Search Results (255)

Amperometric glucose biosensors remain indispensable analytical tools in clinical diagnostics due to their sensitivity, simplicity, and suitability for rapid measurements. Herein, an amperometric glucose biosensor based on immobilized glucose oxidase (GOx) and trimetallic nickel–platinum–palladium (NiPtPd) nanoparticles is reported. The NiPtPd nanoparticles deposited on a graphite rod electrode exhibited pronounced peroxidase-like activity and enabled efficient low-potential electrochemical transduction of the enzymatic reaction. The resulting biosensor displayed a linear response toward glucose in the concentration range from 0.04 to 1.58 mM. The limits of detection and quantification were determined to be 17.33 and 52.53 µM, respectively, and the sensitivity was 29.84 µA/mMcm². The developed biosensor demonstrated good analytical precision, with repeatability and reproducibility characterized by relative standard deviations (RSDs) of 4.01 and 9.0%, respectively. High selectivity toward glucose, strong resistance to common electroactive interferents, and satisfactory short-term storage stability (90.78% signal retention after 14 days) were also achieved. Furthermore, preliminary glucose determination in a diluted human serum sample was demonstrated with a recovery of 101.28% and an RSD of 5.27%, indicating the potential applicability of the biosensor for analysis in diluted biological matrices. These findings demonstrate that trimetallic NiPtPd nanoparticles can serve as effective low-potential electrocatalytic transducers in enzyme–nanozyme sensing platforms. Full article

Metal oxide nanomaterials tailored at the nanoscale are opening new avenues for advanced electroanalytical sensing devices with enhanced properties, including improved electrocatalytic activity. In this work, a novel Mn₂Mo₃O₈/MnO-MWCNT nanocomposite was employed to modify a screen-printed carbon electrode, enabling the fabrication of an amperometric sensor for H₂O₂ operating at relatively low applied potential due to the catalytic activity of the nanocomposite. Further functionalization of this nanostructured surface with glucose oxidase allowed the construction of an electrochemical glucose biosensor, where the Mn₂Mo₃O₈/MnO-MWCNT material acted as an efficient electrocatalyst for hydrogen peroxide detection. The H₂O₂ sensor exhibited a linear response from 0.06 mM to 3.00 mM, with a sensitivity of (2.22 ± 0.02) µA mM⁻¹ and a detection limit of 22 µM. The glucose biosensor showed a linear response in the range from 0.10 mM to 18.9 mM glucose, with a sensitivity of (0.345 ± 0.005) µA mM⁻¹, and a detection limit of 29 µM. The biosensor displayed excellent selectivity and high stability and was successfully applied to the determination of glucose in lactose-free skimmed milk. Full article

Water toxicity screening requires sensitive tools to rapidly detect environmental pollutants. While complex analytical methods accurately determine known contaminants, fast screening tests utilizing biological processes, such as photosynthesis, are increasingly being developed to evaluate the toxicity of environmental waters. We describe the isolation of the psychrotolerant Coccomyxa sp. LT4 from Scarisoara Ice Cave (Romania), representing the first report of green algae inhabiting this type of environment, and provide a preliminary assessment of its isolated thylakoids as novel biorecognition components for water toxicity screening. Photosynthetic activity and diuron sensitivity were measured amperometrically and compared with thylakoids from the reference cyanobacterium Synechococcus elongatus PCC 7942. The bioreceptor’s response to various pollutants and water salinities was also investigated. The microalgal thylakoids were more sensitive to diuron than the reference thylakoids, generated stable photocurrents across a broad salinity range and, when lyophilized with sucrose, retained their activity for over two years at −20 °C. Consequently, these thylakoids, isolated from a cold-environment microalga, provide a promising basis for developing biosensors for in situ toxicity screening in low-temperature aquatic ecosystems. Full article

Background/Objectives: In the area of pharmacology and clinical research, it is necessary to use versatile technologies able to quantify last-line antibiotic molecules with high specificity and sensitivity. This article describes the development of two types of immunosensors based on amperometric and surface plasmon resonance (SPR) measurements and their applicability in the measurement/assessment of therapeutic drug monitoring (TDM) of four last-line antibiotics such as vancomycin, colistin, daptomycin and meropenem in human plasma. In this study, ligand immobilization by preconcentration assays, sensor surface regeneration, determination of sensitivity and correlation of plasma sample quantification results by HPLC were considered. Results: In the case of the electrochemical biosensor the IC50 values obtained were 3.49 μg/L for vancomycin (VAN), 5.44 μg/L for colistin (COL), 0.82 μg/L for meropenem (MER) and 5.10 μg/L for daptomycin (DAP). For the SPRi biosensor the LODs achieved were 19 ng/mL for VAN, 9 μg/L for COL, 12 μg/L for MER and 12.3 μg/L for DAP. Finally, both electrochemical biosensor and the SPRi optical biosensor showed that for the four antibiotics the standard deviations were less than 10% with respect to the HPLC results, with ranges for VAN between ~5–6 µg/mL, for COL ~0.2–0.7 µg/mL, for MER ~4.5–5.5 µg/mL and for DAP ~0.09–0.65 µg/mL. Conclusions: These kinds of biosensors provide a precise and sensitive strategy, together with real-time determination, to quantify last-line antibiotics, with working ranges like those shown by robust techniques such as HPLC and great potential for the clinic. Full article

The precise and reliable detection of milk adulterants has garnered increased scientific interest owing to the rising incidence of food fraud. Recent years have witnessed substantial advancements in optical and electrochemical biosensors for the quick, sensitive, and on-site determination of adulterants. This review thoroughly emphasizes recent developments in electrochemical biosensors, encompassing amperometric, voltammetric, impedimetric, and photoelectrochemical sensors, alongside optical biosensors such as colorimetric, fluorometric, and plasmonic systems. Significant focus is directed towards determination of critical milk adulterants, including variations in pH, urea, formaldehyde (FA), melamine (MEL), nitrates (NO₃⁻), nitrites (NO₂⁻), and sulfites (SO₃²⁻). The sensing mechanisms, functional nanomaterials, analytical efficacy, and sample-handling techniques of the described biosensors are critically examined. Moreover, key challenges regarding matrix interference, sensor stability, reproducibility, regulatory validation, and large-scalability are addressed. Ultimately, future directions towards economical, portable, wearable, and Internet of Things (IoT)-integrated biosensors for continuous dairy monitoring are discussed, highlighting the necessity for standardized validation protocols and next-generation technologies in food safety. Full article

In this study, the nonlinear and non-monotonic behavior of amperometric bienzyme biosensors employing an enzymatic trigger reaction is investigated analytically and computationally using a two-compartment model comprising an enzymatic layer and an outer diffusion layer. The trigger enzymatic reaction is coupled with a cyclic electrochemical–enzymatic conversion (CEC) process. The model is formulated as a system of reaction–diffusion equations incorporating nonlinear Michaelis–Menten kinetics and interlayer partitioning effects. Exact steady-state analytical solutions for substrate and product concentrations, as well as for the output current, are obtained for specific cases of first- and zero-order reaction kinetics. At the transition conditions, biosensor performance is further analyzed numerically using the finite difference method. The CEC biosensor exhibits the highest signal gain when the first enzyme has low activity and the second enzyme has high activity; however, under these conditions, the response time is the longest. When the first enzyme possesses a higher substrate affinity (lower Michaelis constant) than the second, the biosensor demonstrates severalfold higher current and gain compared to the reverse configuration under identical diffusion limitations. Furthermore, increasing external mass transport resistance or interfacial partitioning can enhance the apparent signal gain. Full article

Detecting small molecules in biological fluids is essential for diagnosing diseases, monitoring therapy, and studying how the body works. Traditional biosensing methods—such as amperometric, optical, or piezoelectric systems—offer excellent sensitivity but often rely on complex instruments, additional reagents, or time-consuming sample preparation. Potentiometric biosensors, by contrast, provide a simpler, low-power, and label-free alternative that can operate directly in biological environments. This review explores the latest progress in potentiometric biosensing for small-molecule detection, focusing on new solid-contact materials and advanced sensing membranes and compact device designs. We also discuss key challenges, including biofouling, matrix effects, and signal drift, together with promising strategies such as antifouling coatings, nanostructured interfaces, and calibration-free operation. Finally, we highlight how combining potentiometric sensors with artificial intelligence, digital data processing, and flexible electronics is shaping the future of personalized and point-of-care diagnostics. By summarizing recent advances and identifying remaining barriers, this review aims to show why potentiometric biosensors are becoming a powerful and versatile platform for next-generation biomedical analysis. Full article

Alanine aminotransferase (ALT) is a key biomarker of liver function. Compared with conventional assays for ALT detection—which are expensive, time-consuming, labor-intensive, and require experienced personnel—biosensors represent a promising alternative, but it remains unclear which biorecognitive enzymatic configuration offers the best analytical performance for ALT detection. This study presents the development and comparative evaluation of two amperometric biosensors based on oxidase biorecognition elements: pyruvate oxidase (POx) and glutamate oxidase (GlOx). Enzymes were immobilized onto platinum electrodes under optimized conditions using entrapment for POx (pH 7.4, enzyme loading 1.62 U/µL, PVA-SbQ concentration 13.2%) and covalent crosslinking for GlOx (pH 6.5, enzyme loading 2.67%, glutaraldehyde concentration 0.3%). Analytical parameters were systematically assessed, including linear range (1–500 U/L for POx vs. 5–500 U/L for GlOx), limit of detection (1 U/L for both), and sensitivity (0.75 vs. 0.49 nA/min at 100 U/L). The POx-based biosensor demonstrated higher sensitivity and lower detection limits, whereas the GlOx-based biosensor exhibited greater stability in complex solutions and reduced assay costs due to a simpler working solution. Moreover, while the POx-based system is uniquely suited for ALT determination, the GlOx-based sensor can be affected by AST activity in samples but may also be adapted for targeted AST detection. Overall, the study highlights a trade-off between sensitivity, robustness, and versatility in ALT biosensor design, providing guidance for the rational development of clinically relevant devices. Full article

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

A new approach in amperometric enzyme electrodes production based on all-electrochemically assisted procedures will be described. Enzyme (glucose oxidase) immobilization was performed by in situ co-crosslinking of enzyme molecules through electrophoretic protein deposition, assuring enzyme immobilization exclusively onto the transducer surface (Pt electrode). Analogously, the poor selectivity of the transducer was dramatically improved by the electrosynthesis of non-conducting polymers with built-in permselectivity, permitting the formation of a thin permselective film onto the transducer surface, able to reject common interferents usually found in real samples. Since both approaches required a proper and distinct electrochemical perturbation (a pulsed current sequence for electrophoretic protein deposition and cyclic voltammetry for the electrosynthesis of non-conducting polymers), an appropriate coupling of the two all-electrochemical approaches was assured by a thorough study of the likely combinations of the electrosynthesis of permselective polymers with enzyme immobilization by electrophoretic protein deposition and by the use of several electrosynthesized polymers. For each investigated combination and for each polymer, the analytical performances and the rejection capabilities of the resulting biosensor were acquired so to gain information about their sensing abilities eventually in real sample analysis. This study shows that the proper coupling of the two all-electrochemical approaches and the appropriate choice of the electrosynthesized, permselective polymer permits the easy fabrication of novel glucose oxidase biosensors with good analytical performance and low bias in glucose measurement from typical interferent in serum. This novel approach, resembling classical electroplating procedures, is expected to allow all the advantages expected from such procedures like an easy preparation biosensor, a bi-dimensional control of enzyme immobilization and thickness, interferent- and fouling-free transduction of the electrodic sensor and, last but not the least, possibility of miniaturization of the biosensing device. Full article

We develop a modular, wireless, solar- and battery-powered system for detecting chlorpyrifos (Lorsban^TM 2.5% DP) in water using electrochemical impedance spectroscopy (EIS). The system integrates a Raspberry Pi Zero 2W for data processing, Python-based software (version 3.12.2), and a solar charge manager to power all components via a lithium-ion battery and solar panel. A commercial EmStat Pico Module and an amperometric biosensor with acetylcholinesterase (AChE) detect chlorpyrifos. Nine water samples with varying concentrations were tested using a 20 Hz–200 kHz frequency sweep and 15 mV excitation. Bode plots and statistical analyses confirmed statistically significant impedance variation as a function of chlorpyrifos concentration, validating the system as a portable, sensitive, and effective tool for environmental monitoring. Full article

The non-monotonic behavior of amperometric enzyme-based biosensors under uncompetitive and noncompetitive (mixed) substrate inhibition is investigated computationally using a two-compartment model consisting of an enzyme layer and an outer diffusion layer. The model is based on a system of reaction–diffusion equations that includes a nonlinear term associated with non-Michaelis–Menten kinetics of the enzymatic reaction and accounts for the partitioning between layers. In addition to the known effect of substrate inhibition, where the maximum biosensor current differs from the steady-state output, it has been determined that external diffusion limitations can also cause the appearance of a local minimum in the current. At substrate concentrations greater than both the Michaelis–Menten constant and the uncompetitive substrate inhibition constant, and in the presence of external diffusion limitation, the transient response of the biosensor, after immersion in the substrate solution, may follow a five-phase pattern depending on the model parameter values: it starts from zero, reaches a global or local maximum, decreases to a local minimum, increases again, and finally decreases to a steady intermediate value. The biosensor performance is analyzed numerically using the finite difference method. Full article

Amperometric biosensors (ABSs) and enzymatic biofuel cells (BFCs) share several fundamental principles in their functionality, despite serving different primary purposes. Both devices rely on biorecognition, redox reactions, electron transfer (ET), and advanced electrode materials, including innovative nanomaterials (NMs). ABSs and BFCs, utilizing microbial oxidoreductases in combination with electroactive NMs, are both efficient and cost-effective. In the current study, several laboratory prototypes of BFCs have been developed with bioanodes based on yeast flavocytochrome b₂ (Fcb₂) and alcohol oxidase (AO), and a cathode based on fungal laccase. For the first time, BFCs have been developed featuring anodes based on Fcb₂ co-immobilized with redox NMs on a glassy carbon electrode (GCE), and cathode-utilizing laccase combined with gold–cerium–platinum nanoparticles (nAuCePt). The most effective lactate BFC, which contains gold–hexacyanoferrate (AuHCF), exhibited a specific power density of 1.8 µW/cm². A series of BFCs were developed with an AO-containing anode and a laccase/nAuCePt/GCE cathode. The optimal configuration featured a bioanode architecture of AO/nCoPtCu/GCE, achieving a specific power density of 3.2 µW/cm². The constructed BFCs were tested using lactate-containing food product samples as fuels. Full article

Artificial enzymes or nanozymes (NZs) are gaining significant attention in biotechnology due to their stability and cost-effectiveness. NZs can offer several advantages over natural enzymes, such as enhanced stability under harsh conditions, longer shelf life, and reduced production costs. The booming interest in NZs is likely to continue as their potential applications expand. In our previous studies, we reported the “green” synthesis of copper hexacyanoferrate (gCuHCF) using the oxidoreductase flavocytochrome b₂ (Fcb₂). Organic–inorganic micro-nanoparticles were characterized in detail, including their structure, composition, catalytic activity, and electron-mediator properties. An SEM analysis revealed that gCuHCF possesses a flower-like structure well-suited for concentrating and stabilizing Fcb₂. As an effective peroxidase (PO) mimic, gCuHCF has been successfully employed for H₂O₂ detection in amperometric sensors and in several oxidase-based biosensors. In the current study, we demonstrated the uniqueness of gCuHCF that lies in its multifunctionality, serving as a PO mimic, a chemosensor for ammonium ions, a biosensor for L-lactate, and exhibiting perovskite-like properties. This exceptional ability of gCuHCF to enhance fluorescence under blue light irradiation is being reported for the first time. Using gCuHCF as a PO-like NZ, novel oxidase-based sensors were developed, including an optical biosensor for L-arginine analysis and electrochemical biosensors for methanol and glycerol determination. Thus, gCuHCF, synthesized via Fcb₂, presents a promising platform for the development of amperometric and optical biosensors, bioreactors, biofuel cells, solar cells, and other advanced devices. The innovative approach of utilizing biocatalysts for nanoparticle synthesis highlights a groundbreaking direction in materials science and biotechnology. Full article

Electrochemical enzyme biosensors are extensively utilized in clinical analysis and environmental monitoring, yet achieving effective enzyme immobilization while maintaining high activity remains a challenge. In this work, we developed a flow-through enzyme biosensor system using a 3D-printed flow-through electrochemical cell fabricated from commercially available poly (lactic acid). After modification with thiacalixarene-functionalized oligo (lactic acids) (OLAs), the material enabled efficient immobilization of uricase on the inner surface of a replaceable reactor of the cell. Swelling and hydrolytic stability of OLAs in cone, partial cone, and 1,3-alternate conformations were studied, with 1,3-alernate conformation demonstrating superior stability and enzyme immobilization performance. The use of OLAs enhanced immobilization efficiency by over 30% and protected the reactor from swelling, hydrolytic degradation, and enzyme loss. The biosensor was validated for amperometric uric acid determination, with a screen-printed carbon electrode modified with carbon black and Prussian Blue. This modification reduced the cathodic potential for uric acid detection to –0.05 V. The biosensor exhibited a linear detection range of 10 nM to 30 μM with a detection limit of 7 nM, and it performed effectively in artificial urine and synthetic blood plasma. The novel cell design, featuring easy assembly and low-cost replaceable parts, makes this biosensor a promising candidate for routine clinical analysis and other practical applications. Full article