General In Situ Engineering of Carbon-Based Materials on Carbon Fiber for In Vivo Neurochemical Sensing.

Developing real-time, dynamic, and in situ analytical methods with high spatial and temporal resolutions is crucial for exploring biochemical processes in the brain. Although in vivo electrochemical methods based on carbon fiber (CF) microelectrodes are effective in monitoring neurochemical dynamics during physiological and pathological processes, complex post modification hinders large-scale productions and widespread neuroscience applications. Herein, we develop a general strategy for the in situ engineering of carbon-based materials to mass-produce functional CFs by introducing polydopamine to anchor zeolitic imidazolate frameworks as precursors, followed by one-step pyrolysis. This strategy demonstrates exceptional universality and design flexibility, overcoming complex post-modification procedures and avoiding the delamination of the modification layer. This simplifies the fabrication and integration of functional CF-based microelectrodes. Moreover, we design highly stable and selective H+, O2, and ascorbate microsensors and monitor the influence of CO2 exposure on the O2 content of the cerebral tissue during physiological and ischemia-reperfusion pathological processes.

Preparation of Super-Flexible Silica Aerogel and Its Application in Oil-Water Separation.

Using silica as the precursor, and methyltrimethoxysilane and dimethyldimethoxysilane as the silicon sources, a super-flexible hydrophobic lipophilic gel solid was prepared via hydrolysis, drying, solvent replacement, and atmospheric-pressure drying. The characterization test showed that the sample had good flexibility, hydrophobicity, an amorphous structure, and a hydrophobic contact angle of 137°. Through the adsorption separation experiment, it was concluded that the adsorption separation rate of aerogel to oil substances is related to the viscosity of the oil substances. The hydrophobic and oleophilic properties of flexible silicon aerogel materials can be applied to many aspects, such as crude oil leakage and kitchen waste oil recovery, with broad future development prospects and great research significance.

Copper-Catalyzed Synthesis of 3-Aryl-9H-imidazo[1,5-a]indol-9-ones Using Oxygen as the Sole Oxidant.

A three-component strategy was developed for 3-phenyl-9H-imidazo[1,5-a]indol-9-one preparation from indole-2-carboxaldehydes, aromatic aldehydes, and ammonium acetate under copper catalysis conditions. In this process, a new five-membered ring was formed and the C3 position in the indole substrate was selectively oxidized into a ketone skeleton using oxygen as the sole oxidant and ammonium acetate as the nitrogen source. Furthermore, same products also could be achieved from indole-2-carboxaldehydes and benzyl amines under similar reaction conditions.

Visible-Light-Induced Stoichiometric Coupling of Alkylarenes and Trifluoromethyl Ketones.

A visible-light induced direct C(sp3)-H functionalization of alkylarenes with trifluoromethyl ketones has been reported to access valuable benzyl-substituted trifluoromethyl alcohols in a stoichiometric manner. Readily available petroleum-derived alkylarenes are employed as latent benzylation reagents. With a bromine radical as the hydrogen atom transfer reagent, primary, secondary, and tertiary benzyl C-H bonds are suitable coupling partners. Additionally, the late-stage modification of bioactive molecules highlights the potential application of this approach.

Synergistic Charge Percolation in Conducting Polymers Enables High-Performance In Vivo Sensing of Neurochemical and Neuroelectrical Signals.

Challenges remain in establishing a universal method to precisely tune electrochemical properties of conducting polymers for multifunctional neurosensing with high selectivity and sensitivity. Here, we demonstrate a facile and general approach to achieving synergistic charge percolation in conducting polymers (i.e., poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS) by incorporating conductive catalysts (i.e., carbon nanotubes, CNTs) and post-processing. The approach shows synergistic effects: (i) CNTs and post-processing together promote PEDOT ordered interconnection for highly efficient charge percolation that accelerates electrochemical kinetics; (ii) CNTs catalyze the electrooxidation of vitamin C for selective electrochemical sensing; (iii) CNTs enhance the charge storage/injection capacity of PEDOT:PSS. The prepared CNT-PEDOT:PSS fiber mechanically matches with neural tissues and is proved to be a biocompatible versatile microsensor capable of high-performance neurosensing in vivo.

Support-Free PEDOT:PSS Fibers as Multifunctional Microelectrodes for In Vivo Neural Recording and Modulation.

In vivo microelectrodes are essential for neuroscience studies. However, development of microelectrodes with both flexibility and multifunctionality for recording chemical and electrical signals in the same extracellular microspace and modulating neural activity remains challenging. Here, we find that pure PEDOT:PSS fibers (i.e., support-free) exhibit high conductivity, fast heterogeneous electron transfer, and suitable charge storage and injection capabilities, and can thus directly act as microelectrodes not only for chemical and electrophysiological recording in the same extracellular microspace, but also for electromodulation of neural microcircuit activity. Moreover, the microelectrodes mechanically match with neural tissues, exhibiting less foreign body responses. Given the multifunctionality, flexibility, and biocompatibility, the support-free PEDOT:PSS-based microelectrodes offer a new avenue to microelectrode technology for neuroscience research, diagnostics and therapeutics.

Vitamin D Inhibits the Early Aggregation of α-Synuclein and Modulates Exocytosis Revealed by Electrochemical Measurements.

Alpha-synuclein (α-Syn) localizes at presynaptic terminal and modulates synaptic functions. Increasing evidence demonstrate that α-Syn oligomers, forming at the early of aggregation, are cytotoxic and is thus related to brain neurodegenerative diseases. Herein, we find that vitamin D (VD) can reduce neurocytotoxicity. The reduced neurocytotoxicity might be attributed to the less amount of large-sized α-Syn oligomers inhibited by VD, measured by electrochemical collision at single particle level, which are not observable with traditionally ensembled method. Single-cell amperometry (SCA) results show that VD can recover the amount of neurotransmitter release during exocytosis induced by α-Syn oligomers, further verifying the neuroprotection of VD. Our study reveals the neuroprotective role of VD through inhibiting α-Syn aggregation, which is envisioned to be of great importance in treatment and prevention of the neurodegenerative diseases.

In Vivo Detection of Redox-Inactive Neurochemicals in the Rat Brain with an Ion Transfer Microsensor.

Electrochemical tracking of redox-inactive neurochemicals remain a challenge due to chemical inertness, almost no Faraday electron transfer for these species, and the complex brain atmosphere. In this work, we demonstrate a low-cost, simple-making liquid/liquid interface microsensor (LLIM) to monitor redox-inactive neurochemicals in the rat brain. Taking choline (Ch) as an example, based on the difference in solvation energies of Ch in cerebrospinal fluid (aqueous phase) and 1,2-dichloroethane (1,2-DCE; organic phase), Ch is recognized in the specific ion-transfer potential and distinctive ion-transfer current signals. The LLIM has an excellent response to Ch with good linearity and selectivity, and the detection limit is 0.37 µM. The LLIM can monitor the dynamics of Ch in the cortex of the rat brain by both local microinfusion and intraperitoneal injection of Ch. This work first demonstrates that the LLIM can be successfully applied in the brain and obtain electrochemical signals in such a sophisticated system, allowing one new perspective of sensing at the liquid/liquid interface for nonelectrically active substances in vivo to understand the physiological function of the brain.

Ag2S/Ag Nanoparticle Microelectrodes for In Vivo Potentiometric Measurement of Hydrogen Sulfide Dynamics in the Rat Brain.

Hydrogen sulfide (H2S) plays a pivotal role in gas signal transduction, neuroprotection, and regulation of physiological and pathological processes. However, in vivo tracking the dynamic of hydrogen sulfide in the complex brain environment still faces huge challenges. This study demonstrates a new potentiometric method to monitor in vivo the dynamics of hydrogen sulfide in the rat brain using silver nanoparticles (AgNPs)-modified carbon fiber microelectrodes (AgNPs/CFE) pretreated with Na2S (i.e., Ag2S/AgNPs/CFE), which acts as a solid-contact and ion-selective microelectrode. The Ag2S/AgNPs/CFE exhibits good potential response toward hydrogen sulfide in the range of 2.5-160 µM, with a detection limit of 0.8 µM. Because of the presence of Ag2S, the Ag2S/AgNPs/CFE shows good selectivity to hydrogen sulfide, avoiding the interference from coexistent electroactive neurochemicals and the analogies, such as ascorbic acid and cysteine in the central nervous system. This good selectivity combined with the reversibility, protein antifouling, and biocompatibility of the microelectrode enables the Ag2S/AgNPs/CFE to detect hydrogen sulfide in the rat brain during local microinfusion of Na2S and the change in pH. Our study provides a reliable method to track hydrogen sulfide selectively in vivo, which will help to explore the function of hydrogen sulfide in neurophysiology and pathology.

Rapid determination of the emerging contaminant oxypurinol in surface water using solid phase extraction followed by ultra high-performance liquid chromatography with fluorescence detection.

A method has been developed for the trace analysis of oxypurinol that is considered as an active pharmaceutical ingredient and an emerging environmental contaminant. The method achieved the identification and quantification of oxypurinol in surface water samples utilizing solid phase extraction and ultra high-performance liquid chromatography with diode array and fluorescence detection for the first time. Four principal parameters of solid phase extraction were optimized to obtain maximum extraction efficiency. Under the isocratic elution of methanol/water (5:95, v/v) and the excitation/emission wavelength of 254/359 nm, a rapid determination was achieved in 2.0 min with good linearity of 1.05-351 µg/L (coefficient of determination above 0.9998). The limit of detection and method detection limit were 0.210 µg/L and 1.34 ng/L, respectively. Precision of the method was evaluated and a relative standard deviation value of 3.3% was obtained for analyses of six replicate spiking blank samples (200 mL, 176 ng/L) according to the overall proposed procedure. The method showed a great anti-interference ability and average spiked recoveries of oxypurinol in five surface water samples were in the range of 94.5-111%. The ability of the method to detect and correctly identify oxypurinol can significantly promote investigation on the occurrence of oxypurinol in water and its potential (eco-)toxicological effects. Graphical abstract Quantification of the emerging contaminant oxypurinol in s urface water using SPE/UHPLC-FLD.

Rapid determination of trace polycyclic aromatic hydrocarbons in particulate matter using accelerated solvent extraction followed by ultra high performance liquid chromatography with fluorescence detection.

A method has been developed for the trace analysis of polycyclic aromatic hydrocarbons, which are known as persistent organic pollutants and ubiquitous constituents of fine particulate matter that causes growing airborne pollution. The method, which was especially for samples of airborne particulate matter less than 2.5 µm in diameter, utilized accelerated solvent extraction and ultra high performance liquid chromatography with fluorescence detector. Four principal parameters of accelerated solvent extraction were optimized to obtain maximum extraction efficiency. Using the established synergetic programs of gradient elution and fluorescence wavelength switching, a rapid separation was achieved in 6.56 min with good linearity for 15 polycyclic aromatic hydrocarbons (coefficient of determination above 0.999). The limits of detection ranged from 0.833 to 10.0 pg/m(3) . The precision of the method expressed as inter-day relative standard deviation ranged from 0.2 to 1%, which was calculated from nine repetitive measurements of 8.00 µg/L analytes. Average spiked recoveries ranged from 71.6 to 97.7%, with the exception of naphthalene. The rapid, sensitive, and accurate method can meet the pressing needs of health risk assessment and increasingly heavy daily tasks of air quality monitoring.

Probing the binding of an endocrine disrupting compound-Bisphenol F to human serum albumin: insights into the interactions of harmful chemicals with functional biomacromolecules.

Bisphenol F (BPF) as an endocrine disrupting compounds (EDCs) pollutant in the environment poses a great threat to human health. To evaluate the toxicity of BPF at the protein level, the effects of BPF on human serum albumin (HSA) were investigated at three temperatures 283, 298, and 308 K by multiple spectroscopic techniques. The experimental results showed that BPF effectively quenched the intrinsic fluorescence of HSA via static quenching. The number of binding sites, the binding constant, the thermodynamic parameters and the binding subdomain were measured, and indicated that BPF could spontaneously bind with HSA on subdomain IIA through H-bond and van der Waals interactions. Furthermore, the conformation of HSA was demonstrably changed in the presence of BPF. The work provides accurate and full basic data for clarifying the binding mechanisms of BPF with HSA in vivo and is helpful for understanding its effect on protein function during its transportation and distribution in blood.

Development of electrochemical method for the determination of olaquindox using multi-walled carbon nanotubes modified glassy carbon electrode.

A simple and highly sensitive method for the electrochemical determination of olaquindox (OLA) was developed, which was carried out on the multi-walled carbon nanotubes (MWCNT) modified glassy carbon electrode (MWCNT/GCE) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed that MWCNT remarkably enhanced the reduction of OLA, which improved the cathodic peak current of OLA significantly. Under the optimum condition, the linear range for the calibration curve was 0.3-18.0 µg mL(-1) with a detection limit of 0.26 µg mL(-1). The MWCNT/GCE showed a well reproducibility and the relative standard deviation (R.S.D.) was 3.5% (n=9). And a great anti-interference ability of the MWCNT/GCE was also observed. Finally, the MWCNT/GCE was satisfactorily employed to analyze some synthetic and real water samples.

Multiple spectroscopic studies on the interaction between olaquindox, a feed additive, and bovine serum albumin.

The interaction between olaquindox (OLA) and bovine serum albumin (BSA) was investigated using fluorescence, UV-vis absorption and circular dichroism (CD) spectroscopy. The results showed that the fluorescence quenching of BSA by OLA was a static quenching process induced by the formation of OLA-BSA complex. The binding constant of OLA-BSA complex was calculated to be 1.299 × 10(4)L mol(-1) (293K). The negative values of ΔH(0) and ΔS(0) indicated that hydrogen bond and van der Waals interactions played major roles in stabilizing the complex. Site probe competition experiments and number of binding sites (n) revealed that OLA could bind to site I in subdomain IIA of BSA, and the binding distance (r) was evaluated to be 3.643 nm according to Förster's non-radiative energy transfer theory. The results of CD and three-dimensional fluorescence spectra suggested some conformational changes of BSA after OLA binding.

Adsorption behavior of multi-walled carbon nanotubes for the removal of olaquindox from aqueous solutions.

Multi-walled carbon nanotubes (MWCNT) were employed for the sorption of olaquindox (OLA) from aqueous solution. A detailed study of the adsorption process was performed by varying pH, ionic strength, sorbent amount, sorption time and temperature. The adsorption mechanism is probably the non-electrostatic π-π dispersion interaction and hydrophobic interaction between OLA and MWCNT. The adsorption efficiency could reach 99.7%, suggesting that MWCNT is excellent adsorbents for effective OLA removal from water. OLA adsorption kinetics were found to be very fast and equilibrium was reached within 2.0 min following the pseudo-second-order model with observed rate constants (k) of 0.169-1.048 g mg(-1)min(-1) (at varied temperatures). The overall rate process appeared to be influenced by both external mass transfer and intraparticle diffusion, but mainly governed by intraparticle diffusion. A rapid initial adsorption behavior occurred within a short period of time in this adsorption system. The sorption data could be well interpreted by the Langmuir model with the maximum adsorption capacity of 133.156 mg g(-1) (293 K) of OLA on MWCNT. The mean energy of adsorption was calculated to be 0.124 kJ mol(-1) (293 K) from the Dubinin-Radushkevich adsorption isotherm. Moreover, the thermodynamic parameters showed the spontaneous, exothermic and physical nature of the adsorption process.

Separation of trace amounts of Ga and Ge in aqueous solution using nano-particles micro-column.

A simple and rapid analytical method for the separation of trace amounts of gallium and germanium from aqueous solution by solid-phase extraction with nano-particles was developed. It was found that only Ga(III) could be quantitatively retained on nano-SiO(2) in the pH range of 3-4 and 8-12 while Ge(IV) was not adsorbed, but both Ga(III) and Ge(IV) ions could be adsorbed quantitatively on nano-TiO(2) within the pH range of 4-11. These two ions adsorbed by nano-particles could be desorbed quantitatively. Effects of acidity, concentration of elution solution and interfering ions on the recovery of the analytes were systematically investigated. The sorption data could be well interpreted by the Langmuir model. Based on the Langmuir model equation, the monolayer adsorption capacity of nano-SiO(2)/nano-TiO(2) was calculated to be 4.26 mg g(-1)/19.68 mg g(-1) for Ga(III)/Ge(IV). Moreover, thermodynamic functions, the change of free energy (ΔG(0)), enthalpy (ΔH(0)) and entropy (ΔS(0)) of the adsorption reaction were estimated for each metal ion. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and the adsorption process for both metal ions followed well pseudo-second-order kinetics. Finally, the proposed method was applied to the determination of trace Ga(III) and Ge(IV) in some water samples using loaded nano-particles columns, and it is found that the recoveries of Ga(III) and Ge(IV) were obtained to be in the range of 96.4-105.0%. And the method was validated with certified reference material (GBW07311, GBW 07406) and the values obtained for Ga(III) and Ge(IV) were in good agreement with the certified values.