On-site rapid detection of multiple pesticide residues in tea leaves by lateral flow immunoassay

The application of pesticides (mostly insecticides and fungicides) during the tea-planting process will undoubtedly increase the dietary risk associated with drinking tea. Thus, it is necessary to ascertain whether pesticide residues in tea products exceed the maximum residue limits. However, the complex matrices present in tea samples comprise a major challenge in the analytical detection of pesticide residues. In this study, nine types of lateral flow immunochromatographic strips (LFICSs) were developed to detect the pesticides of interest (fenpropathrin, chlorpyrifos, imidacloprid, thiamethoxam, acetamiprid, carbendazim, chlorothalonil, pyraclostrobin, and iprodione). To reduce the interference of tea substrates on the assay sensitivity, the pretreatment conditions for tea samples, including the extraction solvent, extraction time, and purification agent, were optimized for the simultaneous detection of these pesticides. The entire testing procedure (including pretreatment and detection) could be completed within 30 min. The detected results of authentic tea samples were confirmed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), which suggest that the LFICS coupled with sample rapid pretreatment can be used for on-site rapid screening of the target pesticide in tea products prior to their market release.

Rapid Detection of Somatic Cell Count Based on Hybrid Variable Selection Method

Somatic cell count detection is the daily work of dairy farms to monitor the health of cows.The feasibility of applying near-infrared spectroscopy to somatic cell count detection was researched in this paper.Milk samples with different somatic cell counts were collected and preprocessing methods were studied.Variable selection algorithm based on hybrid strategy and modelling method based on ensemble learning were explored for somatic cell count detection.Detection model was used to diagnose subclinical mastitis and the results showed that near-infrared spectroscopy could be a tool to realize rapid detection of somatic cell count in milk.

A Rapid and Simple Method for the Detection of Rice Dwarf Virus by Aqueous Extract

Rice dwarf disease caused by rice dwarf virus （RDV） is one of the major rice virus diseases in China,which widely distributes in the rice area of China.A simple and rapid method for detection of RDV in rice plants and Nephotettix cincticeps was investigated in this study,and the whole detection only lasted for 20 min.After diseased leaves of rice （10 mg） and leaves of Nephotettix cincticeps （10 mg） both infected by RDV were ground by sterile water （100 μl）,the supernatant was analyzed by 1% agarose gel electrophoresis to steadily detect five specific electrophoretic bands with 1 000 bp to 5 000 bp.However,there was no electrophoretic band in the healthy rice leaves and aqueous extract of non-viruliferous N.cincticeps.Therefore,this method was more rapid and simple to detect RDV in rice plants and Nephotettix cincticeps,which avoided expensive reagents and tedious steps of conventional serological testing and molecular detection （RT-PCR and Western-blot）.

The Application of Reverse Transcription-loop-mediated Isothermal Amplification for the Rapid Detection of Maize Chlorotic Dwarf Virus

Maize chlorotic dwarf virus （MCDV） is a quarantine pest as approved by Chinese government. A rapid, sensitive and specific MCDV detection method using reverse transcription-loop-mediated isothermal amplification （RT-LAMP） was estab- lished in this study. Based on the sequence of MCDV coat protein coding gene, specific primers were designed and similar sensitivities were observed between RT- LAMP and RT-PCR, except that RT-LAMP was quicker, and the reaction could be finished within 1 h. In addition, the presence or absence of the fluorescent display in daylight allows naked easy detection of the amplification of MCDV genomic RNA using calcein. The RT-LAMP assay was applied successfully to detect MCDV in maize seeds, and the result by the addition of calcein was consistent with the result detected by the real time turbidimeter.

A Novel RT-LAMP Assay for Rapid and Simple Detection of Classical Swine Fever Virus

A simple and rapid assay for the detection of Classical swine fever virus(CSFV)was established using reverse transcription loop-mediated isothermal amplification(RT-LAMP).This study describes the amplification of the genomic RNA of CSFV under isothermal conditions(63℃)within one hour,using a set of six primers(two outer primers,two inner primers and two loop primers).This RT-LAMP assay showed 100-fold higher sensitivity than the standard RT-PCR method and identified eighteen additional positive cases that were negative when tested by RT-PCR.This RT-LAMP was able to detect all the 13 strains of CSFV but not the BVDV.PRRSV.SIV. PRV-PCV,thus showed a good specificity.Products amplified by RT-LAMP can be visualized by agarose gel electrophoresis and in addition,either as a white precipitate at the bottom of the tube after a pulse spin or as a color change when dyed with SYBR Green I which are visible to the naked eye.Because RT-LAMP is low-cost and produces rapid results,it has the potential to be an excellent tool for CSFV surveillance in the field,especially in developing countries.

Deterioration mechanism and rapid detection of performances of an existing subgrade in southern China

To relieve the increasing traffic load, many early built highways need to be widened or reconstructed. The rapid performance detection to existing subgrades is important to their reasonable evaluation and maximized utilization. Based on five kinds of soils taken from an existing highway in southern China, three commonly detecting methods were used to determine their moisture contents, compaction degrees and resilient moduli. The results showed that the measured moisture contents were greater than the design value, and the compaction degrees decreased sharply compared to the original ones. The moisture and heat exchange produced a decrease in the resilient modulus of plate loading test(PLT) from the standard 60 MPa down to 40 MPa. Afterwards, the portable falling weight deflectometer(PFWD) and dynamic cone penetrometer(DCP) were used to evaluate the subgrade performances. The measured PFWD moduli and the DCP penetration rates were correlated with the resilient moduli of PLT, deflections of the Beckman beam test, compaction degrees and moisture contents. The correlation analysis indicates that both of two methods are suitable in rapid detecting subgrade performances, but PFWD method is more recommended for it has higher accuracy and efficiency.

Rapid detection of Pseudomonas aeruginosa by cross priming amplification

Pseudomonas aeruginosa(PA)is an opportunistic pathogen of humans and animals and a common source of nosocomial infections especially of the respiratory tract.Pseudomonas aeruginosa is also a major bacterial disease of poultry and in particular,eggs and newly hatched chicks.In this study,we developed a simple,accurate and rapid molecular detection method using cross priming amplification(CPA)with a nucleic acid test strip to detect P.aeruginosa.The assay efficiently amplified the target gene within 45 min at 62℃only using a simple water bath.The detection limit of the method was 1.18x 102 copiesμL^-1 for plasmid DNA and 4.4 CFU mL^-1 for bacteria in pure culture,and was 100 times more sensitive than conventional PCR.We screened 83 clinical samples from yellow-feather broiler breeder chickens and hospitalized/treated dogs and cats using CPA,PCR and traditional culture methods.The positive sample ratios were 15.3%(13/83)by CPA,13.3%(11/83)by PCR and 12.1%(10/83)by the culture method.The established CPA method has significant advantages for detecting P.aeruginosa.The method is easy to use and possesses high specificity and sensitivity without the requirements of complicated experimental equipment.The PA-CPA assay is especially fit for outdoor and primary medical units and is an ideal system for the rapid detection and monitoring of P.aeruginosa.

Recent advances in immunoassays and biosensors for mycotoxins detection in feedstuffs and foods

Mycotoxins are secondary metabolites produced by fungus.Many mycotoxin species are highly toxic and are frequently found in cereals and feedstuffs.So,powerful detection methods are vital and effective ways to prevent feed contamination.Traditional detection methods can no longer meet the needs of massive,real-time,simple,and fast mycotoxin monitoring.Rapid detection methods based on advanced material and sensor technology are the future trend.In this review,we highlight recent progress of mycotoxin rapid detection strategies in feedstuffs and foods,especially for simultaneous multiplex mycotoxin determination.Immunoassays,biosensors,and the prominent roles of nanomaterials are introduced.The principles of different types of recognition and signal transduction are explained,and the merits and pitfalls of these methods are compared.Furthermore,limitations and challenges of existing rapid sensing strategies and perspectives of future research are discussed.

Enzyme Inhibition Rate Method for Rapid Detection of Organophosphorus and Carbamate Pesticides in Cowpea

[Objectives ] The paper was to explore enzyme inhibition rate method for rapid detection of organophosphorus and carbamate pesticides in cowpea. [ Methods ] Acetylcholinesterase （ACHE） was added to cowpea extract, to determine the inhibition rate of extract against enzyme. The influences of different sampiing methods and sampling parts on detection results were compared. [ Results] The positive rate of standard sampling was 18.18% higher than that of non-stand- ard sampling, and the positive rate of samples collected from cowpea tail was 16.67% higher than that collected from other parts. [ Condmions] Enzyme inhibi- tion rate method is suitable for rapid detection of organophosphorus and carbamate pesticides in cowpea.

In vitro Selection of DNA Aptamers and Fluorescence-Based Recognition for Rapid Detection Listeria monocytogenes

Aptamers are specific nucleic acid sequences that can bind to a wide range of nucleic acid and non-nucleic acid targets with high affinity and specificity. Nucleic acid aptamers are selected in vitro from single stranded DNA or RNA ligands containing random sequences of up to a few hundred nucleotides. Systematic evolution of ligands by exponential enrichment （SELEX） was used to select and PCR amplify DNA sequences （aptamers） capable of binding to and detecting Listeria monocytogenes, one of the major food-borne pathogens. A simplified affinity separation approach was employed, in which L. monocytogenes in exponential （log） phase of growth was used as the separation target. A fluorescently-labeled aptamer assay scheme was devised for detecting L. monoeytogenes. This report described a novel approach to the detection of L. monocytogenes using DNA aptamers. Aptamers were developed by nine rounds of SELEX. A high affinity aptamer was successfully selected from the initial random DNA pool, and its secondary structure was also investigated. One of aptamers named e01 with the highest affinity was further tested in aptamer-peroxidase and aptamer-fluorescence staining protocols. This study has proved the principle that the whole-cell SELEX could be a promising technique to design aptamer-based molecular probes for dectection of pathogenic microorganisms without tedious isolation and purification of complex markers or targets.

A Device for Rapid Detection of Dithiocarbamate Pesticide Residues in Fruits

Based on the chemical properties of dithiocarbamate pesticides,a device for rapid detection was developed in the paper,and the experimental conditions were optimized. Dithiocarbamate residues in fruits were successfully detected using molecular absorption spectro-photometry,and the recovery rate was over 80%.The rapid detection method was simple to operate with low cost,and was conducive to application in basic level and enterprise laboratories.

Study on PCR rapid molecular detection technique of Meloidogyne vitis

Meloidogyne vitis is a new root-knot nematode parasitic on grape root in Yunnan Province,China.In order to establish a rapid,reliable and specific molecular detection method for M.vitis,the species-specific primers were designed with rDNA-ITS(ribosomal DNA internal transcribed spacer)gene fragment as the target.The reaction system was optimized and the reliability,specificity and sensitivity of primer were testified,therefore,a rapid PCR detection method for M.vitis was established.The result showed that the optimal annealing temperature of the primers was 53℃,which was suitable for the detection of different life stages of M.vitis.Specificity test showed that the specific fragment size of 174 bp was obtained from M.vitis,but other five non-target nematodes did not have any amplification bands,thus effectively distinguish M.vitis and the other five species,and could specifically detect the M.vitis from mixed populations.Sensitivity test showed that this PCR technique could detect the DNA of a single second-stage juvenile(J_(2))and 10^(-4)female.Futhermore,this PCR technique could be used to detect directly M.vitis from soil samples.The rapid,sensitive and specific PCR molecular detection technique could be used for the direct identification of a single J_(2)of M.vitis and the detection of M.vitis in mixed nematode populations and the detection of two J_(2)s or one male in 0.5 g soil samples,which will provide technical support for the investigation of the occurrence and damage of M.vitis and the formulation of efficient green co ntrol strategies.

Development of a new field-deployable RT-qPCR workflow for COVID-19 detection

Background:Outbreaks of coronavirus disease 2019(COVID-19)have been recorded in different countries across the globe.The virus is highly contagious,hence early detection,isolation,and quarantine of infected patients will play an important role in containing the viral spread.Diagnosis in a mobile lab can aid to find infected patients in time.Methods:Here,we develop a field-deployable diagnostic workflow that can reliably detect COVID-19.Instruments used in this workflow can easily fit in a mobile cabin hospital and also be installed in the community.Different steps from sample inactivation to detection were optimized to find the fastest steps and portable instruments in the detection of COVID-19.Each step was compared to that of the normal laboratory diagnosis setup.Results:From the results,our proposed workflow(80 min)was two times faster compared to that of the normal laboratory workflow(183 min)and a maximum of 32 samples could be detected at each run.Additionally,we showed that using 1%Rewocid WK-30 could inactivate the novel coronavirus directly without affecting the overall detection results.Comparison of our workflow using an in-house assay to that of a commercially acquired assay produced highly reliable results.From the 250 hospital samples tested,there was a high concordance 247/250(98.8%)between the two assays.The in-house assay sensitivity and specificity were 116/116(100%)and 131/134(97.8%)compared to that of the commercial assay.Conclusion:Based on these results,we believe that our workflow is fast,reliable,adaptable and most importantly,field-deployable.

Recent Advances in the Rapid Detection and Performance Evaluation Methods of Detergent Additives for Gasoline

Although detergent additives for gasoline have been widely commercialized,their formulas are often kept confidential and there is still no standardized method for quickly detecting the main active ingredients and evaluating their effectiveness,which makes their regulation difficult.An overview of the current state of the development and application of detergent additives for gasoline in China and other regions,as well as a review of the rapid detection and performance evaluation methods available for analyzing detergent additives are given herein.The review focuses on the convenience,cost,efficiency,and feasibility of on-site detection and the evaluation of various methods,and also looks into future research directions,such as detecting and evaluating detergent additives in ethanol gasoline and with advanced engine technologies.

Development of a Microfluidics-Based Quantitative Real-Time PCR to Rapidly Identify Photobacterium damselae subsp.damselae with Different Pathogenicity by Detecting the Presence of mcp or dly Gene

As a marine bacterial pathogen, Photobacterium damselae subsp. damselae(PDD) is distributed in seawater worldwide. It can infect different animals as well as humans, even cause deaths. The highly conserved regions of PDD mcp gene on chromosome and dly gene on plasmid were selected as the target fragments to design the specific primers. Recombinant plasmid standard was prepared based on the primers. With GENECHECKER UF-150 qRT-PCR instrument as the platform, a fluorescence-based quantitative real-time PCR(qRT-PCR) method was established for the detection of PDD. This method can specifically detect PDD and distinguish the highly virulent strains. Additionally, the test results can be qualitatively judged by visualization, while the quantitative detection can be achieved through the standard curve calculation. The minimum limit of detection was 1.0×101 copies μL-1, and the detection time was less than 20 min. In summary, this new method has outstanding advantages, such as strong specificity, high sensitivity, and low site requirements. It is a rapid on-site detection technology for highly virulent PDD strains.

Filtration assisted pretreatment for rapid enrichment and accurate detection of Salmonella in vegetables

Rapid detection of target foodborne pathogens plays more and more significant roles in food safety,which requires the efficiency,sensitivity,and accuracy.In this research,we proposed a new st rategy of isothermal-molecular-amplification integrated with lateral-flow-strip for rapid detection of Salmonella without traditional enrichment-culture.Th e designed syringe-assisted-filtration can contribute to simultaneous collection and concentration of target bacterium from vegetable samples in just 3 min,resolving the drawbacks of traditional random sampling protocols.After simple and convenient ultrasonication,samples can be directly amplified at 39℃ in 25 min and the amplicons are qualitatively and quantitatively analyzed with the designed lateral-flow-strip in 5 min.Finally,satisfied results have been achieved within 40 min,which greatly improve the efficiency while the accuracy is also guaranteed.Furthermore,all detection steps can be completed under instrument-free conditions.This method will hold great promise for target pathogen detection in the resource-limited district,or for emergency on-site identification.

Dengue virus infection:A review of advances in the emerging rapid detection methods

Dengue virus infections are increasing worldwide generally and in Asia,Central and South America and Africa,particularly.It poses a serious threat to the children population.The rapid and accurate diagnostic systems are essentially required due to lack of effective vaccine against dengue virus and the progressive spread of the dengue virus infection.The recent progress in developing micro-and nano-fabrication techniques has led to low cost and scale down the biomedical point-of-care devices.Starting from the conventional and modern available methods for the diagnosis of dengue infection,this review examines several emerging rapid and point-of-care diagnostic devices that hold significant potential for the progress in smart diagnosis tools.The given review revealed that an effective vaccine is required urgently against all the dengue virus serotypes.However,the rapid detection methods of dengue virus help in early treatment and significantly reduce the dengue virus outbreak.

Rapid Detection of Fat Content in Chenopodium quinoa Willd by Near Infrared Spectroscopy

This study was conducted to find a method for rapid determination of fat content in complete quinoa （ Chenopodium quinoa Willd） seeds. The near infrared spectra of 100 quinoa samples were collected, and a mathematic model was built using the near infrared spectra, so as to perform prediction. The results showed that within the wavelength range of 1 0 000-4 000 cm ^-1 , the quantification model of fat content built by first derivative ＋vector normalization spectral pre-processing had better calibration and prediction effects, and showed a determination coefficient of cross validation （ r cv^ 2 ） of 0.939 3 and a determination coefficient of validation （ rval^2 ） of 0.923 5. The near infrared spectral model of fat could be used for rapid detection of fat contents in quinoa.

Preparation of a Salmonella LAMP Detection Kit

[Objectives] This study was conducted to establish a method for rapid detection of Salmonella at the grassroots level, and a corresponding product was developed. [Methods] By analyzing the invA gene of Salmonella, two pairs of efficient, rapid and specific amplification primers were designed and screened for the six conserved domains of the gene, and the LAMP detection kit for Salmonella based on this method was produced. [Results] The method is simple, sensitive, rapid and specific. The minimum detection concentration is 10~2-10~3 CFU/ml. [Conclusions] It can be used in the self-inspection of food production enterprises and the on-site sampling inspection and rapid detection of large quantities of samples by grassroots food safety inspection and supervision departments.

Establishment of Recombinase Polymerase Amplification for Rapid Detection of Spring Viremia of Carp Virus(SVCV)

[Objective]The paper was to develop a rapid method for the detection of spring Viremia of carp virus(SVCV).[Method]The specific primers were designed by targeting the G gene of SVCV.The recombinase polymerase amplification(RPA)assay for detecting SVCV was estab-lished by optimizing the reaction conditions.The optimal amplification temperature of RPA assay was 30℃,and the test could be finished within 20 min.[Result]The method was specific with no cross-reaction with other common fish infectious viruses.Sensitivity test showed that the lowest detection limit of the method was 89.2 copies/μL,higher than that of traditional RT-PCR.Moreover,a total of 80 clinical samples were detected by RPA and RT-PCR,respectively.The weak positive samples tested by RT-PCR could be detectable with RPA,indicating that RPA assay could be used in clinical detection.[Conclusion]The method established is rapid,simple,specific and sensitive for testing SVCV,and it will be widely used in grassroots laboratory and on-site inspection.