Silver coated magnetic nanoparticles for enhanced nucleic acid detection

摘要

Nanoparticle-based fluorescence DNA/RNA sensing offers promising applications in both research and medical diagnosisdue to the ease of surface chemical modification and sample handling, allowing detection in complex media. Theperformance of the conventional fluorescence biosensors is often limited by the insufficient fluorescence signal. Toovercome the disadvantage, we advanced silver-coated magnetic nanoparticles with strong plasmon resonance to enhancethe molecular beacon (MB)-based nucleic acid nanosensors. The silver-coated magnetic nanoparticles were chemicallysynthesized to compose of 20 nm iron oxide magnetic nanoparticle core and 60 nm thick Ag coating, forming iron oxide/Agcore-shell nanoparticles. Fluorescently labeled DNA MBs were immobilized on the Ag surface which serves as thequencher for the closed MBs and provides fluorescence enhancement for the unfolded MBs in the presence of thecomplementary target sequence. More importantly, the improved Ag shell mitigates the strong optical absorbance in thevisible range associated with the magnetic nanoparticles increasing the fluorescence intensity. The detection wasperformed by dispersing the nanosensors in a 20 μl analyte solution for 10 minutes for accelerated target capture through3D diffusion and concentrating them magnetically for enhanced fluorescence signal acquisition. The rapid, label-free DNAdetection resulted in a detection limit of 10 pM target DNA.