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Salivary thiocyanate is a biomarker of individual health that notably allows for the discrimination between smokers and non‐smokers. Recent studies have also demonstrated its potential as a biomarker of cystic fibrosis, thus rendering the development of methods for its determination in saliva of immense importance. In response, we report on the development of graphite screen‐printed electrodes (SPE) modified with cobalt(II) phthalocyanine nanosticks (CoPcNst), as low‐cost and semi‐disposable sensors for the determination of thiocyanate ion (SCN−) in human saliva. CoPCNst were synthesized and characterized using scanning electron microscopy, x‐ray diffraction, as well as infrared and Raman spectroscopies. The results revealed a structural proximity to the recently identified J‐polymorph. Compared with the electrode modified with commercial, beta‐structure cobalt(II) phthalocyanine, the CoPc Nst/SPE provided four times better LOD and LOQ (0.49 and 1.62 μM) for thiocyanate determination by differential pulse voltammetry. The response was linear up to 20 μM SCN− (R2=0.996) and it was not affected by excess of common electro active compounds, such as ascorbic and uric acid. The analytical utility of CoPc Nst/SPE in human saliva is demonstrated. [ABSTRACT FROM AUTHOR]

This study endeavored to design and develop an innovative closed-loop diagnostic and therapeutic system with the following objectives: (a) the noninvasive detection of glucose concentration in sweat utilizing nanonengineered screen-printed biosensors; (b) the management of measured data through a specialized computer system comprising both hardware and software components, thereby enabling the precise control of therapeutic responses via a patch-based nanomedicine delivery system. This initiative addresses the significant challenges inherent in the management of diabetes mellitus, including the imperative need for glucose-level monitoring to optimize glycemic control. Leveraging chronoamperometric results as a foundational dataset and the in vivo hypoglycemic activity of nanoemulsion formulations, this research underscores the efficacy and accuracy of glucose concentration estimation, decision-making mechanism responses, and transdermal hypoglycemic treatment effects, within the proposed system. [ABSTRACT FROM AUTHOR]

The modification of graphite screen-printed electrodes (SPEs) is reported using an eco-friendly and extremely fast method based on the direct cobalt pin electrode-to-SPE spark discharge at ambient conditions. This approach does not utilize any liquids or chemical templates, does not produce any waste, and allows the in-situ generation of CoxOy nanoparticles onto the electrode surface and the development of efficient electrocatalytic sensing surfaces for the determination of H2O2. Co-spark SPEs were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy (XPS), revealing the formation of surface confined CoxOy nanoparticles and the diverse oxidation states of cobalt species. Co-spark SPEs were also characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Redox transitions of the surface confined electrocatalysts are demonstrated by electrochemical polarization studies, showing the formation of different oxides (CoxOy), varying the XPS results. Amperometric measurements at 0.3 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of H2O2 over the range 1 − 102 μM, achieving a limit of detection (3σ/m) of 0.6 μM. The interference effect of various electroactive species was effectively addressed by employing dual measurements in the absence and presence of the enzyme catalase. The analytical utility of the method was evaluated in antioxidant rich real-world samples, such as energy drinks, demonstrating sufficient recovery. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of multi-walled carbon nanotubes (MWCNTs) and bio-graphene (bG) on the structure and activity of glucose oxidase (GOx), as well as on the performance of the respective electrochemical glucose biosensors. Various spectroscopic techniques were applied to evaluate conformational changes in GOx molecules induced by the presence of MWCNTs and bG. The results showed that MWCNTs induced changes in the flavin adenine dinucleotide (FAD) prosthetic group of GOx, and the tryptophan residues were exposed to a more hydrophobic environment. Moreover, MWCNTs caused protein unfolding and conversion of α-helix to β-sheet structure, whereas bG did not affect the secondary and tertiary structure of GOx. The effect of the structural changes was mirrored by a decrease in the activity of GOx (7%) in the presence of MWCNTs, whereas the enzyme preserved its activity in the presence of bG. The beneficial properties of bG over MWCNTs on GOx activity were further supported by electrochemical data at two glucose biosensors based on GOx entrapped in chitosan gel in the presence of bG or MWCNTs. bG-based biosensors exhibited a 1.33-fold increased sensitivity and improved reproducibility for determining glucose over the sweat-relevant concentration range of glucose. [ABSTRACT FROM AUTHOR]