Avoiding Pre-Isolation Step in Exosome Analysis: Direct Isolation and Sensitive Detection of Exosomes Using Gold-Loaded Nanoporous Ferric Oxide Nanozymes

Anal Chem. 2019 Mar 19;91(6):3827-3834. doi: 10.1021/acs.analchem.8b03619. Epub 2019 Feb 25.

Abstract

Most of the current exosome-analysis strategies are time-consuming and largely dependent on commercial extraction kit-based preisolation step, which requires extensive sample manipulations, costly isolation kits, reagents, tedious procedures, and sophisticated equipment and is prone to bias/artifacts. Herein we introduce a simple method for direct isolation and subsequent detection of a specific population of exosomes using an engineered superparamagnetic material with multifunctional properties, namely, gold-loaded ferric oxide nanocubes (Au-NPFe2O3NC). In this method, the Au-NPFe2O3NC were initially functionalized with a generic tetraspanin (exosomes-associated) antibody (i.e., CD63) and dispersed in sample fluids where they work as "dispersible nanocarriers" to capture the bulk population of exosomes. After magnetic collection and purification, Au-NPFe2O3NC-bound exosomes were transferred to the tissue-specific, antibody-modified, screen-printed electrode. As a proof of principle, we used a specific placental marker, placenta alkaline phosphatase (PLAP), to detect exosomes secreted from placental cells. The peroxidase-like activity of Au-NPFe2O3NC was then used to accomplish an enzyme-linked immunosorbent assay (ELISA)-based sensing protocol for naked-eye observation along with UV-visible and electrochemical detection of PLAP-specific exosomes present in placental cell-conditioned media. We demonstrated excellent agreement in analytical performance for the detection of placental cell-derived exosomes (i.e., linear dynamic range, 103-107 exosomes/mL; limit of detection, 103 exosomes/mL; relative standard deviation (%RSD) of <5.5% for n = 3) using with and without commercial "total exosome isolation kit"-based preisolation step. We envisage that this highly sensitive, rapid, and inexpensive assay could be useful in quantifying specific populations of exosomes for various clinical applications, focusing on pregnancy complications.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaline Phosphatase / metabolism*
  • Biosensing Techniques / methods*
  • Cell Line, Tumor
  • Exosomes / metabolism*
  • Female
  • Ferric Compounds / chemistry*
  • Gold / chemistry*
  • Humans
  • Limit of Detection*
  • Nanopores*
  • Placenta / enzymology
  • Pregnancy

Substances

  • Ferric Compounds
  • ferric oxide
  • Gold
  • Alkaline Phosphatase