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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.

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.

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.

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.

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.

In this work, we demonstrate the applicability of an electrochemical supramolecular platform to detect Hepatitis B virus (HBV) sequences. A DNA molecular beacon was designed as the probe, and immobilized onto the electrodes through the biotin at the 3′-end, while the 5′-end of the probe was labeled with 4-(4-dimethyl aminophenylazo) benzoic acid (dabcyl). The β-cyclodextrins functionalized Au nanoparticles (Au-CDs) were employed as electrochemical signal provider. The probe DNA immobilized on the electrode kept the stem-loop configuration, which shielded dabcyl from docking with Au-CDs in solution due to the steric effect. While in the presence of the target DNA, the probe conformation was changed and a double-stranded DNA (dsDNA) molecule was formed through the hybridization. Consequently, Au-CDs were linked to dsDNA owing to the host–guest recognition between β-CD and dabcyl. Thus, the hybridization events could be sensitively transduced to electrochemical signals provided by Au nanoparticles. The designed sensor favored discrimination between the healthy and single-nucleotide polymorphisms (SNP)-containing sequences. Under optimized detection conditions, the proposed method showed high sensitivity and specificity with a detection limit of 3.00 × 10 −13 M for HBV DNA sequence.

A three-dimensional glassy carbon electrode (GCE) was fabricated from one-dimensional multiwalled carbon nanotubes (MWCNTs) and two-dimensional graphene (GR), using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) ionic liquid to improve its dispersibility and stability. This GR/MWCNTs/BMIMPF6 modified GCE was found to be a highly sensitive electrochemical sensor for the simultaneous determination of hydroquinone (1,4-dihydroxybenzene, HQ) and catechol (1,2-dihydroxybenzene, CT). The GR was characterized using a transmission electron microscope. The electrochemical behaviours of HQ and CT at the GR/MWCNTs/BMIMPF6/GCE were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The chemically modified electrode exhibited excellent electrochemical catalytic activities towards HQ and CT. Linear relationships between the oxidation peak current and concentration of HQ/CT were obtained in the ranges 0.5 μM to 2.9 mM and 0.2 μM to 0.66 mM with detection limits (S/N = 3) of 0.1 μM and 0.06 μM, respectively. This GR/MWCNTs/BMIMPF6/GCE showed many advantages in terms of dispersibility, stability, sensitivity, facility and economy.

The electrochemical monitoring of glucose consumption is relevant for cell biology studies because of its wide detection range, high sensitivity and easy implementation. Whereas the glucose consumption and cell growth rate can be tightly correlated, they should also be cell population density dependent. In this work, we fabricated high sensitive enzyme electrodes for accurate monitoring of glucose consumption of cells in different growth stages. The performance of the fabricated device was firstly evaluated by cyclic voltammetry (CV) with p-benzoquinone (PBQ) as redox mediator, showing a linear response over a wide detection range (0.3–60 mM), a high sensitivity (1.61 ± 0.10 μA mM−1 mm−2 (n = 5)) and a low detection limit (80 μM). Then, daily glucose consumptions of NIH 3T3 cells in 24-well plates were determined for a period of 7 days. The results could be compared to the cell population growth curve, showing a close correlation but different behavior. We found that the increase of the glucose consumption took place prior the cell number increase but the glucose consumption per cell decreases linearly in the exponential growth stage of cells.

An effective method for selective immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy) 3 2+ ) onto one target electrode surface based on the electrodeposition of RuDS NPs (Ru(bpy) 3 2+ doped silica nanoparticles)/chitosan composite film is presented in this paper. Ru(bpy) 3 2+ was selectively deposited onto four individual electrodes in an Au electrode array. The results demonstrate the possibility of selective immobilization of Ru(bpy) 3 2+ onto array electrodes and selective immobilization of different ECL composite. Therefore have potential applications in bioanalysis, capillary electrophoresis and drug screening. RuDS NPs and the resulting composite film were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and Field emission-scanning electron microscope (FE-SEM). The electrochemiluminescence (ECL) sensor based on the composite film modified electrode exhibited excellent reproducibility, stability and sensitivity for the detection of tri-n-propylamine (TPA). The linear range was from 1 × 10 −10 to 1 × 10 −6 M ( R 2 = 0.9954) with the detection limit of 5 × 10 −11 M.