Magnetic nanogels (MNGs) are designed with the necessary features to function as highly efficient trapping materials for the challenging task of selectively capturing circulating tumor cells (CTCs) from the bloodstream. A key factor in this process is the ability to discriminate CTCs from hematological cells, which can be optimized by finely tuning the polymers used to link the targeting moiety to the MNGs.

Here, we describe the relationship between the capturing efficiency of CTCs with overexpressed transferrin receptors and the different strategies used in polymer linkers to decorate these MNGs with transferrin (Tf). Heterobifunctional polyethylene glycol (PEG) linkers with varying molecular weights were coupled to transferrin in different ratios.

Optimal results, with over 80% CTC capture efficiency, were obtained when three PEG linkers with a length of eight ethylene glycol (EG) units were used. These findings highlight the crucial role of linker design in developing efficient CTC-sorting systems.