Biological Sensors Research Articles

Developments in Localized Surface Plasmon Resonance

AbstractLocalized surface plasmon resonance (LSPR) is a nanoscale phenomenon associated with noble metal nanostructures that has long been studied and has gained considerable interest in recent years. These resonances produce sharp spectral absorption and scattering peaks, along with strong electromagnetic near-field enhancements. Over the past decade, advancements in the fabrication of noble metal nanostructures have propelled significant developments in various scientific and technological aspects of LSPR. One notable application is the detection of molecular interactions near the nanoparticle surface, observable through shifts in the LSPR spectral peak. This document provides an overview of this sensing strategy. Given the broad and expanding scope of this topic, it is impossible to cover every aspect comprehensively in this review. However, we aim to outline major research efforts within the field and review a diverse array of relevant literature. We will provide a detailed summary of the physical principles underlying LSPR sensing and address some existing inconsistencies in the nomenclature used. Our discussion will primarily focus on LSPR sensors that employ metal nanoparticles, rather than on those utilizing extended, fabricated structures. We will concentrate on sensors where LSPR acts as the primary mode of signal transduction, excluding hybrid strategies like those combining LSPR with fluorescence. Additionally, our examination of biological LSPR sensors will largely pertain to label-free detection methods, rather than those that use metal nanoparticles as labels or as means to enhance the efficacy of a label. In the subsequent section of this review, we delve into the analytical theory underpinning LSPR, exploring its physical origins and its dependency on the material properties of noble metals and the surrounding refractive index. We will discuss the behavior of both spherical and spheroidal particles and elaborate on how the LSPR response varies with particle aspect ratio. Further, we detail the fundamentals of nanoparticle-based LSPR sensing. This includes an exploration of single-particle and ensemble measurements and a comparative analysis of scattering, absorption, and extinction phenomena. The discussion will extend to how these principles are applied in practical sensing scenarios, highlighting the key experimental approaches and measurement techniques.

Ultra-Stretchable, Adhesive, Conductive, and Antifreezing Multinetwork Borate Ester-Based Hydrogel for Wearable Strain Sensor and VOC Absorption.

Hydrogels based on borate ester bonds exhibit remarkable tensile strength and self-healing ability, which make them a promising material for various biological research and strain sensor applications. However, in order to meet the practical application of hydrogel strain sensors, they must also show high conductivity, frost resistance, and proper adhesion, which is still a continuous challenge. Herein, a triple network hydrogel was prepared using poly(vinyl alcohol) (PVA) as the first network, ethylene imine polymer (PEI) as the second network, and poly(acrylamide-co-acrylic acid) copolymer (denoted as P(AM-Co-AA)) as the third network. 3-Carboxy-4-fluorophenylboronic acid (CFBS) was used as the cross-linking agent, glycerol (GL) was added to improve low-temperature resistance, and sodium chloride (NaCl) was incorporated to enhance electrical conductivity. The resulting PVA-CFBS@PEI@P(AM-Co-AA) triple network hydrogel exhibited impressive mechanical properties, including ultra tensile strength (4100%, 266.8 kPa), high toughness (6.5 MJ/m3), and low-temperature resistance (-60 °C). Additionally, it demonstrated high conductivity (σ = 1.83 mS/cm). The incorporation of CFBS endowed the hydrogel with excellent self-healing ability, while GL improved low-temperature resistance and strain sensing sensitivity (gauge factor (GF) = 2.8 (0-300%), GF = 5.6 (300-600%), GF = 8.7 (600-1000%)). The prepared hydrogel sensor can repetitively detect and differentiate between a wide range of human activities such as joint movements, frowning, and smiling. Additionally, the hydrogel demonstrated favorable mechanical properties at -20 °C (good adhesion, tensile strength: 1169.8%, 1.2 MPa; conductivity: 0.71 mS/cm, and strain sensing coefficient: GF = 1.3), making it suitable for applications in low-temperature environments. Furthermore, it also functions as an exceptional adsorbent, capable of selectively absorbing volatile organic compounds at high capacity (e.g., methanol: 1.80 g/g; acetone: 1.50 g/g).

Preparation of Gradient HEA-DAC/HPA Hydrogels by Limited Domain Swelling Method.

Hydrogels are widely used in biological dressing, tissue scaffolding, drug delivery, sensors, and other promising applications owing to their water-rich soft structures, biocompatibility, and adjustable mechanical properties. However, most of the conventional hydrogels are isotropic. The anisotropic structures existed widely in the organizational structure of plants and animals, which played a crucial role in biological systems. In this work, a method of limited domain swelling to prepare anisotropic hydrogels is proposed. Through spatially controlled swelling, the extension direction of hydrogels can be limited by a tailored mold, further achieving anisotropic hydrogels with concentration gradients. The external solution serves as a swelling solution to promote swelling and extension of the hydrogel matrix in a mold which can control the extension direction. Due to the diversity of external solutions, the method can be applied to prepare a variety of stimulus-responsive polymers. The limited domain swelling method is promising for the construction of anisotropic hydrogels with different structures and properties.

Functionalization of Si‐ and Al‐Based Materials with Phosphorus Dendrimers and their Properties

AbstractThe interactions of dendrimers having a phosphorus atom at each branching point, of type poly(phosphorhydrazone) (PPH), with different types of materials based on silicon and aluminum are reviewed. These dendrimers can be used for the functionalization of solid surfaces at the nanoscale, either by covalent immobilization, or by electrostatic interactions, especially for constructing perfectly controlled multi‐layers by layer‐by‐layer (LbL) deposit. The properties of such hybrid materials as chemical sensors, as very sensitive biological sensors, as well as substrates for the growing of cells are described. The PPH dendrimers can also be embedded inside materials. The resulting hybrid materials have been used for the capture of pollutants, in particular CO2 in air and chromate and methylene blue in waste water.

Nanomedicines with Versatile GSH-Responsive Linkers for Cancer Theranostics.

Glutathione (GSH)-responsive nanomedicines have generated significant interest in biochemistry, oncology, and material sciences due to their diverse applications, including chemical and biological sensors, diagnostics, and drug delivery systems. The effectiveness of these smart GSH-responsive nanomedicines depends critically on the choice of GSH-responsive linkers. Despite their crucial role, comprehensive reviews of GSH-responsive linkers are scarce, revealing a gap in the current literature. This review addresses this gap by systematically summarizing various GSH-responsive linkers and exploring their potential applications in cancer treatment. We provide an overview of the mechanisms of action of these linkers and their bioapplications, evaluating their advantages and limitations. The insights presented aim to guide the development of advanced GSH-responsive agents for cancer diagnosis and therapy.

Dirac Electrons with Molecular Relaxation Time at Electrochemical Interface between Graphene and Water.

The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (Cm) at this interface with the gate voltage Vgate ≈ 0.1 V follows approximate laws Cm~T1.2 and Cm~T0.11 (T is Vgate period) in frequency ranges (1000-50,000) Hz and (0.02-300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (Cint) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (Cm) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (Cdl) and by the graphene quantum capacitance (Cq), and it also implies that Cint is mostly charged. We have also found a voltage dependence of Cm below 10 Hz, which is likely related to the voltage dependence of Cq. The observation of this effect only at low frequencies indicates that Cq relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges.

In Situ Growth of Nanorod-Shaped Ni,Co-MOF on Mo2CTx MXene Surface to Realize Enhanced Energy Storage for Supercapacitors.

Mo2CTx MXene materials, known for their high conductivity and abundant surface functional groups, are widely utilized as electrode materials in supercapacitors. However, their tendency to stack during electrochemical energy storage hinders their performance. The in situ growth of nanorod-shaped Ni,Co bimetallic metal-organic frameworks (Ni,Co-MOF) on Mo2CTx MXene effectively mitigates this stacking. With their porous structure and high specific surface area, MOFs excel in energy storage, and bimetallic MOFs outperform monometallic ones. The synergy between Mo2CTx MXene and Ni,Co-MOF yields an outstanding performance. In a three-electrode system with 1 M KOH, the Mo2CTx/Ni,Co-MOF composite shows a specific capacitance of 58 mAh g-1 (56.26 mAh cm-3) at 1 A g-1. When used in a Mo2CTx/Ni,Co-MOF//AC asymmetric supercapacitor, it achieves an energy density of 22.7 Wh kg-1(0.022 Wh cm-3) at a power density of 293 W kg-1 (0.284 W cm-3). Future work will focus on enhancing synthesis methods, exploring different bimetallic combinations, and optimizing electrode designs for gas sensors, batteries, fuel cells, biological sensors, and so on, with outstanding performance and sustainability.

Critical review on toxic contaminants in surface water ecosystem: sources, monitoring, and its impact on human health.

Surface water pollution is a critical and urgent global issue that demands immediate attention. Surface water plays a crucial role in supporting and sustaining life on the earth, but unfortunately, till now, we have less understanding of its spatial and temporal dynamics of discharge and storage variations at a global level. The contamination of surface water arises from various sources, classified into point and non-point sources. Point sources are specific, identifiable origins of pollution that release pollutants directly into water bodies through pipes or channels, allowing for easier identification and management, e.g., industrial discharges, sewage treatment plants, and landfills. However, non-point sources originate from widespread activities across expansive areas and present challenges due to its diffuse nature and multiple pathways of contamination, e.g., agricultural runoff, urban storm water runoff, and atmospheric deposition. Excessive accumulation of heavy metals, persistent organic pollutants, pesticides, chlorination by-products, pharmaceutical products in surface water through different pathways threatens food quality and safety. As a result, there is an urgent need for developing and designing new tools for identifying and quantifying various environmental contaminants. In this context, chemical and biological sensors emerge as fascinating devices well-suited for various environmental applications. Numerous chemical and biological sensors, encompassing electrochemical, magnetic, microfluidic, and biosensors, have recently been invented by hydrological scientists for the detection of water pollutants. Furthermore, surface water contaminants are monitored through different sensors, proving their harmful effects on human health.

Recent research progress in tetrodotoxin detection and quantitative analysis methods.

Tetrodotoxin (TTX) is a highly potent and widely distributed ion-channel marine neurotoxin; it has no specific antidote and poses a great risk to human health. Therefore, detecting and quantifying TTX to effectively implement prevention strategies is important for food safety. The development of novel and highly sensitive, highly specific, rapid, and simple techniques for trace TTX detection has attracted widespread attention. This review summarizes the latest advances in the detection and quantitative analysis of TTX, covering detection methods based on biological and cellular sensors, immunoassays and immunosensors, aptamers, and liquid chromatography-mass spectrometry. It further discusses the advantages and applications of various detection technologies developed for TTX and focuses on the frontier areas and development directions of TTX detection, providing relevant information for further investigations.

Embedded Hybrid-Dimensional Heterointerface for Filament Modulation in 2D Material-Based Artificial Nociceptor.

Nociceptors are key sensory receptors that transmit warning signals to the central nervous system in response to painful stimuli. This fundamental process is emulated in an electronic device by developing a novel artificial nociceptor with an ultrathin, nonstoichiometric gallium oxide (GaOx)-silicon oxide heterostructure. A large-area 2D-GaOx film is printed on a substrate through liquid metal printing to facilitate the production of conductive filaments. This nociceptive structure exhibits a unique short-term temporal response following stimulation, enabling a facile demonstration of threshold-switching physics. The developed heterointerface 2D-GaOx film enables the fabrication of fast-switching, low-energy, and compliance-free 2D-GaOx nociceptors, as confirmed through experiments. The accumulation and extrusion of Ag in the oxide matrix are significant for inducing plastic changes in artificial biological sensors. High-resolution transmission electron microscopy and electron energy loss spectroscopy demonstrate that Ag clusters in the material dispersed under electrical bias and regrouped spontaneously when the bias is removed owing to interfacial energy minimization. Moreover, 2D nociceptors are stable; thus, heterointerface engineering can enable effective control of charge transfer in 2D heterostructural devices. Furthermore, the diffusive 2D-GaOx device and its Ag dynamics enable the direct emulation of biological nociceptors, marking an advancement in the hardware implementation of artificial human sensory systems.

Modeling and Sensitivity Estimation of a Dual Cavity Source Pocket-Based Charge Plasma Tunneling FET for Label-Free Biological Molecule Detection

A dual-source cavity charge plasma tunneling FET (DSC-SP-CPTFET) with SiGe Pocket is proposed, and its effectiveness as a biological sensor for label-free detection is explored. The fabrication complexity and cost have been reduced by using the charge-plasma concept. For improved sensing, an etched nanocavity is added to the upper and lower of the source metal section. The high-k (HfO2) gate oxide and minimal energy gap (Si0.6Ge0.4) alloy with a 40% mole fraction improve the current sensitivity by enhancing the drain current gradient. The sensitivity of the suggested biological sensor is assessed here for several neutral biological molecules, such as Gelatin, Keratin, Biotin, and 3-Aminopropyl-Triethoxysilane (APTES). Deoxyribonucleic acid (DNA), a charged biological molecule, is also considered with varying positive and negative charge densities. The suggested biological sensor shows a (SIDS)max of 2.21 × 1010 and a Sratio of 3.11 × 109 for biological molecules with higher dielectric constant at room temperature. Different electrostatic performances are estimated in the ON state, including energy band, electron (e-) BTBT rate, electrical field, and IDS-VGS characteristics. In addition, the proposed biological sensor provides a much superior drain current sensitivity (SIDS), current ratio sensitivity (Sratio), and average SS sensitivity (SSS) performance in the presence of both charged and neutral biological molecules.

From “stars” to nano: Porous poly(ethylene glycol) hydrogel films and nanosheets as a versatile platform for sensing and nanofabrication

AbstractThe use of bioinert materials is crucially important for medicine and bioengineering. The most popular systems in this context are oligo- and poly(ethylene glycols) (OEGs and PEGs), applied generally in different forms as bulk materials, thin films, and functional molecular groups. Here, I review the fabrication, properties, and applications of porous hydrogel PEG films (PHFs) and nanosheets (PHNs) formed by thermally activated crosslinking of amino- and epoxy-terminated, star-branched PEG oligomers with variable molecular weight. These systems possess various useful characteristics, including tunable thickness and porosity, hydrogel properties, bioinertness, robustness, and extreme elasticity. They can serve as the basis for composite materials, advanced nanofabrication, and lithography, bioinert supports for high-resolution transmission electron microscopy, susceptible elements in micro-electromechanical systems, and basic building blocks of temperature, humidity, chemical, and biological sensors. Representative examples of the respective applications are provided. Even though these examples span a broad field-from nanoengineering to biosensing, the applications of the PHFs and PHNs are certainly not limited to these cases but can be specifically adapted and extended to other fields, such as tissue engineering and drug delivery, relying on versatility and tunability of these systems.

Construction of Multiply Guaranteed DNA Sensors for Biological Sensing and Bioimaging Applications.

Nucleic acids exhibit exceptional functionalities for both molecular recognition and catalysis, along with the capability of predictable assembly through strand displacement reactions. The inherent programmability and addressability of DNA probes enable their precise, on-demand assembly and accurate execution of hybridization, significantly enhancing target detection capabilities. Decades of research in DNA nanotechnology have led to advances in the structural design of functional DNA probes, resulting in increasingly sensitive and robust DNA sensors. Moreover, increasing attention has been devoted to enhancing the accuracy and sensitivity of DNA-based biosensors by integrating multiple sensing procedures. In this review, we summarize various strategies aimed at enhancing the accuracy of DNA sensors. These strategies involve multiple guarantee procedures, utilizing dual signal output mechanisms, and implementing sequential regulation methods. Our goal is to provide new insights into the development of more accurate DNA sensors, ultimately facilitating their widespread application in clinical diagnostics and assessment.

3D Printed Interdigitated Electrodes for Cardiac Biomarker Detection.

The identification of biomarkers has significant benefits for early disease diagnosis and treatment. Hence, there is an increasing demand for low-cost, disposable point-of-care diagnostic devices for rapid and specific biomarker detection, with good sensitivity and range. Interdigitated electrodes (IDEs) are among the most widely used transducers, especially in chemical and biological sensors, because of their high sensitivity, low cost, and straightforward manufacturing procedure. In this work, a simple 3D printed IDE structure has been developed for cardiac troponin I detection to indicate the risk of acute myocardial infarction (AMI). IDEs have been fabricated using 3D printing technique and the electrically conductive composite polylactic acid (PLA) filament being utilized for the fabrication of electrodes. The demonstrated cardiac troponin I sensor has a calculated quantification limit and detection limit of 0.233 ng ml-1 and 76.97 pg ml-1, respectively which are clinically significant ranges for AMI identification. Electrochemical analytical techniques, such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), were carried out for the detection of analyte concentration. Furthermore, using this fabrication methodology IDEs can be fabricated for under US$ 0.4 which can be utilized to detect several other biomarkers.

The Application of Multi-Parameter Multi-Modal Technology Integrating Biological Sensors and Artificial Intelligence in the Rapid Detection of Food Contaminants.

Against the backdrop of continuous socio-economic development, there is a growing concern among people about food quality and safety. Individuals are increasingly realizing the critical importance of healthy eating for bodily health; hence the continuous rise in demand for detecting food pollution. Simultaneously, the rapid expansion of global food trade has made people's pursuit of high-quality food more urgent. However, traditional methods of food analysis have certain limitations, mainly manifested in the high degree of reliance on personal subjective judgment for assessing food quality. In this context, the emergence of artificial intelligence and biosensors has provided new possibilities for the evaluation of food quality. This paper proposes a comprehensive approach that involves aggregating data relevant to food quality indices and developing corresponding evaluation models to highlight the effectiveness and comprehensiveness of artificial intelligence and biosensors in food quality evaluation. The potential prospects and challenges of this method in the field of food safety are comprehensively discussed, aiming to provide valuable references for future research and practice.

High-sensitive refractive index sensor based on the long-period gratings inscribed in the tapered fiber at dispersion turning point

We demonstrated the fabrication of long-period fiber gratings (LPFGs) in the tapered single-mode fiber by CO2 laser. The phase-matching curves of the LPFGs inscribed in the tapered fiber with different waist diameters have been studied theoretically and experimentally. When the waist diameter of the tapered fiber decreased from 90 μm to 22 μm, the slope of the phase-matching curve changed dramatically. The refractive index sensitivity can be increased by inscribing the LPFGs in the tapered fiber around the dispersion turning point. A maximum refractive index sensitivity of 21702.78 nm/RIU has been achieved in the range of 1.445–1.457 for the LPFG inscribed in the tapered fiber with a waist diameter of 50 μm. This kind of LPFGs inscribing in the tapered fiber may be a good candidate for the development of refractive index based chemical and biological sensors.

New insights into the signal transduction mechanism of O2-sensing FixL and other biological heme-based sensor proteins

Recent structural and biophysical studies of O2-sensing FixL, NO-sensing soluble guanylate cyclase, and other biological heme-based sensing proteins have begun to reveal the details of their molecular mechanisms and shed light on how nature regulates important biological processes such as nitrogen fixation, blood pressure, neurotransmission, photosynthesis and circadian rhythm. The O2-sensing FixL protein from S. meliloti, the eukaryotic NO-sensing protein sGC, and the CO-sensing CooA protein from R. rubrum transmit their biological signals through gas-binding to the heme domain of these proteins, which inhibits or activates the regulatory, enzymatic domain. These proteins appear to propagate their signal by specific structural changes in the heme sensor domain initiated by the appropriate gas binding to the heme, which is then propagated through a coiled-coil linker or other domain to the regulatory, enzymatic domain that sends out the biological signal. The current understanding of the signal transduction mechanisms of O2-sensing FixL, NO-sensing sGC, CO-sensing CooA and other biological heme-based gas sensing proteins and their mechanistic themes are discussed, with recommendations for future work to further understand this rapidly growing area of biological heme-based gas sensors.

Thermal, kinetic of decomposition, theoretical and experimental photoluminescent studies of two Eu3+-betadiketonate containing the 5,5′-dimethyl-2,2′-bipyridine ancillary ligand: Preparation of two efficient OLEDs devices

The Eu3+-betadiketonate coordination compounds are intensively studied due to their intense photoluminescence, which places them as promising materials with different applications, such as ammunition markers, biological sensors, and mainly as electroluminescent materials in Organic Light Emitting Diodes (OLEDs). This work reports the synthesis, thermal and kinetic study, crystal structures, experimental and theoretical photoluminescence analysis of two new Eu3+-betadiketonates of general formula [Eu(tta)3(5,5′-dmbpy)] 1 and [Eu(btfa)3(5,5′-dmbpy)] 2, where Htta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, Hbtfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 5,5′-dmbpy = 5,5′-dimethyl-2,2′-bipyridine. Photoluminescence spectroscopy data revealed that the compounds can be sensitized directly by the metal ion or through of the excitation of the excited states of the ligand system. Due to the high quantum efficiencies found for both complexes, they were used in the preparation of two OLED devices, with these devices exhibiting excellent efficiency and color purity, making them well-suited for organic electronic applications.

Biosensors in environmental analysis of microplastics and heavy metal compounds – A review on current status and challenges

Biosensors (biological sensors) are a promising alternative to standard analytical techniques for testing and monitoring in the environment, among others, heavy metals. Biological materials that detect heavy metals include enzymes, bacteria, fungi, and plant and animal cells. The paper aimed to evaluate the possibilities of biosensor usage in environmental analysis, considering an easy and environmentally friendly analysis of individual compounds (e.g., heavy metals) or their mixtures in various samples directly in the environment, as well as continuous monitoring of these compounds. The work considers biosensors' characteristics, classification, and operation principles. Attention is paid to the possibility of using bioluminescent bacteria as biological material in a biosensor. Examples of the study of heavy metals using various biological sensors were given. It also indicates the possibility of using biosensors to determine microplastics by applying specific hormones (estrogens) receptor use and peptides as a solution or incorporating them into living microbial cells. Additionally, support was given to the use of biosensors to monitor plastics' degradation in the water environment using recombinant whole-cell microbial biosensors as detectors for plastic monomers such as acrylic acid monomers. The application of the biosensors highlighted in the paper is to shorten the time of toxicity studies by using new indicators or acceptors. However, several challenges must be overcome, such as cell viability and activity. A continuous water-monitoring system that can handle a severely toxic sample has yet to be developed in toxicity monitoring.

Polarization-independent tunable multi-band terahertz absorber based on graphene structure to design the ultra-high sensitive biosensors

In this paper, we investigated the heterogeneous structure of a multi-band perfect absorber based on graphene in the terahertz range, benefiting from polarization independence. The proposed structure comprises three layers: copper, silicon dioxide, and an inhomogeneous graphene structure with an analyte. By altering the sub-layers dimensions and the graphene slices' geometric shape, we can modify the number of bands, quality, and absorption levels. Additionally, adjusting the chemical potential of graphene enables the customization of absorption frequencies as needed. The application of this structure in biological sensors extends to the detection of proteins, viruses, and cancer cells, as well as filtering telecommunication waves and imaging. Through geometrically shaping the graphene cuts at frequencies of 4.89 THz, 9.14 THz, and 10.76 THz, absorption values of 99.54%, 99.64%, and 98.3% have been achieved, respectively. Introducing the analyte to the biosensor structure causes a shift in absorption frequency values due to varying refractive index values in different materials. This property has been utilized for biosensor design. Within the refractive index range of biological analytes (e.g., 1.3), the first band achieved a sensitivity value of 2700 GHz/RIU and FoM = 13.08, while the second band achieved a sensitivity value of 2200 GHz/RIU and FoM = 14.02. An important characteristic of this structure is its insensitivity to polarization. Simulations were conducted using Computer Simulation Technology (CST) Microwave Studio Suite 2023.