Faradaic Counter for Liposomes Loaded with Potassium, Sodium Ions, or Protonated Dopamine

Abstract

Collisional electrochemistry between single particles and a biomimetic polarized micro-liquid/liquid interface has emerged as a novel and powerful analytical method for measurements of single particles. Using this platform, rapid detection of liposomes at the single particle level is reported herein. Individual potassium, sodium, or protonated dopamine-encapsulated (pristine or protein-decorated) liposomes collide and fuse with the polarized micro-liquid/ liquid interface accompanying the release of ions, which are recorded as spike-like current transients of stochastic nature. The sizing and concentration of the liposomes can be readily estimated by quantifying the amount of encapsulated ions in individual liposomes via integrating each current spike versus time and the spike frequency, respectively. We call this type of nanosensing technology "Faradaic counter". The estimated liposome size distribution by this method is in line with the dynamic light scattering (DLS) measurements, implying that the quantized current spikes are indeed caused by the collisions of individual liposomes. The reported electrochemical sensing technology may become a viable alternative to DLS and other commercial nanoparticle analysis systems, for example, nanoparticle tracking analysis.

Recent advances in single liposome electrochemistry

“…Although the blocking method is an efficient single collision technique for determining the frequency and the height of the current steps during the particle adsorption onto the UME surface [4,14,42,44,45], the reactor method brings more information on the mechanism of the electroporation process and the liposome content release [4,9,15,33,46]. The liposomes size distribution calculated from the charge passed in each current spike (by peak integration) in the i-t curve is a crucial information on the electrolysis process occurring upon impact onto the UME surface.…”

“…The liposomes size distribution calculated from the charge passed in each current spike (by peak integration) in the i-t curve is a crucial information on the electrolysis process occurring upon impact onto the UME surface. In this way, several recent investigations deal with the permeability of the liposomes lipid membrane and the effect of the membrane tension on the liposomes content release based on single impact events [9,15,44,46]. Especially, Zhang et al [9] have found that the liposomes electroporation process and the amount of released ferrocyanide content can be controlled by modifying the osmolarity of the buffer in which the 200 nm diameterliposomes are suspended.…”

“…Furthermore, the development of resistive-pulse sensing method using nanopipettes and nanopore microelectrodes is an efficient strategy for improving control and sensitivity in the redox liposomes single impact electrochemistry [47][48][49]. Nowadays, the trend is to use the versatility of the redox liposomes properties in terms of lipid membrane composition and encapsulated content, added to the sensitivity of the reactor method for extending single vesicle impact electrochemistry to sensing purposes [7,46,50].…”

“…The method using electrochemical single impacts of synthetic redox liposomes is an attractive way for developing highly sensitive sensing strategies, especially because of the possibility to modulate the redox liposomes composition to reach the desired properties [7,46,50]. In contrast, the mechanisms of the membrane electroporation process and the content release at the polarized UME surface are very dependent on the type of used liposomes (composition) and not fully understood yet [9,15,35].…”

Magnetic Rolling Circle Amplification-Assisted Single-Particle Collision Immunosensor for Ultrasensitive Detection of Cardiac Troponin I

“…When a single nanoparticle collides with the microelectrode surface by random Brownian motion, it can generate a transient current by hindering electron transfer and self-reaction or catalyzing electroactive substances. − Each effective collision can produce an independent and distinguishable step or peak current. By measuring the current intensity, frequency, current rise time, or life, the size distribution, agglomeration degree, , concentration, electrocatalytic properties, and other properties of NPs in the solution can be directly analyzed in situ . Lemay et al first proposed blocking SPCE to realize electrochemical characterization and measurement of individual insulating particles, which has been regarded as one of the most attractive nanometer-scale analytical methods .…”