Electrochemical Biosensor for Detection of the CYP2C19*2 Allele Based on Exonuclease Ⅲ

Currently, the therapeutic effect of clopidogrel differs considerably among individuals and is thought to be closely related to the genetic polymorphism of CYP2C19. The CYP2C19*2 gene can reduce the antiplatelet aggregation effect of clopidogrel, which increases the risk of major cardiovascular adverse events in patients. In this research, we report a new type of biosensor for the highly sensitive detection of the CYP2C19*2 gene based on exonuclease III assisted electric signal amplification and the use of calixarene to enrich electrical signal substances. Specifically, under the best conditions, the logarithmic concentrations of the analytes have a good linear relationship with the peak current in the range of 0.01 fM to 100 pM and the detection limit is 13.49 aM. The results have also shown that this method has good selectivity, high sensitivity, and stability, etc., and will provide a very promising application for the detection of the CYP2C19*2 gene and other biological molecules by replacing corresponding nucleic acid sequences.

MXenes Functionalized with Macrocyclic Hosts: From Molecular Design to Applications

Two-dimensional (2D) MXene has aroused wide attention for its excellent physical and chemical properties. The interlayer engineering formed by layer-by-layer stacking of MXene nanosheets can be employed for molecular sieving and water purification by incorporating specific groups onto the exterior surface of MXene. Macrocyclic hosts exhibiting unique structural features and recognition ability can construct smart devices for external stimuli with reversible features between macrocycles and guests. On that basis, macrocyclic hosts can be anchored to MXene to provide numerous insights into their compositions and intercalation states. In this review, the MXene prepared based on macrocyclic hosts from molecular design to applications is highlighted. Various MXenes functionalized with macrocyclic hosts are empowered in functional membrane (including water purification, organic solvent nanofiltration, and electromagnetic shielding), photocatalysis, sensing, and adsorption (interactions with specific guest). Hopefully, this review can bring new inspiration to the design of multifunctional MXene-based materials and improving its practical applications.

Integrated biosensor platform based on graphene transistor arrays for real-time high-accuracy ion sensing

Two-dimensional materials such as graphene have shown great promise as biosensors, but suffer from large device-to-device variation due to non-uniform material synthesis and device fabrication technologies. Here, we develop a robust bioelectronic sensing platform  composed of  more than 200 integrated sensing units, custom-built high-speed readout electronics, and machine learning inference that overcomes these challenges to achieve rapid, portable, and reliable measurements. The platform demonstrates reconfigurable multi-ion electrolyte sensing capability and provides highly sensitive, reversible, and real-time response for potassium, sodium, and calcium ions in complex solutions despite variations in device performance. A calibration method leveraging the sensor redundancy and device-to-device variation is also proposed, while a machine learning model trained with multi-dimensional information collected through the multiplexed sensor array is used to enhance the sensing system’s functionality and accuracy in ion classification.

The potential of 2D materials for biosensing applications is often limited by large device-to-device variation. Here, the authors report a calibration method and a machine learning approach leveraging the redundancy of a sensing platform based on 256 integrated graphene transistors to enhance the system accuracy in real-time ion classification.

Calix[n]arene/Pillar[n]arene-Functionalized Graphene Nanocomposites and Their Applications

Calix[n]arenes and pillar[n]arenes, which contain repeating units of phenol and methane, are class of synthetic cyclic supramolecules. Their rigid structure, tunable cavity size, flexible functionalization, and rich host-guest properties make them ideal surface modifiers to construct functional hybrid materials. Introduction of the calix[n]arene/pillar[n]arene species to the graphene may bring new interesting or enhanced physicochemical/biological properties by combining their individual characteristics. Reported methods for the surface modification of graphene with calix[n]arene/pillar[n]arene utilize either covalent or non-covalent approaches. This mini-review presents the recent advancements in the functionalization of graphene nanomaterials with calix[n]arene/pillar[n]arene and their applications. At the end, the future outlook and challenges for the continued research of calix[n]arene/pillar[n]arene-functionalized graphene nanohybrids in the development of applied nanoscience are thoroughly discussed.

Selective Detection of Cu2+ Ions by Immobilizing Thiacalix[4]arene on Graphene Field-Effect Transistors

Highly accurate quantitative detection of heavy metals is essential for environmental pollution monitoring and health safety. Here, for selective detection of Cu2+ ions with high sensitivity, thiacalix[4]arene (TCA) immobilized on graphene field-effect transistors (G-FETs) are developed. Our proposed TCA-immobilized G-FETs are successfully used to detect Cu2+ ions at concentrations ranging from 1 μM to 1 mM via changes in their transfer characteristics. Moreover, the measured transfer characteristics clearly shift only when Cu2+ ions are introduced in the buffer solution despite it containing other metal ions, including those of Na+, Mg2+, Ni2+, and Cd2+; this selective detection of Cu2+ ions is attributed to the planar arrangement of TCA on graphene. Therefore, TCA-immobilized G-FETs selectively detect Cu2+ with high sensitivity.

p-Phosphonic acid calix[8]arene mediated synthesis of ultra-large, ultra-thin, single-crystal gold nanoplatelets

Large, ultrathin, single-crystal gold platelets are produced in the presence of p-phosphonic acid calix[8]arene as both a catalyst and stabiliser.

Scalable exfoliation and dispersion of two-dimensional materials - an update

The preparation of dispersions of single- and few-sheet 2D materials in various solvents, as well as the characterization methods applied to such dispersions, is critically reviewed. Motivating factors for producing single- and few-sheet dispersions of 2D materials in liquids are briefly discussed. Many practical applications are expected for such materials that do not require high purity formulations and tight control of donor and acceptor concentrations, as required in conventional Fab processing of semiconductor chips. Approaches and challenges encountered in exfoliating 2D materials in liquids are reviewed. Ultrasonication, mechanical shearing, and electrochemical processing approaches are discussed, and their respective limitations and promising features are critiqued. Supercritical and more conventional liquid and solvent processing are then discussed in detail. The effects of various types of stabilizers, including surfactants and other amphiphiles, as well as polymers, including homopolymeric electrolytes, nonionic polymers, and nanolatexes, are discussed. Consideration of apparent successes of stabilizer-free dispersions indicates that extensive exfoliation in the absence of dispersing aids results from processing-induced surface modifications that promote stabilization of 2D material/solvent interactions. Also apparent paradoxes in "pristineness" and optical extinctions in dispersions suggest that there is much we do not yet quantitatively understand about the surface chemistry of these materials. Another paradox, emanating from modeling dilute solvent-only exfoliation by sonication using polar components of solubility parameters and surface tension for pristine graphene with no polar structural component, is addressed. This apparent paradox appears to be resolved by realizing that the reactivity of graphene to addition reactions of solvent radicals produced by sonolysis is accompanied by unintended polar surface modifications that promote attractive interactions with solvent. This hypothesis serves to define important theoretical and experimental studies that are needed. We conclude that the greatest promise for high volume and high concentration processing lies in applying methods that have not yet been extensively reported, particularly wet comminution processing using small grinding media of various types.

Enhanced removal of phosphate and nitrate ions from aqueous media using nanosized lanthanum hydrous doped on magnetic graphene nanocomposite

A novel nanocomposite adsorbent based on nanosized lanthanum hydroxide doped onto magnetic reduced graphene oxide (MG@La) was synthesized and used for removal of phosphate and nitrate ions from river and sewage media. The composition, surface properties and morphology of the as prepared adsorbent were studied using Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The influence of main parameters on the efficiency of removal process including adsorbent dosage, salt addition, solution pH, contact time, and concentration of the analytes were thoroughly investigated. The validity of the experimental process was checked by the adsorption isotherm and adsorption kinetics models. The obtained data were well fitted to Langmuir isotherm and pseudo-second-order kinetic models. The developed adsorbent showed high adsorption capacities of 116.28 mg g^-1 and 138.88 mg g^-1 for phosphate and nitrate ions, respectively. Additionally, Langmuir isotherm and free energy were suggested monolayer pattern and physisorption mechanism for adsorption process, respectively. Finally, the field application of newly synthesized MG@La provided high removal efficiencies (74%-90%) for phosphate and nitrate ions in real river and sewage water samples.

p-Phosphonated Calix[n]arene Stabilizes Superparamagnetic Nanoparticles for Nitrate and Phosphate Uptake

Highly faceted superparamagnetic magnetite nanoparticles roughly 11 nm in diameter are readily accessible in the presence of p-phosphonated calix[n]arenes of different ring sizes (n=4, 5 and 6), through the use of a simple co-precipitation technique. In contrast, the larger calix[8]arene affords spherical particles of comparable size. The maximum magnetization is 70-60 emu g^-1 , which decreases with increasing size of the calixarene macrocycle, and the evidence indicates that the calixarenes bind to the surface of the nanoparticles via the phosphonate head groups rather than the phenolic oxygen centers. The stabilized nanoparticles show dual functionality: they remove up to 62 % of nitrate nitrogen and 48 % of phosphate from an aqueous effluent after 24 hours at concentrations of only 1 g L^-1 of calixarene-coated nanoparticles.

p-sulfonated calix[8]arene functionalized graphene as a "turn on" fluorescent sensing platform for aconitine determination

This work reports a novel method for the determination of aconitine through the competitive host-guest interaction between p-sulfonated calix[8]arene (SCX8) and signal probe/target molecules by using SCX8 functionalized reduced graphene oxide (SCX8-RGO) as a receptor. Three dyes (ST, RhB, BRB) and aconitine were selected as the probe and target molecules, respectively. The formation of SCX8-RGO·ST, SCX8-RGO·RhB, and SCX8-RGO·BRB complexes greatly decreases the fluorescence emission of ST, RhB, and BRB. The aconitine/SCX8 complex possesses a higher binding constant than ST/SCX8, RhB/SCX8, and BRB/SCX8 complexes, thus the dye in the SCX8 cavity can be replaced by aconitine to revert the fluorescence emission of SCX8-RGO·dye, leading to a "switch-on" fluorescence response. The fluorescence intensity of SCX8-RGO·ST, SCX8-RGO·RhB, and SCX8-RGO·BRB complexes increased linearly with increasing concentration of aconitine ranging from 1.0 to 14.0μM, 2.0-16.0μM, and 1.0-16.0μM, respectively. Based on the competitive host-guest interaction, the proposed detection method for aconitine showed detection limits of 0.28μM, 0.60μM, and 0.37μM, respectively, and was successfully applied for the determination of aconitine in human serum samples with good recoveries from 95.1% to 104.8%. The proposed method showed high selectivity for aconitine beyond competitive binding analytes. In addition, the inclusion complex of the SCX8/aconitine was studied by the molecular docking and molecular dynamics simulation, which indicated that the phenyl ester group of the aconitine molecule was included into the SCX8 cavity.

Indicator displacement assay for cholesterol electrochemical sensing using a calix[6]arene functionalized graphene-modified electrode

Indicator displacement assay for cholesterol (Cho) sensing using CX6–Gra against MB.

Synthesis of a thiacalix[4]arenetetrasulfonate-functionalized reduced graphene oxide adsorbent for the removal of lead(ii) and cadmium(ii) from aqueous solutions

A thiacalix[4]arenetetrasulfonate-functionalized reduced graphene oxide (TCAS–rGO) adsorbent was synthesized and used as an adsorbent for the removal of lead(ii) and cadmium(ii) from aqueous solutions.

Fluorescent Detection of Tadalafil Based on Competitive Host-Guest Interaction Using p-Sulfonated Calix[6]arene Functionalized Graphene

A competitive fluorescence method toward tadalafil detection has been developed based on host-guest recognition by selecting rhodamine B (RhB) and p-sulfonated calix[6]arene functionalized graphene (CX6-Gra) as the "reporter pair". Upon the presence of tadalafil to the performed CX6-Gra-RhB complex, the RhB molecules are displaced by tadalafil, leading to a "switch-on" fluorescence signal. The observed fluorescence signal can be used for quantitative detection of tadalafil ranging from 1.00 to 50.00 μM with a detection limit of 0.32 μM (S/N = 3). The inclusion complex of tadalafil and CX6 was studied by molecular docking and the results indicated that a 1:1 host-guest stoichiometry had the lowest ΔG value of -7.18 kcal/mol. The docking studies demonstrated that the main forces including π-π interactions, electrostatic interactions, and hydrophobic interactions should be responsible for the formation of this inclusion compound. The mechanism of the competitive host-guest interaction was clarified. The binding constant (K) of the tadalafil/CX6 complex was more than 5 times greater than that of RhB/CX6.

Lateral assembly of oxidized graphene flakes into large-scale transparent conductive thin films with a three-dimensional surfactant 4-sulfocalix[4]arene

Graphene is a promising candidate material for transparent conductive films because of its excellent conductivity and one-carbon-atom thickness. Graphene oxide flakes prepared by Hummers method are typically several microns in size and must be pieced together in order to create macroscopic films. We report a macro-scale thin film fabrication method which employs a three-dimensional (3-D) surfactant, 4-sulfocalix[4]arene (SCX), as a lateral aggregating agent. After electrochemical exfoliation, the partially oxidized graphene (oGr) flakes are dispersed with SCX. The SCX forms micelles, which adsorb on the oGr flakes to enhance their dispersion, also promote aggregation into large-scale thin films under vacuum filtration. A thin oGr/SCX film can be shaved off from the aggregated oGr/SCX cake by immersing the cake in water. The oGr/SCX thin-film floating on the water can be subsequently lifted from the water surface with a substrate. The reduced oGr (red-oGr) films can be as thin as 10−20 nm with a transparency of >90% and sheet resistance of 890 ± 47 kΩ/sq. This method of electrochemical exfoliation followed by SCX-assisted suspension and hydrazine reduction, avoids using large amounts of strong acid (unlike Hummers method), is relatively simple and can easily form a large scale conductive and transparent film from oGr/SCX suspension.

Hydrogen induced p-phosphonic acid calix[8]arene controlled growth of Ru, Pt and Pd nanoparticles

Monodispersed Ru, Pt and Pd nanoparticles with narrow size distributions (2, 12 and 20 nm respectively) have been synthesised via bubbling hydrogen gas into aqueous solutions of the noble metal ions in the presence of p-phosphonic acid calix[8]arene, at room temperature. Molecular modelling of the Ru nanoparticles provides insight into the role of the calixarene in controlling the size and stabilisation of the metal nanoparticles.

Self-assembled calixarene aligned patterning of noble metal nanoparticles on graphene

Patterns of noble metal nanoparticles (NMNPs) of ruthenium and platinum are formed on p-phosphonic acid calix[8]arene stabilised graphene in water. This involves hydrogen gas induced reduction of metal ions absorbed on the stabilised graphene, with TEM revealing the patterns being comprised of domains of parallel arrays of NMNPs ∼7 nm apart. The domains are orientated in three directions on each graphene sheet at an angle of ∼60° or ∼120° with respect to each other. AFM of self-assembled p-phosphonic acid calix[8]arene on the surface of a highly ordered pyrolytic graphite (HOPG) revealed a similar pattern, implying that the orientation of the assembly of p-phosphonic acid calix[8]arene is governed by the hexagonal motif of graphite/graphene.

Nitrate uptake by p-phosphonic acid or p-(trimethylammonium)methyl calix[8]arene stablized laminar materials

Graphite, BN, MoS₂ and WS₂ are exfoliated and stablized in water with positively or negatively charged non-toxic calix[8]arenes. All 2D materials adsorb nitrate from waste effluent, precipitating once nitrate is bound, and can be regenerated.