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Jin S, Pang J, Ma F, Cheng Y, Shen Y, Xiao Z, Chen L. Regulating valence states of CuFe-PBA for the simultaneous electrochemical detection of Cd 2+, Pb 2+ and Hg 2+ in food application. Talanta 2024; 273:125848. [PMID: 38432072 DOI: 10.1016/j.talanta.2024.125848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 02/03/2024] [Accepted: 02/28/2024] [Indexed: 03/05/2024]
Abstract
Prussian blue analogues, as prospective electrode materials, play a crucial role in detecting heavy metal ions (HMIs), a process closely related to their electron transfer capacities and active surfaces. Here, etched copper-iron Prussian blue analogues (CuFe-PBA) are synthesized through a combination of flash nanoprecipitation (FNP) and an alkali etching process. Furthermore, this study investigates the impact of ammonia on the electronic structure of CuFe-PBA and its electrochemical detection capabilities for HMIs. The etched CuFe-PBA (e-CuFe-PBA) exhibits excellent detection performance for Cd2+, Pb2+ and Hg2+ with 17.6 μA μM-1, 24.2 μA μM-1 and 26.2 μA μM-1, respectively, due to the fact that the ammonia etching not only modulates the electronic properties of the surface of CuFe-PBA but also reduces the degree of agglomeration and enhances the accessible surface area. Additionally, it demonstrates excellent stability and resistance to interference, having been successfully applied to detect HMIs in food samples such as preserved eggs and apple juice. These results provide a new strategy for the use of Prussian blue analogues as electrochemical sensors for food safety applications.
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Affiliation(s)
- Shan Jin
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China.
| | - Jianxiang Pang
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China
| | - Fanpeng Ma
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China
| | - Yikun Cheng
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China
| | - Yunfei Shen
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China
| | - Zemao Xiao
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China
| | - Long Chen
- School of Chemistry and Chemical Engineering, Shihezi University/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering, Shihezi, 832003, PR China.
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Rehman AU, Fayaz M, Lv H, Liu Y, Zhang J, Wang Y, Du L, Wang R, Shi K. Controllable Synthesis of a Porous PEI-Functionalized Co 3O 4/rGO Nanocomposite as an Electrochemical Sensor for Simultaneous as Well as Individual Detection of Heavy Metal Ions. ACS OMEGA 2022; 7:5870-5882. [PMID: 35224348 PMCID: PMC8867791 DOI: 10.1021/acsomega.1c05989] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
The present study focuses on the strategy of employing an electrochemical sensor with a porous polyethylenimine (PEI)-functionalized Co3O4/reduced graphene oxide (rGO) nanocomposite (NCP) to detect heavy metal ions (HMIs: Cd2+, Pb2+, Cu2+, and Hg2+). The porous PEI-functionalized Co3O4/rGO NCP (rGO·Co3O4·PEI) was prepared via a hydrothermal method. The synthesized NCP was based on a conducting polymer PEI, rGO, nanoribbons of Co3O4, and highly dispersed Co3O4 nanoparticles (NPs), which have shown excellent performance in the detection of HMIs. The as-prepared PEI-functionalized rGO·Co3O4·PEI NCP-modified electrode was used for the sensing/detection of HMIs by means of both square wave anodic stripping voltammetry (SWV) and differential normal pulse voltammetry (DNPV) methods for the first time. Both methods were employed for the simultaneous detection of HMIs, whereas SWV was employed for the individual analysis as well. The limits of detection (LOD; 3σ method) for Cd2+, Pb2+, Cu2+, and Hg2+ determined using the rGO·Co3O4·PEI NCP-modified electrode were 0.285, 1.132, 1.194, and 1.293 nM for SWV, respectively. Similarly, LODs of Cd2+, Pb2+, Cu2+, and Hg2+ were 1.069, 0.285, 2.398, and 1.115 nM, respectively, by DNPV during simultaneous analysis, whereas they were 0.484, 0.878, 0.462, and 0.477 nM, respectively, by SWV in individual analysis.
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Affiliation(s)
- Afrasiab Ur Rehman
- Department
of Chemistry, Khushal Khan Khattak University,
Karak, 27200 Karak, Khyber Pakhtunkhawa, Pakistan
- Key
Laboratory of Functional Inorganic Material Chemistry, Ministry of
Education. School of Chemistry and Material Science, Heilongjiang University, Harbin 150080, P. R. China
| | - Muhammad Fayaz
- Department
of Chemistry, Khushal Khan Khattak University,
Karak, 27200 Karak, Khyber Pakhtunkhawa, Pakistan
| | - He Lv
- Key
Laboratory of Functional Inorganic Material Chemistry, Ministry of
Education. School of Chemistry and Material Science, Heilongjiang University, Harbin 150080, P. R. China
| | - Yang Liu
- Key
Laboratory of Functional Inorganic Material Chemistry, Ministry of
Education. School of Chemistry and Material Science, Heilongjiang University, Harbin 150080, P. R. China
| | - Jiawei Zhang
- Modern
Experiment Center, Harbin Normal University, Harbin 150025, P. R. China
| | - Yang Wang
- Key
Laboratory of Functional Inorganic Material Chemistry, Ministry of
Education. School of Chemistry and Material Science, Heilongjiang University, Harbin 150080, P. R. China
| | - Lijuan Du
- Modern
Experiment Center, Harbin Normal University, Harbin 150025, P. R. China
| | - Ruihong Wang
- Key
Laboratory of Functional Inorganic Material Chemistry, Ministry of
Education. School of Chemistry and Material Science, Heilongjiang University, Harbin 150080, P. R. China
| | - Keying Shi
- Key
Laboratory of Functional Inorganic Material Chemistry, Ministry of
Education. School of Chemistry and Material Science, Heilongjiang University, Harbin 150080, P. R. China
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3
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Xing C, Chen Z, Zhang C, Wang J, Lu C. Construction of a Target-Initiated, Enzyme-Free DNA Cascade Circuit for Amplified Detection of Mercury. ACS APPLIED BIO MATERIALS 2020; 3:1853-1857. [DOI: 10.1021/acsabm.0c00142] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Chao Xing
- Fujian Provincial Key Laboratory of Functional Marine Sensing Materials, Center for Advanced Marine Materials and Smart Sensors, Minjiang University, Fuzhou 350108, P. R. China
| | - Ziyi Chen
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, College of Chemistry, Fuzhou University, Fuzhou 350116, P. R. China
| | - Cheng Zhang
- Fujian Provincial Key Laboratory of Functional Marine Sensing Materials, Center for Advanced Marine Materials and Smart Sensors, Minjiang University, Fuzhou 350108, P. R. China
| | - Jun Wang
- Fujian Provincial Key Laboratory of Functional Marine Sensing Materials, Center for Advanced Marine Materials and Smart Sensors, Minjiang University, Fuzhou 350108, P. R. China
| | - Chunhua Lu
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, College of Chemistry, Fuzhou University, Fuzhou 350116, P. R. China
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Ramachandran R, Chen TW, Chen SM, Baskar T, Kannan R, Elumalai P, Raja P, Jeyapragasam T, Dinakaran K, Gnana kumar GP. A review of the advanced developments of electrochemical sensors for the detection of toxic and bioactive molecules. Inorg Chem Front 2019. [DOI: 10.1039/c9qi00602h] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The recent developments made regarding the novel, cost-effective, and environmentally friendly nanocatalysts for the electrochemical sensing of biomolecules, pesticides, nitro compounds and heavy metal ions are discussed in this review article.
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Affiliation(s)
| | - Tse-Wei Chen
- Electroanalysis and Bioelectrochemistry Lab
- Department of Chemical Engineering and Biotechnology
- National Taipei University of Technology
- Taipei 106
- Republic of China
| | - Shen-Ming Chen
- Electroanalysis and Bioelectrochemistry Lab
- Department of Chemical Engineering and Biotechnology
- National Taipei University of Technology
- Taipei 106
- Republic of China
| | - Thangaraj Baskar
- School of Food and Biological Engineering
- Jiangsu University
- Zhenjiang – 212013
- P.R. China
| | - Ramanjam Kannan
- Department of Chemistry
- Sri Kumaragurupara Swamigal Arts College
- Thoothukudi
- India
| | - Perumal Elumalai
- Centre for Green Energy Technology
- Madanjeet School of Green Energy Technologies
- Pondicherry University
- Puducherry – 605 014
- India
| | - Paulsamy Raja
- Department of Chemistry
- Vivekananda College of Arts and Science
- Kanyakumari – 629 004
- India
| | | | | | - George peter Gnana kumar
- Department of Physical Chemistry
- School of Chemistry
- Madurai Kamaraj University
- Madurai-625 021
- India
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Gallo G, Presta L, Perrin E, Gallo M, Marchetto D, Puglia AM, Fani R, Baldi F. Genomic traits of Klebsiella oxytoca DSM 29614, an uncommon metal-nanoparticle producer strain isolated from acid mine drainages. BMC Microbiol 2018; 18:198. [PMID: 30482178 PMCID: PMC6258164 DOI: 10.1186/s12866-018-1330-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 10/29/2018] [Indexed: 12/24/2022] Open
Abstract
Background Klebsiella oxytoca DSM 29614 - isolated from acid mine drainages - grows anaerobically using Fe(III)-citrate as sole carbon and energy source, unlike other enterobacteria and K. oxytoca clinical isolates. The DSM 29614 strain is multi metal resistant and produces metal nanoparticles that are embedded in its very peculiar capsular exopolysaccharide. These metal nanoparticles were effective as antimicrobial and anticancer compounds, chemical catalysts and nano-fertilizers. Results The DSM 29614 strain genome was sequenced and analysed by a combination of in silico procedures. Comparative genomics, performed between 85 K. oxytoca representatives and K. oxytoca DSM 29614, revealed that this bacterial group has an open pangenome, characterized by a very small core genome (1009 genes, about 2%), a high fraction of unique (43,808 genes, about 87%) and accessory genes (5559 genes, about 11%). Proteins belonging to COG categories “Carbohydrate transport and metabolism” (G), “Amino acid transport and metabolism” (E), “Coenzyme transport and metabolism” (H), “Inorganic ion transport and metabolism” (P), and “membrane biogenesis-related proteins” (M) are particularly abundant in the predicted proteome of DSM 29614 strain. The results of a protein functional enrichment analysis - based on a previous proteomic analysis – revealed metabolic optimization during Fe(III)-citrate anaerobic utilization. In this growth condition, the observed high levels of Fe(II) may be due to different flavin metal reductases and siderophores as inferred form genome analysis. The presence of genes responsible for the synthesis of exopolysaccharide and for the tolerance to heavy metals was highlighted too. The inferred genomic insights were confirmed by a set of phenotypic tests showing specific metabolic capability in terms of i) Fe2+ and exopolysaccharide production and ii) phosphatase activity involved in precipitation of metal ion-phosphate salts. Conclusion The K. oxytoca DSM 29614 unique capabilities of using Fe(III)-citrate as sole carbon and energy source in anaerobiosis and tolerating diverse metals coincides with the presence at the genomic level of specific genes that can support i) energy metabolism optimization, ii) cell protection by the biosynthesis of a peculiar exopolysaccharide armour entrapping metal ions and iii) general and metal-specific detoxifying activities by different proteins and metabolites. Electronic supplementary material The online version of this article (10.1186/s12866-018-1330-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Giuseppe Gallo
- Laboratory of Molecular Microbiology and Biotechnology, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Viale delle Scienze, ed. 16, 90128, Palermo, Italy.
| | - Luana Presta
- Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Via Madonna del Piano 6, I-50019 Sesto F.no, Florence, Italy
| | - Elena Perrin
- Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Via Madonna del Piano 6, I-50019 Sesto F.no, Florence, Italy
| | - Michele Gallo
- Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre, Venezia, Italy
| | - Davide Marchetto
- Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre, Venezia, Italy
| | - Anna Maria Puglia
- Laboratory of Molecular Microbiology and Biotechnology, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Viale delle Scienze, ed. 16, 90128, Palermo, Italy
| | - Renato Fani
- Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Via Madonna del Piano 6, I-50019 Sesto F.no, Florence, Italy
| | - Franco Baldi
- Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre, Venezia, Italy
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Wang S, Lin B, Chen L, Li N, Xu J, Wang J, Yang Y, Qi Y, She Y, Shen X, Xiao X. Branch-Migration Based Fluorescent Probe for Highly Sensitive Detection of Mercury. Anal Chem 2018; 90:11764-11769. [PMID: 30232889 DOI: 10.1021/acs.analchem.8b03547] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Detection of heavy metals is of great importance for food safety and environmental analysis. Among various heavy metal ions, mercury ion is one of the most prevalent species. The methods for detection of mercury were numerous, and the T-Hg-T based assay was promising due to its simplicity and compatibility. However, traditional T-Hg-T based methods mainly relied on multiple T-Hg-T to produce enough conformational changes for further detection, which greatly restrained the limit of detection. Hence, we established a branch-migration based fluorescent probe and found that single T-Hg-T could produce strong signals. The sensing mechanism of our method in different reaction modes was explored, and the detection limits were determined to be 18.4 and 14.7 nM in first-order reaction mode and mixed reaction mode, respectively. Moreover, coupled with Endonuclease IV assisted signal amplification, the detection limit could be 1.2 nM, lower than most DNA based fluorometric assays. For practicability, the specificity of our assay toward different interfering ions was investigated and detection of Hg2+ in deionized water and lake water was also achieved with similar recoveries compared to those of atomic fluorescence spectrometry, which demonstrated the practicability of our method in real samples. Definitely, the proposed branch migration probe would be a promising substitution for current DNA probes based on recognition of multiple T-Hg-T and we anticipate it to be widely adopted in food and environmental analysis.
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Affiliation(s)
- Shanshan Wang
- Key Laboratory of Agrifood Safety and Quality, Ministry of Agriculture of China, Institute of Quality Standards & Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing , 100081 , P.R. China
| | - Bin Lin
- Centre of Reproductive Medicine/Family Planning Research Institute, Tongji Medical College , Huazhong University of Science and Technology , Wuhan , Hubei 430030 , P.R. China.,State Key Laboratory of Environment Health (Incubation), Key Laboratory of Environment and Health, Ministry of Education, Key Laboratory of Environment and Health (Wuhan), Ministry of Environmental Protection, School of Public Health, Tongji Medical College , Huazhong University of Science and Technology , Hangkong Road #13 , Wuhan , Hubei 430030 , P.R. China
| | - Li Chen
- Centre of Reproductive Medicine/Family Planning Research Institute, Tongji Medical College , Huazhong University of Science and Technology , Wuhan , Hubei 430030 , P.R. China
| | - Na Li
- Centre of Reproductive Medicine/Family Planning Research Institute, Tongji Medical College , Huazhong University of Science and Technology , Wuhan , Hubei 430030 , P.R. China
| | - Jiaju Xu
- Centre of Reproductive Medicine/Family Planning Research Institute, Tongji Medical College , Huazhong University of Science and Technology , Wuhan , Hubei 430030 , P.R. China
| | - Jing Wang
- Key Laboratory of Agrifood Safety and Quality, Ministry of Agriculture of China, Institute of Quality Standards & Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing , 100081 , P.R. China
| | - Yuxiang Yang
- Centre of Reproductive Medicine/Family Planning Research Institute, Tongji Medical College , Huazhong University of Science and Technology , Wuhan , Hubei 430030 , P.R. China
| | - Yan Qi
- Key Laboratory of Agrifood Safety and Quality, Ministry of Agriculture of China, Institute of Quality Standards & Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing , 100081 , P.R. China
| | - Yongxin She
- Key Laboratory of Agrifood Safety and Quality, Ministry of Agriculture of China, Institute of Quality Standards & Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing , 100081 , P.R. China
| | - Xiantao Shen
- State Key Laboratory of Environment Health (Incubation), Key Laboratory of Environment and Health, Ministry of Education, Key Laboratory of Environment and Health (Wuhan), Ministry of Environmental Protection, School of Public Health, Tongji Medical College , Huazhong University of Science and Technology , Hangkong Road #13 , Wuhan , Hubei 430030 , P.R. China
| | - Xianjin Xiao
- Centre of Reproductive Medicine/Family Planning Research Institute, Tongji Medical College , Huazhong University of Science and Technology , Wuhan , Hubei 430030 , P.R. China
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A broad mercury resistant strain of Pseudomonas putida secretes pyoverdine under limited iron conditions and high mercury concentrations. Biometals 2016; 29:1097-1106. [PMID: 27848043 DOI: 10.1007/s10534-016-9980-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/28/2016] [Indexed: 10/20/2022]
Abstract
The Pseudomonas putida FB1, known as a broad-spectrum mercury resistant strain, becomes yellow-green due to the secretion of pyoverdine (PVDs) under limited iron conditions and high mercury concentrations. Different modified Nelson's media were obtained by adding mercury, iron, and the complexing agent nitrilotriacetic acid to demonstrate that the strain produces only the highest concentrations of PVDs due to the induction with 25 µM Hg2+. An amount of 250 mg PVDs was purified from the supernatant of 1 litre culture. The various forms of PVDs were characterized using different techniques such as fluorescence spectroscopy, high performance liquid chromatography coupled with high resolution mass spectrometry, and scanning electron microscope equipped with energy dispersive X-ray analyser. A set of "in vivo" experiments demonstrated that additions of Hg2+ to the cultures from 10 to 25 µM Hg2+ stimulate an over secretion of PVDs suggesting that the toxic cation strongly reduces the availability of apo-PVDs, because the complex mercuric-pyoverdine is very stable at neutral pH, and hinder the formation of PVDs-Fe(III).
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Yao XZ, Guo Z, Yuan QH, Liu ZG, Liu JH, Huang XJ. Exploiting differential electrochemical stripping behaviors of Fe3O4 nanocrystals toward heavy metal ions by crystal cutting. ACS APPLIED MATERIALS & INTERFACES 2014; 6:12203-12213. [PMID: 25014119 DOI: 10.1021/am501617a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
This study attempts to understand the intrinsic impact of different morphologies of nanocrystals on their electrochemical stripping behaviors toward heavy metal ions. Two differently shaped Fe3O4 nanocrystals, i.e., (100)-bound cubic and (111)-bound octahedral, have been synthesized for the experiments. Electrochemical results indicate that Fe3O4 nanocrystals with different shapes show different stripping behaviors toward heavy metal ions. Octahedral Fe3O4 nanocrystals show better electrochemical sensing performances toward the investigated heavy metal ions such as Zn(II), Cd(II), Pb(II), Cu(II), and Hg(II), in comparison with cubic ones. Specifically, Pb(II) is found to have the best stripping performance on both the (100) and (111) facets. To clarify these phenomena, adsorption abilities of as-prepared Fe3O4 nanocrystals have been investigated toward heavy metal ions. Most importantly, combined with theoretical calculations, their different electrochemical stripping behaviors in view of facet effects have been further studied and enclosed at the level of molecular/atom. Finally, as a trial to find a disposable platform completely free from noble metals, the potential application of the Fe3O4 nanocrystals for electrochemical detection of As(III) in drinking water is demonstrated.
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Affiliation(s)
- Xian-Zhi Yao
- Nanomaterials and Environmental Detection Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences , Hefei 230031, People's Republic of China
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Wan J, Yin G, Ma X, Xing L, Luo X. Highly Sensitive Electrochemiluminescence Detection of Mercury(II) Ions Based on DNA-Linked Luminol-Au NPs Superstructure. ELECTROANAL 2014. [DOI: 10.1002/elan.201300628] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Baldi F, Gallo M, Marchetto D, Faleri C, Maida I, Fani R. Manila clams from Hg polluted sediments of Marano and Grado lagoons (Italy) harbor detoxifying Hg resistant bacteria in soft tissues. ENVIRONMENTAL RESEARCH 2013; 125:188-196. [PMID: 23398778 DOI: 10.1016/j.envres.2012.11.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 11/17/2012] [Accepted: 11/27/2012] [Indexed: 06/01/2023]
Abstract
A mechanism of mercury detoxification has been suggested by a previous study on Hg bioaccumulation in Manila clams (Ruditapes philippinarum) in the polluted Marano and Grado lagoons and in this study we demonstrate that this event could be partly related to the detoxifying activities of Hg-resistant bacteria (MRB) harbored in clam soft tissues. Therefore, natural clams were collected in six stations during two different periods (winter and spring) from Marano and Grado Lagoons. Siphons, gills and hepatopancreas from acclimatized clams were sterile dissected to isolate MRB. These anatomical parts were glass homogenized or used for whole, and they were lying on a solid medium containing 5mgl(-1) HgCl2 and incubated at 30°C. A total of fourteen bacterial strains were isolated and were identified by 16S rDNA sequencing and analysis, revealing that strains were representative of eight bacterial genera, four of which were Gram-positive (Enterococcus, Bacillus, Jeotgalicoccus and Staphylococcus) and other four were Gram-negative (Stenotrophomonas, Vibrio, Raoultella and Enterobacter). Plasmids and merA genes were found and their sequences determined. Fluorescence in situ hybridization (FISH) technique shows the presence of Firmicutes, Actinobacteria and Gammaproteobacteria by using different molecular probes in siphon and gills. Bacterial clumps inside clam flesh were observed and even a Gram-negative endosymbiont was disclosed by transmission electronic microscope inside clam cells. Bacteria harbored in cavities of soft tissue have mercury detoxifying activity. This feature was confirmed by the determination of mercuric reductase in glass-homogenized siphons and gills.
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Affiliation(s)
- Franco Baldi
- Dipartimento di Scienze Molecolari e Nanosistemi, Cà Foscari University of Venice, Dorsoduro 2137, 30123 Venice, Italy.
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