Fast and accurate detection of microorganisms is of key importance in clinical analysis and in food and water quality monitoring. Salmonella typhimurium is responsible for about a third of all cases ...of foodborne diseases and consequently, its fast detection is of great importance for ensuring the safety of foodstuffs.
We report the development of a label-free impedimetric aptamer-based biosensor for S. typhimurium detection. The aptamer biosensor was fabricated by grafting a diazonium-supporting layer onto screen-printed carbon electrodes (SPEs), via electrochemical or chemical approaches, followed by chemical immobilisation of aminated-aptamer. FTIR-ATR, contact angle and electrochemical measurements were used to monitor the fabrication process. Results showed that electrochemical immobilisation of the diazonium-grafting layer allowed the formation of a denser aptamer layer, which resulted in higher sensitivity. The developed aptamer-biosensor responded linearly, on a logarithm scale, over the concentration range 1×101 to 1×108CFUmL−1, with a limit of quantification (LOQ) of 1×101CFUmL−1 and a limit of detection (LOD) of 6CFUmL−1. Selectivity studies showed that the aptamer biosensor could discriminate S. typhimurium from 6 other model bacteria strains. Finally, recovery studies demonstrated its suitability for the detection of S. typhimurium in spiked (1×102, 1×104 and 1×106CFUmL−1) apple juice samples.
•Rapid (30min) label-free detection of S. typhimurium.•Highly selective and sensitive (1×101CFUmL−1) biosensor for S. typhimurium.•Label free detection of S. typhimurium in spiked apple juice samples.•Diazonium based architecture for robust and sensitive electrochemical aptasensor.
The synthetic utilities of the diazo and diazonium groups are matched only by their reputation for explosive decomposition. Continuous processing technology offers new opportunities to make and use ...these versatile intermediates at a range of scales with improved safety over traditional batch processes. In this minireview, the state of the art in the continuous flow processing of reactive diazo and diazonium species is discussed.
Safety first: The synthetic utilities of the diazo and diazonium groups are matched only by their reputation for explosive decomposition. Continuous processing technology offers new opportunities to make and use these versatile intermediates with improved safety. This Minireview discusses the state of the art in flow chemistry involving these reactive species.
Like normal cellular nucleosides, the nucleoside reverse transcriptase (RT) inhibitor (NRTI) 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) has a 3'-hydroxyl moiety, and yet EFdA is a highly potent ...inhibitor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replication with activity against a broad range of clinically important drug-resistant HIV isolates. We evaluated the anti-HIV activity of EFdA in primary human cells and in HIV-infected humanized mice. EFdA exhibited excellent potency against HIVJR-CSF in phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs), with a 50% inhibitory concentration of 0.25 nM and a selectivity index of 184,000; similar antiviral potency was found against 12 different HIV clinical isolates from multiple clades (A, B, C, D, and CRF01_AE). EFdA was readily absorbed after oral dosing (5 mg/kg of body weight) in both mice and the rhesus macaque, with micromolar levels of the maximum concentration of drug in serum (Cmax) attained at 30 min and 90 min, respectively. Trough levels were at or above 90% inhibitory concentration (IC90) levels in the macaque at 24 h, suggesting once-daily dosing. EFdA showed reasonable penetration of the blood-brain barrier in the rhesus macaque, with cerebrospinal fluid levels at approximately 25% of plasma levels 8 h after single oral dosing. Rhesus PBMCs isolated 24 h following a single oral dose of 5 mg/kg EFdA were refractory to SIV infection due to sufficiently high intracellular EFdA-triphosphate levels. The intracellular half-life of EFdA-triphosphate in PBMCs was determined to be >72 h following a single exposure to EFdA. Daily oral administration of EFdA at low dosage levels (1 to 10 mg/kg/day) was highly effective in protecting humanized mice from HIV infection, and 10 mg/kg/day oral EFdA completely suppressed HIV RNA to undetectable levels within 2 weeks of treatment.
Copper capabilities: Diazonium salts are converted into the corresponding trifluoromethyl derivatives in the presence of a trifluoromethyl–copper complex generated in situ from CuSCN and the ...inexpensive, easy‐to‐use trifluoromethylating reagent Me3Si‐CF3 (see scheme). This Sandmeyer‐type reaction allows the straightforward synthesis of trifluoromethylated arenes and heteroarenes from the corresponding amines.
Lewis base adducts of tetra-alkoxy diboron compounds, in particular bis(pinacolato)diboron (B2 pin2 ), have been proposed as the active source of nucleophilic boryl species in metal-free borylation ...reactions. We report the isolation and detailed structural characterization (by solid-state and solution NMR spectroscopy and X-ray crystallography) of a series of anionic adducts of B2 pin2 with hard Lewis bases, such as alkoxides and fluoride. The study was extended to alternative Lewis bases, such as acetate, and other diboron reagents. The B(sp(2) )-B(sp(3) ) adducts exhibit two distinct boron environments in the solid-state and solution NMR spectra, except for (4-tBuC6 H4 O)B2 pin2 (-) , which shows rapid site exchange in solution. DFT calculations were performed to analyze the stability of the adducts with respect to dissociation. Stoichiometric reaction of the isolated adducts with two representative series of organic electrophiles-namely, aryl halides and diazonium salts-demonstrate the relative reactivities of the anionic diboron compounds as nucleophilic boryl anion sources.
The reliable integration of new nanocarbons in future molecular and hybrid electronics requires mastery of chemical binding between dissimilar materials down to the individual bond. Here, we present ...a detailed study of covalent grafting of aryl radicals on single crystal Au(111), and investigate their electrochemical stability and oxidative desorption. Copper underpotential deposition and Gaussian deconvolution of its current–potential trace are used to map the thermodynamic and kinetic landscape of the modified Au surface. Scanning tunnelling microscopy in a high-boiling organic solvent suggests that grafting is accompanied by vacancy island formation on the Au surface, while iodide adsorption heals these vacancies and allows high-contrast imaging of individual covalent grafts.
Diazo groups have broad and tunable reactivity. That and other attributes endow diazo compounds with the potential to be valuable reagents for chemical biologists. The presence of diazo groups in ...natural products underscores their metabolic stability and anticipates their utility in a biological context. The chemoselectivity of diazo groups, even in the presence of azido groups, presents many opportunities. Already, diazo compounds have served as chemical probes and elicited novel modifications of proteins and nucleic acids. Here, we review advances that have facilitated the chemical synthesis of diazo compounds, and we highlight applications of diazo compounds in the detection and modification of biomolecules.
Under acidic conditions, reduced graphene oxide (rGO) was functionalized with p‐aminobenzoic acid, which formed the diazonium ions through the diazotization with a wet‐chemical method. Surfactants or ...stabilizers were not applied during the diazotization. After the functionalized rGO was treated through mild sonication in aqueous solution, these functionalized rGO sheets were less than two layers, which was determined by atomic force microscopy (AFM) imaging. The water solubility of functionalized rGO after the introduction of polyethyleneimine (PEI) was improved significantly; it was followed by covalent binding of folic acid (FA) molecules to the functionalized rGO to allow us to specifically target CBRH7919 cancer cells by using FA as a receptor. The loading and release behaviors of elsinochrome A (EA) and doxorubicin (DOX) on the functionalized rGO sheets were investigated. The EA loading ratio onto rGO‐C6H4‐CO‐NH‐PEI‐NH‐CO‐FA (abbreviated rGO‐PEI‐FA, the weight ratio of drug loaded onto rGO‐PEI‐FA) was approximately 45.56 %, and that of DOX was approximately 28.62 %. It was interesting that the drug release from rGO‐PEI‐FA was pH‐ and salt‐dependent. The results of cytotoxicity (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) and flow cytometry (FCM) assays, as well as cell morphology observations) clearly showed that the concentration of rGO‐PEI‐FA as the drug‐delivery composite should be less than 12.5 mg L−1. The conjugation of DOX and rGO‐PEI‐FA can enhance the cancer‐cell apoptosis effectively and can also push the cancer cells to the vulnerable G2 phase of the cell cycle, which is most sensitive and susceptible to damage by drugs or radiation.
New horizons: A novel method for covalent modification of reduced graphene oxide (rGO) by means of diazonium chemistry was developed. The functionalized‐rGO drug‐delivery system was tested for the first time (see scheme) and provided a new vision for functionalizing rGO and studying drug‐delivery systems based on graphene materials.
In the presence of catalytic {IrCp*Cl2}2 and Ag2CO3, Li2CO3 as the base, and acetone as the solvent, benzoic acids react with arenediazonium salts to give the corresponding diaryl‐2‐carboxylates ...under mild conditions. This CH arylation process is generally applicable to diversely substituted substrates, ranging from extremely electron‐rich to electron‐poor derivatives. The carboxylate directing group is widely available and can be removed tracelessly or employed for further derivatization. Orthogonality to halide‐based cross‐couplings is achieved by the use of diazonium salts, which can be coupled even in the presence of iodo substituents.
Directing rather than removed: In the presence of catalytic {IrCp*Cl2}2, benzoic acids react with arenediazonium salts to give the corresponding diaryl‐2‐carboxylates. If desired, the carboxylate directing group can be removed by in situ protodecarboxylation.
Synthetic and structural aspects of organofluorine compounds continue to be the focal points of vigorous research activities, as evidenced by the appearance of a large number of publications. Among ...the various useful methodologies for the introduction of fluorine into organic molecules, electrophilic fluorination is a promising and exciting area of research. While a variety of electrophilic fluorinating reagents are available, currently 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo2.2.2octane bis(tetrafluoroborate) (Selectfluor) provides a remarkably straightforward and effective route. The breadth of applications realizable from this reagent in its role as a key electrophilic fluorinating reagent is highlighted here. This Account covers the literature for electrophilic fluorination reactions that employ Selectfluor during the period January 1999−January 2003.
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