Ferric nanoparticle-based resonance light scattering determination of DNA at nanogram levels

A novel assay of DNA has been proposed by using ferric nanoparticles as probes coupled with resonance light scattering (RLS) detection. At pH 7.40, the RLS intensity of ferric nanoparticles can be greatly enhanced by the aggregation of positively charged ferric nanoparticles through electrostatic interaction with negatively charged DNA. The enhanced intensity of RLS at 452 nm is proportional to the concentration of DNA in the range of 0.01–0.8 μg ml−1 for calf thymus and salmon sperm DNA and in the range of 0.005–0.3 μg ml−1 for E. coli K12 genomic DNA. Detection limits are 3.6 ng ml−1 for calf thymus DNA, 4.4 ng ml−1 for salmon sperm DNA, and 1.9 ng ml−1 for E. coli K12 genomic DNA, respectively. Compared with the chromophores previously used in RLS assay, the ferric nanoparticles have offered several advantages in easy preparation, good photostability and high sensitivity without being modified or functionalized.