Researchers from Southern Methodist University describes a method to gauge the stiffness of nanosized liposomes – a nanoscale vesicle – using a custom-made recapture platform coupled to a solid-state nanopore sensor. The recapture platform electrically profiles a given liposome vesicle multiple times through automated reversal of the voltage polarity immediately following a translocation instance to re-translocate the same analyte through the nanopore – provides better statistical insight at the molecular level by analyzing the same particle multiple times compared to conventional nanopore platforms. The capture frequency depends on the applied voltage with lower voltages (i.e., 100 mV) permitting higher recapture instances than at higher voltages (>200 mV) since the probability of particles exiting the nanopore capture radius increases with voltage. The shape deformation was inferred by comparing the normalized relative current blockade ( ΔI/I0ˆ) at the two voltage polarities to that of a rigid particle, i.e., polystyrene beads. The researchers found that liposomes deform to adopt a prolate shape at higher voltages. This platform can be further applied to investigate the stiffness of other types of soft matters, e.g., virus, exosomes, endosomes, and accelerate the potential studies in pharmaceutics for increasing the drug packing and unpacking mechanism by controlling the stiffness of the drug vesicles.
Basic nanopore sensor platform
(a) SEM image of the free-standing SixNy membrane; 7070 μm2 window. The membrane was not polished. (b) SEM image of the nanopore after milling 250 nm diameter nanopore on the SixNy membrane. The inset figure is the zoom-in image of the background image. (c) Nanopore resistive pulse sensor platform. The nanopore chip was sandwitched in the flowcell where an electrolyte solution was filled. Headstage probes were inserted in both chambers, and the signal was amplified and digitized with Axopatch 200B and DAQ board in real time.