Minimum Detectable Concentration Research Articles

Surface-Enhanced Raman Spectroscopy Sensor Integrated with Ag@ZIF-8@Au Core-Shell-Shell Nanowire Membrane for Enrichment, Ultrasensitive Detection, and Inactivation of Bacteria in the Environment.

A core-shell-shell sandwich material is developed with silver nanowires as the core, ZIF-8 as an inner shell, and gold nanoparticles as the outer shell, namely, Ag@ZIF-8@Au nanowires (AZA-NW). Then, the synthesized AZA-NW is transformed into a surface-enhanced Raman spectroscopy (SERS) sensor (named M-AZA) by the vacuum filtration method and used to enrich, detect, and inactivate traces of bacteria in the environment. The M-AZA sensor has three main functions: (1) trace bacteria are effectively enriched, with an enrichment efficiency of 91.4%; (2) ultrasensitive detection of trace bacteria is realized, with a minimum detectable concentration of 1 × 101 CFU/mL; (3) bacteria are effectively killed up to 92.4%. The shell thickness of ZIF-8 (5-75 nm) is controlled by adjusting the synthesis conditions. At an optimum shell thickness of 15 nm, the effect of gold nanoparticles and ZIF-8 shell on the sensor's stability, SERS activity, and antibacterial performance is investigated. The simulation of the SERS sensor using the finite difference time domain (FDTD) method is consistent with the experimental results, theoretically demonstrating the role of the gold nanoparticles and the ZIF-8 shell. The sensor also shows excellent stability, safety, and generalizability. The campus water sample is then tested on-site by the M-AZA SERS sensor, indicating its potential for practical applications.

Harnessing Graphdiyne for Selective Cu2+ Detection: A Promising Tool for Parkinson's Disease Diagnostics and Pathogenesis.

Cu2+ accelerates the viral-like propagation of α-synuclein fibrils and plays a key role in the pathogenesis of Parkinson's disease (PD). Therefore, the accurate detection of Cu2+ is essential for the diagnosis of PD and other neurological diseases. The Cu2+ detection process is impeded by substances that have similar electrochemical properties. In this study, graphdiyne (GDY), a new kind of carbon allotrope with strong electron-donating ability, was utilized for the highly selective detection of Cu2+ by taking advantage of its outstanding adsorption capacity for Cu2+. Density functional theory (DFT) calculations show that Cu atoms are adsorbed in the cavity of GDY, and the absorption energy between Cu and C atoms is higher than that of graphene (GR), indicating that the cavity of GDY is favorable for the adsorption of Cu atoms and electrochemical sensing. The GDY-based electrochemical sensor can effectively avoid the interference of amino acids, metal ions and neurotransmitters and has a high sensitivity of 9.77 μA·μM-1·cm-2, with a minimum detectable concentration of 200 nM. During the investigating pathogenesis and therapeutic process of PD with α-synuclein as the diagnostic standard, the concentration of Cu2+ in cells before and after L-DOPA and GSH treatments were examined, and it was found that Cu2+ exhibits high potential as a biomarker for PD. This study not only harnesses the favorable adsorption of the GDY and Cu2+ to improve the specificity of ion detection but also provide clues for deeper understanding of the role of Cu2+ in neurobiology and neurological diseases.

Research on infrared spectroscopy detection of furfural content in transformer oil based on acetonitrile extraction

Abstract The stable operation of power transformers depends on the oil-paper insulation system, in which the aging degree of insulating paper is the key to evaluate the remaining life of the transformer. Currently, methanol extraction is widely used to detect the furfural content in oil to evaluate the aging state of insulating paper, but it ignores the influence of methanol produced during the operation of the transformer on the extraction results. To address this issue, this paper proposes a new method that can replace methanol extraction for detecting furfural in oil through simulation and experiment. Firstly, through simulation and experiment, it is proved that the strong vibration absorption peaks at 1677 cm-1 for furfural carbonyl and 2240 cm-1 for acetonitrile cyano can be used to establish a new method for extracting furfural content in oil using acetonitrile. A quantitative model between the concentration x of furfural in the furfural-acetonitrile mixed solution and the area y of the infrared absorption peak at 1677 cm-1 is established, with a goodness of fit of 0.9974. Secondly, a comparison between direct detection and acetonitrile extraction methods is conducted. The results show that direct detection is simple to operate, but the minimum detection concentration is 40mg/L, which is difficult to meet practical requirements. Acetonitrile extraction can reduce the minimum detection concentration to 0.1mg/L. At the same time, the extraction conditions are analyzed to determine the extraction ratio of 30, extraction times of 5, and extraction rate of 60%. Finally, the proposed detection method is applied to thermal aging tests on insulating paper of different types. The experimental results show that the proposed method has good repeatability and improves the detection resolution of furfural content. This paper combines infrared spectroscopy with acetonitrile extraction technology to open up a more efficient and practical new method for detecting furfural content in transformer oil.

Progressive expansion of albumin adducts for organophosphorus nerve agent traceability based on single and group adduct collection.

Protein adducts are important biological targets for traceability of organophosphorus nerve agents (OPNAs). Currently, the recognized biomarkers that can be used in actual samples in the field of chemical forensics only include Y411 in albumin and the active nonapeptide in butyrylcholinesterase (BChE). To explore stable and reliable protein adducts and increase the accuracy of OPNAs traceability further, we gradually expanded OPNAs-albumin adducts based on single and group adduct collection. Several stable peptides were found via LC-MS/MS analysis in human serum albumin (HSA) exposed to OPNAs in a large exposure range. These adducts were present in HSA samples exposed to OPNAs of each concentration, which provided data support for the reliability and stability of using adducts to trace OPNAs. Meanwhile, the formation mechanism of OPNAs-cysteine adduct was clarified via computer simulations. Then, these active sites foundand modified peptides were used as raw materials for progressive expansion of albumin adducts. We constructed an OPNAs-HSA adducts group, in which a specific agent is the exposure source, and three or more active peptides constitute data sets for OPNAs traceability. Compared with single or scattered protein adducts, the OPNAs-HSA adduct group improves OPNAs identification by mutual verification using active peptides or by narrowing the identity range of theexposure source. We also determined the minimum detectable concentration of OPNAs for the adduct group. Two or more peptides can be detected when there is an exposure of 50 times the molar excess of OPNAs in relation to HSA. This improved the accuracy of OPNAs exposure and identity confirmation. A collection of OPNAs-albumin adducts was also examined. The collection was established by collecting, classifying, and integrating the existing albumin adducts according to the species to which each albumin belongs, the types of agents, and protease. This method can serve as a reference for discovering new albumin adducts, characteristic phosphonylated peptides, and potential biomarkers. In addition, to avoid a false negative for OPNAs traceability using albumin adducts, we explored OPNAs-cholinesterase adducts because cholinesterase is more reactive with OPNAs than albumin. Seven active peptides in red blood cell acetylcholinesterase (RBC AChE) and serum BChE can assist in OPNAs exposure and identity confirmation.

A fieldable process for sensitive detection of airborne viruses via electrophoresis-based RNA enrichment

Sensitive, on-site, virus detection is a requirement for timely action against the spread of airborne infection since ultra-low in-air viral concentrations can readily infect individuals when inhaled. Here, we consider a fieldable biosensing process that incorporates a fast RNA enrichment step in order to concentrate viral RNA in a small volume prior to RT-qPCR. The enrichment approach uses electrophoresis in an RT-qPCR-compatible buffer, and allows to concentrate the RNA by nearly 5-fold within only 10 min. In order to place this performance into context, we analyzed the minimum detectable concentration of a low-cost, fieldable, biosensing process that uses electrostatic precipitation for air sampling, heating for viral RNA extraction, and then RNA enrichment, followed by RT-qPCR. With enrichment, we estimated an in-air concentration of 5654 genome copies (gc)/m3 with a 100% detection rate and an in-air concentration of 4221 gc/m3 with a 78.6% detection rate. Given that the concentrations of common viruses, such as influenza and SARS-CoV-2, in several indoor spaces are between 5800 and 37000 gc/m3, we conclude that enrichment allows a detection that is sufficiently sensitive for practical applications.

Dual laser based optical feedback cavity enhanced absorption spectroscopy by polarization division multiplexing

This article presents a dual laser-based optical feedback cavity-enhanced absorption spectroscopy technique using polarization division multiplexing. The technique involves two laser beams with orthogonal polarization that enter a V-shaped cavity from two injection directions. This allows for independent control of feedback phase and eliminates the need for an optical component to combine the beams. The two lasers are detected separately at the two ends of the cavity. Additionally, a differential process is proposed to mitigate residual interference between the two lasers. By employing this technique, simultaneous detection of CH4, CO2 and H2O is achieved, resulting in a detection sensitivity of approximately 2 × 10−11 cm−1. Despite using a moderate cavity finesse in our spectrometer, the minimal detectable concentration for the gases is comparable to that of superior gas analyzers using cavity ringdown spectroscopy (CRDS).

Broadband and high-enhancement-factor integrated long-wave infrared sensor using the photonic crystal assisted subwavelength grating waveguide

In this paper, a broadband and high-enhancement-factor integrated long-wave infrared sensor using the photonic crystal assisted subwavelength grating waveguide is presented, optimized, and analyzed in detail. By reasonably designing the structure and optimizing the corresponding parameters, the dispersion relationship can be adjusted to realize a relatively flat band and the slow-light effect can be introduced to improve the interaction between light and matter so that large and stable slow-light enhancement factors are obtained in a wide wavelength range, achieving high-performance detection of multiple types of matter. For the optimized sensor, the operating bandwidth from 7.65142 to 7.71125 µm is realized. When C2H2, HNO3, CH4, H2O2, or N2O is treated as the target matter, the corresponding slow-light enhancement factor at 7.677 µm, 7.661 µm, 7.670 µm, 7.7 µm, or 7.705 µm is, respectively, 4.3405, 4.3432, 4.3194, 5.1584, or 5.9745; the relevant sensitivity is 0.2394Wmol−1L, 0.3466Wmol−1L, 0.3639Wmol−1L, 0.2058Wmol−1L, or 0.4791Wmol−1L; and the minimum detectable concentration is 0.6032 ppb, 0.4164 ppb, 0.3966 ppb, 0.7019 ppb, or 0.3010 ppb.

Trace detection of cadmium (II) ions based on an excessively tilted fiber grating

Cadmium (Cd2+) ion is one of the most crucial industrial pollutants that cause serious harm to the human body. We proposed and experimentally demonstrated a highly sensitive Cd2+ sensor based on hydrogel coated excessively tilted fiber grating. The hydrogel with the functional monomer of the allyl thiourea can specifically bind to Cd2+, and hence forming a complex. The grating excites high order cladding modes, and ensures a sufficient interaction between the light and hydrogel binding to Cd2+, providing highly sensitive monitoring. The results show that the sensor can detect 0-160 pM Cd2+ in aqueous solution. The maximum sensitivity is 10600 nm/µM, and the minimum detection concentration is 20 pM (about 0.004 ppb), which is much less than that of the international standard (3 ppb). The proposed sensor exhibits high sensitivity, ultra-low detection limit, specificity, and a compact structure, offering potential as a tool for Cd2+ detection in aqueous solution.

A new strategy for constructing 3D hybrid graphene/Au/rectangular pyramids PMMA on a flexible SERS substrate for trace molecule detection

Surface enhanced Raman spectroscopy (SERS) has attracted interest in the fields of hazardous substance detection and food safety. However, its limited sensitivity and SERS signal consistency inhibit the widespread use of SERS technology. Herein, a novel approach for the fabrication of a graphene/Au NP/rectangular pyramid PMMA hybrid SERS substrate (Gr/Au/RP PMMA) with high uniformity and sensitivity is presented. The Gr/Au/RP PMMA substrate is machined by indentation firstly, then following wet etching of the copper substrate. The Raman enhancement of Gr/Au/RP PMMA is studied in terms of both electromagnetic enhancement and chemical enhancement. The field strength enhancement of the obtained Gr/Au/RP PMMA substrate is more than 4.9 times greater than that of the Gr/Au/flat PMMA substrate, established using a COMSOL simulation. By actively modulating the machining parameters on a Cu-Gr surface, the number of Gr layers, as well as the Gr/Au/RP PMMA topography, can be controlled, which can effectively influence the performance of the SERS substrate. Moreover, compared with other SERS substrates, including Gr/Au/RP PMMA, Gr/Au/flat PMMA, Au/Gr/RP Cu, Gr/RP PMMA, and Au/RP PMMA, the Raman intensities of R6G were strongest on the Gr/Au/RP PMMA. In addition, the minimum detectable concentrations of paraquat (PQ) and 2,4-d used in situ detection were 10−8 M and 10−6 M, respectively, after being covered with the Gr/Au/RP PMMA flexible substrate. To test its practical applicability with actual fruit surfaces, the Gr/Au/RP PMMA flexible substrate was used for the in situ SERS detection of PQ on apples. Clear Raman peaks of 10−7 M PQ were detected on the apple surface.

PfAgo-Based Zika Virus Detection.

As a mosquito-borne flavivirus, Zika virus (ZIKV) has been identified as a global health threat. The virus has been linked to severe congenital disabilities, including microcephaly and other congenital malformations, resulting in fatal intrauterine death. Therefore, developing sensitive and specific methods for the early detection and accurate diagnosis of the ZIKV is essential for controlling its spread and mitigating its impact on public health. Herein, we set up a novel nucleic acid detection system based on Pyrococcus furiosus Argonaute (PfAgo)-mediated nucleic acid detection, targeting the non-structural protein 5 (NS5) region of the ZIKV genome (abbreviated ZIKV-PAND). Without preamplification with the polymerase chain reaction (PCR), the minimum detection concentration (MDC) of ZIKV-PAND was about 10 nM. When introducing an amplification step, the MDC can be dramatically decreased to the aM level (8.3 aM), which is comparable to qRT-PCR assay (1.6 aM). In addition, the diagnostic findings from the analysis of simulated clinical samples or Zika virus samples using ZIKV-PAND show a complete agreement of 100% with qRT-PCR assays. This correlation can aid in the implementation of molecular testing for clinical diagnoses and the investigation of ZIKV infection on an epidemiological scale.

Zinc Sensing Advancements for Prostate Cancer Detection: Insights from Zincon-MoS2 Electrochemical Characterization

Epidemiological research has illuminated the pivotal role of zinc (Zn) in prostate cancer detection. Among its noteworthy attributes, a healthy prostate is characterized by a higher zinc content, while in a malignant prostate, there is a marked decrease in zinc aggregation. Electrochemical sensing techniques have proven to be valuable in studying zinc behaviour; In this study, we examined the electrochemical characteristics of a glassy carbon electrode that underwent modification with Zincon-MoS2. Our primary objective was to achieve a sensitive and selective approach for detecting zinc in the context of prostate cancer. The synthesis of the Zincon-MoS2 composite was executed through hydrothermal, and subsequent chemical functionalization with zinc was employed to augment its affinity for zinc ions. Conducting cyclic voltammetry measurements, we sought to gain deeper electrochemical insights when exposed to zinc ions. The Zincon-MoS2-modified electrode that we created exhibited exceptional electrochemical capabilities for precisely detecting zinc. We studied the behaviour of MoS2 sheet on microlevel and rest of the studies are done on nano dimensions. We reported 0.912 μM Limit of detection which is quite low then the limit of the zinc concentration in healthy prostate i.e 12 μM. Additionally, the limit of quantification was calculated to be 3.04 μM, indicating the minimum detectable concentration of zinc. The sensitivity of the sensor was found to be 0.086 μAmp/nM-cm2, emphasizing its ability to detect zinc accurately. Furthermore, the effect of pH variations in the electrolyte on the maximum current levels was studied, providing valuable information on the response of the sensor under different physiological conditions. The electrochemical insights obtained through this investigation contribute to a deeper understanding of zinc behaviour in prostate cancer.

Gold nanoparticles spectral CT imaging and limit of detectability in a new materials contrast-detail phantom

This study involves the synthesis, characterization, and spectral photon counting CT (SPCCT) imaging of gold nanoparticles tailored for enhancing the contrast of small cancer lesions. We used the modified Turkevich method to produce thiol-capped gold nanoparticles (AuNPs) at different concentrations (20, 15, 10, 5, 2.5, 1.25, 0.6 mg/ml). We thoroughly characterized the AuNPs using Transmission Electron Microscopy (TEM), X-ray diffraction spectroscopy (XRD), Dynamic Light Scattering (DLS), and UV–visible absorption spectroscopy. To assess the AuNPs contrast enhancing performance, we designed and built a new material contrast detail phantom for CT imaging and determined the minimum detectable concentrations of AuNPs in simulated lesions of small diameters (1, 2, 3, and 5 mm). The synthesized AuNPs are spherical with an average size of approximately 20 ± 4 nm, with maximum UV absorption occurring at 527 nm wavelength, and exhibit a face-centered cubic structure of gold according to XRD analysis. The synthesized gold nanoparticles demonstrated high contrast in SPCCT, suggesting their potential as contrast agents for imaging cancer tissues. The AuNPs image contrast was directly proportional to the AuNPs concentration. We are the first to determine that the lowest visually distinguishable contrast was achieved at a gold concentration of 5 mg/ml for a 2 mm simulated lesion. For 1 mm size lesion the smallest visible concentration was 10 mg/ml. This newly developed phantom can be used for determining the minimal concentration required for various high-Z nanoparticles to produce detectable contrast in X-ray imaging for small-size simulated lesions.

Silver nanostars arrayed on GO/MWCNT composite membranes for enrichment and SERS detection of polystyrene nanoplastics in water

Nanoplastic water contamination has become a critical environmental issue, highlighting the need for rapid and sensitive detection of nanoplastics. In this study, we aimed to prepare a graphene oxide (GO)/multiwalled carbon nanotube (MWCNT)–silver nanostar (AgNS) multifunctional membrane using a simple vacuum filtration method for the enrichment and surface-enhanced Raman spectroscopy (SERS) detection of polystyrene (PS) nanoplastics in water. AgNSs, selected for the size and shape of nanoplastics, have numerous exposed Raman hotspots on their surface, which exert a strong electromagnetic enhancement effect. AgNSs were filter-arrayed on GO/MWCNT composite membranes with excellent enrichment ability and chemical enhancement effects, resulting in the high sensitivity of GO/MWCNT–AgNS membranes. When the water samples flowed through the portable filtration device with GO/MWCNT–AgNS membranes, PS nanoplastics could be effectively enriched, and the retention rate for 50 nm PS nanoplastics was 97.1 %. Utilizing the strong SERS effect of the GO/MWCNT–AgNS membrane, we successfully detected PS nanoparticles with particle size in the range of 50–1000 nm and a minimum detection concentration of 5 × 10−5 mg/mL. In addition, we detected 50, 100, and 200 nm PS nanoplastics at concentrations as low as 5 × 10−5 mg/mL in real water samples using spiking experiments. These results indicate that the GO/MWCNT–AgNS membranes paired with a portable filtration device and Raman spectrometer can effectively enrich and rapidly detect PS nanoplastics in water, which has great potential for on-site sensitive water quality safety evaluation.

A Multilayered GaAs IPD Resonator with Five Airbridges for Sensor System Application.

This work proposes a microwave resonator built from gallium arsenide using integrated passive device (IPD) technology. It consists of a three-layered interlaced spiral structure with airbridges and inner interdigital structures. For integrated systems, IPD technology demonstrated outstanding performance, robustness, and a tiny size at a low cost. The airbridges were made more compact, with overall dimensions of 1590 × 800 µm2 (0.038 × 0.019 λg2). The designed microwave resonator operated at 1.99 GHz with a return loss of 39 dB, an insertion loss of 0.07 dB, and a quality factor of 1.15. Additionally, an experiment was conducted on the properties of the airbridge and how they affected resistance, inductance, and S-parameters in the construction of the resonator. To investigate the impact of airbridges on the structure, E- and H-field distributions of the resonator were simulated. Furthermore, its use in sensing applications was explored. Various concentrations of glucose solutions were used in the experiment. The proposed device featured a minimum detectable concentration of 0.2 mg/mL; high sensitivity, namely, 14.58 MHz/mg·mL-1, with a linear response; and a short response time. Thus, this work proposes a structure that exhibits potential in integrated systems and real-time sensing systems with high sensitivity.

Recyclable Fe3O4@SiO2@PEI-DTC@Au-Ag nanocomposites as a SERS platform for sensitive detection of thiram on fruit surfaces

Equipped with surface-enhanced Raman scattering (SERS) effect and magnetic manipulation capacity, a new paradigm of recyclable SERS substrates based on Fe3O4 nanoparticles (NPs) @SiO2@PEI-DTC adhesive layer @Au-Ag alloy quantum dots (QDs) were successfully prepared via engineering hydrothermal and seed deposition techniques. The SERS performance and uniformity of those substrates with different gold-silver (Au-Ag) weight ratios were evaluated by 4-aminothiophenol (4-ATP) molecules, revealing that the relative standard deviations (RSDs) of all substrates were less than 12 %, with the optimal SERS substrate achieving an enhancement factor (EF) of up to 1.39 × 105. This phenomenon can be attributed to the magnetic core and plasmonic resonance properties of Au-Ag alloy QDs, which result in abundant interparticle hotspots in the Fe3O4@SiO2@PEI-DTC@Au-Ag (FSPAA) nanocomposites. Furthermore, the optimal FSPAA nanocomposite was employed as a SERS substrate for rapid non-destructive detection of thiram on fruit surfaces. The SERS signal intensity exhibited a robust manifesting a linear association with thiram concentration within the span of 1 × 10−4 to 1 × 10−9 M, and the minimal detectable concentration was 1.04 × 10−10 M. The FSPAA core–shell nanocomposites exhibit high reusability and reliability and hold great promise for the practical applications in on-site assessment of food/environmental safety, as well as in spectroscopic identification of molecules adsorbed onto fruit surfaces.

The method of determination for 2, 3-Butanedione in the air of workplace by high performance liquid chromatography with derivatization

Objective: To establish a method for the determination of 2, 3-Butanedione (BUT) in the air of workplace, which including the process of collection by absorption in phosphoric acid aqueous solution and the process of analysis and detection by high performance liquid chromatography with derivatization. Methods: In October 2022, a porous glass plate absorption tube containing 10 ml of 0.01% phosphoric acid solution was used to collect BUT in the air of the workplace at a flow rate of 0.2 L/min. The absorption solution was derived by 2, 4-dinitrophenylhydrazine for 75 min and separated on a SB-C18 column (250 mm×4.6 mm, 5 μm) . At the column temperature of 30 ℃, the mixture of acetonitrile-water (V∶V, 1∶1) was eluted at the flow rate of 1.0 ml/min. It was detected by UV detector (λ=365 nm) , qualitatived by retention time and quantitatived by external standard. Results: It showed that BUT in phosphoric acid aqueous solution could be stored for at least 7 d at 4 ℃. There was a linear relationship within the determination range of 0.05-6.00 μg/ml, the linear regression equation was y=89.610x+0.133, r=0.9999. The sampling absorption efficiencies were 98.33%-100.00%, the detection limit of the method was 0.005 μg/ml, the minimum detection concentration was 0.016 mg/m(3) (based on V(0)=3.0 L) . The recovery rates were 95.96%-102.44%, the intra batch precision were 4.36%-7.78%, and the inter batch precision were 4.96%-6.06%. Conclusion: The method has the advantages of simple operation, high sensitivity and good accuracy. It can prevent the loss and degradation of BUT. It can be used for the determination of BUT in the air of workplace.

Establishment and Application of a Quadruplex Real-Time Reverse-Transcription Polymerase Chain Reaction Assay for Differentiation of Porcine Reproductive and Respiratory Syndrome Virus, Porcine Circovirus Type 2, Porcine Circovirus Type 3, and Streptococcus suis.

Respiratory illnesses present a significant threat to porcine health, with co-infections involving Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), Streptococcus suis (SS), Porcine Circovirus Type 2 (PCV2), and Porcine Circovirus Type 3 (PCV3) acting as the primary causative agents. As a result, the precise diagnosis of PRRSV, PCV2, PCV3 and SS is of paramount importance in the prevention and control of respiratory diseases in swine. Therefore, we conducted a molecular bioinformatical analysis to concurrently detect and differentiate PRRSV, PCV2, PCV3 and SS. We selected the ORF6 gene of PRRSV, the ORF2 gene of PCV2 and PCV3, and the glutamate dehydrogenase (GDH) gene of SS as targets. Specific primers and probes were designed for each pathogen, and following meticulous optimization of reaction conditions, we established a multiple TaqMan fluorescence quantitative PCR detection method. Subsequently, we subjected this method to a comprehensive assessment, evaluating its specificity, sensitivity, and repeatability. The research results demonstrated that the established multiple TaqMan fluorescence quantitative PCR detection method displays displayed exemplary specificity, with no instances of cross-reactivity with other pathogens. The method's minimum detection concentrations for PRRSV, PCV2, PCV3, and SS were 2.80 × 101 copies/µL, 1.96 × 102 copies/µL, 2.30 × 102 copies/µL, and 1.75 × 103 copies/µL, respectively. When applied to the analysis of 30 clinical samples, the results closely mirrored those obtained through Chinese standard uniplex real-time qPCR detection method for PRRSV, as well as the general PCR methods for SS, PCV2, and PCV3. This study underscores the robust specificity, high sensitivity, and consistent stability of the multiple TaqMan fluorescence quantitative PCR detection method that we have developed. It is ideally suited to the clinical monitoring of PRRSV, PCV2, PCV3, and SS, and it carries significant importance in ongoing efforts to prevent and manage respiratory diseases in porcine populations.

Biotin as a structural component in the detection of small model antigens in BLA-S-ELISA

An interesting biotin-linked-antigen-Sandwich-ELISA was developed (BLA-S-ELISA), which based on the captured Trinitrophenol-Biotin (TNP-Biotin) molecule between the immobilised monovalent antibody and enzyme-conjugated streptavidin. Monoclonal anti-Trinitrotoluene single chain fragment antibody (anti-TNT-scFv) was cloned and expressed in E. coli cells, and then used as an immobilised component in an assay. Thereafter, the previously synthesised TNP-Biotin was added as antigen followed by the addition of streptavidin-horseradish peroxidase (streptavidin-HRP) conjugate which led finally to the formation of a three-component system (antibody/TNP-Biotin/streptavidin-HRP). The assay was performed with a range of different dilutions of TNP-Biotin to establish its minimal detectable concentration. The detection limit of TNP-Biotin was 4 ngmL−1 (i.e. 200 pg or 0.42 pmol antigen calculated on the basis of 50 μL sample or 8.4 nM expressed in concentration units). According to our best knowledge, this is the very first time for any model antigen to be detected with such a form of biotin-streptavidin sandwich-assay.

MCNP simulation and experimental study in situ low-grade copper analysis based on PGNAA

A prompt gamma neutron activation analysis (PGNAA) facility utilizing 252Cf source has been developed for in situ analysis of copper samples. Monte Carlo simulation is employed to determine optimal sizes for neutron moderator, gamma-ray shielding material, and thermal neutron absorber. Subsequently, based on the parameters optimized by MCNP, the PGNAA facility was constructed. Five sets of experimental samples containing low-grade copper concentration of 0 %, 0.5 %, 1 %, 1.5 % and 2 % are measured with the PGNAA facility. The results show that the minimum detectable concentration of copper is 0.218 %. The maximum relative deviation of copper is 8.53 %.

Gold Nanoparticle-Decorated Polymer Particles for High-Optical-Density Immunoassay Probes.

To realize a highly sensitive immunoassay, high-optical-density probes conjugated with antibodies for target antigens are needed to increase the detectability of antigen-antibody complex formation. In this work, gold nanoparticle (NP)-decorated polymer (GNDP) particles were successfully prepared by mixing positively charged polymer particles and negatively charged Au NPs. GNDP particles decorated with NPs of 20 nm in size had higher optical density than the original Au NPs and GNDPs decorated with smaller Au NPs. Using GNDP particles as a probe, a highly sensitive immunoassay for influenza H1N1 hemagglutinin was realized with a minimum detectable concentration of 32.5 pg/mL. These results indicate that GNDP particles have high potential as an immunoassay probe that can be used in practical immunoassay systems for detecting a wide variety of antigens.