Preparation of CoFe@C composite modified electrode for neohesperidin dihydrochalcone sensing and its application in Chinese medicine.

CoFe@C was first prepared by calcining the precursor of CoFe-metal-organic framework-74 (CoFe-MOF-74), then an electrochemical sensor for the determination of neohesperidin dihydrochalcone (NHDC) was constructed, which was stemmed from the novel CoFe@C/Nafion composite film modified glassy carbon electrode (GCE). The CoFe@C/Nafion composite was verified by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Electrochemical impedance spectroscopy (EIS) was used to evaluate its electrical properties as a modified material for an electrochemical sensor. Compared with CoFe-MOF-74 precursor modified electrode, CoFe@C/Nafion electrode exhibited a great synergic catalytic effect and extremely increased the oxidation peak signal of NHDC. The effects of various experimental conditions on the oxidation of NHDC were investigated and the calibration plot was tested. The results bespoken that CoFe@C/Nafion GCE has good reproducibility and anti-interference under the optimal experimental conditions. In addition, the differential pulse current response of NHDC was linear with its concentration within the range 0.08 ~ 20 µmol/L, and the linear regression coefficient was 0.9957. The detection limit was as low as 14.2 nmol/L (S/N = 3). In order to further verify the feasibility of the method, it was successfully used to determine the content of NHDC in Chinese medicine, with a satisfactory result, good in accordance with that of high performance liquid chromatography (HPLC).

Magnetic Nanobeads and De Novo Growth of Electroactive Polymers for Ultrasensitive microRNA Detection at the Cellular Level.

Detection of biomarkers at the cellular level can provide more accurate and comprehensive information that is important for early diagnosis of diseases and evaluation of new drugs. However, the interference of a large number of components in cells and the requirement of high sensitivity bring great challenges for their detection. Herein, a robust and enzyme-free electrochemical platform was proposed for microRNA-21 (miRNA-21) detection by integrating the efficient separation of magnetic nanobeads (MBs) with the multisignal amplification of strand displacement amplification (SDA) and electrochemically mediated atom transfer radical polymerization (eATRP). The eATRP is capable of de novo growth of a number of electroactive polymers on the electrode surface for signal amplification. Compared to simple hybridization, SDA and eATRP can enhance the signals by ∼35-fold, achieving high signal-to-noise ratio for low-abundant target detection. Owing to their superparamagnetism and strong magnetic response ability, MBs endow the method with excellent specificity and anti-interference ability to detect miRNA-21 in cells. Using MBs as capture carriers, SDA and eATRP for signal amplification, and gold nanoflower (AuNF)-modified electrodes as working electrodes, as low as 0.32 aM miRNA-21 was detected. Furthermore, the successful detection of miRNA-21 in cells indicated the great prospect of this method in the early diagnosis of cancers, life science research, and single-entity electrochemical detection.

Simple MoS2-Nanofiber Paper-Based Fluorescence Immunosensor for Point-of-Care Detection of Programmed Cell Death Protein 1.

Programmed cell death protein 1 (PD-1) is one of the coinhibitory checkpoints upon T cell activation, the abnormal expression of which severely threatens host immune modulatation for chronic infection. Thus, fast and sensitive monitoring of PD-1 is of vital importance for early diagnosis and cancer treatment. The current detection methods largely based on enzyme-linked immunosorbent assay (ELISA) require time-consuming incubation and complicated washing steps. Herein, we designed a simple and portable nanofiber paper (NFP)-based fluorescence "off-on" immunosensor for PD-1 rapid determination. Molybdenum disulfide (MoS2) nanosheets modified NFP (MoS2-NFP) was employed for adsorbing and immobilizing CdSe/ZnS quantum dots-antibody (QDs-Ab) complex to construct a ready-to-use fluorescent immunosensor. The fluorescent signal of QDs-Ab was initially quenched by MoS2 under the Förster resonance energy transfer (FRET) effect. When the PD-1 target was specifically captured onto NFP by immunization, the QDs-Ab-PD-1 complex was promptly desorbed from the MoS2-NFP surface, resulting in FRET impediment and fluorescence recovery. As an alternative quenching agent, graphene oxide (GO) served as a contrast to investigate NFP-based sensing performance. Owing to superior quenching and desorption efficiency, the MoS2-NFP-based fluorescence immunosensor exhibited nearly 2-fold lower detection limit (85.5 pg/mL) than GO-NFP-based sensor (151 pg/mL) for PD-1 monitoring. Excellent selectivity and satisfactory recovery in PD-1 mouse cell culture supernatant samples were confirmed as well. In addition, the comparable detectability of the MoS2-NFP-based immunosensor was accurately evaluated by a standard PD-1 mouse ELISA kit. This study displayed a simple, rapid, low-cost, and portable point-of-care PD-1 assay, indicating its broad application prospect toward clinical diagnoses.

Efficient degradation of ivermectin by newly isolated Aeromonas taiwanensis ZJB-18,044.

Ivermectin (IVM) is a widely used antiparasitic agent and acaricide. Despite its high efficiency against nematodes and arthropods, IVM may pose a threat to the environment due to its ecotoxcity. In this study, degradation of IVM by a newly isolated bacterium Aeromonas taiwanensis ZJB-18,044 was investigated. Strain ZJB-18,044 can completely degrade 50 mg/L IVM in 5 d with a biodegradation ability of 0.42 mg/L/h. Meanwhile, it exhibited high tolerance (50 mg/L) to doramectin, emamectin, rifampicin, and spiramycin. It can also efficiently degrade doramectin, emamectin, and spiramycin. The IVM degradation of strain ZJB-18,044 can be inhibited by erythromycin, azithromycin, spiramycin or rifampicin. However, supplement of carbonyl cyanide m-chlorophenylhydrazone, an uncoupler of oxidative phosphorylation, can partially recover the IVM degradation. Moreover, strain ZJB-18,044 cells can pump out excess IVM to maintain a low intracellular IVM concentration. Therefore, the IVM tolerance of strain ZJB-18,044 may be due to the regulation of the intracellular IVM concentration by the activated macrolide efflux pump(s). With the high IVM degradation efficiency, A. taiwanensis ZJB-18,044 may serve as a bioremediation agent for IVM and other macrolides in the environment.

Enhancement of gibberellic acid production from Fusarium fujikuroi by mutation breeding and glycerol addition.

Gibberellic acid (GA3) is a natural plant growth hormone that has been widely used in agriculture and horticulture. To obtain higher GA3 producing strains, the method of screening the strains for resistance to simvastatin was used after treatment with nitrosoguanidine (NTG) and gamma rays. The rationale for the strategy was that mutants showing simvastatin resistance were likely to be high GA3 producers, as their activity of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is relatively more effective. GA3 yield of mutant S109 increased by 14.2% than that of the original strain. The GA3 production ability in mutant S109 remained relatively stable after ten generations. With the addition of 0.4 g glycerol on the 5th day during the fermentation process in Erlenmeyer flask, maximum GA3 production of 2.7 g/L was achieved by this mutant, exhibiting 28.6% increase compared with original strain. Furthermore, we also achieved 2.8 g/L GA3 and had a 33.3% increase with addition 20 g glycerol on the 5th day during the fermentation process in a 5-L bioreactor. Our results indicated efficient GA3 production could be achieved on the condition that the supply of glycerol at the suitable conditions. This study would lay a foundation for industrial production of GA3.

Fluorescent-Magnetic-Catalytic Nanospheres for Dual-Modality Detection of H9N2 Avian Influenza Virus.

The outbreak of H9N2 avian influenza virus (H9N2 AIV) brings high mortality and huge economic losses every year. Sensitive and reliable detection methods are essential to timely diagnosis and treatment. Herein, a dual-modality immunoassay is proposed for H9N2 AIV detection by employing fluorescent-magnetic-catalytic nanospheres (FMCNs) as labels and alkaline phosphatase (ALP)-induced metallization as a signal amplification strategy. The excellent magnetic properties of FMCNs endow the assay a potential application in complex samples. Also, the excellent fluorescence properties of FMCNs enable fluorescence modality readout. The antibodies on the FMCN surface can achieve efficient capture and separation of targets. Amplified electrochemical modality readout can be obtained through ALP-catalyzed silver deposition. Dual-modality immunoassay combined the advantages of electrochemical assay with fluorescence assay and provides accurate detection results to meet different testing needs. With two quantitative analysis forms, H9N2 AIV can be detected by electrochemical signals with a quantitation range of 0.1 to 1000 ng/mL and a detection limit of 10 pg/mL. The linear range is 300 to 1000 ng/mL with a detection limit of 69.8 ng/mL by the fluorescence signal readout. Moreover, the specificity, anti-interference ability, accuracy, and diversity of the proposal have unlimited potential for early diagnosis of suspect infections.

An exonuclease-assisted triple-amplified electrochemical aptasensor for mucin 1 detection based on strand displacement reaction and enzyme catalytic strategy.

The development of some sensitive methods for MUC1 is critical for preclinical diagnosis of tumors. In this experiment, we built a triple-amplified electrochemical aptasensor to achieve sensitive detection of MUC1, which was based on exonuclease III (Exo III)-assisted with strand displacement reaction and enzyme catalytic strategy. Firstly, with the help of Exo III, MUC1 and aptamer could be recycled during the cycle I, the single stranded DNA-1 (S-1) was produced during the process and was introduced to the hybride reaction on the electrode. Secondly, during the cycle II, strand displacement reaction was triggered on the electrode with the adding of hairpin DNA-2 (H-2). Thirdly, after the gold nanoparticles (AuNPs)-DNA-enzyme conjugates hybrided with the H-2 on the electrode, the AuNPs-DNA-enzyme conjugates could act as signal probe to produce electrochemical catalytic signal. We used the fabricated triple-amplified electrochemical aptasensor that could detect MUC1 from 0.1 pg mL-1 to 10 ng mL-1 with the detection limit of 0.04 pg mL-1 under the optimized experimental conditions. The constructed triple-amplified electrochemical aptasensor could be applied in real samples determination. Besides, the strategy can be applied to detect other proteins for health monitoring.

Silver nanoclusters-assisted triple-amplified biosensor for ultrasensitive methyltransferase activity detection based on AuNPs/ERGO hybrids and hybridization chain reaction.

In the paper, a triple-amplified biosensor was built for the purpose of ultrasensitive methyltransferase (Dam MTase) activity detection and inhibitor screening based on in-situ synthesized silver nanoclusters (AgNCs) as signal probes to provide amplified current signal coupling with gold nanoparticles/electrochemical reduced graphene oxide (AuNPs/ERGO) hybrids and hybridization chain reactions (HCR) amplification strategy. For biosensor preparation, the AuNPs/ERGO hybrids were firstly generated on the electrode surface by electrochemical co-reduction method, then the ds-DNA structures which comprised the specific recognition sequences (5'-G-A-T-C-3') of the Dam MTase and the restrictive endonuclease DpnI were formed on the electrode by the hybridization of the assistant DNA with the capture DNA. The presence of Dam MTase methylated partial ds-DNA structures on the electrode which could be digested by DpnI and could not undergo HCR process. The unmethylated ds-DNA structures underwent HCR process to further hybridize with DNA1 and DNA2 to form ds-DNA superstructures as effective template for AgNCs in-situ synthesis. Oxidation peak current of silver was obtained as signal output for Dam MTase detection. Integrated synthesis and detection in one as well as combined metal nanocluster with DNA superstructures, this biosensor showed a good performance for Dam MTase activity detection with a detection limit of 0.0073 U/mL. Compared with reported biosensor, the designed biosensor showed high sensitivity and had potential in clinical diagnosis as well as inhibitor screening.