Dipicolinic Acid Research Articles

Terbium-functionalized silver-based metal-organic frameworks for efficient antibacterial and simultaneous monitoring of bacterial spores

Effective sterilization and timely monitoring of bacterial spores are critical to addressing the safety concerns in the environment. Here, we design and synthesize two silver-based metal-organic frameworks Ag-tpt (Htpt=5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole) and Ag-tmpt (Htmpt=5-(4-((1H-1,2,4-triazol-1-yl)methyl)phenyl)-1H-tetrazole) with excellent antibacterial activity against Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli), respectively. The Ag-tpt with an increased degree of conjugation exhibits high stability and enhanced fluorescence performance. Furthermore, the ratiometric fluorescence probe Tb3+@Ag-tpt is fabricated for detecting dipicolinic acid (DPA) in the aqueous solution, showing quite a competitive detection range (0–65 µM) and a low detection limit (LOD = 24.2 nM). In addition, the Tb3+@Ag-tpt presents a low LOD of bacterial spores (1.9 × 104 spores/mL) and also inherits the excellent antibacterial function against B. subtilis and E. coli, in which the antibacterial circle diameters reached 20.8 ± 0.8 mm and 22.3 ± 0.6 mm, respectively. Therefore, the silver-based composite materials bring broad prospects in the fields of reducing bacterial contamination and detecting bacterial spores in real time.

Hydrothermal Stability and Transport Properties of Optically Detectable Advanced Tracers With Carbonate Rocks in the Presence of Oil

Summary The use of tracer technology to illuminate reservoir characteristics such as well connectivity, volumetric sweep efficiency, and geological heterogeneity for the purpose of improving history-matching fidelity and enriching production optimization algorithms has gained momentum over the last decade. Herein, we report the stringent laboratory qualification of a novel class of fluorescent molecules, optically detectable down to ultratrace levels (<ppb) in produced water, as competent crosswell water tracers for use in highly retentive carbonate reservoirs with harsh salinity and temperature requirements. Tracer molecules, with state-of-the-art fluorobenzoic acids (FBAs) as a benchmark, exhibiting requisite hydrothermal stability and nonretentive behavior in simulated reservoir conditions coreflood tests are scheduled to be field-trialed. Our novel fluorescent tracer material systems, based on dipicolinic acid (DPA) and naphthalene sulfonates, rely on time-resolved luminescence and/or advanced chromatographic separation to eliminate the interfering fluorescent background issue in produced water for near real-time analysis. We systematically evaluated the novel tracer molecules at 95°C in high-salinity injection brine over 4 months, with periodic sampling and analysis by liquid chromatography to ascertain their hydrothermal stability. Coreflood tests at reservoir conditions were conducted to determine their interactions with carbonate rock surfaces with and without residual crude oil. All qualification tests were performed using a reference water tracer 2-FBA and/or a model partitioning tracer 4-chlorobenzyl alcohol as benchmark. Finally, reservoir simulations were performed to study both nonpartitioning and partitioning tracer transports in realistic field conditions. Hydrothermal stability tests indicated that our novel tracers are stable for 132 days in brine under reservoir conditions. Coreflood tests without residual oil revealed that the novel fluorescent tracer materials, such as FBAs, exhibit negligible retention in carbonate rocks (almost 100% recovery of the tracers). Coreflood experiments with residual oil suggested that all tracer materials, including the FBAs, possibly reversibly interact with the rocks, resulting in lower tracer materials recovery. While the overall retention of tracer materials is minimal in the presence of residual oil, these values were found to be relatively higher to that measured without residual oil. We observed no significant change in core permeability due to tracer injection. Field-scale reservoir simulation sensitivity studies in companion with coreflood experiments indicated minimum interferences for consecutive tracer injections in the field trial settings. We believe this is the first time such direct comparative study has been performed in the existing research to evaluate the interaction of both water and partitioning tracers in carbonate rocks at reservoir conditions with and without the presence of residual crude oil. Reducing the burden of analysis is critical in the implementation of this technology to obtain high-fidelity tracer data that can be used to improve waterflood optimization, increasing hydrocarbon recovery by a few percent per well without using additional resources for drilling or production. The ability to use presently commercialized tracer technologies, such as FBA-based molecules, in conjunction with this novel optically detectable fluorescent tracer platform will be a force multiplier to enable large tracer campaigns that provide high-fidelity tracer data for a production optimization algorithm.

Characterization of a Clostridioides difficile ST-293 isolate from a recurrent infection in Argentina

Clostridioides difficile is an opportunistic spore-forming pathogen responsible for antibiotic-associated diarrhea in humans. C. difficile produces two main toxins: TcdA and TcdB as well as a third toxin named binary toxin (CDT) that is also involved in virulence. The present study aimed at characterizing the C. difficile isolate ALCD3 involved in a relapse episode of nosocomial infection. Molecular characterization showed that isolate ALCD3 belongs to toxinotype 0/v and the MLST analysis demonstrated allelic profile adk:91, atpA:1, dxr:2, glyA: 1, recA:27, sodA: 1 and tpi:1 which corresponds to ST293 (MLST clade: 1). During growth, isolate ALCD3 showed an early increase in the sporulation ratio as well as maximal values of heat resistant forms after 2 days of incubation. Both sporulation kinetics and production of heat resistant forms were faster for isolate ALCD3 than for the reference strain VPI 10463. Germination in the presence of the natural germinant taurocholate was faster for isolate ALCD3 than for strain VPI 10463, which indicates that isolate ALCD3 starts cortex hydrolysis earlier than strain VPI 10463. Furthermore, the co-germinant glycine, induces rapid release of dipicolinic acid (DPA) in isolate ALCD3. These findings indicate that isolate ALCD3 is particularly efficient in both sporulation and germination. The present work represents the first report of the circulation of C. difficile ST293 in Argentina. The ability of isolate ALCD3 to produce toxins and its high sporulation/germination capacity are key features compatible with a microorganism with high dissemination potential and the possibility of inducing recurrent infections.

Red-emissive carbon nanostructure-anchored molecularly imprinted Er-BTC MOF: a biosensor for visual anthrax monitoring.

Investigating effective fluorescence strategies for real-time monitoring of dipicolinic acid (DPA) is of paramount importance in safeguarding human health. Herein, we present the design of a desirable red-emissive carbon nanostructure anchoring a molecularly imprinted Er-BTC MOF as a fluorescence biosensor for the visual determination of DPA. DPA is a biomarker of Bacillus anthracis, a subcategory of serious infectious diseases and bioweapons. We introduce a paper test strip sensitized with the aforementioned nanostructure, which is integrated with online UV excitation and smartphone digital imaging, resulting in a DPA signal-off sensing platform. The proposed fluorometric visual paper-based biosensor demonstrates wide linear ranges for DPA (10-125 μM) with a LOQ and LOD of 4.32 and 1.28 μM, respectively. The designed platform exhibits impressive emission properties and adaptable surface functional groups, which confirm its desirable selective sensing capabilities against other biological molecules and DPA isomers. As a proof of concept, DPA monitoring is successfully applied to real samples of tap water and urine. This integrated selective paper-based nano-biosensor, coupled with smartphone signal recording, holds great promise for state-of-the-art practical applications including fluorometric/colorimetric detection in healthcare and environmental monitoring, food safety analysis, and point-of-care testing.

Термические свойства дипиколиновой кислоты и натриевой соли дипиколиновой кислоты NaH(COO)2C5H3N • H2(COO)2C5H3N • 3H2O

Pyridine-2,6-dicarboxylic acid (dipicolinic acid) are actively studied by scientists. Dicarboxylic acid can be used as a special biomarker of anthrax. The crystal structure of NaH(COO)2C5H3N•H2(COO)2C5H3N•3H2O (1) was redetermined from single crystal. In the structure of the sodium salt of dipicolinic acid, sodium is the central atom having two molecules of dipicolinic acid and three molecules of water as ligands. The dipicolinic anion coordinate sodium cation by both oxygens and one nitrogen atom. A network of hydrogen bonds connects water and dipicolinic acid molecules. Hydrogen bonds take part in the formation of building blocks and arranging them into chains which, in their turn, make up layers. The sodium salt of dipicolinic acid as well as its precursor – dipicolinic acid were studied by IR spectroscopy and simultaneous thermal analysis. According to thermal analysis dipicolinic acid is anhydrous substance, that decompose on melting at 252 °C forming only gaseous products, presumably CO2 and pyridine. Opposite to that, thermolysis of its sodium salt follow much more complicated way. According to thermogram the 1 has first stage of three water molecules removal at 105 °C. The measured mass loss is very close to expected mass loss. Heat of dehydratation reaction is 151 kJ/mole. On a further heating the sodium salt of dipicolinic acid was melted at 256 °C with large mass loss. The nature of products at 268 and 315 °C is hard to state. EDX elemental analysis of black residue after 700 °C state brutto-formula of “NaNC5O2” – Na cyanate or carbonate in glassy carbon matrix.

A highly stable chain-based EuIII metal-organic framework as a turn-on and blue-shift luminescent sensor for dipicolinic acid.

The development of a rapid and selective method for the identification of dipicolinic acid (DPA), a specific biomarker in Bacillus anthracis spores, is of great importance for the avoidance of anthrax infection. Herein, a chain-based EuIII metal-organic framework with the formula {[Eu3(BTDB)3(μ3-OH)3(H2O)]·solvents}n (JXUST-38, H2BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid) was obtained using 2-fluorobenzoic acid as the pH regulator. JXUST-38 exhibits good chemical and thermal stability and can specifically recognize DPA in N,N-dimethylformamide solution through luminescence enhancement and blue-shift effects with a detection limit of 0.05 μM. Furthermore, the significant luminescence enhancement and blue shift under UV lamps are obviously observable by the naked eye. The luminescence sensing mechanism is attributed to absorbance-induced enhancement between JXUST-38 and DPA. Test paper and mixed-matrix membrane based on JXUST-38 are designed for DPA detection. In addition, the feasibility of using JXUST-38 in biosensing is discussed in detail.

Different patterns of germination inhibition by carvacrol and thymol in Bacillus subtilis spores.

This study aimed to clarify how the phenolic monoterpene carvacrol and its structural isomer thymol both as essential oil components (EOCs) inhibit the germination of Bacillus subtilis spore. Germination was evaluated by the OD600 reduction rate in a growth medium and phosphate buffer containing either l-alanine (l-Ala) system or l-asparagine, d-glucose, d-fructose plus KCl (AGFK) system. The germination of the wild-type spores in the Trypticase Soy broth (TSB) was found to be greatly inhibited by thymol than by carvacrol. Such a difference in the germination inhibition was confirmed by the dipicolinic acid (DPA) release from germinating spores in the AGFK buffer system, but not in the l-Ala system. Similar to the wild-type spores, no difference in the inhibitory activity between the EOCs was also indicated with the gerB, gerK-deletion mutant spores in the l-Ala buffer system and the above substantial difference was also done with the gerA-deleted mutant spores in the AGFK. Fructose was found to release spores from the EOC inhibition and inversely even stimulated. Increased concentrations of glucose and fructose partially suppressed the germination inhibition by carvacrol. The results obtained should contribute to the elucidation of the control effects of these EOCs on bacterial spores in foods.

In the pursuit of a ‘disappearing’ anhydrous phase of the antipyrine–dipicolinic acid (ANT–DPA) co-crystal: explained through relative stability and charge density analyses

The relative stability and growth of the two new cocrystal forms of antipyrine–dipicolinic acid, one of which is the ‘disappearing’ one, were systematically examined.

Effect of pressure-assisted thermal sterilization combining with ε-polylysine on Bacillus subtilis spore proteins, nucleic acids and other intraspore substances

Pressure-assisted thermal sterilization (PATS) is a new technology to inactivate bacterial spores and ensure food safety. Little has been known about the effects of PATS combining with ε-PL on the spore’s nucleic acid, enzymes and other key substances. This study aimed to investigate the inactivation effect of PATS combining with ε-PL on the spores of B. subtilis. The spores were treated with pressure 600 MPa at 25 °C, 65 °C and 75 °C, and ε-PL at 0.1% and 0.3%. After treatment, the survival rate of B. subtilis spores, leakage of nucleic acid and protein, the change in the cell membrane ATPase activity, the leakage of dipicolinic acid, and the damage on protein and nucleic acid of the spores were determined. The results showed that PATS combining with ε-PL inactivated more spores, and significantly increased the release of protein and nucleic acid compared to the control. ATPase activity reached the lowest value after the treatment of 600 MPa/75 °C combining with 0.3% ε-PL. The release of dipicolinic acid from the spores was increased by 600 MPa/75 °C combining with 0.3% ε-PL as compared with 600 MPa/75 °C treatment alone. FTIR analysis showed that a combination of PATS with ε-PL changed the spectral features of B. subtilis functional groups of proteins and nucleic acids. The PATS treatments when combined with ε-PL were found to shift the symmetric and antisymmetric stretching vibrational absorption peaks of phosphodiester group in nucleic acid molecules (P=O). This change suggested that the combined treatment denatured nucleic acid. The combined treatment also changed the protein from an ordered state to a disordered state, and decreased protein stability. The results improved our understanding on the principle of spore inactivation by PATS combining with ε-PL.

Detection of aqueous and gaseous hydrogen sulfide with lanthanide-macrocycle binary complexes.

Two novel, discrete lanthanide-macrocycle binary complexes for the detection of hydrogen sulfide are reported. The hydrogen sulfide sensing mechanism utilises the copper sequestration at a secondary binding site, with resulting bimetallic lanthanide(III)/copper(II) complexes (Ln = Eu3+ and Tb3+) exhibiting high selectivity, good sensitivity and excellent reversibility for aqueous hydrogen sulfide. The inclusion of the DO2A macrocycle and 4-(2-pyridyl)-1,2,3-triazole dipicolinic acid ligand, results in a complex with good solubility and stability. The europium(III) complex also displayed a low limit of detection (665 ppb) with a response time of 30 seconds with gaseous hydrogen sulfide. The improved water solubility and stability over a previous complex results in these sensors having the potential for use in environmental monitoring and biological studies for various functional settings.

Differential sensitization toward lanthanide metal–organic framework for detection of an anthrax biomarker

A novel Tb-doped Eu-based metal-organic framework (Eu-MOF@Tb) has been developed by incorporating hexanuclear europium cluster and 2,2'-bipyridine-5,5'-dicarboxylic acid as well as coordination with Tb(III). Owing to the diverse coordination status of Tb(III) and Eu(III) in MOF, antenna effect emission from Tb(III) can be invoked by dipicolinic acid (DPA), but the luminescence originating from Eu(III) remains unchanged. Taking advantage of this phenomenon, a ratiometric luminescent method for detection of DPA, a biomarker for Bacillus subtilis spores, was developed through differential sensitization toward lanthanide ions. This analysis method allowed for the detection of DPA in the 0.2-10 μM concentration range, with a detection limit of 60nM. It was further validated by spiked recoveries (89.3-110%) of real-world samples with RSD values in the range 3.9-11%. Alongside this, a paper indicator test was prepared for naked-eye detection of DPA via a dose-sensitive color evolution from red to green under UV light. The effectiveness of the proposed approach was explored in the detection of bacterial spores in real biological and environmental samples and indicated great potential for applications as a real-time monitoring system against the anthrax threat.

Fully automated microfluidic mixing aided in-line detection of trace level oil field tracers

Recent development in oil field tracer technologies has been focused on implementations that increase oil recovery through optimized algorithms for production, aided by the addition of high fidelity interwell tracer data that improve reservoir history match. Prerequisites for successful tracer campaigns in oil reservoirs at a large scale not only include low-cost tracer materials with a rich palette of uniquely identifiable tracers, but also high sensitivity, easy-to-use trace-level detection and analysis methodologies. A fully automated in-line separation and detection protocol can simultaneously address challenges in throughput (speed and efficiencies) and accuracy (minimization of error-prone steps) of multi-tracer detection. Our previously reported tracer materials consist of barcoded variants of the dipicolinic acid (DPA) molecules that sensitize the emission of lanthanide ions. We have capitalized on the time-gated optical luminescence detectability of this sensitizer-lanthanide ion complex to reject background oil fluorescence, achieving high detection sensitivity in particularly complex oil field produced brine matrix. However, automation of the detection and analysis process has been hindered by opposing requirements in the integration of chromatography instrumentation (separation resolution) with in-line mixing (dispersion due to increase in residence time), and high sensitivity spectrofluorimetry (long integration time). We overcome this major barrier to implementing an in-line detection design under flow conditions by utilizing a microfluidic mixing chip which offers a high degree of mixing in a very short fluidic path length for the in-flow chelation of lanthanide ion to the chromatographically resolved tracer variants, and a flow-cell fluorescence detector at the output of the high-performance liquid chromatography (HPLC). In this study, we demonstrated the rapid in-line detection of a mixture of three different DPA-based barcoded tracers at ultra-trace level. An automated solid phase extraction (SPE) pre-concentration stage is added to the input of the HPLC, further lowering the detection limit down to a level of 100 pM (pico molar) of tracer molecules. As developed, the complete automated system offers unprecedented sensitivity of detection and accelerated oil field tracer analysis that approaches “near real-time” speed.

Inhibitory effect of licorice extract on the germination and outgrowth of Paraclostridium bifermentans spores.

Paraclostridium bifermentans is responsible for spoilage properties in vacuum-packaged meat. Ordinary heat treatment techniques are ineffective to control the extremely heat-resistant spores of P. bifermentans. Therefore, finding a new strategy to prevent the contamination of P. bifermentans spores in vacuum-packaged meat is challenging. In this study, P. bifermentans was isolated from the vacuum-packaged chicken, and the inhibitory effects of licorice extract on the germination and outgrowth of P. bifermentans spores, as well as the key bioactive components in the licorice extract involved in inhibiting spore activity, were investigated. The spores induced by combination-nutrient-germinant (150 mmol/L L-alanine and 20 mmol/L inosine, co-AI) did not germinate when the concentration of licorice extract was ≥ 3.13 mg/ml. The germination of P. bifermentans spores induced by non-nutrient-germinant (8 mmol/L dipicolinic acid, DPA) was completely prevented by licorice extract at least 1.56 mg/ml. While the outgrowth of P. bifermentans spores was inhibited at a concentration of 0.39 mg/ml. Licorice extract did not seem to damage the non-germinated spores but blocked the germinant sensing. Licorice extract prevented the outgrowing spores from becoming vegetable cells by disrupting the inner membrane. Furthermore, the results obtained from LC-MS data analysis exhibited 15 key bioactive compounds in licorice extract, such as glycyrrhizic acid, liquiritin, etc. Among them, glycyrrhizic acid and liquiritin apioside exerted efficient inhibitory properties on the germination and outgrowth of P. bifermentans spores. This present study demonstrated that licorice extract can be used as a promising inhibitor of spores and provides a new method to control the residual P. bifermentans spores in meat products. Meanwhile, this study exhibits a baseline for the better understanding of the potential application of licorice extracts to control the P. bifermentans spores in meat products.

Preparation of Atorvastatin Calcium-Dipicolinic Acid Multicomponent Solids by Liquid-Assisted Grinding Method to Increase Solubility

Atorvastatin calcium is a cholesterol-lowering drug that is very potent but difficult to dissolve in water, so its bioavailability is low. In this study, atorvastatin calcium-dipicolinic acid multicomponent solids were prepared using the liquid-assisted grinding method to improve atorvastatin calcium's solubility. Characterization of multicomponent solids was carried out using powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Solubility test was carried out by shaking method using distilled water media. The results showed that the particles of atorvastatin calcium - dipicolinic acid multicomponent solids had an irregular shape with rough and porous surface topography. The multicomponent solids have a diffractogram with specific peaks of 2θ at 8.8, 9.9, 11.5, 16.7, 19.1, 21.2, 22.4, 23.4, and 27.7°. The DSC thermogram of multicomponent solids showed a sharp endothermic peak at 181.9 °C (∆H=17.69 J/g), indicating its melting point. The FTIR spectra of atorvastatin calcium-dipicolinic acid multicomponent solids indicated an intermolecular interaction that was thought to be a hydrogen bond between the molecules of atorvastatin calcium and dipicolinic acid. The results of the solubility test showed that the atorvastatin calcium-dipicolinic acid multicomponent solids had a significantly increased solubility (p<0.05) compared to the solubility of pure atorvastatin calcium.

Metabolomic and Lipidomic Profiling of Bacillus Using Two-Dimensional Tandem Mass Spectrometry.

Lipidomic and metabolomic profiles of sporulated and vegetative Bacillus subtilis and Bacillus thuringiensis from irradiated lysates were recorded using a quadrupole ion trap mass spectrometer modified to perform two-dimensional tandem mass spectrometry (2D MS/MS). The 2D MS/MS data domains, acquired using a 1.2 s scan of negative ions generated by nanoelectrospray ionization of microwave irradiated spores, showed the presence of dipicolinic acid (DPA) as well as various lipids. Aside from microwave radiation to extract DPA and lipids from spores, sample preparation was minimal. Characteristic lipid and metabolic profiles were observed using 107─108 cells of the two Bacillus species. Major features of the lipid profiles observed for the vegetative states included sets of phosphatidylglycerol (PG) lipids. Product ion spectra were extracted from the 2D MS/MS data, and they provided structural information on the fatty acid components of the PG lipids. The study demonstrates the flexibility, speed, and informative power of metabolomic and lipidomic fingerprinting for identifying the presence of spore-forming biological agents using 2D MS/MS as a rapid profiling screening method.

Contactless and robust dielectric microspheres-assisted surface-enhanced Raman scattering sensitivity improvement for anthrax biomarker detection.

This report presents a contactless and robust dielectric microspheres (DMs)-assisted surface enhanced Raman scattering (SERS) enhancement method to improve SERS detection sensitivity detection sensitivity. DMs that could focus and collect light were embedded within the polydimethylsiloxane (PDMS) film to avoid direct contact with the analytical solution and improve detection reliability. The as prepared DMs embedded PDMS DMs PD MS film was integrated with a microfluidic technique to enhance the SERS signal of a liquid substrate. Detection in microfluidic systems can reduce reagent consumption, shorten assay time, and avoid evaporation of the colloid substrate solution. The robustness and potential influencing factors of DMs PDMS film assisted SERS enhancement (DERS) were evaluated using 4-aminothiophenol (4-ATP) as the Raman probe. The sensing performance of the proposed method toward dipicolinic acid (DPA) was evaluated, and an evident signal intensification was obtained. Remarkably, the DMs PDMS film can also be implemented on solid substrates. A proof-of-concept experiment was performed by covering the DMs PDMS film directly over an AgNPs@Si solid substrate wherein a 5.7-fold sensitivity improvement was achieved.

Uptake of UVc induced photoproducts of dipicolinic acid by Bacillus subtilis spores - Effects on the germination and UVc resistance of the spores.

Dipicolinic acid (DPA) is a specific molecule of bacterial spores which is essential to their resistance to various stresses such as ultraviolet (UV) exposure and to their germination. DPA has a particular photochemistry that remains imperfectly understood. In particular, due to its ability to absorb UVc radiation, it is likely to form in vitro a wide variety of photoproducts (DPAp) of which only about ten have been recently identified. The photochemical reactions resulting in DPAp, especially those inside the spores, are still poorly understood. Only one of these DPAp, which probably acts as a photosensitizer of DNA upon exposure to UVc, has been identified as having an impact on spores. However, as UVc is required to form DPAp, it is difficult to decouple the overall effect of UVc exposure from the possible effects of DPAp alone. In this study, DPAp were artificially introduced into the spores of the FB122 mutant strain of Bacillus subtilis, one that does not produce DPA. These experiments revealed that some DPAp may play a positive role for the spore. These benefits are visible in an improvement in spore germination rate and kinetics, as well as in an increase in their resistance to UVc exposure.

Dipicolinic Acid-Tb3+/Eu3+ Lanthanide Fluorescence Sensor Array for Rapid and Visual Discrimination of Botanical Origin of Honey.

In the present study, a lanthanide fluorescence sensor array was developed for the discrimination of honey's botanical origin. Dipicolinic acid (DPA) was used as the antenna ligand for sensitizing the fluorescence of Tb3+ and Eu3+ to prepare the DPA-Tb3+/Eu3+ complex. This lanthanide fluorescence sensor showed a cross-reactive response to the major constituents of honey, which led to the result that different classes of honey solution exhibited distinct quenching effects on the fluorescence of the DPA-Tb3+/Eu3+ complex. Furthermore, a fluorescence sensor array composed of ten sensors was constructed by adjusting the pH and the component of the DPA-Tb3+/Eu3+ complex to show multivariate responses towards honey. The visual fluorescence image of the sensor array was recorded by using a smartphone under excitation with portable UV lamp. Results indicated that the pattern of the visual image was related with the botanical origin. After extracting the RGB value of each sensor in 96-well plate, the ratio of R/G was used for principal component analysis (PCA). The results showed that three classes of honey (astragalus, logan, and litchi) were well distinguished. Moreover, the value of principal component 1 (PC1) showed good linearity with the composition of mixing honey and could be used for semi-quantitative analysis. The proposed lanthanide fluorescence sensor array presents a visual and portable method for the discrimination of a honey's origin without the use of analytical instruments, and might provide a novel and simple strategy for the measurement of food origin.

Detection of anthrax biomarker and metallic ions in aqueous media using spherical-shaped lanthanide infinite coordination polymers

We report a lanthanide-based infinite coordination polymer (ICP) system synthesized using pyrazole-3,5-dicarboxylic acid as linker, malonic acid as coordination modulator and water as solvent. The precursors self-assembly into microspherical particles, which are water-stable and exhibit excellent dispersibility. Bimetallic samples based on Tb3+ doped with Eu3+ were investigated as ratiometric dipicolinic acid (DPA) sensors, which is a biomarker for Bacillus anthracis spores. Along with the calibration curves, a detection in a real sample extracted from Bacillus subtilis (model organism) was performed. The samples proved to be highly sensitive and selective for ratiometric DPA detection. In a secondary study, the monometallic sample containing only Tb3+ was also investigated as a sensor for ionic species in aqueous media. The Cr3+, Fe3+, Cu2+, and Cr2O72− ionic species could be detected in water by luminescence quenching mechanism. Therefore, we found that the reported ICP system can be judiciously constructed in order to act as a multimodal probe for several chemical species.

Direct Observation of the Sporicidal Action of Hydrogen Peroxide on Bacillus atrophaeus Spores By Optical Trapping Raman Microscopy

Hydrogen peroxide (H2O2), a strong oxidizer, is frequently used for chemical sterilization in aseptic food processing. Due to their inherent robustness, bacterial spores, i.e. spores of Bacillus atrophaeus, are commonly employed to evaluate the efficacy of the sterilization procedure [1]. Despite its widespread use, however, the details of the sporicidal action of H2O2 are not yet fully understood, with various mechanisms being discussed in the literature [2,3]. Here, we employ optical trapping Raman microscopy to elucidate the sporicidal mechanism of H2O2. Optical trapping Raman microscopy allows us to isolate, investigate, and manipulate individual spores from a sample (Fig. 1A). Combining optical microscopy with the real-time, label-free chemical information obtained from Raman spectroscopy directly reveals the sequence of steps that lead to oxidative spore death after H2O2 exposure (Fig. 1B).We find that spore degradation begins with the fast, cooperative release of dipicolinic acid (DPA), a key spore biomarker and a major component of spore’s core. This indicates a breach of the inner membrane surrounding the core. The onset of DPA release depends on the concentration of H2O2. DPA outflux is accompanied by the formation of oxidation products (mostly carbonyl compounds) and oxidation continues after exchange of DPA with the surrounding medium is complete. The remaining spore shell then slowly disintegrates and continues to shrink on a timescale of hundreds of seconds. Simultaneous observation of spore morphology and size by optical microscopy and particle tracking corroborates this three-step mechanism.The presented assay allows on-line monitoring of spore composition and morphology, which directly reveals the mechanism underlying the sporicidal action of H2O2. In addition, trapped spores can be exposed to different chemical or physical stimuli (temperature, light, chemical composition of the surrounding medium, etc.) to investigate a variety of industrially relevant sterilization conditions. Jildeh, Z. B., Wagner, P. H. & Schöning, M. J. Sterilization of Objects, Products, and Packaging Surfaces and Their Characterization in Different Fields of Industry: The Status in 2020. physica status solidi (a) 218, 2000732 (2021). Setlow, P. & Christie, G. What’s new and notable in bacterial spore killing. World J Microbiol Biotechnol 37, 144 (2021). Setlow, P. Spores of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals. J Appl Microbiol 101, 514-525 (2006). Figure 1