Boronic acids can interact with Lewis bases to generate boronate anions, and they can also bind with diol units to form cyclic boronate esters. Boronic acid based receptor designs originated when ...Lorand and Edwards used the pH drop observed upon the addition of saccharides to boronic acids to determine their association constants. The inherent acidity of the boronic acid is enhanced when 1,2-, 1,3-, or 1,4-diols react with boronic acids to form cyclic boronic esters (5, 6, or 7 membered rings) in aqueous media, and these interactions form the cornerstone of diol-based receptors used in the construction of sensors and separation systems. In addition, the recognition of saccharides through boronic acid complex (or boronic ester) formation often relies on an interaction between a Lewis acidic boronic acid and a Lewis base (proximal tertiary amine or anion). These properties of boronic acids have led to them being exploited in sensing and separation systems for anions (Lewis bases) and saccharides (diols). The fast and stable bond formation between boronic acids and diols to form boronate esters can serve as the basis for forming reversible molecular assemblies. In spite of the stability of the boronate esters’ covalent B–O bonds, their formation is reversible under certain conditions or under the action of certain external stimuli. The reversibility of boronate ester formation and Lewis acid–base interactions has also resulted in the development and use of boronic acids within multicomponent systems. The dynamic covalent functionality of boronic acids with structure-directing potential has led researchers to develop a variety of self-organizing systems including macrocycles, cages, capsules, and polymers. This Account gives an overview of research published about boronic acids over the last 5 years. We hope that this Account will inspire others to continue the work on boronic acids and reversible covalent chemistry.
A series of 3-hydroxyflavone (3-HF) ESIPT (excited-state intramolecular proton transfer) boronate-based fluorescent probes have been developed for the detection of peroxynitrite (ONOO–). The dyes are ...environmentally sensitive, and each probe exhibited a ratiometric response toward ONOO– in a micellar environment. The probes were used to image different aggregation states of amyloid-β (Aβ) in the presence of ONOO–. The 3-HF-OMe probe was found to produce a ratiometric response toward ONOO– when bound to Aβ aggregates, resulting in a novel host–guest ensemble, which adds insight into the development of other ESIPT-based probes for the simultaneous sensing of fibrous proteins/peptides and environmental ROS/RNS.
Infection and blockage of indwelling urinary catheters is significant owing to its high incidence rate and severe medical consequences. Bacterial enzymes are employed as targets for small molecular ...intervention in human bacterial infections. Urease is a metalloenzyme known to play a crucial role in the pathogenesis and virulence of catheter-associated Proteus mirabilis infection. Targeting urease as a therapeutic candidate facilitates the disarming of bacterial virulence without affecting bacterial fitness, thereby limiting the selective pressure placed on the invading population and lowering the rate at which it will acquire resistance. We describe the design, synthesis, and in vitro evaluation of the small molecular enzyme inhibitor 2-mercaptoacetamide (2-MA), which can prevent encrustation and blockage of urinary catheters in a physiologically representative in vitro model of the catheterized urinary tract. 2-MA is a structural analogue of urea, showing promising competitive activity against urease. In silico docking experiments demonstrated 2-MA's competitive inhibition, whilst further quantum level modelling suggests two possible binding mechanisms.
Characterization of Staphylococcus aureus clinical isolates derived from lower respiratory tract infections (LRTIs), and correlation between the functionality of the accessory gene regulator (Agr) ...and genotypic and phenotypic characteristics, clinical variables and clinical outcome.
S aureus isolates derived from LRTIs and control groups (nasal carriage and bacteraemia) were genotyped using StaphyType DNA microarray. Agr activity was evaluated using the CAMP synergistic haemolysis assay and the Vesicle Lysis Test (VLT). Discordant strains were analysed by quantitative reverse-transcriptase real-time PCR (qRT-PCR).
Agr was functional in 79.7% and 84.5% of strains according to the CAMP and VLT assays respectively. Higher concordance with RNAIII expression measured by qRT-PCR was observed with the VLT assay (76.2%) compared with the CAMP assay (23.8%). No statistically significant differences were observed in Agr functionality between the study groups, nor the phenotypical/genotypical bacterial characteristics. No association between increased mortality/respiratory complications and Agr function was observed.
Agr activity was high (82.2%) in isolates from LRTIs suggesting the importance of this global regulator in lower respiratory tract colonisation and infection. However, equally high Agr activity was observed in isolates derived from nasal carriage and bacteraemia, contradictory to previous observations. Agr functionality measured by the VLT assay was superior to CAMP assay.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Two 'turn on' TCF-based fluorescence probes were developed for the detection of biological thiols (TCF-GSH and TCFCl-GSH). TCF-GSH was shown to have a high sensitivity towards glutathione (GSH) with ...a 0.28 μM limit of detection. Unfortunately, at higher GSH concentrations the fluorescence intensity of TCF-GSH decreased and toxicity was observed for TCF-GSH in live cells. However, TCFCl-GSH was shown to be able to detect GSH at biologically relevant concentrations with a 0.45 μM limit of detection. No toxicity was found for TCFCl-GSH and a clear 'turn on' with good photostability was observed for the exogenous addition of GSH, Cys and HCys. Furthermore, TCFCl-GSH was used to evaluate the effects of drug treatment on the levels of GSH in live cells.
The early detection of wound infection in situ can dramatically improve patient care pathways and clinical outcomes. There is increasing evidence that within an infected wound the main bacterial mode ...of living is a biofilm: a confluent community of adherent bacteria encased in an extracellular polymeric matrix. Here we have reported the development of a prototype wound dressing, which switches on a fluorescent color when in contact with pathogenic wound biofilms. The dressing is made of a hydrated agarose film in which the fluorescent dye containing vesicles were mixed with agarose and dispersed within the hydrogel matrix. The static and dynamic models of wound biofilms, from clinical strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis, were established on nanoporous polycarbonate membrane for 24, 48, and 72 h, and the dressing response to the biofilms on the prototype dressing evaluated. The dressing indicated a clear fluorescent/color response within 4 h, only observed when in contact with biofilms produced by a pathogenic strain. The sensitivity of the dressing to biofilms was dependent on the species and strain types of the bacterial pathogens involved, but a relatively higher response was observed in strains considered good biofilm formers. There was a clear difference in the levels of dressing response, when dressings were tested on bacteria grown in biofilm or in planktonic cultures, suggesting that the level of expression of virulence factors is different depending of the growth mode. Colorimetric detection on wound biofilms of prevalent pathogens (S. aureus, P. aeruginosa, and E. faecalis) is also demonstrated using an ex vivo porcine skin model of burn wound infection.
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•Spatial distribution of bacteria, bacteriophages and nano-emulsion droplets is identified.•Bacteriophages are ‘shielded’ against external factors by nano-emulsion droplets, and hence ...become more stable.•Zeta potential measurements elucidate the mechanism of enhanced infectivity.•Nano-emulsions eliminate electrostatic repulsion between bacteria and bacteriophages.•Nano-droplets stimulate more effective bacteria/bacteriophage interaction which results in an enhanced killing effect.
In earlier work we have demonstrated the effect that nano-emulsions have on bacterial growth, and most importantly the enhanced bacteriophage infectivity against Staphylococcus aureus in planktonic culture when phage are carried in nano-emulsions. However, the mechanisms of enhancement of the bacteriophage killing effect are not specifically understood. This work focuses on the investigation of the possible interactions between emulsion droplets and bacterial cells, between emulsion droplets and bacteriophages, and finally interactions between all three components: nano-emulsion droplets, bacteria, and bacteriophages. The first approach consists of simple calculations to determine the spatial distribution of the components, based on measurements of particle size. It was found that nano-emulsion droplets are much more numerous than bacteria or bacteriophage, and due to their size and surface area they must be covering the surface of both cells and bacteriophage particles. Stabilisation of bacteriophages due to electrostatic forces and interaction with nano-emulsion droplets is suspected, since bacteriophages may be protected against inactivation due to ‘charge shielding’. Zeta potential was measured for the individual components in the system, and for all of them combined. It was concluded that the presence of nano-emulsions could be reducing electrostatic repulsion between bacterial cells and bacteriophage, both of which are very negatively ‘charged’. Moreover, nano-emulsions lead to more favourable interaction between bacteriophages and bacteria, enhancing the anti-microbial or killing effect. These findings are relevant since the physicochemical properties of nano-emulsions (i.e. particle size distribution and zeta potential) are key in determining the efficacy of the formulation against infection in the context of responsive burn wound dressings—which is the main target for this work.
Data Access: All data created during this research are openly available from the University of Bath data archive at http://doi.org/10.15125/BATH-00166.
This paper describes the modification of nonwoven fabric such that it responds by releasing an encapsulated antimicrobial from within an attached vesicle in response to two species of pathogenic ...bacteria (Staphylococcus aureus MSSA 476 and Pseudomonas aeruginosa PAO1), but does not respond to nonpathogenic Escherichia coli DH5α. This concept is based on the generalization that a majority of pathogenic bacteria secrete virulence factors such as toxins and lipases that actively damage cell membranes, typically observed as tissue damage around infected wounds, while nonpathogenic bacteria do not (or not at high concentration). The eventual aim of this work is to produce responsive dressings which release antimicrobials and change color only on infected wounds. This paper details preliminary approaches to achieving this goal, including vesicle−bacteria studies in aqueous suspension, and fluorescence imaging of fluorescein containing vesicles lysed by S. aureus and P. aeruginosa, but not by E. coli.
Streptococcus agalactiae, (Group B Streptococcus (GBS)), is a common colonizer of the female vagina. In women giving birth it can be transmitted to the baby and cause serious illness and even death ...to the child. We have developed a biosensor comprising of phospholipids and fatty acids vesicles encapsulating high concentration, self-quenched carboxyfluorescein, which is released by the lysis of the vesicle by virulence factors expressed by GBS, becoming diluted and fluorescent. The microbial specificity of the sensor was tested against a number of GBS strains and other microbes including Candida albicans, Enterococcus faecalis and Staphylococcus epidermidis and a statistically significant response to GBS measured over these other microbes. To test the invivo efficacy of the biosensor, a pilot study using donated lower vaginal swabs from non-pregnant women was conducted, where 58 female adults were recruited. Participants donated two swabs, one which was used for the vesicle test and one for the ‘gold standard’, enriched culture media (ECM) test. An overall GBS carriage rate of 17.2% was measured using the ECM test. The vesicle biosensor test took 45 min to obtain a result, and showed a sensitivity of 83.3%, specificity of 85.7% and accuracy of 85.3%. The test accuracy is in line with current novel GBS identification tests, with the advantage of being rapid, easy to use, low-cost and able to be conducted by bedside during start of labour.
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•Group B Streptococcus (GBS) cause the majority of neonatal infections globally.•Current detection methods are time consuming and cannot be done at bedside.•Phospholipid vesicles encapsulating a self-quenched dye can detect GBS virulence factors.•Phospholipid vesicles detect GBS colonisation in <1 hour and could be used at bedside.
Here, a reaction-based indicator displacement hydrogel assay (RIA) was developed for the detection of hydrogen peroxide (H
2
O
2
)
via
the oxidative release of the optical reporter Alizarin Red S ...(ARS). In the presence of H
2
O
2
, the RIA system displayed potent biofilm inhibition for Methicillin-resistant
Staphylococcus aureus
(MRSA), as shown through an
in vitro
assay quantifying antimicrobial efficacy. This work demonstrated the potential of H
2
O
2
-responsive hydrogels containing a covalently bound diol-based drug for controlled drug release.
Here, a reaction-based indicator displacement hydrogel assay (RIA) was developed for the detection of hydrogen peroxide (H
2
O
2
)
via
the oxidative release of the optical reporter Alizarin Red S (ARS).
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