Interfacial Super-Assembly of Nanofluidic Heterochannels from Layered Graphene and Alumina Oxide Arrays for Label-Free Histamine-Specific Detection

Super-assembled periodic mesoporous organosilica membranes with hierarchical channels for efficient glutathione sensing

Bioinspired nanochannel-based sensors have elicited significant interest because of their excellent sensing performance, and robust mechanical and tunable chemical properties. However, the existing designs face limitations due to material constraints, which hamper broader application possibilities. Herein, a heteromembrane system composed of a periodic mesoporous organosilica (PMO) layer with three-dimensional (3D) network nanochannels is constructed for glutathione (GSH) detection. The unique hierarchical pore architecture provides a large surface area, abundant reaction sites and plentiful interconnected pathways for rapid ionic transport, contributing to efficient and sensitive detection. Moreover, the thioether groups in nanochannels can be selectively cleaved by GSH to generate hydrophilic thiol groups. Benefiting from the increased hydrophilic surface, the proposed sensor achieves efficient GSH detection with a detection limit of 1.2 μM by monitoring the transmembrane ionic current and shows good recovery ranges in fetal bovine serum sample detection. This work paves an avenue for designing and fabricating nanofluidic sensing systems for practical and biosensing applications.

Interfacial Assembly of 2D Graphene-Derived Ion Channels for Water-Based Green Energy Conversion

The utilization of sustained and green energy is believed to alleviate increasing menace of global environmental concerns and energy dilemma. Interfacial assembly of 2D graphene-derived ion channels (2D-GDICs) with tunable ion/fluid transport behavior enables efficient harvesting of renewable green energy from ubiquitous water, especially for osmotic energy harvesting. In this review, various interfacial assembly strategies for fabricating diverse 2D-GDICs are summarized and their ion transport properties are discussed. This review analyzes how particular structure and charge density/distribution of 2D-GDIC can be modulated to minimize internal resistance of ion/fluid transport and enhance energy conversion efficiency, and highlights stimuli-responsive functions and stability of 2D-GDIC and further examines the possibility of integrating 2D-GDIC with other energy conversion systems. Notably, the presented preparation and applications of 2D-GDIC also inspire and guide other 2D materials to fabricate sophisticated ion channels for targeted applications. Finally, potential challenges in this field is analyzed and a prospect to future developments toward high-performance or large-scale real-word applications is offered.

Application of three dimensional-printed devices in extraction technologies

Sample pretreatment is an important and necessary process in chemical analysis. Traditional sample preparation methods normally consume moderate to large quantities of solvents and reagents, are time- and labor-intensive and can be prone to error (since they usually involve multiple steps). In the past quarter century or so, modern sample preparation techniques have evolved, from the advent of solid-phase microextraction and liquid-phase microextraction to the present day where they are now widely applied to extract analytes from simple as well as complex matrices leveraging on their extremely low solvent consumption, high extraction efficiency, generally straightforward and simple operation and integration of most, if not all, of the following aspects: Sampling, cleanup, extraction, preconcentration and ready-to-inject status of the final extract. One of the most interesting features of the progress of microextraction techniques over the years lies in the development of devices, apparatus and tools to facilitate and improve their operations. This review explores the application of a recent material fabrication technology that has been receiving a lot of interest, that of three-dimensional (3D) printing, to the manipulation of microextraction. The review highlights the use of 3D-printed devices in the extraction of various analytes and in different methods to address, and improves upon some current extraction (and microextraction) problems, issues and concerns.

Super-assembled mesoporous thin films with asymmetric nanofluidic channels for sensitive and reversible electrical sensing

Bioinspired artificial nanochannels have emerged as promising candidates for developing smart nanofluidic sensors due to their highly controllable size and surface functionality. However, little attention has been paid to the role of the outer surface of the nanochannels in enhancing the detection sensitivity. Herein, an asymmetric nanochannel-based responsive detection platform with ultrathin tannic acid modified mesoporous silica (TA-MS) layer and alumina oxide (AAO) thin film is prepared through super-assembly strategy. The functional TA-MS outer surface layer provides abundant phenolic groups on the nanochannels for ions and molecules transport, which paves the way for the development of heterochannels for label-free, reversible and highly sensitive dopamine (DA) detection based off of cation displacement effect. Notably, by engineering optimal thickness of the TA-MS, the sensing performance can be further improved. After optimization, the linear response ranges for DA detection are 0.001-1 μM, 1-10 μM and 10-200 μM with the detection limit of 0.1 nM. The prepared sensor exhibits stable reversibility after several detection cycles. In addition, this method was successfully applied for DA detection in fetal bovine serum sample. Theoretical calculations further prove the detection mechanism. This work opens a new horizon of using mesoporous materials to construct nanofluidic sensors for ultrasensitive small molecule detection and recognition.

In Situ Interfacial Super-Assembly of Nanobiohybrids through Plant for Food-Grade Oral Medicine

Developing a next-generation oral drug delivery system with enhanced efficacy and limited side effects is highly desired for refractory diseases treatment such as colitis. The bioinspired assembly of drugs within food-grade plants highlights its potential value of this unique hybrid material. Herein, we report the preparation of drug-encapsulated vegetable nanobiohybrid superassembled frameworks as an oral food-grade drug delivery system (SAF-FGDD). The in situ superassembly of SAF-FGDD driven by natural transpiration from living plants is carried out through a sustainable and low-carbon manner, allowing for the assembly of distinct precursors inside edible living plants. As an example, mesalazine, an anti-inflammatory drug, is encapsulated in the frameworks for colitis treatment. The cell activity and feeding experiments of zebrafish and mice demonstrate the excellent efficacy of this SAF-FGDD. Compared with those of the control groups, the disease activity index scores and histological scores of the SAF-FGDD group were significantly decreased by 80% and 98%, respectively. The improved performance is attributed to the biocompatibility and protective effect of SAF-FGDD, allowing for abundant mesalazine to be released and act at the site of the intestine during the process of food digestion. In combination with mature soilless cultivation technology, plant-based organisms with natural structure-forming abilities possess broad commercial prospects in large-scale production of various food-grade functional materials.

Three-Dimensional Printed Microdevice to Enhance Headspace Microextraction for Enrichment of Histamine in Milk

In this work, a three-dimensional (3D) printed microdevice was designed to fix a drop of extractant that was applied to the enrichment of the most toxic biogenic amine, histamine, by headspace single-drop microextraction (HS-SDME). Concomitantly, based on the hybridization chain reaction of the histamine aptamer isothermal nucleic acid amplification strategy, a new fluorescence sensing method was developed to realize the highly sensitive detection of histamine. This is the first application of a 3D-printed microdevice to realize the HS-SDME process, which, among other advantages, effectively solves the problem of unstable and variable drop volumes that can plague traditional SDME and ensures the accuracy and repeatability of the extraction process. The calibration linear range of this SDME-fluorescence method was from 10 pM to 5 μM (R² > 0.98), and the limit of detection was as low as 3 pM. In addition, the method was successfully demonstrated to determine histamine spiked in milk, with recoveries of between 93% and 104%, and relative standard deviations of less than 5%. The method established in this study has important practical significance for food safety monitoring and human health and provides new ideas and solutions for the design and application of biosensors.

Integrating Ordered Two-Dimensional Covalent Organic Frameworks to Solid-State Nanofluidic Channels for Ultrafast and Sensitive Detection of Mercury

Grafting specific recognition moieties onto solid-state nanofluidic channels is a promising way for selective and sensitive sensing of analytes. However, the time-consuming interaction between recognition moieties and analytes is the main hindrance to the application of nanofluidic channel-based sensors in rapid detection. Here, we show the integration of ordered two-dimensional covalent organic frameworks (2D COFs) to solid-state nanofluidic channels to achieve rapid, selective, and sensitive detection of contaminants. As a proof of concept, a thiourea-linked 2D COF (JNU-3) as the recognition unit is covalently bonded on the stable artificial anodic aluminum oxide nanochannels (AAO) to fabricate a JNU-3@AAO-based nanofluidic sensor. The rapid and selective interaction of Hg(II) with the highly ordered channels of JNU-3 allows the JNU-3@AAO-based nanofluidic sensor to realize ultrafast and precise determination of Hg(II) (90 s) with a low limit of detection (3.28 fg mL^-1), wide linear range (0.01-100 pg mL^-1), and good precision (relative standard deviation of 3.8% for 11 replicate determination of 10 pg mL^-1). The developed method was successfully applied to the determination of mercury in a certified reference material A072301c (rice powder), real water, and rice samples with recoveries of 90.4-99.8%. This work reveals the great potential of 2D COFs-modified solid-state nanofluidic channels as a sensor for the rapid and precise detection of contaminants in complicated samples.

Bioinspired Hydrogen Peroxide-Activated Nanochannels and Their Applications in Cancer Cell Analysis

Bioinspired nanochannels that manipulate ion transport have shown great potential for understanding complex physiological processes. Herein, inspired by the gating function of the biological ion channels, we designed and constructed artificial hydrogen peroxide (H₂O₂)-activated nanochannels by decorating the inner pore surface with 4-(phenoxymethyl) benzeneboronic acid pinacol ester (PBAE). Benefiting from the specific hydrolysis reaction between H₂O₂ and PBAE in the confined nanochannels, the functionalized artificial nanochannels exhibited a highly selective and sensitive response toward H₂O₂. The system could switch between open/closed states in the presence/absence of H₂O₂ by the ionic current test. Meanwhile, comsol simulations were carried out to evidence the mechanism of hydrogen peroxide triggered regulation of ion transport by the nanochannels. It was found that the surface charge density of the nanochannels changed along with the addition of H₂O₂. Furthermore, based on the sensing strategy, the PBAE-functionalized nanochannel membrane was applied in the detection of H₂O₂ in the tumor microenvironment, which achieved highly selective distinguishing of cancerous cells from normal cells. This work provides a versatile method to construct bioinspired nanochannel-based platforms for detecting small reactive molecules and offers prospects for the application of disease diagnosis and prognosis.

Interfacial Superassembly of Mesoporous Titania Nanopillar-Arrays/Alumina Oxide Heterochannels for Light- and pH-Responsive Smart Ion Transport

Stimuli-responsive nanochannels have attracted extensive attention in various fields owing to their precise regulation ability of ionic transportation. However, the poor controllability and functionality as well as responding to only one type of external stimulus still impede the development of the smart nanochannels. Here, we demonstrate a novel heterogeneous membrane composed of ordered mesoporous titania nanopillar-arrays/anodic aluminum oxide (MTI/AAO) using an interfacial superassembly strategy, which can achieve intelligent light and pH multimodulation ion transport. The MTI/AAO membranes are generated through the self-assembly of templates, followed by interfacial superassembly of micelles on AAO, and then the nanostructure and phase transformation of titania. The presence of the MTI layer with anatase crystal endows the heterogeneous membrane with an excellent light-responsive current density of 219.2 μA·cm^-2, which is much higher than that of a reported traditional light-responsive nanofluidic device. Furthermore, the MTI/AAO heterogeneous membranes with an asymmetric structure exhibit excellent rectification performance. Moreover, pH-regulated surface charge polarity leads to a reversal of current rectification polarity. This light and pH multiresponsive membrane realizes efficient, sensitive, and stable ion regulation, extending the traditional nanochannel from single modulation to smart multimodulation.

Super-assembly of freestanding graphene oxide-aramid fiber membrane with T-mode subnanochannels for sensitive ion transport

Biomimetic nacre-like membranes composed of two-dimensional lamellar sheets and one-dimensional nanofibers exhibit high mechanical strength and excellent stability. Thus, they show substantial application in the field of membrane science and water purification. However, the limited techniques for the assembly of two-dimensional lamellar membranes and one-dimensional nanofibers hamper their development and application. Herein, we developed a nacre-like and freestanding graphene oxide/aramid fiber membrane with abundant T-mode subnanochannels by introducing aramid fibers into graphene oxide interlamination via the super-assembly interaction between graphene oxide and aramid fibers. Benefiting from the presence of stable and adjustable sub-nanometer-size ion transport channels, the graphene oxide/aramid fiber composite membrane exhibited excellent mono/divalent ion selectivity of 3.51 (K⁺/Mg²⁺), which is superior to that of the pure graphene oxide membrane. The experimental results suggest that the mono/divalent ion selectivity is ascribed to the subnanochannels in the graphene oxide/aramid fiber composite membrane, electrostatic repulsion interaction and strong interaction between the divalent metal ion and carboxyl groups. Moreover, the composite membrane exhibited remarkable charge selectivity with a K⁺/Cl^- ratio of up to ∼158, indicating that this graphene oxide/aramid fiber composite membrane has great potential for application in energy conversion. This study provides an avenue to prepare freestanding and nacre-like composite membranes with abundant T-mode ion transport channels for ion recognition and energy conversion, which also shows great application prospects in the field of membrane science and water purification.

Interfacially Super-Assembled Tyramine-Modified Mesoporous Silica-Alumina Oxide Heterochannels for Label-Free Tyrosinase Detection

Tyrosinase (TYR) is a multifunctional copper-containing enzyme that plays a critical role in the biosynthetic pathway of melanin. Thus, the detection of TYR activity possesses vast importance from clinical diagnosis to the food industry. However, most TYR detection methods are expensive, complicated, and time-consuming. Herein, a functional nanofluidic heterochannel composed of an ultrathin tyramine-modified mesoporous silica layer (Tyr-MS) and alumina oxide (AAO) arrays is constructed by an interfacial super-assembly method. The heterochannel with plenty of enzyme catalytic sites for TYR provides the response of the ion current signal against TYR concentrations. Introducing enzymatic reaction paves the way for the heterochannel to achieve label-free, selective, specific detection of TYR. Notably, a highly sensitive detection of TYR with a limit of 2 U mL^-1 was obtained by optimizing the modified conditions. Detailed investigations and theoretical calculations further reveal the mechanism for the detection performance. This work provides a simple, low-cost, quick response, and label-free platform based on functional nanofluidic devices for enzyme-sensing technologies.