Paramagnetic beads

For magnetic bead solution made from ferromagnetic beads or paramagnetic beads (Spherotech) used in these experiments, the same concentration of solution was prepared by taking 10 μL of 1.0% w/v from each solution followed by washing them twice with phosphate-buffered saline (PBS) and then adding 400 μL of PBS to make a 0.244 mg/mL magnetic bead solution (pH of 7.4).
For the case of super paramagnetic beads (chemicell), 2 μL of 10 mg/mL were used; the same procedure was followed in cleaning but later adding 300 μL PBS to make a 0.067 mg/mL solution.

The permanent magnets 3×3 mm Neodymium N42 were purchased from a local hobby shop; Poly(methyl methacrylate) (PMMA) was purchased from McMaster-Carr (Elmhurst, IL, USA); ferromagnetic beads of 8, 4, and 2 μm in diameter were purchased from Spherotech (Lake Forest, IL, USA); paramagnetic beads of 4 μm in diameter were purchased from Spherotech; and superparamagnetic beads of 1 μm in diameter were purchased from chemicell (Berlin, Germany). Iron nanopowder of 60–80 nm in diameter was purchased from Sigma-Aldrich Co., (St Louis, MO, USA); gram stain was purchased from EMD Millipore (Billerica, MA, USA); gauss meter was purchased from Sypris/FW Bell (Orlando, FL, USA); and magnetic beads for capturing E. coli 0157:H7 were purchased from Lab M Ltd (Heywood, UK).