Hedgehog-inspired immunomagnetic beads for high-efficient capture and release of exosomes

Exosomes are small extracellular vesicles secreted by cells. They play an important regulatory role in the physiological and pathological processes of the body, and participate in the occurrence and development of many diseases. Although tumor-derived exosomes have been used as biomarkers for cancer detection, it is still a huge challenge to efficiently capture and release functionally complete exosomes. In our research, inspired by the structure of hedgehog burrs, we proposed immunomagnetic hedgehog particles (IMHPs) to efficiently capture and release exosomes. In general, after the assembly of one-dimensional nanostructural TiO₂ bundles into hedgehog TiO₂ particles with 356.12 ± 38.32 nm spikes, magnetic responsive nanoparticles (Fe₃O₄, ∼20 nm), an antifouling polyethylene glycol (PEG) component containing a redox responsive disulfide linkage and anti-CD63 antibody were introduced stepwise to functionalize hedgehog particles and generate IMHPs (1.23 ± 0.18 μm). Due to their unique topological structures, exosomes were positively selected with an exosomal marker (CD63) and negatively selected by depleting environmental pollutants (protein precipitates, cell debris) with the nano-spikes. These prepared IMHPs were successfully applied to capture exosomes from MCF-7 cells, with a capture efficiency of 91.70%. Then, tris (2-carboxyethyl) phosphine hydrochloride (TCEP) was used to reduce the disulfide bond to release exosomes, and the release efficiency was up to 82.45%. The exosomes that experienced successive immunomagnetic separation and release well maintained their structural integrity and good bioactivity to promote MCF-7 cell migration, as compared with those exosomes separated by the classic ultracentrifugation approach. These results also indicated that IMHPs would have broad prospects in biomedicine and clinical applications, where highly efficient and non-destructive separation of bio-substances (cells, extracellular vesicles, etc.) is critically required.