Exosomes as cell-derived vesicles have the potential to be novel biomarkers for noninvasive diagnosis of cancers. However, cost-effective detection of exosomes in routine clinical settings is still challenging. Researchers at Wuhan University, have developed a ZnO nanowires coated three-dimensional (3D) scaffold chip device for effective immunocapture and classically visible and colorimetric detection of exosomes. The chip device is composed of 3D polydimethylsiloxane (PDMS) scaffold skeleton covered by free-standing ZnO nanowire array. The interconnected micropores of 3D scaffold induces the fluid flow with chaotic or vortex feature, and ZnO nanowire array provides large surface area for immobilization of exosome specific antibody as well as size exclusion-like effect for retaining exosomes. These synergistically and significantly enhance the capture of exosomes at a high flow rate. The captured exosomes are detected by horseradish peroxidase (HRP) labeled antibody which can initiate 3,3′,5,5′-tetramethylbenzidine (TMB)-based colorimetric sensing. The quantitative readout of exosomes is easily accomplished by UV-vis spectrometry or microplate reader with a linear range of 2.2 × 105 to 2.4 × 107 particles/μL and a minimal detectable concentration of 2.2 × 104 particles/μL.
This chip device was applicable to clinical samples where cancer patients demonstrate statistically significant increase in exosomes compared with healthy individuals. Thus, this chip device is cost-effective and easy-to-use, facilitating visible and colorimetric assay with high sensitivity toward clinical applications.