Size distribution and concentration measurements of exosomes are essential when investigating their cellular function and uptake. Recently, a particle size distribution and concentration measurement platform known as Tunable Resistive Pulse Sensing (TRPS) has seen increased use for the characterization of exosome samples. TRPS measures the brief increase in electrical resistance (a “resistive pulse”) produced by individual submicron/nanoscale particles as they translocate through a size-tunable submicron/micron-sized pore embedded in an elastic membrane. Unfortunately, TRPS measurements are susceptible to issues surrounding system stability, where the pore can become blocked by particles; and sensitivity issues, where particles are too small to be detected against the background noise of the system. Herein, we provide a comprehensive analysis of the parameters involved in TRPS exosome measurements, and demonstrate the ability to improve system sensitivity and stability by optimization of system parameters. We also provide the first analysis of system noise, sensitivity cutoff limits and accuracy with respect to exosome measurements, and offer an explicit definition of system sensitivity that indicates the smallest particle diameter that can be detected within the noise of the trans-membrane current. A comparison of exosome size measurements from both TRPS and cryo electron microscopy is also provided, finding a significant number of smaller exosomes fell below the detection limit of the TRPS platform and offers one potential insight as to why there is such large variability in exosome the size distribution reported in the literature. We believe the observations reported here may assist others in improving TRPS measurements for exosome samples and other submicron biological and non-biological particles.
Anderson, Will, Rebecca Lane, Darren Korbie, and Matt Trau. "Observations of tunable resistive pulse sensing for exosome analysis: improving system sensitivity and stability." Langmuir 31, no. 23 (2015): 6577-6587.
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