Search Results (89)

Alterations in the expression of the Klotho gene have been associated with chronic kidney disease (CKD), and its potential as an early diagnostic biomarker is currently under active investigation. In this work, we report the development of a highly sensitive, label-free electrochemical DNA-based biosensor for the detection of a 100 mer DNA fragment corresponding to a partial region of Klotho mRNA. The proposed bioplatform integrates mixed self-assembled monolayers (SAMs) and gold nanoparticles for efficient DNA immobilization within a sandwich-type configuration, coupled with impedimetric detection. Different SAM architectures were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy, with the binary monolayer composed of 1-hexadecanethiol (HDT) and the capture probe (CP) exhibiting the best analytical performance. The use of gold nanoparticle-modified screen-printed carbon electrodes (AuNPs–SPCEs) resulted in a 1.4-fold increase in the signal-to-noise ratio compared to screen-printed gold electrodes. Additionally, the incorporation of a blocking step using bovine serum albumin (BSA–HDT–CP–AuNPs–SPCE) enhanced the sensitivity by 1.6-fold compared to the unblocked system. The genosensor displayed a linear response in the concentration range of 3 × 10⁻¹⁰ to 7.5 × 10⁻⁸ M, achieving a detection limit of 0.09 nM. Relative standard deviations below 7.5% were obtained for different Klotho concentrations, confirming high intra-assay and intermediary precision. Selectivity assays demonstrated negligible signals for non-complementary sequences, while recovery experiments in spiked human serum samples yielded satisfactory values between 96.5% and 103.4%. Full article

We report a non-enzymatic electrochemical sensing platform for creatinine based on a nickel-nanoparticle/carbon-quantum-dot (NiNP–CQD) hybrid interface. In this system, the analytical signal originates from the direct electrocatalytic oxidation of creatinine mediated by the Ni(II)/Ni(III) redox couple (Ni(OH)₂/NiOOH), which forms during electrochemical activation of nickel in alkaline media. These redox centers act as catalytic sites that oxidize creatinine without requiring enzymes or biomolecular labels. The CQDs provide a conductive sp²-rich network with abundant oxygenated groups that promote homogeneous nucleation and dispersion of NiNPs, enhancing both surface area and electron-transfer efficiency. Electrochemical characterization of the modified electrodes was performed using the ferricyanide/ferrocyanide redox couple as the electron-transfer probe. Structural and microscopic characterization confirms uniform NiNP deposition on the CQD layer, while electrochemical studies demonstrates that the composite outperforms CQDs or NiNPs alone in current density, linearity, and resistance to active-site saturation. The resulting sensor exhibits a wide linear range (10–1000 µM), high area-normalized sensitivity (1.41 µA µM⁻¹ cm⁻²), and a low detection limit of 5 µM. Selectivity tests reveal minimal interference from common physiological species. By explicitly leveraging a catalyst-driven, enzyme-free oxidation pathway, this NiNP–CQD architecture provides a robust, stable, and scalable platform for clinically relevant creatinine detection. Full article

Early diagnosis of Alzheimer’s disease (AD) remains challenging due to the extremely low concentration of relevant biomarkers and the limited sensitivity of conventional detection techniques. In this study, we present a carbon nanotube field-effect transistor (CNT-FET) immunosensor for label-free detection of phosphorylated tau at threonine 217 (p-tau217). The device employs a Y₂O₃/HfO₂ dielectric layer and gold nanoparticles (AuNPs) to improve biofunctionalization, with anti-p-tau217 antibodies immobilized on the CNT channels. In phosphate-buffered saline (PBS), the sensor exhibited a linear response over a concentration range of 3 fM to 30 pM (R² = 0.973) and achieved a limit of detection (LOD) of 1.66 fM. The device demonstrated high selectivity, with a normalized signal response (NSR) for p-tau217 that was 5–6 times higher than for human serum albumin (HSA) and p-tau231, even at 1000-fold higher concentrations of these interferents. The sensor exhibited reproducibility with a relative standard deviation (RSD) of 4.8% (n = 9) and storage stability with only a 10% decrease in signal after 7 days at 4 °C. Mechanistic analysis indicated that the net positive charge and structural flexibility of the p-tau217 peptide led to a reduction in drain current upon binding, consistent with electrostatic gating effects in p-type CNT-FETs. Current limitations include the absence of standardized p-tau217 reference materials. Future work will focus on validation with clinical samples. This CNT-FET platform enables rapid, minimally invasive detection of p-tau217 and holds strong potential for integration into clinical workflows to facilitate early AD diagnosis. Full article

Single-molecule detection (SMD) has reformed analytical science by enabling the direct observation of individual molecular events, thus overcoming the limitations of ensemble-averaged measurements. This review presents a comprehensive analysis of the principles, devices, and emerging materials that have shaped the current landscape of SMD. We explore a wide range of sensing mechanisms, including surface plasmon resonance, mechanochemical transduction, transistor-based sensing, optical microfiber platforms, fluorescence-based techniques, Raman scattering, and recognition tunneling, which offer distinct advantages in terms of label-free operation, ultrasensitivity, and real-time responsiveness. Each technique is critically examined through representative case studies, revealing how innovations in device architecture and signal amplification strategies have collectively pushed the detection limits into the femtomolar to attomolar range. Beyond the sensing principles, this review highlights the transformative role of advanced nanomaterials such as graphene, carbon nanotubes, quantum dots, MnO₂ nanosheets, upconversion nanocrystals, and magnetic nanoparticles. These materials enable new transduction pathways and augment the signal strength, specificity, and integration into compact and wearable biosensing platforms. We also detail the multifaceted applications of SMD across biomedical diagnostics, environmental monitoring, food safety, neuroscience, materials science, and quantum technologies, underscoring its relevance to global health, safety, and sustainability. Despite significant progress, the field faces several critical challenges, including signal reproducibility, biocompatibility, fabrication scalability, and data interpretation complexity. To address these barriers, we propose future research directions involving multimodal transduction, AI-assisted signal analytics, surface passivation techniques, and modular system design for field-deployable diagnostics. By providing a cross-disciplinary synthesis of device physics, materials science, and real-world applications, this review offers a comprehensive roadmap for the next generation of SMD technologies, poised to impact both fundamental research and translational healthcare. Full article

Due to their unique physicochemical properties, carbon black nanoparticles represent a promising alternative for solving analytical problems. However, diagnostic reagents based on carbon black nanoparticles have not yet found widespread practical application. This review examines the development and application of carbon black nanoparticle conjugates with recognition molecules as diagnostic reagents in test systems that enable non-instrumental interpretation of results. The review critically evaluates the methods for synthesis and characterization of carbon black-based diagnostic reagents. Furthermore, the review summarizes and discusses existing studies comparing the effectiveness of carbon black nanoparticle-based bioconjugates with traditional colorimetric labels. The scientific articles included in the review were carefully analyzed for the presence of an assessment of the reproducibility of methods for obtaining diagnostic reagents based on carbon black nanoparticles and their long-term storage. The main challenges and future prospects of using carbon black nanoparticles in immunoassays are discussed. Full article

Herein, we propose an ultrasensitive electrochemical immunosensor based on glucose oxidase labeling and enzyme-catalyzed Au staining. In brief, the primary antibody (Ab₁), bovine serum albumin, an antigen and then a bionanocomposite that contains a second antibody (Ab₂), poly(3-anilineboronic acid) (PABA), Au nanoparticles (AuNPs) and glucose oxidase (GOx) are modified on a glassy carbon electrode coated with multiwalled carbon nanotubes, yielding a corresponding sandwich-type immunoelectrode. In the presence of glucose, a chemical reduction of NaAuCl₄ by enzymatically generated H₂O₂ can precipitate a lot of gold on the Ab₂-PABA-AuNPs-GOx immobilized immunoelectrode. In situ anodic stripping voltammetry (ASV) detection of gold in 8 μL 1.0 M aqueous HBr-Br₂ is conducted for the antigen assay, and the ASV detection process takes approximately 6 min. This method is employed for the assay of human immunoglobulin G (IgG) and human carbohydrate antigen 125 (CA125), which demonstrates exceptional sensitivity, high selectivity and fewer required reagents/samples. The achieved limits of detection (S/N = 3) by the method are 0.25 fg mL⁻¹ for IgG (approximately equivalent to containing 1 IgG molecule in the 1 microlitre of the analytical solution) and 0.1 nU mL⁻¹ for CA125, which outperforms many previously reported results. Full article

Carbon dots (CDs) derived from renewable biomass are emerging as sustainable alternatives to traditional nanomaterials for applications in bioimaging, sensing, and photonics. In this study, we reported a one-step synthesis of photoluminescent CDs from Laurus nobilis leaves particularly spread in the Mediterranean area. The resulting nanoparticles (NPs) exhibited average diameters of 3–5 nm and high colloidal stability in water. Structural analysis by X-Rays Diffraction revealed the presence of amorphous graphitic domains, while infrared spectroscopy confirmed oxygenated functional groups on the CD surface. Spectrofluorimetric analysis showed excitation-dependent blue–green emission with a maximum at 490 nm that can be applied also as label agents for cells. The environmental sustainability of the synthetic procedure was evaluated through a Life Cycle Assessment (LCA), highlighting that the current impacts were primarily associated with electricity consumption, due to the laboratory-scale nature of the process. These impacts are expected to decrease significantly with future scale-up and process optimization. Full article

The lateral flow immunoassay (LFIA) is a widely utilized, rapid diagnostic technique characterized by its short analysis duration, cost efficiency, visual result interpretation, portability and suitability for point-of-care applications. However, conventional LFIAs have limited sensitivity, a challenge that can be overcome by the introduction of gold nanoparticles, which provide enhanced sensitivity and selectivity (compared, for example, to latex beads or carbon nanoparticles) for the detection of target analytes, due to their optical properties, chemical stability and ease of functionalization. In this work, gold nanoparticle-based LFIAs are developed for the detection of aflatoxin B1, and the relative performance of different morphology particles is evaluated. LFIA using gold nano-labels allowed for aflatoxin B1 detection over a range of 0.01 ng/mL–100 ng/mL. Compared to spherical gold nanoparticles and gold nano-flowers, star-shaped gold nanoparticles show increased antibody binding efficiency of 86% due to their greater surface area. Gold nano-stars demonstrated the highest sensitivity, achieving a limit of detection of 0.01ng/mL, surpassing the performance of both spherical gold nanoparticles and gold nano-flowers. The use of star-shaped particles as nano-labels has demonstrated a five-fold improvement in sensitivity, underscoring the potential of integrating diverse nanostructures into LFIA for significantly improving analyte detection. Moreover, the robustness and feasibility of gold nano-stars employed as labels in LFIA was assessed in detecting aflatoxin B1 in a wheat matrix. Improved sensitivity with gold nano-stars holds promise for applications in food safety monitoring, public health diagnostics and rapid point-of-care diagnostics. This work opens the pathway for further development of LFIA utilizing novel nanostructures to achieve unparallel precision in diagnostics and sensing. Full article

Glycated hemoglobin (HbA1c) is an important biomarker applied for the diagnosis, evaluation, and management of diabetes; therefore, its accurate determination is crucial. In this study, an innovative nanoplatform was developed, integrating carbon nanotubes (CNTs) with enhanced hydrophilicity achieved through cyclodextrin (CD) functionalization, and combined with gold nanoparticles (AuNPs) electrochemically deposited onto a screen-printed carbon electrode. The nanomaterials significantly improved the analytical performance of the sensor due to their increased surface area and high electrical conductivity. This nanoplatform was employed as a substrate for the covalent attachment of thiolated ferrocene-labeled HbA1c specific aptamer through Au-S binding. The electrochemical signal of ferrocene was covered by a stronger oxidation peak of Fe²⁺ from the HbA1c structure, leading to the elaboration of a nanostructured aptasensor capable of the direct detection of HbA1c. The electrochemical aptasensor presented a very wide linear range (0.688–11.5%), an acceptable limit of detection (0.098%), and good selectivity and stability, being successfully applied on real samples. This miniaturized, simple, easy-to-use, and fast-responding aptasensor, requiring only a small sample volume, can be considered as a promising candidate for the efficient on-site determination of HbA1c. Full article

Alkaline earth elements have emerged as crucial electronic modifiers for regulating active sites in catalytic systems, yet the influence of metal–support interactions (MSIs) between alkaline earth compounds and active metals remains insufficiently understood. This study systematically investigated Pt nanoparticles supported on alkaline earth carbonates (Pt/MCO₃, M = Mg, Ca, Ba) for low-temperature propylene combustion. The Pt/BaCO₃ catalyst exhibited outstanding performance, achieving complete propylene conversion at 192 °C, significantly lower than Pt/MgCO₃ (247 °C) and Pt/CaCO₃ (282 °C). The enhanced activity stemmed from distinct MSI effects among the supports, with Pt/BaCO₃ showing the poorest electron enrichment and lowest propylene adsorption energy. Through kinetic analyses, ¹⁸O₂ isotope labeling, and comprehensive characterization, the reaction was confirmed to follow the Mars–van Krevelen (MvK) mechanism. Pt/BaCO₃ achieves an optimal balance between propylene and oxygen adsorption, a critical factor underlying its superior activity. Full article

Detecting multiple tumor markers is of great importance. It helps in early cancer detection, accurate diagnosis, and monitoring treatment. In this work, gold nanoparticles–toluidine blue–graphene oxide (AuNPs-TB–GO) and gold nanoparticles–carboxyl ferrocene–tungsten disulfide (AuNPs–FMC–WS₂) nanocomposites were prepared for labeling Carcinoembryonic antigen (CEA) antibody and Carbohydrate antigen 72–4 (CA72-4) antibody, respectively, and used as two kinds of probes with different electrochemical signals. With the excellent magnetic performance of biotin immune magnetic beads (IMBs), the biofunctional IMBs were firmly deposited on the magnetic glassy carbon electrode (MGCE) surface by applying a constant magnetic field, and then the CEA and CA72-4 antibody were immobilized on the IMBs by the avidin–biotin conjugation. The assay was based on the change in the detection peak current. Under the optimum experimental conditions, the linear range of detection of CEA is of the two-component immunosensor is from 0.01 to 120 ng/mL, with a low detection limit of 0.003 ng/mL, and the linear range of detection of CA72-4 is from 0.05 to 35 U/mL, with a detection limit of 0.016 U/mL. The results showed that the proposed immunosensor enabled simultaneous monitoring of CEA and CA72-4 and exhibited good reproducibility, excellent high selectivity, and sensitivity. In particular, the proposed multiplexed immunoassay approach does not require sophisticated fabrication and is well-suited for high-throughput biosensing and application to other areas. Full article

In order to identify carcinoembryonic antigen (CEA) in serum samples, an innovative smartphone-based, label-free electrochemical immunosensor was created without the need for additional labels or markers. This technology presents a viable method for on-site cancer diagnostics. The novel smartphone-integrated, label-free immunosensing platform was constructed by nanostructured materials that utilize the layer-by-layer (LBL) assembly technique, allowing for meticulous control over the interface. Detection relies on direct interactions without extra tagging agents, where ordered graphene oxide (GO), carbon nanotubes (CNTs), and copper oxide nanoparticles (CuONPs) were sequentially deposited onto a screen-printed carbon electrode (SPCE), designated as CuONPs/CNTs/GO/SPCE. This significantly amplifies the electrochemical signal, allowing for the detection of low concentrations of target molecules of CEA. The LBL approach enables the precise construction of multi-layered structures on the sensor surface, enhancing their activity and optimizing the electrochemical performance for CEA detection. These nanostructured materials serve as efficient carriers to significantly increase the surface area, conductivity, and structural support for antibody loading, thus improving the sensitivity of detection. The detection of carcinoembryonic antigen (CEA) in this electrochemical immunosensing transducer is based on a decrease in the current response of the [Fe(CN)₆]^3−/4− redox probes, which occurs in proportion to the amount of the immunocomplex formed on the sensor surface. Under the optimized conditions, the immunosensor exhibited good detection of CEA with a linear range of 0.1–5.0 ng mL⁻¹ and a low detection limit of 0.08 ng mL⁻¹. This label-free detection approach, based on signal suppression due to immunocomplex formation, is highly sensitive and efficient for measuring CEA levels in serum samples, with higher recovery ranges of 101% to 112%, enabling early cancer diagnosis. The immunosensor was successfully applied to determine CEA in serum samples. This immunosensor has several advantages, including simple fabrication, portability, rapid analysis, high selectivity and sensitivity, and good reproducibility with long-term stability over 21 days. Therefore, it has the potential for point-of-care diagnosis of lung cancer. Full article

Food safety is of great concern, and food-borne bacterial infections and diseases are a major crisis for health. Therefore, it is necessary to develop rapid detection techniques for the prevention and recognition of food safety hazards caused by food-borne pathogens. In recent years, the fluorescence assay has become a widely utilized detection method due to its good signal amplification effect, high detection sensitivity, high stability, and short detection time. In this review, the different kinds of fluorescence materials were concentrated, including quantum dots (QDs), carbon dots (CDs), metal–organic frameworks (MOFs), and upconversion nanoparticles (UCNPs). The optical properties and applications of different kinds of fluorescent materials were analyzed and compared. Furthermore, according to the biosensing components, different fluorescence biosensors are reviewed, including label-free based fluorescence probes, aptamer-based biosensors, and antibody-based biosensors. Finally, we focused our attention on the discussion of fluorescent detection techniques combined with other techniques and their applications. The review presents future trends in fluorescence sensors, providing new sights for the detection of food-borne pathogens. Full article

Cardiac troponin I (cTnI) monitoring is of great value in the clinical diagnosis of acute myocardial infarction (AMI). In this paper, a highly sensitive electrochemical aptamer sensor using polystyrene (PS) microspheres as the electrode substrate material in combination with Prussian blue (PB) and gold nanoparticles (AuNPs) was demonstrated for the sensitive and label-free determination of cTnI. PS microspheres were synthesized by emulsion polymerization and then dropped onto the glassy carbon electrode (GCE); PB and AuNPs were electrodeposited on the electrode in corresponding electrolyte solutions step by step. The PS microsphere substrate provided a large surface area for the loading mass of the biological affinity aptamers, while the PB layer improved the electrical conductivity of the modified electrode, and the electroactive AuNPs exhibited excellent catalytic performance for the subsequent electrochemical measurements. In view of the above mentioned AuNPs/PB/PS/GCE sensing platform, the fabricated label-free electrochemical aptamer sensor exhibited a wide detection range of 10 fg/mL~1.0 μg/mL and a low detection limit of 2.03 fg/mL under the optimal conditions. Furthermore, this biosensor provided an effective detection platform for the analysis of cTnI in serum samples. The introduction of this sensitive electrochemical aptamer sensor provides a reference for clinically sensitive detection of cTnI. Full article

Reliable cell labeling and tracking techniques are imperative for elucidating the intricate and ambiguous interactions between mesenchymal stromal cells (MSCs) and tumors. Here, we explore fluorescent photoconvertible nanoengineered vesicles to study mMSC migration in brain tumors. These 3 μm sized vesicles made of carbon nanoparticles, Rhodamine B (RhB), and polyelectrolytes are readily internalized by cells. The dye undergoes photoconversion under 561 nm laser exposure with a fluorescence blue shift upon demand. The optimal laser irradiation duration for photoconversion was 0.4 ms, which provided a maximal blue shift of the fluorescent signal label without excessive laser exposure on cells. Vesicles modified with an extra polymer layer demonstrated enhanced intracellular uptake without remarkable effects on cell viability, motility, or proliferation. The optimal ratio of 20 vesicles per mMSC was determined. Moreover, the migration of individual mMSCs within 2D and 3D glioblastoma cell (EPNT-5) colonies over 2 days and in vivo tumor settings over 7 days were traced. Our study provides a robust nanocomposite platform for investigating MSC–tumor dynamics and offers insights into envisaged therapeutic strategies. Photoconvertible vesicles also present an indispensable tool for studying complex fundamental processes of cell–cell interactions for a wide range of problems in biomedicine. Full article