Portable Sensor for the Detection of Choline and Its Derivatives Based on Silica Isoporous Membrane and Gellified Nanointerfaces

Abstract

A portable amperometric ion sensor was fabricated by integrating silica isoporous membrane (SIM) and organogel composed of polyvinyl chloride and 1,2-dichloroethane (PVC-DCE) on a 3D-printed polymer chip. The detection of ionic species in aqueous samples could be accomplished by adding a microliter of sample droplet to the sensor and by identifying the ion-transfer potential and current magnitude at the water/organogel interface array templated by SIM. Thanks to the ultrasmall channel size (2-3 nm in diameter), high channel density (4 × 10 μm), and ultrathin thickness (80 nm) of SIM, the ensemble of nanoscopic water/organogel (nano-W/Gel) interface array behaved like a microinterface with two back-to-back hemispherical mass diffusion zones. So, the heterogeneous ion-transfer across the nano-W/Gel interface array generated a steady-state sigmoidal current wave. The detection of choline (Ch) and its derivatives, including acetylcholine (ACh), benzoylcholine (BCh), and atropine (AP), in aqueous samples was examined with this portable sensor. Using differential pulse stripping voltammetry (DPSV), the quantification of these analytes was achieved with a limit of detection (LOD) down to 1 μM. Moreover, the portable ion sensor was insensitive to various potential interferents that might coexist in vivo, owing to size-/charge-based selectivity and antifouling capacity of SIM. With this priority, the portable ion sensor was able to quantitatively determine Ch and its derivatives in diluted urine and blood samples. The LODs for Ch, ACh, AP, and BCh in urine were 1.12, 1.30, 1.08, and 0.99 μM, and those for blood samples were 3.61, 3.38, 2.32, and 1.81 μM, respectively.

Ion transfer at polarised liquid-liquid interfaces modified with adsorbed silica nanoparticles

“…Micro-ITIES arrays were also modified with mesoporous silica channels prepared ex-situ by a Stöber-like method [36]. The vertically aligned channels obtained have demonstrated their potential for analytical applications [37][38][39][40]. We investigated here the adsorption of silica nanoparticles onto the ITIES and their impact on the electrochemical transfer behaviour of ions (e.g.…”

Fused Silica Microcapillaries Used for a Simple Miniaturization of the Electrified Liquid–Liquid Interface

“…In some cases, ITIES was supported with ex situ or in situ prepared mesoporous membranes. 3 , 13 , 14 Commonly used methodology for nano- or microITIES preparation covers single 15 − 17 or double barrel 18 capillary pulling followed by its interior (adapted to the organic phase) or exterior (adapted to the aqueous phase) surface silanization. Laser ablation is another method allowing for patterned membrane preparation.…”

“…Electrochemical sensing at the interface between two immiscible electrolyte solutions (ITIES) is not restricted to oxidation/reduction reactions but can also arise from ionic currents traversing the immiscible junction. − Such a unique property can be extended to detect molecules which are considered as nonactive or difficult to detect at conventional solid electrodes . Moreover, the potential depended partitioning of ions is directly related to their chemical structure and hence opens new avenues for their selective discrimination.…”

Decorating soft electrified interfaces: From molecular assemblies to nano-objects

“…Ex-situ prepared silica isoporous film supported on micropatterned SiN-coated silicon wafers were used to study ion transfer reactions across electrified water -DCE interface [198][199][200].…”