometric characterisation confirms broadband frequency response with quality factors of over 800 for several peaks between 2 MHz and 16 MHz. COMSOL FEM software has been used to vary material properties and residual stress in order to fit the eigenfrequencies of the model with the resonance peaks detected experimentally. Further use of the model shows how the symmetry of the device affects the frequency spectrum. Also, by using the FEM model, the possibility for an electrical read out of the device was tested. The experimental measurements and simulations proved that the device can resonate at many different excitation frequencies allowing multiple operational bands. The size, and the power needed for actuation are comparable with the ones of single beam resonator while the fractal structure allows much larger area for functionalisation.

Radial Nanowire Assemblies under Rotating Magnetic Field Enabled Efficient Charge Separation

Developing efficient charge separation strategies is essential to achieve high-power conversion efficiency in the fields of chemistry, biology, and material science. Herein, we develop a facile strategy for fabrication of unique wafer-scale radial nanowire assemblies by exploiting shear force in rotary solution. The assembly mechanism can be well revealed by the large-scale stochastic dynamics simulation. Free electrons can be rapidly generated to produce quantitatively tunable current output when the radial nanowire assemblies rotate under the magnetic field. Moreover, the photoconductive performance of the radial semiconductor nanowire assemblies can be remarkably enhanced as the electron-hole recombination was retrained by the efficient charge separation under the rotating magnetic field. Such large-scale unique nanowire assemblies will facilitate the design of an efficient charge separation process in biosystem, sensors, and photocatalysis.

Flexible Electrochemical Bioelectronics: The Rise of In Situ Bioanalysis

The amalgamation of flexible electronics in biological systems has shaped the way health and medicine are administered. The growing field of flexible electrochemical bioelectronics enables the in situ quantification of a variety of chemical constituents present in the human body and holds great promise for personalized health monitoring owing to its unique advantages such as inherent wearability, high sensitivity, high selectivity, and low cost. It represents a promising alternative to probe biomarkers in the human body in a simpler method compared to conventional instrumental analytical techniques. Various bioanalytical technologies are employed in flexible electrochemical bioelectronics, including ion-selective potentiometry, enzymatic amperometry, potential sweep voltammetry, field-effect transistors, affinity-based biosensing, as well as biofuel cells. Recent key innovations in flexible electrochemical bioelectronics from electrochemical sensing modalities, materials, systems, fabrication, to applications are summarized and highlighted. The challenges and opportunities in this field moving forward toward future preventive and personalized medicine devices are also discussed.