Application In Specific Detection Research Articles

Emerging Technologies for Fluorescence-Based Optical Test Strip Readers

Fluorescence-based optical test strip readers are used to detect and quantify fluorescent signals from immunoassay test strips in medicine, especially for point-of-care applications. The design of optical systems including light sources and detection systems in these devices is not only indispensable but also the most critical part for specific detection applications. This study aims to provide detailed information about fluorescence-based optical test strip readers, existing and emerging technologies, and their contributions to the design of the device. The most commonly used technologies of light sources and detection systems have been discussed and compared for the ideal design. Arc and Xenon lamps may not be appropriate for portable and low-cost devices as they are larger and more costly when compared to LEDs and laser diodes. Photodiodes and CMOS detectors can be used for the design of low-cost, portable fluorescence-based optical test strip readers as they are cheaper and smaller in size when compared to CCDs and PMTs. Both light source and detector should be chosen according to the application priorities and spectral characteristics of the fluorescent molecule by integrating them with proper optical elements like filters, mirrors, etc. This study contributes to the people who are interested in the design of fluorescence-based optical test strip readers as it serves as a guideline for the optical test strip reader systems.

Fluorescence quenching properties of Au-Ag-Pt tri-metallic nanorod: The application in specific detection of alpha-fetoprotein

In this paper, the fluorescence quenching characteristics of Au-Ag-Pt core–shell nanorods have been studied.Due to nonradiative energy transformation, the fluorescence emission intensity of bovine serum albumin (BSA) could be greatly quenched.It has been found that the quenching effect of Au-Ag-Pt core–shell nanorods could be optimized by adjusting the concentration of chloroplatinic acid.Based on the fluorescence quenching properties of Au-Ag-Pt core–shell nanorods, Au-Ag-Pt trimetal fluorescence quenching nanoprobe has been prepared, and the specificity of alpha-fetoprotein (AFP) detection has also been realized.In order to guarantee the sensing specificity, the surface modification including carboxyl replacement, carboxyl activation and antibody connection have been performed on Au-Ag-Pt core–shell nanorods.By using the principle of specific combination of antigen and antibody, the specific detection of AFP has been realized with a lower detection limit of 4.0 pg/mL, and the linear detection range spans a scope from 0.03 to 0.5 ng/mL.Interference experiments and the actual samples detection results show that the Au-Ag-Pt trimetal core–shell nanorod probes have good anti-interference and repeatability.

Water-soluble AIE-active Fluorescent Organic Nanoparticles: Design, Preparation and Application for Specific Detection of Cyanide in Water and Food Samples.

A dilactosyl-dicyanovinyl-functionalized tetraphenylethene (TPELC) was designed, synthesized and used for ratiometric sensing of cyanide. TPELC was comprised of three moieties (tetraphenylethylene, dicyanovinyl group and lactose unit) in one molecule, making TPELC water-soluble and aggregation-induced emission (AIE)-active and selectively reactive to cyanide. Compared with other reported fluorescent probes containing dicyanovinyl group, TPELC is the first AIE luminogen to be assembled as fluorescent organic nanoparticles (FONs) for sensing of cyanide in water without the use of surfactant or the help of organic solvents based on the nucleophilic addition reaction. The detection mechanism was verified by liquid chromatograph mass spectrometry experiments and by protonation of cyanide to reduce the nucleophilicity of cyanide. In addition, TPELC was used for detection of the cyanide content of food samples and test strips were developed to simplify the detection procedure.

An amperometric biosensor for specific detection of glycated hemoglobin based on recombinant engineered fructosyl peptide oxidase

Here, we present a specific biosensor based on the detection of glycated hemoglobin (HbA1c) proteolytic digestion product, fructosyl valyl histidine (Fru-ValHis). A recombinant engineered fructosyl peptide oxidase (FPOX) enzyme with improved specificity was immobilized on the electrode surface modified by chitosan (CHIT), graphene oxide (GO) and gold nanoparticles (AuNPs). The biosensor exhibited a linear response toward different concentrations of Fru-ValHis ranging from 0.1 to 2 mM with a sensitivity of 8.45 µA mM-1 cm−2. Detection limit of the current biosensor for Fru-ValHis was 0.3 µM as the lowest quantity required giving a signal to a background. Analytical recovery of added Fru-ValHis in whole blood was 95.1–98.35% for FPOX/AuNPs/GO/CHIT/FTO electrode. For Fru-ValHis determination by FPOX-AuNPs-GO-CHIT/FTO electrode, within-run coefficient of variation (CV) was between 1.3% and 2.4% and between run CV was between 2.1% and 3.5%. A significant change in electron transfer resistance after the incubation of FPOX-modified electrode with Fru-ValHis was observed, while no response was achieved with control, indicating specific measurement of Fru-ValHis. Moreover, designed biosensor measured HbA1c in human blood samples and the results were well agreed with that obtained with NORUDIA™ N HbA1c diagnostic kit. Overall, suitable specificity of the engineered FPOX made the bioelectrode responded well to the Fru-ValHis level, which demonstrates a promising application for specific detection of HbA1c biomarker.

Synthesis and properties of cardo-type polyimides containing hydroxyl groups for application in specific detection of fluoride ion

Here, four cardo-type polyimides containing hydroxyl groups have been successfully synthesized by one-step solution polymerization of a hydroxyl-containing fluorene diamine monomer and various commercial dianhydride monomers. The obtained PIs with high molecular weights were readily soluble in many polar solvents. Simultaneously, they still maintain the excellent thermal stability (the 5% and 10% weight loss temperatures over 480 °C and 510 °C in nitrogen, respectively) and the high glass transition temperatures (Tgs, 342–442 °C). Furthermore, PI films show high tensile strength (>78 MPa) and relatively high optical transparency (over 82% at 500 nm), except PI-4. Utilizing that hydroxyl group in PI chain is able to form H-bond interaction with F−, these hydroxyl-containing PIs in DMSO solution are successfully applied as colorimetric chemosensors for detection of F− with high selectivity and sensitivity. Finally, the PI film chemosensors is also used for visual and reversible sensing of F−, which enables them to be a fast and portable test kit for visible detection of F−.

Water-soluble AIE-Active Fluorescent Organic Nanoparticles: Design, Preparation and Application for Specific Detection of Cysteine over Homocysteine and Glutathione in Living Cells.

Water-soluble ratiometric AIE-active fluorescent organic nanoparticles 2OA-FON for the specific sensing of cysteine over other biothiols are reported. The obtained amphiphilic probe included olefin aldehyde as recognizing unit, tetraphenylethylene as fluorescence reporter and lactose moiety as a hydrophilic group. This work provides a general design strategy based on the introduction of a sugar moiety into a hydrophobic AIEgen to develop ratiometric water-soluble fluorescent organic nanoparticles.

A review of titanium dioxide and its highlighted application in molecular imprinting technology in environment

Over the past 40 years, Titanium dioxide (TiO2) has focused continuously growing worldwide concern due to its novel characteristics such as large specific surface area, powerful oxidation strength, and chemical stability. Nevertheless, its poor selectivity restricted its promising application in specific detection and selective removal of target pollutants in mixing solution, especially the low concentration of highly toxic pollutants. Importantly, concerning on the formation of selective sites with the memory of a template, molecular imprinting technologies (MIT) can selectively remove the template and their structural analogues. With the appealing characteristics of combination of TiO2 and MIT, the TiO2-based molecular imprinting polymers (MIPs) can selectively detect and photo-degrades targets, and are widely utilized in chemical sensors, solid-phase extraction and artificial antibodies. Thus, we review the significant progress of MIT and highlighted applications of TiO2-based MIPs during the past 10 years, especially emphasis on their origins, structure, functions, affecting factors, up-to-date development and main challenges faced in improving their working efficiency. Additionally, the review also covered the ecotoxicological effects of TiO2-based MIPs nanomaterials (NMs) in environment and human beings.

A resonant cantilever based particle sensor with particle-size selection function

This paper reports on a novel resonant-gravimetric micro-cantilever based particle sensor for detecting particles (e.g. PM2.5) in air. A row of micro-pillars with desired separation-distance are integrated in a micro-channel that is embedded in the cantilever as a filter to select the particles of desired size. When particles containing air are pumped into the micro-channel, the particles with desired diameters are trapped by the micro-pillars near the free-end of the cantilever, which results in a detectable resonant frequency shift of the micro-cantilever. After detection the sensor can be recovered by reversing the direction of the air flow to blow off the trapped particles and the sensor is ready for the next detection. By tuning the spacing between the barrier bars, the diameters of the trapped particles can be customized for specific detection applications. The complicated structure of the resonant sensor is fabricated by using a novel IC-foundry compatible single-sided surface micromachining technique, with single-side-polished (1 1 1) silicon wafers on a low-cost non-SOI substrate. The sensor prototype has experimentally exhibited excellent real-time detection performance to standard polystyrene micro-spheres, with the resolution of the single particle being distinguishable. The sensor is promising in applications of air pollution monitoring and analysis.

A high gradient and strength bioseparator with nano-sized immunomagnetic particles for specific separation and efficient concentration of E. coli O157:H7

Sample pretreatment is a key to rapid screening of pathogens for prevention and control of foodborne diseases. Magnetic immunoseparation is a specific method based on antibody–antigen reaction to capture the target bacteria and concentrate them in a smaller-volume buffer. The use of nano-sized magnetic particles could improve the separation efficiency of bacteria but require much higher gradient and strength magnetic field. In this study, a strong magnetic bioseparator with a mean field strength of 1.35 T and a mean gradient of 90 T/m was developed with the use of the 30 nm and 180 nm magnetic particles to specifically separate and efficiently concentrate foodborne bacterial pathogens using Escherichia coli O157:H7 as a model bacterium. The polyclonal antibodies against E. coli were evaluated using Dot ELISA analysis for their good affinity with the target bacteria and then used to modify the surface of the magnetic nanoparticles by 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) method and streptavidin-biotin binding. The magnetic particle concentrations were optimized to be 40 µg/ml and 100 µg/ml for the 30 nm and 180 nm particles, respectively, the immunoreaction time was optimized to be 45 min for both sizes of particles, and the separation times were optimized to be 60 min and 2 min for the 30 nm and 180 nm particles, respectively. The total magnetic separation time was 2 h and 1 h for the 30 nm and 180 nm particles, respectively. The experimental results demonstrated that the bioseparator with the use of either 30 nm or 180 nm immunomagnetic particles could achieve a separation efficiency of >90% for E. coli O157:H7 at the concentrations ranging from 102 to 105 cfu/ml. No obvious interferences from non-target foodborne pathogens, such as Salmonella Typhimurium and Listeria innocua, were found. For overall consideration of the consuming time, the cost, and the separation efficiency, the 180 nm magnetic particles are practical for rapid screening applications; however the 30 nm magnetic particles are preferable for specific detection applications. This immunomagnetic bioseparator can be integrated with either conventional culture methods or some rapid detection methods, such as biosensors and PCR, for more sensitive detection of foodborne pathogens.

A Conjugated Aptamer-Gold Nanoparticle Fluorescent Probe for Highly Sensitive Detection of rHuEPO-α

We present here a novel conjugated aptamer-gold nanoparticle (Apt-AuNPs) fluorescent probe and its application for specific detection of recombinant human erythropoietin-α (rHuEPO-α). In this nanobiosensor, 12 nm AuNPs function as both a nano-scaffold and a nano-quencher (fluorescent energy acceptor), on the surface of which the complementary sequences are linked (as cODN-AuNPs) and pre-hybridized with carboxymethylfluorescein (FAM)-labeled anti-rHuEPO-α aptamers. Upon target protein binding, the aptamers can be released from the AuNP surface and the fluorescence signal is restored. Key variables such as the length of linker, the hybridization site and length have been designed and optimized. Full performance evaluation including sensitivity, linear range and interference substances are also described. This nanobiosensor provides a promising approach for a simple and direct quantification of rHuEPO-α concentrations as low as 0.92 nM within a few hours.

A real-time PCR method targeting a gene sequence encoding 16S rRNA processing protein, rimM, for detection and enumeration of Streptococcus thermophilus in dairy products

Abstract A real-time PCR method targeting a gene sequence encoding 16S rRNA processing protein, rimM, for specific detection of Streptococcus thermophilus was developed. The designed real-time PCR primers and probe were specific for S. thermophilus JCM20026, LMG6896, LMG18311, OJT101, OJT102 but not Enteroccocus spp., Lactococcus lactis subsp. lactis, and Streptococcus salivarius which are phylogenetically closely related to S. thermophilus and are difficult to identify using culture-based methods. The linear range of the developed real-time PCR method was from 2.7 to 8.6 log CFU ml −1 with an amplification efficiency of 96%. Minor differences (about 0.4 log CFU ml −1 ) were observed between counts of S. thermophilus obtained by culture and real-time PCR method in plain yoghurt and yoghurt containing fruits. Therefore, the developed real-time PCR method could be of potential application in specific detection and accurate enumeration of S. thermophilus in a wide range of dairy products.

Radiation detection devices made from CVD diamond

CVD diamond is a remarkable material for the fabrication of radiation detectors. The radiation hardness, chemical resistance and high-temperature operational capabilities of diamond motivate its use in the fabrication of devices operating in hostile environments such as those encountered in the nuclear industry and high-energy physics. Synthetic diamond can be grown using the microwave plasma-enhanced chemical vapour deposition technique. However, the material exhibits several difficulties that require its optimization in terms of the sensitivity or stability of the detector response. Also, defect level influence on the detection characteristics was studied as they are the cause of an observed instability. We report here on the techniques that can be used in the preparation of films that satisfy the requirements for a range of specific detection applications. This can be achieved by fine-tuning the growth conditions and the device preparation steps. Films with thicknesses ranging from 5 to 500 μm have been used for detector fabrication. Here we present the recent developments studied at CEA in Saclay for material optimization of a few applications including radiation hard counters, x-ray intensity, shape and beam position monitors, solar blind photodetectors and high dose rate gamma-meters.