Selective, Agglomerate-Free Separation of Bacteria Using Biofunctionalized, Magnetic Janus Nanoparticles

This study presents a scalable method for designing magnetic Janus nanoparticles, which are capable of performing bacterial capture, while preventing agglomeration between bacterial cells. To this end, we prepared silica-coated magnetite Janus nanoparticles functionalized with a bacteria-specific antibody on one side and polyethylene glycol chains on the other, using the established wax-in-water emulsion strategy. These magnetic Janus nanoparticles specifically interact with one type of bacteria from a mixture of bacteria via specific antigen–antibody interactions. Contrarily to bacterial capture with isotropically functionalized particles, the bacterial suspensions remain free from cell–nanoparticle–cell agglomerates, owing to the passivation coating with polyethylene glycol chains attached to the half of the magnetic nanoparticles pointing away from the bacterial surface after capture. The selective magnetic capture of Escherichia coli cells was achieved from a mixture with Staphylococcus simulans without compromising bacterial viability and with an efficiency over 80%. This approach is a promising method for rapid and agglomeration-free separation of live bacteria for identification, enrichment, and cell counting of bacteria from biological samples.