Application and Mechanism of Cryptolepine and Neocryptolepine Derivatives as T3SS Inhibitors for Control of Bacterial Leaf Blight on Rice.

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv oryzae (Xoo) is extremely harmful to rice production. The traditional control approach is to use bactericides that target key bacterial growth factors, but the selection pressure on the pathogen makes resistant strains the dominant bacterial strains, leading to a decline in bactericidal efficacy. Type III secretion system (T3SS) is a conserved and critical virulence factor in most Gram-negative bacteria, and its expression or absence does not affect bacterial growth, rendering it an ideal target for creating drugs against Gram-negative pathogens. In this work, we synthesized a range of derivatives from cryptolepine and neocryptolepine. We found that compound Z-8 could inhibit the expression of Xoo T3SS-related genes without affecting the growth of bacteria. an in vivo bioassay showed that compound Z-8 could effectively reduce the hypersensitive response (HR) induced by Xoo in tobacco and reduce the pathogenicity of Xoo in rice. Furthermore, it exhibited synergy in control of bacterial leaf blight when combined with the quorum quenching bacterial F20.

Development of Ru-polypyridyl complexes for real-time monitoring of Aß oligomers and inhibition of Aß fibril formation.

The aggregation of amyloid-ß (Aß) is one of the important pathological markers of Alzheimer's disease. Ruthenium(II) complexes have good stability, low cytotoxicity, a high fluorescence quantum yield, and a good Stokes shift as fluorescent probes. Based on this, we constructed a fluorescent probe for in vivo real-time imaging and inhibition of Aß-fibril formation using a complex of Ru polypyridine with organic fluorophores (N,N-dimethylaniline) and hydrophobic peptides (KLVFF). DLS and TEM studies have shown that Ru-YH has an inhibitory effect on the fibrotic aggregation of Aß. Both in vivo and in vitro studies have shown that Ru-WJ and Ru-YH can quickly cross the blood-brain barrier and successfully detect Aß in early (2.5-month old) transgenic mouse models. In summary, we have explored the potential of Ru complex based biological probes for early diagnosis and inhibition of AD.

Repurposing a human acetyl-CoA carboxylase inhibitor firsocostat to treat fungal candidiasis alone and in combination.

Opportunistic fungal infections, particularly caused by Candida albicans, remain a common cause of high morbidity and mortality in immunocompromised patients. The escalating prevalence of antifungal drug resistance necessitates the immediate exploration of alternative treatment strategies to combat these life-threatening fungal diseases. In this study, we investigated the antifungal efficacy of firsocostat, a human acetyl-CoA carboxylase (ACC) inhibitor, against C. albicans. Firsocostat alone displayed moderate antifungal activity, while combining it with voriconazole, itraconazole, or amphotericin B exhibited synergistic effects across almost all drug-sensitive and drug-resistant C. albicans strains tested. These observed synergies were further validated in two mouse models of oropharyngeal and systemic candidiasis, where the combination therapies demonstrated superior fungicidal effects compared to monotherapy. Moreover, firsocostat was shown to directly bind to C. albicans ACC and inhibit its enzymatic activity. Sequencing spontaneous firsocostat-resistant mutants revealed mutations mapping to C. albicans ACC, confirming that firsocostat has retained its target in C. albicans. Overall, our findings suggest that repurposing firsocostat, either alone or in combination with other antifungal agents, holds promising potential in the development of antifungal drugs and the treatment of candidiasis.

Mechanistic insights into the selectivity of bicyclophosphorothionate antagonists for housefly versus rat GABA receptors.

BACKGROUND: γ-Aminobutyric acid (GABA) receptors (GABARs) are validated targets of insecticides. Bicyclophosphorothionates are a group of insecticidal compounds that act as noncompetitive antagonists of GABARs. We previously reported that the analogs exhibit various degrees of selectivity for housefly versus rat GABARs, depending on substitutions at the 3- and 4-positions. We here sought to elucidate the unsolved mechanisms of the receptor selectivity using quantitative structure-activity relationship (QSAR), molecular docking, and molecular dynamics approaches. RESULTS: Three-dimensional (3D)-QSAR studies using Topomer comparative molecular field analysis quantitatively demonstrated how the introduction of a small alkyl group at the 3-position of bicyclophosphorothionates contributes to the housefly versus rat GABAR selectivity. To investigate the molecular mechanisms of the selective action, bicyclophosphorothionates were docked into housefly Resistance to dieldrin (RDL) GABAR and rat α1ß2γ2 GABAR homology models built using the published 3D-structures of human GABARs as templates. The results of molecular docking and molecular dynamics simulations revealed that the 2'Ala and 6'Thr residues of the RDL subunit within the channel are the key amino acids for binding to the housefly GABARs, whereas the 2'Ser residue of γ2 subunit plays a crucial role in binding to rat GABARs. CONCLUSION: We revealed the molecular mechanisms underlying the selective antagonistic action of bicyclophosphorothionates on housefly versus rat GABARs. The information presented should help design and develop novel, safe GABAR-targeting insecticides. © 2023 Society of Chemical Industry.

A glutamate-gated chloride channel as the mite-specific target-site of dicofol and other diphenylcarbinol acaricides.

Dicofol has been widely used to control phytophagous mites. Although dicofol is chemically related to DDT, its mode of action has remained elusive. Here, we mapped dicofol resistance in the spider mite Tetranychus urticae to two genomic regions. Each region harbored a glutamate-gated chloride channel (GluCl) gene that contained a mutation-G314D or G326E-known to confer resistance against the unrelated acaricide abamectin. Using electrophysiology assays we showed that dicofol and other diphenylcarbinol acaricides-bromopropylate and chlorobenzilate-induce persistent currents in Xenopus oocytes expressing wild-type T. urticae GluCl3 receptors and potentiate glutamate responses. In contrast, the G326E substitution abolished the agonistic activity of all three compounds. Assays with the wild-type Drosophila GluClα revealed that this receptor was unresponsive to dicofol. Homology modeling combined with ligand-docking confirmed the specificity of electrophysiology assays. Altogether, this work elucidates the mode of action of diphenylcarbinols as mite-specific agonists of GluCl.

Binuclear cobalt(II) and two-dimensional manganese(II) coordination compounds self-assembled by mixed bipyridine-tetracarboxylic ligands with single-ion magnet properties.

A cobalt(II) complex and manganese(II) coordination polymer, formulated as [Co2(H2btca)(mbpy)4][H2btca]·4H2O (1) and {Mn2(btca)(mbpy)2(H2O)2}n (2) (H4btca = 1,2,4,5-benzenetetracarboxylic acid; mbpy = 4,4'-dimethyl-2,2'-bipyridyl), constructed by mixed bipyridine-tetracarboxylic ligands were synthesized and characterized. Single-crystal structural analyses reveal that compound 1 is a discrete neutral binuclear molecule, while compound 2 is a two-dimensional (2D) coordination polymer. The metal ions in these compounds are well isolated, with an intramolecular Co2+⋯Co2+ distance of 9.170 Å for 1 and Mn2+⋯Mn2+ separation of 10.984 and 11.164 Å for 2 due to the bulk tetracarboxylic linker. This isolation gives rise to a single-ion magnetism origin of the compounds. Magnetic studies reveal a large zero-field splitting parameter D of 82.6 cm-1 for 1, while a very small D of 0.42 cm-1 was observed for 2. Interestingly, dynamic ac magnetic measurements exhibited slow magnetic relaxation under the external dc field of the two compounds, revealing the field-supported single-ion magnet (SIM) of 1 and 2. The detailed theoretical calculations were further applied to understand the electronic structures, magnetic anisotropy, and relaxation dynamics in 1 and 2. Combined with our recently reported compound (Eur. J. Inorg. Chem., 2022, e202200354), the foregoing results provide not only a rare binuclear cobalt(II) SIM and the first 2D manganese(II) SIM coordination polymer but also a bipyridine-tetracarboxylic ligand approach toward novel SIMs.

G3'MTMD3 in the insect GABA receptor subunit, RDL, confers resistance to broflanilide and fluralaner.

Meta-diamides (e.g. broflanilide) and isoxazolines (e.g. fluralaner) are novel insecticides that target the resistant to dieldrin (RDL) subunit of insect γ-aminobutyric acid receptors (GABARs). In this study, we used in silico analysis to identify residues that are critical for the interaction between RDL and these insecticides. Substitution of glycine at the third position (G3') in the third transmembrane domain (TMD3) with methionine (G3'M TMD3), which is present in vertebrate GABARs, had the strongest effect on fluralaner binding. This was confirmed by expression of RDL from the rice stem borer, Chilo suppressalis (CsRDL) in oocytes of the African clawed frog, Xenopus laevis, where the G3'MTMD3 mutation almost abolished the antagonistic action of fluralaner. Subsequently, G3'MTMD3 was introduced into the Rdl gene of the fruit fly, Drosophila melanogaster, using the CRISPR/Cas9 system. Larvae of heterozygous lines bearing G3'MTMD3 did not show significant resistance to avermectin, fipronil, broflanilide, and fluralaner. However, larvae homozygous for G3'MTMD3 were highly resistant to broflanilide and fluralaner whilst still being sensitive to fipronil and avermectin. Also, homozygous lines showed severely impaired locomotivity and did not survive to the pupal stage, indicating a significant fitness cost associated with G3'MTMD3. Moreover, the M3'GTMD3 mutation in the mouse Mus musculus α1ß2 GABAR increased sensitivity to fluralaner. Taken together, these results provide convincing in vitro and in vivo evidence for both broflanilide and fluralaner acting on the same amino acid site, as well as insights into potential mechanisms leading to target-site resistance to these insecticides. In addition, our findings could guide further modification of isoxazolines to achieve higher selectivity for the control of insect pests with minimal effects on mammals.

Peptide MSI-1 inhibited MCR-1 and regulated outer membrane vesicles to combat immune evasion of Escherichia coli.

Polymyxin resistance is conferred by MCR-1 (mobile colistin resistance 1)-induced lipopolysaccharide (LPS) modification of G- bacteria. However, the peptide MSI-1 exerts potent antimicrobial activity against mcr-1-carrying bacteria. To further investigate the potential role of MCR-1 in improving bacterial virulence and facilitating immune evasion, and the immunomodulatory effect of peptide MSI-1, we first explored outer membrane vesicle (OMV) alterations of mcr-1-carrying bacteria in the presence and absence of sub-MIC MSI-1, and host immune activation during bacterial infection and OMV stimulation. Our results demonstrated that LPS remodelling induced by MCR-1 negatively affected OMV formation and protein cargo by E. coli. In addition, MCR-1 diminished LPS-stimulated pyroptosis but facilitated mitochondrial dysfunction, further aggravating apoptosis in macrophages induced by OMVs of E. coli. Similarly, TLR4-mediated NF-κB activation was markedly alleviated once LPS was modified by MCR-1. However, peptide MSI-1 at the sub-MIC level inhibited the expression of MCR-1, further partly rescuing OMV alteration and attenuation of immune responses in the presence of MCR-1 during both infection and OMV stimulation, which can be exploited for anti-infective therapy.

Characteristics of Virulent ST5-SCCmec II Methicillin-Resistant Staphylococcus aureus Prevalent in a Surgery Ward.

Objective: To investigate the transmission pathway of a MRSA prevalence in a pancreatic surgery ward in a Chinese teaching hospital. Methods: Molecular epidemiology investigations were carried out combined PFGE, MLST, SCCmec typing and whole-genome sequencing for 20 successive MRSA isolates (2 isolates from the ward environment). Resistance and virulence genes were detected using specific PCR. Bacterial identification and AST were performed using the Vitek 2 Compact System. Clinical data of enrolled cases were retrieved from electronic case records. Results: From January 2020 to May 2020, successive isolated 20 MRSA strains were clarified to 2 PFGE patterns (A = 19, B = 1) in the ward. Both isolates from environment and patients belonged to sequence type ST5-SCCmec II-spa type t311. MRSA-related resistance genes mecA, blaZ, ermA, ant(4')-Ia and norA were found in each clone. All 20 isolates carried tst, hlg, hla, eta, eap, fnbA and seo virulence genes, other virulence genes such as sea, sec, seb, seg, sei, sem, sen, ebpS and fnbB were also found in partial stains. All patients had fever symptom, 27.8% were accompanied by diarrhea, 88.9% had undergone surgery or invasive procedures within 30 days. Finally, 94.4% of these patients recovered. Conclusion: This study confirmed a prevalence of ST5-MRSA-II-t311 clone in a surgery ward, indicated MRSA is a risk factor for post-surgery nosocomial infection and hand hygiene and environmental surveillance should not be ignored.

A novel strategy of designing neutrophil elastase fluorescent probe based on self-immolative group and its application in bioimaging.

Neutrophil elastase (NE) is an important regulator of immune response and is widely regarded as a biomarker for inflammatory diseases. To date, all the NE probe is designed by linking pentafluoropropionyl and amino-containing fluorophores through amide bond. This method is limited by the fluorophores, which must contain amino functional groups. To overcome this problem, we use the self-immolative group to convert hydroxyl groups to fluorophores HFC (4-trifluoromethyl-7-hydroxyl coumarin) into amino groups, and to connect recognition groups (pentafluoropropionyl) to construct a novel NE fluorescent probe HFC-NE. Predictably, HFC-NE can detect NE activity selectively and sensitively with many advantages, such as good water solubility and biocompatibility, high fluorescence enhancement and high affinity. Besides, HFC-NE is successfully applied to real-time and specific detection of NE activity in living cells and zebrafish models. These excellent outcomes confirmed that this strategy based on self-immolative group is a useful method to design more NE fluorescent probes.

A tyrosinase fluorescent probe with large Stokes shift and high fluorescence enhancement for effective identification of liver cancer cells.

Tyrosinase is widely regarded as an important biomarker for melanocytic and liver cancer. However, most currently reported tyrosinase probes have been focused on malignant melanoma study, and few tyrosinase probe have been applied for liver cancer investigation. Herein, we developed a novel probe HFC-TYR for sensitive and selective tracking of tyrosinase activity at enzyme and cellular level, and investigated its application for liver cancer diagnosis. As expected, HFC-TYR has excellent response ability for tyrosinase sensing at enzyme level, such as large Stokes shift (170 nm), high fluorescence enhancement (178-fold), low detection limit (0.12 U/mL), which indicates its potential for efficient identification of endogenous tyrosinase activity at cellular levels. Unsurprisingly, HFC-TYR is proved to be able detect endogenous tyrosinase levels in various living cells. More importantly, HFC-TYR is successfully used to distinguish HepG2 cells from other cells (SKOV3, HeLa and 293T), indicating that tyrosinase is overexpressed in HepG2 cells and HFC-TYR can specifically identify HepG2 cells at cellular level. Meanwhile, HFC-TYR is able to further monitor the endogenous tyrosinase activity in zebrafish models. Therefore, all the findings confirm that HFC-TYR has the application potential of liver cancer diagnosis.

Fabrication of highly fluorinated porphyrin-based covalent organic frameworks decorated Fe3O4 nanospheres for magnetic solid phase extraction of fluoroquinolones.

A highly fluorinated porphyrin-based covalent organic frameworks magnetic adsorbent (FPy-COF@PDA@Fe3O4) was fabricated by using polydopamine (PDA) grafting Fe3O4 nanospheres as magnetic core and FPy-COF as shell for magnetic solid phase extraction (MSPE) of fluoroquinolones (FQs). FPy-COF was constructed by using 5,15-bis(4-aminophenyl)-10,20-bis(perfluorophenyl)porphyrin and 4,4'-biphenyldicarboxaldehyde as two building blocks. PDA as a bridge grafting on the surface of Fe3O4 nanospheres facilitated the growth of FPy-COF. The morphology and structure of FPy-COF@PDA@Fe3O4 adsorbent were characterized in detail. The prepared magnetic adsorbent exhibited good extraction capability to amphiphilic FQs due to their superior chemical affinities such as fluorophilic interaction and hydrogen-bond interaction from nitrogen-rich skeleton. Under the optimized conditions, the MSPE method combined with high performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed to sensitively quantify trace level of six FQs in milk samples. The developed MSPE-HPLC method showed good linearity with wide concentration range, precision, and low limits of detection (S/N = 3) for six FQs as low as 2.3 ngꞏmL-1 in milk. The extraction recoveries of different spiked concentrations were in the range 77.8-110.4% for milk samples with RSD less than 9.7%.

Iron porphyrin-based porous organic polymer with high peroxidase-like activity as colorimetric sensor for glutathione and ascorbic acid assay.

A new iron porphyrin-based organic polymer (Fe-POP) was synthesized through the William ether reaction. The as-prepared Fe-POP presented high chemical stability, wide pore distribution, high iron content, and strong affinity with 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), which contributed to its excellent peroxidase-mimicking performance. In the presence of H2O2, Fe-POP could catalyze the transparent TMB into blue ox-TMB, which could be easily distinguished by the naked eyes. Moreover, glutathione (GSH) and ascorbic acid (AA) could convert blue ox-TMB into colorless TMB due to the inhibitory effect of GSH/AA to the catalytic oxidation of TMB. Based on this phenomenon, a rapid and sensitive colorimetric method for the assay of H2O2, GSH, and AA was developed using Fe-POP as sensor. The detection limits of H2O2, GSH, and AA  were 1.37, 0.44, and 0.33 µM, respectively. Finally, the colorimetric method based on Fe-POP was used to evaluate the GSH and AA content in real samples, which provided the guidance for GSH and AA supplements in our daily diet, suggesting the significant potential of Fe-POP in practical applications.

Exploration of N-Arylsulfonyl-indole-2-carboxamide Derivatives as Novel Fructose-1,6-bisphosphatase Inhibitors by Molecular Simulation.

A series of N-arylsulfonyl-indole-2-carboxamide derivatives have been identified as potent fructose-1,6-bisphosphatase (FBPase) inhibitors (FBPIs) with excellent selectivity for the potential therapy of type II diabetes mellitus. To explore the structure-activity relationships (SARs) and the mechanisms of action of these FBPIs, a systematic computational study was performed in the present study, including three-dimensional quantitative structure-activity relationship (3D-QSAR) modeling, pharmacophore modeling, molecular dynamics (MD), and virtual screening. The constructed 3D-QSAR models exhibited good predictive ability with reasonable parameters using comparative molecular field analysis (q2 = 0.709, R2 = 0.979, rpre2 = 0.932) and comparative molecular similarity indices analysis (q2 = 0.716, R2 = 0.978, rpre2 = 0.890). Twelve hit compounds were obtained by virtual screening using the best pharmacophore model in combination with molecular dockings. Three compounds with relatively higher docking scores and better ADME properties were then selected for further studies by docking and MD analyses. The docking results revealed that the amino acid residues Met18, Gly21, Gly26, Leu30, and Thr31 at the binding site were of great importance for the effective bindings of these FBPIs. The MD results indicated that the screened compounds VS01 and VS02 could bind with FBPase stably as its cognate ligand in dynamic conditions. This work identified several potential FBPIs by modeling studies and might provide important insights into developing novel FBPIs.

Red-Emissive Sulfur-Doped Carbon Dots for Selective and Sensitive Detection of Mercury (II) Ion and Glutathione.

Carbon dots (CDs) show great potential in bioimaging and biosensing because of their good biocompatibility and excellent optical properties. However, CDs with intense red emissions for sensitive and selective detection are rarely reported. Herein, we prepared the red-emissive carbon dots (RCDs) through a facile hydrothermal method using tetra (4-carboxyphenyl) porphyrin (TCPP) and thiourea as starting materials. The obtained RCDs were characterized by TEM, XRD, and XPS. RCDs exhibited high water solubility and strong red emission (λem = 650 nm), with the fluorescence quantum yield as high as 26.7%, which was greatly higher than that of TCPP. Moreover, the as-prepared RCDs could be acted as a highly selective and sensitive probe for the detection of Hg2+ and glutathione (GSH) through the fluorometric titration method. The detection limits of Hg2+ and GSH were calculated to be 1.73 and 1.6 nM, respectively. The cellular experiments demonstrated the good biocompatibility of RCDs and their feasibility in bioimaging. Thus, this work provided a simple strategy to design and synthesize the highly red-emissive carbon dots, which showed promising application in biological and environmental assays.

Identification of Molecular Targets and Potential Mechanisms of Yinchen Wuling San Against Head and Neck Squamous Cell Carcinoma by Network Pharmacology and Molecular Docking.

Head and neck squamous cell carcinoma (HNSCC) represents one of the most malignant and heterogeneous tumors, and the patients have low 5-year survival. Traditional Chinese medicine (TCM) has been demonstrated as an effective complementary and/or alternative therapy for advanced malignancies including HNSCC. It has been noted that several herbs that are used for preparing Yinchen Wuling San (YWLS) have anti-tumor activities, whereas their mechanisms of action remain elusive. In this study, network pharmacology and molecular docking studies were employed to explore the underlying mechanisms of action of YWLS against HNSCC. The 58 active ingredients from six herbs used for YWLS and their 506 potential targets were screened from the traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP) and SwissTargetPrediction database. A total of 2,173 targets associated with HNSCC were mainly identified from the DisGeNET and GeneCards databases. An active components-targets-disease network was constructed in the Cytoscape. Top 20 hub targets, such as AKT1, EGFR, TNF, ESR1, SRC, HSP90AA1, MAPK3, ERBB2, and CCND1, were identified by a degree in the protein-protein interaction (PPI) network. Gene functional enrichment analysis showed that PI3K-AKT, MAPK, Ras, TNF, and EGFR were the main signaling pathways of YWLS in treating HNSCC. There were 48 intersected targets such as EGFR, AKT1, and TNF that were associated with patients' outcomes by the univariate Cox analysis, and most of them had increased expression in the tumor as compared to normal tissues. The area under curves of receiver operating characteristic indicated their diagnostic potential. Inhibition of these survival-related targets and/or combination with EGFR or AKT inhibitors were promising therapeutic options in HNSCC. The partial active components of YWLS exhibited good binding with the hub targets, and ADME analysis further evaluated the drug-likeness of the active components. These compounds and targets identified in this study might provide novel treatment strategies for HNSCC patients, and the subsequent work is essential to verify the underlying mechanisms of YWLS against HNSCC.

Structural insights into the interaction between gabazine (SR-95531) and Laodelphax striatellus GABA receptors.

γ-Aminobutyric acid receptors (GABARs) mediate fast inhibitory neurotransmission and are targets for insecticides. GABARs are composed of five subunits, the composition of which dictates the pharmacological characteristics of GABARs. Both competitive and noncompetitive GABAR antagonists can be used as insecticides. Gabazine is a potent competitive antagonist of mammalian α1ß2γ2 GABARs; however, it is less potent against insect GABARs. To explore how gabazine interacts with GABARs, we examined whether the sensitivity of the small brown planthopper (Laodelphax striatellus) RDL GABAR (LsRDLR) to gabazine is increased when its amino acid residues are substituted with α1ß2γ2 GABAR residues. In the results, two of the generated mutants showed enhanced gabazine sensitivity. Docking simulations of gabazine using LsRDLR homology models and an α1ß2γ2 GABAR cryo-EM structure revealed that the accommodation of gabazine into the "aromatic box" in the orthosteric site lowered the binding energy. This information may help in designing GABAR-targeting insecticides with novel modes of action.

Coumarin-based turn-on fluorescence probe with a large Stokes shift for detection of endogenous neutrophil elastase in live cells and zebrafish.

Neutrophil elastase (NE), a serine proteinase, is a significant biomarker which is closely related to the progress of diseases. However, only few probes have been reported for detection of NE activity and cell imaging. And these probes have exhibited small Stokes shift, which leads to high fluorescence interferences. Furthermore, only one probe among them is able to image NE in vivo successfully. To overcome the above problems, we designed a novel coumarin-based fluorescent probe HNCOU-NE with large Stokes shift to visualize NE activity in living cells and zebrafish. The new probe HNCOU-NE for NE contains fluorophore HNCOU as the reporter and pentafluoroethyl as the enzyme-active trigger moiety. As expected, HNCOU-NE displays perfect detecting performance for sensing of NE, including good water solubility, large Stokes shift, high affinity and wide linear response concentration. In addition, HNCOU-NE has been successfully utilized for NE real-time detection and imaging in different living cells, exhibiting low cytotoxicity and excellent biocompatibility. Most importantly, endogenous NE fluorescence imaging experiments reveals that HNCOU-NE can distinguish liver cancer cells (HepG2) and other cells (293T, HeLa and SKOV3), illustrating its specific ability to diagnose liver cancer cells. Besides, probe HNCOU-NE also has the ability to specifically detect endogenous NE activity in living zebrafish. All the results indicate that HNCOU-NE is a valuable probe for qualitative and quantitative sensing of NE activity in vitro and in vivo.

A controllable staining colorimetric method based on carboxylated cellulose membranes for early-warning and semi-quantitative detection of aflatoxins in water.

The group specific assay of total aflatoxins (AFs) often requires specific antibodies. A controllable staining colorimetric method was proposed to determine AFs by exploiting controllable electrostatic-staining of carboxylated cellulose membranes (CCMs) with Hg2+-capped gold nanoparticles (AuNPs). Under electrostatic force, Hg2+ connects AuNPs and CCMs like a bridge, causing CCMs to be stained by AuNPs. The two adjacent carbonyl groups in the AF structure can chelate Hg2+. When AFs are present, Hg2+ and AFs will form complexes, which reduces the attachment of AuNPs on the CCMs. Therefore, the different degrees of electrostatic-staining of CCMs show different color changes. Based on this phenomenon, a naked-eye colorimetric detection assay of AFs was designed. The visual limit of detection (VLOD) reached 10 ppb, which makes it easily and effectively complete the early-warning and semi-quantitative detection of AFs. To our knowledge, this is the first method for colorimetric detection of AFs based on the controllable electrostatic-staining mechanism, which can be used for the determination of AFs in actual water samples such as beer and beverages. Besides, the colorimetric sensing method based on the controllable electrostatic-staining mechanism provides a novel methodology for early-warning and semi-quantitative detection of toxic and hazardous substances.