Immuno-modified superparamagnetic nanoparticles via host-guest interactions for high-purity capture and mild release of exosomes

The study of exosomes has great significance for cancer diagnosis and prognosis, in which damage-free isolation of exosomes is a critically important step due to their extremely low concentration in body fluids. Herein, immunoaffinitive superparamagnetic nanoparticles (IS-NPs) were successfully constructed by combining antibodies with superparamagnetic nanoparticles through host-guest interactions between beta-cyclodextrin (beta-CD) and 4-aminoazobenzene (AAB). Exosomes in cell-culture supernatants or body fluids can be efficiently captured by IS-NPs and then mildly eluted by competitive host molecules, alpha-CD. Approximately 80% of the exosomes were captured by the IS-NPs from the model samples containing varied concentrations of exosomes (10(11)-10(7) exosomes per mL). After elution, the release efficiency of the captured exosomes was as high as 86.5%, as calculated from the extracted RNA content. A comparison between the exosomes isolated by our IS-NPs, conventional ultracentrifugation (UC), polyethylene glycol (PEG)-based precipitation, and a commercial kit was conducted to examine the performance of the IS-NP exosome isolation. The particle-to-protein ratio of IS-NP captured exosomes (8.8 +/- 1.3 x 10(9)) was eight-fold higher than that of the UC (1.1 +/- 0.4 x 10(9)) and more than two-fold that of the PEG-based precipitation (3.7 +/- 0.8 x 10(9)) and commercial kit (3.2 +/- 0.8 x 10(9)) isolated ones, revealing that IS-NPs yielded more exosomes with higher purity than all the other three approaches. Cellular uptake experiments demonstrated that the exosomes captured by IS-NPs have retained their structural and functional integrities, and their broad applications in biomedical areas could therefore be expected. Promisingly, this host-guest interaction involving immunoaffinity magnetic particle system could offer a new way for fast, high-efficiency and high-purity exosome isolation and elution, further benefitting exosomes' applications in desired areas.