Self-assembled supramolecular immunomagnetic nanoparticles through π–π stacking strategy for the enrichment of circulating tumor cells

Owing to their high-specific binding toward targets as well as fast and convenient separation operations, immunomagnetic beads (IMBs) are widely used in the capture and detection of circulating tumor cells (CTCs). To construct the IMBs, surface modifications are generally performed to functionalize the magnetic cores (e.g. Fe3O4 nanoparticles), and the employed surface modification strategies normally influence the structure and functions of the prepared IMBs in return. Different from the existing work, we proposed the use of supramolecular layer-by-layer (LBL) self-assembly strategy to construct the IMBs. In general, owing to the π–π stacking interactions, the polydopamine, graphene oxide and ‘molecular glue’ γ-oxo-1-pyrenebutyric acid were self-assembled on Fe3O4 nanoparticles sequentially, thereby accomplishing the integration of different functional components onto magnetic cores to prepare the self-assembled supramolecular immunomagnetic beads (ASIMBs). The ASIMBs showed high sensitivity, specificity and good biocompatibility to the model CTCs and low nonspecific adsorption to the negative cells (∼93% for MCF-7 cells and 17% for Jurkat cells). Meanwhile, ASIMBs possessed a remarkable potential to screen the rare MCF-7 cells out of large amounts of interfering Jurkat cells with the capture efficiency of 75–100% or out of mouse whole blood with the capture efficiency of 20–90%. The captured cells can be further recultured directly without any more treatment, which showed huge applicability of the ASIMBs for in vitro detection in clinical practices.