Electrical detection and analysis of exosomes by a glass capillary nanopore.

Abstract

An exosome is a vesicle less than 200 nm in diameter released from a cell and works as a medium for cell-to-cell communication. It is suggested that compositions of encapsulated molecules in exosomes have diversity even from a same cell. Single-particle analysis will be insight into the understanding the diversity, but it is still challenging. Nanopore technology will have a potential to detect and to capture single exosomes because it can discriminate nanoparticle properties including size, shape, and surface properties such as the charge by observation of ionic current change through a nano-sized pore. Here, we proposed to use a glass capillary nanopore (φ∼200 nm) and attempt to capture milk exosomes. Exosomes used in this study were extracted from cow milk using a procedure proposed previously. The particle sizes were confirmed by dynamic light scattering (DLS). A glass capillary nanopore was prepared by a puller. We observed the pore diameter of the capillaries by a scanning electron microscope (SEM). In the nanopore experiments, a glass capillary was filled with and immersed in PBS solution to measure I-V curve for checking the pore conductance, and then it was replaced in the exosome solution to detect the exosomes. The size of extracted exosomes was confirmed by DLS, and it was consistent with that in a previous study (∼130 nm). The outer diameter of the glass nanopores ranged from about 100 to 500 nm determined by SEM observation. For channel current measurement, the current blockages were observed in the presence of exosomes that was depended on the polarity of the applying voltages. We are conducting identification of microRNA encapsulated in exosomes collected from the nanopore by RT-qPCR, and it will be discussed in San Diego.