A renewable screen-printed electrode based on magnetic NiCo@N-doped carbon nanotubes derived from Co-MOF for ractopamine detection.

A renewable electrochemical screen-printed electrode (SPE) is proposed based on magnetic bamboo-like nitrogen-carbon (N-C) nanotubes loaded with nickel-cobalt alloy (NiCo) nanoparticles (NiCo@N-CNTs) for the determination of ractopamine (RAC). During the preparation of NiCo@N-CNTs, Co-MOF-67 (ZIF-67) was firstly synthesized, and then blended with dicyandiamide and nickel acetate, followed by a one-step pyrolysis procedure to prepare NiCo@N-doped carbon nanotubes. The surface morphology, structure, and chemical composition of NiCo@N-CNTs were characterized by SEM, TEM, XRD, XPS, and EDS. The electrocatalytic and electrochemical behavior of NiCo@N-CNTs were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that NiCo@N-CNTs possessed remarkable conductivity and electrocatalysis to the oxidation of ractopamine (RAC). By using screen-printed electrode (SPE), NiCo@N-CNTs, and a designed base support, a magnetic RAC sensor (NiCo@N-CNTs/SPE) was successfully constructed. It presented a detection linear range of 0.05-80 µM with a detection limit of 12 nM (S/N = 3). It also exhibited good sensitivity, reproducibility, and practicability in spiked real pork samples. Since the adhesion of NiCo/N-CNTs on SPE was controlled by magnet, the NiCo@N-CNTs was easily detached from the SPE surface by magnetism and thus displayed excellent renewability. This work broadened insights into portable devices for on-site and real-time analysis.

A dual-mode strategy based on ß-galactosidase and target-induced DNA polymerase protection for transcription factor detection using colorimetry and a glucose meter.

In this work, we report a novel dual-mode method for the highly specific and sensitive detection of transcription factors (TFs) via the integration of Klenow polymerase protection induced by target-specific recognition, cascade-signal amplification using the hybridization chain reaction (HCR) and CRISPR/Cas12a system, and dual-signal transduction mediated by ß-galactosidase (ß-gal) and two substrates. A dual-mode signal-sensing interface was constructed by immobilizing the oligo DNA probe (P1) tethered ß-gal in a 96-well plate. A hairpin H1 with the ability to initiate HCRs was designed to contain the TF binding site. The binding between the TF and H1 protected the H1 from being extended by the Klenow fragment. After thermal denaturation, the reserved H1 launched the HCR and the HCR products activated CRISPR/Cas12a to cleave P1 and reduce the ß-gal on the sensing interface, and thus the contents of the TFs and the corresponding signals mediated by the catalysis of ß-gal showed a correlation. This work was the first attempt at utilizing ß-gal for dual-signal transduction. It is a pioneering study to utilize the HCR-CRISPR/Cas12a system for dual-mode TF sensors. It revealed that DNA polymerase protection through the binding of TF and DNA could be applied as a new pattern to develop TF sensors.

Enhancement and inactivation effect of CRISPR/Cas12a via extending hairpin activators for detection of transcription factors.

An enhancement effect for the activation of CRISPR/Cas12a (CRISPR = clustered regularly interspaced short palindromic repeats; Cas = CRISPR-associated) was discovered. That was, a hairpin model with dangling 5' end complementary to crRNA (CRISPR RNA) greatly improved the activity of CRISPR/Cas12a after extention of two random sequences. But, the corresponding intact hairpin without PAM (protospacer adjacent motif) or suboptimal PAM sequences was completely inactive to CRISPR/Cas12a because of the superhigh stability of intact hairpin. According to the finding, a CRISPR/Cas12a-based strategy coupled with a signal reported system was designed for transcription factors detection. By using mono-labeled ssDNA (single-stranded DNA) as reporter and two newly synthesized N-C (nitrogen-doped carbon) nanosheets as scavenger to eliminate the fluorescent background, the strategy realized the detection of NF-ĸB p50 (p50 subunit of nuclear factor kappa-B) with a linear detection range of 0.8 - 2000.0 pM and a LOD of 0.5 pM. The discovery of "enhancement and inactivation effect" not only deepened insight into CRISPR/Cas12a but also broadened the practical application of CRISPR/Cas systems for the molecular detection and disease diagnostics.

Dual-mode photoelectrochemical/electrochemical sensor based on Z-scheme AgBr/AgI-Ag-CNTs and aptamer structure switch for the determination of kanamycin.

A "signal-on" dual-mode aptasensor based on photoelectrochemical (PEC) and electrochemical (EC) signals was established for kanamycin (Kana) assay by using a novel Z-scheme AgBr/AgI-Ag-CNTs composite as sensing platform, an aptamer structure switch, and K3[Fe(CN)6] as photoelectron acceptor and electrochemical signal indicator. The aptamer structure switch was designed to obtain a "signal-off" state, which included an extended Kana aptamer (APT), one immobilized probe (P1), and one blocking probe (P2) covalently linked with graphdiyne oxide (GDYO) nanosheets. P1, P2, and aptamer formed the double helix structure, which resulted in the inhibited photocurrent intensity because of the weak conductivity of double helix layer and serious electrostatic repulsion of GDYO towards K3[Fe(CN)6]. In the presence of Kana, APT specifically bound to the target and dissociated from P1 and P2, and thus, a "signal-on" state was initiated by releasing P2-GDYO from the platform. Based on the sensing platform and the aptamer structure switch, the dual-mode aptasensor realized the linear determination ranges of 1.0 pM-2.0 µM with a detection limit (LOD) of 0.4 pM (for PEC method) and 10 pM-5.0 µM with a LOD of 5 pM (for EC method). The aptasensor displayed good application potential for Kana test in real samples.

De Novo Development of a Universal Biosensing Platform by Rapid Direct Native Protein Modification.

An innovative biosensing assay was developed for simplified, cost-effective, and sensitive detection. By rapid, direct treatment of target proteins with iron porphyrin (TPPFe) in situ, a carboxyl group of amino acid conjugates with an Fe atom of the TPPFe molecule, forming a stable protein complex. We have shown that this complex not only maintains the integrity and functions of original proteins but also acquires peroxidase activity that can turn TMB to a comparably visible signal like that in ELISA. This study is unique since such conversion is difficult to achieve with standard chemical modification or molecular biology methods. In addition, the proposed immunoassay is superior to traditional ELISA as it eliminates an expensive and complicated cross-linking process of an enzyme-labeled antibody. From a practical point of view, we extended this assay to rapid detection of clinically relevant proteins and glucose in blood samples. The results show that this simple immunoassay provides clinical diagnosis, food safety, and environmental monitoring in an easy-to-implement manner.

Visual Quantitative Detection of Glutathione and Cholesterol in Human Blood Based on the Thiol-Ene Click Reaction-Triggered Wettability Change of the Interface.

Herein, we proposed an innovative visual quantitative sensing strategy based on thiol-ene click chemistry and the capillary action principle. A triethoxyvinylsilane (VTEO)- or mercaptopropylsilatrane (MPS)-modified interface was prepared for analyte recognition. Target analyte molecules containing thiol groups or C═C double bonds are coupled to the VTEO- or MPS-modified inner surface of the glass capillary tube via a thiol-ene click reaction, respectively. Then, the molecular recognition events were transformed into the wettability change of the inner wall of the glass capillary. The concentration of the target molecules was quantified by reading the height change of the water column in the capillary tube. As a proof of concept, this strategy was successfully used to build visual quantitative sensors for detecting glutathione and cholesterol. In addition, this strategy showed a good anti-interference ability to complex biological fluids and realized sensitive glutathione (GSH) and cholesterol detection in real human blood samples.

Tunable graphdiyne for DNA surface adsorption: affinities, displacement, and applications for fluorescence sensing.

Graphdiyne (GDY) adsorbed DNA probes have been used as a fluorescent sensing platform, but topics including DNA adsorption affinities, DNA probe displacement, and fluorescence quenching ability were rarely researched. Herein, the adsorption affinity of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) on a tremella-like GDY was tuned by modulating the surface chemistry of GDY. The fluorescence quenching ability of GDY with different oxidation degrees was compared. The nonspecific displacement of DNA probes on GDY was studied. Under the same concentrations, GDY with low oxidation degree exhibited stronger adsorption affinity and higher adsorption capacity to both ssDNA and dsDNA than highly oxidized GDY. DNA adsorbed on low-oxidized GDY was more resistant to displacement by other DNAs. Protein showed strong interaction with different GDY and could displace DNA probes on GDY. Based on these findings, an ideal GDY with proper oxidation degree, exhibiting high surface affinity for ssDNA and low affinity for dsDNA, was used as scavenger of redundant ssDNA fluorescent probe in an enzyme-assisted amplification system for sensitive ochratoxin (OTA) detection. This study has enhanced our fundamental understanding of DNA adsorption by GDY. It also provided a rational way to apply GDY for fluorescence sensing in a complicated system.

Single Primer Based Multisite Strand Displacement Reaction Amplification Strategy for Rapid Detection of Terminal Deoxynucleotidyl Transferase Activity.

A fluorescence-based multisite strand displacement reaction (MSSDR) amplification strategy is developed for the rapid, sensitive, and selective detection the activity of terminal deoxynucleotidyl transferase (TdT). Oligo dT primer was used for the TdT extension reaction, then the left oligo dT primers were hybridized to the TdT extension reaction product by end to end tiled style and initiated the MSSDR by Klenow polymerase, subsequently, 3' terminals of these single-strand DNA produced by MSSDR are folded back to complement themselves with the adjacent sequences, and Klenow polymerase makes it into double-stranded DNA (dsDNA). The final dsDNA products were analyzed via dsDNA specific fluorescent dye. This method enables rapid (less than 100 min) and sensitive (limit of detection, LOD, 1.35 × 10-5 U) detection and has been demonstrated to work well using a real biosample. Our design would not only serve as a new prototype for high-throughput automated analysis and clinic diagnostic application but also has promising potential for improving the sensitivity of those TDT related biosensing system.

Aptamer based ratiometric electrochemical sensing of 17ß-estradiol using an electrode modified with gold nanoparticles, thionine, and multiwalled carbon nanotubes.

Gold nanoparticles (AuNPs) with a size of ~3 nm were placed on a thionine-multiwalled carbon nanotube (Thi-CNTs) conjugate to form a novel AuNP-Thi-CNTs nanocomposite. Its morphology and composition were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The nanocomposite was placed on an electrode and used as a redox-active signaling interface to fabricate a ratiometric electrochemical aptasensor for 17ß-estradiol (E2). The potentiostatic insertion method was applied to insert an aptamer against E2 into a thin alkane monolayer to warrant an adequate distance between aptamers. The aptamer against E2 acts as both a collector and separator to specifically bind E2. The electrode displays two peak signals (at +0.50 V vs. SCE for E2; and at -0.32 V for Thi) which increase and decrease, respectively, in the 12 pM to 60 nM E2 concentration range. Therefore, the current ratio can be used to reliably, reproducibly, and sensitively quantify the concentration of E2. Graphical abstract Schematic presentation of a novel AuNP-Thi-CNTs nanocomposite. AuNP-Thi-CNTs showed good electrocatalytic oxidation to E2. AuNP-Thi-CNTs was used as self-redox signal interface to fabricate aptasensor. Dual signals of extrinsic E2 and inner Thi was applied to monitor the concentration of E2.

Prompting peroxidase-like activity of gold nanorod composites by localized surface plasmon resonance for fast colorimetric detection of prostate specific antigen.

The interaction between incident light and surface electrons in conductive nanoparticles produces localized plasmon oscillations with a resonant frequency that strongly depends on the composition, size, geometry, and dielectric environment. Hybrid heterostructure materials combining two or more materials in one structure represent a powerful way to achieve unique properties and multifunctionality compared to those of the individual nanoparticle components. Hybrid gold nanorods and gold nanoclusters (GNR/AuNCs) heterostructures prepared by intimate integration of GNRs with AuNCs exhibit both localized surface plasmon resonance (LSPR) property and peroxidase-like activity. It is found that the catalytic activity of the AuNC/GNR heterostructure could be remarkably enhanced by LSPR induced by photon-plasmon coupling in the visible to near-infrared (NIR) region. Meanwhile, the catalytic activity of enzyme-like AuNC/GNRs may be regulated by immunoreactions to realize specific recognition of a target analyte. Accordingly, a fast colorimetric assay within 5 min for the detection of prostate specific antigen (PSA) was developed based on a AuNC/GNRs heterostructure mask regulated by the target molecule under photon-plasmon coupling. The color intensity is inversely proportional to the PSA concentration, and quantitative analysis may be achieved in a range of 10 and 200 pg mL-1. This sensor was practically applied to detect PSA levels in prostate cancer serum samples and the determined values agreed well with those measured by the hospital using standard methods. This indicates that the AuNC/GNRs heterostructure-based assay has high accuracy for the analysis of practical samples. Moreover, the new method has the advantages of very fast determination and low sample volume requirements.

Treatment of acute respiratory distress syndrome with allogeneic adipose-derived mesenchymal stem cells: a randomized, placebo-controlled pilot study.

BACKGROUND: Recent studies have demonstrated that mesenchymal stem cells (MSCs) modulate the immune response and reduce lung injury in animal models. Currently, no clinical studies of the effects of MSCs in acute respiratory distress syndrome (ARDS) exist. The objectives of this study were first to examine the possible adverse events after systemic administration of allogeneic adipose-derived MSCs in ARDS patients and second to determine potential efficacy of MSCs on ARDS. METHODS: Twelve adult patients meeting the Berlin definition of acute respiratory distress syndrome with a PaO2/FiO2 ratio of < 200 were randomized to receive allogeneic adipose-derived MSCs or placebo in a 1:1 fashion. Patients received one intravenous dose of 1 × 106 cells/kg of body weight or saline. Possible side effects were monitored after treatment. Acute lung injury biomarkers, including IL-6, IL-8 and surfactant protein D (SP-D), were examined to determine the effects of MSCs on lung injury and inflammation. RESULTS: There were no infusion toxicities or serious adverse events related to MSCs administration and there were no significant differences in the overall number of adverse events between the two groups. Length of hospital stay, ventilator-free days and ICU-free days at day 28 after treatment were similar. There were no changes in biomarkers examined in the placebo group. In the MSCs group, serum SP-D levels at day 5 were significantly lower than those at day 0 (p = 0.027) while the changes in IL-8 levels were not significant. The IL-6 levels at day 5 showed a trend towards lower levels as compared with day 0, but this trend was not statistically significant (p = 0.06). CONCLUSIONS: Administration of allogeneic adipose-derived MSCs appears to be safe and feasible in the treatment of ARDS. However, the clinical effect with the doses of MSCs used is weak, and further optimization of this strategy will probably be required to reach the goal of reduced alveolar epithelial injury in ARDS. TRIAL REGISTRATION: Clinical trials.gov, NCT01902082.

A platinum glutamate acid complex as a peroxidase mimic: high activity, controllable chemical modification, and application in biosensors.

Recent strides in nanotechnology have given rise to nanozymes, nanomaterials designed to emulate enzymatic functions. Despite their promise, challenges such as batch-to-batch variability and limited atomic utilization persist. This study introduces Pt(Glu)2, a platinum glutamic acid complex, as a versatile small-molecule peroxidase mimic. Synthesized through a straightforward method, Pt(Glu)2 exhibits robust catalytic activity and stability. Steady-state kinetics reveal a lower Km value compared to that of natural enzymes, signifying strong substrate affinity. Pt(Glu)2 was explored for controllable chemical modification and integration into cascade reactions with natural enzymes, surpassing other nanomaterials. Its facile synthesis and seamless integration enhance cascade reactions beyond the capabilities of nanozymes. In biosensing applications, Pt(Glu)2 enabled simultaneous detection of cholesterol and alkaline phosphatase in human serum with high selectivity and sensitivity. These findings illustrate the potential of small molecule mimetics in catalysis and biosensing, paving the way for their broader applications.

Economic burden attributable to healthcare-associated infections at western China hospitals: 6 Year, prospective cohort study.

OBJECTIVES: Healthcare-associated infections (HAIs) represent a major threat to patient safety and are associated with significant economic burden. Calculating the costs attributable to HAIs is challenging given the various sources of bias. Although HAIs as a reasonably preventable medical harm should have been closely linked to medical insurance incentives, there was little linkage between HAIs and medicare in western China owing to the lack of economic evaluation data. The present study aimed to generate estimates of the attributable costs associated with HAIs and the magnitude of costs growth. METHODS: In this cohort study designed horizontally and vertically from 2016 to 2022, we compared outcomes of randomly sampling patients with HAIs and individually matched patients without HAIs in two cohorts at a 6-year interval at 34 hospitals in western China. The primary outcome was the direct medical cost for the entire hospital stay, converted to US dollars ($ for the benchmark year), discounted at 3% annually, and estimated separately in the full analysis set (FAS) and the per protocol set (PPS). We used multiple linear regression to adjust the discounted costs and to assess subgroups effects within each cohort. We nested a dynamic vertical comparison of costs attributable to HAIs between the front and rear cohorts. RESULTS: A total of 230 patients with HAIs in 2016 and 204 patients with HAIs in 2022 were enrolled. After a 1:1 match, all 431 pairs were recruited as FAS, of which 332 pairs as PPS met all matching restrictions. Compared to the 2016 cohort in FAS, the patients with HAIs in 2022 had a significantly older age (64.40 ± 16.45 years), higher repeat hospitalization rate (65 [32.02%] of 203), and lower immune function (69 [33.99%] of 203). The discounted costs and adjusted-discounted costs for patients with HAIs in the 2022 cohort were found to be significantly higher than those of patients without HAIs (discounted costs: $5484.60 [IQR 8426.03] vs $2554.04(4530.82), P < 0.001; adjusted-discounted costs: $5235.90 [3772.12] vs $3040.21(1823.36), P < 0.001, respectively), and also higher than those of patients with HAIs in the 2016 cohort (discounted costs: $5484.60 [8426.03] vs $3553.00 [6127.79], P < 0.001; adjusted-discounted costs: $5235.90 [3772.12] vs $3703.82 [3159.14], P < 0.001, respectively). In vertical comparison of PPS, the incremental costs of the 2022 cohort are 1.48 times higher than those of the 2016 cohort ($964.63(4076.15) vs $652.43 [2533.44], P = 0.084). CONCLUSIONS: This meticulously designed study in western China has successfully and accurately examined the economic burden attributable to HAIs. Their rapidly increasing tendency poses a serious challenge to patients, hospitals, and the medical insurance. A closer linkage between HAIs and ongoing motivating system changes is urgently needed in western China.

Multifunctional Gold-Silver-Carbon Quantum Dots Nano-Hybrid Composite: Advancing Antibacterial Wound Healing and Cell Proliferation.

The urgent need for innovative materials that effectively eliminate bacteria while promoting cell growth to accelerate wound healing has led to the exploration of new options, as current antimicrobial nanoparticles often exhibit high cytotoxicity, which hinders wound closure. In this study, a nano-hybrid composite, named gold-silver-carbon quantum dots (AuAg-CDs), was prepared by embedding gold and silver nanoclusters into carbon dots. The AuAg-CDs nano-hybrid composite demonstrates remarkable biocompatibility, displays potent antibacterial activity, and possesses a unique capability to promote cell proliferation. By physically disrupting bacterial membranes and promoting mammalian cell proliferation, this composite emerges as a highly promising material for wound healing applications. The underlying mechanism of the multifunctional AuAg-CDs was investigated through comprehensive analyses encompassing cell morphology, bacterial membrane potential, levels of reactive oxygen species (ROS), and adenosine triphosphate (ATP) production in both bacterial and mammalian cells. Additionally, AuAg-CDs were incorporated into alginate to create a hydrogel wound dressing, which underwent evaluation using animal models. The results underscore the remarkable potential of the AuAg-CDs wound dressing in facilitating the proliferation of wound fibroblasts and combating bacterial infections. The significance of designing multifunctional nanomaterials to address the challenges associated with pathogenic bacterial infections and regenerative medicine is highlighted by this study, paving the way for future advancements in these fields.

The composite of bismuth oxyiodide-bismuth/nitrogen-doped carbon for photoreduction and electrochemical/photoelectrochemical dual-model sensing of Cr(VI).

A porous bismuth oxyiodide-metal bismuth/nitrogen-doped carbon (BiOI-Bi/N-C) composite composed of BiOI nanosheets, N-C sheets, and metallic Bi nanoparticles was prepared. BiOI-Bi/N-C exhibited remarkable cathodic photoelectrochemical activity and rapid adsorption capacity for Cr(VI) ions. Interestingly, the photocatalytic process of BiOI-Bi/N-C toward Cr(VI) was pH dependent. Under acidic medium, the synthesized material displayed efficient photocatalysis and achieved 95.0% photoreduction efficacy for Cr(VI) ions to Cr3+ within 30 min under visible light irradiation. Under neutral medium, Cr(VI) state showed a different photocatalytic process, and Cr(OH)3 as a product covered on BiOI-Bi/N-C, which decreased the electrochemical (EC) and photoelectrochemical (PEC) performance of BiOI-Bi/N-C. Based on the findings, BiOI-Bi/N-C was utilized as EC/PEC dual-model sensing interface for the detection of Cr(VI) ions. The presented dual-model sensing method displayed an ultralow limit of detection down to 6.8 pM for EC and 3.2 pM for PEC. It demonstrated the practical application potential for the assay of Cr(VI) in real samples.

Sensitive fluorescence detection of pathogens based on target nucleic acid sequence-triggered transcription.

Accurate identification of mutant pathogens derived from genetic polymorphisms is highly desired in clinical diagnosis. However, current detection methods based on Watson-Crick hybridization suffers from false positives due to the cross-reactivity of wild-type sequences. In this study, we developed an accurate identification of mutant pathogens by combining programmable DNAzyme and target nucleic acid sequence-triggered transcription. Single nucleotide variants (SNVs) are the most plentiful type of mutations in the genome. High specificity to discriminate SNV was first achieved by rational design of dual-hairpin DNA structure and DNAzyme's capability of site-specific cleavage. T7 RNA polymerase-mediated transcription amplification was introduced to exponentially increase the sensitivity by encompassing T7 promoter sequence into the dual-hairpin DNA structure. The design of this biosensor is fast and straightforward without many computational steps, and the highly sensitive biosensor can detect not only SNVs but also occasional insertions and large deletions in the genome. We showed that the assay could rapidly detect COVID-19 variant and methicillin-resistant Staphylococcus aureus (MRSA), and the limit of detection is 0.96 copy/µL. The modular design of functional DNA enables this biosensor be easily reconfigured and is useful diagnosis of emerging infectious diseases caused by mutant pathogens.

DBB1a, involved in gibberellin homeostasis, functions as a negative regulator of blue light-mediated hypocotyl elongation in Arabidopsis.

Double B-box 1a (DBB1a) belongs to the zinc-finger family proteins in Arabidopsis thaliana. Transcriptional analysis uncovered that the DBB1a gene expression was blue light-dependently regulated, and the transcript level of DBB1a in cry1cry2 was decreased but not in phyAphyB compared to wild type under blue light conditions. Transgenic plants containing pDBB1a:GUS (ß-glucuronidase) displayed GUS activity in the vascular system of leaves and petioles. Green fluorescent protein (GFP)-fused DDB1a (DBB1a-GFP) protein was found in the nucleus in transient transformation assays with onion epidermal cells as well as in stable transgenic Arabidopsis plants. To investigate the function of DBB1a, we generated DBB1a over-expressing and under-expressing transgenic Arabidopsis plants. Analysis of hypocotyl growth of these lines indicated that DBB1a promoted hypocotyl elongation under blue light condition. The phenotype of transgenic plants with DBB1a over-expression could be impaired by a gibberellin (GA)-biosynthesis inhibitor. Moreover, the expression analysis of GA metabolic and catabolic genes in DBB1a transgenic lines indicated that the DBB1a suppressed GA2-oxidase1 (GA2ox1) and GA2-oxidase8 (GA2ox8) expression, but induced GA3ß-hydroxygenase1 (GA3ox1) and GA20-oxidase1 (GA20ox1) expression under blue light. Taken together, we concluded that DBB1a promotes hypocotyl elongation under blue light condition through an increase in bioactive GA levels in Arabidopsis.

A cathode photoelectrochemical assay of terminal deoxynucleotidyl transferase activity based on Ag-AgI-CNTs composite and surface multisite strand displacement amplification.

Photocathode-based assay is anti-interference for real sample detection. Photocathode produces low photocurrent signal and gives rise to poor sensitivity. Herein, a novel cathode photoelectrochemical (CPEC) sensing platform based on Ag-AgI-CNTs as photocathode material and K3[Fe(CN)6] as photoelectron acceptor was established. Since [Fe(CN)6]3- effectively accepted photoelectrons from Ag-AgI-CNTs, it greatly enhanced the CPEC response. Combining a surface multisite strand displacement amplification (SMSDA) strategy, the CPEC platform was applied for the activity assay of terminal deoxynucleotidyl transferase (TdT). In this proposal, oligo dT primer tethered on CPEC platform was in-situ extended to generate a polyA tail. Then the polyA tail formed a stable multi-point hybrid structure with the adjacent oligo dT. After launching the SMSDA, the CPEC platform was covered by more elongated polynucleotide chains and network, which acutely hampered the photoelectron transfer (eT) between photocathode and electron acceptor and caused a reduced photocurrent. The CPEC sensor possessed a satisfactory linear response from 6 × 10-5-0.1 U and a low detection limit of 1.1 × 10-5 U. The strategy offered a more specific and sensitive method for TdT activity assay. It was feasible in the field of TdT-based biochemical research, drug screening, and disease diagnosis.

Mutational analysis of Arabidopsis PP2CA2 involved in abscisic acid signal transduction.

The homozygous T-DNA mutant of the PP2CA2 gene in Arabidopsis thaliana was identified at DNA and RNA levels. The semi-quantitative RT-PCR analysis showed expression of PP2CA2 was induced by NaCl and ABA. When grown in presence of increasing concentration of exogenous ABA the pp2ca2 mutant showed a significant loss of ABA sensitivity in terms of seed germination, efficiency of post-germination growth and root growth. In presence of all ABA and NaCl concentrations tested the germination percentage of wild-type seeds was lower than that of mutant ppca2 seeds. Furthermore, in the presence of exogenous ABA, the pp2ca2 seeds showed higher germination percentages than wild-type at different stages of development and the pp2ca2 seedlings showed a reduced inhibition of root growth compared with wild-type plants. The above results indicated that the pp2ca2 was an ABA-hyposensitive mutant.

Selectively monitoring glutathione in human serum and growth-associated living cells using gold nanoclusters.

Glutathione (GSH) plays a variety of vital functions in biological systems. Growth-associated change of GSH level in cells might be critical for cell survival and monitoring of GSH in living cells are of great significance for understanding the dynamic link between GSH and some diseases. In this work, chitason micelles templated gold nanoclusters (CM-Au NCs) emitting red fluorescence were prepared with a simple and rapid method, which shows interesting phenomenon of aggregation induced emission (AIE) affected by the size of the chitosan micelles. The unique CM-Au NCs can be used to develop turn-off fluorescent probe for detecting GSH in human serum and living cells based on the reverse process of AIE of CM-Au NCs, completely different from the principle of aggregation caused quenching (ACQ) effect, which can distinguish GSH from other biothiols (cysteine and homocysteine) and quantitatively detect GSH concentration of human serum in healthy people and cancer patients with high sensitivity. The practical application of fluorescent CM-Au NCs for cellular imaging and detecting GSH level indicates ultra-trace changes of GSH levels in normal and cancer cells could be monitored at different growth stages, which reveals that the levels of GSH in cancer cells was always higher than that of normal cells. Compared with commercial GSH assay kits for detection GSH in human serum and living cells, the proposed method was verified to be accuracy and precision. The results not only reflect the changes of GSH during cell growth at different stages, but also demonstrate the feasibility of reverse process of AIE of CM-Au NCs for detection GSH. This strategy would provide a platform to understand the dynamic link between GSH and disease to clarify the disease mechanism.