Anti-aggregation colorimetric sensing of cysteine using silver nanoparticles in the presence of Pb2.

Using silver nitrate as the silver source and sodium borohydride as the reducing agent, we synthesized negatively charged silver nanoparticles (AgNPs). Subsequently, the AgNPs solution was mixed with positively charged lead ions, resulting in AgNPs aggregation via electrostatic interactions. This led to a color change in the solution from yellow to purple and eventually to blue-green. Our study focused on a colorimetric method that exhibited high selectivity and sensitivity in detecting cysteine using AgNPs-Pb2+ as a sensing probe. Upon the introduction of cysteine to the AgNPs-Pb2+ system, the absorbance of AgNPs increased at 396 nm and decreased at 520 nm. The formation of a complex between cysteine and lead ions prevented the aggregation of silver nanoparticles, enabling the colorimetric detection of cysteine. The relationship between the concentration of ΔA396/A520 and cysteine showed linearity within the range of 0.01 to 0.1 µM; the regression equation of the calibration curve is ΔA396/A520 = 9.0005c - 0.0557 (c: µM), with an R2 value of 0.9997. The detection limit was found to be 3.8 nM (S/N = 3). This method demonstrated exceptional selectivity and sensitivity for cysteine and was effectively used for the determination of cysteine in urine. Our findings offer a new perspective for the future advancement of anti-aggregation silver nanocolorimetry.

Constructed a self-powered sensing platform based on nitrogen-doped hollow carbon nanospheres for ultra-sensitive detection and real-time tracking of double markers.

Acute myocardial infarction (AMI) is acute necrosis of a portion of the myocardium caused by myocardial ischemia, which seriously threatens people's health and life safety. Its early diagnosis is a difficult problem in clinical medicine. Research has found that the abnormal expression of microRNA-199a (miR-199a) and microRNA-499 (miR-499) was closely related to AMI disease. In this work, we took advantage of the structural advantages of nitrogen-doped hollow carbon nanospheres (N-HCNSs) to design an ultra-sensitive, portable real-time monitoring visual self-powered biosensor system, which based on dual-target miRNAs triggered catalytic hairpin assembly (CHA) for sensitive detection of miR-199a and miR-499. In addition, the capacitor and the smartphone are introduced into the system to realize the secondary improvement of system sensitivity and portable real-time visual monitoring. Under optimized conditions, in the linear range of 0.1-100000 aM, the detection limits of miR-199a and miR-499 are 0.031 and 0.027 aM, respectively. At the same time, the ultra-sensitive detection of miRNAs is realized in the serum sample, and the recovery rate of miR-199a and miR-499 are 98.0-106.0% (RSD: 0.6-8.1%) and 94.0-109.7% (RSD: 1.8-7.7%), respectively. The method is simple, sensitive and can be used for real-time tracking and portable monitoring of related diseases.

The self-powered electrochemical biosensing platform with multi-amplification strategy for ultrasensitive detection of microRNA-155.

A self-powered biosensor (SPB) was constructed for the ultra-sensitive detection of microRNA-155 (miR-155) by combining a capacitor/enzymatic biofuel cell (EBFC), a strategy of rolling circle amplification (RCA) and a digital multimeter (DMM). The experimental results show that the sensitivity of the assembled EBFC-SPB can reach 15.85 µA/pM with the action of matching capacitor, which is 513% of that without capacitor (3.09 µA/pM). This achieves the first signal amplification. Furthermore, when the target miR-155 triggers RCA, electrons are continuous generated and flow to the biocathode through the external circuit to catalyze the reduction of oxygen and release [Ru(NH3)6]3+ electron acceptor. This achieves the second signal amplification. Finally, DMM is used to convert the signal into instantaneous current and amplify it for real-time reading. This achieves the third signal amplification. Therefore, the limit of detection (LOD) of the developed biosensor is as low as 0.17 fM (S/N = 3), and the linear range is between 0.5 fM and 10,000 fM, indicating that the EBFC-SPB has a broad application prospect for cancer marker of miR-155 with ultrasensitive detection.

Recent advances in biological detection with rolling circle amplification: design strategy, biosensing mechanism, and practical applications.

Rolling circle amplification (RCA) is a simple and isothermal DNA amplification technique that is used to generate thousands of repeating DNA sequences using circular templates under the catalysis of DNA polymerase. Compared to alternating temperature nucleic acid amplification such as polymerase chain reaction (PCR) amplification, RCA is more suitable for on-spot detection without the need for an expensive thermal cycler. In this study, the principle and classification of RCA are introduced, and the applications of RCA in the detection of pathogenic bacteria, nucleic acid tumor markers, viruses, and proteins are reviewed. Finally, the perspectives of RCA in biological detection are anticipated. The RCA method has a great potential for biological detection. This review aims to provide references for the further development and application of the RCA technique in biosensors.

Cycling profile of layered MgAl2O4/reduced graphene oxide composite for asymmetrical supercapacitor.

To improve the ineluctable agglomeration and weak inherent conductivity of MgAl2O4 electrode materials, MgAl2O4/rGO composite is synthesized by a facile method and it shows large specific surface area and enhanced conductivity. Its particular framework can availably hold back the aggregation of MgAl2O4 and restacking of rGO, and accelerate reversible redox reactions. The MgAl2O4/rGO composite shows a specific capacity of 536.6 F/g at 1 A/g (257.3 F/g at 40 A/g) and retains 96.9% after 10,000 cycles at 5 A/g. An asymmetric supercapacitor is developed with MgAl2O4/rGO composite and activated carbon. An energy density of 16.2 Wh/kg is obtained at a power density of 400 kW/kg. Additionally, this device has successfully lighted up a LED, demonstrating its promising application in energy storage.

NiCo2 S4 Materials for Supercapacitor Applications.

Cobalt-nickel sulfide (NiCo2 S4 ) shows extensive potential for innovative photoelectronic and energetic materials owing to distinctive physical and chemical properties. In this review, representative strategies for the fabrication and application of NiCo2 S4 and composite nanostructures are outlined for supercapacitors, with the aim of promoting the development of NiCo2 S4 and their composites in the supercapacitor field through an analysis and comparison of diverse nanostructures. A brief introduction into the structures, properties, and morphologies are presented. Further prospects and promising developments of the materials in the supercapacitor field are also proposed.

[The change and mechanism of apoptosis in the hippocampal CA1 region of rats exposed to intermittent hypoxia].

OBJECTIVE: To investigate the effect of intermittent hypoxia on rat hippocampal oxidative stress and neuron apoptosis in the hippocampal CA1 region. METHODS: Thirty six healthy male Wistar rats were randomly divided into three groups of 12 each: a control (NC) group, an intermittent hypoxia (IH) group and a sustained hypoxia (SH) group. The levels of Malondialdehyde (MDA) and Superoxide dismutase (SOD) were detected by colorimetric method. Western blotting was used to examine the expression of p-JNK and p-c-jun. TUNEL was used to detect the neuron apoptosis in the hippocampal CA1 region. RESULTS: The level of MDA (nmol/mg protein) in the hippocampal CA1 region in IH group (1.61 +/- 0.39) was significantly higher than those in NC group (1.25 +/- 0.29) and in SH group (1.34 +/- 0.24), F = 4.185, P < 0.05; the level of SOD (NU/mg protein) in IH group (45 +/- 13) was significantly lower than those in NC group (58 +/- 12) and in SH group (56 +/- 10), F = 4.338, P < 0.05. There were no significant differences between SH and NC groups in the level of MDA or in the activity of SOD (P all > 0.05). The expression of p-JNK and p-c-jun in IH group were 2.1 and 2.3 times the expression in the NC group respectively. The apoptotic indices of IH group (0.30 +/- 0.16) was significantly elevated as compared with group NC (0.12 +/- 0.07) and SH (0.17 +/- 0.09), F = 7.766, P < 0.01. CONCLUSION: Oxidative stress associated with IH in the hippocampal CA1 region can activate JNK signaling pathway, leading to the apoptosis of hippocampal neuron. This maybe the pathophysiological basis of obstructive sleep apnea hypopnea syndrome with neurobehavioral impairments.