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Ultrasensitive immunoassay

Kenneth Squire, Xianming Kong, Paul LeDuff, Gregory L Rorrer, Alan X Wang
Fluorescence biosensing is one of the most established biosensing methods, particularly fluorescence spectroscopy and microscopy. These are two highly sensitive techniques but require high grade electronics and optics to achieve the desired sensitivity. Efforts have been made to implement these methods using consumer grade electronics and simple optical setups for applications such as point-of-care diagnostics, but the sensitivity inherently suffers. Sensing substrates, capable of enhancing fluorescence are thus needed to achieve high sensitivity for such applications...
May 16, 2018: Journal of Biophotonics
Ao Huang, Luning Zhang, Weiwei Li, Zeyu Ma, Shi Shuo, Tianming Yao
We report an ultrasensitive immunoassay for tau protein-a key marker of Alzheimer's disease. This sensing platform relies on graphene oxide (GO) surfaces conjugated with anti-human tau antibody to provide quantitative binding sites for the tau protein. The GO quenches standard fluorescein isothiocyanate labelled tau (tau-FITC) when tau protein and tau-FITC are both present and compete for the binding sites. This change in fluorescence signal can be used to quantitate tau protein. In contrast with traditional enzyme-linked immunosorbent assay (ELISA), our method does not require enzyme-linked secondary antibodies for protein recognition nor does it require an enzyme substrate for optical signal generation...
April 2018: Royal Society Open Science
Zhili Han, Jiangnan Shu, Qiaoshi Jiang, Hua Cui
In this work, the eletrochemiluminescence (ECL) behavior of Cu2+ /cysteine complexes and N-(aminobutyl)-N-(ethylisoluminol) (ABEI) functionalized gold nanoparticles combined with chitosan (Cu2+ -Cys-ABEI-GNPs-CS) were studied by cyclic voltammetry and a double-step potential, which exhibited excellent ECL properties without any coreactant. It was found that the ECL intensity of Cu2+ -Cys-ABEI-GNPs-CS could increase at least one order of magnitude compared with that of Cu2+ -Cys-ABEI-GNPs. Furthermore, a coreactant-free and label-free ECL immunosensor has been established for the determination of early acute myocardial infarction biomarker copeptin based on luminescent immuno-gold nanoassemblys consisting of Cu2+ -Cys-ABEI-GNPs-CS and immuno-gold nanoparticles prepared by connecting copeptin antibody with trisodium citrate stabilized gold nanoparticles...
April 25, 2018: Analytical Chemistry
Zhen Qin, Wei Xu, Shuai Chen, Jun Chen, Jing Fu Qiu, Chao Rui Li
The authors describe an electrochemical immunoassay for ultrasensitive direct determination of the carcinoembryonic antigen (CEA). A nanocomposite consisting of octahedral Cu2O nanocrystals covered with gold nanoparticles was utilized to modify a glassy carbon electrode which gives a strongly enhanced chronoamperometric signal for H2 O2 which is used as an electrochemical probe. The morphology and elemental composition of the the nanocomposite was studied by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy...
April 24, 2018: Mikrochimica Acta
Linglin Xie, Xia Yang, Yi He, Ruo Yuan, Yaqin Chai
In this work, we adopted polyacrylamide gel contained the zinc finger peptide(PZF)as a "Lock" of Raman signal and zinc ions (Zn2+) as a sensitive "key" which was converted from target-captured ZnO NPs to achieve the ultrasensitive detection of prostate-specific antigen (PSA). Owing to the "lock" effect from PZF, the SERS tag toluidine blue (TB) connected on AgNPs-coating silica wafer was sheltered leading to low Raman response. Meanwhile, target PSA can specifically connect with antibody 2 coupled ZnO nanocomplexes (ZnO@Au@Ab2) and antibody 1 coupled magnetic (CoFe2O4@Au@Ab1) through sandwich immunoassay...
April 16, 2018: ACS Applied Materials & Interfaces
Mohammad Hasanzadeh, Solmaz Tagi, Elham Solhi, Ahad Mokhtarzadeh, Nasrin Shadjou, Aziz Eftekhari, Soltanali Mahboob
The accurate quantification of the level of breast cancer specific protein CA 15-3 in serum is crucial for cancer prognosis. This work, a novel and sensitive label-free immunoassay based on gold nanospear (Au NSs) electrochemically assembled onto thiolated graphene quantum dots (CysA/GQDs) for the detection of CA 15-3 antibodies. The CysA/Au NSs/GQDs hybrid interface provides a large surface area for the effective immobilization of CA 15-3 antigens, as well as it ascertains the bioactivity and stability of immobilized CA 15-3 antigens...
April 2, 2018: International Journal of Biological Macromolecules
Zhen Ma, Huisheng Zhuang
Benzo[a]pyrene (BaP), a type of polycyclic aromatic hydrocarbon, is widely distributed in the environment. In this study, BaP immunogen and coating antigen were respectively prepared by different methods, and the specific antibody targeting the BaP analyte was obtained. Moreover, gold nanoparticles modified with the specific polyclonal antibody and thiol-capped DNA were prepared as biological probes. Based on the work above, an ultrasensitive biological probe enhanced real-time immuno-polymerase chain reaction (BP-rt-iPCR) assay was developed to detect BaP in several environmental samples...
March 15, 2018: Acta Biochimica et Biophysica Sinica
Ruiguo Wang, Wei Zhang, Peilong Wang, Xiaoou Su
An ultrasensitive paper based lateral flow assay is described for rapid and simultaneous fluorometric detection of several β-agonists including clenbuterol and its chemical analogues (mabuterol, brombuterol, cimaterol, cimbuterol, bromchlorbuterol and banbuterol). A nonspecific monoclonal antibody (mAb) against clenbuterol and its analogues was prepared and employed in a competitive immunoassay where mAb conjugated to fluorescent nanoparticles and free β-agonists compete for the binding sites. This enables rapid screening for the 7 β-agonists in a single run that takes about 8 min...
2018: Mikrochimica Acta
Andrew Geoffrey Bourne Thompson, Connie Luk, Amanda J Heslegrave, Henrik Zetterberg, Simon H Mead, John Collinge, Graham S Jackson
OBJECTIVES: A blood-based biomarker of neuronal damage in sporadic Creutzfeldt-Jakob disease (sCJD) will be extremely valuable for both clinical practice and research aiming to develop effective therapies. METHODS: We used an ultrasensitive immunoassay to measure two candidate biomarkers, tau and neurofilament light (NfL), in serum from patients with sCJD and healthy controls. We tested longitudinal sample sets from six patients to investigate changes over time, and examined correlations with rate of disease progression and associations with known phenotype modifiers...
February 27, 2018: Journal of Neurology, Neurosurgery, and Psychiatry
Viviana A Carcamo Yañez, Jens C Göpfert, Markus Otto, Hayrettin Tumani, Andreas Peter, Thomas O Joos
Procalcitonin (PCT) is well established as a highly specific biomarker for the detection of bacterial infections and sepsis. However, the currently available diagnostic tests are not able to detect very low or very early increases of PCT or even baseline levels in healthy individuals or patients with non-bacterial infections. In order to be able to detect these very low concentrations of PCT, a sandwich immunoassay was developed using high sensitivity Single Molecule Array technology (Simoa). The assay was thoroughly validated and applied to analyze human cerebrospinal fluid (CSF) and serum samples from patients with bacterial or viral meningitis as well as CSF, serum, and K2 EDTA plasma from healthy control subjects...
November 16, 2017: High-throughput
María L Scala-Benuzzi, Julio Raba, Galo J A A Soler-Illia, Rudolf J Schneider, Germán A Messina
We report a novel and innovative electrochemical paper-based immunocapture assay (EPIA) to address the need for ultrasensitive detection of emerging pollutants without regulatory status and whose effects on environment and human health are not completely yet understood. In particular, we present the application of this system toward highly sensitive detection of the emerging pollutant ethinyl estradiol (EE2). The EPIA approach is based on the use of paper microzones modified with silica nanoparticles (SNs) and anti-EE2 specific antibodies for capture and preconcentration of EE2 from river water samples...
March 20, 2018: Analytical Chemistry
Mingsha Jie, Songcheng Yu, Fei Yu, Lie Liu, Leiliang He, Yanqiang Li, Hongquan Zhang, Lingbo Qu, Peter de B Harrington, Yongjun Wu
BACKGROUND: In the present study, a novel highly sensitive magnetic enzyme chemiluminescence immunoassay (MECLIA) was developed to detect fumonisin B1 (FB1 ) in cereal samples. The gold-coated magnetic nanoparticles (Fe3 O4 @Au, GoldMag) were used as solid phase carrier to develop a competitive CLIA for detecting FB1 , in which FB1 in samples would compete with FB1 -ovalbumin coated on the surface of Fe3 O4 @Au nanoparticles for binding with FB1 antibodies. Successively, horseradish peroxidase labeled goat anti-rabbit IgG (HRP-IgG) was conjugated with FB1 antibodies on the microplate...
February 12, 2018: Journal of the Science of Food and Agriculture
Di Zhang, Li Huang, Bing Liu, Haibin Ni, Liangdong Sun, Enben Su, Hongyuan Chen, Zhongze Gu, Xiangwei Zhao
Rapid and sensitive quantification of multiplex proteins in a wide concentration range is challenging in high throughput analysis. Herein, we proposed a lateral flow assay (LFA) based on core-shell surface enhanced Raman scattering (SERS) nanotags for multiplex and quantitative detection of cardiac biomarkers for the early diagnosis of acute myocardial infarction (AMI). In practice, Raman dyes (RDs) were embedded into the interior-gap of silver core and gold shell nanoparticles (NPs) to form SERS nanotags as labels instead of gold colloids and three test lines were employed in the strip for the detection of three cardiac biomarkers, Myo, cTnI, and CK-MB, respectively...
May 30, 2018: Biosensors & Bioelectronics
Ying Zhou, Yanqing Yu, Yaqin Chai, Ruo Yuan
Herein, a novel electrochemiluminescence resonance energy transfer (ERET) strategy between in situ electrogenerated silver nanoclusters (AgNCs) as the donor and Ru(bpy)2 (5-NH2 -1,10-phen)Cl2 (Ru(II)) as the acceptor was reported, which was applied for the construction of a ultrasensitive immunosensor for the determination of apolipoprotein-A1 (Apo-A1). Notably, the Ag NCs were in suit electro-reducted on glassy carbon electrode (GCE) based on a simple, fast and controllable electrochemical technique, which acted as not only biocompatible ECL emitters, but also protein immobilization platform via Ag-N or Ag-S bond...
May 1, 2018: Talanta
Zhen Cao, Yu Zhu, Yang Liu, Shurong Dong, Xin Chen, Fan Bai, Shengxin Song, Junxue Fu
A nanoscale insulator-based dielectrophoresis (iDEP) technique is developed for rapid enrichment of proteins and highly sensitive immunoassays. Dense arrays of nanorods (NDs) by oblique angle deposition create a super high electric field gradient of 2.6 × 1024 V2 m-3 and the concomitant strong dielectrophoresis force successfully traps small proteins at a bias as low as 5 V. 1800-fold enrichment of bovine serum albumin protein at a remarkable rate of up to 180-fold s-1 is achieved using oxide coated Ag nanorod arrays with pre-patterned sawtooth electrodes...
March 2018: Small
Tian Wen, Chao Huang, Yi Zhang, Xiaoyan Zeng, Wendong Liu, Zhenbang Jiao, Xiling Guo, Yongjun Jiao
A rapid and sensitive two-step time-resolved fluorescence immunoassay (TRFIA) was developed for the detection of Shiga toxin 2 (Stx2) and its variants in Shiga toxin-producing Escherichia coli (STEC) strains. In sandwich mode, a monoclonal antibody against Stx2 was coated on a microtiter plate as a capture antibody. A tracer antibody against Stx2 labeled with europium(III) (Eu3+ ) chelate was then used as a detector, followed by fluorescence measurements using time-resolved fluorescence. The sensitivity of Stx2 detection was 0...
May 2018: Luminescence: the Journal of Biological and Chemical Luminescence
Anita Talan, Annu Mishra, Sergei A Eremin, Jagriti Narang, Ashok Kumar, Sonu Gandhi
Chlorpyrifos (chl) is an organophosphate pesticide extensively used in agriculture and highly toxic for human health. Fluorine doped tin-oxide (FTO) based electrochemical nanosensor was developed for chlorpyrifos detection with gold nanoparticles (AuNPs) and anti-chlorpyrifos antibodies (chl-Ab). AuNPs provides high electrical conductivity and specific resistivity, thus increases the sensitivity of immunoassay. High electrical conductivity of AuNPs reveals that it promotes the redox reaction for better cyclic voltammetry...
May 15, 2018: Biosensors & Bioelectronics
Sitian Tang, Huawei Shen, Yixiong Hao, Zhenglan Huang, Yiyi Tao, Yang Peng, Yongcan Guo, Guoming Xie, Wenli Feng
Circulating tumor cells (CTCs), as the cellular origin of metastasis, are cancer cells that break away from a primary tumor and circulate in the peripheral blood. And they provide a wealth of information about tumor phenotype. Here, this work reported a novel ultrasensitive immunoassay protocol for the detection of CTCs by using Pt@Ag nanoflowers (Pt@AgNFs) and AuNPs/Acetylene black (AuNPs/AB) nanomaterial. In the established approach, AuNPs/AB nanomaterial was used as substrate material to increase the specific surface area and enhance the conductivity of the gold electrode...
May 1, 2018: Biosensors & Bioelectronics
Peng Liu, Xueen Fang, Hongmei Cao, Mingli Gu, Jilie Kong, Anmei Deng
With the development of proteomics and the continuous discovery of biomarkers of trace proteins, it is important to accurately quantify low abundance protein, especially in urine for clinical diagnostics. In this paper, we reported a novel nano-biotinylated liposome-based immuno-loop-mediated isothermal amplification (LI-LAMP) for the ultrasensitive detection of REG1A (a biomarker for pancreatic ductal adenocarcinoma (PDAC) in urine) with high specificity. The detection range was 1µg/mL to 1fg/mL, with a detection limit of 1fg/mL, and no cross-reactivity was observed to occur in this assay...
March 1, 2018: Talanta
Lu Yang, Wenfang Deng, Chang Cheng, Yueming Tan, Qingji Xie, Shouzhuo Yao
Herein, carbon dots (CDs)-encapsulated breakable organosilica nanocapsules (BONs) were facilely prepared and used as advanced fluorescent labels for ultrasensitive detection of Staphylococcus aureus. The CDs were entrapped in organosilica shells by cohydrolyzation of tetraethyl orthosilicate and bis[3-(triethoxysilyl)propyl]disulfide to form core-shell CDs@BONs, where hundreds of CDs were encapsulated in each nanocapsule. Immunofluorescent nanocapsules, i.e., anti-S. aureus antibody-conjugated CDs@BONs, were prepared to specifically recognize S...
January 31, 2018: ACS Applied Materials & Interfaces
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