Search Results (212)

Capacitive sensors are platforms that enable label-free, real-time detection at low non-perturbing voltages. These sensors do not rely on Faradaic processes, thereby eliminating the need for redox-active species and simplifying system integration for point-of-care diagnostics. However, their sensitivity in high-ionic-strength solutions, such as bodily fluids, is limited due to a reduced Debye length and non-specific interactions. The present review highlights advances in material integration, surface modification, and signal enhancement techniques to mitigate the challenges of deploying capacitive sensors in biofluids (sweat, saliva, blood, serum). This work further expands on the promise of such sensors for advancing liquid biopsies and highlights key technical challenges in translating capacitive systems to clinics. Full article

Exosomes are nanoscale extracellular vesicles (EVs) that carry biomolecular signatures reflective of their parent cells, making them powerful tools for non-invasive diagnostics and therapeutic monitoring. Despite their potential, clinical application is hindered by challenges such as low abundance, heterogeneity, and the complexity of biological samples. To address these limitations, plasmonic biosensing technologies—particularly propagating surface plasmon resonance (PSPR), localized surface plasmon resonance (LSPR), and surface-enhanced Raman scattering (SERS)—have been developed to enable label-free, highly sensitive, and multiplexed detection at the single-vesicle level. This review outlines recent advancements in nanoplasmonic platforms for exosome detection and profiling, emphasizing innovations in nanostructure engineering, microfluidic integration, and signal enhancement. Representative applications in oncology, neurology, and immunology are discussed, along with the increasingly critical role of artificial intelligence (AI) in spectral interpretation and diagnostic classification. Key technical and translational challenges—such as assay standardization, substrate reproducibility, and clinical validation—are also addressed. Overall, this review highlights the synergy between exosome biology and plasmonic nanotechnology, offering a path toward real-time, precision diagnostics via sub-femtomolar detection of exosomal miRNAs through next-generation biosensing strategies. Full article

This paper reports on the high performance of a thick-waveguide guided mode resonance (GMR) sensor. Theoretical calculations revealed that when light incidents on the grating and excites the negative first-order diffraction order, by increasing the waveguide thickness, both a high sensitivity and high figure of merit (FOM) can be obtained. Experimentally, we achieved a sensitivity of 1255.78 nm/RIU, a resonance linewidth of 0.59 nm at the resonance wavelength of 535 nm, an FOM as high as 2128 RIU⁻¹, and a detection limit as low as 1.74 × 10⁻⁷ RIU. To our knowledge, this performance represents the highest comprehensive level for current GMR sensors. Additionally, the use of a microfluidic hemisphere and polymer materials effectively reduces the liquid consumption under oblique incidence and the fabrication cost in practical application. Overall, the proposed GMR sensor exhibits great potential in label-free biosensing. Full article

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression and have emerged as critical biomarkers in various diseases, including cancer. Their stability in bodily fluids and role as oncogenes or tumor suppressors make them attractive targets for non-invasive diagnostics. However, conventional detection methods, such as Northern blotting, RT-PCR, and microarrays, are limited by low sensitivity, lengthy protocols, and limited specificity. Electrochemical biosensors offer a promising alternative, providing high sensitivity, rapid response times, portability, and cost-effectiveness. These biosensors translate miRNA hybridization events into quantifiable electrochemical signals, often leveraging redox-active labels, mediators, or intercalators. Recent advancements in nanomaterials and signal amplification strategies have further enhanced detection capabilities, enabling sensitive, label-free miRNA quantification. This review provides a comprehensive overview of the recent advances in electrochemical biosensing of miRNAs, emphasizing innovative redox-based detection strategies, probe immobilization techniques, and hybridization modalities. The critical challenges and future perspectives in advancing electrochemical miRNA biosensors toward clinical translation and point-of-care diagnostics are discussed. Full article

Guided mode resonance (GMR) sensors are known for their ultrasensitive and label-free detection, achieved by assessing refractive index (RI) variations on grating surfaces. However, conventional systems often require manual adjustments, which limits their practical applicability. Therefore, this study enhances the practicality of GMR sensors by introducing an optimized detection system based on the Jones matrix method. In addition, finite element method simulations were performed to optimize the GMR sensor structure parameter. The GMR sensor chip consists of three main components: a cyclic olefin copolymer (COC) substrate with a one-dimensional grating structure of a period of ~295 nm, a height of ~100 nm, and a ~130 nm thick TiO₂ waveguide layer that enhances the light confinement; an integrated COC microfluidic module featuring a microchannel; and flexible tubes for efficient sample handling. A GMR sensor in conjunction with a specially designed system was used to perform RI measurements across varying concentrations of sucrose. The results demonstrate its exceptional performance, with a normalized sensitivity (S_n) and RI resolution (R_s) of 0.4 RIU⁻¹ and 8.15 × 10⁻⁵ RIU, respectively. The proposed detection system not only offers improved user-friendliness and cost efficiency but also delivers an enhanced performance, making it ideal for scientific and industrial applications, including biosensing and optical metrology, where precise polarization control is crucial. Full article

In this article, the role of downscaling in boosting the sensitivity of a novel label-free DNA sensor based on sub-10 nm dielectric-modulated transition metal dichalcogenide field-effect transistors (DM-TMD FET) is presented through a quantum simulation approach. The computational method is based on self-consistently solving the quantum transport equation coupled with electrostatics under ballistic transport conditions. The concept of dielectric modulation was employed as a label-free biosensing mechanism for detecting neutral DNA molecules. The computational investigation is exhaustive, encompassing the band profile, charge density, current spectrum, local density of states, drain current, threshold voltage behavior, sensitivity, and subthreshold swing. Four TMD materials were considered as the channel material, namely, MoS₂, MoSe₂, MoTe₂, and WS₂. The investigation of the scaling capability of the proposed label-free gate-all-around DM-TMDFET-based biosensor showed that gate downscaling is a valuable approach not only for producing small biosensors but also for obtaining high biosensing performance. Furthermore, we found that reducing the device size from 12 nm to 9 nm yields only a moderate improvement in sensitivity, whereas a more aggressive downscaling to 6 nm leads to a significant enhancement in sensitivity, primarily due to pronounced short-channel effects. The obtained results have significant technological implications, showing that miniaturization enhances the sensitivity of the proposed nanobiosensor. Full article

The creation of surface relief gratings using hydrogels for label-free biomolecule detection represents a significant advance in the development of versatile, cutting-edge biosensors. Central to this innovation is the formulation of materials with enhanced mechanical properties, especially for applications in soft, wearable technologies. In this work, we have developed novel biofunctional hydrogels that incorporate slide-ring supramolecular structures into their network, enabling the production of surface relief gratings with superior mechanical characteristics for biomolecule detection without the need for labels. These hydrogels, functionalized with bovine serum albumin and goat anti-rabbit antibodies, demonstrated excellent selectivity and sensitivity toward anti-bovine serum albumin and rabbit IgGs in blood serum, evaluated using a label-free format. Remarkably, the new materials matched the analytical performance of conventional hydrogels based on static networks while offering dramatically improved toughness and elasticity, with a compressive modulus comparable to human skin. This demonstrates the potential of slide-ring hydrogels for fabricating robust, label-free biosensing platforms. Furthermore, the flexibility of this system allows for the incorporation of various recognition elements tailored to specific applications. Full article

The rapid and ultrasensitive detection of Salmonella holds strategic significance for food safety surveillance and public health protection systems. This study innovatively developed a label-free biosensing platform based on the synergistic integration of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas12a and the fluorescent deoxyribozyme Aurora for the efficient detection of foodborne Salmonella. The detection mechanism operates through a molecular cascade reaction: target-activated Cas12a protein specifically degrades Aurora deoxyribozyme via its trans-cleavage activity, thereby abolishing the enzyme’s catalytic capability to convert 4-methylumbelliferyl phosphate (4-MUP) into the highly fluorescent product 4-methylumbelliferone (4-MU). This cascade ultimately enables quantitative target analysis through fluorescence signal attenuation. Following systematic optimization of critical reaction parameters, the biosensing system demonstrated exceptional analytical performance: a detection limit of 1.29 CFU/mL with excellent linearity (R² = 0.992) spanning six orders of magnitude (1.65 × 10¹–10⁶ CFU/mL), along with high specificity against multiple interfering bacterial strains. Spike-and-recovery tests in complex food matrices (milk, chicken, and lettuce) yielded recoveries of 90.91–99.40% (RSD = 3.55–4.72%), confirming robust practical applicability. Notably, the platform design allows flexible detection of other pathogens through simple replacement of CRISPR guide sequences. Full article

Integrated photonic biosensors are revolutionizing lab-on-a-chip technologies by providing highly sensitive, miniaturized, and label-free detection solutions for a wide range of biological and chemical targets. This review explores the foundational principles behind their operation, including the use of resonant photonic structures such as microring and whispering gallery mode resonators, as well as interferometric and photonic crystal-based designs. Special focus is given to the design strategies that optimize light–matter interaction, enhance sensitivity, and enable multiplexed detection. We detail state-of-the-art fabrication approaches compatible with complementary metal-oxide-semiconductor processes, including the use of silicon, silicon nitride, and hybrid material platforms, which facilitate scalable production and seamless integration with microfluidic systems. Recent advancements are highlighted, including the implementation of optofluidic photonic crystal cavities, cascaded microring arrays with subwavelength gratings, and on-chip detector arrays capable of parallel biosensing. These innovations have achieved exceptional performance, with detection limits reaching the parts-per-billion level and real-time operation across various applications such as clinical diagnostics, environmental surveillance, and food quality assessment. Although challenges persist in handling complex biological samples and achieving consistent large-scale fabrication, the emergence of novel materials, advanced nanofabrication methods, and artificial intelligence-driven data analysis is accelerating the development of next-generation photonic biosensing platforms. These technologies are poised to deliver powerful, accessible, and cost-effective diagnostic tools for practical deployment across diverse settings. Full article

In recent years, field-effect transistors (FETs) based on graphene have attracted significant interest due to their unique electrical properties and their potential for biosensing and molecular detection applications. This study uses FETs with a nanocrystalline graphite (NCG) channel to detect DNA nucleobases. The exceptional electronic properties of NCG, and its high surface area, enable strong π–π stacking interactions with DNA nucleobases, promoting efficient adsorption and stabilization of the biomolecules. The direct attachment of nucleobases to the NCG channel leads to substantial changes in the device’s electrical characteristics, which can be measured in real time to assess DNA binding and sequence recognition. This method enables highly sensitive, label-free DNA detection, opening up new possibilities for rapid genetic analysis and diagnostics. Understanding the interactions between DNA nucleobases and graphene-based materials is crucial for advancing genetic research and biotechnology, paving the way for more accurate and efficient diagnostic tools. Full article

Metasurfaces have been widely investigated across the disciplines of optical biosensing due to their exceptional ability to manipulate electromagnetic fields. Consequently, over the past few years, there has been growing interest in the application of metasurfaces in optical biosensors in the field of biomedical sensing. While being label-free and offering real-time tracking, high sensitivity, and a quick response are among the benefits of conventional optical biosensors, the incorporation of metasurfaces improves their wavefront manipulation, selectivity for versatile sensing, and capacity for device miniaturization to satisfy increasingly complex application requirements. Furthermore, there is a lack of comprehensive evaluations that address the current research developments and future possibilities, despite the encouraging advancements in this emerging field. Hence, this work provides a comprehensive review and serves as a valuable resource for researchers exploring metasurface-based optical biosensors. This review delves into defining the basic sensing concepts, design procedures, and important figures of merit (FOM) for metasurface-based optical biosensors and their applications, including the detection of numerous analytes, such as viruses, toxins, antibodies, tumors, and drugs and the monitoring of blood sugar. Furthermore, presenting a critical evaluation of structural fabrication techniques with a view toward potential future commercialization, this review ends by highlighting several fascinating areas for further investigation. For this review article, a total of 5844 effective documents about metasurface optical biosensors were retrieved from the Scopus database. The VOSviewer version 1.6.20 bibliometric software was used for the scientific analysis of the data retrieved from the Scopus database from 2010 to 2025. Full article

Efficient bacterial lysis and RNA purification are essential for molecular diagnostics and biosensing applications. This study presents a piezoelectric platform integrated with gold-plated RNA capture pins (RCPs) functionalized with synthetic oligonucleotides to extract and enrich E. coli 16S ribosomal RNA (rRNA). The 3D-printed device enables selective bacterial capture using E. coli-specific aptamers and incorporates a piezoelectric transducer operating at 60 kHz to facilitate bacterial cell wall disruption. The platform demonstrated high specificity for E. coli over B. cereus, confirming aptamer selectivity. E. coli viability assessment demonstrated that positioning the piezoelectric plate in contact with the bacterial suspension significantly improved the bacterial lysis, reducing viability to 33.68% after 15 min. RNA quantification confirmed an increase in total RNA released by lysed E. coli, resulting in 10,913 ng after 15 min, compared to 4310 ng obtained via conventional sonication. RCP-extracted RNA has a threefold enrichment of 16S rRNA relative to 23S rRNA. RT-qPCR analysis indicated that the RCPs recovered, on average, 2.3 ng of 16S RNA per RCP from bacterial suspensions and 0.1 ng from aptamer-functionalized surfaces. This integrated system offers a rapid, selective, and label-free approach for bacterial lysis, RNA extraction, and enrichment for specific types of RNA with potential applications in clinical diagnostics and microbial biosensing. Full article

Microfluidics has significantly advanced the field of single-cell analysis, particularly in studies related to cell growth, division, and heterogeneity. Electrical impedance spectroscopy (EIS), a label-free and non-invasive biosensing technique, has been integrated into microfluidic devices for high-throughput and long-term monitoring of single budding yeast cells. Accurate interpretation of EIS measurements of cell growth dynamics necessitates the establishment of theoretical equivalent circuit models for the single-cell sensing system. Here, we report on the development of equivalent circuit models of an in situ EIS sensing system to elucidate cell growth. Firstly, finite element modeling and simulation of an EIS measurement of cell growth in the EIS sensing unit were performed, guiding the fittings of electrical components for an established equivalent circuit model (ECM). From the ECM, we extracted an equivalent volume fraction applicable to various cell and sensing unit geometries to describe the geometry-dependent sensing characteristics corresponding to the electrical response in the model. Then, EIS measurements of an immobilized cell in a microfluidic device were conducted via peripheral circuits. A lumped parameter model for the entire EIS measurement system was established, with electrical components determined by fitting to experimental data. The rationality of the proposed theoretical model was validated through the long-term impedance variation induced by cell growth in experiments, demonstrating its feasibility in linking EIS data with the bio-physics underlying the experimental phenomenon. Full article

Photonic biosensors based on bound states in the continuum (BIC) resonant modes exhibit a transformative potential for high-sensitivity, label-free detection across various diagnostic applications. BIC-enabled metasurfaces, utilizing dielectric, plasmonic, and hybrid structures, achieve ultra-high Q-factors and amplify target molecule interactions on functionalized sensor surfaces. These unique properties result in increased refractive index sensitivity and low detection limits, essential for monitoring biomolecules in clinical diagnostics, environmental analysis, and food safety. Recent advancements in BIC-enabled metasurfaces have demonstrated ultra-low detection limits in the zeptomolar range, making these devices highly promising for real-world applications. This review paper critically discusses the design principles of BIC-based biosensors, emphasizing key factors such as material selection, structural asymmetry, and functionalization strategies that enhance both sensitivity and specificity. Additionally, recent advancements in fabrication techniques that enable precise BIC control with scalable approaches for practical biosensing applications are examined. Case studies demonstrate the effectiveness of BIC metasurfaces for real-time, low-concentration detection, highlighting their versatility and adaptability. Finally, the review discusses future challenges and opportunities, such as integration with microfluidics for point-of-care testing and multiplexed sensing, underscoring the potential of BIC-based platforms to revolutionize the field of biosensing. Full article

A novel approach to developing lateral flow assays (LFAs) for the detection of CYFRA 21-1 (cytokeratin 19 fragment, a molecular biomarker for epithelial-origin cancers) is proposed. Magnetic bioconjugates (MBCs) were employed in combination with advanced optical and magnetic tools to optimize assay conditions. The approach integrates such techniques as label-free spectral-phase interferometry, colorimetric detection, and ultrasensitive magnetometry using the magnetic particle quantification (MPQ) technique. For the first time in LFA applications, the MPQ-based and colorimetry-based detection methods were compared side by side, and superior analytical performance was demonstrated. The limit of detection (LOD) of 0.9 pg/mL was achieved using MPQ, and 2.9 pg/mL with optical detection. This study has demonstrated that MPQ provides elimination of signal saturation, higher sensitivity (slope of the calibration curve), and a 19-fold wider dynamic range of detected signals. Both optical and magnetic detection results are comparable to the best laboratory-based tests with the added benefits of a 20-min assay duration and the LFA format convenience. The assay effectiveness was validated in human serum and artificial saliva, and high recovery rates were observed. The proposed approach offers rapid and reliable detection of molecular biomarkers and holds significant potential for point-of-care diagnostics, particularly in resource-limited settings. Full article