Cloud point (CP)/lower consolute temperature (LCT) of aqueous mixture of TX-100 and a highly recognised anti-diabetic drug metformin hydrochloride (MNH) was analysed in absence/presence of NH
4
Cl, ...NH
4
NO
3
, (NH
4
)
2
SO
4
and (NH
4
)
2
HPO
4
. The CP values were found to be decreased with increasing concentrations of ammonium salts. Occurrence of aggregation in respective solution systems might result in declining of corresponding CP. Thermodynamic parameters (
,
and
) were calculated at CP. The appearance of positive values of Gibbs free energy (
) indicates that clouding in the studied system was thermodynamically non-spontaneous and the degree of non-spontaneity was diminished with increasing in the extents of electrolytes. The computed enthalpy (
) and entropy (
) values of the system showed negative values in cases of aq. NH
4
Cl, (NH
4
)
2
SO
4
and (NH
4
)
2
HPO
4
while the negative values tend to reduce with rise of electrolytes content. In case of aq. NH
4
NO
3
medium, the reverse results for the
and
values were detected. The
and
values in the studied system indicate the presence of electrostatic interaction between TX-100 and MNH in NH
4
Cl, (NH
4
)
2
SO
4
, (NH
4
)
2
HPO
4
media whereas the hydrophobic interactivity might play a great role within the mixture when it was placed in the NH
4
NO
3
solution.
Controlling and monitoring the residual activity of quaternary ammonium compounds (QACs) are critical for maintaining safe yet effective levels of these agents in the environment. This study ...investigates the utility of bromophenol blue (BPB) as a safe, rapid and user‐friendly indicator to detect in situ residual QACs dried on hard, non‐porous surfaces, as well a means to assess their antimicrobial efficacy. At pH 7, BPB has a purple colour which turns blue upon its complexation with QACs such as didecyldimethylammonium chloride (DDAC). BPB itself has no antimicrobial properties up to 400 ppm. Within the range of 0–400 ppm, BPB colour change was tied to specific DDAC antimicrobial performances with a detection threshold of 100 ppm. BPB concentration and application volume could be adjusted such that a colour shift from purple to blue correlated with a set percent reduction (>99·9%) in test bacteria (Staphylococcus aureus and Klebsiella aerogenes). The BPB solutions developed in this study yielded similar colour shifts on polycarbonate and stainless steel surfaces and did not cross‐react with chemical ingredients commonly found in sanitizers and disinfectant products. Overall, this study suggests that BPB provides a simple solution to safely monitor the post‐application level and biocidal activity of residual dried QACs on surfaces.
Significance and Impact of the Study: Excessive use of antimicrobial quaternary ammonium compounds (QACs) can have adverse effects on health and ecosystems. Compatible with chemicals commonly used in sanitizers, non‐toxic bromophenol blue (BPB) was used to detect residual amounts of QACs such as didecyldimethylammonium chloride (DDAC) on hard non‐porous surfaces. Once deposited, BPB solutions turn from purple to blue upon complexation with DDAC in a quantitative, stoichiometric fashion. The colour shift is linked to a 99·9% reduction in bacteria for both Staphylococcus aureus and Klebsiella aerogenes. Thus, BPB provides a simple solution to safely monitor the post‐application level and biocidal activity of dried QACs on surfaces.
Biofilms formed on food contact surfaces are frequently exposed to disinfectants at different concentrations. This study was designed to evaluate how S. Enteritidis in single species and dual species ...biofilms with P. fluorescens respond to quaternary ammonium compounds (QAC) residues on food contact surfaces. The 48 h-biofilms of S. Enteritidis and P. fluorescens in single/dual species were continuously exposed to 20 ppm QAC for 5 days, followed by QAC challenge at 200 ppm and 100 ppm for attached and detached cells, respectively. Biofilm structures were observed by confocal laser scanning microscopy (CLSM) and extracellular polymeric substances (EPS)-related gene expression was also evaluated. Results showed that QAC stress led to one log lower cell counts of S. Enteritidis and P. fluorescens single species biofilms. More cellulose observed by CLSM images and increased transcript levels of cellulose-related genes (csgD, bcsA and ardA) of S. Enteritidis were induced by QAC stress. Nevertheless, high percentage of membrane damaged cells in QAC pre-exposed biofilms might contribute to the increased sensitivity of S. Enteritidis in both attached and detached cells. Previous QAC exposure did not influence S. Enteritidis viable cell counts in dual specie biofilms, in which S. Enteritidis showed strong resistance to QAC with <2 log CFU/cm2 reductions. Decreased transcript levels of cellulose-related genes were observed of S. Enteritidis in dual species biofilms, but EPS-related gene expression of P. fluorescens was not affected by single/duals species. The dual species biofilm matrix which has big microcolonies extruding from bottom layers with great amounts of polysaccharides mainly produced by P. fluorescens could possibly protect S. Enteritidis against disinfection. Enhanced survival of S. Enteritidis in dual species biofilms was also found when they were detached from the coupons. Overall, our findings highlight that although repeated exposures to low dose of QAC sensitized S. Enteritidis, the presence of P. fluorescens in dual species biofilms could enhance QAC resistance of S. Enteritidis, probably contributing to survival of S. Enteritidis in food processing plants.
•QAC stress increased sensitivity of S. Enteritidis attached and detached cells.•QAC stress could induce cellulose production in S. Enteritidis biofilms.•QAC stress upregulated expression levels of csgD, adrA, and bcsA.•Co-culture with P. fluorescens enhanced survival of S. Enteritidis exposed to QAC.•S. Enteritidis and P. fluorescens dual species biofilms showed complex structures.
Airborne and ground-based measurements of aerosol concentrations, chemical
composition, and gas-phase precursors were obtained in three valleys in
northern Utah (USA). The measurements were part of ...the Utah Winter Fine
Particulate Study (UWFPS) that took place in January–February 2017. Total
aerosol mass concentrations of PM1 were measured from a Twin Otter
aircraft, with an aerosol mass spectrometer (AMS). PM1 concentrations
ranged from less than 2 µg m−3 during clean periods to over
100 µg m−3 during the most polluted episodes, consistent with
PM2.5 total mass concentrations measured concurrently at ground
sites. Across the entire region, increases in total aerosol mass above
∼2 µg m−3 were associated with increases in the
ammonium nitrate mass fraction, clearly indicating that the highest aerosol
mass loadings in the region were predominantly attributable to an increase in
ammonium nitrate. The chemical composition was regionally homogenous for
total aerosol mass concentrations above 17.5 µg m−3, with 74±5 % (average ± standard deviation) ammonium nitrate, 18±3 %
organic material, 6±3 % ammonium sulfate, and 2±2 %
ammonium chloride. Vertical profiles of aerosol mass and volume in the region
showed variable concentrations with height in the polluted boundary layer.
Higher average mass concentrations were observed within the first few hundred
meters above ground level in all three valleys during pollution episodes. Gas-phase measurements of nitric acid (HNO3) and ammonia (NH3) during
the pollution episodes revealed that in the Cache and Utah valleys, partitioning
of inorganic semi-volatiles to the aerosol phase was usually limited by the
amount of gas-phase nitric acid, with NH3 being in excess. The inorganic
species were compared with the ISORROPIA thermodynamic model. Total inorganic
aerosol mass concentrations were calculated for various decreases in total
nitrate and total ammonium. For pollution episodes, our simulations of a
50 % decrease in total nitrate lead to a 46±3 % decrease in total
PM1 mass. A simulated 50 % decrease in total ammonium leads to a
36±17 % µg m−3 decrease in total PM1 mass, over the entire
area of the study. Despite some differences among locations, our
results showed a higher sensitivity to decreasing nitric acid concentrations
and the importance of ammonia at the lowest total nitrate conditions. In the
Salt Lake Valley, both HNO3 and NH3 concentrations controlled
aerosol formation.
Quaternary ammonium salts (QAS), as the surface active compounds, are widely used in medicine and industry. Their common application is responsible for the development of microbial resistance to QAS. ...To overcome, this issue novel surfactants, including gemini-type ones, were developed. These unique compounds are built of two hydrophilic and two hydrophobic parts. The double-head double-tail type of structure enhances their physicochemical properties (like surface activity) and biological activity and makes them a potential candidate for new drugs and disinfectants. Antimicrobial activity is mainly attributed to the biocidal action towards bacteria and fungi in their planktonic and biofilm forms, but the mode of action of gemini QAS is not yet fully understood. Moreover, gemini surfactants are of particular interest towards their application as gene carriers. Cationic charge of gemini QAS and their ability to form liposomes facilitate DNA compaction and transfection of the target cells. Multifunctional nature of gemini QAS is the reason of the long-standing research on mainly their structure-activity relationship.
The overuse of antibiotics has led to the emergence of a large number of antibiotic-resistant genes in bacteria, and increasing evidence indicates that a fungicide with an antibacterial mechanism ...different from that of antibiotics is needed. Quaternary ammonium salts (QASs) are a biparental substance with good antibacterial properties that kills bacteria through simple electrostatic adsorption and insertion into cell membranes/altering of cell membrane permeability. Therefore, the probability of bacteria developing drug resistance is greatly reduced. In this review, we focus on the synthesis and application of single-chain QASs, double-chain QASs, heterocyclic QASs, and gemini QASs (GQASs). Some possible structure–function relationships of QASs are also summarized. As such, we hope this review will provide insight for researchers to explore more applications of QASs in the field of antimicrobials with the aim of developing systems for clinical applications.
The development of organic polymer materials for disinfection and sterilization is thought of as one of the most promising avenues to solve the growth and spread of harmful microorganisms. Here, a ...series of linear polyisocyanide quaternary ammonium salts (L-PQASs) with different structures and chain lengths were designed and synthesized by polymerization of phenyl isocyanide monomer containing a 4-chloro-1-butyl side chain followed by quaternary amination salinization. The resultant compounds were characterized by
H NMR and FT-IR. The antibacterial activity of L-PQASs with different structures and chain lengths against
(
and
(
was evaluated by determining the minimum inhibitory concentrations (MICs). The L-POcQAS-M
has the strongest antimicrobial activity with MICs of 27 μg/mL against
and 32 μg/mL against
When the L-PQASs had the same polymerization degree, the order of the antibacterial activity of the L-PQASs was L-POcQAS-M
> L-PBuQAS-M
> L-PBnQAS-M
> L-PDBQAS-M
(linear, polyisocyanide quaternary ammonium salt, monomer,
= 50,100). However, when L-PQASs had the same side chain, the antibacterial activity reduced with the increase of the molecular weight of the main chain. These results demonstrated that the antibacterial activity of L-PQASs was dependent on the structure of the main chain and the length of the side chain. In addition, we also found that the L-POcQAS-M
had a significant killing effect on MK-28 gastric cancer cells.
Cationic surfactants have a strong affinity to sorb to phospholipid membranes and thus possess an inherent potential to bioaccumulate, but there are few measurements of bioconcentration in fish. We ...measured the bioconcentration of 10 alkylamines plus two quaternary ammonium compounds in juvenile rainbow trout at pH 7.6, and repeated the measurements at pH 6.2 for 6 of these surfactants. The BCF of the amines with chain lengths ≤ C14 was positively correlated with chain length, increasing ∼0.5 log units per carbon. Their BCF was also pH dependent and approximately proportional to the neutral fraction of the amine in the water. The BCFs of the quaternary ammonium compounds showed no pH dependence and were >2 orders of magnitude less than for amines of the same chain length at pH 7.6. This indicates that systemic uptake of permanently charged cationic surfactants is limited. The behavior of the quaternary ammonium compounds and the two C16 amines studied was consistent with previous observations that these surfactants accumulate primarily to the gills and external surfaces of the fish. At pH 7.6 the BCF exceeded 2000 L kg–1 for 4 amines with chains ≥ C13, showing that bioconcentration can be considerable for some longer chained cationic surfactants.
Quaternary ammonium compounds (QACs) comprise a large class of surfactants, consumer products, and disinfectants. The recently-isolated QAC natural product tricepyridinium bromide displays potent ...inhibitory activity against S. aureus but due to its unique structure, its mechanism of action remains unclear. A concise synthetic route to access tricepyridinium analogs was thus designed and four N-alkyl compounds were generated in addition to the natural product. Biological analysis of these compounds revealed that they display remarkable selectivity towards clinically-relevant Gram-positive bacteria exceeding that of commercially-available QACs such as cetylpyridinium chloride (CPC) and benzalkonium chloride (BAC) while having little to no hemolytic activity. Molecular modeling studies revealed that tricepyridinium and shorter-chain N-alkyl analogs may preferentially bind to the QacR transcription factor leading to potential activation of the QAC resistance pathway found in MRSA; however, our newly synthesized analogs are able to overcome this liability.
The demand for vegetable proteins increases globally and seaweeds are considered novel and promising protein sources. However, the tough polysaccharide-rich cell walls and the abundance of ...polyphenols reduce the extractability and digestibility of seaweed proteins. Therefore, food grade, scalable, and environmentally friendly protein extraction techniques are required. To date, little work has been carried out on developing such methods taking into consideration the structural differences between seaweed species. In this work, three different protein extraction methods were applied to three Swedish seaweeds (
Porphyra umbilicalis
,
Ulva lactuca
, and
Saccharina latissima
). These methods included (I) a traditional method using sonication in water and subsequent ammonium sulfate-induced protein precipitation, (II) the pH-shift protein extraction method using alkaline protein solubilization followed by isoelectric precipitation, and (III) the accelerated solvent extraction (ASE®) method where proteins are extracted after pre-removal of lipids and phlorotannins. The highest protein yields were achieved using the pH-shift method applied to
P
.
umbilicalis
(22.6 ± 7.3%) and
S
.
latissima
(25.1 ± 0.9%). The traditional method resulted in the greatest protein yield when applied to
U
.
lactuca
(19.6 ± 0.8%). However, the protein concentration in the produced extracts was highest for all three species using the pH-shift method (71.0 ± 3.7%, 51.2 ± 2.1%, and 40.7 ± 0.5% for
P
.
umbilicalis
,
U
.
lactuca
, and
S
.
latissima
, respectively). In addition, the pH-shift method was found to concentrate the fatty acids in
U
.
lactuca
and
S
.
latissima
by 2.2 and 1.6 times, respectively. The pH-shift method can therefore be considered a promising strategy for producing seaweed protein ingredients for use in food and feed.
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