An Engineered Human Fc-Mannose-Binding-Lectin Captures Circulating Tumor Cells.

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.

Optimization of Pathogen Capture in Flowing Fluids with Magnetic Nanoparticles.

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.