Search Results (209)

Background/Objectives: This study systematically analyzed the concentration dynamics of human milk oligosaccharides (HMOs) and the distribution characteristics of secretory (Se) and Lewis (Le) phenotypes in China. Methods: A total of 1462 breast milk samples were collected from lactating mothers in six major regions of China, including Changchun, Lanzhou, Chengdu, Tianjin, Guangzhou, and Shanghai. We quantified 17 major HMOs by high-performance anion exchange chromatography-pulsed amperometric detection (HPAEC-PAD), and Se/Le phenotypes were determined to evaluate regional differences and distribution patterns. Results: Total HMO concentration in breast milk showed a significant downward trend within 200 days postpartum and stabilized after 200 to 400 days. Fucosylated HMOs accounted for the highest proportion $60.0–83.0\%$, among which 2′-FL had the largest concentration $903.4–2832.7 \mathrm{m}\mathrm{g}/\mathrm{L}$; acetylated HMOs $8.4–17.6\%$ and sialylated HMOs $8.2–25.3\%$ accounted for relatively lower proportions. This study further divided breast milk into four phenotypes based on HMO characteristics: 72.49% of the samples were Se+/Le+, 6.145% were Se+/Le−, 20.12% were Se−/Le+, and 1.24% were double negative (Se−/Le−). Se+ and Le+ phenotypes accounted for 78.7% and 92.6% of the total population, respectively. The total concentration of HMOs in breast milk of different phenotypes was significantly different, with the average total HMO concentration of Se+/Le+ breast milk being the highest (8342 mg/L), while that of Se−/Le− breast milk being the lowest (4532 mg/L). Se+ phenotype was associated with higher levels of fucosylated HMOs, including 2′-fucosyllactose (2′-FL) and lacto-N-fucopentaose I (LNFP I), and lower levels of lacto-N-tetraose (LNT) and sialyl-lacto-N-tetraose b (LST b) compared to other phenotypes. Most HMOs reached their highest concentrations during the colostrum (CM) and transitional milk (TM) stages, followed by a progressive decline with lactation, with phenotype-specific variations evident across all HMOs. Notably, certain HMOs, such as 3-FL, 3′-SL, DFL, and LNDFH II, exhibited distinct temporal patterns. Conclusions: This study revealed the Se/Le phenotype distribution and dynamic characteristics of HMOs in the Chinese mother-infant population, offering a valuable reference for global breast milk composition databases and infant nutrition research. 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

In situ electrochemical imaging of corrosion reactions is performed directly by scanning electrochemical microscopy (SECM) in generation-collection mode. This method involves redox conversion of soluble metal ions at the amperometric tip for quantification. Unfortunately, many metals, such as copper, do not undergo redox conversion to a soluble state and are deposited on the SECM tip. They therefore modify the electrochemical behavior of the tip and require consideration of metal stripping processes. In addition, the miniaturization of the electrode to operate as a microelectrode tip can be accompanied by variations in the potential range and distribution of the redox processes related to copper deposition and redissolution, thus complicating the adequate choice of electrochemical conditions applied to the tip for the unambiguous operation of SECM in the generation-collection mode to study the corrosion of copper-based materials. Therefore, in this work, a study of different parameters for the amperometric determination of Cu²⁺ ions was conducted using gold disk electrodes of 500 and 10 μm diameter to represent the typical sizes employed in conventional and scanning microelectrochemical measurements. The investigation was performed to analyze the effect of underpotential deposition (UPD) and overpotential deposition (ODP) on the voltammetric characteristics of copper deposition and redissolution resulting from variations in the solution composition, i.e., the nature of anions and pH. The dependence and limits of the reduction and reoxidation waves were analyzed as functions of the Cu²⁺ ion concentration, the ionic strength of the electrolyte, and the pH of the solution. The results were interpreted as UPD and OPD. Under conditions close to the marine environment, the release of Cu²⁺ ions can be unambiguously detected and quantified from potentials above −0.1 V vs. Ag/AgCl. Full article

The bioanalysis of body fluids plays a crucial role in clinical diagnostics, pharmaceutical research, forensic science, and biomarker discovery. Traditional chromatographic techniques are widely used in clinical laboratories but are often costly and time-consuming. Capillary electrophoresis (CE) and its modifications, such as capillary zone electrophoresis, isotachophoresis, and micellar electrokinetic chromatography, have emerged as efficient, cost-effective, and miniaturized alternatives for analyzing small organic and inorganic molecules in biological fluids. This paper deals with the applications of CE-based electromigration techniques in the determination of various analytes in urine, blood, saliva, and cerebrospinal fluid. The study further discusses the advantages and limitations of different detection methods, including ultraviolet-visible spectroscopy, laser-induced fluorescence, mass spectrometry, conductivity, and amperometric detection. A focus is given to the identification and quantification of amino acids and their metabolites as potential biomarkers for metabolic and degenerative disorders. The work highlights recent advancements in CE methodologies and their potential to enhance sensitivity and selectivity in bioanalytical applications. Full article

Colorectal cancer (CRC) remains a significant global health burden, mainly due to late diagnosis and chemotherapy resistance. Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine associated with tumor progression, has emerged as a promising biomarker in CRC. However, its clinical utility is limited by the lack of rapid and accessible detection methods. In this study, we report an electrochemical immunotechnology for the sensitive and selective quantification of MIF protein in CRC tissue samples. By combining magnetic microparticles (MMPs), antibody-based recognition, horseradish peroxidase (HRP) labeling, and amperometric transduction at disposable screen-printed carbon electrodes (SPCEs), the developed methodology displayed a linear dynamic range from 0.24 to 20 ng mL⁻¹, enabling quantification across clinically relevant MIF levels, and achieving a low limit of detection (0.07 ng mL⁻¹). In addition, the developed method is the only one reported for MIF assembled on MMPs and addresses its determination in a relevant oncological scenario (paired non-tumoral (NT) and tumoral (T) tissues from individuals diagnosed with CRC at different stages of the disease). The analysis, requiring only 100 ng of tissue extract, allowed efficient discrimination between NT and T paired tissues, and successfully differentiated between healthy, early (I–II) and advanced (III–IV) CRC stages, achieving these results in just 105 min. Full article

Background/Objectives: This study comprehensively characterized the O- and N-glycosylation profiles of bispecific antibodies (BsAbs) via advanced analytical techniques to evaluate their structural and functional implications. Methods: High-resolution MS revealed O-xylosylation at Ser468 within the (G4S)4 linker peptide, which was identified as xylose with a molecular weight of 132.042 Da. HILIC-HPLC analysis of N-glycosylation revealed glycan species engineered to eliminate Fc effector functions. O-glycosylation analysis via β-elimination followed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) identified xylose as the predominant glycan. Results: O-xylosylation does not affect the binding of BsAbs to either antigen Programmed Death-1 (PD-1) or Vascular Endothelial Growth Factor (VEGF). Notably, O-xylosylation interactions with mannose receptor represent the first discovery highlighting potential immunomodulatory roles. Conclusions: This study highlights the critical importance of monitoring comprehensive glycosylation characterization during the development of BsAb with (G4S)n linkers to ensure optimal therapeutic efficacy, safety, and reduced immunogenic potential. Full article

A novel voltammetric sensor was constructed by modifying a glassy carbon electrode with a composite material consisting of platinum–nickel-doped tin oxide and carbon black (PtNiSnO₂-CB/GCE), enabling highly sensitive differential pulse voltammetry (DPV) determination of trazodone HCl (TRZ). The DPV experimental parameters, including the composition of the supporting electrolyte and instrumental settings, were carefully optimized to achieve maximum analytical efficiency. Within the linear range of 1–10 µM, quantification of TRZ molecules could be performed without the preconcentration step. When applying a 60 s accumulation time (in the range 0.02–0.2 µM of TRZ), the detection limit reached 4.1 nM (1.67 mg L⁻¹), indicating superior sensitivity compared to previously reported voltammetric techniques. The method demonstrated good reproducibility, with a relative standard deviation of 4.3% for 10 repeated measurements at 0.06 µM TRZ. The developed sensor exhibits excellent stability, simplicity of fabrication, and operational convenience. Its practical applicability was confirmed by the successful analysis of molecules of TRZ in diverse sample types, including pharmaceutical products, urine, plasma, river water, and artificial gastric and intestinal fluids, with recovery rates between 97.7% and 104.2%. Flow injection analysis (FIA) with amperometric detection was also performed for TRZ molecule determination. 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

Celiac disease (CD), a human leukocyte antigen-associated disorder, is caused by gluten sensitivity and is characterized by mucosal alterations in the small intestine. Currently, its diagnosis involves the determination of serological markers. The traditional method for clinically determining these markers is the enzyme-linked immunosorbent assay. However, immunosensors offer sensitivity and facilitate the development of miniaturized and portable analytical systems. This work focuses on developing an amperometric immunosensor for the quantification of IgA antibodies against tissue transglutaminase (IgA anti-TGA) in human serum samples, providing information on a critical biomarker for CD diagnosis. The electrochemical device was designed on a polyimide substrate using a novel solid ink of wax and carbon nanofibers (CNFs). The working electrode microzone was defined by incorporating aminofunctionalized TiO₂ nanoparticles (TiO₂NPs). The interactions and morphology of CNFs/wax and TiO₂NPs/CNFs/wax electrodes were assessed through different characterization techniques. Furthermore, the device was electrochemically characterized, demonstrating that the incorporation of CNFs into the wax matrix significantly enhanced its conductivity and increased the active surface area of the electrode, while TiO₂NPs contributed to the immunoreaction area. The developed device exhibited remarkable sensitivity, selectivity, and reproducibility. These results indicate that the fabricated device is a robust and reliable tool for the precise serological diagnosis of CD. Full article

A facile fabrication method was developed for the growth of Cu_1.8Se nanosheets (NSs) on a Cu foil substrate, enabling dual-functionality as an electrochemical sensor for H₂O₂ and an active surface-enhanced Raman scattering (SERS) substrate. The process involved the preparation of Cu(OH)₂ nanowires (NWs) via electrochemical oxidation, followed by chemical conversion to Cu_1.8Se through a selenization process. The morphology, composition, and microstructure of the resulting Cu_1.8Se NSs were systematically characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The Cu_1.8Se NSs exhibited excellent electrocatalytic activity for H₂O₂ reduction, achieving a notably low detection limit of 1.25 μM and demonstrating rapid response and high sensitivity with a linear relationship in amperometric detection. Additionally, SERS experiments using Rhodamine B as a probe molecule and the Cu_1.8Se NS/Cu foil as a substrate displayed outstanding performance, with a detection limit as low as 1 μM. The flower-like structure of the Cu_1.8Se NSs exhibited linear dependence between analyte concentration and detection signals, along with satisfactory reproducibility in dual-sensing applications. These findings underscore the scalability and potential of this fabrication approach for advanced sensor development. Full article

NiFe₂O₄ and TiO₂ are widely studied for photoelectrochemical (PEC) applications due to their unique properties. Nitrogen-doped graphene (NG) and metal–organic frameworks (MOFs), such as MIL-100(Fe) (where MIL stands for Materials of Lavoisier Institute), are commonly incorporated to enhance PEC performance by offering a high surface area and facilitating efficient charge transport. Composite systems are commonly employed to overcome the limitations of individual PEC catalysts. In this study, a highly efficient NiFe₂O₄/NG@MIL-100(Fe)/TiO₂ photoanode was developed to enhance photoelectrochemical water-splitting performance. The composite was synthesized via a hydrothermal method with a two-step heating process. X-ray diffraction confirmed the expected crystal structures, with peak broadening in NiFe₂O₄ indicating reduced crystallite size and increased lattice strain. X-ray photoelectron spectroscopy of the Ni 2p and Fe 2p regions validated the successful integration of NiFe₂O₄ into the composite. Electrochemical analysis demonstrated excellent performance, with linear sweep voltammetry achieving a peak photocurrent density of 3.5 mA cm⁻² at 1.23 V (vs RHE). Electrochemical impedance spectroscopy revealed a reduced charge-transfer resistance of 50 Ω, indicating improved charge transport. Optical and electronic properties were evaluated using UV-Vis spectroscopy and Tauc plots, revealing a direct bandgap of 2.1 eV. The composite exhibited stable photocurrent under amperometric J-t testing for 2000 s, demonstrating its durability. These findings underscore the potential of NiFe₂O₄/NG@MIL-100(Fe)/TiO₂ as a promising material for renewable energy applications, particularly in photoelectrochemical water splitting. Full article

Background: Prebiotics are non-digestible dietary compounds, defined as substrates that are utilised by host microorganisms conferring a health benefit. Although fructo-oligosaccharides (FOSs) and galacto-oligosaccharides (GOSs) are among the most studied prebiotics and support intestinal normobiosis, comprehensive data on their content in foods remain limited. Objectives: The objective was to quantify the content of FOSs (kestose, nystose, and 1 F-β-fructofuranosylnystose) and GOSs (raffinose and stachyose) in 35 foods, including fruit and nuts, legumes, and cereals. We also estimated the intakes of prebiotics in an Italian population. Methods: We analysed the prebiotic content in foods using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). We estimated the prebiotic intake of 100 healthy controls from a case-control study on colorectal cancer conducted in Italy between 2017 and 2019. We used dietary information collected through a food frequency questionnaire and the prebiotic data quantified in this and a previous study. Results: FOSs were mostly detected in cereal products, with wheat bran and whole-meal rye flour containing the highest amount (around 0.7 g/100 g each). GOSs were most abundant in legumes, especially in dried soy products (around 4.0 g/100 g each). Mean daily intake was 0.236 g for total FOSs and 0.371 g for total GOSs. Wheat bran, raspberries, chestnuts, walnuts, raisins, soy milk, and soy yoghurt overall accounted for 3.9% of kestose, 1.2% of nystose, 0% of 1F-β-fructofuranosylnystose, 15.5% of raffinose, and 8.3% of stachyose total intakes. Conclusions: The present study enables the development of a comprehensive database on prebiotic content in foods through a consistent analytical method. This makes prebiotic intake assessments more accurate than previously available data and facilitates future epidemiological studies investigating their potential effects on health. Full article

Objectives: The purpose of this study was to further characterize the ultrafiltration (UF) method for determining free saccharide levels in glycoconjugate vaccines and compare it with other methods used for the determination of free saccharide levels in meningococcal glycoconjugate vaccines. Methods: We performed experiments on both meningococcal glycoconjugates and capsular polysaccharides, and compared UF, deoxycholate (DOC) precipitation, and solid-phase extraction (SPE) methods. Meningococcal capsular polysaccharides from groups A (MenA), C (MenC), and W (MenW) were depolymerized and characterized using SEC-MALS (size-exclusion chromatography with multi-angle laser light scattering) to determine the molecular weight and hydrodynamic size and then subjected to UF. The free saccharide content was quantified using HPAEC-PAD (high-performance anion-exchange chromatography with pulsed amperometric detection). Results: The characterization of size-reduced group C polysaccharide revealed weight-average molecular mass (Mw) ranging from 22,200 g/mol to 287,300 g/mol and hydrodynamic radii of 3.7 to 19.5 nm. Pore size studies confirmed that polysaccharides with diameters up to 15 nm filtered through the 100 kDa cellulose membrane. The smallest PS fragment tested (22,200 g/mol, 7.4 nm diameter) was partially recovered from the 30 kDa membrane. For MenC-CRM₁₉₇, DOC yielded the lowest free saccharide content (<1%), UF gave moderate results (7–8%), and SPE showed the highest and most variable values (up to 15%). For MenA- and MenW-CRM₁₉₇, UF and DOC consistently provided low free saccharide levels (<2% and 3–11%, respectively). Conclusions: The upper limits on the size of free group C meningococcal polysaccharides that can be ultrafiltered were assessed. Differences in the relative amount of free saccharide were observed between various methods used to control meningococcal conjugate vaccines. Full article

Bisphenol A (BPA) is a typical environmental estrogen that is distributed worldwide and has the potential to pose a hazard to the ecological environment and human health. The development of an efficient and sensitive sensing strategy for the monitoring of BPA residues is of paramount importance. A novel electrochemical sensor based on carbon black and carbon nanofibers composite (CB/f-CNF)-assisted signal amplification has been successfully constructed for the amperometric detection of BPA in foods. Herein, the hybrid CB/f-CNF was prepared using a simple one-step ultrasonication method, and exhibited good electron transfer capability and excellent catalytic properties, which can be attributed to the large surface area of carbon black and the strong enhancement of the conductivity and porosity of carbon nanofibers, which promote a faster electron transfer process on the electrode surface. Under the optimized conditions, the proposed CB/f-CNF/GCE sensor exhibited a wide linear response range (0.4–50.0 × 10⁻⁶ mol/L) with a low limit of detection of 5.9 × 10⁻⁸ mol/L for BPA quantification. Recovery tests were conducted on canned peaches and boxed milk, yielding satisfactory recoveries of 86.0–102.6%. Furthermore, the developed method was employed for the rapid and sensitive detection of BPA in canned meat and packaged milk, demonstrating comparable accuracy to the HPLC method. This work presents an efficient signal amplification strategy through the utilization of carbon/carbon nanocomposite sensitization technology. Full article