Magnetic nanoparticles tethered with Zn–DPA for the removal of bacteria from red blood cell suspension

Bacterial infections continue to drive the need for more effective and rapid methods for bacterial analysis. To address this, magnetic nanoparticles (MNPs) have emerged as promising tools, especially when their surfaces are modified with bacteria binders. The bis-zinc-dipicolylamine (Zn-DPA) complex is known for its broad affinity to bacteria. We have synthesized MNPs <i>via</i> a thermal decomposition method, encapsulated them in silica, modified their surface with Zn-DPA, and tested their ability to remove bacteria. The MNPs retain their superparamagnetic properties and crystallite structure after being encapsulated. The MNPs coated with silica and Zn-DPA effectively bind and remove both Gram-positive and Gram-negative bacteria from bacterial suspensions in both PBS buffer and red blood cell suspension. The capture efficiency (CE) of bacteria is high, >0.95 for both concentrated (1 × 10⁸ CFU) and dilute (1 × 10³ CFU) suspensions of Gram-positive and Gram-negative bacteria in PBS. The bacterial capture efficiency in red blood cell suspension with 50% hematocrit ranges is high (CE > 0.95) for both concentrated and dilute suspensions of <i>S. aureus</i> but lower for concentrated (CE = 0.30) and dilute (CE = 0.15) suspensions of <i>E. coli</i>. The Zn-DPA coated MNPs have promising binding efficiencies for a broad-spectrum of bacteria within a short period of time, potentially leading to applications in diagnostic devices for both medical and industrial uses.