The purification of plasmid DNA or recombinant protein is fundamental to life science research, but some isolation methods can be physically and chemically damaging. Magnetic separation offers a gentle alternative. Targets are captured on magnetic particles coated with a target-specific surface, and separated from the sample using a magnetic field. Methods: Nanosized superparamagnetic nanoparticles (Fe3O4) were prepared by chemical coprecipitation method using Fe2+, Fe3+ salt, and ammonium hydroxide under a nitrogen atmosphere. A quick and reliable method for the isolation and purification of transfection-grade plasmid DNA has been developed, using PEI-modified magnetic nanobeads as a solid-phase adsorbent. We demonstrated a useful plasmid, pRSETB-EGFP, encoding the green fluorescent protein with T7 promoter, was amplified in DE3 strain of E. coli. A new immobilized metal ion affinity (IMA) adsorbent containing superparamagnetic nanoparticles and coated with hydrophilic resins are also proposed to improve the purification of His-tagged proteins.The GMA-IDA-coated magnetic Fe3O4 were employed for the direct extraction of recombinant protein, EGFP-(His)6, from E. coli lysates as a model system. Results: Up to approximately 819 ?g of high-purity (A260/A280 ratio=1.86) plasmid DNA was isolated from 100 ml of overnight bacterial culture. The eluted plasmid DNA was used directly for restriction enzyme digestion, bacterial cell transformation and animal cell transfection applications with success.The Cu2+-charged GMA-IDA-coated adsorbent had the highest yield and purification factor at 70.4% and 12.3, respectively. Conclusions: 1) PEI-modified magnetic nanobeads deliver significant time-savings, overall higher yields and better transfection efficiencies compared to anion-exchange and other methods. 2) GMA-IDA-coated magnetic adsorbent could be used as a suitable adsorbent for recombinant His-tagged protein from aqueous solution. Results proved that this new protein purification adsorbent provides a fast and efficient method for purifying His-tagged proteins with high yield and low background.

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