Snakebite envenoming is predominantly a life-threatening occupational disease caused by venom proteins in the bite of a venomous snake. The development of reliable rapid diagnostics is the need of the hour for timely snakebite diagnosis and the early administration of antivenom for treatment. Magnetic nanoparticles (MNPs) conjugated with antibodies have been extensively explored for the selective detection of biomarkers for diagnostic purposes. The purpose of the current study is to develop antivenom antibody-immobilized MNPs for the efficient immunodetection of snake venom proteins. Iron oxide magnetic nanoparticles were synthesized by the co-precipitation of Fe²⁺ and Fe³⁺ in sodium hydroxide (NaOH) solution. These MNPs were functionalized by sodium citrate solution. The synthesized citrate-capped MNPs with at least one carboxylic acid group on the surface were used for the immobilization of F(ab¢)₂ antibodies present in commercially available polyvalent antivenom. For the site-directed immobilization of antibodies, EDC-NHS ((1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N hydroxysuccinimide)) was used as linker. The antibody-immobilized and non-immobilized MNPs were characterized by X-ray diffraction and Fourier-transform infrared spectrometry analysis, and their size was estimated with the help of zeta potential. To validate the performance of antibody-conjugated MNPs in detecting snake venom proteins, a dot blot assay was performed using Russell’s viper venom protein antigens. The presence of snake venom-specific phospholipase A₂ (PLA₂) in human serum is an early indicator of snake bite envenomation and serves as a potential biomarker for the detection of free-flowing venom protein. Thus, antibody-immobilized MNPs were used as an immunoaffinity-based platform to capture a purified viper venom PLA₂. The present study demonstrated the successful conjugation of antibodies to the surface of magnetic nanoparticles and their ability to recognize viper venom proteins. Further, antibody-coated MNPs displayed the capability to effectively immunocapture a venom PLA₂ protein. Such antibody-coated nanoparticle-based immunodetection platforms will provide efficient enrichment and selective separation of snake venom-specific venom proteins from human serum. Additionally, immunoaffinity platforms based on nanoparticles for snake venom proteins with high sensitivity and high purity, and quick characterization will facilitate the early diagnosis of snakebite envenomation.

Introduction: Trichothecene mycotoxins are produced by several species of Fusarium, such as Fusarium langsethiae, acuinatum, sporotrichioide and poae. The T-2 toxin is one of the most toxics and is widely distributed throughout the world, contaminating cereals such as barley, corn, oats, wheat and rice, as well as various cereal products. We developed a portable immunosensor for T-2 mycotoxin electrochemical quantification in mixed cereal samples.

Methods: A screen-printed carbon electrode was modified with a dual-function mesoporous nanostructure (CMK-9/KIT-6). The KIT-6 silica nanostructure was used as an immobilization platform for the anti-T-2 monoclonal antibodies, so the mycotoxin was detected using a competitive immunoassay method. Moreover, the carbon CMK-9 nanostructure increases the electroactive surface area, and therefore the sensitivity in the quantification. The nanocomposite CMK-9/KIT-6/SPCE was characterized by CV, Impedance, SEM, EDS, and Isotherms. In this way, the T-2 mycotoxin present in the sample competes with horseradish peroxidase (HRP)-conjugated T-2 for the specific recognition sites of the immobilized anti-T-2 antibodies. Then, the enzyme, in the presence of HRP, catalyzes the oxidation of catechol, whose electrochemical reduction was detected at the nanostructured electrode at -0.15 V. In this sense, the T-2 mycotoxin concentration in the sample was indirectly proportional to the T-2-conjugated HRP , showing a higher current by amperometry.

Results: The detection limits for the portable immunosensor with electrochemical detection and the Enzyme-Linked ImmunoSorbent Assay (ELISA) were 0.05 μg kg^-1 and 10 μg kg^-1, and the coefficients of variation (intra- and inter-assay) were below 4.29 % and 5.98 %, respectively.

Conclusions: The T-2 toxin electrochemical immunosensor is a valuable tool for portable in situ analysis of agri-food samples.

Introduction: Vascular endothelial growth factor (VEGF) is acknowledged as a crucial biomarker for tumor angiogenesis, playing a significant role in the progression, development, and metastasis of tumors. Therefore, developing an ultra-sensitive detection method for VEGF is vital for early cancer prevention and surveillance of disease status.

Methods: In this research, we constructed a sandwich-style quenching electrochemiluminescence (ECL) immunosensor by employing the mechanism of electrochemiluminescence resonance energy transfer (ECL-RET), aiming for highly sensitive identification of VEGF₁₆₅.

Results: The PTC@UIO-66-NH₂ complex was prepared by integrating the organic luminescent probe, derived from the ammonolysis of Perylene-3,4,9,10-tetracarboxylic dianhydride (PTC), into the UIO-66-NH₂ metal–organic framework. This complex was subsequently modified on the surface of a polished carbon electrode to serve as an ECL substrate. The VEGF antibody was then conjugated to this substrate via an amide reaction. Meanwhile, bovine serum albumin-functionalized MnO₂ nanosheets (BSA-MnO₂), which were linked to VEGF₁₆₅ aptamers, functioned as the ECL acceptor. Upon selective recognition and binding to VEGF₁₆₅, ECL-RET occurred between the PTC@UIO-66-NH₂ (ECL donor) and BSA-MnO₂ (ECL acceptor), leading to a significant reduction in the ECL signal, which could be readily captured by the instrument. Additionally, the intensity of the ECL response diminished as the concentration of VEGF₁₆₅ increased. Under optimal experimental conditions, the ECL immunosensor exhibited a linear detection range spanning from 5 pg/mL to 50 ng/mL, with a minimum detectable limit of 3.5 pg/mL, which underscores its exceptional sensitivity. Furthermore, the ECL-RET immunoassay was subjected to rigorous validation procedures to confirm its specificity and stability.

Conclusions: In a nutshell, our ECL immunosensor presents a novel method for the early identification of VEGF in human serum, offering a fresh approach for timely detection. Furthermore, this technology depicts its potential to function as a flexible and promising platform, capable of detecting other circulating tumor biomarkers.

A novel electrochemical sensor offering superior analytical performance criteria has been developed to quantify various biomolecules involved in life-threatening ailments [1,2]. The composite material comprises a layer of poly(3,4-ethylenedioxythiophene) conducting polymer (PEDOT) and platinum nanoparticles (PtNPs) electrodeposited on a glassy carbon electrode (GCE) surface through the application of a sinusoidal voltage (SV) procedure with tailored electrochemical parameters. The sinusoidal voltage method relies on the application of a sinusoidal voltage on a constant voltage for a precisely monitored timeframe. The antifouling capability of the polymeric matrix, combined with the enhanced sensitivity and the remarkable catalytic properties offered by the metallic nanoparticles, ensures the accurate and reliable detection of biologically important molecules. Moreover, the newly synthesized analytical device displays a trend of cost-effective production associated with the potential for additional functionalization using renewable or sustainable material sources for environmental protection. The GCE-PEDOT/PtNP electrochemical sensor was successfully implemented for serotonin determination in a synthetic buffer solution. The sensor responded selectively to serotonin, with a linear response range of 1-80 µM. The sensor’s optimum analytical capacity was validated, achieving a detection limit of 1.8 µM for the target analyte. Moreover, the analytical performance of the devised sensing platform proved to be in agreement with the data available in the literature. The results point to the effectiveness of the SV procedure for the selective determination of target analytes in a complex medium featuring various interfering molecules.

Acknowledgments: This work was performed within the research theme “Development of Electrochemical Sensors for Biologically Active Compounds Determination” of the Erasmus+ Traineeship Program between POLITEHNICA University of Bucharest and the University of Modena and Reggio Emilia.

References

[1] Leau et al. Chemosensors (2023). 11.3:179.

[2] Monari et al. Talanta (2025). 282-126958.

Biological nanomaterials that exhibit repetitive functionalities with high spatial precision, density, and orientation are of great interest for the development and production of biosensors. In particular, biomaterials which can self-assemble on technologically relevant surfaces are of paramount importance. In this context, bacterial surface layer proteins (SLPs) are highly interesting nanomaterials as they fulfil all these requirements. Additionally, the proteinaceous lattice has water-filled pores and shows a thickness of only few nanometres. These features make self-assembled SPLs ideal as an intermediate surface for biosensors utilizing surface-sensitive techniques as read-out system. Moreover, the SLP lattice provides a surface where molecules can be bound in precise spatial distribution and orientation whereby almost no unspecific binding occurs.

To demonstrate the suitability of SLP lattices as smart surfaces, folate was chemically bound to the SLP from Lysinibacillus sphaericus CCM 2177 (SbpA). This construct was subsequently self-assembled on a gold-coated quartz disc. The specific recognition of folate receptors by the SbpA-immobilized folate was investigated by quartz crystal microbalance with dissipation monitoring (QCM-D). Folate receptors are highly expressed on the cell membrane of some cancer cells, such as the human breast adenocarcinoma cell line MCF-7. The developed sensor shows specific binding of MCF-7 cells whereas human liver cancer cells lacking folate receptors on their cell membrane give no shift in the QCM-D signal. This biosensor offers the ability to recognize cells in situ and in real time, and it is even possible to discriminate between different MCF-7 cell viability levels.

The proposed smart surface has several advantages like the nanometer thickness and low unspecific binding properties of the SLP lattice. These features increase the sensitivity and cell capturing efficiency. Hence, this biosensor comprising SbpA-folate biorecognition elements provides a promising strategy for designing smart sensing platforms to diagnose early-stage cancers.

The global spread of pathogenic bacteria is an ongoing issue, where detecting bacterial endotoxins, known as lipopolysaccharides (LPSs), is vital for addressing environmental and healthcare challenges. LPS is responsible for various infections and has recently been implicated in the development of Parkinson's disease. Traditional methods for detecting LPS in research and clinical settings, such as ELISA and LAL assay, have significant drawbacks. These techniques often exhibit low sensitivity and involve complicated, time-consuming processes. Consequently, there is an increasing demand for the development of innovative and cost-effective methods, e.g., electrochemical detection, especially in the fields of environmental science and medicine. This work describes the design of amino-functionalized MIP silica particles for the selective recognition of a specific targeted type of LPS (i.e., LPS from Pseudomonas aeruginosa) from different bacterial strains. The obtained MIP particles were incorporated in a lab-made carbon paste formulation and drop-casted on the working electrode surface of a screen-printed electrode (SPCE). MIP silica particles were synthesized using the Stöber method in the presence of the target molecule LPS via the polycondensation of the functional monomer 3-Aminopropyltriethoxysilane and the structural monomer, tetraethyl orthosilicate, in the basic medium. Herein, two types of cationic surfactants (cetyltrimethylammonium bromide and benzyl trimethyl ammonium chloride) were utilized to stimulate and control the formation of silica particles at a nano level. To ensure the capacity of the MIP particles of recognizing LPS, computational docking was assessed to predict the binding affinity of 3-Aminopropyltriethoxysilane towards LPS. The 1H-NMR results sustained the docking predictions. Other modern techniques, including structural and morphological analyses, were employed to characterize the obtained MIP particles in the raw phase and after their embedment and deposition on the final biosensors. Cyclic voltammetry and differential pulse voltammetry, along with the static and selective adsorption analysis, were submitted to determine the imprinting factor, sensitivity, and selectivity for the targeted LPS. As a result, the obtained amino-functionalized MIP silica particles proved to be an effective and low-cost alternative for biosensor development for the detection of lipopolysaccharide from Pseudomonas aeruginosa.

Gold surface-based acoustic (bio)sensors often face non-specific adsorption issues, creating specificity and sensitivity issues which negatively affect the sensor’s performance. This can be prevented by antifouling coatings, such as 2-(3-trichlorosilylpropyloxy)-ethyltrifluoroacetate (Si-MG-TFA), which is used for silica quartz surfaces used in electromagnetic piezoelectric acoustic devices. Previous research provides evidence that this coating can reduce fouling by a factor of ten, but this could not be successfully replicated on gold surfaces. However, we have found a novel method of successfully applying the Si-MG-TFA coating on gold, with comparable antifouling performance, by using β-mercaptoethanol as an intermediate linker between the gold surface and the Si-MG-TFA. By using the self-assembled monolayer approach to coat gold with β-mercaptoethanol, the gold’s surface becomes hydroxylated, allowing for a proper Si-MG-TFA coating via covalent ether bonds, as seen in silica quartz surfaces. Serum tests using a thickness shear mode acoustic sensor and atomic force microscopy for surface characterization provide evidence of comparable antifouling performance and successful coating of Si-MG-TFA, respectively, on sufficiently flat gold surfaces. Overall, our work shows a potential method of significantly preventing non-specific adsorption for any method involving gold surface-based (bio)sensing.

Based on microelectromechanical (MEMS) technology, this paper presents two electromagnetic vibration energy harvesters. We designed and fabricated two models with different vibration structures. As part of the energy harvester, a permanent magnet is attached to a vibration structure (resonator) made from silicon and a very small wire-wound coil. The total volume of the coil is about 0.9 cm³. Tests and comparisons are performed on two energy harvesters with different resonators.

The maximum load voltage of Model A is 143 mV, and, for Model B, it is 196 mV. Model A generated a maximum load power of 51.52 μW across a 405 Ω load at 347 Hz. Model B generated a maximum load power of 135.35 μW at 311.4 Hz with an acceleration of 0.5 g. Compared to Model A, Model B has a higher output voltage and greater working bandwidth. Under similar experimental conditions, Model B's performance is better than Model A's. Using simple analysis, the results indicated that electromagnetic energy harvesting with Model B provided better results. Furthermore, it shows that a non-linear spring might be able to extend the frequency bandwidth and increase the output voltage.

Stable electrodes are crucial for the creation of high-performance electrochemical microsensors, as they guarantee reliable long-term operation and enhanced sensitivity. Silver electrodes coated with a thin film of silver chloride (AgCl/Ag) form the basis of analytical electrodes due to the excellent charge transfer characteristics and non-polarization of the AgCl material. Also, there is great interest in the integration of nanoparticles with carbon materials due to their unique properties, though challenges related to their hydrophobicity remain. In this study, we modified the silver substrate to create nanostructured reference electrodes and prepared the carbon substrate for the working electrode to improve its compatibility with nanoparticles. The chemical modification process, performed by means of the chlorination of the metal microelectrodes on silicon wafer, included the following steps: degreasing and chemical roughening of the Ag film; washing, drying, and chlorination of the Ag film at room temperature; washing and chemical and thermal stabilization of the nanostructured AgCl film. The enhancement of the hydrophilic properties of nanocrystalline graphite films was achieved by using an acid treatment on the film. The electrodes were structurally characterized, highlighting the formation of the silver chloride film, the degree of purity, and the structural integrity of the carbon material. Microscopic studies allowed us to observed the morphology and roughness of both the modified carbon material and the film, consisting of spherical particles AgCl/Ag with a thickness of about 300 nm. Contact angle analysis was used to investigate the film-wetting properties of the two types of electrodes.

Acknowledgements: This work was supported by a grant from the Ministry of Research, Innovation and Digitization, CNCS-UEFISCDI, project number PN-IV-P2-2.1-TE-2023-0417, within PNCDI IV, and by the Core Program within the National Research Development and Innovation Plan 2022-2027, project no. 2307.

Binary metal oxide nanostructures have received much attention as potential materials in biosensor development, due to their chemical and structural stability, good conductivity, catalytic activity, and high reversible capacity. By combining metal oxides (e.g., TiO₂, In₂O₃, ZnO, and CuO), various versatile materials are obtained, capable of creating sensitive and selective platforms for detecting certain biological or chemical analytes. Among them, In₂O₃-TiO₂ is considered a promising structure for speeding up electron transfer, preventing the recombination of electron–hole pairs, and has superior photocatalytic activity and remarkable photonic activity under visible light illumination.

In this study, the In₂O₃-TiO₂ nanostructures were synthesized by the cation precipitation method, varying the conditions of the synthesis process and thermal treatment at the optimum temperature of 550°C. Different analytical methods were used to evaluate the characteristics regarding the identification of functional groups, determination of the shape and size of the samples, and the purity and crystallinity of the samples. Structural characterization was conducted using FTIR spectroscopy, highlighting bands assigned to In-O and Ti-O bonds; XRD was conducted to find structures of high crystallinity and purity; and EDX provided information at the atomic level. SEM microscopy allowed morphological characterization, finding agglomerated formations of almost-spherical particles of small size. The applicability of the In₂O₃-TiO₂ nanostructures is supported by their hydrophilic behavior and the possibility of percolation, properties determined by contact angle measurements.

Acknowledgments: This work was supported by a grant from the Ministry of Research, Innovation and Digitization, CNCS-UEFISCDI, under project number PN-IV-P2-2.1-TE-2023-0417, within PNCDI IV, and by the Core Program within the National Research Development and Innovation Plan 2022-2027, under project no. 2307.