Dipicolinic Acid Research Articles

Dual-emission Tb-based coordination polymer as a ratiometric fluorescence probe for the detection of phosphate.

A simple, sensitive dual-emission probe was developed for the detection of phosphate (Pi). The probe Tb-BTB/DPA was synthesized by mixing dual-ligand, 1,3,5-tri(4-carboxyphenyl) benzene (H3BTB) and dipicolinic acid (DPA), with metal ions Tb3+ in ethanol-water solution at 40℃ for 2h. Tb-BTB/DPA exhibits two emission peaks, the emission at 362nm is attributed to H3BTB, an energy transfer between Tb3+ nodes, and DPA further enhances the fluorescence of Tb3+ at 544nm. Pi competes with ligand H3BTB to coordinate Tb3+, resulting in partial collapse of the Tb-BTB/DPA structure and interrupting the electron transfer between H3BTB and Tb3+. Therefore, the emission at 362nm is enhanced, while the emission at 544nm is unchanged, and a ratiometric fluorescence method is developed to detect Pi. Tb-BTB/DPA exhibits good linearity within the Pi concentration range (0.1-50µmol/L), and the detection limit was 25.8nmol/L. This study provides a new way to prepare probes with dual emission sensing properties.

Zn-CD@Eu Ratiometric Fluorescent Probe for the Detection of Dipicolinic Acid, Uric Acid, and Ex Vivo Uric Acid Imaging.

Development of reliable methods for the detection of potential biomarkers is of the utmost importance for an early diagnosis of critical diseases and disorders. In this study, a novel lanthanide-functionalized carbon dot-based fluorescent probe Zn-CD@Eu is reported for the ratiometric detection of dipicolinic acid (DPA) and uric acid (UA). The Zn-CD@Eu nanoprobe was obtained from a simple room-temperature reaction of zinc-doped carbon dots (Zn-CD) and the EDTA-Eu lanthanide complex. Under optimal conditions, a good linear response was obtained for DPA in two concentration ranges of 0-55 and 55-100 μM with a limit of detection of 0.53 and 2.2 μM respectively, which is significantly below the infectious dosage of anthrax (∼55 μM). Furthermore, the Zn-CD@Eu/DPA system was employed for the detection of UA with a detection limit of 0.36 μM in the linear range of 0-100 μM. The fluorescent probe was successfully implemented for determining DPA and UA in human blood serum, sweat, and natural water bodies with considerable recovery rates. In addition, the potential of the nanoprobe for ex vivo visualization of UA was demonstrated in fruit fly (Drosophila melanogaster) as a model organism.

Filling two needs with one deed: Differential sensing of anthrax biomarker dipicolinic acid and bovine serum albumin using binary ensemble based on 1,8-naphthalimide Schiff base and cationic surfactant

Keeping in mind the severities of anthrax disease caused by bacteria Bacillus anthracis and side effects of abnormal levels of a nonmetalloprotein bovine serum albumin (BSA), their early diagnosis was highly required. The existing lanthanide based sensors for their detection are not up to the mark due to their potential disadvantages of genetic toxicity, bio-migration, supply shortages, low atom utilization and poor stability. To address these issues, a binary ensemble OHNP@CTAB was fabricated in aqueous medium by encapsulation of 1,8-naphthalimide derived Schiff base (OHNP) in the micelles of a cationic surfactant CTAB. Significant changes were observed in the absorption and emission spectrum of OHNP@CTAB in the presence of DPA and BSA mainly due to electrostatic interaction among positively charged receptor and negatively charged guest species. Limit of detection (LOD) values of OHNP@CTAB towards DPA and BSA were calculated to be 1.19 and 0.11 µM, respectively from fluorescence spectral titration data. Moreover, the binary ensemble OHNP@CTAB efficiently detected BSA and DPA in real samples viz. packaged milk, gulkand and candy.

Dual fluorophores embedded in zeolitic imidazolate framework‑8 for ratiometric fluorescence sensing of a biomarker of anthrax spores

The precise and selective monitoring of dipicolinic acid (DPA), a particular biomarker associated with anthrax spores, is crucial for the rapid detection and diagnosis of anthrax infection. A ratiometric fluorescence nanoprobe called AuNCs/GQDs@ZIF-8, has been designed by encapsulating gold nanoclusters (AuNCs) and graphene quantum dots (GQDs) into zeolitic imidazolate framework‑8 (ZIF-8) for sensing DPA. By leveraging enrichment effects of ZIF-8, embedded AuNCs restricts intramolecular movements and triggers aggregation-induced emission, further acquiring bright fluorescence. In the presence of europium ions (Eu3+), the fluorescence of AuNCs@ZIF-8 significantly decreases due to static quenching. However, Eu3+ are sequestered by DPA through strong coordination effects, causing fluorescence recovery of AuNCs@ZIF-8. Eu3+-mediated AuNCs@ZIF-8 therefore serve as response signals for DPA recognition. Integrating with stable reference signals of GQDs, a ratiometric fluorescence sensor exhibits the satisfactory linearity of 0.1–200 µM and detection limit of 32 nM. Furthermore, the smartphone-integrated visual mode can immediately identify fluorescence colors for assessing DPA. Compared to alternative nanoprobes, this ratiometric fluorescence sensor demonstrates higher sensitivity, lowering than DPA commonly released by infectious spores (60 µM). This study not only provides the promising sensor for DPA measurement during early anthrax diagnosis, but offers insights on designing ratiometric sensors with diverse fluorescence nanomaterials.

Smartphone-assisted mobile fluorescence sensor for self-calibrated detection of anthrax biomarker, Cu2+, and cysteine in food analysis

Dipicolinic acid (DPA), as a biomarker for Bacillus anthracis, is highly toxic at trace levels. Rapid and on-site quantitative detection of DPA is essential for maintaining food safety and public health. This work develops a dual-channel self-calibrated fluorescence sensor constructed by the YVO4:Eu and Tb-β-diketone complex for rapid visual detection of DPA. This sensor exhibits high selectivity, fast response time, excellent detection sensitivity, and the detection limit is as low as 4.5 nM in the linear range of 0–16 μM. A smartphone APP and portable ultraviolet lamp can assemble a mobile fluorescence sensor for on-site analysis. Interestingly, adding Cu2+ ions can quench the fluorescence intensity of Tb3+. In contrast, the addition of cysteine can restore the fluorescence, allowing the accurate detection of Cu2+ ions and cysteine in environmental water and food samples. This work provides a portable sensor that facilitates real-time analysis of multiple targets in food and the environment.

Single-cell analysis reveals microbial spore responses to sodium hypochlorite.

Pollution from toxic spores has caused us a lot of problems because spores are extremely resistant and can survive most disinfectants. Therefore, the detection of spore response to disinfectant is of great significance for the development of effective decontamination strategies. In this work, we investigated the effect of 0.5% sodium hypochlorite on the molecular and morphological properties of single spores of Bacillus subtilis using single-cell techniques. Laser tweezers Raman spectroscopy showed that sodium hypochlorite resulted in Ca2+-dipicolinic acid release and nucleic acid denaturation. Atomic force microscopy showed that the surface of treated spores changed from rough to smooth, protein shells were degraded at 10 min, and the permeability barrier was destroyed at 15 min. The spore volume decreased gradually over time. Live-cell imaging showed that the germination and growth rates decreased with increasing treatment time. These results provide new insight into the response of spores to sodium hypochlorite.

A Dual-Mode Fluorescent Nanoprobe for the Detection and Visual Screening of Pathogenic Bacterial Spores.

Bacterial vegetative cells turn into metabolically dormant spores in certain environmental situations. Once suitable conditions trigger the germination of spores belonging to the pathogenic bacterial category, public safety and environmental hygiene will be threatened, and lives will even be endangered when encountering fatal ones. Instant identification of pathogenic bacterial spores remains a challenging task, since most current approaches belonging to complicated biological methods unsuitable for onsite sensing or emerging alternative chemical techniques are still inseparable from professional instruments. Here we developed a polychromatic fluorescent nanoprobe for ratiometric detection and visual inspection of the pathogenic bacterial spore biomarker, dipicolinic acid (DPA), realizing rapidly accurate screening of pathogenic bacterial spores such as Bacillus anthracis spores. The nanoprobe is made of aminoclay-coated silicon nanoparticles and functionalized with europium ions, exhibiting selective and sensitive response toward DPA and Bacillus subtilis spores (simulants for Bacillus anthracis spores) with excellent linearity. The proposed sensing strategy allowing spore determination of as few as 0.3 × 105 CFU/mL within 10 s was further applied to real environmental sample detection with good accuracy and reliability. Visual quantitative determination can be achieved by analyzing the RGB values of the corresponding test solution color via a color recognition APP on a smartphone. Different test samples can be photographed at the same time, hence the efficient accomplishment of examining bulk samples within minutes. Potentially employed in various on-site sensing occasions, this strategy may develop into a powerful means for distinguishing hazardous pathogens to facilitate timely and proper actions of dealing with multifarious security issues.

Inactivation of Alicyclobacillus acidoterrestris in apple juice using pulsed light

We aimed to investigate the effect of pulsed light (PL) on inactivating Alicyclobacillus acidoterrestris in apple juice, the mechanism behind the inactivation, and the resultant effects on the quality of the juice. Our results showed that PL had a good inactivation effect on both spores and vegetative cells of A. acidoterrestris in apple juice, with a reduction of 3.5 ± 0.1 and 2.1 ± 0.1 log CFU/mL, respectively, following 3 s of treatment. This effect was better when lower concentrations of apple juice and lower liquid layer depths were used. Transmission electron microscopy (TEM) showed that the morphology and structure of A. acidoterrestris spores did not change significantly before and after treatment. When we compared the dipicolinic acid (DPA) release rate and death rate of the spores, we hypothesized that PL might have damaged the cortical proteins on A. acidoterrestris that are associated with the resistance of the spores, thus leading to their death. However, TEM revealed that the cell membranes of vegetative cells of A. acidoterrestris were intact and smooth before the treatment, but significantly wrinkled afterward. Raman spectroscopy revealed that the main targets of PL on A. acidoterrestris vegetative cells were: amide I on the proteins, nucleic acids [adenine(A) and guanine (G), in particular] and DNA (O–P–O¯ stretching) structures, and lipids (C–H2 deformation). The PL treatment increased the sugar content significantly, while having little to no effect on the other basic physicochemical parameters of apple juice.

Bridging biological and food monitoring: A colorimetric and fluorescent dual-mode sensor based on N-doped carbon dots for detection of pH and histamine

Rapid and sensitive monitoring of pH and histamine is crucial for bridging biological and food systems and identifying corresponding abnormal situations. Herein, N-doped carbon dots (CDs) are fabricated by a hydrothermal method employing dipicolinic acid and o-phenylenediamine as precursors. The CDs exhibit colorimetric and fluorescent dual-mode responses to track pH and histamine variations in living cells and food freshness, respectively. The aggregation-induced emission enhancement and intramolecular charge transfer result in a decrease in absorbance and an increase in fluorescence, which become readily apparent as the pH changes from acidic to neutral. This property enables precise differentiation between normal and cancerous cells. Furthermore, given the intrinsic basicity of histamine, pH-responsive CDs are advantageous for additional colorimetric and fluorescent monitoring of histamine in food freshness, achieving linearities of 25-1000µM and 30-1000µM, respectively, which are broader than those of alternative nanoprobes. Interestingly, smartphone-integrated sensing platform can portably and visually evaluate pH and histamine changes due to sensitive color changes. Therefore, the sensor not only establishes a dynamic connection between pH and histamine for the purposes of biological and food monitoring, but also presents a novel approach for developing a multifunctional biosensor that can accomplish environmental monitoring and biosensing simultaneously. Environmental ImplicationHigh amounts of histamine, hazardous substances produced by spoiled food, pose adverse effects for food poisoning and human health including vomiting, head-aches and death. Based on their harmfulness, the threshold histamine should be strictly controlled. So rapid and accurate histamine evaluation is crucial. This work employs a colorimetric and fluorescent CDs for pH and histamine dual-mode monitoring, achieving dynamic bridges of hazardous histamine between biological and food monitoring. Interestingly, sensitive color changes make smartphone-integrated sensor more portable and visual than other probes. This enables CDs a multifunctional biosensor for monitoring histamines with realistically detecting ranges to meet practical needs.

A water stable europium coordination polymer based on mixed organic ligands as a luminescence sensor for the detection of an anthrax biomarker

The development of luminescence sensors capable of detecting anthrax biomarkers is crucial for preventing anthrax. In this study, a two-dimensional europium coordination polymer [Eu(dlba)(phen)·2(H2O)]n (CP-1) was prepared based on a rigid 1,10-phenanthroline (phen) and a flexible 2-(3,5-dicarboxybenzyloxy) benzoic acid (H3dlba) under the hydrothermal conditions. The CP-1 was characterized by powder X-ray diffraction, elemental analysis, thermogravimetric analysis, infrared spectroscopy, and single crystal X-ray diffraction. The CP-1 exhibits excellent water stability and thermal stability. Luminescence experiments demonstrated a high luminescence quenching efficiency (98.1 %) upon addition of the anthrax biomarker dipicolinic acid (DPA). Additionally, the sensor shows good sensitivity and a rapid response time of 30 s. The detection limit is as low as 0.12 µM, which is much lower than the infection dose of spores (60 µM). The sensor has a recovery rate of 95–105 % when tested on actual samples, indicating its potential for practical applications. The luminescence quenching effect may be due to the competitive absorption of DPA, which affects the efficiency of energy transfer from the ligands to the europium ions.

A dual‐responsive luminescent sensor for efficient detection of 3‐nitrotyrosine and dipicolinic acid biomarkers based on copper(II) organic framework

The trace detection of biomarkers in real samples has profound a most important significance in the early diagnosis and daily monitoring of diseases. Based on the ligand pre‐design strategy, a novel 3D CuMOF, with the formula of {[Cu4(BTPB)(μ2‐OH)2(H2O)5]·3H2O}n, was fabricated by using the hexacarboxyl ligand of 1,4‐bis(2,4,6‐tricarboxylpyrid‐5‐yl)benzene (H6BTPB) and tetranuclear {Cu4(COO)4(μ2‐OH)2} SBUs. Benefiting from the robust framework and unique luminescence performance, the prepared CuMOF displays great potential as a dual‐responsive efficient luminescent sensor in “turn‐off” detection of 3‐nitrotyrosine (3‐NT) biomarker and “turn‐on” detecting the anthrax biomarker of dipicolinic acid (DPA), with detection limits (LOD) for 3‐NT and DPA being 110.8 ng/ml and 85.2 ng/ml, respectively. Additionally, the practicality and compatibility of such developed sensors were verified by quantifying 3‐NT and DPA biomarkers in diluted serum and urine samples with satisfactory recoveries. Further, the theoretical calculations of energy levels as well as the spectral overlap between the analytes and CuMOF were conducted to elucidate the possible sensing mechanisms. This work demonstrated that MOFs‐based luminescent sensors are evolving as an efficacious and equable approach for the detection of biomarkers in real samples.

Engineering Pseudomonas putida KT2440 for Dipicolinate Production via the Entner-Doudoroff Pathway.

Dipicolinic acid (DPA), a cyclic diacid, has garnered significant interest due to its potential applications in antimicrobial agents, antioxidants, chelating reagents, and polymer precursors. However, its natural bioproduction is limited since DPA is only accumulated in Bacillus and Clostridium species during sporulation. Thus, heterologous production by engineered strains is of paramount importance for developing a sustainable biological route for DPA production. Pseudomonas putida KT2440 has emerged as a promising host for the production of various chemicals thanks to its robustness, metabolic versatility, and genetic tractability. The dominant Entner-Doudoroff (ED) pathway for glucose metabolism in this strain offers an ideal route for DPA production due to the advantage of NADPH generation and the naturally balanced flux between glyceraldehyde-3-phosphate and pyruvate, which are both precursors for DPA synthesis. In this study, DPA production via the ED pathway was in silico designed in P. putida KT2440. The systematically engineered strain produced dipicolinate with a titer of 11.72 g/L from glucose in a 5 L fermentor. This approach not only provides a sustainable green route for DPA production but also expands our understanding of the metabolic potential of the ED pathway in P. putida KT2440.

Effect of Cu(II) compound containing dipicolinic acid on DNA damage: a study of antiproliferative activity and DNA interaction properties by spectroscopic, molecular docking and molecular dynamics approaches

A polymeric compound formulized as [Cu(µ-dipic)2{Na2(µ-H2O)4]n.2nH2O (I), where dipic is 2,6-pyridine dicarboxylic acid (dipicolinic acid, H2dipic), was synthesized by sonochemical irradiation. The initial in-vitro cytotoxic activity of this complex compared with renowned anticancer drugs like cisplatin, versus HCT116 colon cell lines, shows promising results. This study investigated the interaction mode between compound (I) and calf-thymus DNA utilizing a range of analytical techniques including spectrophotometry, fluorimetry, partition coefficient analysis, viscometry, gel electrophoresis and molecular docking technique. The results obtained from experimental methods reveal complex (I) could bind to CT-DNA via hydrogen bonding and van der Waals forces and the theoretical methods support it. Also, complex (I) indicates nuclease activity in the attendance of H2O2 and can act as an artificial nuclease to cleave DNA with high efficiency. Communicated by Ramaswamy H. Sarma

Insight into effects of terbium on cell growth, sporulation and spore properties of Bacillus subtilis.

Recovery of rare earth elements (REEs) from wastewater with Bacillus subtilis(B. subtilis)during culture is promising due to its environmental benefits. However, the effects of REEs in the culture media on B. subtilis are poorly understood. This study aims to investigate the effects of the terbium (Tb(III)), a typical rare earth element, on the cell growth, sporulation, and spore properties of B. subtilis. Tb(III) can suppress bacterial growth while enhancing spore tolerance to wet heat. Spore germination and content of dipicolinic acid (DPA) were promoted at low concentrations of Tb(III) while inhibited at a high level, but an inverse effect on initial sporulation appeared. Scanning electron microscope and energy dispersive spectrometer detection indicated that Tb(III) complexed cells or spores and certain media components simultaneously. The germination results of the spores after elution revealed that Tb(III) attached to the spore surface was a key effector of spore germination. In conclusion, Tb(III) directly or indirectly regulated both the nutrient status of the media and certain metabolic events, which in turn affected most of the properties of B. subtilis. Compared to the coat-deficient strain, the wild-type strain grew faster and was more tolerant to Tb(III), DPA, and wet heat, which in turn implied that it was more suitable for the recovery of REEs during cultivation. These findings provide fundamental insights for the recovery of rare earths during the culture process using microorganisms.

Influence of Temperature, Light, and H2O2 Concentration on Microbial Spore Inactivation: In‐Situ Raman Spectroscopy Combined with Optical Trapping

To gain insight on chemical sterilization processes, the influence of temperature (up to 70 °C), intense green light, and hydrogen peroxide (H2O2) concentration (up to 30% in aqueous solution) on microbial spore inactivation is evaluated by in‐situ Raman spectroscopy with an optical trap. Bacillus atrophaeus is utilized as a model organism. Individual spores are isolated and their chemical makeup is monitored under dynamically changing conditions (temperature, light, and H2O2 concentration) to mimic industrially relevant process parameters for sterilization in the field of aseptic food processing. While isolated spores in water are highly stable, even at elevated temperatures of 70 °C, exposure to H2O2 leads to a loss of spore integrity characterized by the release of the key spore biomarker dipicolinic acid (DPA) in a concentration‐dependent manner, which indicates damage to the inner membrane of the spore. Intensive light or heat, both of which accelerate the decomposition of H2O2 into reactive oxygen species (ROS), drastically shorten the spore lifetime, suggesting the formation of ROS as a rate‐limiting step during sterilization. It is concluded that Raman spectroscopy can deliver mechanistic insight into the mode of action of H2O2‐based sterilization and reveal the individual contributions of different sterilization methods acting in tandem.

Polyarylether-based COFs coordinated by Tb3+ for the fluorescent detection of anthrax-biomarker dipicolinic acid.

In this study, a rare-earth hybrid luminescent material (lanthanide@COF) was constructed for the detection of a biomarker for anthrax (dipicolinic acid, DPA). JCU-505-COOH was prepared by the hydrolysis of the cyano group in JCU-505 via a post-synthetic modification strategy, then the carboxyl groups in JCU-505-COOH coordinated with Tb3+ ions, similar to pincer vising nut. The prepared Tb3+@JCU-505-COOH exhibited a turn-on response toward DPA, which allowed the lanthanide@COF to serve as a fluorescence sensor with excellent selectivity and high sensitivity (binding constant Ka = 3.66 × 103). The fluorescent probe showed satisfactory performance for the determination of DPA in saliva and urine with a detection limit of 0.6 μM. Moreover, we established a facile point-of-care testing (POCT) using the Tb3+@JCU-505-COOH-based fluorescent test paper together with a smartphone for the initial diagnosis of anthrax. As expected, Tb3+@JCU-505-COOH showed great potential for the rapid screening of anthrax due to low cost, simple operation, and wide applicability.

A terbium-functionalized ZIF-8 nanosensor for rapid and sensitive detection of an anthrax spore biomarker

Because anthrax spores are highly lethal to humans and animals as well as potential biological warfare agents, there is a great need for rapid, sensitive, and selective quantification of dipicolinic acid (DPA) as a biomarker for anthrax spores.

Spore germination: Two ion channels are better than one.

Germination is the process by which spores emerge from dormancy. Although spores can remain dormant for decades, the study of germination is an active field of research. In this issue of Genes & Development, Gao and colleagues (pp. 31-45) address a perplexing question: How can a dormant spore initiate germination in response to environmental cues? Three distinct complexes are involved: GerA, a germinant-gated ion channel; 5AF/FigP, a second ion channel required for amplification; and SpoVA, a channel for dipicolinic acid (DPA). DPA release is followed by rehydration of the spore core, thus allowing the resumption of metabolic activity.

A comparison of the catalytic activities of oxovanadium(IV) and cobalt(II) complex compounds in the oligomerization of ethylene

The polymerization and oligomerization of olefins, especially ethylene, is a process of great industrial and scientific importance in polymer chemistry. Catalysts are an essential part of this reaction, and a new report of a catalyst improving this process is worthy of special attention. During this study, nine complex compounds based on oxovanadium(IV) and cobalt(II) ions in combination with organic ligands, e.g., dipicolinic acid, 2,2′-bipyridine, iminodiacetic acid, diglycolic acid, thiodiacetic acid, 1,10-phenanthroline were synthesized. The compound [VO(tda) · 0.5 H2O] is a new complex not previously reported in the literature, and its synthesis and structure are described in this article. The high catalytic activity values in other oligomerization processes in other olefins led us to use the synthesized compounds as precatalysts in the oligomerization reaction. Subsequently, their catalytic activity was also calculated in this process. The obtained oligomerization products were then analyzed by IR, MALDI-TOF-MS, TG, DSC, and SEM techniques to characterize the obtained products and verify the correctness of the oligomerization reaction. Based on the obtained data, the catalytic activity values were compared and the most active catalyst was selected. The best catalyst was a cobalt(II) compound containing an iminodiacetic acid anion and 2,2′-bipyridine in its structure. However, all complexes can be classified as highly active and active catalysts for ethylene oligomerization. The presented studies show novel catalysts that have in their structure other metal ions than those most commonly used in the literature so far. Additionally, coordination compounds of this type have not been previously used in ethylene oligomerization. Moreover, these studies are a source of knowledge on the correlation between catalyst structure and catalytic activity value, thanks to which they provide essential information necessary for the design of next-generation catalysts used for ethylene oligomerization and polymerization.

Spectroscopic and molecular docking investigation on the interaction of a water-soluble Cu(II) complex containing diethanolamine and dipicolinic acid ligands with human serum albumin

Under physiological conditions, spectroscopic techniques as well as molecular docking simulation have been used to investigate the binding interaction mechanism between Cu(II) complex containing Pyridine-2,6-dicarboxylic acid (PDCA) and Diethanolamine (DEA) ligands, [Cu(DEA)(PDCA)] and human serum albumin (HSA). UV spectral changes of protein in the presence of the Cu(II) complex suggested the formation of a Protein-Cu(II) complex conjugate with specific new structure. The Cu(II) complex quenches the intrinsic fluorescence of the HSA via a static mechanism in which van der Waals interactions along with hydrogen bonds are fundamental binding forces. Displacement experiments performed by warfarin and ibuprofen site probes predict that the Cu(II) complex is located in subdomain IIA, Sudlow site 1 of HSA. Molecular docking results showed close resemblance with experimental data. Communicated by Ramaswamy H. Sarma