Biosensors

18 pages, 2079 KiB

Open AccessArticle

An Amperometric Enzyme–Nanozyme Biosensor for Glucose Detection

by Asta Kausaite-Minkstimiene, Aiste Krikstaponyte, Nataliya Stasyuk, Galina Gayda and Almira Ramanaviciene

Biosensors 2025, 15(8), 545; https://doi.org/10.3390/bios15080545 - 19 Aug 2025

Abstract

Amperometric biosensors, due to their high sensitivity, fast response time, low cost, simple control, miniaturization capabilities, and other advantages, are receiving significant attention in the field of medical diagnostics, especially in monitoring blood glucose levels in diabetic patients. In this study, an amperometric [...] Read more.

Amperometric biosensors, due to their high sensitivity, fast response time, low cost, simple control, miniaturization capabilities, and other advantages, are receiving significant attention in the field of medical diagnostics, especially in monitoring blood glucose levels in diabetic patients. In this study, an amperometric glucose biosensor based on immobilized enzyme glucose oxidase (GOx) and bimetallic platinum cobalt (PtCo) nanoparticles was developed. The PtCo nanoparticles, deposited on a graphite rod electrode, exhibited peroxidase-like catalytic properties and were able to electrocatalyze the reduction of H₂O₂. After immobilization of the GOx, an amperometric signal generated by the biosensor was directly proportional to the glucose concentration in the range of 0.04–2.18 mM. The biosensor demonstrated a sensitivity of 19.38 μA mM⁻¹ cm⁻², with a detection limit of 0.021 mM and a quantification limit of 0.064 mM. In addition to this analytical performance, the biosensor exhibited excellent repeatability (relative standard deviation (RSD) was 4.90%); operational and storage stability, retaining 98.93% and 95.33% of its initial response after 26 cycles of glucose detection and over a 14-day period, respectively; and anti-interference ability against electroactive species, as well as exceptional selectivity for glucose and satisfactory reproducibility (RSD 8.90%). Additionally, the biosensor was able to detect glucose levels in blood serum with a high accuracy (RSD 5.89%), indicating potential suitability for glucose determination in real samples. Full article

(This article belongs to the Special Issue Recent Advances in Glucose Biosensors)

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17 pages, 1576 KiB

Open AccessArticle

Design of an MIP-Based Electrochemical Sensor for the Determination of Paracetamol in Pharmaceutical Samples

by José Alberto Cabas Rodríguez, Fernando Javier Arévalo and Adrian Marcelo Granero

Biosensors 2025, 15(8), 544; https://doi.org/10.3390/bios15080544 - 19 Aug 2025

Abstract

Paracetamol (PAR) is a common antipyretic and analgesic extensively used to treat cold and flu symptoms. It has been proven to be effective in headaches and relieving fever and pain. It is usually found as an over-the-counter drug, which has been associated with [...] Read more.

Paracetamol (PAR) is a common antipyretic and analgesic extensively used to treat cold and flu symptoms. It has been proven to be effective in headaches and relieving fever and pain. It is usually found as an over-the-counter drug, which has been associated with an increase in cases of poisoning due to overdose. Therefore, the development of new analytical tools for the detection of PAR at low concentrations in different samples is necessary. In this work, a Molecularly Imprinted Polymer (MIP)-based electrochemical sensor was designed for the selective and sensitive determination of PAR using a glassy carbon electrode (GCE) modified with a polymeric film obtained through the electropolymerization of o-aminophenol. A complete characterization based on electrochemical techniques, such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and scanning electron microscopy (SEM) was used to examine all steps involved in the construction of the MIP-based electrochemical sensor. In addition, all parameters affecting the MIP were optimized. As a result, the MIP-based electrochemical sensor showed a very low limit of detection (LOD) of 10 nM, with an analytical sensitivity of (3.4 ± 0.1) A M⁻¹. In addition, construction of the MIP-based electrochemical sensor showed highly reproducibility, expressed in terms of a variation coefficient lower than 4%. The MIP-based electrochemical sensor was successfully used in an assay for the determination of PAR in pharmaceutical products. The performance of the MIP-based electrochemical sensor was compared to High Performance Liquid Chromatography (HPLC) for the determination of PAR in pharmaceutical samples, showing excellent agreement between the two methodologies. A very important aspect of the developed sensor was its reusability for at least twenty times. The MIP-based electrochemical sensor is a reliable analytical tool for the determination of PAR. Full article

(This article belongs to the Special Issue Electrochemical Biosensor Applications in Agriculture, Environment and Health Systems)

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28 pages, 3851 KiB

Open AccessReview

Technological Advances and Medical Applications of Implantable Electronic Devices: From the Heart, Brain, and Skin to Gastrointestinal Organs

by Jonghyun Lee, Sung Yong Han and Young Woo Kwon

Biosensors 2025, 15(8), 543; https://doi.org/10.3390/bios15080543 - 18 Aug 2025

Abstract

Implantable electronic devices are driving innovation in modern medical technology and have significantly improved patients’ quality of life. This review comprehensively analyzes the latest technological trends in implantable electronic devices used in major organs, including the heart, brain, and skin. Additionally, it explores [...] Read more.

Implantable electronic devices are driving innovation in modern medical technology and have significantly improved patients’ quality of life. This review comprehensively analyzes the latest technological trends in implantable electronic devices used in major organs, including the heart, brain, and skin. Additionally, it explores the potential for application in the gastrointestinal system, particularly in the field of biliary stents, in which development has been limited. In the cardiac field, wireless pacemakers, subcutaneous implantable cardioverter-defibrillators, and cardiac resynchronization therapy devices have been commercialized, significantly improving survival rates and quality of life of patients with cardiovascular diseases. In the field of brain–neural interfaces, biocompatible flexible electrodes and closed-loop deep brain stimulation have improved treatments of neurological disorders, such as Parkinson’s disease and epilepsy. Skin-implantable devices have revolutionized glucose management in patients with diabetes by integrating continuous glucose monitoring and automated insulin delivery systems. Future development of implantable electronic devices incorporating pressure or pH sensors into biliary stents in the gastrointestinal system may significantly improve the prognosis of patients with bile duct cancer. This review systematically organizes the technological advances and clinical outcomes in each field and provides a comprehensive understanding of implantable electronic devices by suggesting future research directions. Full article

(This article belongs to the Section Biosensors and Healthcare)

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19 pages, 3233 KiB

Open AccessArticle

A Galactose-Functionalized Pyrrolopyrrole Aza-BODIPY for Highly Efficient Detection of Eight Aliphatic and Aromatic Biogenic Amines: Monitoring Food Freshness and Bioimaging

by Yujing Gan, Bingli Lu, Jintian Zhong, Xueguagn Ran, Derong Cao and Lingyun Wang

Biosensors 2025, 15(8), 542; https://doi.org/10.3390/bios15080542 - 18 Aug 2025

Abstract

The detection of aliphatic and aromatic biogenic amines (BAs) is important in food spoilage, environmental monitoring, and disease diagnosis and treatment. Existing fluorescent probes predominantly detect aliphatic BAs with single signal variation and low sensitivity, impairing the adaptability of discriminative sensing platforms. Herein, [...] Read more.

The detection of aliphatic and aromatic biogenic amines (BAs) is important in food spoilage, environmental monitoring, and disease diagnosis and treatment. Existing fluorescent probes predominantly detect aliphatic BAs with single signal variation and low sensitivity, impairing the adaptability of discriminative sensing platforms. Herein, we present a visual chemosensor (galactose-functionalized pyrrolopyrrole aza-BODIPY, PPAB-Gal) that simultaneously detects eight aliphatic and aromatic BAs in a real-time and intuitive way based on their unique electronic and structural features. Our findings reveal that the dual colorimetric and ratiometric emission changes are rapidly produced in presence of eight BAs through a noncovalent interaction (π–π stacking and hydrogen bond)-assisted chromophore reaction. Specifically, other lone-pair electrons containing compounds, such as secondary amines, tertiary amines, NH₃, and thiol, fail to exhibit these changes. As a result, superior sensing performances with distinctly dual signals (Δλ_ab = 130 nm, Δλ_em = 150 nm), a low LOD (~25 nM), and fast response time (<2 min) were obtained. Based on these advantages, a qualitative and smartphone-assisted sensing platform with a PPAB-Gal-loaded TLC plate is developed for visual detection of putrescine and cadaverine vapor. More importantly, we construct a connection between a standard quantitative index for the TVBN value and fluorescence signals to quantitatively determine the freshness of tuna and shrimp, and the method is facile and convenient for real-time and on-site detection in practical application. Furthermore, since the overexpressed spermine is an important biomarker of cancer diagnosis and treatment, PPAB-Gal NPs can be used to ratiometrically image spermine in living cells. This work provides a promising sensing method for BAs with a novel fluorescent material in food safety fields and biomedical assays. Full article

(This article belongs to the Special Issue Applications of Biosensors in Medicine, the Food Industry, and Disease Diagnosis)

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12 pages, 2134 KiB

Open AccessArticle

Fluorescence Imaging-Activated Microfluidic Particle Sorting Using Optical Tweezers

by Yiming Wang, Xinyue Dai, Qingtong Jiang, Hangtian Fan, Tong Li, Xiao Xia, Yipeng Dou and Yuxin Mao

Biosensors 2025, 15(8), 541; https://doi.org/10.3390/bios15080541 - 18 Aug 2025

Abstract

The precise and efficient sorting of microscopic particles is critical in diverse fields, including biomedical diagnostics, drug development, and environmental monitoring. Fluorescence imaging-activated sorting refers to a strategy where fluorescence images are used to dynamically identify target particles and trigger selective manipulation for [...] Read more.

The precise and efficient sorting of microscopic particles is critical in diverse fields, including biomedical diagnostics, drug development, and environmental monitoring. Fluorescence imaging-activated sorting refers to a strategy where fluorescence images are used to dynamically identify target particles and trigger selective manipulation for sorting purposes. In this study, we introduce a novel microfluidic particle sorting platform that combines optical tweezers with real-time fluorescence imaging for detection. High-speed image analysis enables accurate particle identification and classification, while the optical trap is selectively activated to redirect target particles. To validate the system’s performance, we used 10 µm green and orange fluorescent polystyrene particles. The platform achieved a sorting purity of 94.4% for orange particles under continuous flow conditions. The proposed platform provides an image-based sorting solution, advancing the development of microfluidic systems for high-resolution particle sorting in complex biological and environmental applications. Full article

(This article belongs to the Special Issue Microfluidics for Sample Pretreatment)

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27 pages, 5309 KiB

Open AccessReview

The Potential of Nanopore Technologies in Peptide and Protein Sensing for Biomarker Detection

by Iuliana Șoldănescu, Andrei Lobiuc, Olga Adriana Caliman-Sturdza, Mihai Covasa, Serghei Mangul and Mihai Dimian

Biosensors 2025, 15(8), 540; https://doi.org/10.3390/bios15080540 - 16 Aug 2025

Abstract

The increasing demand for high-throughput, real-time, and single-molecule protein analysis in precision medicine has propelled the development of novel sensing technologies. Among these, nanopore-based methods have garnered significant attention for their unique capabilities, including label-free detection, ultra-sensitivity, and the potential for miniaturization and [...] Read more.

The increasing demand for high-throughput, real-time, and single-molecule protein analysis in precision medicine has propelled the development of novel sensing technologies. Among these, nanopore-based methods have garnered significant attention for their unique capabilities, including label-free detection, ultra-sensitivity, and the potential for miniaturization and portability. Originally designed for nucleic acid sequencing, nanopore technology is now being adapted for peptide and protein analysis, offering promising applications in biomarker discovery and disease diagnostics. This review examines the latest advances in biological, solid-state, and hybrid nanopores for protein sensing, focusing on their ability to detect amino acid sequences, structural variants, post-translational modifications, and dynamic protein–protein or protein–drug interactions. We critically compare these systems to conventional proteomic techniques, such as mass spectrometry and immunoassays, discussing advantages and persistent technical challenges, including translocation control and signal deconvolution. Particular emphasis is placed on recent advances in protein sequencing using biological and solid-state nanopores and the integration of machine learning and signal-processing algorithms that enhance the resolution and accuracy of protein identification. Nanopore protein sensing represents a disruptive innovation in biosensing, with the potential to revolutionize clinical diagnostics, therapeutic monitoring, and personalized healthcare. Full article

(This article belongs to the Special Issue Advances in Nanopore Biosensors)

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22 pages, 4664 KiB

Open AccessArticle

Numerical Study of a Novel Kagome-Inspired Photonic Crystal Fiber-Based Surface Plasmon Resonance Biosensor for Detection of Blood Components and Analytical Targets

by Ayushman Ramola, Amit Kumar Shakya, Ali Droby and Arik Bergman

Biosensors 2025, 15(8), 539; https://doi.org/10.3390/bios15080539 - 15 Aug 2025

Abstract

This numerical study introduces a surface plasmon resonance (SPR)-based biosensor utilizing a kagome lattice-inspired hollow core photonic crystal fiber (PCF) for the highly sensitive detection of various blood biomarkers and analytical components. The sensor is designed to detect key blood biomarkers such as [...] Read more.

This numerical study introduces a surface plasmon resonance (SPR)-based biosensor utilizing a kagome lattice-inspired hollow core photonic crystal fiber (PCF) for the highly sensitive detection of various blood biomarkers and analytical components. The sensor is designed to detect key blood biomarkers such as water, glucose, plasma, and hemoglobin (Hb), as well as analytical targets including krypton, sylgard, ethanol, polyacrylamide (PA), and bovine serum albumin (BSA), by monitoring shifts in the resonance wavelength (RW). A dual-polarization approach is employed by analyzing both transverse magnetic (TM) and transverse electric (TE) modes. The proposed sensor demonstrates exceptional performance, achieving maximum wavelength sensitivities (Sw) of 18,900 nm RIU⁻¹ for TM pol. and 16,800 nm RIU⁻¹ for TE pol. Corresponding peak amplitude sensitivities (S_A) of 71,224 RIU⁻¹ for TM pol. and 58,112 RIU⁻¹ for TE pol. were also observed. The peak sensor resolution (S_R) for both modes is on the order of 10⁻⁶ RIU, underscoring its high precision. Owing to its enhanced sensitivity, compact design, and robust dual-polarization capability, the proposed biosensor holds strong promise for point-of-care diagnostics and real-time blood component analysis. Full article

(This article belongs to the Special Issue Surface Plasmon Resonance-Based Biosensors and Their Applications)

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15 pages, 2365 KiB

Open AccessArticle

Development of a Novel Aptamer-Antibody Sandwich Chemiluminescent Biosensor and Its Application in the Detection of Aflatoxin B₁

by Zhike Zhao, Jianghao Feng and Caizhang Wu

Biosensors 2025, 15(8), 538; https://doi.org/10.3390/bios15080538 - 15 Aug 2025

Abstract

In addressing the challenges posed by high costs, low accuracy, and cumbersome operations in mycotoxin detection, a novel aptamer-antibody sandwich chemiluminescent biosensor for detecting aflatoxin B₁ (AFB₁) was developed. The indirect competition between AFB₁, aflatoxin B₁-ovomucoid [...] Read more.

In addressing the challenges posed by high costs, low accuracy, and cumbersome operations in mycotoxin detection, a novel aptamer-antibody sandwich chemiluminescent biosensor for detecting aflatoxin B₁ (AFB₁) was developed. The indirect competition between AFB₁, aflatoxin B₁-ovomucoid complete antigen (AFB₁-OVA), and rabbit anti-ovomucoid (OVA) antibody results in the formation of a sandwich complex. This sandwich assay is linked to a horseradish peroxidase-labeled antibody, which catalyzes luminol chemiluminescence for the indirect detection of AFB₁. The biosensor was designed to operate with high precision, low cost, and a low detection limit for AFB₁, which is contingent upon experimental conditions such as pH, reagent concentration, temperature, and incubation time. The optimization of pH, aptamer concentration, competitive incubation time, competitive incubation temperature, and HRP-labeled antibody concentration was instrumental in achieving these objectives. Experimental findings demonstrated that the sensor’s detection limit was 0.067 ng/mL, exhibiting excellent linearity (R² = 0.99679) within the concentration range of 0.25–10 ng/mL. The recovery rate of spiked samples ranged from 94.4% to 108.05%. This sensor boasts a low detection limit, straightforward operation, and minimal cost, thus offering a novel solution for developing cost-effective, high-precision mycotoxin detection methods. Full article

(This article belongs to the Section Optical and Photonic Biosensors)

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16 pages, 2774 KiB

Open AccessArticle

Enzyme-Free Monitoring of Glucose Using Molecularly Imprinted Polymers and Gold Nanoparticles

by Ana Rita Aires Cardoso, Pedro Miguel Cândido Barquinha and Maria Goreti Ferreira Sales

Biosensors 2025, 15(8), 537; https://doi.org/10.3390/bios15080537 - 15 Aug 2025

Abstract

This work describes a non-enzymatic electrochemical glucose biosensor combining for the first time molecularly imprinted polymers (MIPs) for glucose concentration and gold nanoparticles (AuNPs) on screen-printed carbon electrodes (SPEs), where both MIPs and AuNPs were assembled in situ. Electrochemical impedance spectroscopy (EIS) was [...] Read more.

This work describes a non-enzymatic electrochemical glucose biosensor combining for the first time molecularly imprinted polymers (MIPs) for glucose concentration and gold nanoparticles (AuNPs) on screen-printed carbon electrodes (SPEs), where both MIPs and AuNPs were assembled in situ. Electrochemical impedance spectroscopy (EIS) was used to evaluate the analytical performance of the sensor, which has a linear range between 1.0 µM and 1.0 mM when standard solutions are prepared in buffer. Direct measurement of glucose was performed by chronoamperometry, measuring the oxidation current generated during direct glucose oxidation. The selectivity was tested against ascorbic acid and the results confirmed a selective discrimination of the electrode for glucose. Overall, the work presented here represents a promising tool for tracking glucose levels in serum. The use of glucose MIP on the electrode surface allows the concentration of glucose, resulting in lower detection limits, and the use of AuNPs reduces the potential required for the oxidation of glucose, which increases selectivity. In addition, this possible combination of two analytical measurements following different theoretical concepts can contribute to the accuracy of the analytical measurements. This combination can also be extended to other biomolecules that can be electrochemically oxidised at lower potentials. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers in Biosensors: Assembly, Characterization and Applications)

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13 pages, 7712 KiB

Open AccessArticle

Bifunctional TiO₂@AgNP Superstructures as a SERS-Sensing Platform for Identifying Flavonoids in Chinese Herbal Medicine

by Yulin Li, Jubo Li, Haisu Wang, Shaorui Qi, Zhehao Zhang, Yaqiu Wang, Ying Wang and Wei Ji

Biosensors 2025, 15(8), 536; https://doi.org/10.3390/bios15080536 - 15 Aug 2025

Abstract

Acanthopanax senticosus is an essential medicinal herb in traditional Chinese medicine, with its pharmacological properties largely attributed to bioactive flavonoids. The types and amounts of these flavonoids act as vital quality markers for both the raw materials and the resultant products. In this [...] Read more.

Acanthopanax senticosus is an essential medicinal herb in traditional Chinese medicine, with its pharmacological properties largely attributed to bioactive flavonoids. The types and amounts of these flavonoids act as vital quality markers for both the raw materials and the resultant products. In this work, we introduce a TiO₂@AgNP nanocomposite designed as a surface-enhanced Raman scattering (SERS) sensor aimed at the preliminary quantification and identification of flavonoids. This is achieved by leveraging the effective molecular adsorption properties of TiO₂ alongside the ‘hot spots’ generated by AgNPs. By optimizing SERS performance through adjustment of the molar ratio between TiO₂ and Ag, we can quantitatively evaluate four flavonoids—luteolin, kaempferol, quercetin, and rutin—with low detection concentrations of 10⁻⁶ M, 10⁻⁵ M, 5 × 10⁻⁶ M, and 10⁻⁶ M, respectively. Additionally, we observe a nearly linear relationship between the SERS signals and the flavonoid concentrations, allowing for dual or multiplex analysis of these compounds. Furthermore, we successfully differentiated Acanthopanax senticosus samples from six different geographical regions in China based on the detection of significant flavonoid constituents. This serves as a proof of concept for practical applications that can enhance the identification and distinction of traditional Chinese medicine, as well as assess quality and medicinal efficacy. Full article

(This article belongs to the Special Issue Surface-Enhanced Raman Scattering in Biosensing Applications)

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24 pages, 3609 KiB

Open AccessReview

Droplet-Based Microfluidics in Single-Bacterium Analysis: Advancements in Cultivation, Detection, and Application

by Haiyan Ma, Yuewen Zhang, Ren Shen and Yanwei Jia

Biosensors 2025, 15(8), 535; https://doi.org/10.3390/bios15080535 - 15 Aug 2025

Abstract

Microorganisms exhibit remarkable diversity, making their comprehensive characterization essential for understanding ecosystem functioning and safeguarding human health. However, traditional culture-based methods entail inherent limitations for resolving microbial heterogeneity, isolating slow-growing microorganisms, and accessing uncultivated microbes. Conversely, droplet-based microfluidics enables a high-throughput and precise [...] Read more.

Microorganisms exhibit remarkable diversity, making their comprehensive characterization essential for understanding ecosystem functioning and safeguarding human health. However, traditional culture-based methods entail inherent limitations for resolving microbial heterogeneity, isolating slow-growing microorganisms, and accessing uncultivated microbes. Conversely, droplet-based microfluidics enables a high-throughput and precise platform for single-bacterium manipulation by physically isolating individual cells within microdroplets. This technology presents a transformative approach to overcoming the constraints of conventional techniques. This review outlines the fundamental principles, recent research advances, and key application domains of droplet-based microfluidics, with a particular focus on innovations in single-bacterium encapsulation, sorting, cultivation, and functional analysis. Applications such as antibiotic susceptibility testing, enzyme-directed evolution screening, microbial interaction studies, and the cultivation of novel bacterial species are discussed, underscoring the technology’s broad potential in microbiological research and biotechnology. Full article

(This article belongs to the Special Issue Biosensors Based on Microfluidic Devices—2nd Edition)

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16 pages, 1307 KiB

Open AccessArticle

Kinetic Analysis of SARS-CoV-2 S1–Integrin Binding Using Live-Cell, Label-Free Optical Biosensing

by Nicolett Kanyo, Krisztina Borbely, Beatrix Peter, Kinga Dora Kovacs, Anna Balogh, Beatrix Magyaródi, Sandor Kurunczi, Inna Szekacs and Robert Horvath

Biosensors 2025, 15(8), 534; https://doi.org/10.3390/bios15080534 - 14 Aug 2025

Abstract

The SARS-CoV-2 spike (S1) protein facilitates viral entry through binding to angiotensin-converting enzyme 2 (ACE2), but it also contains an Arg–Gly–Asp (RGD) motif that may enable interactions with RGD-binding integrins on ACE2-negative cells. Here, we provide quantitative evidence for this alternative binding pathway [...] Read more.

The SARS-CoV-2 spike (S1) protein facilitates viral entry through binding to angiotensin-converting enzyme 2 (ACE2), but it also contains an Arg–Gly–Asp (RGD) motif that may enable interactions with RGD-binding integrins on ACE2-negative cells. Here, we provide quantitative evidence for this alternative binding pathway using a live-cell, label-free resonant waveguide grating (RWG) biosensor. RWG technology allowed us to monitor real-time adhesion kinetics of live cells to RGD-displaying substrates, as well as cell adhesion to S1-coated surfaces. To characterize the strength of the integrin–S1 interaction, we determined the dissociation constant using two complementary approaches. First, we performed a live-cell competitive binding assay on RGD-displaying surfaces, where varying concentrations of soluble S1 were added to cell suspensions. Second, we recorded the adhesion kinetics of cells on S1-coated surfaces and fitted the data using a kinetic model based on coupled ordinary differential equations. By comparing the results from both methods, we estimate that approximately 33% of the S1 molecules immobilized on the Nb₂O₅ biosensor surface are capable of initiating integrin-mediated adhesion. These findings support the existence of an alternative integrin-dependent entry route for SARS-CoV-2 and highlight the effectiveness of label-free RWG biosensing for quantitatively probing virus–host interactions under physiologically relevant conditions without the need of the isolation of the interaction partners from the cells. Full article

(This article belongs to the Special Issue In Honor of Prof. Evgeny Katz: Biosensors: Science and Technology)

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15 pages, 1615 KiB

Open AccessArticle

Simultaneous Routing with Washing Droplets Based on Shape-Dependent Velocity Model in MEDA Biochips

by Chiharu Shiro, Hiroki Nishikawa, Xiangbo Kong, Hiroyuki Tomiyama and Shigeru Yamashita

Biosensors 2025, 15(8), 533; https://doi.org/10.3390/bios15080533 - 14 Aug 2025

Abstract

Micro Electrode Dot Array (MEDA) biochips have recently attracted considerable attention in the biochemical and medical industries. MEDA biochips manipulate micro droplets for biochemical experiments such as DNA analysis. Droplets on MEDA biochips are moved using the Electrowetting on Dielectric (EWOD) effect, but [...] Read more.

Micro Electrode Dot Array (MEDA) biochips have recently attracted considerable attention in the biochemical and medical industries. MEDA biochips manipulate micro droplets for biochemical experiments such as DNA analysis. Droplets on MEDA biochips are moved using the Electrowetting on Dielectric (EWOD) effect, but a portion of a droplet may remain on a cell after passing through, contaminating the cell. Other droplets cannot pass through a contaminated cell. In previous studies, contaminated cells were considered unavailable for droplet routing. As the number of contaminated cells increases, droplets may be prevented from moving to the desired position. Therefore, we propose a method for simultaneous routing of target functional and washing droplets based on a shape-dependent velocity model. In a simulation, the proposed method reduced the routing time by about 10% compared with an existing method. Full article

(This article belongs to the Special Issue Microfluidics for Biomedical Applications (3rd Edition))

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16 pages, 6084 KiB

Open AccessArticle

First Design of a Contact Lens for Diagnosis of Dehydration

by Kundan Sivashanmugan, Reece E. Albert and Joseph R. Lakowicz

Biosensors 2025, 15(8), 532; https://doi.org/10.3390/bios15080532 - 14 Aug 2025

Abstract

Dehydration is a serious medical problem for elderly patients and young children. The most widely used diagnostics are measurements of sodium ion (Na⁺) and potassium ion (K⁺) in blood serum. Dehydration is difficult to diagnose even by trained health [...] Read more.

Dehydration is a serious medical problem for elderly patients and young children. The most widely used diagnostics are measurements of sodium ion (Na⁺) and potassium ion (K⁺) in blood serum. Dehydration is difficult to diagnose even by trained health care professionals because the body compensates to maintain the appearance of skin. These measurements required a blood draw because specific tests are generally not available for only Na⁺ and K⁺. The blood samples are analyzed by an electrolyte panel (EP) or a basic metabolic panel (BMP). Most hospitals limit EP and BMP to one per day to control costs. More frequent measurements of Na⁺ and K⁺ are needed, especially during rehydration. We designed a dehydration contact lens that can provide the Na⁺ and K⁺ concentrations as needed or for continuous monitoring. The measurements are obtained from the fluorescent lifetime or wavelength-ratiometric intensities of the Na⁺- and K⁺-sensitive fluorophores. The dehydration contact lens does not contain electronic components and are inexpensive to prepare. Full article

(This article belongs to the Special Issue Advanced Fluorescence Biosensors)

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15 pages, 3400 KiB

Open AccessArticle

Ti₃C₂T_X MXene/Polyaniline-Modified Nylon Fabric Electrode for Wearable Non-Invasive Glucose Monitoring in Sweat

by Lichao Wang, Meng Li, Shengnan Ya, Hang Tian, Kerui Li, Qinghong Zhang, Yaogang Li, Hongzhi Wang and Chengyi Hou

Biosensors 2025, 15(8), 531; https://doi.org/10.3390/bios15080531 - 14 Aug 2025

Abstract

Sweat-based electrochemical sensors for wearable applications have attracted substantial interest due to their non-invasive nature, compact design, and ability to provide real-time data. Remarkable advancements have been made in integrating these devices into flexible platforms. While thin-film polymer substrates are frequently employed for [...] Read more.

Sweat-based electrochemical sensors for wearable applications have attracted substantial interest due to their non-invasive nature, compact design, and ability to provide real-time data. Remarkable advancements have been made in integrating these devices into flexible platforms. While thin-film polymer substrates are frequently employed for their durability, the prolonged buildup of sweat on such materials can disrupt consistent sensing performance and adversely affect skin comfort over extended periods. Therefore, investigating lightweight, comfortable, and breathable base materials for constructing working electrodes is essential for producing flexible and breathable sweat electrochemical sensors. In this study, nylon fabric was chosen as the base material for constructing the working electrode. The electrode is prepared using a straightforward printing process, incorporating Ti₃C₂T_X MXene/polyaniline and methylene blue as modification materials in the electronic intermediary layer. The synergistic effect of the modified layer and the multi-level structure of the current collector enhances the electrochemical kinetics on the electrode surface, improves electron transmission efficiency, and enables the nylon fabric-based electrode to accurately and selectively measure glucose concentration in sweat. It exhibits a wide linear range (0.04~3.08 mM), high sensitivity (3.11 μA·mM⁻¹), strong anti-interference capabilities, and high stability. This system can monitor glucose levels and trends in sweat, facilitating the assessment of daily sugar intake for personal health management. Full article

(This article belongs to the Section Biosensor and Bioelectronic Devices)

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11 pages, 1327 KiB

Open AccessArticle

All-in-One Sustainable Thread Biosensor for Chemiluminescence Smartphone Detection of Lactate in Sweat

by Emanuela Maiorano, Maria Maddalena Calabretta, Eugenio Lunedei and Elisa Michelini

Biosensors 2025, 15(8), 530; https://doi.org/10.3390/bios15080530 - 13 Aug 2025

Abstract

Thanks to their low-cost, portability, and sustainability, microfluidic thread-based analytical devices (μTADs) are emerging as an attractive analytical platform for wearable biosensing. While several μTADs, mainly based on colorimetric and electrochemical detection methods, have been developed, achieving the needed sensitivity and accuracy for [...] Read more.

Thanks to their low-cost, portability, and sustainability, microfluidic thread-based analytical devices (μTADs) are emerging as an attractive analytical platform for wearable biosensing. While several μTADs, mainly based on colorimetric and electrochemical detection methods, have been developed, achieving the needed sensitivity and accuracy for these biosensors continues to present a significant challenge. Prompted by this need we investigated for the first time the implementation of chemiluminescence (CL) as a detection technique for μTADs. Exploiting the lactate oxidase-catalyzed reaction coupled with the enhanced luminol/H₂O₂/horseradish peroxidase CL system, we developed a cotton-thread-based chemiluminescent device enabling the detection of lactate with a limit of detection of 0.25 mM in a 2 µL volume of artificial sweat at pH 6.5 within 3 min. The use of recycled grape skin as support made the device sustainable, while the smartphone detection allowed a simple and quantitative readout for the end-user. Using a smartphone as a detector, the analytical performance was evaluated in different conditions and in the presence of potential interferents, showing suitability for monitoring lactate levels in physiological conditions, such as for monitoring anaerobic thresholds in endurance training. Full article

(This article belongs to the Special Issue Advanced Biosensing and Bioimaging by Nanomaterials and Machine Learning)

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13 pages, 2094 KiB

Open AccessArticle

Laser-Assisted Visible-Light Polymerization for Rapid Synthesis of Molecularly Imprinted Polymers

by Wissal Mrabet, Abdelhafid Karrat and Aziz Amine

Biosensors 2025, 15(8), 529; https://doi.org/10.3390/bios15080529 - 13 Aug 2025

Abstract

The demand for rapid, energy-efficient, and low-toxicity methods for synthesizing molecularly imprinted polymers (MIPs) is increasing, particularly for applications in environmental monitoring and green chemistry. In this context, the present work focuses on the development of a novel laser-assisted method for MIP synthesis, [...] Read more.

The demand for rapid, energy-efficient, and low-toxicity methods for synthesizing molecularly imprinted polymers (MIPs) is increasing, particularly for applications in environmental monitoring and green chemistry. In this context, the present work focuses on the development of a novel laser-assisted method for MIP synthesis, employing a visible laser (450 nm) and erythrosine B as a green photoinitiator. This visible-light approach enables fast and spatially controlled polymerization while avoiding the drawbacks of conventional methods (thermal heating, UV synthesis), such as the use of toxic initiators like AIBN and the need for UV shielding. MIPs were synthesized for bisphenol A and sulfamethoxazole, two emerging contaminants of significant environmental concern. The synthesis process was optimized for rapidity and scalability, and the resulting MIPs were integrated into a paper-based analytical device (MIP-PAD) for smartphone-assisted, on-site detection. The developed sensors exhibited excellent analytical performance, with recovery rates of 98.6% in tap water and 90.2% in river water and relative standard deviations (RSDs) below 1.88%. This study demonstrated a green, efficient, and highly controllable laser-assisted polymerization technique, offering a promising alternative to conventional MIP synthesis methods. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers in Biosensors: Assembly, Characterization and Applications)

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12 pages, 2021 KiB

Open AccessArticle

Dual-Mode Optical Detection of Sulfide Ions Using Copper-Anchored Nitrogen-Doped Graphene Quantum Dot Nanozymes

by Van Anh Ngoc Nguyen, Trung Hieu Vu, Phuong Thy Nguyen and Moon Il Kim

Biosensors 2025, 15(8), 528; https://doi.org/10.3390/bios15080528 - 13 Aug 2025

Abstract

We present a dual-mode optical sensing strategy for selective and sensitive detection of sulfide ions (S²⁻), employing copper-anchored nitrogen-doped graphene quantum dots (Cu@N-GQDs) as bifunctional nanozymes. The Cu@N-GQDs were synthesized via citric acid pyrolysis in the presence of ammonium hydroxide (serving [...] Read more.

We present a dual-mode optical sensing strategy for selective and sensitive detection of sulfide ions (S²⁻), employing copper-anchored nitrogen-doped graphene quantum dots (Cu@N-GQDs) as bifunctional nanozymes. The Cu@N-GQDs were synthesized via citric acid pyrolysis in the presence of ammonium hydroxide (serving as both nitrogen source and reductant) and copper chloride, leading to uniform incorporation of copper oxide species onto the N-GQD surface. The resulting nanohybrids exhibit two synergistic functionalities: intrinsic fluorescence comparable to pristine N-GQDs, and significantly enhanced peroxidase-like catalytic activity attributed to the anchored copper species. Upon interaction with sulfide ions, the system undergoes a dual-optical response: (i) fluorescence quenching via Cu-S complexation, and (ii) inhibition of peroxidase-like activity due to the deactivation of Cu catalytic centers via the interaction with S²⁻. This dual-signal strategy enables sensitive quantification of S²⁻, achieving detection limits of 0.5 µM (fluorescence) and 3.5 µM (colorimetry). The sensor demonstrates excellent selectivity over competing substances and high reliability and precision in real tap water samples. These findings highlight the potential of Cu@N-GQDs as robust, bifunctional, and field-deployable nanozyme probes for environmental and biomedical sulfide ion monitoring. Full article

(This article belongs to the Special Issue Advanced Optics and Photonics in Biosensing Applications)

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15 pages, 2864 KiB

Open AccessArticle

Rapid Detection of Staphylococcus aureus in Milk Samples by DNA Nanodendrimer-Based Fluorescent Biosensor

by Mukaddas Mijit, Dongxia Pan, Hui Wang, Chaoqun Sun and Liang Yang

Biosensors 2025, 15(8), 527; https://doi.org/10.3390/bios15080527 - 12 Aug 2025

Abstract

Staphylococcus aureus is the primary pathogen responsible for mastitis in dairy cows and foodborne illnesses, posing a significant threat to public health and food safety. Here, we developed an enhanced sensor based on solid-phase separation using gold-magnetic nanoparticles (Au@Fe₃O₄) [...] Read more.

Staphylococcus aureus is the primary pathogen responsible for mastitis in dairy cows and foodborne illnesses, posing a significant threat to public health and food safety. Here, we developed an enhanced sensor based on solid-phase separation using gold-magnetic nanoparticles (Au@Fe₃O₄) and signal amplification via dendritic DNA nanostructures. The substrate chain was specifically immobilized using thiol–gold coordination, and a three-dimensional dendritic structure was constructed through sequential hybridization of DNAzymes, L chains, and Y chains, resulting in a 2.8-fold increase in initial fluorescence intensity. Upon specific cleavage of the substrate chain at the rA site by S. aureus DNA, the complex dissociates, resulting in fluorescence intensity decay. The fluorescence intensity is negatively correlated with the concentration of Staphylococcus aureus. After optimization, the biosensor maintains a detection limit of 1 CFU/mL within 3 min, with a linear range extended to 1–10⁷ CFU/mL (R² = 0.998) and recovery rates of 85.6–102.1%, significantly enhancing resistance to matrix interference. This provides an innovative solution for rapid on-site detection of foodborne pathogens. Full article

(This article belongs to the Special Issue The Application of Biomaterials in Electronics and Biosensors)

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