In Situ Measuring Partition Coefficient at Intact Nanoemulsions: A New Application of Single-Entity Electrochemistry

Abstract

We report a new application of the single-entity electrochemistry (SEE) to in situ measure a partition coefficient at intact nanoemulsions (NEs). The partition coefficient at intact NEs is the most crucial physicochemical property to determine the uptake of delivery molecules inside NEs. It, however, has not been unequivocally elucidated by currently existing techniques based on ex situ measurements. Herein, we apply the single-entity electrochemistry (SEE) to directly and quantitatively measure the partition coefficient at NEs in situ. In this work, we use NEs featured with amphiphilic triblock copolymer (Pluronic F-127) as a model system to extract/preconcentrate 2-aminobiphenyl (2-ABP) dissolved in the water and demonstrate a new application of SEE to in situ quantitatively estimate the amounts of 2-ABP distributed into each intact NE. Our SEE measurements reveal that the partitioning is governed by extraction of 2-ABP inside NEs rather than its adsorption on the NE surface, and this extraction is remarkably efficient with up to ∼8 orders of magnitude of the preconcentration factor, thus leading to the unprecedentedly large partition coefficient of 1.9 (±1.4) × 1010. This result implies that not only the thermodynamic distribution but also the intermolecular interaction of extracted compounds inside NEs could play a significant role in the apparent partition coefficient (P = 1.9 (±1.4) × 1010). The experimentally determined partition coefficient was validated by molecular dynamics (MD) simulations with showing a stabilizing role of intermolecular interaction in the partitioned system. We further verified our methodology with other compounds exhibiting aromatic properties, e.g., ferrocenemethanol. Significantly, our new approach can be readily applicable to investigate practical NEs commercially marketed for drug, food, and cosmetics.

Temporally Resolved Electrochemical Interrogation for Stochastic Collision Dynamics of Electrogenerated Single Polybromide Droplets

“…As described in previous reports, ,, a PBIL droplet is not a closed system; i.e., Br – transfers at an interface between an aqueous and PBIL phase. Therefore, it would be more reasonable to be considered that a collisional contact of a PBIL droplet on an electrode with a biased electrochemical potential induces Br – electrolysis not only inside the droplet but at its surrounding.…”

Nanoelectrochemistry at liquid/liquid interfaces for analytical, biological, and material applications

“…13A). 138,139 Pluronic F-127 functionalized NEs were employed to extract and preconcentrate target analytes, e.g., ferrocenemethanol and 2-aminobiphenyl (2-ABP) as a model of ubiquitous aromatic-toxicants dissolved in water. The in situ detection and quantitative estimation of analytes extracted in individual NEs were made via the oxidation of extracted analytes upon NE collision onto a Pt UME.…”

“…The diameter of NEs studied by single-entity electrochemistry is usually larger than 100 nm but can be as small as 40 nm. [137][138][139] Experimentally, either a smaller nanopipet or a smaller NE requires the measurement of lower current, which is eventually limited by the shot noise to B2000 electrons for a given temporal resolution. 150 This limitation was discussed in the recent study of K + transport by single valinomycin molecules through the bilayer lipid membrane.…”

Mass Transfer from Ion-Sensing Component-Loaded Nanoemulsions into Ion-Selective Membranes: An Electrochemical Quartz Crystal Microbalance and Thin-Film Coulometry Study

“…In mechanism (c), the transfer across three phases (NE−water−membrane) is considered where the interaction with the aqueous phase will modulate the transfer rate. 9 Methods to study the transfer mechanism of emulsions include HPLC, 12 optical measurements, 11 and electrochemistry, 13 which rarely focus on studying the mass transfer of molecules across three phases in real time. This work describes our efforts to introduce a new technique to achieve this.…”

“…Methods to study the transfer mechanism of emulsions include HPLC, optical measurements, and electrochemistry, which rarely focus on studying the mass transfer of molecules across three phases in real time. This work describes our efforts to introduce a new technique to achieve this.…”