DNA assay based on monolayer-barcoded nanoparticles for mass spectrometry in combination with magnetic microprobes.

Mass spectrometry (MS) based methodology offers simple, fast and sensitive diagnosis. While it has become the predominate approach in biomolecular analysis, it has not been suitable for analyzing nucleic acid due to its low ionization efficiency. We report herein on a DNA assay based on monolayer-barcoded nanoparticles that were encoded with reporter mass molecules, which act as surrogate molecules for the matrix-assisted laser desorption/ionization time-of-flight MS (MALDI-TOF MS) identification of target DNA through mass spectrometry in combination with magnetic microprobes. This assay demonstrated high MS sensitivity, with the ability to detect target DNA at femtomolar (10(-15) M) levels. This inaugural effort using combined techniques is significant because it showed an extraordinary analytical capability for differentiating the single nucleotide polymorphism (SNP), which comprises the most abundant source of genetic variation in the human genome. We also report herein the feasibility of MS detection of two target DNAs that have the same mass but different nucleotide base composition, which classic MS methodology is inherently unable to differentiate.