SOUTHERN JOURNAL OF SCIENCES

Background: A crucial aspect of electrochemical enzymatic biosensor development is the immobilization of the enzymes, as it directly influences the sensitivity of the bioelectrode. Among the different methods used to incorporate enzymes on the surface of the transducers, layer-by-layer (LbL) self-assembly based on electrostatic interaction with polyelectrolytes of opposite charge stands out due to its simplicity and reproducibility. Aims: The aim of the work was to develop an electrochemical glucose biosensor by LbL assembly of a new functionalized chitosan polycation and the enzyme glucose oxidase (GOx). Methods: Chitosan was chemically functionalized with glucose by the Maillard reaction. The resulting polycation, named G-Chit, is soluble in the medium compatible with the enzyme. The bioelectrode was obtained by alternating adsorption of G-Chit and GOx onto carbon paste electrodes. By selecting the number of bilayer of G-Chit/GOX, the enzyme concentration, and the pH, the electroanalytical performance of the biosensor was optimized. The electrochemical responses were characterized by cyclic voltammetry and chronoamperometry. Results: Under optimized experimental conditions, the biosensor exhibited a sensitivity of (0.81 ± 0.03) µA mM-1 in a glucose concentration range of (0.18 to 1.75) mM. Discussion: Results indicated that catalytic response increases both with the number of G-Chit/GOx bilayers and the enzyme concentration, obtaining the best responses for 3 bilayers and 2 mg mL-1, respectively, while the optimum working pH value was 7.0. Conclusions: The analytical response of the biosensor was tested in milk samples with negligible matrix effects, suggesting a potential application in other dairy products. Results show that G-Chit appears promising for the immobilization of enzymes.

Background: Background: Vitamin D plays an essential role in bone health and overall physiological function, and its deficiency is common in children and adolescents with β-thalassemia major (βTM). Iron overload, as reflected by elevated ferritin, may further influence vitamin D status. Aim: This study aimed to evaluate serum vitamin D levels in βTM patients and determine their association with ferritin levels. Methods: A total of 40 βTM patients and 20 age-matched healthy controls (aged 4–25 years) were enrolled between October 2024 and February 2025. Serum vitamin D, calcium, ferritin, and hemoglobin were measured. Statistical analysis, including correlation and logistic regression, was performed using SPSS v.26 to identify predictors of vitamin D deficiency. Results: Vitamin D deficiency was highly prevalent among βTM patients (70%) compared with controls. Patients showed significantly lower vitamin D levels (17.32±1.56) than controls (25.34±1.76). Vitamin D levels were positively correlated with age (r = 0.788), calcium (r = 0.772), and hemoglobin (r = 0.771), and negatively correlated with ferritin (r = −0.517). Logistic regression demonstrated that ferritin >1000 ng/mL strongly predicted vitamin D deficiency (OR = 17.875; 95% CI: 3.258–98.074; p = 0.001), while younger age ( < 10 years) also increased the odds of deficiency (OR = 5.200; p = 0.018). Discussion: D deficiency is a prevalent and intrinsic metabolic disturbance in β-thalassemia major, closely linked to chronic iron overload and elevated ferritin levels. This interplay disrupts hepatic vitamin D hydroxylation, induces inflammation, and contributes to endocrine and skeletal complications, highlighting ferritin as a key predictor of deficiency in these patients. Conclusion: Vitamin D deficiency is highly prevalent in βTM and is strongly associated with elevated ferritin levels, suggesting that iron overload is a significant predictor. Integrating vitamin D assessment into routine monitoring may support better management of disease-related metabolic disturbances in patients with βTM.

Introduction: Thermal insulating coatings are increasingly being introduced into construction practice for internal and external finishing enclosing structures and pipelines. Thermal insulation coatings are usually made based on polymer binder and mineral fillers. The durability and stability of the properties of heat-insulating materials depend on the type of binder. As a rule, polymers are used as a binder: epoxy resin; silicone rubber; urea-formaldehyde resins; aqueous dispersed polymers - styrene-butadiene, polyvinyl acetate, and acrylate (acrylic and styrene-acrylic). The quality indicator of binders can be assessed by the influence of the seasonality of climatic impact, and as a result, the best elastic strength characteristics of binders can be established after one month to a year of field tests. Aim: To determine the influence of climatic factors on the change in the elastic-strength indicators of epoxy polymers binders used in liquid thermal insulation coatings. Methods: A tensile testing machine of the AGS-X series with the TRAPEZIUM X software was used for mechanical tests. The tests were carried out in accordance with GOST 11262-2017 (ISO 527-2: 2012) "Plastics. Tensile test method". Results and Discussion: The paper discusses the results of experimental studies of the compositions of polymer binders and their resistance to various climatic factors, which will later be used as a polymer binder for thermal insulation coatings based on fine mineral granular systems. Conclusions: When analyzing the changes in the characteristics of polymer samples after exposure to climatic factors, it was found that compositions based on Etal-247 epoxy resin, cured with amine hardeners Etal-1440N, Etal-1460, Etal-1472, and Etal-45M, demonstrate the best elastic strength characteristics after one year of full-scale tests. The high stability of the indicators under consideration allows us to conclude that the use of Etal-247 resin as a base leads to creating of the most climate-resistant epoxy coatings.