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Analytica Chimica Acta (v.745, #)
Intracellularly grown gold nanoislands as SERS substrates for monitoring chromate, sulfate and nitrate localization sites in remediating bacteria biofilms by Raman chemical imaging by Sandeep P. Ravindranath; Ulhas S. Kadam; Dorothea K. Thompson; Joseph Irudayaraj (pp. 1-9).
Display Omitted► A bioanalytical approach for the simultaneous analysis of chromate, sulfate and nitrate reduction is presented. ► The uptake of gold nanoislands by the bacterium cells using TEM and FLIM imaging. ► The study determines the simultaneous reduction of chromate, sulfate and nitrate at single-cell level using Raman chemical imaging. ► The chromate–sulfate, chromate–nitrate interactions, and chromate–sulfate competition in single bacterium.Understanding the chemical composition of biofilm matrices is vital in different fields of biology such as surgery, dental medicine, synthetic grafts and bioremediation. The knowledge of biofilm development, composition, active reduction sites and remediation efficacy will help in the development of effective solutions and evaluation of remediating approaches prior to implementation. Surface-enhanced Raman spectroscopy (SERS) based imaging is an invaluable tool to obtain an understanding of the remediating efficacy of microorganisms and its role in the formation of organic and inorganic compounds in biofilms. We demonstrate for the first time, the presence of chromate, sulfate, nitrate and reduced trivalent chromium in soil biofilms. In addition, we demonstrate that SERS imaging was able to validate two observations made by previous studies on chromate/sulfate and chromate/nitrate interactions in Shewanella oneidensis MR-1 biofilms. Additionally, we show a detailed Raman mapping based evidence of the existence of chromate–sulfate competition for cellular entry. Subsequently, we use Raman mapping to study the effect of nitrate on chromate reduction. The findings presented in this paper are among the first to report – detection of multiple metallic ions in bacterial biofilms using intracellular SERS substrates. Such a detailed characterization of biofilms using gold nanoislands based SERS mapping substrate can be extended to study cellular localization of other metallic ions and chemical species of biological and toxicological significance and their effect on reduction reactions in bacterial biofilms.
Keywords: Surface-enhanced Raman spectroscopy (SERS); Chemical imaging; Hexavalent chromate; Sulfate; Nitrate; Bioremediation; Shewanella oneidensis; MR-1
Multiplex optical sensing with surface-enhanced Raman scattering: A critical review by Laura Rodriguez-Lorenzo; Laura Fabris; Ramon A. Alvarez-Puebla (pp. 10-23).
Display Omitted► Multiplex SERS may be applied directly, but it is restricted due to the complexity of real samples. ► The SERS spectrum of a given probe is equivalent to a barcode of that chemical entity. ► The number of SERS codes is practically unlimited. ► Bioimaging with encoded SERS particles is one of the most promising approaches. ► SERS bioimaging has enabled the ratiometric quantification of cancerous vs. non-cancerous cells.Multiplex analysis permits the detection of several analytical targets at the same time. This approach may permit to draw a rapid and accurate diagnostic about the health of an individual or an environment. Among the analytical techniques with potential for multiplexing surface-enhanced Raman scattering (SERS) offer unique advantages such as ultrasensitive detection down low the deconvolution times, a unique signature containing all the vibrational information of the target molecules, and the possibility of performing the experiments even in very demanding environments such as natural or biological fluids. Here we review the late advances in multiplex SERS including the direct methods, those aided by the surface functionalization of the plasmonic nanoparticles and the use of SERS encoded particles.
Keywords: SERS; Multiplex; Plasmonics; Direct sensing; Encoded particles
Speciation of the bio-available iodine and bromine forms in edible seaweed by high performance liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry by Vanessa Romarís-Hortas; Pilar Bermejo-Barrera; Jorge Moreda-Piñeiro; Antonio Moreda-Piñeiro (pp. 24-32).
Display Omitted► Bioavailable iodine and bromine speciation in edible seaweed were developed. ► In vitro dialyzability was used to assess the bioavailable fractions. ► AEC hyphenated with inductively coupled plasma-mass spectrometry was used. ► Iodide, MIT, DIT, bromide and bromate were found in dialyzates from edible seaweed. ► Positive correlation between bioavailability and protein contents was found.A bioavailability study based on an in vitro dialyzability approach has been applied to assess the bio-available fractions of iodine and bromine species from edible seaweed. Iodide, iodate, 3-iodo-tyrosine (MIT), 3,5-diiodo-tyrosine (DIT), bromide and bromate were separated by anion exchange chromatography under a gradient elution mode (175mM ammonium nitrate plus 15% (v/v) methanol, pH 3.8, as a mobile phase, and flow rates within the 0.5–1.5mLmin−1 range). Inductively coupled plasma-mass spectrometry (ICP-MS) was used as a selective detector for iodine (127I) and bromine (79Br). Low dialyzability ratios (within the 2.0–18% range) were found for iodine species; whereas, moderate dialyzability percentages (from 9.0 to 40%) were obtained for bromine species. Iodide and bromide were the major species found in the dialyzates from seaweed, although MIT and bromate were also found in the dialyzates from most of the seaweed samples analysed. However, DIT was only found in dialyzates from Wakame, Kombu, and NIES 09 (Sargasso) certified reference material; whereas, iodate was not found in any dialyzate. Iodine dialyzability was found to be dependent on the protein content (negative correlation), and on the carbohydrate and dietary fibre levels (positive correlation). However, bromine dialyzability was only dependent on the protein amount in seaweed (negative correlation).
Keywords: Iodine; Bromine; Speciation; Seaweed; Dialyzability; In vitro; digestion; HPLC; ICP-MS
An electrochemical ascorbic acid sensor based on palladium nanoparticles supported on graphene oxide by Geng-huang Wu; Yan-fang Wu; Xi-wei Liu; Ming-cong Rong; Xiao-mei Chen; Xi Chen (pp. 33-37).
Display Omitted► PdNPs with a mean diameter of 2.6nm were homogeneously deposited on GO. ► The proposed sensor exhibited a rapid amperometric response to AA within 5s. ► Good selectivity, wide linear range, low detection limit for AA.In this study, an electrochemical ascorbic acid (AA) sensor was constructed based on a glassy carbon electrode modified with palladium nanoparticles supported on graphene oxide (PdNPs-GO). PdNPs with a mean diameter of 2.6nm were homogeneously deposited on GO sheets by the redox reaction between PdCl42− and GO. Cyclic voltammetry and amperometric methods were used to evaluate the electrocatalytic activity towards the oxidation of AA in neutral media. Compared to a bare GC or a Pd electrode, the anodic peak potential of AA (0.006V) at PdNPs-GO modified electrode was shifted negatively, and the large anodic peak potential separation (0.172V) of AA and dopamine (DA), which could contribute to the synergistic effect of GO and PdNPs, was investigated. A further amperometric experiment proved that the proposed sensor was capable of sensitive and selective sensing of AA even in the presence of DA and uric acid. The modified electrode exhibited a rapid response to AA within 5s and the amperometric signal showed a good linear correlation to AA concentration in a broad range from 20μM to 2.28mM with a correlation coefficient of R=0.9991. Moreover, the proposed sensor was applied to the determination of AA in vitamin C tablet samples. The satisfactory results obtained indicated that the proposed sensor was promising for the development of novel electrochemical sensing for AA determination.
Keywords: Ascorbic acid; Electrochemical sensor; Palladium nanoparticles; Graphene oxide
Development of a simultaneous extraction and cleanup method for pyrethroid pesticides from indoor house dust samples by Jeanette M. Van Emon; Jane C. Chuang (pp. 38-44).
Display Omitted► A selective pressurized liquid extraction (SPLE) method was developed for dust-bound pyrethroid residues. ► The SPLE compared favorably with a multi-step extraction and cleanup procedure. ► House dust samples from two exposure studies were analyzed using the SPLE method. ► The SPLE procedure could be applied to a large sample load generated by a monitoring study.An efficient and reliable analytical method was developed for the sensitive and selective quantification of pyrethroid pesticides (PYRs) in house dust samples. The method is based on selective pressurized liquid extraction (SPLE) of the dust-bound PYRs into dichloromethane (DCM) with analysis by gas chromatography/mass spectrometry. Various adsorbents and combinations of extraction solvents and temperatures were evaluated to achieve a high-throughput sample preparation that eliminates the post-extraction cleanup step. The final method used sulfuric acid-impregnated silica (acid silica) and neutral silica together in the extraction cell with the dust sample to provide both extraction and cleanup simultaneously. The optimal ratio of dust/acid silica/silica was 1:0.8:8. The extraction was performed at 2000psi, at 100°C with DCM for 5min in three cycles. Method precision and accuracy were evaluated by the analysis of triplicate aliquots of the dust samples and the samples fortified with the target PYRs. The accuracy measured as the recoveries of the PYRs in the fortified samples ranged from 85% to 120%. The precision measured as the relative standard deviation of replicate samples was within ±25%. The SPLE method was applied to 20 house dust samples collected from households that participated in two field studies regarding exposures to pesticides and other pollutants. Similar concentrations of target PYRs were obtained for the SPLE and a stepwise extraction/cleanup procedure. The SPLE procedure reduces organic solvent consumption and increases the sample throughput when compared with a traditional stepwise extraction and cleanup procedure. This study demonstrates that the SPLE procedure can be applied to complex dust matrices for analysis of PYRs for large scale exposure or environmental monitoring studies.
Keywords: Pyrethroid pesticides; Selective pressurized liquid extraction; SPLE; GC/MS; Indoor sampling; Dust
Electromembrane extraction of zwitterionic compounds as acid or base: Comparison of extraction behavior at acidic and basic pHs by Saeed Nojavan; Ahmad Pourahadi; Saied Saeed Hosseiny Davarani; Amin Morteza-Najarian; Mojtaba Beigzadeh Abbassi (pp. 45-52).
Display Omitted► This study has performed on electromembrane extraction of zwitterionic compounds. ► Zwitterionic compounds could be extracted from both acidic and basic solutions. ► Extraction efficiency of cationic species of CTZ was higher than anionic species. ► Position of charge within the CTZ was an effective parameter on the extraction. ► Chemistry of SLM solvent was important more than the magnitude of applied voltage.This study has performed on electromembrane extraction (EME) of some zwitterionic compounds based on their acidic and basic properties. High performance liquid chromatography (HPLC) equipped with UV detection was used for determination of model compounds. Cetirizine (CTZ) and mesalazine (MS) were chosen as model compounds, and each of them was extracted from acidic (as a cation) and basic (as an anion) sample solutions, separately. 1-Octanol and 2-nitrophenyl octylether (NPOE) were used as the common supported liquid membrane (SLM) solvents. EME parameters, such as extraction time, extraction voltage and pH of donor and acceptor solutions were studied in details for cationic and anionic forms of each model compound and obtained results for two ionic forms (cationic and anionic) of each compound were compared together. Results showed that zwitterionic compounds could be extracted in both cationic and anionic forms. Moreover, it was found that the extraction of anionic form of each model compound could be done in low voltages when 1-octanol was used as the SLM solvent. Results showed that charge type was not highly effective on the extraction efficiency of model compounds whereas the position of charge within the molecule was the key parameter. In optimized conditions, enrichment factors (EF) of 27–60 that corresponded to recoveries ranging from 39 to 86% were achieved.
Keywords: Abbreviations; CTZ; cetirizine; DEHP; di-(2-ethylhexyl) phosphate; EME; electromembrane extraction; EF; enrichment factor; HZ; hydroxyzine; MS; mesalazine; NPOE; 2-nitrophenyl octylether; SLM; supported liquid membraneElectromembrane extraction; Zwitterionic compounds; Charge type; Cetirizine; Mesalazine; Hydroxyzine; Sample preparation
Identification and quantification of odorous compounds from adhesives used in food packaging materials by headspace solid phase extraction and headspace solid phase microextraction coupled to gas chromatography–olfactometry–mass spectrometry by Paula Vera; Blanca Uliaque; Elena Canellas; Ana Escudero; Cristina Nerín (pp. 53-63).
Display Omitted► Off-odor in adhesives have been identified and analytical protocol has been established. ► Individual compounds responsable for off-odor have been separated, identified and quantified. ► SPE and HS-SPME are compared for extraction of odorous compounds. ► Five different types of adhesives in multilayer food packaging materials have been studied.Adhesives are often responsible for off-flavors in food in contact with packaging. The aim of this investigation was to identify by GC–O–MS the odorous compounds in five different types of adhesive (hotmelt, vinyl acetate ethylene, starch, polyvinyl acetate and acrylic) used in food packaging. In order to obtain a substantial number of compounds, they were extracted by two complementary extraction methods: HS-SPE and HS-SPME. Fifteen minutes extraction time using PDMS fiber for hotmelt adhesive and DVD/CAR/PDMS fiber for the other adhesives were the best conditions for defining a representative solvent-free adhesive extract using a rapid and simple D-GC–O technique. Thirty-three compounds were identified by GC–O–MS. These include butyric acid, acetic acid, methyl butyrate, 1-butanol and nonanal, which were present in most of the adhesives under study producing cheesy, rancid, sour, medicinal and green aromas, respectively. The concentrations were determined, the most abundant compound being acetic acid with concentrations from 22.9 to 8930μgg−1 of adhesive.
Keywords: Adhesives; Food packaging; Odor; Gas chromatography–olfactometry–mass spectrometry; Direct gas chromatography–olfactometry; Paper; Odor analysis
Detoxification of organophosphate residues using phosphotriesterase and their evaluation using flow based biosensor by Rupesh K. Mishra; George Istamboulie; Sunil Bhand; Jean-Louis Marty (pp. 64-69).
Display Omitted► Present work demonstrates the detoxification of OPs at low level. ► This is the first report of OPs detoxification in milk using PTE. ► PTE reacts rapidly with OPs and hydrolyzes within few minutes. ► Detoxification of OPs using PTE was evaluated using flow based biosensor.Among known pesticide groups, organophosphates (OPs) have grasped attention due to their hazardous nature and their applications as pesticides and chemical weapons. This work presents the development of cost-effective column based biosensor for detoxification of OPs in water and milk. Enzyme phosphotriesterase (PTE) was immobilized on an activated Sepharose 4B via covalent coupling using an Omnifit glass column. Three different OPs, ethyl paraoxon (EPOx), malaoxon (MAO) and chlorpyriphos-oxon (CPO) were spiked in water and milk to test the detoxification of OPs. Mixtures of these pesticides were also tested to check the cumulative detoxification in the real samples. The efficiency of detoxification was evaluated using a highly sensitive acetylcholinesterase (AChE) B394 biosensor based flow system. The column conditions were optimized for the detoxification studied. The method was shown to be promising when we tested real milk samples spiked with OPs. Detoxification obtained in milk was up to 86% whereas in water, 100% detoxification was obtained.
Keywords: Organophosphate; Detoxification; Phosphotriesterase; Water; Milk; Flow based biosensor
Analytical pyrolysis vs. classical wet chemical analysis to assess the decay of archaeological waterlogged wood by Jeannette J. Łucejko; Magdalena Zborowska; Francesca Modugno; Maria P. Colombini; Włodzimierz Prądzyński (pp. 70-77).
Display Omitted► We compare wet chemical analysis and Py(HMDS)–GC/MS in the characterisation of archaeological wood. ► We compare the two methods quantitatively. ► We evaluate the efficiency of Py(HMDS)–GC/MS in assessing the state of wood conservation. ► We characterise samples of waterlogged wood from the historical Żółte site in Poland.The macromolecular complexity of wood limits the possibility of obtaining complete chemical information on its alteration in archaeological objects. This paper compares the results obtained in the characterisation of the components of archaeological wood by a classical wet chemical method and by an instrumental method based on pyrolysis in presence of hexamethyldisilazane coupled with gas chromatography/mass spectrometry, Py(HMDS)–GC/MS. We compare the results obtained with the two methods quantitatively. This enables us to evaluate the efficiency of Py(HMDS)–GC/MS in assessing the chemical composition and the state of conservation of degraded wood. The material analysed consisted of reference sound wood and waterlogged wood from the Żółte historical site, located on a small island on Lake Zarańskie in Poland. The samples are from the remains of settlements dating to a period between the 9th and the 12th centuries AD.The results obtained by Py(HMDS)–GC/MS analysis are consistent in the determination of the level of degradation of archaeological wood with the results obtained using traditional techniques. The pyrolysis method is faster, reproducible, and reveals not only the amount but also the quality of the wood constituents, needing a much smaller sample.
Keywords: Waterlogged archaeological wood; Py–GC/MS; Classical wet analysis; Wood degradation
Fluorescence enhancement of CdTe/CdS quantum dots by coupling of glyphosate and its application for sensitive detection of copper ion by Zhengqing Liu; Shaopu Liu; Pengfei Yin; Youqiu He (pp. 78-84).
Glyphosate (Glyp) had been used to modify the surface of CdTe/CdS QDs, resulting in the enhancement of fluorescence intensity. The Glyp-functionalized QDs fluorescent probe offers good sensitivity and selectivity for detecting Cu2+ based on the fluorescence quenching.Display Omitted► Water soluble CdTe/CdS quantum dots capped with glyphosate were firstly synthesized. ► The fluorescence of the Glyp-functionalized QDs was quenched by copper ion. ► A new fluorescent sensor for copper ion was developed based on the prepared QDs. ► The sensor exhibited high sensitivity and good selectivity for copper ion.A novel fluorescent probe for Cu2+ determination based on the fluorescence quenching of glyphosate (Glyp)-functionalized quantum dots (QDs) was firstly reported. Glyp had been used to modify the surface of QDs to form Glyp-functionalized QDs following the capping of thioglycolic acid on the core–shell CdTe/CdS QDs. Under the optimal conditions, the response was linearly proportional to the concentration of Cu2+ between 2.4×10−2μgmL−1 and 28μgmL−1, with a detection limit of 1.3×10−3μgmL−1 (3 δ). The Glyp-functionalized QDs fluorescent probe offers good sensitivity and selectivity for detecting Cu2+. The fluorescent probe was successfully used for the determination of Cu2+ in environmental samples. The mechanism of reaction was also discussed.
Keywords: Quantum dots; Glyphosate; Fluorescence; Probe; Copper ion
Revision of iron(III)–citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies by Petra Vukosav; Marina Mlakar; Vladislav Tomišić (pp. 85-91).
Display Omitted► Combination voltammetry-spectophotometry best portrayed Fe–citrate speciation in aqueous solution. ► 4 redox processes of Fe(III)–citrate species were registered: at 0.1, −0.1, −0.28 and −0.4V. ► Biochemically most important Fe(III)–citrate mononuclear species, were described. ►logβFeLH=25.69,logβFeL2H2=48.06,logβFeL2H=44.60,logβFeL2=38.85.A detailed study of iron (III)–citrate speciation in aqueous solution ( θ=25°C, I c=0.7molL−1) was carried out by voltammetric and UV–vis spectrophotometric measurements and the obtained data were used for reconciled characterization of iron (III)–citrate complexes. Four different redox processes were registered in the voltammograms: at 0.1V (pH=5.5) which corresponded to the reduction of iron(III)–monocitrate species (Fe:cit=1:1), at about −0.1V (pH=5.5) that was related to the reduction of FeL25−, FeL2H4− and FeL2H23− complexes, at −0.28V (pH=5.5) which corresponded to the reduction of polynuclear iron(III)–citrate complex(es), and at −0.4V (pH=7.5) which was probably a consequence of Fe(cit)2(OH) x species reduction. Reversible redox process at −0.1V allowed for the determination of iron(III)–citrate species and their stability constants by analyzing Ep vs. pH and Ep vs. [L4−] dependence. The UV–vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (log β=25.69), FeL2H23− (log β=48.06), FeL2H4− (log β=44.60), and FeL25− (log β=38.85). The stability constants obtained by spectrophotometry were in agreement with those determined electrochemically. The UV–vis spectra recorded at various citrate concentrations (pH=2.0) supported the results of spectrophotometric–potentiometric titration.
Keywords: Iron(III); Citric acid; Voltammogram; Iron(III)–citrate complexes; UV–vis spectra; Stability constants
Analytical procedure for the determination of Ethyl Lauroyl Arginate (LAE) to assess the kinetics and specific migration from a new antimicrobial active food packaging by Davinson Pezo; Beatriz Navascués; Jesús Salafranca; Cristina Nerín (pp. 92-98).
Display Omitted► Ethyl Lauroyl Arginate (LAE) has been incorporated as antimicrobial agent into active food packaging materials. ► Ionic pair formation-based analytical methods have been developed and applied for LAE determination at mgkg−1 level. ► UV–Vis spectrophotometry and HPLC have been used. ► LAE stability and migration kinetics tests to aqueous food simulants have been assessed. ► One of the prototypes of active films is a very promising as antimicrobial active packaging for improving the shelf life of foodstuffs.Ethyl Lauroyl Arginate (LAE) is a cationic tensoactive compound, soluble in water, with a wide activity spectrum against moulds and bacteria. LAE has been incorporated as antimicrobial agent into packaging materials for food contact and these materials require to comply with the specific migration criteria. In this paper, one analytical procedure has been developed and optimized for the analysis of LAE in food simulants after the migrations tests. It consists of the formation of an ionic pair between LAE and the inorganic complex Co(SCN)42− in aqueous solution, followed by a liquid–liquid extraction in a suitable organic solvent and further UV–Vis absorbance measurement. In order to evaluate possible interferences, the ionic pair has been also analyzed by high performance liquid chromatography with UV–Vis detection. Both procedures provided similar analytical characteristics, with linear ranges from 1.10 to 25.00mgkg−1, linearity higher than 0.9886, limits of detection and quantification of 0.33 and 1.10mgkg−1, respectively, accuracy better than 1% as relative error and precision better than 3.6% expressed as RSD. Optimization of analytical techniques, thermal and chemical stability of LAE, as well as migration kinetics of LAE from experimental active packaging are reported and discussed.
Keywords: Ethyl Lauroyl Arginate; Antimicrobial; Active packaging; Specific migration analysis; Food simulant; Ionic pair
Colloidal gold nanoparticle probe-based immunochromatographic assay for the rapid detection of chromium ions in water and serum samples by Xi Liu; Jun-Jian Xiang; Yong Tang; Xiao-Li Zhang; Qiang-Qiang Fu; Jun-Hui Zou; YueHe Lin (pp. 99-105).
Display Omitted► An immunochromatography assay (ICA) is the first time applied for Cr detection. ► The ICA combine with a colorimetric reader is developed for quantification of Cr. ► The pretreatment helps to measure chromium speciation in water and serum samples.An immunochromatographic assay (ICA) using gold nanoparticles coated with monoclonal antibody (McAb) for the detection of chromium ions (Cr) in water and serum samples was developed, optimized and validated. Gold nanoparticles coated with affinity-purified monoclonal antibodies against isothiocyanobenzyl-EDTA (iEDTA)-chelated Cr3+ were used as the detecting reagent in this completive immunoassay-based one-step test strip. The ICA was investigated to measure chromium speciation (Cr3+ and Cr6+ ions) in water samples. Chromium standard samples of 0–80ngmL−1 in water were determined by the test strips. The results showed that the visual lowest detection limit (LDL) of the test strip was 50.0ngmL−1. A portable colorimetric lateral flow reader was used for the quantification of Cr. The results indicated that the linear range of the ICA with colorimetric detection was 5–80ngmL−1. The ICA was also validated for the detection of chromium ions in serum samples. The test trips showed high stability in that they could be stored at 37°C for at least 12 weeks without significant loss of activity. The test strip also showed good selectivity for Cr detection with negligible interference from other heavy metals. Because of its low cost and short testing time (within 5min), the test strip is especially suitable for on-site large-scale screening of Cr-polluted water samples, biomonitoring of Cr exposure, and many other field applications.
Keywords: Chromium ions; Gold nanoparticle; Immunochromatography assay; Rapid test; Quantification
A novel sensing platform using aptamer and RNA polymerase-based amplification for detection of cancer cells by Jingjin Zhao; Liangliang Zhang; Chunfei Chen; Jianhui Jiang; Ruqin Yu (pp. 106-111).
Display Omitted► The sensor used aptamer for target cell recognition. ► This sensor used RNA polymerase-based isothermal amplification method. ► This sensing platform also performed a satisfactory result in the cell media. ► This method can be further expanded to screen more kinds of tumor cells by altering the related aptamers. ► The sensor is high sensitivity, excellent selectivity and small volume of sample.Cancer is one of the most serious and lethal diseases around the world. Its early detection has become a challenging goal. To address this challenge, we developed a novel sensing platform using aptamer and RNA polymerase-based amplification for the detection of cancer cells. The assay uses the aptamer as a capture probe to recognize and bind the tumor marker on the surface of the cancer cells, forming an aptamer-based sandwich structure for collection of the cells in the microplate wells, and uses SYBR Green II dye as a tracer to produce strong fluorescence signal. The tumor marker interacts first with the recognition probes which were composed of the aptamer and single-stranded T7 RNA polymerase promoter. Then, the recognition probe hybridized with template probes to form a double-stranded T7 RNA polymerase promoter. This dsDNA region is extensively transcribed by T7 RNA polymerase to produce large amounts of RNAs, which are easily monitored using the SYBR Green II dye and a standard fluorometer, resulting in the amplification of the fluorescence signal. Using MCF-7 breast cancer cell as the model cell, the present sensing platform showed a linear range from 5.0×102 to 5.0×106cellsmL−1 with a detection limit of 5.0×102cellsmL−1. This work suggested a strategy to use RNA signal amplification combining aptamer recognition to develop a highly sensitive and selective method for cancer cells detection.
Keywords: Sensing platform; Cancer cells; Aptamer; RNA polymerase-based amplification
A novel nonenzymatic sensor based on LaNi0.6Co0.4O3 modified electrode for hydrogen peroxide and glucose by Zhen Zhang; Shuqing Gu; Yaping Ding; Jindi Jin (pp. 112-117).
CVs recorded on the bare CPE (a) and LNC/CPE (c) with 0.3mM H2O2, LNC/CPE (b) without H2O2 in 0.1M NaOH. Scan rate: 100mVs−1.Display Omitted► The sensor exhibited wide linear range and low detection limit. ► The sensor possesses high sensitivity and fast response. ► The sensor was used for detection of hydrogen peroxide and glucose. ► The proposed sensor has good stability and reproducibility. ► The sensor was applied in toothpaste and serum samples with satisfactory results.In this paper, LaNi0.6Co0.4O3 (LNC) nanoparticles were synthesized by the sol–gel method, and the structure and morphology of LNC nanoparticles were characterized by X-ray diffraction spectrum, scanning electron microscopy and transmitting electron microscopy. And then, LNC was used to modify carbon paste electrode (CPE) without any adhesive to fabricate hydrogen peroxide and glucose sensor, and the results demonstrated that LNC exhibited strong electrocatalytical activity by cyclic voltammetry and amperometry. In H2O2 determination, linear response was obtained in the concentration range of 10nM–100μM with a detection limit of 1.0nM. In glucose determination, there was the linear region of 0.05–200μM with a detection limit of 8.0nM. Compared with other reports, the proposed sensor also displayed high sensitivity toward H2O2 (1812.84μAmM−1cm−2) and glucose (643.0μAmM−1cm−2). Moreover, this prepared sensor was applied to detect glucose in blood serum and hydrogen peroxide in toothpaste samples with satisfied results, indicating its possibility in practical application.
Keywords: Electrocatalysis; Nonenzymatic; LaNi; 0.6; Co; 0.4; O; 3; Hydrogen peroxide; Glucose
Tracking growth hormone abuse in sport: Performance of marker proteins in a controlled setting by J. Bosch; G. Such-Sanmartín; J. Segura; R. Gutiérrez-Gallego (pp. 118-123).
Display Omitted► Detection of recombinant human growth hormone abuse in sport. ► Protein markers (insulin-like growth factor I (IGF-I) and procollagen type III N-terminal propeptide (P-III-NP)). ► Final validation with a dedicated human clinical trial.Human growth hormone (hGH) abuse in sport is a challenge at present. The current strategy used, known as direct method, is based on the quantification of hGH variants in serum. An alternative strategy, known as indirect method, focuses on serum markers such as insulin-like growth factor I (IGF-I) and procollagen type III N-terminal propeptide (P-III-NP). The indirect method allows a longer window of detection (WOO) of hGH abuse. To evaluate the performance of the indirect method, in parallel to the direct method, a clinical trial with recombinant hGH (rhGH) was conducted on healthy male subjects during 7 days (0.026mg−1kg−1person−1day−1). The data were fit to the discriminant formula proposed in the previously published GH-2000 project. The low sensitivity of the scores, judged from the high number of false negative outcomes, imposed a new discriminant analysis, standarised using local population subjects demographically similar to the ones of the study. The sensitivity of the method significantly increased, highlighting the importance of the standardisation. The indirect method allowed extended window of opportunity (WOO), although two false positive evaluations were observed derived from elevated basal IGF-I and P-III-NP concentrations stressing the need for an independent confirmation method. When direct and indirect methods were combined the best selectivity and sensitivity were achieved.
Keywords: Growth hormone; Isoform; Marker proteins; Immunoassay; Doping
Catalytic gold nanoparticles for fluorescent detection of mercury(II) and lead(II) ions by Chen-I Wang; Chih-Ching Huang; Yang-Wei Lin; Wen-Tsen Chen; Huan-Tsung Chang (pp. 124-130).
Display Omitted► A fluorescence assay for the highly sensitive and selective detection of Hg2+ and Pb2+ ions using gold nanoparticles (Au NPs)-based probe has been developed. ► The Hg–Au and Pb–Au alloys formed on the Au NP surfaces possess peroxidase-mimic catalytic activity for H2O2-mediated oxidation of Amplex UltraRed (AUR). ► The limits of detection (S/N=3) for Hg2+ and Pb2+ ions are both 4.0nM. ► The practicality of this assay has been assessed by determination of Hg2+ and Pb2+ ions from water and blood samples.In this study, we developed a fluorescence assay for the highly sensitive and selective detection of Hg2+ and Pb2+ ions using a gold nanoparticle (Au NP)-based probe. The Hg–Au and Pb–Au alloys that formed on the Au NP surfaces allowed the Au NPs to exhibit peroxidase-mimicking catalytic activity in the H2O2-mediated oxidation of Amplex UltraRed (AUR). The fluorescence of the AUR oxidation product increased upon increasing the concentration of either Hg2+ or Pb2+ ions. By controlling the pH values of 5mM tris–acetate buffers at 7.0 and 9.0, this H2O2–AUR–Au NP probe detected Hg2+ and Pb2+ ions, respectively, both with limits of detection (signal-to-noise ratio: 3) of 4.0nM. The fluorescence intensity of the AUR oxidation product was proportional to the concentrations of Hg2+ and Pb2+ ions over ranges 0.05–1μM ( R2=0.993) and 0.05–5μM ( R2=0.996), respectively. The H2O2–AUR–Au NP probe was highly selective for Hg2+ (>100-fold) and Pb2+ (>300-fold) ions in the presence of other tested metal ions. We validated the practicality of this simple, selective, and sensitive H2O2–AUR–Au NP probe through determination of the concentrations of Hg2+ and Pb2+ ions in a lake water sample and of Pb2+ ions in a blood sample. To the best of our knowledge, this system is the first example of Au NPs being used as enzyme-mimics for the fluorescence detection of Hg2+ and Pb2+ ions.
Keywords: Enzyme mimics; Fluorescence; Gold nanoparticles; Mercury; Lead
Ultrasensitive photoelectrochemical sensing of nicotinamide adenine dinucleotide based on graphene-TiO2 nanohybrids under visible irradiation by Kun Wang; Jun Wu; Qian Liu; Yicong Jin; Jiajia Yan; Jianrong Cai (pp. 131-136).
Display Omitted► The photoelectrochemical behavior of G-TiO2/GCE was investigated in visible region. ► The G-TiO2/GCE possessed enhanced photocurrent than pure TiO2 nanocrystals. ► A photoelectrochemical sensor for ultrasensitive determination of NADH was proposed. ► The proposed sensor showed linear range of 1.0×10−8 to 2.0×10−3M for NADH detection. ► This strategy largely reduces the destructive effect of UV light to biomolecules.In this paper, the photoelectrochemical behavior of graphene-TiO2 (G-TiO2) nanohybrids was investigated in the visible region and a new photoelectrochemical sensor for sensitive determination of nicotinamide adenine dinucleotide (NADH) was proposed. Under visible light, the G-TiO2 nanohybrids possessed enhanced photocurrent, which was nearly 5 times than that of pure TiO2 nanocrystals (NCs). Based on the enhanced photocurrent of G-TiO2 nanohybrids toward NADH, a new photoelectrochemical methodology for ultrasensitive determination of NADH was developed. The proposed sensor showed linearly enhanced photocurrent by increasing the NADH concentration from 1.0×10−8 to 2.0×10−3M with a low detection limit of 3.0×10−9M. Furthermore, this sensor exhibited good selectivity and stability towards NADH determination. This strategy opens up a new avenue for the application of graphene-based hybrids in the field of photoelectrochemical sensing and monitoring.
Keywords: Photoelectrochemical sensor; Graphene-TiO; 2; nanohybrids; NADH determination
Highly sensitive luminol electrochemiluminescence immunosensor based on ZnO nanoparticles and glucose oxidase decorated graphene for cancer biomarker detection by Yinfeng Cheng; Ruo Yuan; Yaqin Chai; Huan Niu; Yaling Cao; Huijing Liu; Lijuan Bai; Yali Yuan (pp. 137-142).
Display Omitted► In this paper, a novel sandwiched immunosensor has been developed. ► Electrochemiluminescence of luminol was enhanced by ZnO nanoparticles. ► This method was first used for construction of immunosensor. ► Glucose oxidase was used to label the second antibodies for generating H2O2 in situ. ► Graphene was used to load more second antibodies and ZnO nanoparticles.In this work, we reported a sandwiched luminol electrochemiluminescence (ECL) immunosensor using ZnO nanoparticles (ZnONPs) and glucose oxidase (GOD) decorated graphene as labels and in situ generated hydrogen peroxide as coreactant. In order to construct the base of the immunosensor, a hybrid architecture of Au nanoparticles and graphene by reduction of HAuCl4 and graphene oxide (GO) with ascorbic acid was prepared. The resulted hybrid architecture modified electrode provided an excellent platform for immobilization of antibody with good bioactivity and stability. Then, ZnONPs and GOD functionalized graphene labeled secondary antibody was designed for fabricating a novel sandwiched ECL immunosensor. Enhanced sensitivity was obtained by in situ generating hydrogen peroxide with glucose oxidase and the catalysis of ZnONPs to the ECL reaction of luminol–H2O2 system. The as-prepared ECL immunosensor exhibited excellent analytical property for the detection of carcinoembryonic antigen (CEA) in the range from 10pgmL−1 to 80ngmL−1 and with a detection limit of 3.3pgmL−1 (SN−1=3). The amplification strategy performed good promise for clinical application of screening of cancer biomarkers.
Keywords: Electrochemiluminescence; Glucose oxidase; Immunosensor; ZnO nanoparticles; Carcinoembryonic antigen
Fluorescence assay of catecholamines based on the inhibition of peroxidase-like activity of magnetite nanoparticles by Cheng-Hao Liu; Cheng-Ju Yu; Wei-Lung Tseng (pp. 143-148).
We developed a novel method for the fluorescence sensing of catecholamines based on the inhibition of Fe3O4 NP-catalyzed oxidation of Amplex UltraRed in the presence of H2O2.Display Omitted► Catecholamine can inhibit the peroxidase-like activity of Fe3O4 nanoparticles. ► This is first example of the quantification of dopamine using Fe3O4 nanoparticles. ► This probe provided high sensitivity toward catecholamines (LOD=3–6nM). ► The probe provided >1000-fold selectivity toward catecholamines. ► This probe can be applied to the determination of catecholamines in urine.We report a fluorescence approach for the highly selective and sensitive detection of catecholamines using magnetite nanoparticles (Fe3O4 NPs) in the presence of Amplex UltraRed (AUR) and H2O2. Fe3O4 NPs catalyze H2O2-mediated oxidation of AUR. The resulting product fluoresces (excitation/emission maxima, ca. 568/587nm) more strongly, relative to AUR. When catecholamines bind to Fe3O4, the complexes that are formed induce decreased activity of Fe3O4 NPs, mediated through the coordination between Fe3+ on the NP surface and the catechol moiety of catecholamines. As a result, Fe3O4 NPs-catalyzed H2O2-mediated oxidation of AUR is inhibited by catecholamines. The limits of detection for dopamine (DA),l-DOPA, norepinephrine, and epinephrine were 3nM, 3nM, 3nM, and 6nM, respectively. The Fe3O4 NPs-H2O2-AUR probe exhibited high selectivity (>1000-fold) toward catecholamines over other tested biomolecules that commonly exist in urine. Four catecholamines had similar sensitivity because the inhibition of the Fe3O4 NPs activity relies on the presence of the catechol moiety. This approach also allowed the determination of tyrosinase activity because tyrosinase catalyzes the conversion ofl-tyrosine tol-DOPA. We validated the practicality of the use of the Fe3O4 NPs-H2O2-AUR probe for the determination of the concentrations of DA in urine samples.
Keywords: Magnetite nanoparticles; Dopamine; Fluorescence; Amplex UltraRed; Catechol moiety
Determination of nitrocellulose by capillary electrophoresis with laser-induced fluorescence detection by M Ángeles Fernández de la Ossa; Mercedes Torre; Carmen García-Ruiz / (pp. 149-155).
Display Omitted► Development of the first method to determine nitrocellulose by capillary electrophoresis. ► Application of the method to the determination of nitrocellulose contained in gunpowder and collodion samples. ► Visual discrimination of highly and lowly nitrated nitrocellulose samples on the basis of the electrophoretic profiles. ► An in-capillary preconcentration strategy allowed to determine nitrocellulose contained in ∼15μg of gunpowder.The industrial application of nitrocellulose depends on its nitrogen content. When nitrocellulose presents high nitrogen content is used in the manufacture of explosives whereas nitrocellulose with low nitrogen content is used to make a wide range of daily and non-explosive products (e.g. cigarettes, paints, lacquers). This fact makes really important to develop a method for the determination and discrimination of nitrocellulose samples. This work reports, for the first time, the qualitative determination of nitrocellulose previously derivatized with 8-aminopyrene-1,3,6-trisulfonic acid (APTS) by capillary electrophoresis (CE-LIF) with laser-induced fluorescence detection (CE-LIF). APTS-labeled nitrocellulose was determined in lowly and highly nitrated nitrocellulose samples present in collodions and smokeless gunpowders, respectively, after their pulverization in liquid nitrogen. The method described enables the visual discrimination of different nitrocelluloses on the basis of the different electrophoretic profiles obtained, and provides a useful tool to determine nitrocellulose. Additionally, the use of field-amplified sample injection (FASI) enabled enhanced sample detection, which made it possible to determine nitrocellulose contained in ∼15μg of gunpowder.
Keywords: Nitrocellulose; APTS; Smokeless Gunpowder; Collodion; Explosives; Capillary electrophoresis