A magnetic nanoparticle-based microfluidic device fabricated using a 3D-printed mould for separation of Escherichia...

Herein, A microfluidic device is described, produced with a 3D-printed master mould that rapidly separates and concentrates Escherichia coli directly from whole blood samples, enabling a reduction in the turnaround time of bloodstream infections (BSIs) diagnosis. Moreover, it promotes the cleansing of the blood samples whose complexity frequently hampers bacterial detection. The device comprises a serpentine mixing channel with two inlets, one for blood samples (spiked with bacteria) and the other for magnetic nanoparticles (MNPs) functionalized with a (bacterio)phage receptor-binding protein (RBP) with high specificity for E. coli. After the magnetic labelling of bacteria throughout the serpentine, the microchannel ends with a trapping reservoir where bacteria-MNPs conjugates are concentrated using a permanent magnet. The optimized sample preparation device successfully recovered E. coli (on average, 66%) from tenfold diluted blood spiked within a wide range of bacterial load (10² CFU to 10⁷ CFU mL^-1). The non-specific trapping, tested with Staphylococcus aureus, was at a negligible level of 12%. The assay was performed in 30 min directly from diluted blood thus presenting an advantage over the conventional enrichment in blood cultures (BCs). The device is simple and cheap to fabricate and can be tailored for multiple bacterial separation from complex clinical samples by using RBPs targeting different species. Moreover, the possibility to integrate a biosensing element to detect bacteria on-site can provide a reliable, fast, and cost-effective point-of-care device.