Biological Interference Research Articles

Scalp surface Laplacian potential monitoring system based on novel hydrogel active tri-polar concentric ring electrodes

Electroencephalography is valued in brain research for its high temporal resolution and user-friendly nature. However, limitations in spatial resolution and susceptibility to biological artifacts restrict its broader application. The surface Laplacian potential obtained through tri-polar concentric ring electrodes offers a solution by mitigating biological artifact interference and enhancing spatial resolution while preserving essential information. In this study, an active tri-polar concentric ring electrode based on conductive hydrogel and a 3-lead surface Laplacian potential monitoring system designed for use with the electrode were proposed. The part of the electrode that came into contact with the human body was the hydrogel with high electrical conductivity. The contact surface curvature was designed based on the real forehead curvature of 22 subjects, resulting in a normalized electrode-skin contact impedance of 30.95±16.76KΩ*cm2 at 10 Hz, which was lower than commercial disposable wet electrodes and remained stable over a 10-hour period of long-term wear. And the electrode still exhibited excellent performance after being left for 20 days. Additionally, the internal noise of the system was about 1.9μV, which was comparable to that of the FDA-approved equipment. The signal analysis results demonstrated that the surface Laplacian potential collected by the proposed electrode and system had better signal-to-noise ratio and spatial resolution, and had a good suppression effect on biological artifacts.

Red-emitting carbon dots for fluorescent and smartphone-assisted dual-mode detection of Cu(II), Hg(II), and Fe(III) and investigation of the sensing mechanism

Red-emitting carbon dots (R-CDs) have triggered ever-increasing interest in biochemical sensing due to their deep tissue penetration and minimal biological auto-fluorescence interference. Herein, dual-emitting intrinsic R-CDs are fabricated and well-characterized. R-CDs display ratiometric and colorimetric sensing properties for heavy metal ions (HMIs, Cu2+, Hg2+, and Fe3+), with the corresponding detection limits of 24.5, 74.2, and 170 nM, respectively. Additionally, smartphone imaging colorimetry based on red-green-blue (RGB) value variations is employed to achieve real-time and on-site detection of these HMIs. Crucially, discrimination of these HMIs is facilitated by principal component analysis. Furthermore, R-CDs demonstrate effective optical sensing of these HMIs in tap/lake water and human urine with satisfactory recoveries (95.82–104.8 %). The underlying mechanism of optical sensing, which involves metal ion-triggered aggregation-induced quenching, is elucidated by spectroscopic, morphological analysis, and quantum mechanical calculations. This work presents a feasible real-time approach for the fluorescent and smartphone-assisted dual-mode detection of HMIs.

Determination of drugs of abuse and metabolites in plasma microsamples by LC-MS/MS after microQuEChERS extraction.

Aim: Identifying drugs of abuse and their metabolites in plasma is vital in both forensic and clinical toxicology. While the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method offers an efficient approach to sample preparation, its application is complex due to the wide-ranging properties of target analytes and the challenges posed by biological matrix interferences. This study aims to develop a microQuEChERS approach for the quantification of 14 drugs of abuse and metabolites utilizing minimal sample and solvent volumes.Methods: The microQuEChERS method involved using 10μl plasma samples, 25mg of a salt mixture and 150μl of acetonitrile. Extracts were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with a 7.5min run. The assay was validated according to bioanalytical guidelines.Results: The accuracy was 96.8-112.4%. The within-assay precision was within 2.0-8.9% and the between-assay precision was within 3.2-8.2%. Matrix effects were found to range from -5.7 to 13.5%. The extraction yield was higher than 74.7%.Conclusion: This study described a microQuEChERS sample preparation approach for determining drugs of abuse and metabolites using plasma microsamples and LC-MS/MS. The approach is efficient, environmentally friendly and suitable for scenarios with limited amounts of biological samples.

Recent developments in intranasal drug delivery of nanomedicines for the treatment of neuropsychiatric disorders.

Neuropsychiatric disorders are multifaceted syndromes with confounding neurological explanations. It includes anxiety, depression, autism spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, Tourette's syndrome, delirium, dementia, vascular cognitive impairment, and apathy etc. Globally, these disorders occupy 15% of all diseases. As per the WHO, India has one of the largest populations of people with mental illnesses worldwide. The blood-brain barrier (BBB) makes it extremely difficult to distribute medicine to target cells in the brain tissues. However, it is possible through novel advancements in nanotechnology, molecular biology, and neurosciences. One such cutting-edge delivery method, nose-to-brain (N2B) drug delivery using nanoformulation (NF), overcomes traditional drug formulation and delivery limitations. Later offers more controlled drug release, better bioavailability, improved patient acceptance, reduced biological interference, and circumvention of BBB. When medicines are delivered via the intranasal (IN) route, they enter the nasal cavity and go to the brain via connections between the olfactory and trigeminal nerves and the nasal mucosa in N2B. Delivering phytochemical, bioactive and synthetic NF is being investigated with the N2B delivery strategy. The mucociliary clearance, enzyme degradation, and drug translocations by efflux mechanisms are significant issues associated with N2B delivery. This review article discusses the types of neuropsychiatric disorders and their treatment with plant-derived as well as synthetic drug-loaded NFs administered via the IN-delivery system. In conclusion, this review provided a comprehensive and critical overview of the IN applicability of plant-derived NFs for psychiatric disorders.

Nanostructured electrochemical platform for sensitive detection of melatonin in human serum and tablets

Melatonin (MT) is a crucial hormone for biological rhythms that influences sleep-wake cycles. The therapeutic value of MT in neurological disorders highlights the need for precise detection. However, challenges like low concentrations in biological samples and complex matrix interferences persist, necessitating rapid and precise analytical techniques. This study presents the novelty of designing a novel sensor that combines a molecularly imprinted polymer with polytoluidine blue O (PTBO) and multi-walled carbon nanotubes on a glassy carbon electrode for MT detection and the study of the interaction between MT and the proposed sensor using density functional theory (DFT). DFT showed that MT has a high nucleophilic character and low electrophilicity compared to TBO, which is a strong electrophile. This supports electron transfer from MT to TBO/PTBO, as indicated by the electronic chemical potentials and molecular electrostatic potentials. Scanning electron microscopy was used to see the morphology. Electrochemical measurements using differential pulse voltammetry demonstrated enhanced sensitivity and selectivity. Under optimized conditions, the sensor exhibited a linear response ranging from 1 to 1000 µM with a limit of detection and limit of quantification of 0.027 µM and 0.092 µM respectively. The performance of the sensor was evaluated in pharmaceutical tablets and human serum. Validation experiments confirmed the reliability of the sensor, with recovery rates of 97.5 % for serum and 98.0 % for pharmaceutical tablets, alongside low relative standard deviations indicating good precision. Interference studies showed minimal effects from coexisting substances, highlighting the selectivity of the proposed sensor. Comparative analysis with existing sensors showed superior performance.

Exploring the Effects of Chirality of 5-methyl-5-[4-(4-oxo-3H-quinazolin-2-yl) phenyl]imidazolidine-2,4-dione and its Derivatives on the Oncological Target Tankyrase 2. Atomistic Insights.

Tankyrases (TNKS) are homomultimers existing in two forms, viz. TNKS1 and TNKS2. TNKS2 plays a pivotal role in carcinogenesis by activating the Wnt//β-catenin pathway. TNKS2 has been identified as a suitable target in oncology due to its crucial role in mediating tumour progression. The discovery of 5-methyl-5-[4-(4-oxo-3H-quinazolin-2-yl) phenyl] imidazolidine-2,4-dione, a hydantoin phenylquinazolinone derivative which exists as a racemic mixture and in its pure enantiomer forms, has reportedly exhibited inhibitory potency towards TNKS2. However, the molecular events surrounding its chirality towards TNKS2 remain unresolved. Herein, we employed in silico methods such as molecular dynamics simulation coupled with binding free energy estimations to explore the mechanistic activity of the racemic inhibitor and its enantiomer forms on TNK2 at a molecular level Results: Favourable binding free energies were noted for all three ligands propelled by electrostatic and van der Waals forces. The positive enantiomer demonstrated the highest total binding free energy (-38.15 kcal/mol), exhibiting a more potent binding affinity to TNKS2. Amino acids PHE1035, ALA1038, and HIS1048; PHE1035, HIS1048 and ILE1039; and TYR1060, SER1033 and ILE1059 were identified as key drivers of TNKS2 inhibition for all three inhibitors, characterized by the contribution of highest residual energies and the formation of crucial high-affinity interactions with the bound inhibitors. Further assessment of chirality by the inhibitors revealed a stabilizing effect of the complex systems of all three inhibitors on the TNKS2 structure. Concerning flexibility and mobility, the racemic inhibitor and negative enantiomer revealed a more rigid structure when bound to TNKS2, which could potentiate biological activity interference. The positive enantiomer, however, displayed much more elasticity and flexibility when bound to TNKS2. Overall, 5-methyl-5-[4-(4-oxo-3H-quinazolin-2-yl) phenyl] imidazolidine-2,4-dione and its derivatives showed their inhibitory prowess when bound to the TNKS2 target via in silico assessment. Thus, results from this study offer insight into chirality and the possibility of adjustments of the enantiomer ratio to promote greater inhibitory results. These results could also offer insight into lead optimization to enhance inhibitory effects.

Bio-responsive polymers for dual 31P/19F-magnetic resonance to detect reactive oxygen species in vivo

Biocompatible metal-free agents are emerging as a promising alternative to commercial magnetic resonance (MR) contrast agents, but there is an additional need for novel probes with enhanced responsiveness in preclinical MR testing to effectively target diverse pathological conditions. To address this, we develop hydrophilic phospho-/fluoropolymers as dual MR probes. Incorporating thiophosphoester groups (P = S) into the polymer structure produces a distinct chemical shift (~59 ppm) in phosphorus MR (31P-MR), reducing biological signals interference. Reactive oxygen species (ROS) oxidize the P = S groups, causing a detectable shift in 31P-MR, enabling precise localization of ROS, abundant in inflammation and cancer. To enhance this capability, bioinert trifluoromethyl groups (CF3) are added, creating a “hotspot” for fluorine MR (19F-MR), aiding in vivo localization. Both in vitro and in vivo testing demonstrate the probe’s high specificity and responsiveness, underscoring its potential as a sensitive ROS sensor and dual MR-traceable tool in cancer research.

Berberine alleviates ulcerative colitis by inhibiting inflammation through targeting IRGM1

BackgroundBerberine (BBR), the main active component of Coptis chinensis Franch., has a variety of pharmacological effects, notably anti-inflammatory, which make it a potential treatment for ulcerative colitis (UC). Nevertheless, the specific target and the mode of action of BBR against UC are still unclear. PurposeHere, we aim to identify BBR's anti-inflammatory target and its mode of action in UC treatment. MethodsThe therapeutic effects of BBR and Coptis chinensis Franch. extract were first assessed in UC mice. Then, stable isotope labeling using amino acids in cell culture-activity-based protein profiling (SILAC-ABPP) was applied to identify the anti-inflammatory target proteins of BBR in an inflammation model of RAW264.7 cells stimulated by LPS. Molecular docking, drug affinity responsive target stability (DARTS), molecular dynamics simulation, cellular thermal shift assay (CETSA), and biological layer interference (BLI) measurement were employed to study the interaction between BBR and its targets. Lentiviral transfection was used to knock down the target protein and investigate BBR's anti-inflammatory mechanism. ResultsBBR and Coptis chinensis Franch. extracts both significantly alleviated UC in mice. SILAC-ABPP identified IRGM1 as BBR's anti-inflammatory target, with its overexpression reduced by BBR treatment in both RAW264.7 cell inflammation models stimulated by LPS and UC mice. BBR significantly reduced inflammatory cytokines in LPS-induced RAW264.7 cells by blocking the PI3K/AKT/mTOR pathway. Knockdown of IRGM1 weakened BBR's effects on cytokine expression and pathway regulation. ConclusionFor the first time, IRGM1 was identified as the direct anti-inflammatory target of BBR. BBR has the potential to inhibit IRGM1 expression in vitro as well as in vivo. The molecular mechanism of BBR's anti-inflammatory activity was inhibiting the PI3K/AKT/mTOR pathway by targeting IRGM1.

Highly sensitive electrochemical sensor for glutathione detection using zinc oxide quantum dots anchored on reduced graphene oxide

This work presents a highly sensitive and selective electrochemical sensor for glutathione (GSH) detection using a glassy carbon (GC) electrode modified with zinc oxide quantum dots-reduced graphene oxide nanocomposites (ZnO QDs-rGO NCs). The ZnO QDs (diameters about ∼2 to 8 nm) were synthesized and successfully anchored onto the surface of reduced graphene oxide (rGO). The resulting nanocomposites were then characterized using various spectroscopic and microscopic techniques. The wurtzite crystal structure of ZnO and anchored onto the rGO surface were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synergistic interaction between ZnO QDs with rGO provides a large surface area, high conductivity, and efficient transfer of electrons, resulting in improved electrocatalytic activity for GSH oxidation. The ZnO QDs-rGO/GC electrode exhibits exceptional performance with a wide linear range (0.01–10 μM), high sensitivity (3.66 μAμM−1), and excellent selectivity for GSH. The sensor demonstrates good analytical stability, characterized by high reproducibility (%RSD = 2.90%) and repeatability (%RSD = 1.49%), and maintains its performance in the presence of common biological interferences. The applicability of the sensor was validated through successful GSH detection in complex matrices like human blood and pharmaceutical capsules, achieving recovery rates of 98.1-102.0% with excellent reliability.

A 3D-Printed Do-It-Yourself ELISA Plate Reader as a Biosensor Tested on TNFα Assay.

Simple analytical devices suitable for the analysis of various biochemical and immunechemical markers are highly desirable and can provide laboratory diagnoses outside standard hospitals. This study focuses on constructing an easily reproducible do-it-yourself ELISA plate reader biosensor device, assembled from generally available and inexpensive parts. The colorimetric biosensor was based on standard 96-well microplates, 3D-printed parts, and a smartphone camera as a detector was utilized here as a tool to replace the ELISA method, and its function was illustrated in the assay of TNFα as a model immunochemical marker. The assay provided a limit of detection of 19 pg/mL when the B channel of the RGB color model was used for calibration. The assay was well correlated with the ELISA method, and no significant matrix effect was observed for standard biological samples or interference of proteins expected in a sample. The results of this study will inform the development of simple analytical devices easily reproducible by 3D printing and found on generally available electronics.

Applicability of Salting-out Liquid-liquid Extraction for New Fluorimetric Quantification of Omadacycline in Pharmaceutical Formulations and Biological Samples

Objective: A detectable innovative fluorimetric method was used to determine OMC in human plasma matrices, pharmaceutical tablets, and vials with high recovery rates and without biological interference. Methods: The fluorimetric technique was used based on the interaction between 4-chloro7-nitrobenzofurazan (NBD-Cl) with a (2-ry amine group) in OMC with pH 8.0, which generates a fluorescent compound measured at 530 nm (exci 470 nm) following a 10-minute heating step at 80 oC. The plasma and milk samples were treated with ammonium sulfate as a salting-out procedure. Results: Omadacycline (OMC) was successfully determined in pharmaceuticals, plasma, and milk samples with a linear range from 60.0 to 700.0 ng mL-1, with the lower limit of detection (LOD 5.18 ng mL-1) and limit of quantitation (LOQ 15.72 ng mL-1). Conclusion: This simple, reliable, and detectable fluorimetric method was successfully developed to determine omadacycline in pharmaceutical tablets, plasma samples, and milk with high recovery rates.

Dual-driven AND molecular logic gates for label-free and sensitive ratiometric fluorescence sensing and inhibitors screening

Due to the complexity of regulatory networks of disease-related biomarkers, developing simple, sensitive, and accurate methods has remained challenging for precise diagnosis. Herein, an “AND” logic gates DNA molecular machine (LGDM) was constructed, which was powered by the catalytic hairpin assembly (CHA). It was coupled with dual-emission CdTe quantum dots (QDs)-based cation exchange reaction (CER) for label-free, sensitive, and ratiometric fluorescence detection of APE1 and miRNA biomarkers. Benefiting from synergistic signal amplification strategies and a ratiometric fluorometric output mode, this LGDM enables accurate logic computing with robust and significant output signals from weak inputs. It offers improved sensitivity and selectivity even in cell extracts. Using dual-emission spectra CdTe QDs, with a ratiometric signal output mode, ensured good stability and effectively prevented false-positive signals from intrinsic biological interferences compared to the approach relying on a single signal output mode, which enabled the LGDM to achieve rapid, efficient, and accurate natural drug screening against APE1 inhibitors in vitro and cells. The developed method provides impetus to streamline research related to miRNA and APE1, offering significant promise for widespread application in drug development and clinical analysis.

Boron carbide decorated tungsten disulfide nanosheet composite for determination of chloramphenicol in food and pharmaceutical samples

Making the nanocomposites of metal oxides or metal sulfides with carbon source materials has a huge impact on the electrochemical determination of toxic chemicals. To determine the adverse side effects of the antibiotics, electrochemical sensors have been used as they can peek into the sensitivity of the drug sample. This work has done the sensitive amperometric evaluation of a chloramphenicol antibiotic by modifying the electrode of tungsten disulfide decorated boron carbide. Here, tungsten disulfide (WS2) nanosheets and boron carbide (B4C) materials were synthesized by conventional methods which give a good amount of yield. The composite was prepared by the green and cost-effective sonochemical approach with good morphology. The conductivity of the nanocomposite and the response to chloramphenicol were determined by cyclic voltammetry. The sensitivity, limit of detection (LOD), and the linear range were observed by the highly sensitive amperometric technique. From the amperometric analysis, the prepared nanocomposite shows nominal LOD as a 17.4 nM, a broad linear range (0.025–1134.6 µM), and good sensitivity of 1.52 µA µM−1 cm−2. Practicability of the modified sensor was studied in food and pharmaceutical samples with adequate recovery performances. Moreover, the modified electrode shows good stability, repeatability, reproducibility, and anti-interfering properties against the array of food and biological interferences.

Morphologically tailored NiMn2O4nanocubic material for high energy-power density asymmetric supercapacitor and non-enzymatic H2O2 sensing

Developing an advanced material for energy storage and sensors is considered a key solution to meet future energy demands and economic challenges. The inverse spinel-structured NiMn2O4 emerges as a promising electrode material for next-gen energy storage due to its notable power capability, high energy density, and excellent cyclic stability. Nanostructuring enhances features not achievable in bulk materials, with a mixed morphology of nano-cubic and nanoflakes optimizing surface-to-volume ratio for effective use in energy storage devices. The addition of PVP as a surfactant, transforms the diffusion-controlled behavior to a capacitive mechanism, enhancing energy density and cyclic stability. Electrodes exhibit a specific capacitance of 816 F g−1 at 1 A g−1 and stable cyclic behavior over 5000 cycles in 1 M KOH. The constructed ASC device shows 96% cyclic stability over 10,000 cycles, maintaining an energy density of 8.8 Wh kg−1 at 6400 W kg−1 and reaching a maximum of 36.55 Wh kg−1 at 400 W kg−1. Electronic structural characteristics explained through density functional theory (DFT) contribute insights. Furthermore, the non-enzymatic NiMn4/GCE H2O2 sensor demonstrates high sensitivity, a low detection limit, and remarkable selectivity against various biological interferences across a broad concentration range.

Advancing Nonsmall Cell Lung Cancer Diagnosis Accuracy via Dual Detection Fluorescent Nanoprobes.

Among the primary threats to human health worldwide, nonsmall cell lung cancer (NSCLC) remains a significant factor and is a leading cause of cancer-related deaths. Due to subtle early symptoms, NSCLC patients are diagnosed at advanced stages, resulting in low survival rates. Herein, novel Au-Se bond nanoprobes (NPs) designed for the specific detection of Calpain-2 (CAPN2) and Human Neutrophil Elastase (HNE), pivotal biomarkers in NSCLC, were developed. The NPs demonstrated exceptional specificity and sensitivity toward CAPN2 and HNE, enabling dual-color fluorescence imaging to distinguish between NSCLC cells and normal lung cells effectively. The NPs' performance was consistent across a wide pH range (6.2 to 8.0), and it exhibited remarkable resistance to biological thiol interference, indicating its robustness in complex physiological environments. These findings suggest the nanoprobe is a promising tool for early NSCLC diagnosis, offering a novel approach for enhancing the accuracy of cancer detection.

Background-Free SERS Nanosensor for Endogenous Hydrogen Sulfide Detection Based on Prussian Blue-Coated Gold Nanobipyramids.

Surface-enhanced Raman scattering (SERS) has great potential in biological analysis due to its specificity, sensitivity, and non-invasive nature. However, effectively extracting Raman information and avoiding spectral overlapping from biological background interference remain major challenges. In this study, we developed a background-free SERS nanosensor consisting of gold nanobipyramids (Au NBPs) core-Prussian blue (PB) shell (Au NBPs@PB), for endogenous H2S detection. The PB shell degraded quickly upon contact with endogenous H2S, generating a unique Raman signal response in the Raman silent region (1800-2800 cm-1). By taking advantage of the high SERS-activity of Au NBPs and H2S-triggered spectral changes of PB, these SERS nanosensors effectively minimize potential biological interferences. The nanosensor exhibits a detection range of 2.0 μM to 250 μM and a limit of detection (LOD) of 0.34 μM, with good reproducibility and minimal interference. We successfully applied this background-free SERS platform to monitor endogenous H2S concentrations in human serum samples with satisfied results.

High-Order Temporal Convolutional Network for Improving Classification Performance of SSVEP-EEG

Background and objectiveSteady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs) aim to detect target frequencies corresponding to specific commands in electroencephalographic (EEG) signals by classification algorithms to achieve the desired control. However, SSVEP signals suffer from low signal-to-noise ratio and large differences in brain activity. Moreover, the existing CNN models have small receptive fields, which make it difficult to receive large range of feature information and limit the effectiveness of classification algorithms. MethodsTo this end, we proposed a high-order temporal convolutional neural network (HOT-CNN) model for enhancing the performance of SSVEP target recognition. Specifically, the SSVEP-EEG signals was divided into equal-length time segments and a time-slice attention module was designed to capture the correlation between time slices. The module improves the local characterization of signals and reduces biological noise interference by automatically assigning high weights to locally relevant temporal sampling cues and lower weights to other temporal cues. Moreover, for global features, a temporal convolutional network module was designed to increases the receptive field of the network and to extract more comprehensive time domain features by using dilated causal convolution. Finally, the fusion and analysis of local and global features are achieved by designing a feature fusion and classification module to accomplish accurate classification of SSVEP signals. ResultsOur method was evaluated on large publicly available datasets containing 35 subjects and 40 categories. Experimental results indicated that HOT-CNN achieved encouraging performance compared with other advanced methods: the highest information transfer rate of 241.01bits/min was obtained using 0.5s stimuli, and the highest average accuracy of 96.39% was obtained using 1.0s stimuli. ConclusionsThe method effectively reinforced the global and local time-domain information and improved the classification performance of SSVEP, which has wide application prospects.

Fabrication and characterization of a novel strontium oxide-polythiophene core–shell nanocomposite for in-vitro electrochemical detection of antiplatelet cilostazol drug in formulation and human plasma

The green synthesis of metal or metal oxide nanoparticles utilizing plants is a novel promising approach in bio-nanotechnology. The strontium oxide nanoparticles (SrO NPs) were synthesized for the first time utilizing a plant extract of Green cardamom (Elettaria cardamomum) as a reducing and stabilizing agent. The strontium oxide polythiophene (SrO@PTh) nanocomposite was then prepared by in-situ oxidative polymerization of thiophene on the surface of SrO NPs using anhydrous FeCl3 as an oxidant. FTIR spectrum indicates the coordination of SrO NPs with the binding sites along PTh backbone. TEM analysis resulted in an average particles size of (25 – 50 nm) for SrO NPs and core–shell nanostructure of its composite (SrO@PTh CS) with shell thickness of (20–90 nm). The XRD analysis indicates a crystalline cubic structure of SrO NPs with particles size of ≈ 45 nm in average and interplanar space of (0.24 ∼ 0.36 nm). The crystallinity was relatively diminished to some extent for SrO@PTh CS which exhibits a particle size of about 85 nm and interplanar space of (0.13 ∼ 0.23 nm). A smart and novel electrochemical graphite paste sensor (GPS), based on SrO@PTh CS nanocomposite, has been fabricated for the ultrasensitive in-vitro detection of antiplatelet drug cilostazol. SrO@PTh CS nanocomposite-based square-wave voltammetry biosensor exhibited the lowest limits of detection of 1.99 × 10−10 and 9.83 × 10−10 M for cilostazol drug determination in bulk and human plasma samples, respectively compared to all the reported methods. It exhibited also good reproducibility, repeatability, long-term stability and was free from biological interference effects.

Magnetic Fields in Multiconductor Systems with Harmonic Currents.

Electric and magnetic fields produced by power transmision and distribution lines are receiving strong interest due to its biological effects and interference disturbances upon electronic and computer equipment. The presence of currents with harmonic contents, generated by variable speed drives and other power electronic devices worsen the problem. The accurate evaluation of the magnteic field in the vicinity of the line must take into account the non uniform distribution of currents inside the conductors, due to skin and proximity effects. The spatial distribution of induction lines down to the ground level must be plotted, to evaluate its effects in the body of a person situated below the line This paper proposes a two step procedure for solving the problem: first, the non uniform distribution of the currents in the conductors is calculated, applying Maxwell laws. Second, the distribution of the field is obtained, using a very fast and innovative approach, based on the application of the Bidimensional Fast Fourier Transform to solve a bidimensional convolution in the domain of the spatial frequency.

Advances in electrochemical biosensor design for the detection of the stress biomarker cortisol.

The monitoring of stress levels in humans has become increasingly relevant, given the recent incline of stress-related mental health disorders, lifestyle impacts, and chronic physiological diseases. Long-term exposure to stress can induce anxiety and depression, heart disease, and risky behaviors, such as drug and alcohol abuse. Biomarker molecules can be quantified in biological fluids to study human stress. Cortisol, specifically, is a hormone biomarker produced in the adrenal glands with biofluid concentrations that directly correlate to stress levels in humans. The rapid, real-time detection of cortisol is necessary for stress management and predicting the onset of psychological and physical ailments. Current methods, including mass spectrometry and immunoassays, are effective for sensitive cortisol quantification. However, these techniques provide only single measurements which pose challenges in the continuous monitoring of stress levels. Additionally, these analytical methods often require trained personnel to operate expensive instrumentation. Alternatively, low-cost electrochemical biosensors enable the real-time detection and continuous monitoring of cortisol levels while also providing adequate analytical figures of merit (e.g., sensitivity, selectivity, sensor response times, detection limits, and reproducibility) in a simple design platform. This review discusses the recent developments in electrochemical biosensor design for the detection of cortisol in human biofluids. Special emphasis is given to biosensor recognition elements, including antibodies, molecularly imprinted polymers (MIPs), and aptamers, as critical components of electrochemical biosensors for cortisol detection. Furthermore, the advantages and limiting factors of various electrochemical techniques and sensing in complex biofluid matrices are overviewed. Remarks on the current challenges and future perspectives regarding electrochemical biosensors for stress monitoring are provided, including matrix effects (pH dependence and biological interferences), wearability, and large-scale production.