Determination of indole-3-acetic acid using disposable molecularly imprinted electrochemical sensors based on bifunctional monomers.

Stainless steel sheets were coated with carbon ink to obtain disposable carbon electrodes, which were used as supports for moleculary imprinted polymer (MIP) electrochemical sensors by electropolymerizing o-phenylenediamine and o-aminophenol along with indole-3-acetic acid (IAA) as the template. After optimization, the MIP biosensors could be used for sensitive and selective detection of IAA with the limit of quantification of 0.1 µM.

CS/PVP Hydrogel-Based Nanocapillary for Monitoring Bacterial Growth and Rapid Antibiotic Susceptibility Testing.

Infection with drug-resistant bacteria poses a significant threat to human health. Judicious use of antibiotics could reduce the likelihood of bacterial resistance, which can be evaluated through antibiotic susceptibility testing (AST). This paper focuses on the application of a needle-like nanocapillary tip filled with chitosan (CS)/polyethylene pyrrolidone (PVP) hydrogel based on its specific pH-sensitive properties.

Sensitive electrochemical flow injection analysis of HO released from cells with a pass-through mode.

Conventional plate electrodes were commonly used in electrochemical flow injection analysis and only part of molecules diffused to the plane of electrodes could be detected, which would limit the performance of electrochemical detection. In this study, a low-cost native stainless steel wire mesh (SSWM) electrode was integrated into a 3D-printed device for electrochemical flow injection analysis with a pass-through mode, which is different compared with previous flow-through mode. This strategy was applied for sensitive analysis of hydrogen peroxide (HO) released from cells.

A Bifunctional Wearable Sensor Based on a Nanoporous Membrane for Simultaneous Detection of Sweat Lactate and Temperature.

Wearable sensors for non-invasive, real-time detection of sweat lactate have far-reaching implications in the fields of health care and exercise physiological responses. Here, we propose a wearable electrochemical sensor with gold nanoelectrode arrays fabricated on the nanoporous polycarbonate (PC) membrane by encapsulating lactate oxidase (LO) in chitosan (CS) hydrogel for detecting body temperature and sweat lactate concurrently. Flexible gold nanoporous electrodes not only enhance electrode area but also offer a nanoconfined space to accelerate the catalytic reaction of LO and control substrate concentration on the surface of LO to decrease substrate inhibition.

An Ultrasensitive and Efficient microRNA Nanosensor Empowered by the CRISPR/Cas Confined in a Nanopore.

This work presents a clustered regularly interspaced short palindromic repeat (CRISPR)/Cas-nanopipette nano-electrochemistry (Cas = CRISPR-associated proteins) capable of ultrasensitive microRNA detection. Nanoconfinement of the CRISPR/Cas13a within a nanopipette leads to a high catalytic efficacy of ca. 169 times higher than that in bulk electrolyte, contributing to the amplified electrochemical responses.

Vibration-enhanced disposable electroanalytical platform for selective analysis of tryptophan in fruits based on molecular imprinting.

Although electrochemical detection based on molecular imprinting polymers (MIP) could dramatically improve the selectivity, the procedure is time-consuming because of the essential incubation step. In addition, current MIP electrochemical detections were not suitable for analysis of microliter-level sample solutions, limiting their applications for real samples. This investigation aims at applying vibration to enhance efficiency of MIP electrochemical detection of 20 μL sample solutions.

Janus Metal-Organic Framework Membranes Boosting the Osmotic Energy Harvesting.

The unique ion-transport properties in nanoconfined pores enable nanofluidic devices with great potential in harvesting osmotic energy. The energy conversion performance could be significantly improved by the precise regulation of the "permeability-selectivity" trade-off and the ion concentration polarization effect. Here, we take the advantage of electrodeposition technique to fabricate a Janus metal-organic framework (J-MOF) membrane that possesses rapid ion-transport capability and impeccable ion selectivity.

Construction and Evaluation of Zeolitic Imidazolate Framework-Encapsulated Hemoglobin Microparticles as Oxygen Carriers.

Artificial oxygen carriers, such as favorably hemoglobin-based oxygen carriers, have received considerable attention due to some drawbacks of human donor blood. Among all oxygen carriers, the metal organic framework (MOF) exhibits excellent oxygen-carrying capacity due to its good encapsulation efficiency and competitive biocompatibility. Recently, zeolitic imidazolate frameworks (ZIFs) with unique structure have attracted much attention due to their outstanding solvothermal stability.

Rational design of mesoporous chiral MOFs as reactive pockets in nanochannels for enzyme-free identification of monosaccharide enantiomers.

Monosaccharides play significant roles in daily metabolism in living organisms. Although various devices have been constructed for monosaccharide identification, most rely on the specificity of the natural enzyme. Herein, inspired by natural ionic channels, an asymmetrical MOF-in-nanochannel architecture is developed to discriminate monosaccharide enantiomers based on cascade reactions by combining oxidase-mimicking and Fenton-like catalysis in homochiral mesoporous CuMOF pockets.

Locally superengineered cascade recognition-quantification zones in nanochannels for sensitive enantiomer identification.

As an intriguing and intrinsic feature of life, chirality is highly associated with many significant biological processes. Simultaneous recognition and quantification of enantiomers remains a major challenge. Here, a sensitive enantiomer identification device is developed on TiO nanochannels the design of cascade recognition-quantification zones along the nanochannels.

Synergistic Effect of Electrostatic Interaction and Ionic Dehydration on Asymmetric Ion Transport in Nanochannel/Ion Channel Composite Membrane.

Ion transport in nanochannels of a size comparable to that of hydrated ions exhibits unique properties due to the synergistic effect of various forces. Here, we design a nanochannel/ion channel composite (NIC) membrane that shows a high ion current rectification (ICR) ratio in different electrolytes. Experimental and theoretical results demonstrate that the synergistic effect of electrostatic interaction and ionic dehydration plays an important role in regulating the ICR behavior of the NIC membrane.

PNP Nanofluidic Transistor with Actively Tunable Current Response and Ionic Signal Amplification.

Inspired by electronic transistors, electric field gating has been adopted to manipulate ionic currents of smart nanofluidic devices. Here, we report a PNP nanofluidic bipolar junction transistor (nBJT) consisting of one polyaniline (PANI) layer sandwiched between two polyethylene terephthalate (PET) nanoporous membranes. The PNP nBJT exhibits three different responses of currents (quasi-linear, rectification, and sigmoid) due to the counterbalance between surface charge distribution and base voltage applied in the nanofluidic channels; thus, they can be switched by base voltage.

Light-Enhanced Osmotic Energy Harvester Using Photoactive Porphyrin Metal-Organic Framework Membranes.

High ion selectivity and permeability, as two contradictory aspects for the membrane design, highly hamper the development of osmotic energy harvesting technologies. Metal-organic frameworks (MOFs) with ultra-small and high-density pores and functional surface groups show great promise in tackling these problems. Here, we propose a facile and mild cathodic deposition method to directly prepare crack-free porphyrin MOF membranes on a porous anodic aluminum oxide for osmotic energy harvesting.

Electrochemically Switchable Double-Gate Nanofluidic Logic Device as Biomimetic Ion Pumps.

Biological ion pumps with two separate gates can actively transport ions against the concentration gradient. Developing an artificial nanofluidic device with multiple responsive sites is of great importance to improve its controllability over ion transport to further explore its logic function and mimic the biological process. Here, we propose an electrochemical polymerization method to fabricate electrochemically switchable double-gate nanofluidic devices.

Reversible Electrochemical Tuning of Ion Sieving in Coordination Polymers.

Membrane-based ion separation is environmentally friendly, energy-efficient, and easy to integrate, being widely used in water desalination and purification systems. With the existing separation technologies, it is yet difficult to achieve real time, , and reversible control of the separation process. Here, we design and fabricate a Prussian blue (PB) coordination polymer based membrane with uniform and electrochemically size-tunable subnanopores.

Nanocapillary confinement of imidazolium based ionic liquids.

Room temperature ionic liquids are salts which are molten at or around room temperature without any added solvent or solution. In bulk they exhibit glass like dependence of conductivity with temperature as well as coupling of structural and transport properties. Interfaces of ionic liquids have been found to induce structural changes with evidence of long range structural ordering on solid-liquid interfaces spanning length scales of 10-100 nm.

Regulating Ion Transport in a Nanochannel with Tandem and Parallel Structures via Concentration Polarization.

The unique phenomena of ion selectivity and ion current rectification (ICR) in nanofluidics have been widely used to construct bioinspired channels and organs, sensors, and power generators. However, the excellent performance of a single nanochannel does not show a linear increase when it is scaled up into multiple nanochannels in tandem and parallel structure, and in some cases, it even shows a reverse trend. Understanding of this scaling-up inconsistency in nanofluidics is essential to the design of functional devices.

Specific cell capture and noninvasive release via moderate electrochemical oxidation of boronic ester linkage.

Early diagnosis and therapy of cancer metastasis are of great importance for disease outcome. Circulating tumor cells (CTCs) offer the ability for noninvasive tumor profiling in real time. However, simply capturing and counting tumor cells are inadequate to provide valuable information about tumor.

High-performance bioanalysis based on ion concentration polarization of micro-/nanofluidic devices.

Micro-/nanofluidics has received considerable attention over the past two decades, which allows efficient biomolecule trapping and preconcentration due to ion concentration polarization (ICP) within nanostructures. The rich scientific content related to ICP has been widely exploited in different applications including protein concentration, biomolecules sensing and detection, cell analysis, and water purification. Compared to pure microfluidic devices, micro-/nanofluidic devices show a highly efficient sample enrichment capacity and nonlinear electrokinetic flow feature.

Study on the photocatalytic reaction kinetics in a TiO nanoparticles coated microreactor integrated microfluidics device.

For study of the photocatalytic reaction kinetics in a confined microsystem, a photocatalysis microreactor integrated on a microfluidic device has been fabricated using an on-line UV/vis detector. The performance of the photocatalysis microreactor is evaluated by the photocatalytic degradation of Rhodamine B chosen as model target by using commercial titanium dioxide (Degussa P25, TiO) nanoparticles as a photocatalyst. Results show that the photocatalytic reaction occurs via the Langmuir-Hinshelwood mechanism and the photocatalysis kinetics in the confined microsystem (r = 0.

Electrogenerated Chemiluminescence Imaging of Electrocatalysis at a Single Au-Pt Janus Nanoparticle.

Noble metal nanoparticles are promising catalysts in electrochemical reactions, while understanding the relationship between the structure and reactivity of the particles is important to achieve higher efficiency of electrocatalysis, and promote the development of single-molecule electrochemistry. Electrogenerated chemiluminescence (ECL) was employed to image the catalytic oxidation of luminophore at single Au, Pt, and Au-Pt Janus nanoparticles. Compared to the monometal nanoparticles, the Janus particle structure exhibited enhanced ECL intensity and stability, indicating better catalytic efficiency.

Illustrating the Mass-Transport Effect on Enzyme Cascade Reaction Kinetics by Use of a Rotating Ring-Disk Electrode.

Electrochemical biosensors based on enzymatic reaction have been applied to a wide range of fields. As the trend continues to grow, these biosensors are approaching the limit imposed by physics and chemistry. To further improve the performance of biosensors, the interplay of mass transport and enzymatic reaction kinetics, especially in enzyme cascade systems, should be considered in the design of biosensors.

Highly Efficient Capture and Electrochemical Release of Circulating Tumor Cells by Using Aptamers Modified Gold Nanowire Arrays.

The effective capture and release of circulating tumor cells (CTCs) is of significant importance in cancer prognose and treatment. Here we report a highly efficient method to capture and release human leukemic lymphoblasts (CCRF-CEM) using aptamers modified gold nanowire arrays (AuNWs). The gold nanowires, showing tunable morphologies from relatively random pillar deposit to relatively uniform arrays, were fabricated by electrochemical deposition using anodic aluminum oxide (AAO) as template.

Effect of Nanoemitters on Suppressing the Formation of Metal Adduct Ions in Electrospray Ionization Mass Spectrometry.

In the work, we showed that the use of nanoemitters (tip dimension <1 μm, typically ∼100 nm) could dramatically reduce the nonspecific metal adduction to peptide or protein ions as well as improve the matrix tolerance of electrospray ionization mass spectrometry (ESI-MS). The proton-enriched smaller initial droplets are supposed to have played a significant role in suppressing the formation of metal adduct ions in nanoemitters. The proton-enrichment effect in the nanoemitters is related to both the exclusion-enrichment effect (EEE) and the ion concentration polarization effect (ICP effect), which permit the molecular ions to be regulated to protonated ones.