Adsorption behaviors of DNA by modified magnetic nanoparticles: Effect of spacer and salt

• Spacers conjugated ACO MNPs were prepared.
• ACO MNPs were prepared by EDC coupling agent.
• The length of spacer arm has great effect on the adsorption process.

The isolation of nucleic acid is an essential operation before biochemical and diagnostic processes. Here the adsorption of plasmid DNA and salmon sperm DNA on amine magnetic nanoparticles coated with ligand acridine orange was investigated. Spacers such as 6-bromohexanoic acid, 4-bromobutyric acid, and 2-bromoacetic acid were used to facilitate connection between the magnetic nanoparticles and acridine orange. We carried out adsorption mechanism with a study of adsorption isotherm and adsorption kinetics to find out the strong evidence for the influence of electrostatic and intercalating forces which enhance the DNA separation efficiency. The modified magnetic nanoparticles (MNPs) were characterized using TEM, SQUID, Zeta potential and FTIR. The maximum adsorption capacity of acridine orange modified MNPs using the 6-bromohexanoic acid as the spacer for plasmid DNA was found to be 181.1 μg mg−1. The addition of 0.5 M CaCl2 in the solution could further enhance the adsorption capacity to 335.8 μg mg−1. The adsorption isotherms and kinetics fitted well to the Langmuir model and the pseudo-first-order model. The acridine orange modified MNPs exhibited very short equilibrium time (2 min) for the adsorption of plasmid DNA and salmon sperm DNA. The facile method could facilitate the development of simple and fast separation of nucleic acid.

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