Cover picture provided by Dr. Elena Benito-Peña and Dr. Susana Campuzano. Electroanalysis covers all branches of electroanalytical chemistry, including both fundamental and application papers as well as reviews dealing with analytical voltammetry, potentiometry, new electrochemical sensors and detection schemes, nanoscale electrochemistry, advanced electromaterials, nanobioelectronics, point-of-care diagnostics, wearable sensors, and practical applications.
Circulating microRNAs (miRNAs) in biological fluids are small non-coding RNAs identified as promising biomarkers. They are particularly abundant in milk, a fluid easily accessible without invasive techniques. However, detection methods are currently performed by specialized personnel in centralized laboratories, which greatly lengthen analysis times. This study addresses some challenges by proposing a portable microfluidic electrochemical platform for the detection of miR-30b, a miRNA overexpressed by a previously developed transgenic mouse model. The sensors integrated into the platform were surface-modified with oligonucleotides. Through dual-mode detection by cyclic voltammetry and electrochemical impedance spectroscopy, they exhibit high specificity and sensitivity with a detection range from 10−16 to 10−8 M. Tests on real samples show that the platform is able to distinguish between miR-30b extracted from milk of transgenic mice and that of wild-type mice. These results suggest a strong potential of this sensing platform to carry out early and noninvasive detections. They open the way to precise monitoring of the physiological state of individuals while improving diagnostic options for pathologies in clinical or veterinary settings.
Circulating microRNAs (miRNAs) in biological fluids are small non-coding RNAs identified as promising biomarkers. They are particularly abundant in milk, a fluid easily accessible without invasive techniques. However, detection methods are currently performed by specialized personnel in centralized laboratories, which greatly lengthen analysis times. This study addresses some challenges by proposing a portable microfluidic electrochemical platform for the detection of miR-30b, a miRNA overexpressed by a previously developed transgenic mouse model. The sensors integrated into the platform were surface-modified with oligonucleotides. Through dual-mode detection by cyclic voltammetry and electrochemical impedance spectroscopy, they exhibit high specificity and sensitivity with a detection range from 10−16 to 10−8 M. Tests on real samples show that the platform is able to distinguish between miR-30b extracted from milk of transgenic mice and that of wild-type mice. These results suggest a strong potential of this sensing platform to carry out early and noninvasive detections. They open the way to precise monitoring of the physiological state of individuals while improving diagnostic options for pathologies in clinical or veterinary settings.
The dielectric properties of biological culture media play a critical role in accurately modeling and optimizing in vitro electrical stimulation systems. This study presents the dielectric characterization of a skeletal muscle cell differentiation medium using electrochemical impedance spectroscopy (EIS) with a custom-designed three-electrode stainless steel setup. Impedance measurements were conducted across a frequency range of 0.01 Hz to 10 kHz and fitted to a Randles equivalent circuit, yielding excellent agreement with experimental data (χ2 = 0.0833). Analysis focused on the frequency range of interest for stimulation applications (1–100 Hz), where results demonstrated marked frequency-dependent behavior in conductivity (ranging from 0.07 to 4.7 S/m) and relative permittivity (ε′ exceeding 2 × 109 at 1 Hz), indicative of α-dispersion and interfacial polarization effects. The medium's high ionic conductivity and dielectric response were comparable to those observed in standard saline and physiological solutions, reinforcing its suitability for bioelectrical applications. While the use of stainless-steel electrodes facilitated low-cost fabrication and stable measurements, minor variability in the impedance signal may reflect surface redox activity. Future work will involve integrating live-cell systems, refining electrode materials, and extending equivalent circuit models to capture diffusion-related phenomena for real-time monitoring in organ-on-a-chip platforms.
The dielectric properties of biological culture media play a critical role in accurately modeling and optimizing in vitro electrical stimulation systems. This study presents the dielectric characterization of a skeletal muscle cell differentiation medium using electrochemical impedance spectroscopy (EIS) with a custom-designed three-electrode stainless steel setup. Impedance measurements were conducted across a frequency range of 0.01 Hz to 10 kHz and fitted to a Randles equivalent circuit, yielding excellent agreement with experimental data (χ2 = 0.0833). Analysis focused on the frequency range of interest for stimulation applications (1–100 Hz), where results demonstrated marked frequency-dependent behavior in conductivity (ranging from 0.07 to 4.7 S/m) and relative permittivity (ε′ exceeding 2 × 109 at 1 Hz), indicative of α-dispersion and interfacial polarization effects. The medium's high ionic conductivity and dielectric response were comparable to those observed in standard saline and physiological solutions, reinforcing its suitability for bioelectrical applications. While the use of stainless-steel electrodes facilitated low-cost fabrication and stable measurements, minor variability in the impedance signal may reflect surface redox activity. Future work will involve integrating live-cell systems, refining electrode materials, and extending equivalent circuit models to capture diffusion-related phenomena for real-time monitoring in organ-on-a-chip platforms.
17β-estradiol (E2) is the main female sex hormone widely found in pharmaceutics indicated for contraception and replacement therapy. Because this hormone is secreted by the body and contaminates the aquatic environment, it is considered an important organic pollutant to monitor due to its action on the human body as an endocrine disruptor. Therefore, the development of rapid, sensitive, precise, and portable methods is relevant for its quantification “in situ” in different matrices. In this context we propose the determination of E2 using a fast low-cost system composed of a graphite-acrylonitrile butadiene styrene (coated on 3D-printed ABS substrate) electrode assembled in a novel user-friendly 3D-printed batch injection analysis system with amperometric detection (BIA-AD). The best electrochemical behavior was obtained in 0.04 mol L−1 Britton-Robinson buffer (pH 3.0) in which an irreversible oxidation was noted at +0.85 V. Under the optimized conditions of BIA-AD (detection potential = +1.1 V, injection volume = 100 µL, dispensing rate = 142 µL s−1), a sensitivity of 0.154 µA µmol−1 L, a linear range of 0.1–7.0 µmol L−1, an experimental LOD of 0.1 µmol L−1, and an analytical frequency of 240 injections per hour were obtained. Good precision was reached for sequential injections of E2 at three concentration levels (8.6%, 3.2%, and 5.0% for 0.5, 3.0, and 6.0 µmol L−1, respectively). Moreover, good interelectrode reproducibility was reached (RSD = 5.5%; n = 4), which confirms good manufacturing efficiency. The method was applied for the determination of E2 in pharmaceutical sample and river water. The results found in a pharmaceutical sample were statistically similar to the obtained by a UV–vis spectrophotometric method. The value found in river water was below the experimental LOD. Thus, this sample was fortified with different concentrations of E2, obtaining recoveries between 100% and 116%, which confirms the good accuracy of the method. The proposed BIA-AD is promising for the fast on-site determination of E2 in different matrices.
Initially, a printed electrode was fabricated on a polyethylene terephthalate (PET) substrate using an ink based on graphite, carbon black, and nail polish. The working electrode was then modified with gold nanoparticles, followed by the sequential immobilization of antibodies specific to KLK2, bovine serum albumin (BSA), and KLK2 antigen as the target molecule. Several parameters were optimized to achieve the best performance of the immunosensor: antibody incubation time (40 min), BSA incubation time and concentration (30 min, 1.50 mg mL−1), antigen incubation time (60 min), supporting electrolyte pH (7.50), and supporting electrolyte concentration (0.01 mol L−1). After each modification step, the sensor was thoroughly washed with a 0.10 mol L−1 phosphate buffer (pH 7.00) and dried using a nitrogen stream. Reproducibility and interference studies demonstrated that the sensor exhibited good reproducibility and specificity for KLK2 detection. Subsequently, the sensor was applied to determine KLK2 in synthetic serum samples, achieving excellent recovery values ranging from 95.6% to 102%. These results suggest that the screen-printed electrode (SPE)/AuNP/anti-KLK2/BSA sensor holds promise for analyzing KLK2 in real serum samples.
Initially, a printed electrode was fabricated on a polyethylene terephthalate (PET) substrate using an ink based on graphite, carbon black, and nail polish. The working electrode was then modified with gold nanoparticles, followed by the sequential immobilization of antibodies specific to KLK2, bovine serum albumin (BSA), and KLK2 antigen as the target molecule. Several parameters were optimized to achieve the best performance of the immunosensor: antibody incubation time (40 min), BSA incubation time and concentration (30 min, 1.50 mg mL−1), antigen incubation time (60 min), supporting electrolyte pH (7.50), and supporting electrolyte concentration (0.01 mol L−1). After each modification step, the sensor was thoroughly washed with a 0.10 mol L−1 phosphate buffer (pH 7.00) and dried using a nitrogen stream. Reproducibility and interference studies demonstrated that the sensor exhibited good reproducibility and specificity for KLK2 detection. Subsequently, the sensor was applied to determine KLK2 in synthetic serum samples, achieving excellent recovery values ranging from 95.6% to 102%. These results suggest that the screen-printed electrode (SPE)/AuNP/anti-KLK2/BSA sensor holds promise for analyzing KLK2 in real serum samples.
17β-estradiol (E2) is the main female sex hormone widely found in pharmaceutics indicated for contraception and replacement therapy. Because this hormone is secreted by the body and contaminates the aquatic environment, it is considered an important organic pollutant to monitor due to its action on the human body as an endocrine disruptor. Therefore, the development of rapid, sensitive, precise, and portable methods is relevant for its quantification “in situ” in different matrices. In this context we propose the determination of E2 using a fast low-cost system composed of a graphite-acrylonitrile butadiene styrene (coated on 3D-printed ABS substrate) electrode assembled in a novel user-friendly 3D-printed batch injection analysis system with amperometric detection (BIA-AD). The best electrochemical behavior was obtained in 0.04 mol L−1 Britton-Robinson buffer (pH 3.0) in which an irreversible oxidation was noted at +0.85 V. Under the optimized conditions of BIA-AD (detection potential = +1.1 V, injection volume = 100 µL, dispensing rate = 142 µL s−1), a sensitivity of 0.154 µA µmol−1 L, a linear range of 0.1–7.0 µmol L−1, an experimental LOD of 0.1 µmol L−1, and an analytical frequency of 240 injections per hour were obtained. Good precision was reached for sequential injections of E2 at three concentration levels (8.6%, 3.2%, and 5.0% for 0.5, 3.0, and 6.0 µmol L−1, respectively). Moreover, good interelectrode reproducibility was reached (RSD = 5.5%; n = 4), which confirms good manufacturing efficiency. The method was applied for the determination of E2 in pharmaceutical sample and river water. The results found in a pharmaceutical sample were statistically similar to the obtained by a UV–vis spectrophotometric method. The value found in river water was below the experimental LOD. Thus, this sample was fortified with different concentrations of E2, obtaining recoveries between 100% and 116%, which confirms the good accuracy of the method. The proposed BIA-AD is promising for the fast on-site determination of E2 in different matrices.
Considering the importance of antioxidants in food and medical industries, the accurate evaluation of their reactivity is of capital importance. In this work, a new electrochemical approach based on the cupric reducing antioxidant capacity (CUPRAC) is proposed for the accurate evaluation of antioxidant properties. The electrochemical behavior of the complex ([Cu(Nc)2]2+) obtained from the reaction between copper(II) and neocuproine (Nc) used in the CUPRAC method was studied to identify the ideal Cu/Nc molar ratio. The Cu/Nc ratio of 4/3, usually used in the CUPRAC method, was not suitable because of the partial reaction of Nc with Cu(II). A more appropriate Cu/Nc molar ratio of 1/7 was experimentally determined by voltammetry at a stationary or rotating electrode. With this molar ratio, [Cu(Nc)2]2+ presents a fast and monoelectronic system controlled by diffusion. This allowed antioxidant properties determination by chronoamperometry, by following the [Cu(Nc)2]2+ reduction current as a function of the tested antioxidant. Ascorbic acid and Trolox used in this study as model antioxidants showed inhibition concentrations values (IC50) very close to the expected theoretical values. These results are proof that the developed electrochemical method is accurate and allows a fast and efficient evaluation of antioxidant properties while minimizing interferences encountered using spectrophotometric methods.
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