Sanitization of hydroponic farming facilities in Singapore: what, why, and how.

This study performed microbial analysis of nutrient film technique (NFT) hydroponic systems on three indoor farms in Singapore (the "what"). To justify the necessity of sanitizing hydroponic systems, strong biofilm-forming bacteria were isolated from the facility and investigated for their influence on Salmonella colonization on polyvinyl chloride (PVC) coupons in hydroponic nutrient solutions (the "why"). Finally, sanitization solutions were evaluated with both laboratory-scale and field-scale tests (the "how"). As a result, the microbiome composition in NFT systems was found to be highly farm specific. The strong biofilm formers Corynebacterium tuberculostearicum C2 and Pseudoxanthomonas mexicana C3 were found to facilitate the attachment and colonization of Salmonella on PVC coupons. When forming dual-species biofilms, the presence of C2 and C3 also significantly promoted the growth of Salmonella (P < 0.05). Compared with hydrogen peroxide (H2O2) and sodium percarbonate (SPC), sodium hypochlorite (NaOCl) exhibited superior efficacy in biofilm removal. At 50 ppm, NaOCl reduced the Salmonella Typhimurium, C2, and C3 counts to <1 log CFU/cm2 within 12 h, whereas neither 3% H2O2 nor 1% SPC achieved this effect. In operational hydroponic systems, the concentration of NaOCl needed to achieve biofilm elimination increased to 500 ppm, likely due to the presence of organic matter accumulated during crop cultivation and the greater persistence of naturally formed multispecies biofilms. Sanitization using 500 ppm NaOCl for 12 h did not impede subsequent plant growth, but chlorination byproduct chlorate was detected at high levels in the hydroponic solution and in plants in the sanitized systems without rinsing. IMPORTANCE: This study's significance lies first in its elucidation of the necessity of sanitizing hydroponic farming systems. The microbiome in hydroponic systems, although mostly nonpathogenic, might serve as a hotbed for pathogen colonization and thus pose a risk for food safety. We thus explored sanitization solutions with both laboratory-scale and field-scale tests. Of the three tested sanitizers, NaOCl was the most effective and economical option, whereas one must note the vital importance of rinsing the hydroponic systems after sanitization with NaOCl.

Application of sodium hypochlorite for human norovirus and hepatitis A virus inactivation in groundwater.

In this study, the effect of sodium hypochlorite (10-200 ppm of Cl2) on the inactivation of human norovirus (HuNV) GII.4 and hepatitis A virus (HAV) in groundwater was investigated using propidium monoazide (PMA)/reverse transcription quantitative real-time PCR (RT-qPCR). Initially, 4.00 log10 genome copies/µL of HuNV GII.4 or 5.50 log10 genome copies/µL of HAV were artificially inoculated in groundwater. The titers of HuNV GII.4 and HAV decreased significantly (P < 0.05) with increasing Cl2 concentrations. Groundwater was treated with 10, 30, 50, 100, 150, and 200 ppm of Cl2, and the viable HuNV GII.4 was significantly (P < 0.05) reduced to 3.28 (0.21-log reduction), 3.18 (0.31-log reduction), 3.01 (0.48 log reduction), 2.75 (0.74 log reduction), 2.54 (0.95 log reduction), and 2.34 (1.15 log reduction) log10 genome copies/µL, respectively. The viable HAV was also significantly (P < 0.05) reduced to 4.99 (0.23 log reduction), 4.76 (0.46 log reduction), 4.55 (0.67 log reduction), 4.21 (1.01-log reduction), 3.89 (1.33 log reduction), and 3.64 (1.58 log reduction) log10 genome copies/µL, respectively. The decimal reduction times (D values) (1-log10 genome reduction) of HuNV GII.4 and HAV infectivity in groundwater were predicted as 116.7 and 98.9 ppm of Cl2, respectively, using the first-order kinetics model (HuNV GII.4: y = -0.0054x + 3.3585, correlation coefficient (R2) = 0.97; HAV: y = -0.0091x + 5.0470, R2 = 0.97). The result specifically suggests that 150- to 200-ppm Cl2 can potentially be used for the inactivation of >1-log10 genome copy/µL HuNV GII.4 and HAV in groundwater.IMPORTANCEGroundwater represents a vital component of the global water supply, serving as a crucial source of potable water for humans. It serves as a source of potable water for up to 50% of the global population and accounts for 43% of all water used for irrigation. It thus follows that the sustainable management of groundwater represents a pivotal solution. However, the regrowth of pathogens in water that is not treated with chlorine or where proper residual chlorine is not maintained represents a risk to public health.

A novel ratiometric colorimetric sensor for detecting hypochlorite and ascorbic acid based on cascade reaction.

Hypochlorite and ascorbic acid (AA), play an indispensable role in numerous physiological activities. Herein, a ratiometric colorimetric sensing strategy for the determination of hypochlorite and AA was developed via the catalytic oxidation and reduction of 3,3',5,5'-tetramethylbenzidine (TMB). Interestingly, in the presence of Fe3O4-MOF-5(Fe) and hypochlorite, TMB complexes in acidic environments were oxidized to blue oxidized TMB and further diazotized to produce yellow-green diazotized TMB, resulting in the hypochlorite concentration-dependent ratiometric variation for the absorbance at 652 and 450 nm (A450/A652). Moreover, the diazotized TMB was restored to colorless TMB due to the reducibility of AA, and the detection limit of hypochlorite and AA were 0.027 and 0.677 µM, respectively. The ratiometric colorimetric sensing platform offered higher sensitivity and better selectivity because of the specific hypochlorite-induced reaction and the excellent peroxidase-like activity of Fe3O4-MOF-5(Fe). The proposed novel strategy provided the guidance to develop sensors for successive detection of hypochlorite and AA in complicated samples.

Efficacy of Disinfectants for Monkeypox Virus Inactivation on High Touch Surface Materials in Low-Resource Settings.

Disinfection efficacy tests were conducted on surface carriers inoculated with the monkeypox virus (MPXV) by applying six disinfectant solutions (and three controls) on six surfaces common in low-resource settings: four nonporous surfaces (stainless steel, glass, plastic, and latex) and two porous surfaces (ceramic and wood). Disinfectants were wiped on carriers in triplicate, with a 1 min contact time: 0.05 and 0.5% sodium hypochlorite, 70% ethanol, two quaternary ammonium compound (QAC)-based disinfectants, and 1.4% hydrogen peroxide. MPXV was then quantified, and log10 removal values were calculated. Sodium hypochlorite (0.05 and 0.5%) and ethanol (70%) removed MPXV to below detection level, ≥ 99.97% reduction for nonporous surfaces, and ≥99.40% for wood, QAC-based disinfectants were efficacious on nonporous surfaces (≥99.97% inactivation) but had diminished efficacy on wood, a porous surface, and 1.4% H2O2 had limited efficacy across all tested surfaces. Results varied by disinfectant type and surface type. Based on our results, we recommend using 0.05% sodium hypochlorite or 70% ethanol with 1 min contact time to inactive MPXV on clean nonporous and porous surfaces. As MPXV is evolving, future research with additional disinfectants, application methods, and environmental conditions and research to understand adsorption, disinfection efficacy, and transmission risk on porous surfaces are needed to develop practical disinfection recommendations.

Glutathione Modified silicon-doped Carbon Quantum dots as a Sensitive Fluorescent Probe for ClO- Detection.

A selective and sensitive fluorescence method for hypochlorite (ClO-) was designed using glutathione (GSH) modified silicon-doped carbon quantum dots (GSH@Si-CDs). Then a dual emission ratio fluorescence probe (RF-probe) was obtained based on carbodiimide-activated coupling reaction between GSH and Si-CDs. i.e., when the excitation wavelength was kept at 360 nm, the GSH@Si-CDs exhibited strong blue and weak yellow fluorescence at 430 and 580 nm. Meanwhile, the fluorescence of GSH@Si-CDs could be selectively quenched at 430 nm and enhanced at 580 nm in the presence of ClO-, and corresponding limit of detection (LOD) and linear range were measured to be 0.35 µM and 1.0-33.3 µM. The sensing mechanism of the system was also investigated in detail. Moreover, the RF-probe with good accuracy was successfully employed to monitor ClO- in real samples with satisfactory results compared to the standard iodometric method.

A New Fluorene-Based Fluorescent Probe for Recognition of Hypochlorite Ions and its Applications.

Oxidative stress is a trigger for many diseases and occurs with the unstable hypochlorite (ClO-), known as one of the reactive oxygen species (ROS) in organisms. Then, HOCI is acknowledged as an oxidizing species that eliminates a variety of environmental pollutants. Hence, the development of novel methodologies for the selective and precise identification of HOCl/ ClO- is considered to be of utmost importance. In this study, the design, characterization, and applications of a fluorene-based fluorescent probe (FHBP) dependent on the ESIPT mechanism with a "turn-on" response for the sensitive/selective determination of ClO- against other competing samples were reported. The experimental results indicated that the detection limit for ClO-could be quantitatively determined by the probe to be 8.2 × 10-7 M. The binding constant of the probe FHBP with ClO- was computed as 9.75 × 103 M-1. In addition, the response time of FHBP was appointed to be 30 s, indicating a rapid reaction with ClO-. It has also been demonstrated that this probe can be successfully used for the detection of ClO- on filter papers, TLC sheets, cotton swabs, and real samples.

An intramolecular charge transfer based fluorescent probe for imaging of OCl.

The discovery and utilization of new fluorescent chromophore is indispensable to exploit high performance probes for biological research. Stokes shift is one of the most important properties of chromophore accounting for super-resolution fluorescence imaging. Intramolecular charge transfer (ICT) is one of the fundamental mechanisms for fluorescence that accompanied by large Stokes shifts. Based on the conformational changes between ground and excited states, ICT models can be divided into two types: conformation-steady ICT, whose conformation remains unchanged, and conformation-changeable ICT, which is characterized by the rotation of the chromophore around an axis upon excitation. Herein, we report a new chromophore whose donor and acceptor parts took a butterfly geometry with a dihedral angle of 21° in ground state and a planar conformation upon photo excitation. The bent conformation might be ascribed to the extra conjugated double bond, which made the coplanarity of the chromophore in ground state get worse. The chromophore shows a remarkable Stokes shift over 150 nm and a high fluorescence quantum yieldof 0.62. The limit of detection is 41 nM, which enabled the imaging of basal as well as induced OCl- in different cells. Moreover, the pronounced spectroscopic properties ensure the in vivo monitoring of OCl- in arthritic mice. This finding would shed light on the exploitation of small molecule probes based on new fluorescence chromophore for precise biological imaging.

Bactericidal Efficacy of So-Called Sanitizers in Japan.

Commercially available so-called sanitizers in Japan are often touted as having remarkable "sanitizing (jokin)" effect, "virus-removal" capabilities, and "99.99%" removal rate of microbes and pathogens. In this study, we investigated the bactericidal efficacy of these so-called sanitizers for environmental surfaces against Enterococcus faecalis and Pseudomonas aeruginosa. Of note, out of 43 products, 24 (55.8%) did not exhibit bactericidal effects on either Enterococcus or Pseudomonas. Among these 43 products, there were no bactericidal effects in 9 (47.4%) of 19 products that stated as containing "alcohol" as the formula; as well as 4 (80%) of 5 products stating only "benzalkonium chloride"; similarly no effect in 5 (83.3%) of 6 stating only"chlorine chemicals." Furthermore, 6 (46.2%) of 13 products that stated components other than alcohol, benzalkonium chloride, and chlorine chemicals on the product container or with no description of constituent components failed to show any bactericidal effects. Four disinfectants (alcohol for disinfection, 0.1% benzalkonium chloride, 0.05% (500 ppm) hypochlorite, 0.1% (1000 ppm) hypochlorite) as control showed bactericidal effect. The lack of bactericidal activity in nearly half of sanitizers may be explained by the low concentration of the effective ingredient such as alcohol, benzalkonium chloride, and hypochlorite. In sanitizers containing hypochlorite, degradation of hypochlorite with prolongation of time after manufacturing may be another reason.

Genetic determinants of increased sodium hypochlorite and ciprofloxacin susceptibility in Pseudomonas aeruginosa PA14 biofilms.

Reactive chlorine species (RCS) like sodium hypochlorite (NaOCl) are potent oxidizing agents and widely used biocides in surface disinfection, water treatment, and biofilm elimination. Moreover, RCS are also produced by the human immune system to kill invading pathogens. However, bacteria have developed mechanisms to survive the damage caused by RCS. Using the comprehensive Pseudomonas aeruginosa PA14 transposon mutant library in a genetic screen, we identified a total of 28 P. aeruginosa PA14 mutants whose biofilms showed increased susceptibility to NaOCl in comparison to PA14 WT biofilms. Of these, ten PA14 mutants with a disrupted apaH, PA0793, acsA, PA1506, PA1547, PA3728, yajC, queA, PA3869, or PA14_32840 gene presented a 4-fold increase in NaOCl susceptibility compared to wild-type biofilms. While none of these mutants showed a defect in biofilm formation or attenuated susceptibility of biofilms toward the oxidant hydrogen peroxide (H2O2), all but PA14_32840 also exhibited a 2-4-fold increase in susceptibility toward the antibiotic ciprofloxacin. Further analyses revealed attenuated levels of intracellular ROS and catalase activity only for the apaH and PA1547 mutant, providing insights into the oxidative stress response in P. aeruginosa biofilms. The findings of this paper highlight the complexity of biofilm resistance and the intricate interplay between different mechanisms to survive oxidative stress. Understanding resistance strategies adopted by biofilms is crucial for developing more effective ways to fight resistant bacteria, ultimately contributing to better management of bacterial growth and resistance in clinical and environmental settings.

Antimicrobial efficacy of chitosan versus sodium hypochlorite: A systematic review and meta-analysis.

AIM: This meta-analysis aimed to compare the antibacterial efficacy of chitosan/chitosan nanoparticles (Ch/Ch-NPs) versus sodium hypochlorite/chlorhexidine (NaOCl/CHX). MATERIALS AND METHODS: A search was performed in four electronic databases until December 08, 2023. Studies with missing, unclear, and insufficient data sets were excluded. The included studies were assessed by two independent reviewers using the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies. The meta-analysis of standardized mean difference was performed using a random effects model. Additionally, funnel plots as well as Egger's regression intercept test were used to evaluate potential publication bias. RESULTS: A total of 426 samples were used in nine included studies. There was no difference in antibacterial efficacy between Ch/Ch-NPs-NaOCl (SMD: 0.005; 95% CI: -0.844-0.854; p = 0.990). However, the antibacterial efficacy of NaOCl was statistically more effective than Ch/Ch-NPs (SMD: 0.807; 95% CI: 0.015-1.599; p = 0.046) using the bacterial culture method, and Ch/Ch-NPs was statistically higher than NaOCl (SMD: -1.827; 95% CI: -2.720, -0.934; p < 0.000) using confocal laser scanning microscopy. CONCLUSIONS: Ch/Ch-NPs may be an alternative to NaOCl against Enterococcus faecalis. The methods used in the in vitro studies evaluating the antibacterial efficacy of irrigation solutions against E. faecalis may have had an impact on the results.

Calcium hypochlorite cytotoxicity mechanism in fibroblasts and effect on osteoblast mineralization.

AIM: To determine the cytotoxicity mechanism of 2.5% calcium hypochlorite [Ca(OCl)2 ] in L929 fibroblasts and the effect of this solution on human osteoblast-like cells (Saos-2) mineralization, compared to that of 2.5% sodium hypochlorite (NaOCl). METHODOLOGY: L929 fibroblasts were exposed to Ca(OCl)2 and NaOCl at different dilutions for 10 min. Cell metabolism was assessed by methyl-thiazole-tetrazolium (MTT); lysosome integrity, by neutral red (NR) assay; type of cell death, by flow cytometry (apoptosis/necrosis); cytoskeleton, by actin and α-tubulin fluorescence and cell ultrastructure, by transmission electron microscopy (TEM). The alkaline phosphatase (ALP) activity and mineralized nodule formation were determined in Saos-2 by thymolphthalein release and alizarin red staining (ARS), respectively. The data were analysed by two-way anova and Bonferroni's post-test (α = .05). RESULTS: Ca(OCl)2 promoted higher cell viability and a lower percentage of apoptosis and necrosis than NaOCl (p < .05). Ca(OCl)2 and NaOCl decreased cell metabolism and lysosome integrity, induced the breakdown of microtubules and actin filaments, promoted alterations of rough endoplasmic reticulum and disruption of mitochondrial cristae. Additionally, Ca(OCl)2 did not induce ALP activity and had no effect on mineralized nodules formation. CONCLUSIONS: Although Ca(OCl)2 and NaOCl promoted the same cytotoxicity mechanism, Ca(OCl)2 was less cytotoxic than NaOCl. As for ALP activity, no differences were observed between NaOCl and Ca(OCl)2 . The production of mineralized nodules induced by Ca(OCl)2 was lower than those induced by NaOCl, but was not different from those induced by the control group.

Impact of root canal disinfection on the bacteriome present in primary endodontic infection: A next generation sequencing study.

AIM: To investigate the bacteriome present in teeth with primary endodontic infection (PEI) and apical periodontitis (AP) and to determine quantitatively and qualitatively the impact of chemomechanical preparation (CMP) using 2.5% sodium hypochlorite NAOCl on the bacteriome found in PEI with AP using the Illumina MiSeq platform. METHODOLOGY: Thirty-six paired samples from 18 patients were successfully sequenced and analysed. Samples were collected at two sampling times: before (s1) and after (s2) CMP using 2.5% NaOCl. The DNA was extracted from s1 and s2 samples and quantified using quantitative PCR (qPCR). All 36 samples were sequenced using the Illumina MiSeq platform. Raw V3-V4 amplicon sequencing data were processed with the DADA2 pipeline to generate amplicon sequence variants (ASVs). Alpha diversity metrics representing abundance (Chao1) and diversity and evenness (Shannon, Simpson) were computed. The paired-sample Wilcoxon's test was used to compare alpha diversity metrics and qPCR counts between s1 and s2. The PERMANOVA method (with 999 permutations) was applied to compare community composition between sample types (s1 versus s2) and between patient IDs. ALDEx2 (ANOVA-like differential expression tool for high-throughput sequencing data) to investigate differentially abundant taxa between s1 and s2. A paired-sample Wilcoxon's test was used to compare alpha diversity metrics and qPCR counts between s1 and s2. RESULTS: The qPCR counts were significantly higher in s1 compared to s2 (p = .0007). The Chao1 index indicated no difference in alpha diversity (p < .7019); whereas Shannon (p = .0056) and Simpson (p = .02685) indexes showed higher values in s2. The PERMANOVA test using Adonis2 showed a significant effect of sample time on community composition (R2 = .0630, p = .012). Patient ID also showed a significant effect on community composition (R2 = .6961, p = .001). At the genus level, Dialister, Mogibacterium, Prevotella, and Olsenella were differentially enriched at s1, while Actinomyces, Stenotrophomonas_unclassified, Enterococcus_unclassified, and Actinomyces_unclassified were differentially enriched in s2. CONCLUSION: The bacteriome present in teeth with PEI with AP is complex and diverse. CMP using 2.5% NaOCl showed a high quantitatively and qualitatively disinfectant impact on the bacteriome present in PEI with AP.

Radiographic outcome of endodontic treatment and retreatment of teeth with apical periodontitis using two different root canal irrigants. A prospective cohort study.

AIM: The aim of this prospective cohort study was to compare the radiographic outcome of endodontic treatment and retreatment of teeth with apical periodontitis using either 1% sodium hypochlorite (NaOCl) or 2% chlorhexidine digluconate (CHX) for root canal irrigation. MATERIALS AND METHODS: In the years from 2013 to 2015 standard irrigation varied by semester between NaOCl and CHX at the Department of Endodontics at the Faculty of Dentistry. During that time, 912 teeth received treatment for apical periodontitis in 744 patients, of whom 532 responded to the request for a 1-year follow-up. Only one tooth per person (the most distally located) were included; 285 teeth treated with NaOCl and 247 with CHX. One hundred cases were then randomly sampled from each irrigation group and analysed for outcome by periapical index (PAI) scoring using criteria for success, uncertain and failure. Clinical and other radiographic parameters were scored or recorded and analysed for associations with radiographic outcome using chi-square, ANOVA and regression analyses. RESULTS: Success rates (PAI score 1 or 2 at control) were nearly identical for the two irrigation liquids. The use of irrigating solution also did not significantly influence the outcome in chi-square analyses of subgroups of teeth or regression analyses with other variables included. Ordinal regression analysis established that preoperative lesion size or preoperative PAI score were significantly associated with outcome, and teeth in the mandible had significantly better outcomes than in the maxilla. CONCLUSIONS: No significant differences in the radiographic outcome using either 1% NaOCl or 2% CHX as irrigants were found. The outcome was better for teeth with small lesions or lower PAI scores at completion of treatment and for mandibular teeth.

The use of 0.5% or 3% NaOCl for irrigation during root canal treatment results in similar clinical outcome: A 6-year follow-up of a quasi-randomized clinical trial.

AIM: To evaluate the 6-year outcome of root canal treatment irrigated with 0.5% or 3% sodium hypochlorite (NaOCl). METHODOLOGY: The baseline trial was designed as a quasi-randomized clinical trial. Patients referred for root canal treatment to an endodontic specialist clinic were recruited to the study (n = 298). The concentration of NaOCl was allocated quasi-randomized to 271 subjects (0.5% [n = 139], 3% [n = 132]). Bacterial sampling was performed immediately before root canal filling. Samples were cultured and evaluated as growth or no growth. Patients were invited to a clinical and radiological follow-up >5 years postoperatively. The clinical outcome measurements were tooth survival, cumulative incidence of endodontic retreatments, patients' assessment of pain, clinical findings and radiological signs of apical periodontitis (AP). RESULTS: Tooth survival was 85.6% in the 0.5% NaOCl group and 81.1% in the 3% NaOCl group (p = .45). There was no record of retreatment in 94.4% in the 0.5% NaOCl group and in 92.2% in the 3% NaOCl group (p = .76). The percentage of asymptomatic cases were 87.8% in the 0.5% group and 85.3% in the 3% NaOCl group (p = .81). Absence of clinical signs of AP was seen in 86.6% in the 0.5% NaOCl group and in 83.6% in the 3% NaOCl group (p = .80). Absence of radiological signs of AP was seen in 74.0% in the 0.5% NaOCl group and 64.1% in the 3% NaOCl group (p = .20). Subjects with positive culture before root filling reported subjective pain with a significantly higher frequency as compared to negative-culture subjects (p = .014). CONCLUSIONS: The use of 0.5% or 3% NaOCl for irrigation during root canal treatment resulted in similar clinical outcomes 5-7 years postoperatively. Persisting bacteria immediately before root filling may predict future episodes of subjective pain.

Experimental appraisal and numerical modelling of chlorine demand and decay in a typical drinking water distribution network in South Africa.

Safe drinking water requires sound monitoring and maintenance of residual chlorine within drinking water distribution networks (DWDNs) to suppress possible microbial regrowth. However, in the developing world, DWDNs face unique challenges, including aging infrastructure, water pipes laid near or even aboveground thus exposing water to high temperature fluctuations, and relatively high organic loads. Therefore, safely maintaining sustainable residual chlorine levels and restricting the problems of hazardous disinfection by-products (DBPs) formation and of antimicrobial resistance (AMR), both tracing back to extensive chlorination, is a difficult exercise in those settings. Here, the temperature dependent bulk chlorine decay, i.e., the rate at which chlorine residual is consumed, was estimated for a typical DWDN system in South Africa. To this end, experimental assays were performed and a mathematical model was developed to predict chlorine levels within the DWDN under study. A direct relationship (R2 = 0.99) between bulk chlorine decay and initial chlorine dosage was identified, with bulk chlorine decay following the first-order decay model. The bulk chlorine decay rate coefficient (Kb) and the reaction constant with the pipe walls (Kw) were experimentally estimated, with the first being the main chlorine consumer and the latter only slightly contributing to chlorine decay. EPANET was used to simulate the chlorine concentrations within the examined DWDN, while residual chlorine concentrations were modelled using COMSOL. The software programs were calibrated and validated using experimental results. The optimum liquid chlorine dosage was 5 mg L-1, and this could maintain residual levels at 0.5 mg L-1 for 3500 min in the water distribution tanks. Yet, the residual chlorine levels at the distal end of the DWDN were below the recommended safety limits, suggesting the need for chlorine booster stations to supplement residual chlorine rather than further increasing chlorine initial dosages which will lead to unsafe chlorine levels at the proximal points and inevitably will increase DBPs in drinking water. This relatively high chlorine dosage reflects the overall poor quality of the raw water that feeds the drinking water treatment plant under study, which is consistent with the poor water quality of surface water in South Africa. Overall, this methodology can be replicated in DWDNs in South Africa and across the developing world, where similar challenges persist and ensure safe drinking water but not at the expense of DBPs formation and possibly AMR spreading.

A ratiometric fluorescent probe for rapid and specific detection of hypochlorite.

Hypochlorite (ClO- ), as a kind of essential reactive oxygen species, plays a crucial role in vitro and in vivo. Here, a ratiometric fluorescent probe (TPAM) was designed and constructed for sensing ClO- based on substituted triphenylamine and malononitrile, which exhibited obvious colour transfer from orange to colourless under daylight accompanied by noticeable fluorescence change from red to green in response to ClO- . TPAM could effectively monitor ClO- with the merits of fast response, excellent selectivity, high sensitivity and a low detection limit of 0.1014 µM. 1 H NMR, mass spectra and theoretical calculations proved that ClO- caused the oxidation of the carbon-carbon double bond in TPAM, resulting in compound 1 and marked changes in colour and fluorescence. In addition, TPAM was utilized for imaging ClO- in living cells successfully with good photostability and biocompatibility.

Synthesis and application of hypochlorite mediated acylhydrazone fluorescence probes.

Hypochlorous acid (HClO/ClO- ) is one of the important reactive oxygen species (ROS). It acts as a second signaling molecule within and between cells and is an indispensable active molecule in living organisms to regulate physiological and pathological processes. In this article, two fluorescent probes (PTF and PTA) for highly selective fluorescent recognition of ClO- were successfully synthesized based on the ICT mechanism by condensing phenothiazines with two hydrazides via the hydrazide structure (). PTF can identify different concentrations of ClO- in two steps. Due to its ClO- two site recognition, the probe exhibited good selectivity (specific recognition of ClO- over a wide concentration range), a fast time response (rapid recognition in seconds), a sufficiently low detection limit (3.6 and 11.0 nM), and large Stokes shifts (180 and 145 nm). Furthermore, the recognition of ClO- by contrasting probes with different substituents exhibited different fluorescence changes of ratiometric type and turn-off. PTF successfully achieves the detection of exogenous and endogenous ClO- in aqueous solution and living cells.

A triphenylamine-based carbohydrazide hydrazone fluorescent probe for selective detection of hypochlorite and sensing acidic gases.

Hypochlorous acid and its hypochlorite are important reactive oxygen species in the body, and are involved in various physiological processes related to immunity; their rapid detection is of great significance. Here, we synthesized a fluorescent probe (TPAS) by condensation of 4-(diphenylamino)benzaldehyde, carbohydrazide, and salicylaldehyde, which can be used for the detection of ClO- in water and sensing of acidic gas in its solid state. The probe showed strong selective recognition of ClO- in acetonitrile and good tolerance to interference ions. There were good linear responses between the intensity of absorbance and fluorescence and the amount of ClO-. The TPAS solid and its paper strips can emit red fluorescence when exposed to volatile acidic vapours. After being treated with NH3, the red fluorescence can be restored to yellow. The response process of TPAS to ClO- and acid gases was characterized using nuclear magnetic resonance, electrospray ionisation mass spectrometry, transmission electron microscopy, and density functional theory calculations. Furthermore, it can be utilized in analyzing ClO- in commercially available bleaching products; the detection results were basically compatible with the labelled values. In addition, the probe is biocompatible and can be applied for imaging ClO- in zebrafish.

Quantitative analysis of CL-20 explosive by smartphone-based chemiluminescence method.

A new smartphone-based chemiluminescence method has been introduced for the quantitative analysis of CL-20 (Hexanitroazaisowuertzitan) explosive. The solvent mixture, oxidizer agent, and concentration of the reactants were optimized using statistical procedures. CL-20 explosive showed a quenching effect on the chemiluminescence intensity of the luminol-NaClO reaction in the solvent mixture of DMSO/H2O. A smartphone was used as a detector to record the light intensity of chemiluminescence reaction as a video file. The recorded video file was converted to an analytical signal as intensity luminescence-time curve by a written code in MATLAB software. Dynamic range and limit of detection of the proposed method were obtained 2.0-240.0 and 1.1 mg⋅L-1, respectively, in optimized concentrations 1.5 × 10-3 mol⋅L-1 luminol and 1.0 × 10-2 mol⋅L-1 NaClO. Precursors TADB, HBIW, and TADNIW in CL-20 explosive synthesis did not show interference in measurement the CL-20 purity. The analysis of CL-20 spiked samples of soil and water indicated the satisfactory ability of the method in the analysis of real samples. The interaction of CL-20 molecules and OCl- ions is due to quench of chemiluminescence reaction of the luminol-NaClO.

Tailoring plasmonic sensing strategies for the rapid and sensitive detection of hypochlorite in swimming water samples.

A tunable plasmonic sensor has been developed by varying the dextran content in the initially synthesized dextran-gold nanoparticle (dAuNPs) solution. A colloidal nanogold solution (dAuNPs-Sol) was initially prepared using dextran and gold salt in alkaline media by a one-pot green synthetic route. The dAuNPs-Sol was combined with varying amounts of dextran (ranging from 0.01 to 30.01%) to create a tunable probe, along with different solid formats, including tablet (dAuNPs-Tab), powder (dAuNPs-Powder), and composite (dAuNPs-Comp). Both the liquid and solid phase plasmonic probes were characterized using UV-vis spectroscopy, transmission electron microscopy (TEM) dynamic light scattering (DLS), and zeta potential analysis. The impact of dextran content in the dAuNP solution is studied in terms of surface charge and hydrodynamic size. The influence of operational treatments used to achieve solid dAuNPs probes is also explored. All plasmonic probes were employed to detect a broad range of OCl¯ concentrations (ranging from µM to mM) in water through aggregation followed by calculating a lower and upper limit of detection (LLoD, ULoD) of the proposed colorimetric sensors. Results indicate that the most sensitive detection is achieved with a lower dextran content (0.01%), which exhibits an LLoD of 50 µM. The dAuNPs-Sol sensor is selective and demonstrates real-world applicability, as confirmed by interference analysis and successful testing with various water samples. Additionally, it is found that a 20 × concentration of dextran-coated gold nanoparticles could be attained without any changes in the particle morphology. This concentration is achieved through a straightforward process that does not require the use of a centrifuge machine. This finding highlights the practicality and simplicity of the method, indicating its potential for scalable and cost-effective production of concentrated dAuNPs without compromising their structural integrity.