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One-Pot Colorimetric Nucleic Acid Test Mediated by Silver Nanoparticles for DNA Extraction and Detection
Rapid and Highly Sensitive Detection of Ricin in Biological Fluids Using Optical Modulation Biosensing
Understanding the Mechanism of Bent DNA Amplifying Sensors Using All-Atom Molecular Dynamics Simulations

Journal Description

Biosensors

Biosensors is an international, peer-reviewed, open access journal on the technology and science of biosensors published monthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), PubMed, MEDLINE, PMC, Embase, CAPlus / SciFinder, Inspec, and other databases.
Journal Rank: JCR - Q1 (Instruments and Instrumentation) / CiteScore - Q1 (Instrumentation)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 21.8 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 5.6 (2024); 5-Year Impact Factor: 5.7 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2079-6374

Latest Articles

15 pages, 1609 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 (registering DOI) - 14 Aug 2025

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))

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 (registering DOI) - 14 Aug 2025

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 (registering DOI) - 14 Aug 2025

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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12 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

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

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

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

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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18 pages, 2250 KiB

Open AccessArticle

Fumonisin B Determination in Maize Products from Belize Using an Immunosensor Based on Screen-Printed Carbon Electrodes

by Beatriz Pérez-Fernández, Britt Marianna Maestroni, Carlotta Cozzani, Colette Eusey, Natalie Gibson, Alfredo de la Escosura-Muñiz and Christina Vlachou

Biosensors 2025, 15(8), 526; https://doi.org/10.3390/bios15080526 - 12 Aug 2025

A competitive electrochemical immunosensor, using screen-printed carbon electrodes (SPCEs), was developed for the determination of total fumonisins (sum of FB1, FB2 and FB3) extracted with a simple solvent extraction and dilution method, without clean up, from maize flour and maize tortillas. The optimized [...] Read more.

A competitive electrochemical immunosensor, using screen-printed carbon electrodes (SPCEs), was developed for the determination of total fumonisins (sum of FB1, FB2 and FB3) extracted with a simple solvent extraction and dilution method, without clean up, from maize flour and maize tortillas. The optimized biosensor has a linear range of 0.25 to 50 µg/L with 3% and 2% reproducibility for FB1 and (FB1 + FB2), respectively, and a linear range of 0.25 to 10 µg/L with 2% reproducibility for (FB1 + FB2 + FB3). The limits of detection and quantification in PBS buffer for total fumonisins are 0.12 µg/L and 0.39 µg/L, respectively. These values in the maize matrix are 6.07 µg/kg and 20.25 µg/kg, respectively. In addition, the stability and the selectivity of the sensor were studied. The immunosensor was validated with liquid chromatography–tandem mass spectrometry. This novel biosensor is more rapid, simpler and cheaper than current methods, and can also be used at the point of need. Full article

(This article belongs to the Special Issue Applications of Cutting-Edge Biosensors in Environment, Food and Healthcare Field)

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24 pages, 2773 KiB

Open AccessArticle

Highly Sensitive SOI-TFET Gas Sensor Utilizing Tailored Conducting Polymers for Selective Molecular Detection and Microbial Biosensing Integration

by Mohammad K. Anvarifard and Zeinab Ramezani

Biosensors 2025, 15(8), 525; https://doi.org/10.3390/bios15080525 - 11 Aug 2025

We present a highly sensitive and selective gas sensor based on an advanced silicon-on-insulator tunnel field-effect transistor (SOI-TFET) architecture, enhanced through the integration of customized conducting polymers. In this design, traditional metal gates are replaced with distinct functional polymers—PPP-TOS/AcCN, PP-TOS/AcCN, PP-FE(CN)₆³⁻ [...] Read more.

We present a highly sensitive and selective gas sensor based on an advanced silicon-on-insulator tunnel field-effect transistor (SOI-TFET) architecture, enhanced through the integration of customized conducting polymers. In this design, traditional metal gates are replaced with distinct functional polymers—PPP-TOS/AcCN, PP-TOS/AcCN, PP-FE(CN)₆³⁻/H₂O, PPP-TCNQ-TOS/AcCN, and PPP-ClO₄/AcCN—which enable precise molecular recognition and discrimination of various target gases. To further enhance sensitivity, the device employs an oppositely doped source region, significantly improving gate control and promoting stronger band-to-band tunneling. This structural modification amplifies sensing signals and improves noise immunity, allowing reliable detection at trace concentrations. Additionally, optimization of the subthreshold swing contributes to faster switching and response times. Thermal stability is addressed by embedding a P-type buffer layer within the buried oxide, which increases thermal conductivity and reduces lattice temperature, further stabilizing device performance. Experimental results demonstrate that the proposed sensor outperforms conventional SOI-TFET designs, exhibiting superior sensitivity and selectivity toward analytes such as methanol, chloroform, isopropanol, and hexane. Beyond gas sensing, the unique polymer-functionalized gate design enables integration of microbial biosensing capabilities, making the platform highly versatile for biochemical detection. This work offers a promising pathway toward ultra-sensitive, low-power sensing technologies for environmental monitoring, industrial safety, and medical diagnostics. Full article

(This article belongs to the Special Issue Microbial Biosensor: From Design to Applications—2nd Edition)

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40 pages, 14675 KiB

Open AccessReview

Recent Advances in Hydrogel-Promoted Photoelectrochemical Sensors

by Yali Cui, Yanyuan Zhang, Lin Wang and Yuanqiang Hao

Biosensors 2025, 15(8), 524; https://doi.org/10.3390/bios15080524 - 10 Aug 2025

Photoelectrochemical (PEC) sensors have garnered increasing attention due to their high sensitivity, low background signal, and rapid response. The incorporation of hydrogels into PEC platforms has significantly expanded their analytical capabilities by introducing features such as biocompatibility, tunable porosity, antifouling behavior, and mechanical [...] Read more.

Photoelectrochemical (PEC) sensors have garnered increasing attention due to their high sensitivity, low background signal, and rapid response. The incorporation of hydrogels into PEC platforms has significantly expanded their analytical capabilities by introducing features such as biocompatibility, tunable porosity, antifouling behavior, and mechanical flexibility. This review systematically categorizes hydrogel materials into four main types—nucleic acid-based, synthetic polymer, natural polymer, and carbon-based—and summarizes their functional roles in PEC sensors, including structural support, responsive amplification, antifouling interface construction, flexible electrolyte integration, and visual signal output. Representative applications are highlighted, ranging from the detection of ions, small biomolecules, and biomacromolecules to environmental pollutants, photodetectors, and flexible bioelectronic devices. Finally, key challenges—such as improving fabrication scalability, enhancing operational stability, integrating emerging photoactive materials, and advancing bio-inspired system design—are discussed to guide the future development of hydrogel-enhanced PEC sensing technologies. Full article

(This article belongs to the Special Issue Biosensors Based on Self-Assembly and Boronate Affinity Interaction)

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19 pages, 2087 KiB

Open AccessArticle

Kinematic Monitoring of the Thorax During the Respiratory Cycle Using a Biopolymer-Based Strain Sensor: A Chitosan–Glycerol–Graphite Composite

by María Claudia Rivas Ebner, Emmanuel Ackah, Seong-Wan Kim, Young-Seek Seok and Seung Ho Choi

Biosensors 2025, 15(8), 523; https://doi.org/10.3390/bios15080523 - 9 Aug 2025

This study presents the development and the mechanical and clinical characterization of a flexible biodegradable chitosan–glycerol–graphite composite strain sensor for real-time respiratory monitoring, where the main material, chitosan, is derived and extracted from Tenebrio Molitor larvae shells. Chitosan was extracted using a sustainable, [...] Read more.

This study presents the development and the mechanical and clinical characterization of a flexible biodegradable chitosan–glycerol–graphite composite strain sensor for real-time respiratory monitoring, where the main material, chitosan, is derived and extracted from Tenebrio Molitor larvae shells. Chitosan was extracted using a sustainable, low-impact protocol and processed into a stretchable and flexible film through glycerol plasticization and graphite integration, forming a conductive biocomposite. The sensor, fabricated in a straight-line geometry to ensure uniform strain distribution and signal stability, was evaluated for its mechanical and electrical performance under cyclic loading. Results demonstrate linearity, repeatability, and responsiveness to strain variations in the stain sensor during mechanical characterization and performance, ranging from 1 to 15%, with minimal hysteresis and fast recovery times. The device reliably captured respiratory cycles during normal breathing across three different areas of measurement: the sternum, lower ribs, and diaphragm. The strain sensor also identified distinct breathing patterns, including eupnea, tachypnea, bradypnea, apnea, and Kussmaul respiration, showing the capability to sense respiratory cycles during pathological situations. Compared to conventional monitoring systems, the sensor offers superior skin conformity, better adhesion, comfort, and improved signal quality without the need for invasive procedures or complex instrumentation. Its low-cost, biocompatible design holds strong potential for wearable healthcare applications, particularly in continuous respiratory tracking, sleep disorder diagnostics, and home-based patient monitoring. Future work will focus on wireless integration, environmental durability, and clinical validation. Full article

(This article belongs to the Special Issue Multidimensional Nanomaterial-Based Biosensors for Environmental and Healthcare Monitoring)

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13 pages, 5735 KiB

Open AccessArticle

High-Resolution Imaging of Morphological Changes Associated with Apoptosis and Necrosis Using Single-Cell Full-Field Optical Coherence Tomography

by Suyeon Kang, Kyeong Ryeol Kim, Minju Cho, Joonseup Hwang, Joon-Mo Yang, Jun Ki Kim and Woo June Choi

Biosensors 2025, 15(8), 522; https://doi.org/10.3390/bios15080522 - 9 Aug 2025

Full-field optical coherence tomography (FF-OCT) is a high-resolution interferometric imaging technique that enables label-free visualization of cellular structural changes. In this study, we employed a custom-built time-domain FF-OCT system to monitor morphological alterations in HeLa cells undergoing doxorubicin-induced apoptosis and ethanol-induced necrosis at [...] Read more.

Full-field optical coherence tomography (FF-OCT) is a high-resolution interferometric imaging technique that enables label-free visualization of cellular structural changes. In this study, we employed a custom-built time-domain FF-OCT system to monitor morphological alterations in HeLa cells undergoing doxorubicin-induced apoptosis and ethanol-induced necrosis at the single-cell level. Apoptotic cells showed characteristic features such as echinoid spine formation, cell contraction, membrane blebbing, and filopodia reorganization. In contrast, necrotic cells exhibited rapid membrane rupture, intracellular content leakage, and abrupt loss of adhesion structure. These dynamic events were visualized using high-resolution tomography and three-dimensional surface topography mapping. Furthermore, FF-OCT-based interference reflection microscopy (IRM)-like imaging effectively highlighted changes in cell–substrate adhesion and cell boundary integrity during the cell death process. Our findings suggest that FF-OCT is a powerful imaging platform for distinguishing cell death pathways and assessing dynamic cellular states, with potential applications in drug toxicity testing, anticancer therapy evaluation, and regenerative medicine. Full article

(This article belongs to the Special Issue Optical Sensors for Biological Detection)

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15 pages, 2370 KiB

Open AccessArticle

Microneedle–Tissue Interaction Across Varying Biological and Mechanical Conditions

by Elham Lori Zoudani, Prabuddha De Saram, Kyle Engel, Nam-Trung Nguyen and Navid Kashaninejad

Biosensors 2025, 15(8), 521; https://doi.org/10.3390/bios15080521 - 9 Aug 2025

Microneedle (MN)–tissue interactions play a critical role in the efficiency and reliability of transdermal drug delivery and biosensing, yet their mechanistic understanding remains limited. This study systematically investigates the effects of biological (tissue type and temperature) and mechanical (needle design, material, and insertion [...] Read more.

Microneedle (MN)–tissue interactions play a critical role in the efficiency and reliability of transdermal drug delivery and biosensing, yet their mechanistic understanding remains limited. This study systematically investigates the effects of biological (tissue type and temperature) and mechanical (needle design, material, and insertion velocity) parameters on the performance of microneedle insertion and extraction. Experiments were performed on porcine skin, chicken breast, and agarose gel to represent varying tissue properties. Additionally, the effect of tissue temperature on replicating physiological conditions, such as hypo- and hyperthermia, was evaluated using porcine skin as the sample. A novel conical MN design integrated with surface suction-cup structures was developed to improve tissue adhesion. Mechanical responses were analyzed through force–displacement measurements, evaluating insertion force, extraction force, and relaxation time. Results show that elevated tissue temperature reduces insertion and extraction forces while shortening relaxation times, indicating increased tissue compliance. The suction-cup MNs significantly enhanced needle–tissue adhesion, with the most pronounced effect observed in chicken breast tissue, achieving more than a four-fold increase in extraction force compared to conventional conical needles. These findings provide valuable insights into optimizing the design of MNs for advanced biomedical applications. Full article

(This article belongs to the Special Issue Nano/Micro Biosensors for Biomedical Applications (2nd Edition))

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14 pages, 5194 KiB

Open AccessArticle

Drying-Induced Salt Deposition Patterns as a Tool for Label-Free Protein Quantification

by Arturo Patrone-Garcia, Miquel Avella-Oliver and Ángel Maquieira

Biosensors 2025, 15(8), 520; https://doi.org/10.3390/bios15080520 - 9 Aug 2025

This work reports a label-free analytical strategy based on protein-induced modulation of salt crystallization patterns upon drying. This method relies on the consistent observation that protein-containing saline samples produce distinct salt deposition morphologies compared to protein-free controls. The work first demonstrates the concept [...] Read more.

This work reports a label-free analytical strategy based on protein-induced modulation of salt crystallization patterns upon drying. This method relies on the consistent observation that protein-containing saline samples produce distinct salt deposition morphologies compared to protein-free controls. The work first demonstrates the concept of this phenomenon and characterizes the structural features of the resulting salt patterns. Then, systematic experiments with different solution compositions, substrates, surface coatings, and protein types confirm the generality of this differential deposition behavior and its dependence on total protein concentration. Two complementary measurement approaches are evaluated: a custom laser-scattering setup for optical attenuation measurements and a digital image analysis method based on pixel intensity distributions. Both strategies enable quantitative protein detection in simple (casein) and complex (human serum) samples, offering good correlations between signal and concentration and detection limits in the range of 2–18 µg·mL⁻¹ for digital image analysis and 162–205 µg·mL⁻¹ for optical attenuation measurements. These findings introduce an appealing paradigm for protein quantification exploiting drying-mediated crystallization phenomena, with potential for simple and label-free bioanalytical assays. Full article

(This article belongs to the Special Issue Optical Sensors for Biological Detection)

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12 pages, 2679 KiB

Open AccessArticle

Polypyrrole-Modified Saccharomyces cerevisiae Used in Microbial Fuel Cell

by Kasparas Kižys, Domas Pirštelis, Ingrida Bružaitė and Inga Morkvėnaitė

Biosensors 2025, 15(8), 519; https://doi.org/10.3390/bios15080519 - 9 Aug 2025

Microbial fuel cells (MFCs) are one of the contributors to the novel sustainable energy generation from organic waste. However, the application of MFCs is limited due to the slow charge transfer between cells and electrodes. This problem can be solved by modifying cells [...] Read more.

Microbial fuel cells (MFCs) are one of the contributors to the novel sustainable energy generation from organic waste. However, the application of MFCs is limited due to the slow charge transfer between cells and electrodes. This problem can be solved by modifying cells with conductive polymers, such as polypyrrole (PPy). We investigated the viability and electroactivity of modified cells at five different pyrrole concentrations, namely 8, 25, 50, 100, and 200 mM. The 100 mM concentration of PPy solution had the highest impact on yeast cells’ proliferation and growth, with the CFU/mL of PPy-treated yeast cells being 0.6 × 10⁷ ± 5 × 10⁻². The power density of the constructed MFC was evaluated by using an external load. The MFCs were analyzed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Although CV results with different pyrrole concentrations were similar, DPV indicated that yeast modification with 50 mM pyrrole resulted in the most significant current density, which may be attributed to an increase in charge transfer due to the conductive properties of polypyrrole. The power density achieved with modified yeast in wastewater, 12 mW/m², reached levels similar to those in laboratory solutions, 45 mW/m². Full article

(This article belongs to the Section Biosensor Materials)

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17 pages, 1719 KiB

Open AccessArticle

A DNA Adsorption-Based Biosensor for Rapid Detection of Ratoon Stunting Disease in Sugarcane

by Moutoshi Chakraborty, Shamsul Arafin Bhuiyan, Simon Strachan, Muhammad J. A. Shiddiky, Nam-Trung Nguyen, Narshone Soda and Rebecca Ford

Biosensors 2025, 15(8), 518; https://doi.org/10.3390/bios15080518 - 8 Aug 2025

Early and accurate detection of plant diseases is critical for ensuring global food security and agricultural resilience. Ratoon stunting disease (RSD), caused by the bacterium Leifsonia xyli subsp. xyli (Lxx), is among the most economically significant diseases of sugarcane worldwide. Its [...] Read more.

Early and accurate detection of plant diseases is critical for ensuring global food security and agricultural resilience. Ratoon stunting disease (RSD), caused by the bacterium Leifsonia xyli subsp. xyli (Lxx), is among the most economically significant diseases of sugarcane worldwide. Its cryptic nature—characterized by an absence of visible symptoms—renders timely diagnosis particularly difficult, contributing to substantial undetected yield losses across major sugar-producing regions. Here, we report the development of a potential-induced electrochemical (EC) nanobiosensor platform for the rapid, low-cost, and field-deployable detection of Lxx DNA directly from crude sugarcane sap. This method eliminates the need for conventional nucleic acid extraction and thermal cycling by integrating the following: (i) a boiling lysis-based DNA release from xylem sap; (ii) sequence-specific magnetic bead-based purification of Lxx DNA using immobilized capture probes; and (iii) label-free electrochemical detection using a potential-driven DNA adsorption sensing platform. The biosensor shows exceptional analytical performance, achieving a detection limit of 10 cells/µL with a broad dynamic range spanning from 10⁵ to 1 copy/µL (r = 0.99) and high reproducibility (SD < 5%, n = 3). Field validation using genetically diverse sugarcane cultivars from an inoculated trial demonstrated a strong correlation between biosensor signals and known disease resistance ratings. Quantitative results from the EC biosensor also showed a robust correlation with qPCR data (r = 0.84, n = 10, p < 0.001), confirming diagnostic accuracy. This first-in-class EC nanobiosensor for RSD represents a major technological advance over existing methods by offering a cost-effective, equipment-free, and scalable solution suitable for on-site deployment by non-specialist users. Beyond sugarcane, the modular nature of this detection platform opens up opportunities for multiplexed detection of plant pathogens, making it a transformative tool for early disease surveillance, precision agriculture, and biosecurity monitoring. This work lays the foundation for the development of a universal point-of-care platform for managing plant and crop diseases, supporting sustainable agriculture and global food resilience in the face of climate and pathogen threats. Full article

(This article belongs to the Special Issue Nanomaterial-Based Biosensors for Point-of-Care Testing)

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19 pages, 3018 KiB

Open AccessArticle

Development and Characterisation of a Microneedle Sensor for Intrapartum Fetal Monitoring

by J. M. Mitchell, C. V. Thatte, R. Sebastian, C. O’Mahony, R. A. Greene, J. R. Higgins, P. Galvin, F. P. McCarthy and S. R. Teixeira

Biosensors 2025, 15(8), 517; https://doi.org/10.3390/bios15080517 - 8 Aug 2025

This study presents the in vitro and preliminary ex vivo development of a novel microneedle-based pH sensor for continuous intrapartum fetal monitoring. The objective was to evaluate the feasibility of using microneedle sensors to monitor fetal pH during labour and to develop a [...] Read more.

This study presents the in vitro and preliminary ex vivo development of a novel microneedle-based pH sensor for continuous intrapartum fetal monitoring. The objective was to evaluate the feasibility of using microneedle sensors to monitor fetal pH during labour and to develop a proof-of-principle microneedle pH sensor that meets clinical requirements such as high sensitivity to small pH changes (0.05 units) within a relevant range (6.50–7.45), minimal tissue disruption, and a compact design suitable for transcervical placement on the fetal scalp (<40 mm diameter). Platinum microneedles were passivated with ArCare medical adhesive and coated with iridium oxide via electrodeposition. Sensitivity was tested in phosphate buffered saline (PBS) and artificial interstitial fluid (ISF), using both external Ag/AgCl and internal platinum pseudo-reference electrodes. In PBS, the sensor exhibited linear responses in increments of 0.05 pH units over the clinically relevant range (6.5–7.45), with slopes of −60.49 mV/pH (R² = 0.946, accuracy = 97.65%) and −63.2 mV/pH (R² = 0.910, accuracy = 93.70%) in the external and internal configurations, respectively. In ISF, a slope of −25.5 mV/pH (R² = 0.979) was obtained. Ex vivo testing on human skin confirmed successful microneedle penetration without visible iridium oxide transfer or tissue damage, as indicated by methylene blue staining. These findings support the potential for continuous minimally invasive fetal pH monitoring during labour, representing a significant step toward more objective and specific intrapartum assessment. Full article

(This article belongs to the Special Issue Nano/Micro Biosensors for Biomedical Applications (2nd Edition))

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16 pages, 25225 KiB

Open AccessArticle

Theory Design of a Virtual Polarizer with Multiscale and Multi-Biomass Sensing

by Chuanqi Wu and Haifeng Zhang

Biosensors 2025, 15(8), 516; https://doi.org/10.3390/bios15080516 - 8 Aug 2025

Recently, more and more attention has been paid to human health with the rapid development of society. A designed virtual polarizer (VP) can realize multiscale and multi-biomass sensing, including temperature, cancerous cells, and COVID-19. Based on coherent perfect polarization conversion, a certain polarization [...] Read more.

Recently, more and more attention has been paid to human health with the rapid development of society. A designed virtual polarizer (VP) can realize multiscale and multi-biomass sensing, including temperature, cancerous cells, and COVID-19. Based on coherent perfect polarization conversion, a certain polarization conversion can be fulfilled within 1.72~2.14 THz. Then, through observing the displacement of a perfect matching point (PMP), variations in temperature can be accurately determined, covering from 299 K to 315 K, with a sensitivity (S) of 0.0198 THz/K. Moreover, a sharp coherent perfect absorption (CPA) peak generated from the VP can be employed for the detection of cancerous cells and COVID-19. The refractive index (RI) detection range of cancerous cells is from 1.36 RIU to 1.41 RIU with the sensitivity being −4.45881 THz/RIU. The average quality factor (Q), figure of merit (FOM), and detection limit (DL) are 825.36, 241.11 RIU⁻¹, and −36.83 dB. For the COVID-19 solution concentration (SC) from 0 mM to 525 mM, by mapping SC to RI, the RI sensing range is 1.344 RIU–1.355 RIU with the S being −5.03467 THz/RIU. The relevant Q, FOM, and DL are 760.85, 244.94 RIU⁻¹, and −36.89 dB. Based on two strategies of PMP and CPA, the proposed VP is capable of multiscale and multi-biomass sensing with excellent detection performance, providing a new detection method for biosensing. Full article

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

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15 pages, 2906 KiB

Open AccessArticle

Cell Observation and Analysis with a Three-Dimensional Optical Wave Field Microscope

by Shimon Matsumoto, Shoko Itakura, Junta Minato, Masahiro Hashimoto, Shu Obana, Mai Kanai, Masaki Kobayashi, Makiya Nishikawa and Kosuke Kusamori

Biosensors 2025, 15(8), 515; https://doi.org/10.3390/bios15080515 - 8 Aug 2025

Cell observation is crucial in life science research, and advancements in microscopy are essential for deciphering biological phenomena. These technological developments have significantly enhanced our understanding of cellular mechanisms and processes. Light, characterized by its wave-like properties, is fundamental to scientific observation. Recently, [...] Read more.

Cell observation is crucial in life science research, and advancements in microscopy are essential for deciphering biological phenomena. These technological developments have significantly enhanced our understanding of cellular mechanisms and processes. Light, characterized by its wave-like properties, is fundamental to scientific observation. Recently, new technologies have been developed to detect changes in light wavelengths upon illumination, using them as signals for visualization. Three-dimensional optical wave field microscopy (3D-OWFM), a recent innovation in optimal imaging, leverages the wave properties of light to capture objects without labels, invasive procedures, or direct contact, thus facilitating non-invasive observation. In this study, we observed and analyzed mammalian cell structure and behaviors using 3D-OWFM. The 3D-OWFM revealed the intrinsic structure of the cells, including the cytoplasm and nucleus, with high clarity. The optical path difference (OPD) intensity effectively highlighted nuclear complexity. Furthermore, time-lapse imaging captured cell division process through variations in OPD signal intensity. These findings indicate that 3D-OWFM has significant potential for cell observation, offering insights not attainable with conventional microscopes. Full article

(This article belongs to the Special Issue Biosensing Applications for Cell Monitoring)

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19 pages, 8504 KiB

Open AccessArticle

Fiber-Based Ultra-High-Speed Diffuse Speckle Contrast Analysis System for Deep Blood Flow Sensing Using a Large SPAD Camera

by Quan Wang, Renzhe Bi, Songhua Zheng, Ahmet T. Erdogan, Yi Qi, Chenxu Li, Yuanyuan Hua, Mingliang Pan, Yining Wang, Neil Finlayson, Malini Olivo, Robert K. Henderson and David Uei-Day Li

Biosensors 2025, 15(8), 514; https://doi.org/10.3390/bios15080514 - 7 Aug 2025

Diffuse speckle contrast analysis (DSCA), also called speckle contrast optical spectroscopy (SCOS), has emerged as a groundbreaking optical imaging technique for tracking dynamic biological processes, including blood flow and tissue perfusion. Recent advancements in single-photon avalanche diode (SPAD) cameras have unlocked exceptional sensitivity, [...] Read more.

Diffuse speckle contrast analysis (DSCA), also called speckle contrast optical spectroscopy (SCOS), has emerged as a groundbreaking optical imaging technique for tracking dynamic biological processes, including blood flow and tissue perfusion. Recent advancements in single-photon avalanche diode (SPAD) cameras have unlocked exceptional sensitivity, time resolution, and high frame-rate imaging capabilities. Despite this, the application of large-format SPAD arrays in speckle contrast analysis is still relatively uncommon. This study introduces a pioneering use of a large-format SPAD camera for DSCA. By harnessing the camera’s high temporal resolution and photon-detection efficiency, we significantly enhance the accuracy and robustness of speckle contrast measurements. Our experimental results demonstrate the system’s remarkable ability to capture rapid temporal variations over a broad field of view, enabling detailed spatiotemporal analysis. Through simulations, phantom experiments, and in vivo studies, we validated the proposed approach’s potential for cerebral blood flow and functional tissue monitoring. This work highlights the transformative impact of large SPAD cameras on DSCA, setting the stage for breakthroughs in optical imaging. Full article

(This article belongs to the Special Issue Optical Biosensors for Healthcare: An Artificial Intelligence Approach)

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