Circulating tumor cells (CTCs) detach from primary tumors and enter circulation, making them dangerous cells of origin for metastasis and the spread of cancer throughout the body. The detection of CTCs in the blood can serve as a biomarker, and cell counts can be a rapid approach to tracking therapeutic efficacy and/or disease progression. However, the isolation of this phenotypically heterogeneous population can prove difficult at low percentages in the blood, particularly when they are outnumbered by other leukocytes. 

 

EpCAM, also known as CD326, has traditionally been found in abundance on CTCs with epithelial cell-like characteristics. In addition, the clinical significance of EpCAM expression was previously established, and there are several commercially available reagents that have been used in techniques to acquire low to medium EpCAM-expressing cells.

 

Characterizing the magnetic beads

 

Given this information, Liu et al. focused on the EpCAM marker and devised an optimized Halbach configuration, a specific arrangement of permanent magnets. This setup used a flow-through immuno-magnetic CTC enrichment system capable of processing large amounts of blood samples obtained from diagnostic leukapheresis. It also utilized an indirect capture system with magnetic beads to improve capture efficiency of EpCAM-expressing CTCs. In order to determine which Streptavidin magnetic beads worked best, they tested reagents available across the industry from companies like BioLegend, Miltenyi Biotec, BioMagnetic, NVIGEN, Bioneer Corporation, Proteintech, Thermo Fisher Scientific, and TriLink Biotechnologies.

 

The researchers investigated several properties of the beads, including the ability of each Streptavidin particle to capture tumor cell lines with varying levels of EpCAM expression. This was represented by PC3-9 and LNCaP cell lines which expressed approximately 19,700 and 628,400 epitopes per cell, respectively. To assess the capture capabilities of the beads, Liu’s assay used magnets to attract the beads in solution to an area of the tube that was magnetized. While moving, the beads had the chance to bind surface antigens on target cells. 

 

For both cell lines, BioLegend's MojoSort™ Streptavidin Nanobeads demonstrated the highest capture efficiency (77% for PC3-9 and 88% for LNCaP) and enrichment factors among the commercially available options. Liu hypothesized that the increased efficiency in the BioLegend beads could be due to their size (~130 nm), stronger magnetization ability, and a higher surface area, which would make biotin binding sites more abundant. Based on capture efficiency, purity, and costs, Liu concluded that the BioLegend Streptavidin Nanobeads had the best overall performance.

 

 

Capture efficiency and purity for magnetic particles from industry vendors for the capture of LNCaP and PC3-9 from blood. (a) The percentage of LNCaP, PC3-9, and WBC (leukocytes) captured by magnetic particles from companies as indicated. (b) A comparison of the purity of isolated LNCaP and PC3-9 cells in the captured aliquots. Columns indicate mean ± SD with a median line. Comparisons were made for capture efficiency versus purity in panels (c) for LNCaP and (d) for PC3-9. 

 

 

A promising method for future therapeutic studies

 

The use of Streptavidin Nanobeads has been shown to be effective in isolating tumor cells with varying levels of EpCAM. In addition, the flexible nature of Streptavidin Nanobeads means they can be used in conjunction with a variety of biotinylated antibodies for other potential tumor targets, such as HER-2 or PMSA. It is paramount for researchers and clinicians to choose beads that demonstrate optimal performance in capture ability, purity, enrichment, and even cost effectiveness. Read the full publication to gain deeper insights into their research, or visit our MojoSort™ webpage to find more information on our Streptavidin Nanobeads, anti-Biotin Nanobeads, and magnetic cell separation systems. 

 

Diagram demonstrating a typical MojoSort cell isolation workflow with handheld magnets.

 

 

Reference

Liu, Peng et al. “Performance comparison of streptavidin magnetic beads for EpCAM expressing cancer cell lines for circulating tumor cell (CTC) enrichment in a flow-through immunomagnetic system.” PloS one vol. 20,5 e0322375. 9 May. 2025, doi:10.1371/journal.pone.0322375