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An all-solid-state ion-selective electrode (ASS-ISE) array that is portable and easily miniaturized can meet the needs of home sensing devices for long-term health monitoring. However, their stability and accuracy are affected by the multistep modification required for ASS-ISE manufacturing and the complex background signal of real samples. In this study, a four-channel ISE array with the integration of a calibration channel has been developed based on polystyrene-Au (PS-Au) ion-sensing nanocomposites (PS-Au ISE array) for the home detection of Na+ and K+. The nanocomposites combine target recognition function and ion-electron transduction function and could be modified on the channel surface by direct drop-casting, thus simplifying the preparation process and then improving the stability. Meanwhile, the integrated calibration channel could automatically deduct complex background signals in real sample analysis and thus improve the accuracy. As a result, the proposed self-calibrated PS-Au ISE array showed a near Nernstian behavior for Na+ and K+ in the range of 1 × 10-2 M-1 × 10-4 M, and the detection limits were 6.8 × 10-5 M and 5.5 × 10-5 M in artificial urine. The linear equations can be obtained according to the slopes and intercepts of Na+ and K+, and thus, the concentration of the target ions can be directly read out by combining this PS-Au ISE array with the smart electronic device. Furthermore, the detection results of Na+ and K+ in human urine agreed well with those obtained by ICP-AES, suggesting that this proposed self-calibrated PS-Au ISE array is very suitable for home smart sensing devices, facilitating the health monitoring.

An all-solid-state potentiometric aptasensor based on signal amplification by polycation has been proposed for the detection of streptomycin. The carboxylated multi-walled carbon nanotubes (CMWCNTs), polyethylenimine (PEI), and the aptamers of streptomycin were assembled successively on the screen-printing carbon electrode surface by Layer-by-Layer (LbL) technique. The streptomycin would specifically bind to the aptamers, leading to the release of aptamers from the modified electrode surface. Thus, the charges of electrode were changed, causing the variation of open circuit potential (OCP). The introduction of polycation – PEI makes the electrode exposing a large amount of positive charges, so it can combine more aptamers to realize signal amplification. Consequently, under the optimal conditions, this aptasensor showed high sensitivity with corresponding linear response ranges of $1.00\times 10^{-11}-1.00\times 10^{-9}$ M, and a detection limit of $3.43\times 10^{-12}$ M. Moreover, this aptasensor presented good selectivity, reproducibility and stability. It could be applied to the detection of milk samples, demonstrating the practicability of this aptasensor.

Current strand displacement amplification (SDA)-based nucleic acid sensing methods generally rely on a ssDNA template that involves complementary bases to the endonuclease recognition sequence, which has the limitation of detecting only short nucleic acids. Herein, a new SDA method in which the defective T junction structure is first used to support SDA (dT-SDA) was proposed and applied in longer DNA detection. In dT-SDA, an auxiliary probe and a primer were designed to specifically identify the target gene, following the formation of a stable defective T junction structure through proximity hybridization, and the formation of defective T junctions could further trigger cascade SDA cycling to produce numerous ssDNA products. The quantity of these ssDNA products was detected through microchip electrophoresis (MCE) and could be transformed to the concentration of the target gene. Moreover, the applicability of this developed strategy in detecting long genomic DNA was verified by detecting bacterial 16S rDNA. This proposed dT-SDA strategy consumes less time and has satisfactory sensitivity, which has great potential for effective bacterial screening and infection diagnosis.

Integrating silica with organic nanoparticles can generate unique properties. Here pillar[5]arene/silica hybrid vesicles were constructed based on the amphiphilic and rigid properties of pillararenes, as well as the catalytic hydrolysis of tetraethoxysilane. Such vesicles exhibited the high strength of silica and unique molecular recognition of pillararenes, both of which could tune the pH-triggered release behavior. Furthermore, a rhodamine B derivative with hexyl group (RhB-C6) was synthesized, which can form a complex with the pillar[5]arene. Based on the host-guest interaction and high strength of silica, the hybrid vesicles could load more RhB-C6 and the rhodamine B was released more slowly compared with the organic vesicles.

Extracellular pH can indicate the variation in organelle function and cell state. It is important to measure extracellular pH (pHe) with a controllable distance. In this work, a potentiometric SECM dual-microelectrode was developed to monitor the pHe of MCF-7 cells under electrical stimulation. The distance between the dual-microelectrode and the cells was determined first with a gold microelectrode by recording the approaching curve, and the pH was determined using an open-circuit potential (OCP) technique with a polyaniline-modified Pt microelectrode. The pH microelectrode showed a response slope of 53.0 ± 0.4 mV/pH and good reversibility from pH 4 to pH 8, fast response within 10 s, and a potential drift of 1.13% for 3 h, and thus was employed to monitor the pHe of stimulated cells. The value of pHe decreased with the decrease in the distance to cells, likely due to the release of H+. With an increase in the stimulation potential or time, the pHe value decreased, as the cell membrane became more permeable, which was verified by fluorescence staining of calcein-AM/PI (propidium iodide). Based on these results, this method can be widely applied for determining the species released by biosystems at a controllable position.

Potentiometric aptasensors enhanced by integrating advanced nanomaterials are of particular interest for the detection of multiplex species (e.g., proteins, bacteria, micro-organisms) due to their low cost, ease of operation, and low detection limits. However, potentiometric detection of small ionic species aptasensors is still challenging. This article describes the first example of a label-free G-quadruplex-based potentiometric aptasensing platform for the detection of Pb2+. Polyion oligonucleotide-labeled gold nanoparticles (AuNPs-DNA) as probes are modified on Au electrode, providing high-density negative charge on the electrode surface. These signal-amplifying probes can selectively form G-quadruplexes with the presence of Pb2+ ions and reduce the negative charges on the electrode surface, hence achieving potentiometric detection of Pb2+ ions with high selectivity. The AuNPs-DNA-based aptasensor shows an acceptable sensitivity over a wide range from 10−11 to 10−6 M with a detection limit of 8.5 pM. Furthermore, confirmed by coupled plasma mass spectrometry, the sensing platform is capable of performing effective and accurate detection of Pb2+ level in real water samples. The presented aptasensor offers a fast, convenient, low-maintenance, and highly sensitive alternative for on-site water pollution detections.

A PEDOT-modified Pt microelectrode was used in SECM for DNA biosensing and combined with long self-assembled DNA concatemers to realize dual signal amplification. The approach curve could also be plotted for tip location using this modified microelectrode with no impact on the catalytic effect so that both signal amplification and tip locating were achieved in one single tip. The detection limit of this method reached 0.076 fM, providing an ultra-sensitive DNA biosensing platform. Furthermore, this strategy could be applied in scanning a DNA chip, showing great potential in high-throughput bioanalysis with high sensitivity.

In this study, a novel all-solid-state ion selective electrode (ASS-ISE) was developed for the detection of Cu2+ by open circuit potential (OCP) based on phytic acid (PA)@Ag, which forms a thin anion layer interacting with positive charged Cu2+. Due to the excellent conductivity and complexing ability with multi-chelating features, PA can selectively recognize metal ions and execute ion-electron conduction. Moreover, with the assistance of Ag nanoparticles, multiple PA molecules were connected, forming a network structure with the improved conductivity and stability. After optimizing the thickness of PA@Ag film, this ASS-ISE gave a near Nernstian behavior (31.3 ± 1.8 mV/dec) towards the variation of Cu2+ concentration in the range of 1.0 × 10−5 to 1.0 × 10−3 mol/L with a detection limit of 2.7 × 10−6 mol/L, and presented excellent selectivity and stability. Furthermore, it was applied in the analysis of Cu2+ in environmental waters with the satisfactory recoveries, and the results were consistent well with those obtained by inductively coupled plasma atomic emission spectrometer, providing a promising alternative for the on-site detection of Cu2+ with simplicity and reliability.

Cigarette smoke contains abundant toxicants, and profiling its cytotoxicity represents a critical topic. In this study, cell-substrate impedance sensing (ECIS) was used to measure the cytotoxicity of 4‑(methylnitrosoamino)‑1‑(3‑pyridinyl)‑1‑butanone (NNK), nicotine, and the total particle material (TPM) of high-tar and low-tar cigarettes on CHO-K1 cells. Normalized impedance values at 3174 Hz were collected with microscopic imaging as an assistant, showing the dynamics of cell damage and the ability for cell self-recovery. The NI determination of the four toxicants indicated that, as the concentration of toxicants increased, cigarette smoke produced more intense toxic effects on the cells, and the ability of cell self-recovery worsened until there was permanent damage to the cells and the cells eventually died. Furthermore, the survival rate of the cells was obtained during treatment. NRU assays as a comparison were developed for evaluating the cytotoxicity by calculating the IC50. Both methods showed that the cytotoxicity decreased in the following order: the TPM of high-tar cigarettes, TPM of low-tar cigarettes, nicotine and NNK. The sensitivity of the ECIS method was higher. Our work provides a useful and convenient approach for determining the cytotoxicity of cigarettes in a real-time, label-free manner, contributing to the development of low-toxicity cigarettes.

In this study, a mixed mode stationary phase for capillary liquid chromatography (cLC) was prepared by chemical modification of glycol diglycidyl ether (EGDE) and γ-aminobutyric acid (GABA) bonded to the silica, named as Sil–EGDE–GABA. The Sil–EGDE–GABA was characterized by Fourier transform infrared spectroscopy and elemental analysis. The retention of nucleotide bases at different acetonitrile levels in the mobile phase indicated that the stationary phase possessed both hydrophilic chromatography (HILIC) and reversed-phase chromatography (RPLC) characteristics. Positional isomers, aniline compounds and a mixture of polar–nonpolar analytes were separated in RPLC mode. The stationary phase exhibited different separation mechanisms in the separation of positional isomers, compared with a commercial ODS column. Sulfonamides and biogenic amines were successfully separated in HILIC mode. These results demonstrated the application possibilities of the prepared Sil–EGDE–GABA as packing materials in cLC.

The detection of Staphylococcus aureus specific gene in combination with the mecA gene is vitally important for accurate identification of methicillin-resistant Staphylococcus aureus (MRSA). A homogeneous electrochemical DNA sensor was fabricated for simultaneous detection of mecA and nuc gene in MRSA. Metal-organic framework (type UiO-66-NH2) was applied as nanocarrier. Two electroactive dyes, methylene blue (MB) and epirubicin (EP), were encapsulated in UiO-66-NH2, respectively, and were locked by the hybrid double-stranded DNA. Based on the target-response electroactive dye release strategy, once target DNA exists, it completely hybridizes with displacement DNA (DEP and DMB). So DEP and DMB is displaced from the MOF surface, causing the release of electroactive dyes. Co-Zn bimetallic zeolitic imidazolate framework-derived N-doped porous carbon serves for electrode modification to improve electrocatalytic performance and sensitivity. The differential pulse voltammetry peak currents of MB and EP were accurately detected at − 0.14 V and − 0.53 V versus the Ag/AgCl reference electrode, respectively. Under the optimal conditions, the detection limits of mecA gene and nuc gene were 3.7 fM and 1.6 fM, respectively. Combining the effective application of MOFs and the homogeneous detection strategy, the sensor exhibited satisfactory performance for MRSA identification in real samples. The recovery was 92.6–103%, and the relative standard deviation was less than 5%. Besides, MRSA and SA can also be distinguished. This sensor has great potential in practical applications.

A programmable multitarget-response electrochemical imaging technique was presented using scanning electrochemical microscopy (SECM) combined with a self-designed waveform. The potential waveform applied to the tip decreased the charging current caused by the potential switch, enhancing the signal-to-noise ratio. This programmable SECM (P-SECM) method was used to scan a metal strip for verifying its feasibility in feedback mode. Since it could achieve simultaneous multitarget imaging during one single imaging process, PC12 cells status was imaged and identified through three different molecules (FcMeOH, Ru(NH

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main pathogens involved in hospital and community infection. To rapidly and sensitively detect the mecA gene, which is relevant to methicillin-resistant strains, microchip electrophoresis (MCE) integrated with isothermal strand-displacement polymerase reaction (ISDPR) was developed. In the ISDPR signal recycle amplification, the target DNA opened the DNA hairpin structure by specifically binding with the hairpin probe (HP), and then the primer hybridized with the probe and released the target DNA in the presence of Klenow Fragment exo− (KF exo−) polymerase. The released target DNA hybridized with the next HP and then was displaced by the primer again, consequently achieving target recycling and amplification. The amplified products of the HP-cDNA duplex were separated rapidly from other DNAs by MCE. Under optimal conditions, the limit of detection of the target DNA was as low as 12.3 pM (S/N = 3). The proposed ISDPR with MCE method was also successfully applied to detect methicillin-resistant S. aureus, and the experimental results showed that it had some advantages such as being label free, ultrasensitive, rapid and well separated.

An electrochemical sensor based on dual functional Cu2+-modified metal–organic framework nanoparticles (Cu2+-NMOFs) for sensitive detection of bacterial lipopolysaccharide (LPS) is reported. Cu2+-NMOFs were prepared and characterized by SEM, EDS, XRD, and XPS. In this LPS sensor, LPS firstly immobilized in gold nanoparticles/reduced graphene oxide by C18 alkane thiol chains, since the LPS can interact with the C18 alkyl chains by strong intermolecular interactions. Then the Cu2+-NMOFs were captured by the anionic groups of the carbohydrate portions of LPS molecules and played a vital role of recognition unit. More importantly, the Cu2+-NMOFs can catalyze dopamine oxidation to generate aminochrome, resulting in a strong electrochemical oxidation signal. The electrochemical sensor based on dual functional Cu2+-NMOFs was investigated by differential pulse voltammetry, and the stripping peak currents of dopamine oxidized to aminochrome were used to monitor the level of LPS. The developed method demonstrated a wide linear range from 0.0015 to 750 ng/mL with a limit of detection of 6.1 × 10−4 ng/mL. The fabricated sensor was applied to detect LPS in mouse blood serum and satisfactory results were achieved. Compared to other detection schemes by using the LPS-binding proteins, peptides, and aptamer, the proposed LPS determination based on the catalytic peroxidase-mimicking NMOFs has some advantages such as good reproducibility, low detection limit, and excellent specificity.

Simultaneous detection of various intracellular biomarkers is promising for early diagnosis and treatment of cancer. Herein, a split primer ligation-triggered catalyzed hairpin assembly-based on dual-signal electrochemical biosensor was constructed for the determination of two pairs of cancer mRNAs: TK1 and c-myc, survivin and GalNAc-T by using ferrocene molecular beacon and hemin molecular beacon as detection signal sources. Each pair of targets exists simultaneously, can release the split primers and ligated as the integral primers, hybridization occurred between the integral primers and part of MBs, causing a double-stranded DNA formed. The probes hybridized with the unfolded MBs and displaced integral primers. Finally, the displaced integral primers again hybridized with the MBs and initiated cycle amplification. Under the optimal conditions, the detection limit of TK1 and c-myc mRNA is as low as 0.022 nM, and that of survivin and GalNAc-T mRNA is 0.029 nM. In addition, two pairs of cancer mRNAs could act as outputs to activate an AND logic gate.

The detection of Staphylococcus aureus (S. aureus) is very important as it is responsible for bacterial infectious diseases and food poisoning. In this paper we explored the application of fluorescently labelled vancomycin to specifically bind and detect S. aureus. In view of the specificity of vancomycin towards bacterial cell surfaces, we utilized Cy5 to label vancomycin (Cy5-Van) for the identification of S. aureus. Our experiments were designed to examine in greater detail the specificity of the reaction between Cy5-Van and S. aureus. Detection parameters such as the derivatization conditions, concentrations of buffer, pH value, response performance of Cy5-Van to bacterial surface, injection time and reversed-polarity time have been investigated and optimized. To develop a simple and quick assay for the detection of S. aureus at low concentrations, we propose to use the Cy5-Van for labeling the S. aureus coupled with an on-line multiple-concentration in microchip electrophoresis. Under the optimized conditions, the detection of S. aureus was achieved within 150 s with limit of detection (S/N = 3) of 981 CFU/mL, and 350-fold enhancement was obtained for S. aureus as compared to using the no concentration step. It is self-evident that this approach has great potential in the future for the analysis of S. aureus.

In this study, distinguishing skin cancer cells (A431) and normal cells (HaCaT) was achieved using electrical impedance spectroscopy (EIS) with a novel developed device. The proliferation behaviors of the two cell types during a culture period of 5 days were characterized by the normalized impedance measured at 1465 Hz with simultaneous microscopic imaging for assistance. By fitting to the established equivalent circuits, A431 cells generated smaller resistance (Rc) values with smaller increasing variation, and comparable capacitance (Cc) values with similar decreasing variation compared with HaCaT cells. Moreover, Cc values were linearly correlated to the cell number. The results indicate that these two cell types can be distinguished with EIS based on the differences in the values and variation trends of Rc and Cc during the proliferation process in a real-time and label-free manner. Our work supplies a useful analytical approach for skin cancer cell research and may facilitate the early diagnosis of skin cancer.

A novel electrochemical DNA (E-DNA) biosensing strategy was designed and used for the detection of breast cancer susceptibility gene (BRCA-1). The biosensor was based on gold nanoparticles-reduced graphene oxide (AuNPs-GO) modified glass carbon electrode (GCE) covered with the layer of molecularly imprinted polymers (MIPs) synthesized with rhodamine B (RhB) as template, methacrylic acid (MAA) as the monomer, and Nafion as additive. The signal amplification tracing tag SiO2@Ag NPs were prepared by covering AgNPs on the surface of SiO2 nanoparticles in situ, and then DNA probes were modified on AgNPs by Ag-S bond, forming the composites SiO2@Ag/DNA. In presence of target DNA (T-DNA), homogeneous hybridization was performed with SiO2@Ag/DNA and RhB labeled DNA, and the resulting SiO2@Ag/dsDNA/RhB was specifically recognized by MIPs via the interaction between imprinting cavities and RhB. Under optimal conditions, the proposed biosensor exhibited wide linear range from 10 fM to 100 nM, low detection limit of 2.53 fM (S/N = 3), excellent selectivity, reproducibility, stability, and feasibility in serum analysis. Overall, these findings suggest the promising prospects of the proposed biosensing strategy in clinical diagnostics.

An all-solid-state potentiometric aptasensor array based on a multichannel disposable screen-printed carbon electrode (SPCE) was demonstrated for the simultaneous detection of Hg2+, Cd2+, and As3+ by open circuit potential (OCP) technology. The potential of the channel with an internal calibration DNA sequence (IC-DNA) was employed as the internal calibration potential (ICP) to subtract the background signal generated by the detection system, providing a built-in correction methodology. As a result, the developed aptasensor array showed high sensitivity and accuracy for detecting Hg2+, Cd2+, and As3+ without mutual interference or interference from other ions. The linear response ranged from 2.5 pM to 2.5 μM, and the detection limits for Hg2+, Cd2+, and As3+ were 2.0, 0.62, and 0.17 pM, respectively. Furthermore, the potentiometric aptasensor array was successfully applied for the simultaneous detection of three ions in real samples. The results obtained from the developed approach agreed well with the re...

The detection of Salmonella enterica serovar Typhimurium (S. Typhimurium) is very important for the prevention of food poisoning and other infectious diseases. Here we reported a simple and sensitive strategy to test S. Typhimurium by microchip capillary electrophoresis couple with laser-induced fluorescence (MCE-LIF) based on the specific reaction between the bacterium and corresponding aptamers. Based on the differences in charge to mass ratio between bacteria-aptamer complexes and free aptamers, a separation of the complexes and free aptamers could be obtained by MCE. The optimal parameters of the specific reaction including fluorescent dye concentration, Mg2+ concentration, incubation time, and pH of incubation solution were carefully investigated. Meanwhile, a non-specific DNA was exploited as a contrast for the detection of S. Typhimurium. Under the optimal conditions, a rapid separation of the bacteria-aptamer complex and free aptamers was achieved within 135 s with a limit of detection (S/N = 3) of 3.37 × 102 CFU mL−1. This method was applied for the detection of S. Typhimurium in fresh milk samples and a recovery rate of 95.8% was obtained. The experimental results indicated that the specific aptamers are of enough biostability and the established method could be used to analyze S. Typhimurium in foods.

Skin wound healing represents a critical medical topic. For its ideal case, the injured tissue can repair quickly without scars. In this paper, an ECIS device was developed using nano-grooves to simulate internal extracellular matrix (ECM) with 75 nm in depth and 200 nm in width of grooves and ridges. HFF and HaCaT cells were cultured but only HFF cells could orient along the nano-grooves. In the cell migration and proliferation occurred during the wound healing, HFF and HaCaT cells both presented increased normalized impedance (NI) values at the characteristic frequencies of 977 Hz and 1465 Hz, respectively. Compared to flat electrodes, nano-grooves electrodes generated less intense impedance signals in HFF cell migration and proliferation, and HaCaT cell migration, but more intense ones in HaCaT cell proliferation. Cell images were captured simultaneously and the statistical analysis demonstrated that the nano-grooves electrode could accelerate the migration while slow down the proliferation. After establishing the correlations between impedance response and cell behaviors, it could be found that the NI values increased all linearly the rising of recovery degree and cell number. Under the equal changes of recovery degree and cell number on nano-grooves, HFF cells produced the both declined impedance signals, because of the elongation, while, HaCaT cells created the same and deduced NI variation rates, due to the unchanged morphology and aggregation growth, respectively. Our work provides a useful approach for the clinical monitoring of skin wound healing in a real-time and label-free manner, potentially promoting the development of regenerative medicine.

Herein we propose a multiple signal amplification strategy designed for ultrasensitive electrochemical detection of glycoproteins. This approach introduces a new type of boronate-affinity sandwich assay (BASA), which was fabricated by using gold nanoparticles combined with reduced graphene oxide (AuNPs-GO) to modify sensing surface for accelerating electron transfer, the composite of molecularly imprinted polymer (MIP) including 4-vinylphenylboronic acid (VPBA) for specific capturing glycoproteins, and SiO2 nanoparticles carried gold nanoparticles (SiO2@Au) labeled with 6-ferrocenylhexanethiol (FcHT) and 4-mercaptophenylboronic acid (MPBA) (SiO2@Au/FcHT/MPBA) as tracing tag for binding glycoprotein and generating electrochemical signal. As a sandwich-type sensing, the SiO2@Au/FcHT/MPBA was captured by glycoprotein on the surface of imprinting film for further electrochemical detection in 0.1 M PBS (pH 7.4). Using horseradish peroxidase (HRP) as a model glycoprotein, the proposed approach exhibited a wide ...

A new method of capillary electrophoresis (CE) using laser induced fluorescence (LIF) detection via online pre-concentration techniques including transient trapping combined with the dynamic pH junction mode was developed for the sensitive determination of glutathione in biological samples. The mechanism together with the important parameters governing the pre-concentration and separation were investigated in order to obtain maximum resolution and sensitivity. The analytes were compressed into a narrow zone due to the effect of the dynamic pH junction mode, and then transiently trapped by SDS micelles at the interface of the sample and micellar areas. Under the optimal conditions, the limits of detection for reduced glutathione, glycine, oxidized glutathione, cysteine, and glutamic acid were 0.01, 0.01, 0.5, 0.7, and 0.1 nM (S/N = 3), respectively. The enhancement factors obtained when using the transient trapping combined with the dynamic pH junction mode as a pre-concentration process were enhanced from 87 to 430 when compared to the results obtained by the classical capillary zone electrophoresis (CZE) mode. Moreover, this optimized method was successfully applied to bacteria (Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus) and HaCaT cell samples for the determination of reduced glutathione with satisfactory recoveries.

We reported the use of polydopamine/Au nanoparticles/DNA (PDA/Au NPs/DNA) as a stationary phase for the separation of tryptophan enantiomers by microchip capillary electrophoresis (MCE). The stationary phase was formed by sequentially immobilizing PDA/Au NPs and DNA to the glass microfluidic channel surface using layer-by-layer assembly. The formation of PDA/Au NPs as a functional film involved the use of HAuCl4 as an oxidant to trigger DA self-polymerization. DA was then used as a reductant to reduce HAuCl4 to Au NPs. All these Au NPs were simultaneously deposited on the microchip surface by the adhesive PDA, and the thiolated DNA was strongly adsorbed onto the glass microfluidic channel surface through covalent gold–sulfur bonding. The functional film of the PDA/Au NPs/DNA was characterized by scanning electron microscopy, UV-vis spectra and ATR-FT-IR. The influence of separation voltage and the concentration and pH value of the running buffer were found to significantly influence separation. Successful baseline separation of tryptophan enantiomers was achieved within 65 s utilizing an effective separation length of 33 mm, and coupling with laser-induced fluorescence detection resulted in a resolution factor of 2.95. All these evaluation parameters, including stability and reproducibility, were considered satisfactory. The method outlined here, using the PDA/Au NPs/DNA-coated microfluidic channel as a versatile platform, may offer a processing strategy to prepare a functional surface on microfluidic chips.

The separation of chiral amino acids using microchip electrophoresis (MCE) was investigated using chiral nematic mesoporous silica (CNMS) as the chiral stationary phase, with hydroxypropyl-β-cyclodextrin (HP-β-CD) as the chiral selector. Individually, neither CNMS nor HP-β-CD achieved separation, so they were combined. Ten chiral amino acids (phenylalanine, tryptophan, glutamic, alanine, serine, aspartic acid, cysteine, methionine, tyrosine, and histidine) were selected as the model analytes. Under optimized conditions, we achieved baseline separation of six chiral amino acids, and the other four chiral amino acids displayed improved resolution. These results indicate the presence of a synergistic effect between CNMS and HP-β-CD, showing that the combination of a chiral stationary phase and a chiral additive is a promising approach for enantioseparation using MCE.

Herein we show that by appending bulky β-cyclodextrin (CD) groups onto sheet-forming peptoids, we obtain cylindrical micelles that further assembly into membranes and intertwined ribbons on substrates in aqueous solution, depending on the choice of solution and substrate conditions. In situ atomic force microscopy (AFM) shows that micelle assembly occurs in two steps, starting with "precursor" particles that transform into worm-like micelles, which extend and coalesce to form the higher order structures with a rate and a degree of cooperativity dependent on pH and Ca2+ concentration. After co-assembly with hydrophobic 4-(2-hydroxyethylamino)-7-nitro-2,1,3-benzoxadiazole (NBD) donors that occupy the hydrophobic core, followed by exposure to hydrophilic Rhodamine B as acceptors that insert into cyclodextrin, the micelles exhibit highly efficient Forster resonance energy transfer efficiency in aqueous solution, thereby mimicking natural light harvesting systems.

Different cells respond differently to environmental stimulation, resulting in different extracellular pH values. Therefore, the pH of the extracellular microenvironment (pHe) is an important manifestation of cell response to the environment. In this study, a pH-selective dual-microelectrode tip was used as the probe tip of a scanning electrochemical microscopy (SECM) instrument to in situ monitor the pHe changes of different cells after being electrically stimulated by the SECM potential method. pHe is the pH at a certain distance from the cells, and the distance is determined by substituting the current measured by the approach curve into a theoretical calculation. A gold microelectrode was used to determine the distance between the dual-microelectrode tip and the cell, and a pH-selective microelectrode was used to measure the pHe. It was found that the pHe value was related to the distance between the pH-measuring electrode and the cell, and different types of cells had different pHe changes after electrical stimulation. Through fluorescent staining with calcein-AM and propidium iodide, it was verified that this phenomenon was caused by changes in the permeability of the cell membrane due to electrical stimulation. In situ monitoring the pHe changes of different cells will be helpful for exploring the response of cells to environmental stimulation and the mechanism of these different responses.

As a kind of malignant tumor, breast cancer needs more simple and sensitive diagnosis methods. Exosomes, a novel cancer marker, have the potential to be used in cancer biopsy alternative surveillance. Thus, the determination of the correlation between cancer cells and their exosome composition is of significance. Herein, an electrochemiluminescence (ECL) aptasensor has been designed to detect the MUC1 protein expression on breast cancer cells and their derived exosomes. CD63 aptamer was immobilized on the electrode surface to capture the cells and exosomes, and Ru(bpy)32+@SiO2 nanoparticles (Ru@SiO2 NPs) modified with MUC1 aptamer could recognize specifically MUC1 protein on cells and exosomes. The amplified ECL signal from Ru@SiO2 NPs exhibited linear responses in the range of 7.53 - 753 μg/mL with a limit of detection (LOD) of 0.83 μg/mL for MCF-7 cells, as well as linear range of 3.22 × 10−4 - 156 μg/mL with a LOD of 2.73 × 10−4 μg/mL for their exosomes. The expression of MUC1 protein on the surface of MDA-MB-231 and SK-BR-3 cells and their exosomes, were further analyzed, indicating the consistency of MUC1 expression of breast cancer cells and their exosomes. Furthermore, this aptasensor was applied to the determination of MUC1 protein on exosomes in serum samples of patient and normal control, demonstrating its potential for clinical cancer surveillance.

Recently, many strategies have been developed to trace the breast cancer susceptibility gene (BRCA), which is closely related to the occurrence of breast cancer. In this work, a novel recyclable electrochemical sensing platform was constructed to detect BRCA DNA based on the homogeneous hybridization of this target sequence with ferrocene-labeled DNA/Au nanospheres (FcNS) and horseradish peroxidase-labeled DNA/Au nanospheres (HRPNS) concatamers, and the host-guest interaction between cucurbit [7]uril (CB [7]) adsorbed on the electrode and Fc on the hybridization complex. With the optimization of experimental conditions, the fabricated sensing platform showed improved sensitivity with a low detection limit of 25 pM (S/N = 3), contributed by the dual amplification of signal using FcNS and HRPNS concatamers, and high specificity for BRCA DNA. The captured complex was dissociated from CB [7]-modified electrode with the rise of pH value to recycle the sensing platform. Furthermore, this detection strategy displayed the reliability and applicability in the analysis of human serum samples, indicating great potential for applications in early diagnosis of breast cancer.

A capillary column was prepared by continuously packing ostadecylsilane (ODS) and taurine derivatized silica (TDS) in one column without interface. This continuously packing chromatography (CPC) column is easy to operate, has good stability and shows simultaneously separation of both polar and non-polar compounds. The simultaneous separation of a series of complex samples with highly hydrophobic components (benzene, toluene, ethylbenzene, and PAHs) and highly hydrophilic components (biogenic amines, bases and nucleosides) using this CPC method was investigated. The relative parameters such as the volume fraction of acetonitrile and length of the ODS and the TDS phases were investigated and optimized. The experimental results show that this column combines the advantages of both ODS and TDS stationary phases, and exhibits a reversed phase liquid chromatography (RPLC) mode followed by a hydrophilic interaction liquid chromatography (HILIC) mode when 80% of acetonitrile was used in the mobile phase. The satisfactory results indicate that the CPC method provides an easy way to simultaneously separate polar and non-polar compounds.

Due to their unique physical and chemical properties, 2D materials have attracted intense interest for applications in filtration, sensing, nanoelectronics, and biomedical devices. Peptoids are a class of biomimetic sequence-defined polymers for which certain amphiphillic sequences self-assemble into 2D crystalline materials with properties that mimic those of cell membranes. In this study the ability of these membrane-like materials to self-repair following damage on a range of substrates is explored. In situ atomic force microscopy (AFM) is used to both create damage and image the subsequent repair process. Damage is induced by using the AFM to scribe peptoid-free patterns within a preassembled membrane. The results show here that, upon introduction of a peptoid-containing solution, for a suitable range of pH conditions, the damage is eliminated through assembly of the peptoids at the newly created edges, regardless of whether the substrates are negatively or positively charged and even in the absence of an underlying surface. The rate of the advancing edge depends on the edge orientation, the pH, and the composition of the substrate. Moreover, if the solution contains a second peptoid having an identical sequence in the hydrophobic block, repair of the defects results in nanoscale patterns of the new peptoid, even if the hydrophilic regions are distinct. Consequently, this ability to self-repair can be exploited to create nm-sized patterns of distinct functional groups within a single coherent membrane.

Microchip electrophoresis (MCE) is particularly attractive as it provides high sensitivity and selectivity, short analysis time and low sample consumption. An on-line preconcentration strategy combining field-amplified stacking (FASS) and reversed-field stacking (RFS) was developed for efficient and sensitive analysis of neurotransmitters in real urine samples by MCE with laser induced fluorescence (LIF) detection. In this study, the multiple-preconcentration strategy greatly improves the sensitivity enhancement and surpass other conventional analytical methods for neurotransmitters detection. Under optimal conditions, the separation of three neurotransmitters (dopamine, norepinephrine and serotonin), was achieved within 3min with limits of detection (S/N=3) of 1.69, 2.35, and 2.73nM, respectively. The detection sensitivities were improved by 201-, 182-, and 292-fold enhancement, for the three neurotransmitters respectively. Other evaluation parameters such as linear correlation coefficients were considered as satisfactory. A real urine sample was analyzed with recoveries of 101.8-106.4%. The proposed FASS-RFS-MCE method was characterized in terms of precision, linearity, accuracy and successfully applied for rapid and sensitive determination of three neurotransmitters in human urine.

In this work, a recyclable electrochemical sensing platform to detect breast cancer susceptibility gene (BRCA) was constructed by pillararenes based host–guest recognition and homogeneous DNA hybridization. BRCA target DNA (T-DNA) formed sandwich-type DNA via homogeneous hybridization with methylene blue labeled signal DNA and alkylamino modified capture DNA, which could form complexes with pillararenes. Such sandwich-type DNA was captured by a novel trithiocarbonate modified pillar[5]arene (P5A-CTA) which was immobilized on the Au electrode. With the help of enzyme amplification, the electrochemical detection signal of target DNA in sensing platform was apparently amplified. This sensing platform exhibited wide linear range and excellent specificity, and was particularly recyclable after simple washing with hot acetonitrile due to the reversible host–guest complexation between P5A-CTA and alkylamino modified DNA.

A novel label-free electrochemical strategy was designed for multi-sites recognizing the guanine-rich DNA (G-rich DNA) with surface molecular imprinting polymer composite, in which the multi-walled carbon nanotubes (MWNCTs) were regarded as supporting material and the molecularly imprinted polymer (MIP) with guanine sites of DNA was applied as recognition element. Firstly, the vinyl groups were grafted onto the surface of carboxylic acid-functionalized MWNCTs (MWCNTs-COOH) through chemical modification. Then, the composite of MWCNTs-MIP was fabricated by the selective copolymerization of methacrylic acid, ethylene glycol dimethacrylate and guanine on the vinyl group-functionalized MWNTs surface. MWCNTs-MIP was characterized by different techniques, including Fourier transform infrared (FTIR) spectroscopy, scanning electronic microscopy (SEM), cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS), showing that the MWCNTs-MIP composite was successfully prepared. Under the optimized conditions, the imprinting factor was nearly 5.68 according to the comparative slopes obtained on MWCNT-MIP and MWCNTs-non-imprinted polymer (MWCNTs-NIP), indicating that MWCNTs-MIP exhibited high selectivity for G-rich DNA. Moreover, the MWCNTs-MIP composite had a relatively wide linear range over G-rich DNA concentration of 0.05–1 μM and 5–30 μM with a detection limit of 7.52 nM (S/N = 3). Furthermore, the novel electrochemical strategy based on imprinted composite has very excellent performance in real samples of human serum and human urine.

The long DNA concatemers have been well developed to fabricate various biosensing platforms for the signal amplification. Herein, this signal amplification strategy was firstly used for an ultrasensitive scanning electrochemical microscopy (SECM)-based DNA biosensing platform. This platform was constructed through the hybridization of target DNA (TD) with thiol-tethered DNA capture probes (CP), immobilized on the gold substrate surface, and biotinylated DNA signal probes (SP), which formed then the long DNA concatemers through the continuous self-assembly with alternating DNA auxiliary probes (AP). The streptavidin-horseradish peroxidase (HRP) was linked to the long DNA concatemers through biotin-streptavidin interaction. In the HRP-catalyzed reaction, hydroquinone (H 2 Q) was oxidized to benzoquinone (BQ) with H 2 O 2 at the modified substrate surface where sequence-specific hybridization had occurred, and the BQ generated could be monitored by a SECM tip. This platform exhibited a low detection limit of 0.18 aM estimated by the 3σ rule. Combined with DNA microarrays, four kinds of TDs (100 fM) as the models were detected simultaneously by using this proposed strategy, which also demonstrated sufficient selectivity to distinguish specific DNA sequences and good reproducibility. This method opens a promising direction to improve the SECM sensitivity for high-throughput DNA detection.

A simple, economical, and sensitive capillary electrophoresis (CE) method integrated with capacitively coupled contactless conductivity detection was developed for the determination of metal ions such as K+, Na+, Mg2+, Sr2+, Ca2+ in drinking water. 18-Crown-6 ether and Hexadecyltrimethylammonium Bromide (CTAB) were employed as complexing reagents. The effects of electrolyte additives, citric acid buffer solution, and other separation conditions of CE were comprehensively investigated and carefully optimized. The best results were obtained in a running buffer solution composed of citric acid (12 mM), 18-crown-6 ether (0.2 mM), and CTAB (0.015 mM) at pH 3.5. Under these conditions, a complete separation of five metal ions was successfully achieved in less than 12 min. The limits of detection for the optimal procedure were determined to be in the range of 0.02 - 0.2 mg·L-1. The repeatability with respect to migration times and peak areas, expressed as relative standard deviations, was better than 2.3% and 5.1%, respectively. Evaluation of the efficiency of the methodology indicated that it was reliable for the determination of metal ions in six different brands of drinking water samples.

A novel Congo red (CR) derivatized silica stationary phase was prepared and packed into a fused silica capillary tube for nano-flow HPLC. A variety of analytes including poly-aromatic hydrocarbons, parabens, acids, sulfonamides, bases, and nucleosides were successfully separated using the CR. In comparison with commercial ODS columns, this new stationary phase has a different separation mechanism (hydrophobically-assisted ion-exchange), which was evident in the separation of benzoic acid derivatives and sulfonamides. The successful application of CR-bonded silica stationary phase in the HILIC and PALC modes demonstrates the effectiveness of this potential chromatographic material in nano flow HPLC.

Probe-lengthening amplification (PLA) is a target-specific nucleic acid amplification method that realizes good selectivity by effectively avoiding nonspecific amplification. Here, we propose a probe-lengthening amplification-assisted microchip electrophoresis (MCE) strategy for sensitive analysis of 16S rRNA genes of five bacteria. In this assay, four specific short probes were designed for a target bacterium to recognize its bacterial 16S rRNA gene, integrated into longer DNA ligation duplexes using Ampligase, and subsequently separated and detected by MCE. Along with the rapid generation of ligation duplexes, this approach provides exponential amplification of nucleic acid signals that are useful for sensitive bacterial quantification. Through tactfully combining PLA and MCE, the detection sensitivity of bacterial genes was significantly improved, and a limit of detection (LOD) of 30 fM was realized for the artificial target DNA. This approach was also applied to detect actual bacterial genomic samples with excellent results, demonstrating the potential application of this methodology in infection diagnosis.

A novel potentiometric aptasensor array based on a 4-channel screen-printed carbon electrode was developed with a dual-internal calibration system for the simultaneous detection of streptomycin and kanamycin. Two channels were used as working channels for assembling the aptamers of the two targets, and the other two channels acted as calibration channels. The calibration channels functioned by immobilizing two all-A sequences were employed to subtract the influence from the background matrix and further improve the detection accuracy. Consequently, under optimal conditions, this aptasensor array showed high sensitivity for the detection of streptomycin and kanamycin with detection limits of 9.66 pM and 5.24 pM, respectively, and corresponding linear response ranges of 10 pM–10 μM and 10 pM–1 μM, respectively. Moreover, it presented high specificity without mutual interference between the two targets or with other antibiotics and also demonstrated good repeatability. This aptasensor array was further applied to the simultaneous detection of streptomycin and kanamycin in real milk samples, and the results were validated by liquid chromatography-mass spectrometry (LC–MS). The results demonstrated satisfactory accuracy and precision and showed the great application potential of the aptasensor array with internal calibration for on-site detection of multiple targets.

Amyloid-β oligomers (AβOs) are highly toxic species involved in Alzheimer's disease (AD). Hence, a reliable detection method for AβOs, which are promising potential therapeutic targets and biomarkers for AD, is of great significance for improving the diagnosis of AD. Herein, a novel sandwich assay electrochemical biosensor was developed for highly sensitive and selective detection of AβO, using molecularly imprinted polymers (MIPs) and aptamer as the recognition element. Instead of using an antibody to recognize the AβO target molecules, the AβO in the samples were captured by the film of MIPs and the AβO-specific aptamer, forming a MIPs/target/aptamer sandwich assay for the highly selective detection of AβO. The AβO-specific aptamer was immobilized on the surface of core-shell nanoparticles that combined silver nanoparticles with silica nanoparticles (SiO2@Ag NPs). The highly sensitive electrochemical signal from the sandwich assay was generated by using a small amount of AβO to trigger a large number of electrochemically active Ag NPs. Under the optimized conditions, the developed biosensor showed good linearity in the concentration range of 5 pg mL−1 to 10 ng mL−1 with a limit of detection of 1.22 pg mL−1. The biosensor also showed excellent specificity, reproducibility and stability. In addition, the feasibility of detecting AβO in human serum was successfully verified, demonstrating the promising potential of this approach for clinical research and the early diagnosis of AD.

Exosomes (30–150 nm) secreted by cells play an important role in intercellular communication. Herein, a novel double imprinting-based electrochemical method has been developed for analyzing the particle size distribution (PSD) of mimetic exosomes – a mixture of SiO2@HRP with the diameters in 50 nm, 100 nm and 150 nm at a ratio similar to the exosomes. Double imprinting polymers (DIP) were synthesized with SiO2@HRP at different sizes as template, providing the both recognition of size and morphology. With the capture of the target and the binding of the signal amplification tag – SiO2@Ag/MPBA on the DIP film, a sandwich structure was constructed on Au NPs-GO modified glassy carbon electrode. Under the optimal conditions, the DIP film exhibits the linear correlations between the current intensity and the logarithmic concentration of SiO2@HRP as ΔI50 = −1.52 + 0.50 × lgc50 (2.89 × 104–2.89 × 109 particles/mL), ΔI100 = −1.61 + 0.48 × lgc100 (2.89 × 104–2.89 × 109 particles/mL) and ΔI150 = −1.54 + 0.49 × lgc150 (5.75 × 104–5.75 × 109 particles/mL) with the limit of detection of 1.44 × 103 particles/mL, 5.68 × 102 particles/mL and 7.70 × 102 particles/mL, respectively. Furthermore, the DIP film was applied to the PSD analysis of mimetic exosomes – SiO2@HRP at mixed sizes with a ratio of 50 nm:100 nm:150 nm = 5.0%:42.5%:52.5% detected by nanoparticle tracking analysis (NTA), obtaining a similar result of 50 nm:100 nm:150 nm = 3.6%:43.0%:53.4% with small relative concentration errors. It also exhibited excellent reproducibility and stability. This double imprinting-based method shows high potential in the separation and detection of complex biosamples.

The specific and sensitive detection of multiple pathogens is critical for the prevention and identification of health- and safety-related problems. A microchip electrophoresis/LED-induced fluorescence (MCE-LIF) method, combining an aptamer-based probe and a novel universal primer-duplex polymerase chain reaction (PCR) process (UP-DPCR), was designed to simultaneously detect two kinds of bacteria. The probe consists of a recognition unit (aptamer) for specifically capturing bacterial cells and eventually releasing complementary DNAs (C1 and C2). The two released DNA strands (C1 and C2) can be simultaneously amplified by a pair of universal primers, because of the identical sequences designed at both ends of the two DNA strands. The UP-DPCR products of C1 and C2 can be separated and detected by MCE-LIF, and the heights of the two peaks are correlated with the concentrations of the corresponding bacteria. Here, Salmonella enterica serovar Typhimurium (S. Typhimurium) and Pseudomonas aeruginosa (P. aeruginosa) were detected as a proof of concept. Under optimal conditions, the limits of detection (S/N = 3) were 15 CFU mL−1 for S. Typhimurium and 5 CFU mL−1 for P. aeruginosa. This approach was also applied for detecting these two types of bacteria in defatted milk, indicating its potential application in the analysis of real samples. This method can not only simultaneously detect two kinds of bacteria without lysing the bacterial cells, but also simplify duplex PCR with the use of universal primers.

Because foodborne pathogenic bacteria are in a great variety and may cause many infectious diseases even at low concentrations, a highly sensitive and selective method has long-been desired for bacteria detection. In this study, a microchip electrophoretic method for biosensing E. coli O157:H7 was developed by using E. coli O157:H7 aptamer (apt-E) for specific bacteria recognition together with aptamer-induced catalysed hairpin assembly (CHA) for significantly improving the sensitivity of bacteria detection. Briefly, three nucleic acid strands (apt-E, hairpin H1, and H2) were used in the CHA amplification. Because different quantities of H1/H2 complexes were formed due to the circle amplification induced with different amounts of apt-E and the correlation between the concentrations of apt-E and E. coli O157:H7, E. coli O157:H7 thus could be quantified by the detection of H1/H2 complexes with microchip electrophoresis (MCE). Under the optimal conditions, the limit of detection was 75 CFU mL−1. This method was also applied to detect E. coli O157:H7 in defatted milk with a satisfying recovery rate. The proposed strategy for E. coli O157:H7 detection is label-free, enzyme-free, ultra-sensitive, and cost-effective. It is also practical and could be applied to detect other bacteria in food samples.

The release of cytochrome C (Cyt C) plays an important role in apoptosis. In this study, selective and sensitive detection of Cyt C based on an aptamer strategy coupled with MCE was developed. Following the binding of a specific aptamer to Cyt C, the aptamer exhibited an irregular state, reducing the binding affinity of a fluorescent probe, and thus preventing the aptamer-Cyt C complexes from detection within the MCE. The height of the detection peak of the residual aptamer linearly decreased, and therefore, the difference in peak height of residual aptamer compared to that of the initial aptamer was used to quantify the captured protein concentration. Experimental conditions such as incubation time, pH, temperature, and ionic strength were optimized. A measurement of Cyt C concentration by MCE was achieved within 135 s, with a limit of detection as low as 0.4 nM. The proposed method has high selectivity and good stability for the detection of Cyt C. The experimental results demonstrate that this method is quick, consumes only a small quantity of sample, is highly selectivity and exhibits high sensitivity.

Foodborne bacteria are some of the most important human pathogens and can cause many diseases. In this study, multiplex PCR amplification combined with microchip electrophoresis (MCE) was studied to simultaneously and sensitively detect Staphylococcus aureus, Proteus mirabilis, and Enterobacter sakazakii. In order to simultaneously and accurately detect the aim bacteria, three pairs of primers were specially designed for the multiplex PCR amplification of the target genes of three bacteria, which were the specific genes corresponding to these bacteria respectively. After the DNA fragments of three bacteria were simultaneously extracted, the multiplex PCR amplification was performed by adding the three pairs of specific primers in the mixed DNA fragments solution. The multiplex PCR products of the three food-borne pathogens were analyzed by MCE and the limits of detection of target DNA fragments were 1.2-2.2ngμL-1, (S/N=3). The limits of detection of the aim bacteria were calculated as 53CFUmL-1 for Enterobacter sakazakii, 32CFUmL-1 for Proteus mirabilis, 28CFUmL-1 for Staphylococcus aureus, respectively. Satisfactory results were obtained when this method was applied to detect the three foodborne bacteria in milk samples. The experimental results show that this method has the advantages of quickness, less sample consumption, high selectivity and high sensitivity.

Herein, a novel and convenient electrochemically active-inactive switching molecular beacon based on hemin (Hs-MB) has been designed for easy discrimination of single nucleotide polymorphisms (SNPs) and sensitive detection of insulin. The electrochemically active changing capability of Hs-MB is based on two identical hemin groups labeled at both ends of MB sequence in dimer or monomer forms depending on the conformation of MB which is in stem-loop structure or line shaped structure. The Hs-MB assay permits discrimination of SNPs and the highly sensitive and specific detection of insulin with detection limit successively as low as 0.5 pmol/L. Even at a very low target concentration, the Hs-MB assay also shows a good specificity in the presence of other potentially interfering components. The experimental results also show that Hs-MB can also be used for the accurate and rapid monitoring of insulin secretion by glucose-stimulated from MIN6 cells at different time periods, demonstrating that Hs-MB has potential in monitoring of biomarker variation in vivo.

A rapid and sensitive PCR based strategy in combination with microchip capillary electrophoresis (MCE) was employed to simultaneously detect three foodborne pathogenic bacteria. Three pairs of primers were specially designed for the amplification of target genes from Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella enterica serovar Typhimurium (S. Typhimurium). The PCR products along with standard DNA fragments were employed to optimize the separation conditions in MCE. Under optimal conditions, detectable separation of the PCR products (1.6–3.5 ng μL−1) from the three foodborne pathogenic bacteria was achieved within 135 s. The limits of detection of the three bacteria were concluded to be as low as 45 CFU mL−1 for E. coli, 62 CFU mL−1 for S. aureus and 42 CFU mL−1 for S. Typhimurium. The RSD of migration time was in the range of 0.5–0.8%. We conclude that MCE along with PCR holds real potential for rapid analysis and detection of nucleic acids from routine foodborne pathogenic bacteria.

Porous organic cages composed of discrete cage molecules have attracted considerable recent attention as gas adsorption materials and separation media. In this study, we report a homochiral porous organic cage CC5 with a large cavity and pore windows as a novel stationary phase for high-resolution gas chromatographic separations. The capillary column was prepared by a static coating method. A large number of racemic compounds have been resolved on the coated capillary column, including derivatized amino acids, alcohols, alcohol amines, esters, ethers, ketones, and epoxides. It is interesting that the CC5-coated capillary column exhibits significant chiral recognition complementarity to a commercial β-DEX 120 column and a previously reported homochiral porous organic cage CC3-R-coated column, which could expand the range of the analytes amenable to separation on porous organic cage-based capillary columns. Moreover, the fabricated column also shows excellent selectivity for the separation of positional isomers, including the challenging ethylbenzene and xylene isomers. Experimental results demonstrate an excellent separation performance and stability of the CC5-coated column, making it promising for gas chromatography applications.

In this paper, polydopamine/gold nanoparticles (PDA/Au NPs) were used to construct a functional film on a glass microfluidic channel surface in microchip electrophoresis (MCE) for the separation of reduced glutathione (GSH) and oxidized glutathione (GSSH). The formation of the PDA/Au NPs was characterized by scanning electron microscopy, transmission electron microscope, UV–Vis spectra and ATR-FTIR. An online pre-concentration strategy involving field-amplified sample stacking was used to determine the sensitivity of the assay for measuring GSH and GSSH in bacteria (Escherichia coli, Staphylococcus aureus and Salmonella enterica serovar Typhimurium) and HaCaT cells samples by MCE with laser-induced fluorescence detection. The influences of the separation voltage, the concentration of the running buffer and the pH value of running buffer, were carefully investigated. Using this studied method, GSH and GSSH could be simultaneously pre-concentrated and separated within 70 s. The limits of detection of GSH and GSSH were as low as 0.81 and 0.91 nM, respectively (S/N = 3), which corresponded to approximately 180–301-fold improvements in peak height. Moreover, this method was successfully applied to the analysis of bacteria (E. coli, S. aureus and S. typhimurium) and HaCaT cell samples with a satisfactory recovery rate.

Bacterial lipopolysaccharides (LPS) are endotoxins, which can cause fever, inflammation, cell and tissue damage, irreversible septic shock and death in mammals as well as other organisms. Herein, a highly sensitive and selective strategy was proposed for detecting LPS using microchip electrophoresis (MCE) based on aptamer-modified magnetic beads and polymerase chain amplification. In this strategy, the biotinylated aptamer for the LPS (LBA) was hybridized partially with the complementary DNA (cDNA), then the double-stranded DNA obtained was immobilized onto the magnetic beads. In the presence of target LPS, the target-aptamer complex was formed and the cDNA would be freed. After a magnetic separation, the cDNA was released into the supernatant and subsequently triggered the polymerase chain amplification. This process eventually generated a large number of output DNA, which could be quantitatively detected by MCE. With the polymerase chain amplification, this designed protocol provided an ultrasensitive detection of LPS down to the 1.1 × 10−14 g/mL with a linear range of 5 orders of magnitude. The proposed method also exhibited a high specificity toward LPS in the presence of other common interfering substances. Moreover, the assay showed a good practical application for LPS determination in serum samples.