Advances of Electrochemical and Electrochemiluminescent Sensors Based on Covalent Organic Frameworks

Covalent organic frameworks(COFs),a rapidly developing category of crystalline conjugated organic polymers,possess highly ordered structures,large specific surface areas,stable chemical properties,and tunable pore microenvironments.Since the first report of boroxine/boronate ester-linked COFs in 2005,COFs have rapidly gained popularity,showing important application prospects in various fields,such as sensing,catalysis,separation,and energy storage.Among them,COFs-based electrochemical(EC)sensors with upgraded analytical performance are arousing extensive interest.In this review,therefore,we summarize the basic properties and the general synthesis methods of COFs used in the field of electroanalytical chemistry,with special emphasis on their usages in the fabrication of chemical sensors,ions sensors,immunosensors,and aptasensors.Notably,the emerged COFs in the electrochemiluminescence(ECL)realm are thoroughly covered along with their preliminary applications.Additionally,final conclusions on state-of-the-art COFs are provided in terms of EC and ECL sensors,as well as challenges and prospects for extending and improving the research and applications of COFs in electroanalytical chemistry.

Individual dynamics and local heterogeneity provide a microscopic view of the epidemic spreading

The COVID-19 pandemic has caused severe global disasters,highlighting the importance of understanding the details and trends of epidemic transmission in order to introduce efficient intervention measures.While the widely used deterministic compartmental models have qualitatively presented continuous “analytical” insight and captured some transmission features,their treatment usually lacks spatiotemporal variation.Here,we propose a stochastic individual dynamical(SID)model to mimic the random and heterogeneous nature of epidemic propagation.The SID model provides a unifying framework for representing the spatiotemporal variations of epidemic development by tracking the movements of each individual.Using this model,we reproduce the infection curves for COVID-19 cases in different areas globally and find the local dynamics and heterogeneity at the individual level that affect the disease outbreak.The macroscopic trend of virus spreading is clearly illustrated from the microscopic perspective,enabling a quantitative assessment of different interventions.Seemingly,this model is also applicable to studying stochastic processes at the “meter scale”,e.g.,human society’s collective dynamics.

Cigarette smoke promotes oral leukoplakia via regulating glutamine metabolism and M2 polarization of macrophage

Oral immunosuppression caused by smoking creates a microenvironment to promote the occurrence and development of oral mucosa precancerous lesions.This study aimed to investigate the role of metabolism and macrophage polarization in cigarette-promoting oral leukoplakia.The effects of cigarette smoke extract(CSE)on macrophage polarization and metabolism were studied in vivo and in vitro.The polarity of macrophages was detected by flow cytometric analysis and q PCR.Liquid chromatography-mass spectrometry(LC-MS)was used to perform a metabolomic analysis of Raw cells stimulated with CSE.Immunofluorescence and flow cytometry were used to detect the polarity of macrophages in the condition of glutamine abundance and deficiency.Cell Counting Kit-8(CCK-8),wound-healing assay,and Annexin V-FITC(fluorescein isothiocyanate)/PI(propidium iodide)double-staining flow cytometry were applied to detect the growth and transferability and apoptosis of Leuk-1 cells in the supernatant of Raw cells which were stimulated with CSE,glutamine abundance and deficiency.Hyperkeratosis and dysplasia of the epithelium were evident in smoking mice.M2 macrophages increased under CSE stimulation in vivo and in vitro.In total,162 types of metabolites were detected in the CSE group.The metabolites of nicotine,glutamate,arachidic acid,and arginine changed significantly.The significant enrichment pathways were also selected,including nicotine addiction,glutamine and glutamate metabolism,and arginine biosynthesis.The results also showed that the supernatant of Raw cells stimulated by CSE could induce excessive proliferation of Leuk-1 and inhibit apoptosis.Glutamine abundance can facilitate this process.Cigarette smoke promotes oral leukoplakia via regulating glutamine metabolism and macrophage M2 polarization.

Electrocatalytic Oxidation of NADH Based on Self-assembled Colloidal Gold and Nafion Matrixes and Co Complex Mediator

A novel approach based on self-assembled colloidal gold and Nation matrixes and Co complex mediator to construct Co（bpy）3^3＋/nano-Au/Co（bpy）3^3＋/nafion/GC electrode, on which formed stable redox-active films. This electrode can decrease the overpotential about 330 mV for the oxidation of NADH with high stability, wide linear range and low detection limit.

Quantitative‑Profling Method of Serum Steroid Hormones by Hydroxylamine‑Derivatization HPLC-MS

A sensitive and rapid high performance liquid chromatography-mass spectrometry(HPLC-MS)method was developed and validated for simultaneous quantifcation of ten steroid hormones,including estrogens,androgens,progesterones,and corticosteroids four classes of steroids.The following ten steroid hormones were analyzed:progesterone,21-deoxycortisol,estrone,4-androstenedione,testosterone,dihydro-testosterone,androstenone,dehydroepiandrosterone,corticosterone and cortisone.Stable deuterated isotopes were used as internal standards for quantifcation.Sample preparation with and without derivatization were performed after liquid-liquid extraction,and the corresponding results were compared according to sensitivity and selectivity.Hydroxylamine derivatization was found to improve the ionization efciency of the analytes for electrospray ionization MS analysis.The gradient of mobile phase and experimental parameters for HPLC separation were optimized.The lower limits of quantifcation were in the range of 0.05-5 ng mL^(−1) with wide linear range for the ten steroid hormones.The intra-day precision<11.1%and recovery of 84.5-120% with negligible matrix efect were achieved,where within the acceptance limits of the FDA guideline.Total HPLC-MS analysis time was 6 min.This method enables simultaneous quantifcation of steroids in human serum.It will be helpful for the serum steroid profling in order to understand various endocrinology diseases.

Induced growth of Fe-N_x active sites using carbon templates

Highly active Fe-N_x sites that effectively improve the performance of non-precious metal electrocatalysts for oxygen reduction reactions（ORRs） are desirable. Herein, we propose a strategy for introducing a carbon template into a melamine/Fe-salt mixture to inductively generate highly active Fe-N_x sites for ORR. Using 57 Fe M？sbauer spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, we studied the structural composition of the Fe and N co-doped carbon catalysts.Interestingly, the results showed that this system not only converted inactive Fe and Fe-carbides into active Fe-N_4 and other Fe-nitrides, but also improved their intrinsic activities.

Role of the caudate-putamen nucleus in sensory gating in induced tinnitus in rats

Tinnitus can be described as the conscious perception of sound without external stimulation,and it is often accompanied by anxiety,depression,and insomnia.Current clinical treatments for tinnitus are ineffective.Although recent studies have indicated that the caudateputamen nucleus may be a sensory gating area involved in noise elimination in tinnitus,the underlying mechanisms of this disorder are yet to be determined.To investigate the potential role of the caudate-putamen nucleus in experimentally induced tinnitus,we created a rat model of tinnitus induced by intraperitoneal administration of 350 mg/kg sodium salicylate.Our results revealed that the mean spontaneous firing rate of the caudate-putamen nucleus was increased by sodium salicylate treatment,while dopamine levels were decreased.In addition,electrical stimulation of the caudate-putamen nucleus markedly reduced the spontaneous firing rate of neurons in the primary auditory cortex.These findings suggest that the caudate-putamen nucleus plays a sensory gating role in sodium salicylate-induced tinnitus.This study was approved by the Institutional Animal Care and Use Committee of Peking University Health Science Center(approval No.A2010031)on December 6,2017.

Coprecipitation Synthesis of Fluorides Nanoparticles with Multiform Structures and Mechanisms Research

Fluoride nanoparticles with multiform crystal structures and morphologies were successfully synthesized by a facile, effective, and environmentally friendly coprecipitation method. Transmission electron microscopy (TEM) was used to characterize the nanoparticles. The nanoparticles were modified by PEI, CTAB, PAA and Ci, respectively. It was feasible for function by -COOH and -NH2 groups, due to the surface modification. Moreover, different surface modifications of the nanoparticles were examined. The possible formation mechanisms for fluoride nanoparticles with surface modification were presented in detail. More importantly, it is expected to be widely applied to biomedicine.

Visualization analysis of lecithin in drugs based on electrochemiluminescent single gold microbeads

Fast and high-throughput determination of drugs is a key trend in clinical medicine.Single particles have increasingly been adopted in a variety of photoanalytical and electroanalytical applications,and microscopic analysis has been a hot topic in recent years,especially for electrochemiluminescence(ECL).This paper describes a simple ECL method based on single gold microbeads to image lecithin.Lecithin reacts to produce hydrogen peroxide under the successive enzymatic reaction of phospholipase D and choline oxidase.ECL was generated by the electrochemical reaction between a luminol analog and hydrogen peroxide,and ECL signals were imaged by a camera.Despite the heterogeneity of single gold microbeads,their luminescence obeyed statistical regularity.The average luminescence of 30 gold microbeads is correlated with the lecithin concentration,and thus,a visualization method for analyzing lecithin was established.Calibration curves were constructed for ECL intensity and lecithin concentration,achieving detection limits of 0.05 m M lecithin.This ECL imaging platform based on single gold microbeads exhibits outstanding advantages,such as high throughput,versatility and low cost,and holds great potential in disease diagnostics,environmental monitoring and food safety.

Study on the Structural Effect of Maltoligosaccharides on Cytochrome c Complexes Stabilities by Native Mass Spectrometry

Noncovalent interactions between ligands and targeting proteins are essential for understanding molecular mechanisms of proteins.In this work,we investigated the interaction of Cytochrome c(Cyt c)with maltoligosaccharides,namely maltose(Mal Ⅱ),maltotriose(Mal Ⅲ),maltotetraose(Mal Ⅳ),maltopentaose(Mal Ⅴ),maltohexaose(Mal Ⅵ)and maltoheptaose(Mal Ⅶ).Using electrospray ionization mass spetrometry(ESI-MS)assay,the 1:1 and 1:2 complexes formed by Cyt c with maltoligosaccharide ligand were observed.The corresponding association constants were calculated according to the deconvoluted spectra.The order of the relative binding affinities of the selected oligosaccharides with Cyt c were as MalⅢ>MalⅣ>MalⅡ>MalⅤ>MalⅥ>MalⅦ.The results indicated that the stability of noncovalent protein complexes was intimately correlated to the molecular structure of bound ligand.The relevant functional groups that could form H-bonds,electrostatic or hydrophobic forces with protein’s amino residues played an important role for the stability of protein complexes.In addition,the steric structure of ligand was also critical for an appropriate interaction with the binding pocket of proteins.

Mutants only Partially Represent Characteristics of Calcium-ReleaseActivated Calcium Channel Gating

Calcium-release-activated calcium(CARC)channels are one of the major pathways of calcium entry in non-excitable cells.Despite a decade or two of research,its regulatory mechanism is not yet thoroughly understood.The slow progress is due to the complexity of its pores(i.e.,Orai)on one hand and the difficulty in capturing its regulatory complex on the other hand.As a result,possible gating mechanisms have often been speculated by exploring the structure and properties of constitutive open mutants.However,there is much debate about how they can truly reflect the gating of CRAC channels under physiological conditions.In the present study,we combined molecular dynamics simulations with free energy calculations to study three dOrai mutants(G170P,H206A,and P288A),and further calculated their current-voltage curves.Results show that these constructs adopt different approaches to maintain their conductive state.Meanwhile they have unique pore structures and distinctive rectification properties and ion selectivity for cations compared to wild-type pores.We conclude that although the mutants may partially capture the gating motion characteristics of wild-type pores,the information obtained from these mutants is likely not a true reflection of CRAC channel gating under physiological conditions.

Luminescence and ESR Studies of CaS：Dy Phosphor

CaS phosphor activated with Dy ions is prepared by the solid-state diffusion method. The phosphor is characterized by x-ray powder diffraction, thermogravimetric analysis and photoiuminescence. Defect centres formed in CaS：Dy are studied using the technique of electron spin resonance. The thermoluminescence glow curve shows peaks at around 117℃ and 345℃. Irradiated CaS：Dy exhibits ESR lines due to defect centres. The thermal annealing behaviour of one of the defect centres appears to correlate with the TL peaks at 117℃ and 345℃. This centre is characterized by an isotropic g-value of 2.0035 and is assigned to an F^＋ centre.

New Researches of State Key Laboratories in Analytical Chemistry

In the past two decades,as the eyes of fundamental scientific research and social activities relative to human security and health,analytical chemistry has made great progress in both analytical methodologies and detection instruments by integrating multidisciplinary research achievements.Four State Key Laboratories were successively established in this rapidly developing discipline.In order to publish some of the excellent results together,we have organized this special topic with 10 Articles and Reviews from these State Key Laboratories.

Microwave-assisted sol-gel synthesis of hydroxyapatite nanoparticles

A rapid sol-gel method for preparing hydroxyapatite nanoparticles(nHAP) has been developed. Three different sets of experimental conditions, in terms of solvents(water and ethanol), synthesis temperatures(25, 40 and 60℃), and microwave irradiation(on and off) were explored. Crystal phase composition, functional groups and morphology of the products were characterized by thermogravimetric analysis(TGA), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The solvent and temperature were optimized based on product properties. Most importantly, the microwave-assisted method(with little to no ageing necessary) was much faster than the conventional methods(with slow ageing processes needing from hours to days), while affording pure nHAP with virtually identical morphological and structural properties. This study represents a practical application of the powerful microwave technique in synthesis of nHAP, offering guidance on the selection of optimum experiment conditions.

The catalytic properties of DNA G‐quadruplexes rely on their structural integrity

The influence of the G‐quartet structural integrity on the catalytic activity of the G‐quadruplex(G4)was investigated by comparing the G4‐DNAzyme performances of a series of G4s with a G‐vacancy site and a G‐triplex(G‐tri).The results presented herein not only confirm that the structural integrity of the 3'‐end G‐quartet is necessary for G4s to be catalytically competent but also show how to remediate G‐vacancy‐mediated catalytic activity losses via the addition of guanine surrogates in an approach referred to as G‐vacancy complementation strategy that is applicable to parallel G4s only.Furthermore,this study demonstrates that the terminal G‐quartet could act as a proximal coordinating group and cooperate with the flanking nucleotide to activate the hemin cofactor.

A Novel Tetraiodocadmate（Ⅱ） - PVC Membrane Electrode for the Potentiometric Determination of Cadmium（Ⅱ）

A novel tetraiodocadmate（Ⅱ）-selective membrane electrode consisting of tetraiodo-cadmate（Ⅱ）-rhodamin B ion pair （TICRhB） dispersed in a PVC matrix plasticized with 2-nitrophenyl octyl ether （o-NPOE） was prepared. The sensor demonstrated a near-Nernstian response for 1×10^-2 to 2×10^-6 mol/L cadmium （Ⅱ） at 25℃ with an anionic slope of 29.0. It revealed very good selectivity for Cd^2＋ with negligible interference from many cations and anions, and could be used in a pH range of 3 to 6.

The effective transfection of a low dose of negatively charged drug-loaded DNA-nanocarriers into cancer cells via scavenger receptors

DNA-nanotechnology-based nano-architecture scaffolds based on circular strands were designed in the form of DNA-nanowires(DNA-NWs) as a polymer of DNA-triangles. Circularizing a scaffold strand(84-NT) was the critical step followed by annealing with various staple strands to make stiff DNAtriangles. Atomic force microcopy(AFM), native polyacrylamide gel electrophoresis(PAGE), UVanalysis, MTT-assay, flow cytometry, and confocal imaging were performed to assess the formulated DNA-NWs and cisplatin(CPT) loading. The AFM and confocal microscopy images revealed a uniform shape and size distribution of the DNA-NWs, with lengths ranging from 2 to 4 mm and diameters ranging from 150 to 300 nm. One sharp band at the top of the lane(500 bp level) with the loss of electrophoretic mobility during the PAGE(native) gel analysis revealed the successful fabrication of DNA-NWs. The loading efficiency of CPT ranged from 66.85% to 97.35%. MTT and flow cytometry results showed biocompatibility of the blank DNA-NWs even at 95% concentration compared with the CPT-loaded DNANWs. The CPT-loaded DNA-NWs exhibited enhanced apoptosis(22%) compared to the apoptosis(7%)induced by the blank DNA-NWs. The release of CPT from the DNA-NWs was sustained at < 75% for 6 h in the presence of serum, demonstrating suitability for systemic applications. The IC_(50) of CPT@DNA-NWs was reduced to 12.8 nM CPT, as compared with the free CPT solution exhibiting an IC_(50) of 51.2 n M.Confocal imaging revealed the targetability, surface binding, and slow internalization of the DNA-NWs in the scavenger-receptor-rich cancer cell line(HepG2) compared with the control cell line.

Seminal Plasma Biochemical Components Mediate the Inverse Association of Microcystin Exposure with Sperm Motility:A Mediation Analysis in Chinese Men

Epidemiological studies suggest a global decline in male fertility, which accounts for approximately50% of infertility cases in couples. Male infertility is a multifactorial and complex issue that may arise due to congenital, acquired, idiopathic, or other unknown factors[1].

Corrigendum to“The effective transfection of a low dose of negatively charged drug-loaded DNA-nanocarriers into cancer cells via scavenger receptors”[Journal of Pharmaceutical Analysis volume 11(2021)174e182]

The authors regret to inform that Figs.4,6,and 7 in the original article were wrongly selected.The corrected figures appear below:The authors would like to apologize for any inconvenience caused.

Adsorption of cytochrome c by succinic anhydride-modified peanut shells

A novel adsorbent based on peanut shells modified with glutaraldehyde and succinic anhydride was prepared. Factors affecting the adsorption capacity, such as the pH, temperature, adsorption time, initial cytochrome c (cyt c) concentration and NaCl ionic strength, were extensively investigated. The results showed that the maximum adsorption capacity of the modified peanut shells (MPSs) was 432.6 mg/g when 10 mL of cyt c solution was adsorbed by 20 mg of MPSs at pH 5.0 for 3 h. In contrast, the adsorption capacities of the unmodified peanut shells (PSs), alkaline peanut shells (APSs) and crosslinked peanut shells (CPSs) were only 100.6, 180.3, and 173.0 mg/g, respectively, 4.3-, 2.4-, and 2.5-fold lower, respectively, than that of the modified shells. The desorption rate reached 89.9% with 1.5 mol/L NaCNS as an eluent, because the electrostatic attraction between the positive charges of the protein and the negative charges of the MPSs was reduced when the ionic strength was increasing. The MPSs were used to separate and purify cytochrome c from pig myocardium. A purification of 13.5-fold in a single step with a total enzyme activity recovery of 74.0% was achieved.