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1.
Sensors (Basel) ; 18(10)2018 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-30347779

RESUMO

Simple, robust, and low-cost nitrate- and ammonium-selective electrodes were made using substrate prepared from household materials. We explored phosphonium-based ILs and poly (methyl methacrylate)/poly(decyl methacrylate)(MMA-DMA) copolymer as matrix materials alternative to classical PVC-based membranes. IL-based membranes showed suitability only for nitrate-selective electrode exhibiting linear concentration range between 5.0 × 10-6 and 2.5 × 10-3 M with a detection limit of 5.5 × 10-7 M. On the other hand, MMA-DMA-based membranes showed suitability for both ammonium- and nitrate-selective electrodes, and were successfully applied to detect NO3- and NH4⁺ in water and soil samples. The proposed ISEs exhibited near-Nernstian potentiometric responses to NO3- and NH4⁺ with the linear range concentration between 5.0 × 10-5 and 5.0 × 10-2 M (LOD = 11.3 µM) and 5.0 × 10-6 and 1.0 × 10-3 M (LOD = 1.2 µM), respectively. The power of ISEs to detect NO3- and NH4⁺ in water and soils was tested by comparison with traditional, portable colorimetric techniques. Procedures required for analysis by each technique from the perspective of a non-trained person (e.g., farmer) and the convenience of the use on the field are compared and contrasted.

2.
Talanta ; 188: 658-664, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30029427

RESUMO

This article reports the detection of Salmonella spp. based on M13 bacteriophage in a capacitive flow injection system. Salmonella-specific M13 bacteriophage was immobilized on a polytyramine/gold surface using glutaraldehyde as a crosslinker. The M13 bacteriophage modified electrode can specifically bind to Salmonella spp. via the amino acid groups on the filamentous phage. An alkaline solution was used to break the binding between the sensing surface and the analyte to allow renewable use up to 40 times. This capacitive system provided good reproducibility with a relative standard deviation (RSD) of 1.1%. A 75 µL min-1 flow rate and a 300 µL sample volume provided a wide linear range, from 2.0 × 102 to 1.0 × 107 cfu mL-1, with a detection limit of 200 cfu mL-1. Bacteria concentration can be analyzed within 40 min after the sample injection. When applied to test real samples (raw chicken meat) it provided good recoveries (100-111%). An enrichment process was also explored to increase the bacteria concentration, enabling a quantitative detection of Salmonella spp. This biosensor opens a new opportunity for the detection of pathogenic bacteria using bacteriophage.


Assuntos
Carga Bacteriana/métodos , Bacteriófago M13/fisiologia , Técnicas Biossensoriais/métodos , Salmonella/isolamento & purificação , Sequência de Aminoácidos , Animais , Bacteriófago M13/química , Galinhas/microbiologia , Técnicas Eletroquímicas/métodos , Eletrodos , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Ouro/química , Limite de Detecção , Peptídeos/química , Reprodutibilidade dos Testes , Salmonella/química , Ligação Viral
3.
Biosens Bioelectron ; 102: 217-225, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29149687

RESUMO

A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nucleic acid (acpcPNA)/polypyrrole (PPy)/silver nanofoam (AgNF) modified electrode. The AgNF was electrodeposited as redox indicator on a gold electrode, which was then functionalized with an electropolymerized layer of PPy, a conducting polymer, to immobilize the PNA probes. The fabrication process was investigated by electrochemical impedance spectroscopy. The biosensor was used to detect miRNA-21, a biomarker abnormally expressed in most cancers. The signal was monitored by the change in current of the AgNF redox reaction before and after hybridization using cyclic voltammetry. Two PNA probe lengths were investigated and the longer probe exhibited a better performance. Nucleotide overhangs on the electrode side affected the signal more than overhangs on the solution side due to the greater insulation of the sensing surface. Under optimal conditions, the electrochemical signal was proportional to miRNA-21 concentrations between 0.20fM and 1.0nM, with a very low detection limit of 0.20fM. The biosensor showed a high specificity which could discriminate between complementary, single-, doubled-base mismatched, and non-complementary targets. Three out of the seven tested plasma samples provided detectable concentrations (63 ± 4, 111 ± 4 and 164 ± 7fM). The sensor also showed good recoveries (81-119%). The results indicated the possibilities of this biosensor for analysis without RNA extraction and/or amplification, making the sensor potentially useful for both the prognosis and diagnosis of cancer in clinical application.


Assuntos
Técnicas Biossensoriais , Técnicas Eletroquímicas , MicroRNAs/isolamento & purificação , Hibridização de Ácido Nucleico/genética , Espectroscopia Dielétrica , Ouro/química , Humanos , Limite de Detecção , MicroRNAs/genética , Neoplasias/diagnóstico , Neoplasias/genética , Polímeros/química , Pirróis/química , Pirrolidinas/química , Prata
4.
Biosens Bioelectron ; 96: 84-88, 2017 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-28463740

RESUMO

A simple renewable surface for a rapid antibacterial susceptibility test has been demonstrated. The 3-aminophenylboronic acid (3-APBA) modified electrode bind with cis-diol groups on the cell wall of both gram positive and gram negative bacteria. The detection of antibacterial susceptibility response by a capacitive system can be done within a short time, 2.5h for the whole process, with good repeatability of the electrode's preparation. An acid solution, could break the bonding between 3-APBA and the bacteria, which were then easily removed by the fluid flow, renewing the sensing surface for the next test. This modified electrode can be reused up to 35 times. This sensor is useful for testing the susceptibility of bacteria to antibacterial agents that affect their cell wall. Results from the capacitive sensor corresponded well with the antimicrobial information in the literature and to the morphology of the treated bacteria revealed by scanning electron microscopy. Antimicrobial susceptibility to natural products could also be easily tested.


Assuntos
Antibacterianos/farmacologia , Ampicilina/farmacologia , Técnicas Biossensoriais , Ácidos Borônicos/farmacologia , Ceftriaxona/farmacologia , Técnicas Eletroquímicas , Eletrodos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície , Tetraciclina/farmacologia , Vancomicina/farmacologia , Xantonas/farmacologia
5.
Biosens Bioelectron ; 85: 743-750, 2016 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-27266659

RESUMO

A simple and selective colorimetric sensor for sialic acid detection, based on the aggregation of 4-mercaptophenylboronic acid functionalized gold nanoparticles (4-MPBA-AuNPs) was developed. The color of the solution changed from wine-red to blue after binding with sialic acid. The colorimetric sensor provided good analytical performances with a linear dynamic range of 80µM to 2.00mM and a 68±2µM limit of detection without any effect from possible interferences and sample matrix. In addition, the quantitative results were obtained within only 10min. This developed sensor was used to detect sialic acid in blood serum samples and the results were in good agreement with those from the current periodate-resorcinol method (P>0.05) thus indicating that this developed colorimetric sensor can be used as an alternative method for sialic acid detection with a shorter analysis time and a high accuracy.


Assuntos
Ácidos Borônicos/química , Colorimetria/métodos , Ouro/química , Nanopartículas Metálicas/química , Ácido N-Acetilneuramínico/sangue , Compostos de Sulfidrila/química , Técnicas Biossensoriais/métodos , Humanos , Limite de Detecção , Nanopartículas Metálicas/ultraestrutura
6.
Biosens Bioelectron ; 82: 99-104, 2016 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-27054813

RESUMO

A highly sensitive label-free DNA biosensor based on PNA probes immobilized on a gold electrode was used to detect a hybridization event. The effect of a target DNA overhang on the hybridization efficiency was shown to enhance the detected signal and allowed detection at a very low concentration. The sensors performances were investigated with a complementary target that had the same length as the probe, and the signal was compared to the target DNAs with different lengths and overhangs. A longer target DNA overhang was found to provide a better response. When the overhang was on the electrode side the signal enhancement was greater than when the overhang was on the solution side due to the increased thickness of the sensing surface, hence produced a larger capacitance change. Using conformationally constrained acpcPNA probes, double stranded DNA was detected sensitively and specifically without any denaturing step. When two acpcPNA probes were applied for the screening test for the double stranded HLA-B*58:01 and HLA-B*57:01 genes that are highly similar, the method differentiated the two genes in all samples. Both purified and unpurified PCR products gave comparable results. This method would be potentially useful as a rapid screening test without the need for purification and denaturation of the PCR products.


Assuntos
Técnicas Biossensoriais/métodos , DNA/genética , Antígenos HLA-B/genética , Sequência de Bases , DNA/análise , Capacitância Elétrica , Humanos , Hibridização de Ácido Nucleico/métodos , Sondas de Ácido Nucleico/química , Sondas de Ácido Nucleico/genética , Ácidos Nucleicos Peptídicos/química , Ácidos Nucleicos Peptídicos/genética
7.
Bioelectrochemistry ; 101: 106-13, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25203453

RESUMO

Tissue inflammation, certain cardiovascular syndromes and the occurrence of some solid tumors are correlated with raised serum concentrations of human chitinase-3-like protein 1 (YKL-40), a mammalian chitinase-like glycoprotein, which has become the subject of current research. Here we report the construction and characterization of an electrochemical platform for label-free immunosensing of YKL-40. Details of the synthesis of YKL-40 and production of anti-YKL-40 immunoglobulin G (IgG) are provided and cross-reactivity tests presented. Polyclonal anti-YKL-40 IgG was immobilized on gold electrodes and the resulting immunosensors were operated in an electrochemical flow system with capacitive signal generation. The strategy offered a wide linear detection range (0.1µg/L to 1mg/L) with correlation coefficients (R(2)) above 0.99 and good sensitivity (12.28±0.27nF/cm(2) per decade of concentration change). Additionally, the detection limit of 0.07±0.01µg/L was well below that of optical enzyme-linked immunosorbent assays (ELISAs), which makes the proposed methodology a promising alternative for YKL-40 related disease studies.


Assuntos
Adipocinas/análise , Técnicas Eletroquímicas/métodos , Imunoensaio/métodos , Lectinas/análise , Adipocinas/sangue , Adipocinas/genética , Adipocinas/imunologia , Animais , Biomarcadores/análise , Calibragem , Proteína 1 Semelhante à Quitinase-3 , Reações Cruzadas , Técnicas Eletroquímicas/instrumentação , Eletrodos , Feminino , Ouro/química , Humanos , Imunoensaio/instrumentação , Imunoglobulina G/imunologia , Lectinas/sangue , Lectinas/genética , Lectinas/imunologia , Limite de Detecção , Coelhos , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia
8.
Anal Chim Acta ; 853: 521-532, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25467499

RESUMO

For the first time, a simple and highly sensitive label-free electrochemical carcinoembryonic antigen (CEA) immunosensor based on a cryogel electrode has been developed and tested. The as-prepared nanocomposite combined the advantages of the graphene, AuNPs and chitosan (AuNPs-GP-CS) together with the ease of preparing a cryogel coupled to a silver deposition, to act as a redox mediator, on a Au electrode. Under the optimal conditions, the decrease of the cyclic voltammetry (CV) silver peak current was proportional to the CEA concentration over a range of from 1.0×10(-6) to 1.0 ng mL(-1) with a detection limit of 2.0×10(-7) ng mL(-1). This AuNPs-GP-CS cryogel electrode gave a 1.7 times higher sensitivity and 25 times lower detection limit than the non-cryogel electrode. Moreover, the proposed electrochemical immunosensor exhibited good selectivity, reproducibility and stability. When applied to analyse clinical serum samples, the data determined by the developed immunosensor were in agreement with those obtained by the current hospital analysis system (enzyme linked fluorescent assay) (P>0.05), to indicate that the immunosensor would be potentially useful for clinical diagnostics.


Assuntos
Técnicas Biossensoriais , Antígeno Carcinoembrionário/sangue , Criogéis/química , Técnicas Eletroquímicas , Nanocompostos/química , Quitosana/química , Espectroscopia Dielétrica , Eletrodos , Ouro/química , Grafite/química , Humanos , Imunoensaio , Nanopartículas Metálicas/química , Oxirredução
9.
Analyst ; 139(23): 6160-7, 2014 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-25306849

RESUMO

A novel highly sensitive and selective molecularly imprinted polymer (MIP) cryogel biosensor for determination of microalbumin in urine samples was fabricated. The MIP gel was prepared based on the graft copolymerization of acrylamide with N,N'-methylenebisacrylamide on chitosan using human serum albumin (HSA) as the template. The sub-zero polymerization allowed the solvent to form ice crystals and left a macroporous cryogel structure when it was thawed. After removing the template, the specific imprinted surface on cryogel pore walls was used to detect HSA via a redox mediator (ferrocene), entrapped in the cryogel, using differential pulse voltammetry (DPV). The electrochemical detection was improved by the presence of graphene that has been composited within the polymer. For determination of albumin, the fabricated MIP cryogel biosensor showed a high sensitivity with a wide linear range of 1.0 × 10(-4) to 1.0 × 10(1) mg L(-1) and a low limit of detection of 5.0 × 10(-5) mg L(-1) (S/N = 3). The sensor also provided a very good reusability, i.e., the sensitivity remained >90% after 9 cycles of binding-rewashing (18 analyses per cycle), while the sensitivity only decreased to 90% after 6 weeks of storage at room temperature. The biosensor also showed a good selectivity, both against bovine serum albumin (BSA) and some common possible interfering compounds normally present in urine (ascorbic acid, uric acid, urea, sodium, chloride, potassium and creatinine). The excellent performance of the biosensor was confirmed by analyzing microalbumin in urine samples, and results were in good agreement with those obtained by the standard immunoturbidimetric method (P > 0.05).


Assuntos
Acrilamida/química , Técnicas Biossensoriais/métodos , Quitosana/química , Compostos Ferrosos/química , Grafite/química , Albumina Sérica/química , Criogéis/química , Humanos , Metalocenos , Microscopia Eletrônica de Varredura
10.
Anal Bioanal Chem ; 406(15): 3763-72, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24718436

RESUMO

A novel amperometric uric acid biosensor was fabricated by immobilizing uricase on an electrospun nanocomposite of chitosan-carbon nanotubes nanofiber (Chi-CNTsNF) covering an electrodeposited layer of silver nanoparticles (AgNPs) on a gold electrode (uricase/Chi-CNTsNF/AgNPs/Au). The uric acid response was determined at an optimum applied potential of -0.35 V vs Ag/AgCl in a flow-injection system based on the change of the reduction current for dissolved oxygen during oxidation of uric acid by the immobilized uricase. The response was directly proportional to the uric acid concentration. Under the optimum conditions, the fabricated uric acid biosensor had a very wide linear range, 1.0-400 µmol L(-1), with a very low limit of detection of 1.0 µmol L(-1) (s/n = 3). The operational stability of the uricase/Chi-CNTsNF/AgNPs/Au biosensor (up to 205 injections) was excellent and the storage life was more than six weeks. A low Michaelis-Menten constant of 0.21 mmol L(-1) indicated that the immobilized uricase had high affinity for uric acid. The presence of potential common interfering substances, for example ascorbic acid, glucose, and lactic acid, had negligible effects on the performance of the biosensor. When used for analysis of uric acid in serum samples, the results agreed well with those obtained by use of the standard enzymatic colorimetric method (P > 0.05).


Assuntos
Técnicas Biossensoriais/métodos , Quitosana/química , Enzimas Imobilizadas/análise , Nanopartículas Metálicas/química , Nanotubos de Carbono/química , Urato Oxidase/análise , Ácido Úrico/análise , Ácido Ascórbico/análise , Tampões (Química) , Catálise , Eletroquímica , Eletrodos , Glucose/análise , Concentração de Íons de Hidrogênio , Ácido Láctico/análise , Limite de Detecção , Nanofibras/química , Oxigênio/química , Prata/química , Ácido Úrico/química , Urina/química
11.
Biosens Bioelectron ; 38(1): 430-5, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22770826

RESUMO

This paper reports, for the first time, the influence of the length and the terminating head group of blocking thiols on the sensitivity and specificity of a label-free capacitive DNA detection system using immobilized pyrrolidinyl peptide nucleic acid (acpcPNA) probes. A C-terminal lysine-modified acpcPNA was immobilized through four different alkanethiol self-assembled monolayers (SAMs), i.e., 3-mercaptopropionic acid (MPA), thioctic acid (TA), thiourea (TU) and mercaptosuccinic acid (MSA). The hybridization between the acpcPNA probes and the target DNA was directly measured using the capacitive system. Five blocking thiols of various lengths (C=3, 6, 8, 9 and 11), with the -OH terminating head group, i.e., 3-mercapto-1-propanol (3-MPL), 6-mercapto-1-hexanol (6-MHL), 8-mercapto-1-octanol (8-MOL), 9-mercapto-1-nonanol (9-MNL), 11-mercapto-1-undecanol (11-MUL) and another blocking thiol (C=11) with a -CH(3) terminating head group, and 1-dodecanethiol (1-DDT) were investigated. The blocking thiol with the same length as the total spacer of the immobilized acpcPNA gave the highest sensitivity and specificity with the -OH terminating head group providing a slightly better signal than the -CH(3) group. Under the optimized conditions, the immobilized acpcPNA probes provided a wide linear range for DNA detection (1.0 × 10(-11)-1.0 × 10(-8)M) with a very low detection limit in the picomolar range. The modified acpcPNA electrode could be reused through at least 58 cycles. The high sensitivity and very low detection limits are potentially useful for the analysis of ultra-trace levels of DNA in samples. Preliminary studies were also performed to see the effect of probe concentration and target length.


Assuntos
Técnicas Biossensoriais/instrumentação , DNA/análise , Ácidos Nucleicos Peptídicos/química , Pirrolidinas/química , Sequência de Bases , Capacitância Elétrica , Limite de Detecção , Hibridização de Ácido Nucleico , Compostos de Sulfidrila/química , Transdutores
12.
Anal Chem ; 84(3): 1327-35, 2012 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-22185519

RESUMO

Ion-selective membranes operated in a thin layer coulometric detection mode have previously been demonstrated to exhibit attractive characteristics in view of realizing sensors without the need for frequent recalibration. In this methodology, the analyte ion is exhaustively removed across an ion-selective membrane by an applied potential, and the resulting current is integrated to yield the coulomb number and hence the amount of analyte originally present in the sample. This exhaustive process, however, places greater demands on the selectivity of the membrane compared to direct potentiometry, since the level of interference will increase as the analyte depletes. We evaluate here a double pulse protocol to reduce the level of interference, in which the sample is electrolyzed once again after the initial coulometric detection pulse. Since the analyte ion is no longer present at significant concentrations during the second pulse, but an interfering ion of high concentration did not appreciably deplete, the second electrolysis step may be used to partially compensate for undesired interference. These processes are here evaluated by numerical simulation for ions of the same charge, demonstrating that the resulting coulomb number may indeed be reduced for systems of limited selectivity. The improvement in operational selectivity relative to uncompensated coulometry is found to be ca. 6-fold. The methodology is successfully demonstrated experimentally with a calcium selective membrane and tetraethylammonium as a model interfering agent, and the observed relative errors after background compensation can be favorably compared to that in direct potentiometry where no sample depletion occurs.


Assuntos
Técnicas Eletroquímicas/instrumentação , Eletrodos Íon-Seletivos , Cálcio/química , Técnicas Eletroquímicas/métodos , Membranas Artificiais , Modelos Teóricos , Tetraetilamônio/química
13.
Biosens Bioelectron ; 26(11): 4571-8, 2011 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-21665460

RESUMO

A multilayer electrode modified with a self-assembled thiourea monolayer (SATUM) followed by gold nanoparticles (AuNPs), mercaptosuccinic acid (MSA) and antibody was investigated for the detection of ultra trace amount of a small molecule (chloramphenicol) in an impedimetric system. The formation of the antibody-antigen complex at the electrode surface caused the impedance to increase. Under optimum conditions three modified electrodes were compared the SATUM/AuNPs/MSA electrode provided a wide linear range (0.50-10) × 10⁻¹6 M, and a very low determination limit of 1.0 × 10⁻¹6 M. This determination limit was much lower than the SATUM/AuNPs electrode, 1.0 × 10⁻¹5 M, and SATUM electrode, 4.7 × 10⁻¹4 M. The modified electrode provided good selectivity for chloramphenicol detection and can be reused up to 45 times with a relative standard deviation of lower than 4%. When applied to determine chloramphenicol in shrimp samples, the results agreed well with those obtained by the high-performance liquid chromatography coupled with a photo diode array detector (P > 0.05). The developed system can be applied to detect other small molecules using appropriate affinity binding pairs.


Assuntos
Técnicas Biossensoriais/métodos , Animais , Anticorpos Imobilizados , Técnicas Biossensoriais/estatística & dados numéricos , Cloranfenicol/análise , Cloranfenicol/imunologia , Cromatografia Líquida de Alta Pressão , Impedância Elétrica , Técnicas Eletroquímicas , Eletrodos , Análise de Injeção de Fluxo , Contaminação de Alimentos/análise , Ouro , Limite de Detecção , Nanopartículas Metálicas , Reprodutibilidade dos Testes , Frutos do Mar/análise , Tiomalatos , Tioureia
14.
Anal Chim Acta ; 699(2): 232-41, 2011 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-21704779

RESUMO

Detection of ultra-trace amounts of antigens by label-free capacitive immunosensors was investigated using electrodes modified with silver nanoparticles (AgNPs) that allows for an increase in the amount of immobilized antibodies. The optimal amount of AgNPs that provided the highest immobilization yield was 48 pmol (in 2.0 mL). The performances of immunosensor electrodes for human serum albumin prepared with AgNPs, were compared to electrodes prepared with gold nanoparticles. The two systems provided the same linear range (1.0×10(-18) to 1.0×10(-10) M) and detection limit (1.0×10(-18) M). The system with AgNPs was used to analyze albumin in urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). Electrodes modified with AgNPs and appropriate antibodies were tested for their performances to detect analytes of different sizes. For a macromolecule (human serum albumin) the incorporation of AgNPs improved the detection limit from 100 to 1 aM. For small molecules, microcystin-LR and penicillin G, the detection limits were lowered from 100 and 10 fM to 10 and 0.7 fM, respectively. The high sensitivity and very low detection limits are potentially useful for the analysis of toxins or residues present in samples at ultra-trace levels and this method could easily be applied to other affinity pairs.


Assuntos
Anticorpos Imobilizados/imunologia , Antígenos/análise , Técnicas Biossensoriais/métodos , Imunoensaio/métodos , Nanopartículas Metálicas/química , Prata/química , Técnicas Eletroquímicas/métodos , Eletrodos , Ouro/química , Humanos , Nanopartículas Metálicas/ultraestrutura , Microcistinas/análise , Penicilina G/análise , Albumina Sérica/análise
15.
Biosens Bioelectron ; 26(2): 357-64, 2010 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-20801635

RESUMO

Boronic acid that can reversibly bind to diols was used to detect bacteria through its affinity binding reaction with diol-groups on bacterial cell walls. 3-aminophenylboronic acid (3-APBA) was immobilized on a gold electrode via a self-assembled monolayer. The change in capacitance of the sensing surface caused by the binding between 3-APBA and bacteria in a flow system was detected by a potentiostatic step method. Under optimal conditions the linear range of 1.5×10(2)-1.5×10(6) CFU ml(-1) and the detection limit of 1.0×10(2) CFU ml(-1) was obtained. The sensing surface can be regenerated and reused up to 58 times. The method was used for the analysis of bacteria in several types of water, i.e., bottled, well, tap, reservoir and wastewater. Compared with the standard plate count method, the results were within one standard deviation of each other. The proposed method can save both time and cost of analysis. The electrode modified with 3-APBA would also be applicable to the detection of other cis-diol-containing analytes. The concept could be extended to other chemoselective ligands, offering less expensive and more robust affinity sensors for a wide range of compounds.


Assuntos
Carga Bacteriana/instrumentação , Técnicas Biossensoriais/instrumentação , Ácidos Borônicos/química , Condutometria/instrumentação , Salmonella/isolamento & purificação , Staphylococcus aureus/química , Staphylococcus aureus/isolamento & purificação , Capacitância Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento , Microbiologia da Água
16.
Biosens Bioelectron ; 24(8): 2559-65, 2009 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-19201186

RESUMO

A flow injection capacitive biosensor system to detect trace amounts DNA has been developed based on the affinity binding between immobilized histone and DNA. Histones from calf thymus and shrimp were immobilized on gold electrodes covered with self-assembled monolayer (SAM) of thioctic acid. Each of these histones was used to detect DNA from calf thymus, shrimp and Escherichia coli. The studies indicated that histones can bind better with DNA from the same source and give higher sensitivity than the binding with DNA from different sources. Under optimum conditions, both histones from calf thymus and shrimp provided the same lower detection limit of 10(-5) ng l(-1) for DNA from different sources, i.e., calf thymus, shrimp and E. coli. The standard curve for the affinity reaction between calf thymus histone and DNA shows sigmoidal behavior and two linear ranges, 10(-5) to 10(-2) ng l(-1) and 10(-1) to 10(2) ng l(-1), could be obtained. The immobilized histones were stable and after regeneration good reproducibility of the signal could be obtained up to 43 times with a %R.S.D. of 3.1. When applied to analyze residual DNA in crude protein extracted from white shrimp recoveries were obtained between 80% and 116%.


Assuntos
Técnicas Biossensoriais/instrumentação , DNA/análise , DNA/genética , Eletroquímica/instrumentação , Análise de Injeção de Fluxo/instrumentação , Microquímica/instrumentação , DNA/química , Capacitância Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
17.
Anal Chem ; 80(3): 707-12, 2008 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-18184015

RESUMO

We here report on the first example of an aptamer-based potentiometric sandwich assay of proteins. The measurements are based on CdS quantum dot labels of the secondary aptamer, which were determined with a novel solid-contact Cd2+-selective polymer membrane electrode after dissolution with hydrogen peroxide. The electrode exhibited cadmium ion detection limits of 100 pM in 100 mL samples and of 1 nM in 200 microL microwells, using a calcium-selective electrode as a pseudoreference electrode. As a prototype example, thrombin was measured in 200 microL samples with a lower detection limit of 0.14 nM corresponding to 28 fmol of analyte. The results show great promise for the potentiometric determination of proteins at very low concentrations in microliter samples.


Assuntos
Aptâmeros de Peptídeos/química , Técnicas Biossensoriais/métodos , Eletrodos Íon-Seletivos , Potenciometria/métodos , Proteínas/análise , Técnicas Biossensoriais/instrumentação , Compostos de Cádmio/química , Imunoensaio , Potenciometria/instrumentação , Proteínas/química , Pontos Quânticos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Coloração e Rotulagem , Sulfetos/química , Trombina/análise , Trombina/química
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