Design and Characterization of the APTA Biosensor/Cy3 Fluorescent Probe Consisting of CdTe Quantum Dots and Aptamers for the Detection of 25-Hydroxyvitamin D3

Abstract

This study presents an ultrasensitive and cost-effective fluorescent probe designed to measure 25-hydroxyvitamin D3 [25(OH)D3]. The probe, referred to as the APTA biosensor/Cy3, is composed of cadmium telluride quantum dots (CdTe QDs), a thiol-25(OH)D3-aptamer (APTA), and a Cy3-labeled aptamer. The fluorescence intensity in this Förster Resonance Energy Transfer (FRET) system decreases due to the optimal alignment of the emission spectrum of the CdTe QDs with the absorption spectrum of Cy3. Additionally, this quenching effect becomes more noticeable with the introduction of 25(OH)D3 into the system. The study established a linear relationship between fluorescence intensity and the concentration of 25(OH)D3, achieving a detection limit of 8.05 × 10^-9 M. The APTA biosensor/Cy3 demonstrated excellent selectivity and specificity for 25(OH)D3, with recovery rates ranging from 96.00% to 100.88% in human serum and urine samples through the spiking method. The structural and morphological characteristics of the probe were confirmed using various analytical techniques, including UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamic light scattering (DLS). Overall, these results indicate that the FRET-based APTA biosensor/Cy3 has significant potential for developing fluorescent probes that can detect low-concentration analytes.