Co-reporter:Rong Hu, Zai-Sheng Wu, Songbai Zhang, Guo-Li Shen and Ruqin Yu
Chemical Communications 2011 vol. 47(Issue 4) pp:1294-1296
Publication Date(Web):22 Nov 2010
DOI:10.1039/C0CC03884A
A highly sensitive and selective electrochemical DNA signaling scheme, which identifies the point mutation existing in target DNA sequence, is developed based on the combination of label-free hairpin probe (HP)/DNA endonuclease with zirconia (ZrO2) nanoparticle film, representing a promising screening platform for the accurate diagnosis of infections and genetic diseases as well as for environmental and forensic applications.
Co-reporter:Yuehua Fei, Xiao-Yong Jin, Zai-Sheng Wu, Song-Bai Zhang, Guoli Shen, Ru-Qin Yu
Analytica Chimica Acta 2011 Volume 691(1–2) pp:95-102
Publication Date(Web):8 April 2011
DOI:10.1016/j.aca.2011.02.040
In order to develop a highly sensitive and selective piezoelectric transducer for the detection of DNA, the bio-recognizing probe is for the first time designed by introducing a hairpin structure and a recognition site for EcoRI into an oligonucleotide sequence and signal amplifiers are prepared by modifying gold nanoparticles (GNPs) with biomolecules, deepening the application and understanding of biomaterials. The piezoelectric transducer is prepared by immobilizing designed hairpin recognition probe onto the quartz-crystal-microbalance (QCM). In the absence of target DNA, the hairpin probe is removed from the QCM surface after exposure to endonuclease, inhibiting the subsequent signaling reaction. In contrast, introduction of target DNA can open the hairpin probe due to the probe/target hybridization, dissociating the cleavable double-stranded portion. In this case, even if being treated with endonuclease, the integrated hairpin probe is maintained. Subsequent introduction of GNPs modified with detection probes that can hybridize to the terminal sequence of hairpin probe results in a many-folds increase of the frequency response. Utilizing the proposed transduction scheme, the reliable target DNA detection can be accomplished. The detection limit of 2 pM and dynamic response range for target DNA from 2 to 300 pM are obtained. Furthermore, single-base mismatched DNAs can be easily identified. The developed proof-of-principle of a novel piezoelectric transduction scheme is expected to establish a potential platform for the disease-associated mutation analysis and DNA hybridization detection in biotechnology and medical diagnostics.
Co-reporter:Yue-Hua Fei, Dengyou Liu, Zai-Sheng Wu, Guo-Li Shen, and Ru-Qin Yu
Bioconjugate Chemistry 2011 Volume 22(Issue 12) pp:2369
Publication Date(Web):October 13, 2011
DOI:10.1021/bc200086c
Identification and quantification of small organic molecules capable of binding to a protein of interest with reasonable affinity and specificity is a central problem. Via developing DNA-encoded recognizing probe, we validate a proof-of-principle for constructing of small target-to-DNA conversion that screens the small molecule–protein interaction. Successful identification of β-indole acetic acid, abscisic acid, or 2,4-dichlorophenoxyacetic acid/corresponding antibody binding implies its fascinating potential for interrogating small molecule/protein interaction.
Co-reporter:Yun Zhang, Hua Wang, Jianping Li, Jinfang Nie, Yuwei Zhang, Guoli Shen, Ruqin Yu
Biosensors and Bioelectronics 2011 Volume 26(Issue 7) pp:3272-3277
Publication Date(Web):15 March 2011
DOI:10.1016/j.bios.2010.12.040
In this paper, an aqueous solution diffusion-localized platform (ASDLP) for multianalyte immunogold staining assays has been developed for the first time by assembling nitrocellulose (NC) strips onto a superhydrophobic polycarbonate (PC) coating with a water contact angle (CA) up to 160°. In the concept-of-proof experiments, the ASDLP was used for colorimetric detection of a human IgG model antigen based on the gold-enhanced gold nanoparticle (AuNP) label amplification. The relative concentration of the analyte captured on NC was further quantified by measuring the intensity of staining result with the use of image analysis software. The comparison study demonstrates that the white superhydrophobic PC-based ASDLP can offer preferable advantages over the commonly adopted bulky piece of NC for immunogold staining assays, in terms of the localized antibody immobilization and reagent addition, the minimization of “coffee effect”, uniformity of staining results, quantitative analysis and use efficiency of NC. Moreover, the high selectivity of a multiple antibodies-immobilized NC strip array for multiple antigens in a single sample has been further demonstrated in the multianalyte immunogold staining assay experiments.
Co-reporter:Jian Tang, Rong Hu, Zai-Sheng Wu, Guo-Li Shen, Ru-Qin Yu
Talanta 2011 Volume 85(Issue 1) pp:117-122
Publication Date(Web):15 July 2011
DOI:10.1016/j.talanta.2011.03.038
Co-reporter:Kejun Feng, Li-Ping Qiu, Yifeng Yang, Zai-Sheng Wu, Guo-Li Shen, Ru-Qin Yu
Biosensors and Bioelectronics 2011 Volume 29(Issue 1) pp:66-75
Publication Date(Web):15 November 2011
DOI:10.1016/j.bios.2011.07.068
Oligonucleotide-based detection schemes that avoid chemical modification possess significant advantages, including simplified design, intrinsic affinity for targets, low cost and ease to extend applications. In this contribution, we developed a label-free self-locked bifunctional oligonucleotide probe (signaling probe) for the detection of different disease markers in parallel. Two signal enhancement techniques based on isothermal circular strand-displacement polymerization reaction, cyclical nucleic acid strand-displacement polymerization (CNDP) and cyclical common (nonnucleic acid) target-displacement polymerization (CCDP), were employed to implement the amplification assay for p53 gene and PDGF-BB, respectively. The attractive assay properties confirmed the effectiveness of isothermal polymerization in common biosensing systems without evolving any chemical modification: PDGF could be detected down to 0.87 ng/mL, and a dynamic response range of 8–5000 ng/mL was achieved; The capability to screen the p53 gene was also considerably improved, including the detection limit, sensitivity, dynamic range and so on. Moreover, because no any chemical modification of the signaling probe was acquired and different targets were separately detected in homogeneous solution. This interrogating platform exhibits the design flexibility, convenience, simplicity and cost-effectiveness. The success achieved here is expected to serve as a significant step toward the development of robust label-free oligonucleotide probes in biomarker profiling and disease diagnostics.
Co-reporter:Songbai Zhang, Zai-Sheng Wu, Liping Qiu, Hui Zhou, Guoli Shen and Ruqin Yu
Chemical Communications 2010 vol. 46(Issue 19) pp:3381-3383
Publication Date(Web):17 Mar 2010
DOI:10.1039/B926646A
Ferrocene-conjugated oligonucleotides that can form intermolecular guanine (G)-quadruplexes are prepared and used as signaling probes for detecting target DNA, improving substantially assay characteristics (e.g. a considerably wider linear dynamic range and lower detection limit).
Co-reporter:Zaisheng Wu, Hui Zhou, Songbai Zhang, Xiaobing Zhang, Guoli Shen and Ruqin Yu
Chemical Communications 2010 vol. 46(Issue 13) pp:2232-2234
Publication Date(Web):18 Jan 2010
DOI:10.1039/B919585H
A pendulum-type DNA nanoswitch, which can perform a reversible on/off molecular motion at an about 9.1-nm scale is developed as a proof-of-concept, and the sequence-specific recognition and quantification of target olignucleotides are demonstrated utilizing this screening scheme.
Co-reporter:Zai-Sheng Wu, Hui Zhou, Songbai Zhang, Guoli Shen and Ruqin Yu
Analytical Chemistry 2010 Volume 82(Issue 6) pp:2282
Publication Date(Web):February 15, 2010
DOI:10.1021/ac902400n
A reusable aptameric recognition system was described for the electrochemical detection of the protein PDGF-BB based on the target binding-induced rolling circle amplification (RCA). A complementary DNA (CDNA), linear padlock probe, and primer probe were utilized to introduce a RCA process into the aptamer−target binding event while a new aptamer was elegantly designed via lengthening the original aptamer by the complement to the CDNA. The aptameric sensing system facilitates the integration of multiple functional elements into a signaling scheme: a unique electrochemical technique, an attractive RCA process, reversible DNA hybridization, and desirable aptameric target recognition. This RCA-based electrochemical recognition system not only exhibits excellent performance (e.g., a detection limit of 6.3 × 10−11 M, a linear dynamic range of 2 orders of magnitude, high specificity, and satisfactory repeatability) but also overcomes the limitations associated with conventional aptameric biosensors (e.g., dependence of signaling target binding on specific aptamer sequence or requirement of sandwich assays for two or more binding sites per target molecule). A recovery test demonstrated the feasibility of the developed target protein assay. Given the attractive characteristics, this aptameric recognition platform is expected to be a candidate for the detection of proteins and other ligands of interest in both fundamental and applied research.
Co-reporter:Zai-Sheng Wu, Songbai Zhang, Hui Zhou, Guo-Li Shen and Ruqin Yu
Analytical Chemistry 2010 Volume 82(Issue 6) pp:2221
Publication Date(Web):February 12, 2010
DOI:10.1021/ac901794w
A universal approach is proposed in this study for the development of an aptameric assay system for proteins based on aptamer structure-switching-triggered ligation-rolling circle amplification (L-RCA) upon target binding. The strategy chiefly depends on the competition for binding the aptamer probe between target protein and a complementary single-stranded DNA (CDNA) that can induce the circularization of the padlock probe. Introduction of target protein into the assay system inhibits the hybridization of the CDNA with the aptamer probe because of the formation of the target/aptamer duplex. The free CDNA can only hybridize with the padlock probe. With the assistance of DNA ligase, the padlock probe is circularized, and the subsequent RCA process can be accomplished by Phi 29 DNA polymerase. Each RCA product containing thousands of repeated sequences might hybridize with a large number of molecular beacons (detection probes), resulting in an enhanced fluorescence signal. In contrast, in the absence of target protein, no obvious change in the fluorescence intensity of the detection probe is observed. This signaling mode for target recognition and transduction events is based on the combination of aptamer recognition elements and L-RCA technology with high specificity and sensitivity. The proposed assay system not only exhibits excellent analytical characteristics (e.g., the detection limit on attomolar scale and a linear dynamic range of more than 3 orders of magnitude) but also possesses significant advantages over existing aptameric assays. The proposed strategy is universal since the sequences of aptamer probe, CDNA, and padlock probe could be easily designed to be compatible with the L-RCA based detection of other proteins without other conditions.
Co-reporter:Zai-Sheng Wu, Haixia Lu, Xueping Liu, Rong Hu, Hui Zhou, Guoli Shen and Ru-Qin Yu
Analytical Chemistry 2010 Volume 82(Issue 9) pp:3890
Publication Date(Web):April 15, 2010
DOI:10.1021/ac100422h
Gold nanoparticles (GNPs) possessing strong distance-dependent optical properties and high extinction coefficients have emerged as important colorimetric materials. Almost all colorimetric studies are based on two working mechanisms: sandwich cross-linking and non-cross-linking systems. In the present study, a new working mechanism, hairpin sticky-end pairing-induced GNP assembly, is introduced based on the discovery of unique aggregation behavior of aptamer-functionalized GNPs. The salt-induced aggregation of oligonucleotide probe-modified GNPs can readily occur due to the sticky-end pairing effect while addition of target molecules favors the formation of the hairpin structure of probe sequences and substantially inhibits the nanoparticle assembly. Along this line, we developed a proof-of-concept colorimetric homogeneous assay using immunoglobulin E (IgE) as an analyte model via transforming a commonly designed “light-down” colorimetric biosensor into a “light-up” one. From the point of view of both conformational transition of aptamer and steric bulk, oligonucleotide−GNPs display an additional stability upon binding to target molecules. The assay showed an extremely high sensitivity from both naked eye observations and absorbance measurements. Compared with almost all existing IgE sensing strategies, the proposed colorimetric system possesses a substantially improved analytical performance. Investigating the assembly behavior of hairpin aptamer-modified GNPs could offer new insight into the dependence of the GNP properties on the structure switching and open a new way to design signaling probes and develop colorimetric assay schemes.
Co-reporter:Xiaoyong Jin, Yuehua Fei, Liangliang Zhang, Xueping Liu, Guoli Shen and Ruqin Yu
Analyst 2010 vol. 135(Issue 1) pp:121-126
Publication Date(Web):10 Nov 2009
DOI:10.1039/B911672A
A new strategy for one-step, reusable and sensitive detection of a single-base mutation based on an electrochemical molecular switch is developed in the present work. When the hybridization reaction takes place in the presence of target DNA, the Fc-labeled terminal of the open switch molecule can be captured by the probe through the predesigned complementary bases of both sequences. By this method, a signal-on sensor featuring both generalizability and simplicity towards reagentless detection of DNA with sensitivity and selectivity electrochemical system is built on. The approach had been demonstrated with the identification of a single-base mutation of α-thalassemia point mutation in Hb Constant Spring codon 142 (TAA → CAA). The wild-type and mutant-type of the synthetic 16 mer DNA sequences as the model targets were successfully discriminated. The results showed that the response signal was linear to the logarithm of the target concentration in the range from 0.01 to 100 pM with a detection limit of 0.01 pM. The regeneration experiment demonstrated that the sensor interface can be easily and successfully regenerated. All these revealed that the present system is a promising candidate for single-base mutation discrimination.
Co-reporter:Suiping Wang, Yong Lei, Yun Zhang, Jian Tang, Guoli Shen, Ruqin Yu
Analytical Biochemistry 2010 Volume 398(Issue 2) pp:191-197
Publication Date(Web):15 March 2010
DOI:10.1016/j.ab.2009.11.029
Here we report a simple, biomolecular-friendly protocol for the fabrication of a hydroxyapatite nanowires array (HANWA) biosensor of spatial positioning, large surface area, and abundant adsorbing sites and its application to cyanide sensing. The fabrication of HANWA is performed by template-assisted electrodeposition. The well-aligned hydroxyapatite nanoarray is composed of vertical nanowires with a diameter of approximately 200 nm and an average length of 1 μm. The electrochemical biosensor for the determination of cyanide through its inhibitory effect on horseradish peroxidase (HRP) encapsulated by chitosan (CHIT) on the platform of HANWA is demonstrated. The current organic–inorganic hybrid nanostructure provides excellent enzyme–substrate contact with enzyme activity well maintained. The densely distributed HANWA with large surface area and abundant adsorbing sites can provide a favorable electrochemical interface for the construction of electrochemical biosensor. A sensitive detection limit of 0.6 ng ml−1 was obtained for cyanide. The proposed CHIT–HRP/HANWA biosensor has the advantages of spatial resolution, high sensitivity, rapid regeneration, and fast response associated with individual nanowires. It broadens the possible applications of chemosensors and biosensors, and it offers an alternative method for toxic substance determination. The new device holds great promise for environmental and food industrial monitoring of toxins.
Co-reporter:Chenrui Chen, Dengyou Liu, Zaisheng Wu, Qimei Luo, Guo-Li Shen, Ru-Qin Yu
Electrochemistry Communications 2009 Volume 11(Issue 10) pp:1869-1872
Publication Date(Web):October 2009
DOI:10.1016/j.elecom.2009.08.006
A label-free electrochemical immunosensor for the detection of protein analytes without redox-active centers is for the first time developed based on the combination of gold nanoparticles and the mediated charge transport through the multilayer films that is related to an electrocatalytic process. Given the low detection limit, high sensitivity and selectivity, the success achieved here seems plausibly to serve as a significant step toward the development of versatile label-free immunoassay.
Co-reporter:Yun Zhang, Hua Wang, Jinfang Nie, Hui Zhou, Guoli Shen, Ruqin Yu
Electrochemistry Communications 2009 Volume 11(Issue 10) pp:1936-1939
Publication Date(Web):October 2009
DOI:10.1016/j.elecom.2009.08.024
Encoded polymer films for electrochemical identification have been achieved by embedding different semiconductor nanocrystals into self-polymerized dopamine films. Such encoded polydopamine films based on mussel-inspired surface chemistry show high adhesive ability and can be created on a wide range of inorganic and organic materials, including noble metals, oxides, ceramics, and synthetic polymers. By incorporating different predetermined levels of various redox nanomarkers, the use of multi-film system composed of multiple, sequenced polydopamine identification films could theoretically generate nearly unlimited (>1012) distinct voltammetric signatures (electric codes).
Co-reporter:Suiping Wang, Limin Lu, Minghui Yang, Yong Lei, Guoli Shen, Ruqin Yu
Analytica Chimica Acta 2009 Volume 651(Issue 2) pp:220-226
Publication Date(Web):5 October 2009
DOI:10.1016/j.aca.2009.09.004
In this paper, for the first time, we introduced the seed-mediated method to the growth of cobalt hexacyanoferrate nanoparticles (CoNPs), using 3.5 nm gold nanoparticles as seeds and multiwalled carbon nanotubes (MWCNTs) as growth scaffold which would both show synergistic action toward the reduction of H2O2. Via gold seeds, the one-step fabrication of CoNPs on the glassy carbon electrode is simple without any linking reagents, which will ingeniously exert the electrochemical properties of cobalt hexacyanoferrate. Combined with glucose oxidase, the sensing surface is applied as a biosensor for glucose. The growth of CoNPs is a chemical deposition process around the small Au nanoseed particles. The nanoseeds bridge the CoNPs and CNTs to form a smart nanocomposite. Spherical CoNPs have a relatively moderate dispersion on the three-dimensional network of CNTs with relatively even diameter ca. 100 nm. Whereas, in the control experiments without gold seeds cobalt hexacyanoferrate can only form continuous films, of which the size is far from nanolevel and the catalytic ability is poor. The synthesis and fabrication/modification of CoNPs are simple and fast without prior preparation of CoNPs and lengthy process of cross-linking. The amount of the seeds and CNTs, growth time and concentration of growth solution were investigated. Scanning electron microscopy (SEM) and electrochemical method were used.
Co-reporter:Xuefang Jin, Xiaoyong Jin, Xueping Liu, Liguo Chen, Jianhui Jiang, Guoli Shen, Ruqin Yu
Analytica Chimica Acta 2009 Volume 645(1–2) pp:92-97
Publication Date(Web):10 July 2009
DOI:10.1016/j.aca.2009.04.041
An ultrasensitive piezoelectric method for the detection of the aflatoxin B1 (AFB1) based on the indirect competitive immunoassay and the biocatalyzed deposition amplification has been developed. In this method, the quartz crystal surface was coated with a self-assembled monolayer of 3-mercaptopropionic acid (MPA) for covalently immobilization of the BSA-AFB1 conjugate, which could compete with the free AFB1 for binding to the anti-AFB1 antibody (MsIgG). After the competitive immunoreaction, the horseradish peroxidase (HRP) labeled goat anti-mouse IgG (G-Anti-MsIgG) was introduced into the detection cell to combine with the anti-AFB1 antibody on the crystal surface. The enzyme labeled G-Anti-MsIgG as a biocatalyst could accelerate the oxidation of 4-chloro-1-naphthol by H2O2 to yield the insoluble product benzo-4-chlorohexadienone on the surface of quartz crystal microbalance (QCM), resulting in a mass increase that was reflected by a decrease in the resonance frequency of the QCM. The proposed approach could allow for the determination of AFB1 in the concentration range of 0.01–10.0 ng mL−1. Furthermore, several artificially contaminated milk samples were analyzed with good recoveries obtained, which demonstrated the suitability of the proposed method for detecting AFB1.
Co-reporter:Songbai ZHANG;Zaisheng WU;Ming XIE;Guoli SHEN;Ruqin YU
Chinese Journal of Chemistry 2009 Volume 27( Issue 3) pp:523-528
Publication Date(Web):
DOI:10.1002/cjoc.200990086
Abstract
A new strategy for homogeneous detection of DNA hybridization in single-step format was developed based on fluorescence quenching by gold nanoparticles. The gold nanoparticle is functionalized with 5′-thiolated 48-base oligonucleotide (probe sequence), whose 3′-terminus is labeled with fluorescein (FAM), a negatively charged fluorescence dye. The oligonucleotide adopts an extended configuration due to the electrostatic repulsion between negatively charged gold nanoparticle and the FAM-attached probe sequence. After addition of the complementary target sequence, specific DNA hybridization induces a conformation change of the probe from an extended structure to an arch-like configuration, which brings the fluorophore and the gold nanoparticle in close proximity. The fluorescence is efficiently quenched by gold nanoparticles. The fluorescence quenching efficiency is related to the target concentration, which allows the quantitative detection for target sequence in a sample. A linear detection range from 1.6 to 209.4 nmol/L was obtained under the optimized experimental conditions with a detection limit of 0.1 nmol/L. In the assay system, the gold nanoparticles act as both nanoscaffolds and nanoquenchers. Furthermore, the proposed strategy, in which only two DNA sequences are involved, is not only different from the traditional molecular beacons or reverse molecular beacons but also different from the commonly used sandwich hybridization methods. In addition, the DNA hybridization detection was achieved in homogenous solution in a single-step format, which allows real-time detection and quantification with other advantages such as easy operation and elimination of washing steps.
Co-reporter:Yun Zhang, Hua Wang, Jinfang Nie, Yuwei Zhang, Guoli Shen, Ruqin Yu
Biosensors and Bioelectronics 2009 Volume 25(Issue 1) pp:34-40
Publication Date(Web):15 September 2009
DOI:10.1016/j.bios.2009.06.011
A renewable, site-selective immobilization platform of microelectrode array (MEA) for multiplexed immunoassays has been initially developed using pencil graphite particles coated with gold layers as microelectrodes. The graphite particles available on the common pencil were utilized for directing the electro-deposition of gold layers with uniform microstructures which displayed a well-defined sigmoidal voltammetric response. In the concept-of-proof experiments, the resulting MEA platform was modified with functionalized monolayer, on which anti-human IgG antibodies could be stably immobilized in a site-selective way through binding chemistry to selectively capture human IgG antigens from the sample media. The subsequent introduction of anti-human IgG antibodies conjugated with 15 nm electro-active gold nanoparticles to recognize the captured IgG proteins resulted in a significant decrease in the interfacial electron-transfer resistance. High sensitive electrochemical quantification by gold nanoparticle-amplified impedance responses could thus be achieved. Experimental results show that the developed MEA sensor can allow for the detection of human IgG with wide linear range (0.05–100 ng ml−1) and sensitivity over 103 larger than that of the conventional, bulk gold electrode. The rapid regeneration of the used MEA platform can additionally be realized by a simple electrochemical treatment. The high selectivity of four individually addressable MEA platforms for multiple antigens in a single sample has been further demonstrated in the multiplexed immunoassay experiments. Such a site-selective immobilization strategy of MEA platform may open a new door towards the development of various simple, sensitive, cost-effective, and reusable biological sensors and biochips.
Co-reporter:Songbai Zhang, Zaisheng Wu, Guoli Shen, Ruqin Yu
Biosensors and Bioelectronics 2009 Volume 24(Issue 11) pp:3201-3207
Publication Date(Web):15 July 2009
DOI:10.1016/j.bios.2009.03.012
A new strategy for label-free and sensitive detection of single-nucleotide polymorphism (SNP) based on ligation-rolling circle amplification (L-RCA) and intercalating of methylene blue is developed in the present work. A circular template generated by ligation upon the recognition of a point mutation on DNA targets was amplified isothermally by the Phi29 DNA polymerase. The elongation products were hybridized with the capture probe immobilized on the gold electrode. Methylene blue was used as the intercalator to indicate the mutation occurrence. Making use of the high amplification efficiency of Phi29 DNA polymerase and the remarkable precision of Escherichia coli DNA ligase in differentiating mismatched bases at the ligation site, as low as 40 amol mutated strands can be detected, and the positive mutation detection was achieved with a wild-type to mutant ratio of 5000:1, indicating high sensitivity and high fidelity. Furthermore, the proposed sensor is label-free and easy to regenerate compared with most of RCA strategies which utilized an immobilized primer and a labeled detection probe, making it a promising candidate for SNP genotyping.
Co-reporter:Xiaoyong Jin, Xuefang Jin, Liguo Chen, Jianhui Jiang, Guoli Shen, Ruqin Yu
Biosensors and Bioelectronics 2009 Volume 24(Issue 8) pp:2580-2585
Publication Date(Web):15 April 2009
DOI:10.1016/j.bios.2009.01.014
A simple, rapid and highly sensitive piezoelectric immunosensor has been proposed and applied to detect aflatoxin B1 (AFB1). It is unlikely that direct binding of small molecules such like AFB1 to the piezoelectric sensor surface could result in a satisfactory detection limit and sensitivity. Thus, indirect competitive immunoassay technique had been used for the detection of the target and gold nanoparticles (GNP) been employed as a ‘weight label’ to the secondary antibody for amplifying the response. This method is proven in its ability to detect AFB1 down to a level of 0.01 ng mL−1 in artificially contaminated milk, which is comparable to or even exceeding the sensitivity of microtitre plate ELISA. Furthermore, the frequency responses of the immunoassay are linearly correlated to the logarithm of AFB1 concentration in the range of 0.1–100 ng mL−1. The sensor could be regenerated under very mild conditions simply by immersing the sensor into glycine buffer solution to desorb the combined antibody. It is found that the as-renewed sensor could be reused at least 9 runs without obvious loss of sensing sensitivity.
Co-reporter:Yanhong Tang, Yu Cao, Suiping Wang, Guoli Shen, Ruqin Yu
Sensors and Actuators B: Chemical 2009 Volume 137(Issue 2) pp:736-740
Publication Date(Web):2 April 2009
DOI:10.1016/j.snb.2008.12.011
A novel amperometric sensor for hydrogen peroxide (H2O2) was developed based on palladium nanoparticles (NPs) in-situ formed on the electrode surface. Poly(acrylic acid) (PAA) was first electrodeposited onto a gold electrode. Then Pd2+ were chemically adsorbed within the PAA network, and subsequently reduced by hydrazine hydrate to form palladium NPs. The size and density of palladium NPs can be easily controlled through controlling the amount of metal ions in the film. The PAA-templated Pd NPs displayed excellent electrocatalytical response to the reduction of H2O2. Under optimal conditions, linear relationship was observed for H2O2 reduction in the concentration range from 10 μM to 25 mM at the applied potential of −0.1 V and the detection limit was 5 μM. The resulted sensor shows fast response and good stability. By varying the metal catalyst and by conjugating biomolecules with the free carboxyl groups of PAA, a variety of new chemical and biosensors could be constructed.
Co-reporter:Jishan Li, Jian-Hui Jiang, Xiang-Min Xu, Xia Chu, Cheng Jiang, Guoli Shen and Ru-Qin Yu
Analyst 2008 vol. 133(Issue 7) pp:939-945
Publication Date(Web):24 Apr 2008
DOI:10.1039/B717853K
Multiplex single nucleotide polymorphisms analysis has found a great demand in human genetics and pharmacogenetics. The present study reports a novel approach for a genotyping assay that could achieve simultaneous identification of multiple point mutations via a ligase-mediated gold nanoparticle assembly. Based on the allelic specificity of DNA ligase, gold nanoparticles modified by oligonucleotide probes perfectly matched to the DNA targets were assembled into a thermally-stable aggregate, while a single-base mismatch would result in the dissociation of the gold nanoparticle assembly at high temperature. Then, DNA targets and their point mutations could be differentiated using a multi-step temperature elevation analysis monitored by ultraviolet-visible measurements. This approach offered a direct colorimetric discrimination of multiple point mutations without stringent temperature control. The proposed approach is demonstrated using a model system for the identification of single-base mutations in codon 17 and position −28 of the β-thalassemia gene. The results reveal that the wild and the mutant types could be simultaneously determined successfully. Owing to its ease of operation and high specificity, it was expected that the proposed procedure might hold great promise in both research-oriented and clinical genomic assays.
Co-reporter:Yanjun Ding, Jia Liu, Xiaoyong Jin, Haixia Lu, Guoli Shen and Ruqin Yu
Analyst 2008 vol. 133(Issue 2) pp:184-190
Publication Date(Web):21 Nov 2007
DOI:10.1039/B713824E
Hybrid composites are of special scientific interest for biochemical applications wherein the abilities to modulate the morphology and property of the hybrid material are important. In this paper, the formation of poly-L-lysine/hydroxyapatite/carbon nanotube (PLL/HA/CNT) hybrid nanoparticles is described and a general design strategy for an immunosensing platform has been proposed on the basis of PLL/HA/CNT nanocomposite adsorption of antibodies. Quartz crystal microbalance (QCM) used as a model transducer and the detection performances of the resulting immunosensor were investigated by use of the immuno-system of carbohydrateantigen 19-9 (CA19-9), an important indicator in the diagnosis of clinical cancers. The hybrid nanocomposite was characterized by the transmission electron microscope (TEM), scanning electron microscope (SEM) and Fourier transform-infrared (FT-IR) spectrum measurements. The frequency response characteristics for the processes of immobilization and immunoreaction of anchored anti-CA19-9 antibodies were studied in detail. It was found that the developed sensing interface has some advantages such as the activation-free immobilization and the high antigen-binding activities of antibodies. The as-prepared immunosensor can allow for the determination of CA19-9 in the concentration range of around 12.5–270.0 U ml−1. Such an interface design with the hybrid nanocomposite should be tailored as a new alternative used for biosensor design.
Co-reporter:Xiao-Yong JIN;Xue-Fang JIN;Yan-Jun DING;Jian-Hui JIANG;Ru-Qin YU
Chinese Journal of Chemistry 2008 Volume 26( Issue 12) pp:2191-2196
Publication Date(Web):
DOI:10.1002/cjoc.200890390
Abstract
A simple piezoelectric immunoagglutination assay technique with antibody-modified nanoparticles has been developed for direct quantitative detection of protein. The proposed technique is based on the specific agglutination of goat anti-hIgG-coated silica (or gold) nanoparticles in the presence of human immunoglobulin G (hIgG), which causes a frequency change and is monitored by a piezoelectric device. The antibody modified on the probe surface would combine with antibody-coated nanoparticles in the presence of antigen (hIgG) when the surface agglutination reaction took place, which couples both the mass effect and viscoelastic effect acting on the probe. The results indicate that the background interference can be substantially minimized and the probe signal can be observably multiplied. In addition, the surface of the modified probe and that after combining the complex of immunoagglutination were imaged by scanning electronic microscopy (SEM). Moreover, an optimization of assay medium composition with the addition of poly(ethylene glycol) (PEG) serving as immunoagglutination enhancer and sodium chloride to control the ion-strength was investigated. The frequency responses of the immunoagglutination assay were found to correlate well with the hIgG concentration with a detection limit of 84 ng·mL−1.
Co-reporter:Yanjun Ding, Haixia Lu, Guorong Shi, Jia Liu, Guoli Shen, Ruqin Yu
Biosensors and Bioelectronics 2008 Volume 24(Issue 2) pp:228-232
Publication Date(Web):15 October 2008
DOI:10.1016/j.bios.2008.03.020
A novel yeast cell-based strategy for the immobilization of antibodies using an amine-terminated self-assembly film has been proposed. A quartz crystal microbalance sensor was according fabricated by coupling with anti-prostate specific antigen (anti-PSA) for PSA immunoassay. The crystal was modified with cysteamine to deposit yeast cells, on which anti-PSA antibodies were immobilized. The surface topologies of the as-prepared crystals were characterized by use of scanning electron microscopy. In contrast to the traditional glutaraldehyde (GLU) approach, the yeast cells could allow antibody molecules bound with higher bioactivity and achieve better immunoreaction capability. Results indicate that immunoassay prepared using the developed yeast cell-binding procedure exhibits increased analytical performance compared with that produced using the GLU cross-linking procedure. A PSA serum concentration in the range of 5.0–604.0 ng ml−1 can be determined by this new system.
Co-reporter:Ming-Hui Yang, Feng-Li Qu, Ya-Shuang Lu, Guo-Li Shen, Ru-Qin Yu
Talanta 2008 Volume 74(Issue 4) pp:831-835
Publication Date(Web):15 January 2008
DOI:10.1016/j.talanta.2007.07.013
Platinum nanoparticles (PtNPs) attached to glass slide surface was successfully prepared by using a simple in situ chemical reduction method. In this method, a ∼10 nm gold layer was first sputtered uniformly onto the glass slide surface, PtNPs could be grown directly on the gold layer by immersing the glass slide into the grown solution containing H2PtCl4 and ascorbic acid. The gold layer sputtered uniformly serves as “seed” for the following growth of PtNPs and high dense of PtNP modified film can be prepared. Control experiment without the gold layer found no obvious formation of PtNPs indicating the importance of the “seed”. The electrocatalytic effect of the PtNP film was investigated with the detection of hydrogen peroxide and for the fabrication of biosensors. Glucose oxidase was selected and directly electrodeposited onto the PtNPs modified surface. The resulting biosensor has a fast response time (<10 s) with wide linear range (5 × 10−6 to 2 × 10−2). The fabrication method is simple, convenient and can be used for the mass fabrication of biosensors. The present preparation method of PtNPs modified film could be used for the preparation of other metal nanoparticle and find electrochemical applications as well as for optical uses.
Co-reporter:Fengli Qu, Aiwu Shi, Minghui Yang, Jianhui Jiang, Guoli Shen, Ruqin Yu
Analytica Chimica Acta 2007 Volume 605(Issue 1) pp:28-33
Publication Date(Web):12 December 2007
DOI:10.1016/j.aca.2007.10.013
Prussian blue nanowire array (PBNWA) was prepared via electrochemical deposition with polycarbonate membrane template for effective modification of glassy carbon electrode. The PBNWA electrode thus obtained was demonstrated to have high-catalytic activity for the electrochemical reduction of hydrogen peroxide in neutral media. This enabled the PBNWA electrode to show rapid response to H2O2 at a low potential of −0.1 V over a wide range of concentrations from 1 × 10−7 M to 5 × 10−2 M with a high sensitivity of 183 μA mM−1 cm−2. Such a low-working potential also substantially improved the selectivity of the PBNWA electrode against most electroactive species such as ascorbic acid and uric acid in physiological media. A detection limit of 5 × 10−8 M was obtained using the PBNWA electrode for H2O2, which compared favorably with most electroanalysis procedures for H2O2. A biosensor toward glucose was then constructed with the PBNWA electrode as the basic electrode by crosslinking glucose oxidase (GOx). The glucose biosensor allowed rapid, selective and sensitive determination of glucose at −0.1 V. The amperometric response exhibited a linear correlation to glucose concentration through an expanded range from 2 × 10−6 M to 1 × 10−2 M, and the response time and detection limit were determined to be 3 s and 1 μM, respectively.
Co-reporter:Zai-Sheng Wu, Song-Bai Zhang, Meng-Meng Guo, Chen-Rui Chen, Guo-Li Shen, Ru-Qin Yu
Analytica Chimica Acta 2007 Volume 584(Issue 1) pp:122-128
Publication Date(Web):12 February 2007
DOI:10.1016/j.aca.2006.11.003
An unmodified gold nanoparticle-based colorimetric assay system in homogeneous format has been developed using hydrogen peroxide (H2O2) as a model analyte. H2O2 is added to o-phenylenediamine/horseradish peroxidase solution, and allowed to react for 10 min. Then, unmodified gold nanoparticles that serve as “reaction indicators” are added to the reaction solution. The resulting mixture color changes dramatically from red to blue. The reason is that azoaniline, a horseradish peroxidase-catalyzed oxidation product, induces the nanoparticle aggregation. Using this approach, H2O2 can be semiquantitatively determined over the concentration range of ∼4 orders of magnitude by the naked eye. If the observed peak intensity at 420 nm is used for the construction of the calibration plot, hydrogen peroxide can be accurately determined down to concentration levels of 1.3 × 10−6 M. Compared with the conventional electrochemical protocol, this sensing system offers several important advantages: (1) ability to be monitored by the naked eye, (2) avoiding the need of surface modification of electrodes or gold nanoparticles and (3) detection in homogeneous solution. It is worthy of note that this efficient and convenient strategy is also suitable for the detection of other species, such as glucose and cholesterol.
Co-reporter:Yan-Jun Ding;Hua Wang;Jian-Hui Jiang;Ru-Qin Yu
Chinese Journal of Chemistry 2007 Volume 25(Issue 9) pp:1288-1293
Publication Date(Web):17 SEP 2007
DOI:10.1002/cjoc.200790239
A simple, rapid and sensitive impedance immunosensor based on iridium oxide (IrOx) thin film for the detection of carcinoembyronic antigen (CEA) in human sera has been proposed. Gold electrode was electrochemically modified with IrOx thin film and simultaneously functionalized with protein A (PA) to bind anti-CEA antibodies in an orientated way. It has been found that the antibody loading amount was dependent on the PA concentration and the deposition time of IrOx matrix. Under the optimized experimental conditions, the electron transfer resistances obtained were linearly related to the CEA concentration ranging from 36.2 to 460.0 ng/mL, with a detection limit of 28.0 ng/mL. Analytical results of clinical samples from cancer patients show that the proposed immunoassay is reasonably comparable with the chemiluminescence immunoassay (CLIA), indicating the feasibility of using the proposed method for CEA immunoassay in clinical laboratory.
Co-reporter:Song-Bai Zhang, Zai-Sheng Wu, Meng-Meng Guo, Guo-Li Shen, Ru-Qin Yu
Talanta 2007 Volume 71(Issue 4) pp:1530-1535
Publication Date(Web):15 March 2007
DOI:10.1016/j.talanta.2006.07.036
A novel immunoassay strategy based on combination of chitosan (CHIT) and a gold nanoparticle (GNP) label has been developed. The susceptibility of CHIT to further chemical modifications due to the abundant amino groups is explored in order to covalently immobilize antibody (Ab) onto the (3-aminopropyl) triethoxysilane derivatized glass slide by cross-linking with glutaraldehyde (GA). After incubating in antigen (Ag) solution, the obtained substrate is immersed in GNP labeled antibody solution for signal generation. The two steps were repeated alternatively for three times, forming multilayer of gold nanoparticles via antigen–antibody specific reaction. Ultraviolet-visible (UV–vis) absorption spectrum is recorded to obtain quantitative information about the specific antigen. The presented immunoassay strategy is applied for determination of human serum albumin (HSA) as a model analyte. The immunoassay of HSA is specific. Compared to previous correlative work, the proposed immunosensing strategy shows some advantages, such as improved sensitivity as much more gold nanoparticles can be coupled to the functionalized surface making use of the abundant amino groups of CHIT. Moreover, a significantly extended linear detection range of 8.0–512.0 μg/mL is gained under the optimized experimental conditions. In particular, the presented biosensing method shows low cost and simplicity, and only a conventional UV–vis detector is involved.
Co-reporter:Zai-Sheng Wu;Meng-Meng Guo
Analytical and Bioanalytical Chemistry 2007 Volume 387( Issue 8) pp:2623-2626
Publication Date(Web):2007 April
DOI:10.1007/s00216-007-1126-1
Guanine-rich DNA sequences commonly form helical quadruplex structures via Hoogsteen hydrogen bonds. The aggregation behavior of the nanoparticles, which are functionalized with four-guanine-terminated 27-base sequences at a nanoparticle-to-DNA ratio of 1:60, is investigated. To some extent, the guanine-quadruplex structures between the gold nanoparticles (GNPs) promote nanoparticle aggregation. However, the coordination site of the metal ion on the nanoparticle surface is partially passivated: the stability of guanine-rich DNA-GNPs is slightly lower than that of the usual DNA-GNPs, and the metal-ion specificity of nanoparticle assembly is substantially decreased. Thus, a mechanism for the aggregation of guanine-rich sequence-modified GNPs is proposed. It is possible to obtain a stable guanine-rich sequence-functionalized nanoparticle solution at high ionic strength by regulating guanine-rich DNA sequences. The controllability of guanine-rich sequence-modified nanoparticles makes the secondary structure of DNA a potentially useful candidate for DNA analysis and disease diagnostics.
Co-reporter:T. Deng;J.-S. Li;J.-H. Jiang;G.-L. Shen;R.-Q. Yu
Advanced Functional Materials 2006 Volume 16(Issue 16) pp:
Publication Date(Web):19 SEP 2006
DOI:10.1002/adfm.200600149
A class of novel core/shell near-IR fluorescent nanoparticles have been prepared through co-hydrolysis of a hydrophobic silicon alkoxide, hexadecyltrimethoxysilane, and tetraethyl orthosilicate as the dye-doped core, followed by the formation of a hydrophilic shell via hydrolysis of tetraethyl orthosilicate in a water-in-oil microemulsion. The co-hydrolysis of hexadecyltrimethoxysilane and tetraethyl orthosilicate produces a highly hydrophobic core for the entrapment of a low-cost near-IR fluorescence dye, methylene blue. Experimental investigation of this particular core/shell nanoparticle in comparison with conventional dye-doped silica nanoparticles demonstrates that the hydrophobic core enables the doped dye to exhibit enhanced fluorescence and show improved stability to dye leaching and exogenous quenchers. In contrast to rhodamine B doped silica nanoparticles, the near-IR fluorescent nanoparticles also show negligible background fluorescence and low inner-filtration interference in complex biological systems such as whole blood. This advantage is utilized for the development of an immunoagglutination assay method based on fluorescence-anisotropy measurement for the detection of alpha fetoprotein (AFP) in whole-blood samples. The results reveal that increase in fluorescence anisotropy is linearly correlated with AFP concentration in the range 1.9–51.9 ng mL–1.
Co-reporter:Minghui Yang, Fengli Qu, Yashuang Lu, Yan He, Guoli Shen, Ruqin Yu
Biomaterials 2006 Volume 27(Issue 35) pp:5944-5950
Publication Date(Web):December 2006
DOI:10.1016/j.biomaterials.2006.08.014
Platinum nanowire arrays can be grown by electrodeposition in polycarbonate membrane, with the average diameter of the nanowires about 250 nm and the height about 2 μm. The nanowire array prepared by the proposed method can be considered as nanoelectrode array (NEA) with nanoelectrode density of 5×108 cm−2. While the NEA can improve the signal-to-noise ratio and decrease the detection limit, the high surface area of the platinum NEA circumvents the problem of conventional platinum electrodes associated with the limited electroactive site. The platinum NEA can direct response to hydrogen peroxide at low potential of 0 V with wide linear range (1×10−7–6×10−2 m) and sensitivity 50 times larger than that of the conventional platinum electrode. With the absorption of glucose oxidase onto the ordered NEA surface, the spatially patterned glucose oxidase improves greatly the resulting biosensor. The biosensor can achieve interference free determination of glucose with wide linear range (10−6–3×10−2 m). The sensitivity of the glucose biosensor is one-fifth of the sensitivity toward hydrogen peroxide, indicating high efficiency of signal transduction. The biosensor was used to determine glucose in real blood samples, and the glucose contents determined by the present biosensor were in agreement with the results of existing method.
Co-reporter:Zai-Sheng Wu, Gu-Zhen Zhou, Jian-Hui Jiang, Guo-Li Shen, Ru-Qin Yu
Talanta 2006 Volume 70(Issue 3) pp:533-539
Publication Date(Web):15 October 2006
DOI:10.1016/j.talanta.2006.01.004
It is difficult to detect glucose by surface-enhanced Raman spectroscopy (SERS) due to the small normal Raman cross-section and the weak adsorption of glucose molecules on the surface of noble metal. A simple and fast method is proposed in this paper for the detection of glucose based on SERS signal of the enzyme reaction product and the difficulties have been circumvented. Gold colloids modified by horseradish peroxidase and glucose oxidase (HRP/GOD-gold colloids) are added to the mixture of o-phenylenediamine and glucose, and the resulting solution is allowed to react at room temperature for 5 min. Azoaniline, an azo compound with strong Raman scattering, is generated and the Raman scattering of this reaction product is enhanced when adsorbed on gold colloids. The intensity of the SERS spectrum is used for assessment of glucose content. The dynamic signal range provided by this analytical system is 0.50–32 mM, which covers the normal clinical range for glucose in blood from 3.5 to 6.1 mM. The detection limit is about 0.46 mM. The interference effect of several proteins on glucose detection is also investigated and has shown to have no effect on the measurement of glucose by the described technique.
Co-reporter:Yunhui Yang, Zhijie Wang, Minhui Yang, Mengmeng Guo, Zhaoyang Wu, Guoli Shen, Ruqin Yu
Sensors and Actuators B: Chemical 2006 Volume 114(Issue 1) pp:1-8
Publication Date(Web):30 March 2006
DOI:10.1016/j.snb.2005.04.005
A renewable potentiometric urease inhibition biosensor based on self-assembled gold nanoparticles has been developed for the determination of mercury ions. Gold nanoparticles were chemically adsorbed on the PVC-NH2 matrix membrane pH electrode surface containing N,N-didecylaminomethylbenzene (DAMAB) as a neutral carrier and urease was then immobilized on the gold nanoparticles. The response characteristics of the DAMAB/PVC-NH2 pH-sensitive membrane and the effects of the size of nanoparticles have been investigated in detail. The linear range of determination of Hg2+ was 0.09–1.99 μmol L−1 with a detection limit of 0.05 μmol L−1. The advantages of self-assembled immobilization are low detection limit, fast response and ease regeneration. The assembled gold nanoparticles and inactive enzyme layers denatured by Hg2+ can be rinsed out via a saline solution with acid and alkali successively. This sensor is generally of great significance for inhibitor determination, especially in comparison with expensive base transducers.
Co-reporter:Xia Chu, Zi-Long Zhao, Guo-Li Shen, Ru-Qin Yu
Sensors and Actuators B: Chemical 2006 Volume 114(Issue 2) pp:696-704
Publication Date(Web):26 April 2006
DOI:10.1016/j.snb.2005.06.014
A novel dendritic amplification procedure has been developed for microgravimetric quartz crystal microbalance (QCM) immunosensing by the application of antibody-functionalized Au nanoparticles as the primary amplifying probe and a dendritic-type immunocomplex of protein A- and antibody-modified Au nanoparticles as the secondary amplifying probe. Goat anti-human immunoglobulin G (IgG) antibody is orientedly immobilized on the Au electrode surface of QCM through pre-assembled protein A and acts as the sensing interface to recognize the analyte, human IgG. The primary amplification of the recognition process is implemented via the interaction of the sensing interface with the antibody-functionalized Au nanoparticles, and the secondary dendritic amplification is performed through interaction with the immunocomplex of protein A- and antibody-modified Au nanoparticles. The dendritic-type amplified sensing procedure is also confirmed by the UV–vis absorption measurements. The frequency decreases of the primary amplified and the secondary amplified sensing process are observed to be linearly dependent upon the IgG concentration in the range of 10.9 ng ml−1 to 10.9 μg ml−1 with a detection limit of 3.5 ng ml−1, while in the absence of the amplification processes, the antigen–antibody recognition event can only be detected for a IgG concentration as high as 10.9 μg ml−1.
Co-reporter:Shuzhen Tan, Jianhui Jiang, Guangyu Shen, Guoli Shen, Ruqin Yu
Analytica Chimica Acta 2005 Volume 547(Issue 2) pp:215-220
Publication Date(Web):22 August 2005
DOI:10.1016/j.aca.2005.05.041
A general route for preparation of dye-encapsulated polymer particles via an emulsion polymerization process has been described. 1-Naphthaleneboronic acid (NBA) was encapsulated, the resultant particles were used as a fluorescence probe for cilnidipine assay based on fluorescence quenching. The sensitivity of NBA-encapsulated probe to cilnidipine was largely improved in comparison with that of free NBA. The probe showed a linear response toward cilnidipine over the concentration range of 2.0 × 10−7 to 1.1 × 10−5 mol l−1, with high sensitivity, fast response time, and good selectivity.
Co-reporter:Jing Wu, Hua Wang, Liu Fu, Zhaopeng Chen, JianHui Jiang, Guoli Shen, Ruqin Yu
Talanta 2005 Volume 65(Issue 2) pp:511-517
Publication Date(Web):30 January 2005
DOI:10.1016/j.talanta.2004.07.045
Catechins are strong autoxidant to produce steady intermediate in alkali solution. In present work, we, for the first time, developed a electrochemical method based on ruthenium tris (2, 2′) bipyridyl (Ru(bpy)33+) modified boron-doped diamond (BDD) electrode to investigate the electrochemical reduction of catechin autoxidation intermediate with its existence verified by the electron spin resonance (ESR). The reduction peak potential was observed at −855.5 mV, not appearing either in acid solution (pH 2) containing catechins or in oxidized catechin solution (pH 12). Moreover, the effects of pH, ascorbic acid, Cu2+, Fe2+ and autoxidation time are investigated, demonstrating the reduction peak being really the reduction of catechin autoxidation intermediate. It is found that the peak current is proportional to scan rate, indicative of a surface confined reduction process. Sensitive amperometric response was obtained covering linear range from 0.3268 μM to 0.1591 mM. The determination of catechin in commercial preparations using this method shows satisfactory results comparable with those of the traditional methods.
Co-reporter:Bing Liu, Yun-Hui Yang, Zhao-Yang Wu, Hua Wang, Guo-Li Shen, Ru-Qin Yu
Sensors and Actuators B: Chemical 2005 Volume 104(Issue 2) pp:186-190
Publication Date(Web):24 January 2005
DOI:10.1016/j.snb.2004.04.093
A potentiometric acetylcholinesterase biosensor based on pH-sensitive PVC membrane with plasma-polymerized ethylenediamine film has been proposed. Glow discharge plasma technique was utilized to deposit a film containing amino groups on the surface of pH-sensitive PVC membrane. Such an approach makes it possible to fabricate a very simple self-mounted acetylcholinesterase membrane directly attached to PVC pH-sensing electrode surface. The deposition conditions were optimized and the optimum plasma polymerization parameters were as follows: applied power, 75 W; pressure, 130 Pa; plasma exposure time, 60 min and flow rates, 10 ml min−1. Two neutral carriers, DOODA and DAMAB were compared as the pH-carrier, and the biosensor based on DAMAB showed better response characteristics. The effect of pH of the medium was also examined. The potential responses of biosensor increase with the acetylcholine chloride concentration over the concentration range of 10−6 to 10−1 mol dm−3 and the detection limit is 0.002 mmol dm−3 in pH 8.0 PB buffer solution. The biosensor was employed more than 200 times in 20 days while the maximum response span of biosensor retained 90%.
Co-reporter:Xia Chu, Xin Fu, Ke Chen, Guo-Li Shen, Ru-Qin Yu
Biosensors and Bioelectronics 2005 Volume 20(Issue 9) pp:1805-1812
Publication Date(Web):15 March 2005
DOI:10.1016/j.bios.2004.07.012
A novel, sensitive electrochemical immunoassay has been developed based on the precipitation of silver on colloidal gold labels which, after silver metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a glassy-carbon electrode. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) as a model. The influence of relevant experimental variables, including the reaction time of antigen with antibody, the dilution ratio of the colloidal gold-labeled antibody and the parameters of the anodic stripping operation, upon the peak current was examined and optimized. The anodic stripping peak current depended linearly on the IgG concentration over the range of 1.66 ng ml−1 to 27.25 μg ml−1 in a logarithmic plot. A detection limit as low as 1 ng ml−1 (i.e., 6 × 10−12 M) human IgG was achieved, which is competitive with colorimetric enzyme linked immuno-sorbent assay (ELISA) or with immunoassays based on fluorescent europium chelate labels. The high performance of the method is attributed to the sensitive ASV determination of silver (I) at a glassy-carbon electrode (detection limit of 5 × 10−9 M) and to the catalytic precipitation of a large number of silver on the colloidal gold-labeled antibody.
Co-reporter:Yun Zhang, Hua Wang, Bani Yan, Yuwei Zhang, Jishan Li, Guoli Shen, Ruqin Yu
Journal of Immunological Methods (20 March 2008) Volume 332(Issues 1–2) pp:103-111
Publication Date(Web):20 March 2008
DOI:10.1016/j.jim.2007.12.019
This paper reports a simple, sensitive, and reusable piezoelectric immunosensor using magnetic hydroxyapatite (HAP)/γ-Fe2O3/Au nanocomposite. Use of porous HAP nanocrystals embedded with γ-Fe2O3 and colloidal gold nanoparticles resulted in a multifunctional HAP/γ-Fe2O3/Au nanocomposite. Under optimized conditions, the biocompatible nanocomposites were exploited for direct adsorption of large quantities of rabbit anti-human immunoglobulin G antibodies (anti-hIgG) with well-preserved immunoactivity. In a homogeneous bulk solution, the hIgG analytes were captured by the anti-hIgG-derivatized immunocomposites followed by magnetic separation/enrichment onto a bovine serum albumin (BSA)-sealed QCM probe before measuring. This QCM immunosensor can quantitatively determine concentrations of hIgG ranging from ~ 20 to 800 ng/ml, with a detection limit of ~ 15 ng/ml. Moreover, regeneration of the immunosensor can be simply realized by canceling the controllable magnetic field. With the possibility of performing the analysis automatically and considering its ease of use, high sensitivity, and good reusability, this magnetic separation-assisted QCM immunosensor may have great potential to be further tailored as a general and promising alternative for a broad range of practical applications.
Co-reporter:Songbai Zhang, Zai-Sheng Wu, Liping Qiu, Hui Zhou, Guoli Shen and Ruqin Yu
Chemical Communications 2010 - vol. 46(Issue 19) pp:NaN3383-3383
Publication Date(Web):2010/03/17
DOI:10.1039/B926646A
Ferrocene-conjugated oligonucleotides that can form intermolecular guanine (G)-quadruplexes are prepared and used as signaling probes for detecting target DNA, improving substantially assay characteristics (e.g. a considerably wider linear dynamic range and lower detection limit).
Co-reporter:Zaisheng Wu, Hui Zhou, Songbai Zhang, Xiaobing Zhang, Guoli Shen and Ruqin Yu
Chemical Communications 2010 - vol. 46(Issue 13) pp:NaN2234-2234
Publication Date(Web):2010/01/18
DOI:10.1039/B919585H
A pendulum-type DNA nanoswitch, which can perform a reversible on/off molecular motion at an about 9.1-nm scale is developed as a proof-of-concept, and the sequence-specific recognition and quantification of target olignucleotides are demonstrated utilizing this screening scheme.
Co-reporter:Rong Hu, Zai-Sheng Wu, Songbai Zhang, Guo-Li Shen and Ruqin Yu
Chemical Communications 2011 - vol. 47(Issue 4) pp:NaN1296-1296
Publication Date(Web):2010/11/22
DOI:10.1039/C0CC03884A
A highly sensitive and selective electrochemical DNA signaling scheme, which identifies the point mutation existing in target DNA sequence, is developed based on the combination of label-free hairpin probe (HP)/DNA endonuclease with zirconia (ZrO2) nanoparticle film, representing a promising screening platform for the accurate diagnosis of infections and genetic diseases as well as for environmental and forensic applications.
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