Voltammetric Aptamer-Based Biochip Featuring Poly Gallic Acid/SnO2-MoO3 Nanocomposite for Selective Tryptophan Detection: Potential Application in Alzheimer's Diagnosis

초록

Tryptophan (Trp) levels are associated with Alzheimer's disease (AD), suggesting its utility as a diagnostic marker in AD patients. In this study, a disposable screen-printed carbon electrode modified with an aptamer, poly gallic acid, and SnO2-MoO3 nanoparticles (Apt/p-GA/SnO2-MoO3/SPCE) was demonstrated for voltammetric selective detection of Trp in clinical plasma samples. X-ray photoelectron and impedance spectroscopy, along with cyclic voltammetry, revealed that SnO2-MoO3 nanoparticles enlarged an effective surface area, while p-GA enhanced aptamer immobilization leading to selectivity for target molecules. The synergistic effects of these components promote excellent electron transfer to Trp. Differential pulse voltammetric measurements for Trp oxidation with Apt/p-GA/SnO2-MoO3/SPCE provided a wide linear range (0.5-100 mu M) and a low limit of detection (0.189 mu M) with a reasonable sensitivity (0.352 mu A mu M-1 cm(-2)), comparable to the reported single metal oxide-based composite electrodes. Further application of the aptasensor to clinical plasma samples from healthy individuals and AD patients revealed an effective reduction of matrix effects during Trp analysis. The sample analysis results were also closely correlated with those obtained using the enzyme-linked immunosorbent assay, highlighting the accuracy and practical utility of the sensor for clinical assessment.

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