Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h(-1) . Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce ), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications.

Here, we describe a versatile application of a planar Halbach permanent magnet array for an efficient long-range magnetic separation of living cells and microparticles over distances up to 30 mm. A Halbach array was constructed from rectangular bar magnets using 3D-printed holders and compared to a conventional alternating array of identical magnets. We theoretically predicted the superiority of the Halbach array for a long-range magnetic separation and then experimentally validated that the Halbach configuration outperforms the alternating array for isolating magnetic microparticles or microparticle-bound bacterial cells at longer distances. Magnetophoretic velocities (ymag) of magnetic particles (7.9 μm diameter) induced by the Halbach array in a microfluidic device were significantly higher and extended over a larger area than those induced by the alternating magnet array (ymag = 178 versus 0 μm/s at 10 mm, respectively). When applied to 50 ml tubes (∼30 mm diameter), the Halbach array removed >95% of Staphylococcus aureus bacterial cells bound with 1 μm magnetic particles compared to ∼70% removed using the alternating array. In addition, the Halbach array enabled manipulation of 1 μm magnetic beads in a deep 96-well plate for ELISA applications, which was not possible with the conventional magnet arrays. Our analysis demonstrates the utility of the Halbach array for the future design of devices for high-throughput magnetic separations of cells, molecules, and toxins.

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Tumor cells circulating throughout the body have shown great potential for providing new diagnostic or therapeutic strategies for treating cancer patients. However, isolating circulating tumor cells (CTCs) is still challenging due to the lack of broad spectrum reagents that bind specifically to these cells. This study shows that an engineered human blood opsonin that mimics the innate immune mechanism for opsonizing complex mannan carbohydrates, Fc‐mannose binding lectin (FcMBL), exhibits a broad spectrum of CTC binding activity. Using FcMBL‐coated magnetic beads, this study is able to specifically capture and isolate a broad range of tumor cells spiked into buffer or blood. FcMBL is bound preferentially to human and mouse breast cancer cells relative to normal breast epithelium, and this study demonstrates the capture of seven different types of cancer cells with greater than 90% capture efficiency, whereas two of these same cancer cells bound poorly to anti epithelial cell adhesion molecule antibodies. It is also confirmed that FcMBL‐coated magnetic beads can be used to capture CTCs from the blood of mice bearing metastatic tumors. The FcMBL capture technology may therefore provide a new tool for harvesting a broad range of CTCs with high efficiency as it targets tumor cell specific surface markers that are expressed across diverse cell types and retained throughout the metastatic process.

Flaviviruses are enveloped, positive-strand RNA viruses that cause millions of infections in the human population annually. Although Zika virus (ZIKV) had been detected in humans as early as the 1950s, its reemergence in South America in 2015 resulted in a global health crisis. While flaviviruses encode 10 proteins that can be post-translationally modified by host enzymes, little is known regarding post-translational modifications (PTMs) of the flavivirus proteome. We used mass spectrometry to comprehensively identify host-driven PTMs on the ZIKV proteome. This approach allowed us to identify 43 PTMs across 8 ZIKV proteins, including several that are highly conserved within the Flavivirus genus. Notably, we found two phosphosites on the ZIKV envelope protein that are functionally important for viral propagation and appear to regulate viral budding. Additionally, we discovered 115 host kinases that interacted with ZIKV proteins and determined that Bosutinib, an FDA-approved tyrosine kinase inhibitor that targets ZIKV interacting host kinases, impairs ZIKV growth. Thus, we have defined a high-resolution map of host-driven PTMs on ZIKV proteins as well as cellular interacting kinases, uncovered a novel mechanism of host driven-regulation of ZIKV budding, and identified an FDA-approved inhibitor of ZIKV growth.