A new voltammetric method for the simultaneous determination of vitamin E and vitamin K present in different types of commercially available food supplements has been developed. This electroanalytical method is based on the ex situ adsorptive accumulation of these biologically active compounds onto the surface of a solid glassy carbon electrode (GCE) with subsequent electrochemical detection by square-wave adsorptive stripping voltammetry in 0.01-mol L⁻¹ HNO₃ containing 0.1-mol L⁻¹ KCl at pH 2.08. Due to reversible electrochemical reactions of phylloquinone, a subsequent voltammetric detection of both vitamins in anodic mode can be performed. Since individual forms of vitamins E and K usually exhibit nearly identical electrochemical behavior, it is therefore impossible to distinguish individual forms (quinones and tocopherols) and determine their molar concentrations in this way. Thus, the values of vitamin content were expressed as mass equivalent of phylloquinone and α-tocopherol as they are the most biologically active forms. Despite the high sensitivity, relatively short linear ranges were obtained due to the interaction (competition) of both vitamins during adsorption onto the freshly polished surface of the GCE from a 50% aqueous–acetonitrile mixture. The obtained results showed that the voltammetric approach is a very simple and low-cost analytical method that can be used in analyses of food supplements.

An electroanalytical study for possible simultaneous detection of three naturally occurring isomers of vitamin E (α, γ, and δ-tocopherol) was performed. This research includes several optimization steps, such as selection of electrode material, composition of working medium, selection of electrochemical technique, and parameters of square-wave voltammetry (SWV), to reach a well-defined recognition of peaks. A glassy carbon electrode, 99.9% acetonitrile containing 0.1 mol L⁻¹ lithium perchlorate, SWV at the potential step of 1 mV, potential amplitude of 25 mV, and frequency of 25 Hz were decided as the most suitable working conditions. Nevertheless, the corresponding anodic peaks were not sufficiently separated due to their overlapping. Thus, four standard evaluation methods (polynomial or linear baseline, zero base, and deconvolution) were compared, and the last-mentioned method was chosen as optimum. Similar linear ranges from 3.0 × 10⁻⁶ to 1.0 × 10⁻⁵ mol L⁻¹ were obtained for α, γ, and δ-tocopherol, characterized by determination coefficient of 0.998, 0.985, and 0.994, quantification limits of 11.28, 2.70, and 3.67 × 10⁻⁶ mol L⁻¹ and detection limits of 3.72, 0.89, and 1.21 × 10⁻⁶ mol L⁻¹, respectively. A recovery from 72.0 to 128.5% for different concetration ratios of tocopherols has been achieved. This recovery range is in the accordance with values reported for liquid chromatography.

Achieving and maintaining optimal oral health necessitates a comprehensive understanding of the complex bio‐adhesive and metabolic processes occurring within the oral cavity. These processes are significantly influenced by the intricate composition of oral fluids, particularly saliva and its resident microbiome. Currently available methodologies struggle to accurately monitor the dynamic and heterogeneous nature of key oral biomarkers, such as glucose. The development of miniaturized sensors for continuous and quantitative monitoring of clinically relevant salivary parameters represents a significant advancement in diagnostic capabilities. This work introduces an electrochemical sensor array designed for the continuous, quantitative monitoring of the clinically relevant and paradigmatic metabolite glucose. To address the challenges posed by the complex salivary environment, a surface modification strategy is implemented involving hybrid films of Prussian blue with chitosan and glucose oxidase enzyme entrapped within chitosan. The incorporation of chitosan, along with the further integration of zwitterionic polymer based on self‐polymerized dopamine (pDA) and 2‐ Methacryloyloxyethyl Phosphoryl Choline (MPC), facilitates the sensitive, selective, and reliable glucose monitoring in harsh salivary environments. Continuous amperometric glucose monitoring showcases the platform's capability for real‐time quantification, as increasing glucose concentrations correspond with elevated current signals. Pilot experiments show the sensors' capacity to precisely quantify salivary glucose levels and ascertain unknown concentrations, validated through the use of commercial glucometers. While the initial focus lies on glucose detection as a proof of concept, the final device integrates multiple electrochemical and potentiometric sensors. This advanced configuration enables the comprehensive quantification of several clinically relevant parameters in saliva. The development of multi‐sensor devices for continuous monitoring within the oral cavity holds immense potential: by unlocking deeper insights into the mechanisms driving the onset and progression of oral diseases, it will pave the way for further innovations in preventive dentistry.

Thyroxine (T4) is a key hormone regulating metabolic, cardiovascular, and neurodevelopmental processes, yet its clinical quantification still relies on centralized immunoassays that limit rapid or point-of-care monitoring. Here, we present a label-free biosensing platform based on silicon nanowire field-effect transistors (SiNW-FETs) functionalized with a T4-selective DNA aptamer via a 3-Triethoxysilyl propylsuccinic Anhydride (TESPSA)-mediated silanization approach, enabling a streamlined two-step modification for oriented immobilization. The biosensor achieves robust real-time detection of T4 across the physiological concentration range (5–30 pM), with a limit of detection of ~5 pM and a strong linear correlation between drain current and analyte concentration (R² = 0.9931). Specificity is confirmed using non-functionalized devices and estradiol as a non-target control. All measurements were performed in undiluted phosphate-buffered saline, representing a physiologically relevant ionic environment and demonstrating stable sensor performance under realistic buffer conditions. The dose–response behavior follows a Hill model, allowing extraction of binding parameters and confirming that the electrical signal originates from specific aptamer–target interactions. These results demonstrate that aptamer-functionalized SiNW-FETs provide a highly sensitive, selective, and miniaturizable platform for quantitative thyroid hormone monitoring, with strong potential for future point-of-care applications.