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World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Friday, 31 August 2012

Just Published: Analytica Chimica Acta


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:

Intracellularly grown gold nanoislands as SERS substrates for monitoring chromate, sulfate and nitrate localization sites in remediating bacteria biofilms by Raman chemical imaging

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Sandeep P. Ravindranath, Ulhas S. Kadam, Dorothea K. Thompson, Joseph Irudayaraj
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Multiplex optical sensing with surface-enhanced Raman scattering: A critical review

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Laura Rodriguez-Lorenzo, Laura Fabris, Ramon A. Alvarez-Puebla
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Speciation of the bio-available iodine and bromine forms in edible seaweed by high performance liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Vanessa Romarís-Hortas, Pilar Bermejo-Barrera, Jorge Moreda-Piñeiro, Antonio Moreda-Piñeiro
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).

Graphical abstract

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Graphical abstract Highlights

► 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.

An electrochemical ascorbic acid sensor based on palladium nanoparticles supported on graphene oxide

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Geng-huang Wu, Yan-fang Wu, Xi-wei Liu, Ming-cong Rong, Xiao-mei Chen, Xi Chen
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 PdCl4 2− 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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Development of a simultaneous extraction and cleanup method for pyrethroid pesticides from indoor house dust samples

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Jeanette M. Van Emon, Jane C. Chuang
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Electromembrane extraction of zwitterionic compounds as acid or base: Comparison of extraction behavior at acidic and basic pHs

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Saeed Nojavan, Ahmad Pourahadi, Saied Saeed Hosseiny Davarani, Amin Morteza-Najarian, Mojtaba Beigzadeh Abbassi
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

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

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Paula Vera, Blanca Uliaque, Elena Canellas, Ana Escudero, Cristina Nerín
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Detoxification of organophosphate residues using phosphotriesterase and their evaluation using flow based biosensor

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Rupesh K. Mishra, George Istamboulie, Sunil Bhand, Jean-Louis Marty
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Analytical pyrolysis vs. classical wet chemical analysis to assess the decay of archaeological waterlogged wood

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Jeannette J. Łucejko, Magdalena Zborowska, Francesca Modugno, Maria P. Colombini, Włodzimierz Prądzyński
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Fluorescence enhancement of CdTe/CdS quantum dots by coupling of glyphosate and its application for sensitive detection of copper ion

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Zhengqing Liu, Shaopu Liu, Pengfei Yin, Youqiu He
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 2.4×10−2 μgmL−1 and 28μgmL−1, with a detection limit of 1.3×10−3 μgmL−1 (3δ). 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.

Graphical abstract

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Graphical abstract Highlights

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.
► 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.

Revision of iron(III)–citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Petra Vukosav, Marina Mlakar, Vladislav Tomišić
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 FeL2 5−, FeL2H4− and FeL2H2 3− 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 E p vs. pH and E p vs. [L4−] dependence. The UV–vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (log β =25.69), FeL2H2 3− (log β =48.06), FeL2H4− (log β =44.60), and FeL2 5− (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.

Graphical abstract

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Graphical abstract Highlights

► 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. ► log   β FeLH = 25.69 ,     log   β FeL 2 H 2 = 48.06 ,     log   β FeL 2 H = 44.60 ,     log   β FeL 2 = 38.85 .

Analytical procedure for the determination of Ethyl Lauroyl Arginate (LAE) to assess the kinetics and specific migration from a new antimicrobial active food packaging

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Davinson Pezo, Beatriz Navascués, Jesús Salafranca, Cristina Nerín
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)4 2− 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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Colloidal gold nanoparticle probe-based immunochromatographic assay for the rapid detection of chromium ions in water and serum samples

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Xi Liu, Jun-Jian Xiang, Yong Tang, Xiao-Li Zhang, Qiang-Qiang Fu, Jun-Hui Zou, YueHe Lin
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

A novel sensing platform using aptamer and RNA polymerase-based amplification for detection of cancer cells

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Jingjin Zhao, Liangliang Zhang, Chunfei Chen, Jianhui Jiang, Ruqin Yu
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 5.0×106 cellsmL−1 with a detection limit of 5.0×102 cellsmL−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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Intracellularly grown gold nanoislands as SERS substrates for monitoring chromate, sulfate and nitrate localization sites in remediating bacteria biofilms by Raman chemical imaging

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Sandeep P. Ravindranath, Ulhas S. Kadam, Dorothea K. Thompson, Joseph Irudayaraj
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Multiplex optical sensing with surface-enhanced Raman scattering: A critical review

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Laura Rodriguez-Lorenzo, Laura Fabris, Ramon A. Alvarez-Puebla
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.

Graphical abstract

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Graphical abstract Highlights

► 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.

Speciation of the bio-available iodine and bromine forms in edible seaweed by high performance liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Vanessa Romarís-Hortas, Pilar Bermejo-Barrera, Jorge Moreda-Piñeiro, Antonio Moreda-Piñeiro
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).

Graphical abstract

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Graphical abstract Highlights

► 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.

An electrochemical ascorbic acid sensor based on palladium nanoparticles supported on graphene oxide

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Geng-huang Wu, Yan-fang Wu, Xi-wei Liu, Ming-cong Rong, Xiao-mei Chen, Xi Chen
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 PdCl4 2− 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.

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► 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.

Development of a simultaneous extraction and cleanup method for pyrethroid pesticides from indoor house dust samples

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Jeanette M. Van Emon, Jane C. Chuang
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.

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► 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.

Electromembrane extraction of zwitterionic compounds as acid or base: Comparison of extraction behavior at acidic and basic pHs

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Saeed Nojavan, Ahmad Pourahadi, Saied Saeed Hosseiny Davarani, Amin Morteza-Najarian, Mojtaba Beigzadeh Abbassi
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.

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► 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.

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

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Paula Vera, Blanca Uliaque, Elena Canellas, Ana Escudero, Cristina Nerín
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.

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► 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.

Detoxification of organophosphate residues using phosphotriesterase and their evaluation using flow based biosensor

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Rupesh K. Mishra, George Istamboulie, Sunil Bhand, Jean-Louis Marty
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.

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► 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.

Analytical pyrolysis vs. classical wet chemical analysis to assess the decay of archaeological waterlogged wood

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Jeannette J. Łucejko, Magdalena Zborowska, Francesca Modugno, Maria P. Colombini, Włodzimierz Prądzyński
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.

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► 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.

Fluorescence enhancement of CdTe/CdS quantum dots by coupling of glyphosate and its application for sensitive detection of copper ion

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Zhengqing Liu, Shaopu Liu, Pengfei Yin, Youqiu He
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 2.4×10−2 μgmL−1 and 28μgmL−1, with a detection limit of 1.3×10−3 μgmL−1 (3δ). 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.

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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.
► 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.

Revision of iron(III)–citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Petra Vukosav, Marina Mlakar, Vladislav Tomišić
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 FeL2 5−, FeL2H4− and FeL2H2 3− 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 E p vs. pH and E p vs. [L4−] dependence. The UV–vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (log β =25.69), FeL2H2 3− (log β =48.06), FeL2H4− (log β =44.60), and FeL2 5− (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.

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► 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. ► log   β FeLH = 25.69 ,     log   β FeL 2 H 2 = 48.06 ,     log   β FeL 2 H = 44.60 ,     log   β FeL 2 = 38.85 .

Analytical procedure for the determination of Ethyl Lauroyl Arginate (LAE) to assess the kinetics and specific migration from a new antimicrobial active food packaging

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Davinson Pezo, Beatriz Navascués, Jesús Salafranca, Cristina Nerín
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)4 2− 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.

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► 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.

Colloidal gold nanoparticle probe-based immunochromatographic assay for the rapid detection of chromium ions in water and serum samples

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Xi Liu, Jun-Jian Xiang, Yong Tang, Xiao-Li Zhang, Qiang-Qiang Fu, Jun-Hui Zou, YueHe Lin
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.

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► 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.

A novel sensing platform using aptamer and RNA polymerase-based amplification for detection of cancer cells

31 August 2012, 09:00:08
Publication year: 2012
Source:Analytica Chimica Acta, Volume 745
Jingjin Zhao, Liangliang Zhang, Chunfei Chen, Jianhui Jiang, Ruqin Yu
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 5.0×106 cellsmL−1 with a detection limit of 5.0×102 cellsmL−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.

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► 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.