Probing Dynamic Events of Dielectric Nanoparticles by a Nanoelectrode‐Nanopore Nanopipette

Abstract

In recent years, various single-entity electrochemical methods have been developed to study the dynamic events of single nanoparticles (NPs) in solution. It has been demonstrated that the assembly, transport, and translocation of metallic NPs near a nanopore entrance can be detected based on the open-circuit potential change of a floating nanoelectrode placed near the nanopore. In this study, we applied the nanopore-nanoelectrode-based method to study polystyrene (PS) NPs with various sizes, which were used as the model dielectric NPs. Furthermore, by utilizing dielectrophoretic (DEP) force applied through the nanoelectrode, PS NPs can be efficiently preconcentrated to form large assemblies outside the nanopipette tip, enabling high-throughput single NP analysis. We revealed how the interactions between NPs and between the NP and the nanopore surface affected the current and potential signals. We investigated the dynamic structures and motions of PS NPs inside the large assembly based on the complementary and correlated the ionic current and potential signals from both the nanopore and the nanoelectrode. We also compared the difference in the dynamic events between polarizable metallic NPs and non-polarizable dielectric NPs during multi-NP structure formation and individual NP transport and translocation motions.

Single-Entity Approach to Investigate Surface Charge Enhancement in Magnetoelectric Nanoparticles Induced by AC Magnetic Field Stimulation

“…These transient changes are due to the interactions between NPs and the nanopipette apex, and most are at a single-NP level. 40 As illustrated in Figure 1d, two types of NP−nanopipette interaction events may be observed: (i) translocation through the nanopore and (ii) collision near the CNE surface.…”

“…37,38 Here, we are demonstrating the detection of surface charge enhancement of individual MENPs under AC B-field through collision events of MENPs at the carbon nanoelectrode (CNE) of a nanopore−nanoelectrode nanopipette. 40,41 The collision events of individual NPs at the CNE are detected by an opencircuit potential (OCP) detection method, which has been validated using gold NPs and polystyrene NPs. 41 The AC Bfield stimulation is generated by electromagnetic coils.…”

Development of multifunctional nanopipettes for controlled intracellular delivery and single-entity detection

“…The uniformly distributed transient signals indicate the buildup of GNPs inside the nanopore barrel near the orifice. 62 Due to the strong electrostatic repulsion between the negatively charged GNPs and the silica surface near the nanopore mouth, the motion of the exiting GNPs is slowed down, which is beneficial for the single-entity detection. In general, ∼75% (7 of 9 attempts) of the GNP delivery in the 10 mM PBS bath show highly correlated current and potential changes.…”

“…This is different from the mainly downward peak shape for the negatively charged NPs at a low salt concentration. 53,62 Here, the biphasic shape is mainly due to the resistive changes induced by the NP translocation motion. The charge sensing mechanism-based potential detection becomes minor at a high salt concentration.…”

Detection of small-sized DNA fragments in a glassy nanopore by utilization of CRISPR-Cas12a as a converter system

“…In order to achieve the capability of detecting small-sized target molecules, strategies comprising the functionalization of the nanopore with DNA nanostructures or other molecules have been proposed. 25,28,33,35 Other methods employ indirect transduction strategies via modifying the nanopores to enhance the interactions between the small analytes and the nanopores. However, those methods all require the use of small pore sizes matched with small-sized target molecules.…”