A microfluidic platform integrating paper adsorption-based sample clean-up and voltage-assisted liquid desorption electrospray ionization mass spectrometry for biological sample analysis

Dual-signal fluorescence aptasensing system for adenosine triphosphate assisting by MoS2 nanosheets

Adenosine triphosphate (ATP) has an irreplaceable role in the maintenance of many physiological processes and biological functions, and can be employed as an indicator of many diseases. In this work, we constructed a simple and sensitive dual-signal fluorescence aptasensing system for ATP detection with berberine as the signal reporter, ATP-aptamer as the recognition unit and MoS2 nanosheets as the signal amplification. In the absence of ATP, berberine can bind to the single-stranded DNA (ssDNA) of ATP-aptamer and selectively assemble on the surface of MoS2 nanosheets, leading to the fluorescence quenching of bererbine based on the fluorescence resonance energy transfer, denoted by "OFF". Accordingly, the fluorescence anisotropy signal is enhanced due to restriction on rotate of the fluorescent probe and denoted as "ON". Conversely, in the presence of ATP, it specifically interacts with ATP-aptamer and switches the free-curled single-stranded of ATP-aptamer to the G-quadruplex structure of ATP-aptamer/ATP/berberine, causing the detachment from the surface of the MoS2 nanosheet. Accordingly, the fluorescence signal was reversed from "OFF" to "ON", and the fluorescence anisotropy signal was turned "ON" to "OFF". The developed aptasensing system achieved a desirable sensitivity of 40.0 nM with fluorescent mode, and of 20.8 nM with fluorescent anisotropic mode. The sensing system has demonstrated high quality detection performance in human serum sample, and obtained the satisfactory recovery results for fluorescent of 93.0-108.5%, fluorescent anisotropic of 96.4-106.7%.

Rapid identification of Takifugu genus using visual loop-mediated isothermal amplification

Some Takifugu species are commonly found in the coastal areas of China, Japan, Thailand, and Korea and cause pufferfish poisoning, which is toxic and even lethal to humans. From 2010 to 2015, there were 430 cases of pufferfish poisoning worldwide, resulting in 52 deaths. Identification of Takifugu species is imperative to reduce financial losses and ensure food safety. Here, visual loop-mediated isothermal amplification (LAMP) was applied to identify Takifugu species. Conserved regions within the mitochondrial DNA among different Takifugu species were selected to design LAMP primers. In 55 min of amplification, sufficient DNA was obtained to observe the results with the naked eye, without the need for complicated instruments. The method was highly specific, with no cross-detection of 17 other fish species, namely, 7 Tetraodontiformes species and 10 commercially important fish. The method showed a detection limit of 0.1 ng Takifugu DNA and was successfully validated to detect Takifugu in cooked fish and the vomitus of poisoned patients. This rapid and visual LAMP method is a useful tool to prevent false labeling, protect consumer rights, and reduce the risk of pufferfish poisoning. PRACTICAL APPLICATION: The loop-mediated isothermal amplification method established in this study can identify cooked or digested fish products containing 1% or more of Takifugu. Therefore, it can be used for the visual detection of Takifugu products and the medical diagnosis of Takifugu poisoning.

Microfluidic colorimetric detection platform with sliding hybrid PMMA/paper microchip for human urine and blood sample analysis

A microfluidic colorimetric detection (MCD) platform consisting of a sliding hybrid PMMA/paper microchip and a smart analysis system is proposed for the convenient, low-cost and rapid analysis of human urine and whole blood samples. The sliding PMMA/paper microchip comprises a PMMA microfluidic chip for sample injection and transportation, a paper strip for sample filtration (urine) or separation (blood), and a sealed paper-chip detection zone for sample reaction and detection. In the proposed device, the paper-chip is coated with bicinchoninic acid (BCA) and biuret reagent and is then assembled into the PMMA microchip and packaged in aluminum housing. In the detection process, the PMMA/paper microchip is slid partially out of the housing, and 2 μL of sample (urine or whole blood) is dripped onto the sample injection zone. The chip is then slid back into the housing and the sample is filtered/separated by the paper strip and transferred under the effects of capillary action to the sealed paper-chip detection zone. The housing is inserted into the color analysis system and heated at 45 °C for 5 min to produce a purple-colored reaction complex. The complex is imaged using a CCD camera and the RGB color intensity of the image is then analyzed using a smartphone to determine the total protein (TP) concentration of the sample. The effectiveness of the proposed method is demonstrated using TP control samples with known concentrations in the range of 0.03-5.0 g/dL. The detection results obtained for 50 human urine samples obtained from random volunteers are shown to be consistent with those obtained from a conventional hospital analysis system (R² = 0.992). Moreover, the detection results obtained for the albumin (ALB) and creatine (CRE) concentrations of 50 whole blood samples are also shown to be in good agreement with the results obtained from the hospital analysis system (R² = 0.982 and 0.988, respectively).

Application of magnetic fields to wastewater treatment and its mechanisms: A review

Magnetic field (MF) has been applied widely and successfully as an efficient, low-cost and easy-to-use technique to enhance wastewater treatment (WWT) performance. Although the effects of MF on WWT were revealed and summarized by some works, they are still mysterious and complex. This review summarizes the application of MF in magnetic adsorption-separation of heavy metals and dyes, treatment of domestic wastewater and photo-magnetic coupling technology. Furthermore, the mechanisms of MF-enhanced WWT are critically elaborated from the perspective of magnetic physicochemical and biological effects, such as magnetoresistance, Lorentz force, and intracellular radical pair mechanism. At last, the challenges and opportunities for MF application in WWT are discussed. For overcoming the limitations and taking advantages of MFs in WWT, fundamental research of the mechanisms of the application of MFs should be carried out in the future.