RESUMO

In this paper, a highly sensitive method for sulfur ion (S2-) detection was developed based on a four-color fluorescence probe constructed from copper-containing metal-organic framework (CuBDC) and four dye-labeled single-strand DNA (ssDNA). In the absence of S2-, dye-labeled ssDNA can be adsorbed on the surface of CuBDC, and the dyes are close to copper ion on the CuBDC surface, their fluorescence is quenched by copper ion, and their fluorescence signals are weak. In the presence of S2- in the system, S2- reacts with copper ion in CuBDC to form CuS, which has a more stable structure than complex CuBDC, resulting in the decomposition of CuBDC. In this case, dye-labeled ssDNA are detached from the CuBDC surface and dissolved in the solution, and the fluorescence of the dyes is restored. Under the optimized conditions, there is a good linear relationship between the total fluorescence intensity of four dyes and the concentration of S2- in the range of 2 × 10-9 to 5 × 10-8 mol/L; the detection limit is 2.2 × 10-10 mol/L. The method has a good selectivity and accuracy, and it can be applied to the analysis and detection of S2- in actual water samples.

Assuntos

Cobre , Corantes Fluorescentes , Estruturas Metalorgânicas , Espectrometria de Fluorescência , Enxofre , Cobre/química , Cobre/análise , Enxofre/química , Estruturas Metalorgânicas/química , Corantes Fluorescentes/química , Poluentes Químicos da Água/análise , Fluorescência , DNA de Cadeia Simples/química , Limite de Detecção , Água/química , Íons/análise , Íons/química , Cor , Estrutura Molecular

RESUMO

We have developed a new method of one-step simultaneous detection for three pesticides including acetamiprid, atrazine and carbendazim based on organic framework nanomaterial Cu/UiO-66 and three different fluorescent dyes labeled pesticide aptamers. Cu/UiO-66 can be easily combined with pesticide aptamers through strong coordination, and then aptamers were adsorbed to the surface of Cu/UiO-66, which brings the dyes and Cu/UiO-66 into close proximity. Then, the fluorescence of dyes was quenched by Cu/UiO-66. When the target pesticides appeared, the aptamers reacted with corresponding target pesticides and formed special spatial structure, and then the dyes were far away from the surface of Cu/UiO-66 and the fluorescence of dyes is resumed. Thus, the one-step simultaneous detection for three pesticides can be achieved by synchronous fluorescence analysis. The detection limit of acetamiprid, atrazine and carbendazim were 0.1 nmol/L, 1.6 nmol/L, and 0.3 nmol/L, respectively. This method has a good sensitivity, low detection limit, and high selectivity. We have developed a new method of one-step simultaneous detection for three pesticides including acetamiprid, atrazine and carbendazim based on a multi-color fluorescent probe composed of bimetallic organic framework nanomaterials Cu/UiO-66 and three different fluorescent dyes and phosphate double-labeled aptamers of acetamiprid, atrazine and carbendazim.

Assuntos

Nanoestruturas , Praguicidas , Corantes Fluorescentes , Estruturas Metalorgânicas , Oligonucleotídeos , Ácidos Ftálicos

RESUMO

We have developed a fluorescence quantitative analysis method for the simultaneous detection of Hg2+, Pb2+ and Ag+ based on fluorescently labelled nucleic acid aptamer probes and graphene oxide (GO). By this method, three nucleic acid aptamer probes (PHg, PPb, PAg) were designed. The carboxyl fluorescein (FAM), tetramethyl-6-carboxyrhodamine (TAMRA) and cyanine-5 (Cy-5) were respectively selected as fluorophore of aptamer probes, and GO was chosen as quencher. In general, these probes were on free single-stranded state and adsorbed on the surface of GO via π-π interactions, which brought fluorophores of probes and GO into close proximity. Due to the fluorescence resonance energy transfer occurred between fluorophores and GO, the fluorescence was quenched and fluorescence signals were all weak. Under the optimal condition, fluorescence intensities of three fluorophores exhibited a good linear dependence on corresponding ions concentration. The detection limit for Hg2+, Pb2+ and Ag+ were 0.2, 0.5 and 2 nmol/L (3σ, n = 11). Average recoveries of this method were 97.56-104.92%, which indicated the method had a high accuracy and low detection limit. In addition, this proposed method has good selectivity, and there was no crosstalk effect among these probes.

Assuntos

Técnicas Biossensoriais , Grafite , Mercúrio , Chumbo , Limite de Detecção , Prata

RESUMO

A fluorescence method for the quantitative detection of chloramphenicol (CAP) has been developed using phosphate and fluorescent dye 6-carboxy-x-rhodamine (ROX) double-labeled aptamers of CAP and the bimetallic organic framework nanomaterial Cu/UiO-66. Cu/UiO-66 was prepared by coordinate bonding of metal organic framework (MOF) nanomaterial UiO-66 with copper ions. Cu/UiO-66 contains a large number of metal defect sites, which can be combined with phosphate-modified nucleic acid aptamers through strong coordination between phosphate and zirconium to form "fluorescence turn-on" sensors. In the absence of CAP, all single-stranded aptamers were adsorbed on the surface of Cu/UiO-66 through π-π stacking between single-stranded DNA and Cu/UiO-66, which brings the ROX fluorophores and Cu/UiO-66 into close proximity. The ROX fluorescence of aptamers was then quenched by Cu/UiO-66 through photoinduced electron transfer (PET). In the presence of CAP, however, CAP reacted with nucleic acid aptamers to form a special spatial structure, in which the ROX fluorophores were far away from the MOF surface via a change in the spatial structure of the aptamers, and the fluorescence of ROX was able to be recovered. The quantitative detection of CAP can be achieved by measuring the fluorescence signal of ROX using synchronous scanning fluorescence spectrometry. Under optimum conditions, the fluorescence intensities of ROX exhibit a good linear dependence on the concentration of CAP in the range of 0.2-10 nmol/L, with a detection limit of 0.09 nmol/L. The method has advantages of high sensitivity, good selectivity, and a low limit of detection. Graphical abstract.

RESUMO

In this work, a novel MOF(Fe)@NaAlg aerogels composite were fabricated by a facile method of ion cross-linking, and characterized via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS) and BET surface area analysis. The MOF(Fe)@NaAlg aerogels loaded by ammonium (NH4+) was prepare to the slow-release fertilizer (SRF). The adsorption capacity and swelling of MOF(Fe)@NaAlg(2:10) were 29.4 mg/g and 73 g/g, respectively. The swelling behaviors of MOF(Fe)@NaAlg(2:10) in different saline solutions were investigated. The release assessments confirmed the effective role of MOF(Fe) in slow-release property of the prepared formulation. Also, the prepared fertilizer formulation exhibited excellent water-retention capacity in soil. Therefore, they will have a great potential application in the field of agriculture.

Assuntos

Alginatos/química , Fertilizantes , Hidrogéis/química , Adsorção , Cinética , Estruturas Metalorgânicas , Solo , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química , Difração de Raios X

RESUMO

We designed two double quenching molecular beacons (MBs) with simple structure based on guanine (G base) and Black Hole Quencher (BHQ), and developed a new analytical method for sensitive simultaneous detection of two DNAs by synchronous fluorescence analysis. In this analytical method, carboxyl fluorescein (FAM) and tetramethyl-6-carboxyrhodamine (TAMRA) were respectively selected as fluorophore of two MBs, Black Hole Quencher 1 (BHQ-1) and Black Hole Quencher 2 (BHQ-2) were respectively selected as organic quencher, and three continuous nucleotides with G base were connected to organic quencher (BHQ-1 and BHQ-2). In the presence of target DNAs, the two MBs hybridize with the corresponding target DNAs, the fluorophores are separated from organic quenchers and G bases, leading to recovery of fluorescence of FAM and TAMRA. Under a certain conditions, the fluorescence intensities of FAM and TAMRA all exhibited good linear dependence on their concentration of target DNAs (T1 and T2) in the range from 4 × 10-10 to 4 × 10-8molL-1 (M). The detection limit (3σ, n = 13) of T1 was 3 × 10-10M and that of T2 was 2×10-10M, respectively. Compared with the existing analysis methods for multiplex DNA with MBs, this proposed method based on double quenching MBs is not only low fluorescence background, short analytical time and low detection cost, but also easy synthesis and good stability of MB probes.

Assuntos

DNA Viral/análise , DNA Viral/química , Guanina , Sondas de Oligonucleotídeos/química , Sequência de Bases , Calibragem , DNA Viral/genética , Estudos de Viabilidade , HIV/genética , Vírus da Hepatite B/genética , Limite de Detecção , Hibridização de Ácido Nucleico , Sondas de Oligonucleotídeos/genética , Polimorfismo de Nucleotídeo Único

RESUMO

A highly sensitive and selective fluorescence method of quantitative detection for mercury in soil was developed using non-labeled molecular beacon (MB), single-stranded nucleic acid (ssDNA) and fluorescent dye Hoechst 33258. In this analytical method, the loop of MB was designed to be a sequence that was complementary to the ssDNA with multiple T-T mismatches, the stem of MB was completely designed as C-G base pairs, and both ends of the MB are not modified by any fluorophore and quencher. In the absence of Hg2+, the interaction between Hoechst 33258 and the MB was very weak, and the fluorescence signal of Hoechst 33258 was very low. In the presence of Hg2+, the MB and ssDNA with multiple T-T mismatches formed a double-stranded nucleic acid (dsDNA) via the T-Hg2+-T coordination structure which provided binding sites for Hoechst 33258. Then Hoechst 33258 binded to A-T base pairs of dsDNA, and the fluorescence intensity of Hoechst 33258 was significantly enhanced. Thus, a highly sensitive fluorescence quantitative detection method for Hg2+ can be realized. In this strategy, the optimal determination conditions for Hg2+ were a buffer solution pH of 8.2, an incubated temperature of 50°C, an incubated time of 5 min and NaCl of 60 mmol L-1. Under the optimum conditions, the fluorescence intensity of Hoechst 33258 exhibited a good linear dependence on the concentration of Hg2+ in the range of 5 × 10-9 - 400 × 10-9 mol L-1. The fitted regression equation was ΔI = 2.1084C - 8.9587 with a correlation coefficient of 0.9943 (R2), and the detection limit of this method was 3 × 10-9 mol L-1 (3σ). The proposed method had a high selection; the common substances in soil such as Ca2+, Mg2+, Mn2+, Fe3+, Cu2+, Pb2+, Al3+, K+, Na+, Ni2+, Cd2+, Cr3+, SiO32-, Cl-, PO43-, NH4+ and S2- had no interference to the detection of mercury. The proposed method had a high accuracy, and it was applied to detect mercury of ten different types of soil; the recoveries were 97.65 - 103.22%. In addition, the proposed method had a low background emission, fast detection speed and low detection cost.

Assuntos

Bisbenzimidazol/química , Carbono/química , Fluorescência , Corantes Fluorescentes/química , Mercúrio/análise , Pontos Quânticos , Solo/química , Espectrometria de Fluorescência

RESUMO

A highly sensitive fluorescence method of quantitative detection for specific DNA sequence is developed based on molecular beacon (MB) and nucleic acid dye SYBR Green I by synchronous fluorescence analysis. It is demonstrated by an oligonucleotide sequence of wild-type HBV (target DNA) as a model system. In this strategy, the fluorophore of MB is designed to be 6-carboxyfluorescein group (FAM), and the maximum excitation wavelength and maximum emission wavelength are both very close to that of SYBR Green I. In the presence of targets DNA, the MBs hybridize with the targets DNA and form double-strand DNA (dsDNA), the fluorophore FAM is separated from the quencher BHQ-1, thus the fluorophore emit fluorescence. At the same time, SYBR Green I binds to dsDNA, the fluorescence intensity of SYBR Green I is significantly enhanced. When targets DNA are detected by synchronous fluorescence analysis, the fluorescence peaks of FAM and SYBR Green I overlap completely, so the fluorescence signal of system will be significantly enhanced. Thus, highly sensitive fluorescence quantitative detection for DNA can be realized. Under the optimum conditions, the total fluorescence intensity of FAM and SYBR Green I exhibits good linear dependence on concentration of targets DNA in the range from 2×10(-11) to 2.5×10(-9)M. The detection limit of target DNA is estimated to be 9×10(-12)M (3σ). Compared with previously reported methods of detection DNA with MB, the proposed method can significantly enhance the detection sensitivity.

Assuntos

Alcanossulfonatos/química , Compostos Azo/química , Técnicas Biossensoriais/métodos , DNA/química , Compostos Orgânicos/química , Espectrometria de Fluorescência/métodos , Benzotiazóis , DNA/genética , Primers do DNA/química , Diaminas , Fluoresceínas/química , Corantes Fluorescentes/química , Luz , Limite de Detecção , Ácidos Nucleicos/genética , Sondas de Oligonucleotídeos/genética , Oligonucleotídeos/química , Quinolinas , Reprodutibilidade dos Testes , Espalhamento de Radiação

RESUMO

We have developed a new fluorescence method for specific single-stranded DNA sequences with exonuclease III (Exo III) and nucleic acid dye SYBR Green I. It is demonstrated by a reverse transcription oligonucleotide sequence (target DNA, 27 bases) of RNA fragment of human immunodeficiency virus (HIV) as a model system. In the absence of the target DNA, the hairpin-probe is in the stem-closed structure, the fluorescence of SYBR Green I is very strong. In the presence of the target DNA, the hairpin-probe hybridizes with the target DNA to form double-stranded structure with a blunt 3'-terminus. Thus, in the presence of Exo III, only the 3'-terminus of probe is subjected to digestion. Exo III catalyzes the stepwise removal of mononucleotides from this terminus, releasing the target DNA. The released target DNA then hybridizes with another probe, whence the cycle starts anew. The signal of SYBR Green I decreases greatly. This system provides a detection limit of 160 pM, which is comparable to the existing signal amplification methods that utilized Exo III as a signal amplification nuclease. Due to the unique property of Exo III, this method shows excellent detection selectivity for single-base discrimination. More importantly, superiors to other methods based on Exo III, these probes have the advantages of easier to design, synthesize, purify and thus are much cheaper and more applicable. This new approach could be widely applied to sensitive and selective nucleic acids detection.

Assuntos

Técnicas Biossensoriais , DNA/análise , Exodesoxirribonucleases/química , Corantes Fluorescentes/química , HIV/genética , Compostos Orgânicos/química , Benzotiazóis , DNA/química , DNA/genética , Sondas de DNA , Diaminas , Polimorfismo de Nucleotídeo Único , Quinolinas , RNA Viral/genética

RESUMO

We developed a multiplexed DNA detection method with a composite molecular beacon (MB) probe based on guanine-quenching by synchronous fluorescence analysis. It is demonstrated by two types of tumor-suppressor genes namely exon segments of p16 (T1) and p53 (T2) genes. The composite MB probe includes two loops and two stems, and two fluorophores of 6-carboxyfluorescein group (FAM) and tetramethyl-6-carboxyrhodamine (TAMRA) are connected to the two ends of molecular beacon. Every stem portion of MB include four continuous nucleotides with guanine (G) base as quencher, every loop portion is a probe sequence that is complementary to a corresponding target sequence. In the absence of target DNA, the composite MBs are in the stem-closed form, the fluorescence of FAM and TAMRA are quenched by G bases. At this time, the fluorescence signals of FAM and TAMRA are all very low. In the presence of target DNA, the MBs hybridize with the target DNA and form double-strands, FAM and TAMRA are separated from G bases, and the fluorescence of FAM and TAMRA recovers simultaneously. Thus, the simultaneous detection of two targets of DNA can be realized by measuring fluorescence signals of FAM and TAMRA, respectively. Under the optimum conditions, the fluorescence intensities of FAM and TAMRA all exhibit good linear dependence on their target DNA concentration in the range from 5 × 10(-11) to 5.5 × 10(-9) M. The detection limit of T1 is 4 × 10(-11) M (3σ), and that of T2 is 3 × 10(-11) M. This composite MB can be applied to detect the real sample, and can be applied to detect two aleatoric sequences of DNA. Compared with previously reported methods of detecting multiplexed target DNA with MBs, the proposed method has some advantages including easy synthesis of composite MB probes, low detection cost and shorter analytical time.

Assuntos

Técnicas Biossensoriais/métodos , DNA/análise , DNA/química , Guanina/química , Sondas de Oligonucleotídeos/química , Sequência de Bases , Soluções Tampão , DNA/genética , Estudos de Viabilidade , Concentração de Íons de Hidrogênio , Limite de Detecção , Sondas de Oligonucleotídeos/genética , Concentração Osmolar , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único , Espectrometria de Fluorescência , Fatores de Tempo

RESUMO

The bifunctionality of graphene oxide (GO) which can highly adsorb single-stranded DNA (ssDNA) and effectively quench the emission of organic dyes is reasonably utilized in a multiplexed DNA detection system, achieving sensitive and selective detection of HIV, VV and EV, respectively.

Assuntos

Técnicas de Química Analítica/instrumentação , DNA/análise , DNA/genética , Grafite/química , Óxidos/química , Adsorção , Cor , DNA/química , Modelos Moleculares , Conformação de Ácido Nucleico

RESUMO

We have developed a tricolor fluorescence quantitative method for sequence-specific DNA detection using a new molecular beacon (MB) and a nucleic acid dye TOTO-3. This new MB is designed with two fluorophores of FAM and TAMRA instead of one fluorophore and one quencher of traditional MB, and a nucleotide with guanine base is attached directly to FAM as a quencher. In the absence of target DNA, MBs are in the stem-loop state. The fluorescence of FAM is absorbed by TAMRA, and the fluorescence of TAMRA is quenched by guanine base. Meanwhile, the interaction between TOTO-3 and MBs is very weak. In the presence of target DNA, MBs hybridize with target DNA to form a double-stranded structure. TAMRA is separated from FAM and guanine base, and the fluorescence of FAM and TAMRA recovers simultaneously. At the same time TOTO-3 binds to double-stranded DNA, the fluorescence of TOTO-3 significantly enhances. In this strategy, the false-positive signals of MBs caused by non-specific interactions can be distinguished by the change of the ratio of the total fluorescence intensities of FAM and TAMRA to that of TOTO-3 at different concentrations of target DNA. In the simple sample, the detection of target DNA can be achieved with the total fluorescence intensity of three dyes, which results in a significant improvement of the detection sensitivity. In the complex sample, the detection of target DNA can be achieved with the fluorescence intensity of TOTO-3 which can overcome the false-positive signals of MBs and improve the detection accuracy.

Assuntos

DNA/análise , DNA/genética , Corantes Fluorescentes/química , Sondas de Oligonucleotídeos/química , Quinolinas/química , Espectrometria de Fluorescência/métodos , Tiazóis/química , Sequência de Bases , Soluções Tampão , Cor , DNA/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Hibridização de Ácido Nucleico , Sondas de Oligonucleotídeos/genética , Concentração Osmolar , Polimorfismo de Nucleotídeo Único , Temperatura

RESUMO

We have developed a dual color fluorescence quantitative detection method for specific single-stranded DNA with molecular beacons (MBs) and nucleic acid dye SYBR Green I by synchronous scanning fluorescence spectrometry. It is demonstrated by a reverse-transcription oligonucleotide sequence (target DNA, 33 bases) of RNA fragment of human immunodeficiency virus (HIV) as a model system. In the absence of target DNA, the MBs are in the stem-closed state, the fluorescence of 5-carboxy-X-rhodamine (ROX) is quenched by black hole quencher-2 (BHQ-2), and the interaction between SYBR Green I and the MBs is very weak. At this time the fluorescence signals of ROX and SYBR Green I are all very weak. In the presence of target DNA, MBs hybridize with target DNA and form a double-strand structure, the fluorophore ROX is separated from the quencher BHQ-2, and the fluorescence of ROX recovers. At the same time, SYBR Green I binds to hybridized dsDNA, whose fluorescence intensity is significantly enhanced. Thus, dual color fluorescence quantitative detection for the target DNA can be realized by synchronous scanning fluorescence spectrometry. In this strategy, the fluorescence signal of SYBR Green I is far larger than that of ROX, so the quantitative analysis of target DNA with the fluorescence intensity of SYBR Green I can significantly improve the detection sensitivity. In addition, the false-positive signals of MBs do not affect the fluorescence signals of nucleic acid dye SYBR Green I. Thereby, in the analysis of complex samples, quantitative analysis of target DNA with SYBR Green I can avoid the false-positive signals of MBs and improve the detection accuracy.

Assuntos

DNA de Cadeia Simples/análise , DNA de Cadeia Simples/química , Corantes Fluorescentes/química , Sondas de Oligonucleotídeos/química , Compostos Orgânicos/química , Espectrometria de Fluorescência/métodos , Sequência de Bases , Benzotiazóis , Soluções Tampão , Cor , DNA de Cadeia Simples/genética , Diaminas , Estudos de Viabilidade , Concentração de Íons de Hidrogênio , Limite de Detecção , Modelos Moleculares , Conformação de Ácido Nucleico , Sondas de Oligonucleotídeos/genética , Concentração Osmolar , Polimorfismo de Nucleotídeo Único , Quinolinas , Temperatura , Fatores de Tempo

RESUMO

An amplified multiplexed DNA detection biosensor has been developed, which combines the unique cleavage function of exonuclease III (Exo III) with the separating ability of magnetic microparticles (MMPs). By using different fluorophores, the multiplexed detection of DNA is demonstrated.

Assuntos

Técnicas Biossensoriais , DNA Viral/análise , Ebolavirus/genética , HIV/genética , Sequência de Bases , Exodesoxirribonucleases/química , Corantes Fluorescentes/química

RESUMO

We have developed a new fluorescent immune ensemble probe comprised of a conjugated lower toxic water-soluble CdTe:Zn(2+) quantum dots (QDs) and Ru(bpy)(2)(mcbpy-O-Su-ester)(PF(6))(2)- antibody complex (Ru-Ab) for the dual-color determination of human enterovirus 71 (EV71) in homogeneous solution. EV71 monoantibody was easily covalently conjugated with Ru(bpy)(2)(mcbpy-O-Su-ester)(PF(6))(2) to form a stable complex Ru-Ab, which acted both as an effective quencher of QDs fluorescence and the capture probe of virus antigen EV71. Herein, the target EV71 can break up the low fluorescent ionic ensemble by antigen-antibody combination to set free the fluorescent QDs and restore the fluorescence of QDs whereas the fluorescence intensity of Ru-Ab remains the same. Thus, the determination of EV71 by the complex Ru-Ab and QDs can be realized via the restoration of QDs fluorescence upon addition of EV71 and even can be directly evaluated by the ratio of green-colored QDs fluorescence intensity to Ru-Ab red-colored fluorescence intensity. The green-colored fluorescence of QDs was very sensitive to the change of EV71 concentration, and its fluorescence intensity increased with the increase of EV71 concentration between 1.8 ng/mL and 12 µg/mL. With this method, EV71 was detected at subnanogram per milliliter concentration in the presence of 160 µg/mL bovine serum albumin. More importantly, this strategy can be used as a universal method for any protein or virus by changing conjugated antibodies in disease early diagnosis providing a fast and promising clinical approach for virus determination. In a word, a simple, fast, sensitive, and highly selective assay for EV71 has been described. It could be applied in real sample analysis with a satisfactory result. It was notable that the sensor could not only achieve rapid and precise quantitative determination of protein/virus by fluorescent intensity but also could be applied in semiquantitative protein/virus determination by digital visualization.

Assuntos

Enterovirus Humano A/imunologia , Enterovirus Humano A/isolamento & purificação , Fluorescência , Imunoensaio/métodos , Animais , Anticorpos/química , Anticorpos/imunologia , Complexo Antígeno-Anticorpo/química , Complexo Antígeno-Anticorpo/imunologia , Técnicas Biossensoriais , Bovinos , Células Cultivadas , Chlorocebus aethiops , Colorimetria , Humanos , Concentração de Íons de Hidrogênio , Compostos Organometálicos/química , Pontos Quânticos , Soroalbumina Bovina/química , Espectrometria de Fluorescência , Células Vero

RESUMO

We have developed a new analytical method to detect multiple DNA simultaneously based on the biobarcoded CdSe/ZnS quantum dot (QD) and magnetic microparticle (MMP). It was demonstrated by using oligonucleotide sequences of 64 bases associated with human papillomavirus 16 and 18 L1 genes (HPV-16 and HPV-18) as model systems. This analytical system involves three types of probes, a MMP probe and two streptavidin-modified QD probes. The MMPs are functionalized with HPV-16 and HPV-18 captures DNA to form MMP probes. The QDs are conjugated with HPV-16 or HPV-18 probe DNA along with FAM- or Rox-labeled random DNA to form HPV-16 and HPV-18 QD probes, respectively. A one-step hybridization reaction was performed by mixing the MMP probes, HPV-16 and HPV-18 target DNA (T-16 and T-18), HPV-16 and HPV-18 QD probes. Afterwards, the hybrid-conjugated microparticles were separated by a magnet and heated to remove the MMPs. Finally, the detections of T-16 and T-18 were done by measuring fluorescence signals of FAM and Rox, respectively. Under the optimum conditions, the fluorescence intensity exhibited a good linear dependence on target DNA concentration in the range from 8 × 10⁻¹¹ to 8 × 10⁻9 M. The detection limit of T-16 is up to 7 × 10⁻¹¹ M (3σ), and that of T-18 is 6 × 10⁻¹¹ M. Compared with other biobarcode assay methods, the proposed method that QDs were used as the solid support has some advantages including shorter preparation time of QD probes, faster binding kinetics and shorter analytical time. Besides, it is simple and accurate.

Assuntos

DNA/análise , DNA/genética , Pontos Quânticos , Sequência de Bases , Código de Barras de DNA Taxonômico , Sondas de DNA de HPV/genética , Papillomavirus Humano 16/genética , Papillomavirus Humano 18/genética , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Magnetismo , Hibridização de Ácido Nucleico , Concentração Osmolar , Polimorfismo de Nucleotídeo Único , Estreptavidina

RESUMO

We have developed a new analytical method to detect melamine (MA) in milk powder based on the fluorescence enhancement of Au nanoparticles (AuNPs). AuNPs with the average diameter of ∼16 nm can emit stable fluorescence at 370 nm when the excitation wavelength was selected at 252 nm. The AuNPs could assemble with melamine to form larger aggregates (AuNPs-MA) through electrostatic interaction and coordinating interaction in acidic conditions, which led to the significant enhancement of the fluorescence intensity. Under the optimized conditions, the enhancement of the fluorescence intensity exhibited a good linear dependence on melamine concentration in the range from 8.0 × 10(-10) to 8.0 × 10(-8) M, and the detection limit is 6.1 × 10(-10) M (3σ). This proposed method showed high precision and accuracy when applied to the real sample analyses. In conclusion, a simple, rapid, accurate and sensitive method to detect melamine has been suggested.