Ultrasensitive Detection of Single Nucleotide Polymorphism in Human Mitochondrial DNA Utilizing Ion-Mediated Cascade Surface-Enhanced Raman Spectroscopy Amplification

Although surface-enhanced Raman spectroscopy (SERS) has been featured by high sensitivity, additional signal enhancement is still necessary for trace amount of biomolecules detection. In this paper, a SERS amplified approach, featuring ions-mediated cascade amplification (IMCA), was proposed by utilizing the dissolved silver ions (Ag+) from silver nanoparticles (AgNPs). We found that using Ag+ as linkage agent can effectively control the gaps between neighboring 4-aminobenzenethiol (4-ABT) encoded gold nanoparticles (AuNPs@4-ABT) to form hot spots and thus produce SERS signal output, in which the SERS intensity was proportional to the concentration of Ag+ . Inspired by this finding, the IMCA was utilized for ultrasensitive detection of single nucleotide polymorphism in human mitochondrial DNA (16189T -> C). Combining with the DNA ligase reaction, each target DNA binding event could successfully cause one AgNP introduction. By detecting the dissolved Ag+ from AgNPs using IMCA, low to 3.0 x 105 fm/mu L targeted DNA can be detected, which corresponds to extractions from 200 nL cell suspension containing carcinoma pancreatic beta-cell lines from diabetes patients. This IMCA approach is expected to be a universal strategy for ultrasensitive detection of analytes and supply valuable information for biomedical research and clinical early diagnosis.