Rapid, cost-effective DNA quantification via a visually-detectable aggregation of superparamagnetic silica-magnetite nanoparticles

DNA and silica-coated magnetic particles entangle and form visible aggregates under chaotropic conditions with a rotating magnetic field, in a manner that enables quantification of DNA by image analysis. As a means of exploring the mechanism of this DNA quantitation assay, nanoscale SiO 2 -coated Fe 3 O 4 (Fe 3 O 4 @SiO 2 ) particles are synthesized via a solvothermal method. Characterization of the particles defines them to be ∼200 nm in diameter with a large surface area (141.89 m 2 /g), possessing superparamagnetic properties and exhibiting high saturation magnetization (38 emu/g). The synthesized Fe 3 O 4 @SiO 2 nanoparticles are exploited in the DNA quantification assay and, as predicted, the nanoparticles provide better sensitivity than commercial microscale Dynabeads® for quantifying DNA, with a detection limit of 4 kilobase-pair fragments of human DNA. Their utility is proven using nanoparticle DNA quantification to guide efficient polymerase chain reaction (PCR) amplification of short tandem repeat loci for human identification.