Rapid and simple isolation and detection of exosomes using CaTiO₃:Eu³⁺@Fe₃O₄ multifunctional nanocomposites

Exosomes are potential biomarkers for disease diagnosis and treatment, as well as drug carriers. However, as their isolation and detection remain critical issues, convenient, rapid, low-cost, and effective methods are necessary. In this study, we present a rapid and simple method for directly capturing and analyzing exosomes from complex cell culture media using CaTiO₃:Eu³⁺@Fe₃O₄ multifunctional nanocomposites. The CaTiO₃:Eu³⁺@Fe₃O₄ nanocomposites were prepared by high-energy ball-milling and used to isolate exosomes by binding CaTiO₃:Eu³⁺@Fe₃O₄ nanocomposites and the hydrophilic phosphate head of the exosome phospholipids. Notably, the developed CaTiO₃:Eu³⁺@Fe₃O₄ multifunctional nanocomposites achieved results comparable with those of commercially available TiO₂ and were separated using a magnet within 10 min. Moreover, we report a surface-enhanced Raman scattering (SERS)-based immunoassay for detecting the exosome biomarker CD81. Gold nanorods (Au NRs) were modified with detection antibodies, and antibody-conjugated Au NRs were labeled with 3, 3, diethylthiatricarbocyanine iodide (DTTC) as the SERS tags. A method combining magnetic separation and SERS was developed to detect exosomal biomarker CD81. The results of this study demonstrate the feasibility of this new technique as a useful tool for exosome isolation and detection.