Bacteria capture, lysate clearance, and plasmid DNA extraction using pH-sensitive multifunctional magnetic nanoparticles.

A multifunctional magnetic nanoparticle (MNP)-assisted bioseparation method was developed to isolate plasmid DNA (pDNA) from Escherichia coli culture. Using the pH-sensitive carboxyl-modified magnetic nanoparticles, both cell capture and the subsequent removal of genomic DNA/protein complex after lysis can be achieved simply by magnetic separation. Furthermore, the yield and purity of pDNA extracted by MNPs are comparable to those obtained using organic solvents or commercial kits. This time- and cost-effective protocol does not require centrifugation or precipitation steps and has the potential for automated DNA extraction, especially within miniaturized lab chip applications. Copyright 2009 Elsevier Inc. All rights reserved.