Surfactant-free suspension polymerization of hydrophilic monomers with an oil-in-water system for the preparation of microparticles toward the selective isolation of tumor cells

Circulating tumor cells (CTCs) are derived from a primary tumor or monastic foci, and are found in the bloodstream of patients with tumors. We developed polymer droplets of blood-compatible poly(2-methoxyethyl acrylate) (PMEA) that selectively accumulate in tumor cells. PMEA microparticles, which are larger than the size of cells, have potential as a platform for CTC capture devices without the need to use antibodies. Herein, these microparticles, as well as several, other types of microparticles composed of hydrophilic monomers, were prepared by surfactant-free suspension polymerization, and their selective isolation abilities toward the capture of tumor cells were evaluated via comparative studies. The microparticles possessed smooth and extremely pure surfaces suitable for evaluating the interaction force with tumor cells. The number of human platelets adhered to the PMEA microparticles was clearly lower than the number of platelets adhered to the other polymer microparticles. Interestingly, the PMEA microparticles prepared with a 1% crosslinking ratio showed stronger interactions with tumor cells than the other polymer microparticles. In addition, the PMEA microparticles enabled the efficient recovery of tumor cells from cell suspensions under dynamic conditions in comparison with the other polymer microparticles. These results provide insights into the possible applicability of PMEA microparticles as a platform for CTC capture without using antibodies.