چكيده به لاتين
Amyotrophic lateral sclerosis (ALS) is one of the most devastating neurological diseases, progressively damaging the myelin sheath of axons and dendrites in both upper and lower motor neurons. This deterioration results in the loss of control over vital functions such as walking, breathing, swallowing, and speaking. Therefore, monitoring individuals’ health and screening for early diagnosis of this disease is crucial. Early detection of ALS through continuous monitoring of biomarkers in saliva offers a highly effective, non-invasive method. In this study, a multi-response sensor (colorimetric, fluorometric, and electrochemical) based on nanozymes within a bimetallic cerium and vanadium metal-organic framework (UiO-66-NH2(Ce/V)), integrated into agarose hydrogel, was developed for detecting the biomarker L-serine. Physical, chemical, and electrochemical analyses confirmed that the nanozyme possesses optimal properties for catalytic pseudo-peroxidase reactions. The UiO-66-NH2(Ce/V) nanozyme, functioning as a pseudo-peroxidase, facilitated the oxidation of tetramethylbenzidine (TMB) in the colorimetric sensor, ortho-phenylenediamine (OPD) in the fluorometric sensor, and TMB in the electrochemical sensor. The oxidation of these tracers resulted in the formation of colored compounds in the colorimetric and fluorometric sensors, as well as the development of anodic and cathodic peaks in the electrochemical sensor. Increasing the concentration of L-serine inhibited the oxidation-reduction reactions, causing a reduction in the intensity of both the colors and the sensor peaks. Key operational parameters such as response time, pH, nanozyme concentration, agarose concentration, tracer concentration, and oxidizing agent concentration were optimized to achieve the best performance. The optimal conditions for each sensor were: pH 4, nanozyme concentrations of 0.22% w/v for the colorimetric sensor, 0.20% for the fluorometric sensor, and 0.47% for the electrochemical sensor. Agarose concentrations were 92% for the colorimetric sensor, 86.2% for the fluorometric sensor, and 35.62% for the electrochemical sensor. Additionally, the chromogenic tracer concentrations for the three sensors were 2.5, 4, and 0.7 mM, respectively, with an oxidizing agent concentration of 3% by volume for both the colorimetric and fluorometric sensors. The optimal response times were calculated as 60 seconds for the colorimetric sensor, 40 seconds for the fluorometric sensor, and 120 seconds for the electrochemical sensor. The linear detection ranges for L-serine were 1-250 μM for the colorimetric sensor, 1-250 μM for the fluorometric sensor, and 0.3-250 μM for the electrochemical sensor. The corresponding detection limits were 0.27 μM, 0.26 μM, and 0.076 μM, respectively. These sensors, exhibiting a standard deviation of less than 5%, demonstrated excellent selectivity and reproducibility. They were successfully applied to the detection of L-serine in human saliva samples, achieving recovery rates between 92.20% and 107.50%. The findings suggest that these sensors have significant potential for use in on-site healthcare systems for monitoring disease biomarkers and represent a promising approach for the early diagnosis of the disease.
