Molecular simulation-guided aptasensor design of robust and sensitive lateral flow strip for cadmium ion detection.

Lateral flow fluorescence strip (LFFS) aptasensor have been widely used for on-site target detection. However, they are limited by low sensitivity and strong background signals owing to the inappropriate design of molecule probes. Herein, we employed molecular simulations to improve the sensitivity of LFFS by the optimization of the DNA probe length and sequence, which is a critical parameter for the competitive approach of the aptasensor. Simulation results revealed that a probe with 30 nt can maximize the hybridization yield of aptamer to reduce the background signal. More importantly, the simulation results highlighted the Cd2+ concentration-dependent conformational changes in the aptamer. It is essential to block its hybridization with a probe, and consequently, yield sensitive and target concentration-dependent fluorescence signal. Considering these results, we developed a sensitive aptamer-based fluorescent lateral flow strip for rapid Cd2+ detection. The fluorescence intensity of this strip exhibited an excellent linear relationship with the Cd2+ concentration ranging from 63 nM to 1000 nM (R2 = 0.9724). The limit of detection was determined to be 30 nM (S/N = 3). This method was also applied for the detection of Cd2+ in river water samples in the range from 92.9 ± 1.0% to 108.6 ± 1.4%. Moreover, the detected concentration in water samples is below the harmful levels (267 nM) recommended by WHO standards in drinking water. The use of molecular simulations is a significant addition to cost and resource-effective aptasensor development protocol, and it can be readily expanded to design aptasensors for other targets.

Rapid Russula senecis identification assays using loop-mediated isothermal amplification based on real-time fluorescence and visualization.

Russula senecis, a common poisonous mushroom, is widely distributed in China. Mushroom poisoning is becoming a major threat to human health and its rate is increasing worldwide. For the first time, we developed a set of loop-mediated isothermal amplification (LAMP) assays based on a real-time fluorescence and a visualization method to detect R. senecis, and the visual LAMP reaction system was optimized to further shorten the reaction time. Both real-time LAMP and visual LAMP could detect as low as 3.2 pg of genomic DNA. In addition, fried and digested mushrooms were used to validate the proposed LAMP method, and mushroom mixtures with as low as 1% of the target species could be successfully detected, indicating that the LAMP assays established in this study had good applicability and could be used for clinical sample detection and forensic identification. Furthermore, the LAMP assays were proven to be comparable to the real-time PCR method. KEY POINTS: • A set of loop-mediated isothermal amplification (LAMP) assays based on real-time fluorescence and visualization to detect Russula senecis was developed. • Both real-time LAMP and visual LAMP can be used to detect genomic DNA at concentrations as low as 3.2 pg. • By simulating mushroom processing and digestion in gastric juice, LAMP assays were proved to have good applicability and could be used for clinical diagnosis and forensic analysis.

A strip of lateral flow gene assay using gold nanoparticles for point-of-care diagnosis of African swine fever virus in limited environment.

Recombinase polymerase amplification (RPA) was combined with lateral flow to develop a gold nanoparticles test strip for point-of-care diagnosis of African swine fever virus (ASFV), which is called lateral flow gene assay (LFGA). Common diagnostic techniques, including polymerase chain reaction (PCR) and immunochromatography, are time-consuming and labor-intensive, and generally require costly instruments. For improvement, this assay used tailed primers to produce DNA duplexes with a single-stranded tail at one end which can hybridize with a gold nanoparticle (AuNP)-labeled oligonucleotide detection probe. And then, biotin attached to the other end of the product bound to streptavidin, which previously fixed to the test line. Therefore, there would form a sandwich structure, and gold nanoparticles labeled on the detection probe would show a red band on the test line of strip. With the low reaction temperature (37~42 °C) and short reaction time (30 min), LFGA can specifically identify ASFV in blood samples infected with ASFV and classical swine fever virus (CSFV), and the LOD was 102 copies/µL, which was comparable to that of agarose gel electrophoresis. In addition, blood samples infected with ASFV and CSFV were tested, and it was found that the LFGA can specifically identify ASFV DNA. In conclusion, LFGA achieves visual observation of the product after rapid RPA amplification and does not require any expensive instruments during the entire process, which is very helpful for early diagnosis of ASFV. Combined recombinase polymerase amplification (RPA) with lateral flow, we developed a gold nanoparticles test strip for point-of-care diagnosis of African swine fever virus. The upstream primers of RPA were modified with biotin, and the downstream primers were modified with a C3 spacer and an oligonucleotide tail that can be hybridized to a gold nanoparticle-labeled oligonucleotide detection probe. On the strip, the test line and control line were sprayed with streptavidin and an oligonucleotide control probe. In the presence of positive products, RPA products can form a sandwich structure on the test line. Therefore, two red lines will be displayed both on the test line and control line. When there is no positive product, only the control line is shown in red. Its low reaction temperature (37~42 °C) and short time of amplification and detection (30 min) make ASFV realizing point-of-care diagnosis in limited environment.

A rapid sample preparation method for the analysis of stable isotope ratios of beef samples from different countries.

RATIONALE: The use of multi-isotopic analyses to trace beef is gaining wider acceptance, but no uniform standard for the pretreatment method is available for the determination of stable isotope ratios. Drying and defatting of meat samples are usually applied. Thus, a rapid sample preparation procedure is required to provide a reference for the study of beef using stable isotope methods. METHODS: Student's t-test (T-test) was used to determine significant differences between the δ13 C and δ15 N values in traditional and rapid beef sample preparation methods. The δ13 C, δ15 N, δ2 H, and δ18 O values of beef samples from six countries were assayed using elemental analyzer-isotope ratio mass spectrometry. Stable isotope data were subjected to principal component analysis, discriminant analysis, and partial least-squares discriminant analysis (PLS-DA). RESULTS: There was no significant difference (P > 0.05) between the δ13 C and δ15 N values of the two preparation approaches. A classification of satisfactory was obtained with the original-validation rate of 96.6% and the cross-validation rate of 95.9%. The PLS-DA model was correctly validated to differentiate beef samples from six countries. CONCLUSIONS: We describe a rapid sample preparation method for beef samples. A model combining stable isotope data and chemometric methods correctly assigned the origin of beef samples from different countries. The results demonstrated the successful utilization of rapid pretreatment methods to prepare beef samples when using multiple stable isotope analyses to trace beef samples from different countries.

Determination of content of camel milk in adulterated milk samples by normalized real-time polymerase chain reaction system based on single-copy nuclear genes.

BACKGROUND: Compared with the traditional qualitative polymerase chain reaction (PCR), which only identifies the category of species, the quantitative PCR method provides a value, which is very important for appropriate penalty enforcement according to the extent of adulteration. However, most of the current quantitative PCR methods are based on mitochondrial genes, expressing different copy numbers in different cells and reducing the accuracy of quantitative results. In this study, single-copy nuclear housekeeping genes, instead of multicopy mitochondrial genes, were selected as both camel species-specific and reference genes to develop a novel normalized PCR system. RESULTS: This system had an excellent linear correlation (R2 = 0.9614) between camel milk content and Ct ratio (specific/reference genes), and allowed quantitative determination of the content of camel milk in adulterated milk samples. The accuracy was effectively validated using simulated adulterated samples with recoveries ranging from 90% to 120% and coefficient of variation less than 10%, exhibiting sufficient parameters of trueness and precision. CONCLUSIONS: The normalized PCR system based on single-copy nuclear genes is a simple, rapid and reliable method for the determination of the content of camel milk in adulterated milk samples, and also provides technical support for appropriate penalty enforcement. © 2020 Society of Chemical Industry.

Two new defatted beef reference materials, CAAS-1801 and CAAS-1802, for carbon and nitrogen stable isotope ratio measurements.

RATIONALE: Isotope reference materials are essential to enable reliable and comparable isotope data across multiple laboratories. Although many reference materials already exist, the best reference materials should mimic the unknown samples, so new reference materials continue to evolve with the development of isotope research in new product areas. METHODS: Two defatted beef reference materials, CAAS-1801 and CAAS-1802, with substantially different δ13 C values (due to difference in dietary intake), have been prepared as reference materials for stable C and N isotope analysis of meat tissue. Homogeneity, and short- and long-term stability tests of these reference materials have been performed. The δ13 C and δ15 N values of both materials were measured for two-point isotopic normalization against international reference materials by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). A total of nine international laboratories were selected for the joint evaluation. Cochran statistical analysis yielded the values reported here. RESULTS: The defatted beef reference material CAAS-1801 from Heilongjiang province has a δ13 C value of -13.58 ± 0.56‰ relative to VPDB and a δ15 N value of 4.23 ± 0.56‰ relative to N2 in air. The defatted beef reference material CAAS-1802 from Sichuan province has a δ13 C value of -25.03 ± 0.45‰ and a δ15 N value of 4.36 ± 0.69‰. CONCLUSIONS: The two defatted beef reference materials were found to be isotopically stable across a range of ambient temperatures, and to have low volatility and toxicity, which enables them to be useful as stable isotope reference materials in the field of authentication and traceability of meat.

A new retrospective, multi-evidence veterinary drug screening method using drift tube ion mobility mass spectrometry.

RATIONALE: The retrospectivity (the ability to retrospect to a previously unknown compound in raw data) is very meaningful for food safety and risk assessment when facing new emerging drugs. Accurate mass and retention time based screening may lead false positive and false negative results so new retrospective, reliable platform is desirable. METHODS: Different concentration levels of standards with and without matrix were analyzed using ion mobility (IM)-quadrupole-time-of-flight (Q-TOF) for collecting retrospective accurate mass, retention time, drift time and tandem MS evidence for identification in a single experiment. The isomer separation ability of IM and the four-dimensional (4D) feature abundance quantification abilities were evaluated for veterinary drugs for the first time. RESULTS: The sensitivity of the IM-Q-TOF workflow was obviously higher than that of the traditional database searching algorithm [find by formula (FbF) function] for Q-TOF. In addition, the IM-Q-TOF workflow contained most of the results from FbF and removed the false positive results. Some isomers were separated by IM and the 4D feature abundance quantitation removed interference with similar accurate mass and showed good linearity. CONCLUSION: A new retrospective, multi-evidence platform was built for veterinary drug screening in a single experiment. The sensitivity was significantly improved and the data can be used for quantification. The platform showed its potential to be used for food safety and risk assessment.

A Lateral Flow Strip Based Aptasensor for Detection of Ochratoxin A in Corn Samples.

Ochratoxin A (OTA) is a mycotoxin identified as a contaminant in grains and wine throughout the world, and convenient, rapid and sensitive detection methods for OTA have been a long-felt need for food safety monitoring. Herein, we presented a new competitive format based lateral flow strip fluorescent aptasensor for one-step determination of OTA in corn samples. Briefly, biotin-cDNA was immobilized on the surface of a nitrocellulose filter on the test line. Without OTA, Cy5-labeled aptamer combined with complementary strands formed a stable double helix. In the presence of OTA, however, the Cy5-aptamer/OTA complexes were generated, and therefore less free aptamer was captured in the test zone, leading to an obvious decrease in fluorescent signals on the test line. The test strip showed an excellent linear relationship in the range from 1 ng·mL-1 to 1000 ng·mL-1 with the LOD of 0.40 ng·mL-1, IC15 value of 3.46 ng·mL-1 and recoveries from 96.4% to 104.67% in spiked corn samples. Thus, the strip sensor developed in this study is an acceptable alternative for rapid detection of the OTA level in grain samples.

A sandwich dipstick assay for ATP detection based on split aptamer fragments.

Aptamer-based strip assay is an easy, highly efficient and low-cost detection method, which has been developed and easily applied to onsite detection. A new sensitive sandwich dipstick assay for adenosine triphosphate (ATP) detection was successfully developed based on specific recognition between split aptamer fragments and the target. In this method, the thiolated aptamer was first conjugated to the surface of gold nanoparticles (AuNPs), while the biotin-aptamer was immobilized on the surface of a nitrocellulose filter in the test line. In the presence of ATP, the thiol-aptamer/ATP/biotin-aptamer complexes were generated, which led to an obvious increase in optical signals at the test line. Under the optimal determination conditions, an excellent linear logarithmic response to the ATP concentration was obtained within the range of 0.5 µM to 5 mM. The limit of detection (LOD) of 0.5 µM was reached at a signal-to-noise ratio of 3. The dipstick assay showed a good average recovery of 96-108 % with the RSD of less than 20 % in urine samples. The proposed method exhibited high specificity against other nucleotides such as the uridine triphosphate (UTP), cytidine triphosphate (CTP), and guanosine triphosphate (GTP). The results indicated that the dipstick strip may be considered as an inexpensive screening tool for onsite ATP determination. Graphical Abstract A simple split aptamer fragments based sandwich-type dipstick assay was developed for ATP detection.

Comparative study between macrolide regulatory proteins MphR(A) and MphR(E) in ligand identification and DNA binding based on the rapid in vitro detection system.

The macrolide regulatory protein MphR(A) has been widely studied and used in various aspects such as metabolism monitoring, exogenous gene expression, and in vivo and in vitro macrolide antibiotic screening. Another macrolide regulatory protein, MphR(E), has rarely been reported. In this study, in vitro ELISA-type systems were established for MphR(A) and MphR(E) to study their correlation. The reactivity of 14 macrolide antibiotics and pseudo-macrolide antibiotics was tested in the systems. The results indicated that the ligand identification spectra of MphR(A) and MphR(E) were basically consistent. The binding characteristics of MphR(A) and MphR(E) with three corresponding promoter DNA sequences were preliminarily studied. According to the ELISA-type analysis results, MphR(A) and MphR(E) have consistent DNA binding properties, which bind to A-DNA/B-DNA more easily than to C-DNA. This study has confirmed that MphR(E) can bind to the promoter DNA sequences mrx(E) and mph(E) in plasmid pRSB111, and different DNAs can affect the sensitivity of the in vitro detection systems.

Sensitive colorimetric detection of cyromazine in cucumber samples by using label-free gold nanoparticles and polythymine.

Cyromazine (CYR) can cause serious damage to the organs of animals or human beings, and it was found to bind to polythymine (polyT10) via multiple hydrogen bonding interactions. Based on this novel finding, a highly sensitive and simple colorimetric method was developed for CYR detection by using label-free gold nanoparticles (AuNPs) and polyT10. Under the optimized conditions, excellent linearity was acquired for CYR within the range of 1-500 ng mL(-1). In addition, the spectra and color changes of the AuNP solution were measured by spectrophotometry and observed by the naked eye, and the results showed that as low as 1 and 5 ng mL(-1) of CYR could be detected, depending upon the measurement methods. Afterwards, cucumber was selected to investigate the sample matrix effect and a sample pretreatment procedure was developed with simple homogenization and filtration. Even after 200 times dilution, the limit of detection (LOD) and limit of quantitation (LOQ) reached 252 ng g(-1) and 500 ng g(-1), respectively. The LOD and LOQ satisfied the Chinese requirement for the maximum residue limit (MRL), which is 0.5-1 µg g(-1) of CYR in most vegetables. The assay also showed a good average recovery of 83.7-104.8% with the RSD of less than 7% and good selectivity for cyromazine over other pesticides that may exist in vegetable samples. The method proposed in this study was simple, fast, and highly sensitive and accurate, and the test result with this method was visible to the naked eye. Therefore, it could be used for routine determination of CYR residues in cucumber samples.

Ultra-performance LC separation and quadrupole time-of-flight MS identification of major alkaloids in Plumula Nelumbinis.

INTRODUCTION: As an essential medicine and tea source in many countries, Plumula Nelumbinis potentially exerts its major biological activities through its alkaloids. However, the activities of Plumula Nelumbinis are not fully understood due to the lack of studies on its chemical components. OBJECTIVE: To establish an ultra-performance liquid chromatography combined with diode-array detector (UPLC/DAD) method, coupled to an electrospray ionisation with quadrupole time-of-flight mass spectrometry (ESI/QTOF/MS) method, for the separation and identification of Plumula Nelumbinis alkaloids. METHODS: The eluant from an UPLC separation of an ethanol extract of Plumula Nelumbinis was directly infused into an ESI/QTOF/MS system. Both positive and negative ion modes of ESI with low and high collision energy (CE) were used to obtain sufficient MS information. RESULTS: Twenty-one alkaloids were tentatively identified based on their chromatographic characteristics, UV spectra, exact mass, MS fragments and literature reports. They consist of six bis-1-benzyltetrahydroisoquinoline, eleven benzyltetrahydroisoquinoline (including two glycoalkaloids and two quaternary ammoniums), two aporphine, one proaporphine and one indole alkaloids. Eleven were identified in Plumula Nelumbinis for the first time and seven were first reported in Nelumbo nucifera Gaertn. Five compounds, namely norcoclaurine-4'-O-glucoside, norcoclaurine-6-O-glucoside, isolotusine, 6-demethyl-4-demethylN-methylcoclaurine and N-norisoliensinine, were characterised and proposed as new compounds. CONCLUSION: The established UPLC/DAD - ESI/QTOF/MS method is efficient for systematic identification of the alkaloids in Plumula Nelumbinis extract.

Identification and quantitation of phenolic compounds from the seed and pomace of Perilla frutescens using HPLC/PDA and HPLC-ESI/QTOF/MS/MS.

INTRODUCTION: Perilla frutescens (L.) Britt., an essential traditional Asian crop and Chinese medicine, potentially exerts anti-oxidation effects through its phenolic compounds. These compounds have already been reported in perilla seed, however, little is reported in Perilla pomace, the primary waste during oil production of Perilla seed. OBJECTIVE: To investigate major phenolic compounds in perilla seeds and pomaces in order to check whether the pomace could be an alternative resource to the seed for nutritional and medical purposes. METHODS: Compounds in extracts of perilla seeds and pomaces were separated by high-performance liquid chromatography and detected by photodiode array, and by electrospray ionisation with quadrupole time-of-flight tandem mass spectrometry. Herb-markers selected by principal components analysis were then quantified in both seeds and pomaces. Moreover, a fingerprinting approach and multiple discriminant analysis were applied to screen the phenolic markers in 22 samples. RESULTS: Ten phenols were tentatively identified, among which four (rosmarinic acid, luteolin, apigenin and rosmarinic acid-3-O-glucoside) were selected as herb-markers. Perilla seeds and pomaces showed similar phenol profiles, however, the pomaces contained almost two times the amount of the four herb-markers than the seeds. CONCLUSION: The results indicated perilla pomace is a promising alternative source of phenolic compounds that could be recovered and potentially used as natural anti-oxidants.

[Gold nanoparticle-aptamer based colorimetric biosensing assays].

The single strand nucleic acid based aptamer could bound to targets with high sensitivity and specificity. Gold nanoparticles have strong particle space optical effects and could take a color change from red to blue when the dispersed nanoparticles were aggregated. Aptamer could be immobilized through covalent coupling or direct adsorption to the surface of gold nanoparticle. Various approaches have been designed for biosensing based on the target induced aptamer-gold nanoparticle system color changes. The recent developments in the gold nanoparticle-aptamer based colorimetric biosensing assays were reviewed and the directions for future research were discussed and proposed.

Amplification-free quantitative detection of genomic DNA using lateral flow strips for milk authentication.

With the globalization and complexity of the food supply chain, the market is becoming increasingly competitive and food fraudulent activities are intensifying. The current state of food detection faced two primary challenges. Firstly, existing testing methods were predominantly laboratory-based, requiring complex procedures and precision instruments. Secondly, there was a lack of accurate and efficient quantitative detection methods. Taking cow's milk as an example, this study introduced a novel method for nucleic acid quantification in dairy products, based on lateral flow strips (LFS). The core idea of this method is to design single-stranded DNA (ssDNA) probes to hybridize with mitochondrial genes, which are abundant, stable, and species-specific in dairy products, as detection targets. Drawing inspiration from the principles of nucleic acid amplification, this research innovatively established a new DNA hybridization method, named LAMP-Like Hybridization (HybLAMP-Like). Leveraging the denaturation and DNA polymerization functions of the bst enzyme, efficient binding of the probe and template strand was achieved. This method eliminated the need for nucleic acid amplification, simplifying the procedure and mitigating aerosol contamination, thereby ensuring the accuracy of the detection results. The method exhibited exceptional sensitivity, capable of detecting extremely low to 12.5 ng in visual inspection and 3.125 ng when using a reader. In terms of practicality, it could achieve visual detection of cow's milk content as low as 1% in adulterated dairy products. When combined with a portable LFS reader, it also enabled precise quantitative analysis of milk adulteration.

An instrument-free, integrated micro-platform for rapid and multiplexed detection of dairy adulteration in resource-limited environments.

In dairy industry, expensive yak's milk, camel's milk, and other specialty dairy products are often adulterated with low-cost cow's milk, goat's milk and so on. Currently, the detection of specialty dairy products typically requires laboratory settings and relies on skilled operators. Therefore, there is an urgent need to develop a multi-detection technology and on-site rapid detection technique to enhance the efficiency and accuracy of the detection of specialty dairy products. In this study, we introduced a fully integrated and portable microfluidic detection platform called Sector Self-Driving Microfluidics (SDM), designed to simultaneously detect eight common species-specific components in milk. SDM integrated nucleic acid extraction, purification, loop-mediated isothermal amplification (LAMP), and lateral flow strip (LFS) detection functions into a closed microfluidic system, enabling contamination-free visual detection. The SDM platform used a constant-temperature heating plate, powered by a mobile battery, eliminated the need for additional power support. The SDM platform achieved nucleic acid enrichment and transfer through magnetic force and liquid flow driven by capillary forces, operating without external pumps. The standalone SDM platform could detect dairy components with as low as 1% content within 1 h. Validation with 35 commercially available samples demonstrated 100% specificity and accuracy compared to the gold standard real-time PCR. The SDM platform provided the dairy industry with an efficient, convenient, and accurate detection tool, enabling rapid on-site testing at production facilities or sales points. This facilitated real-time monitoring of quality issues during the production process, quickly identifying potential risks and preventing substandard products from entering the market.

A clean and sustainable method for recycling of lithium from spent lithium iron phosphate battery powder by using formic acid and oxygen.

With the widespread adoption of lithium iron phosphate (LiFePO4) batteries, the imperative recycling of LiFePO4 batteries waste presents formidable challenges in resource recovery, environmental preservation, and socio-economic advancement. Given the current overall lithium recovery rate in LiFePO4 batteries is below 1 %, there is a compelling demand for an eco-friendly, cost-efficient, and sustainable solution. This study introduces a green and sustainable recycling method that employs environmentally benign formic acid and readily available oxygen as reaction agents for selectively leaching lithium from discarded lithium iron phosphate powder. Formic acid was employed as the leaching agent, and oxygen served as the oxidizing agent. Utilizing a single-factor variable approach, various factors including formic acid concentration, oxygen flow rate, leaching time, liquid-to-solid ratio, and reaction temperature were individually investigated. Moreover, the feasibility of this method was explored mechanistically by analyzing E-pH diagrams of the Li-Fe-P-H2O system. Results demonstrate that under conditions of 2.5 mol/L formic acid concentration, 0.12 L/min oxygen flow rate, 25 mL/g liquid-to-solid ratio, 70 °C reaction temperature, and 3 h reaction time, lithium leaching efficiency exceeds 99.9 %, with iron leaching efficiency only at 1.7 %. Moreover, we also explored using air instead of oxygen as the oxidant and get the excellent lithium leaching rate (97.81 %) and low iron leaching rate (4.81 %), which shows the outstanding selectivity. Furthermore, the environmentally benign composition of the chemical reagents, comprising only C, H, and O elements, establishes it as a genuinely green and sustainable technology for secondary resource recovery. It can be considered as a highly environmentally friendly, cost-effective, and efficient approach. Nevertheless, in the current context of carbon neutrality and sustainable development, this method undoubtedly holds excellent prospects for industrialization.

Critical review and recent advances of emerging real-time and non-destructive strategies for meat spoilage monitoring.

Monitoring and evaluating food quality, especially meat quality, has received a growing interest to ensure human health and decrease waste of raw materials. Standard analytical approaches used for meat spoilage assessment suffer from time consumption, being labor-intensive, operation complexity, and destructiveness. To overcome shortfalls of these traditional methods and monitor spoilage microorganisms or related metabolites of meat products across the supply chain, emerging analysis devices/systems with higher sensitivity, better portability, on-line/in-line, non-destructive and cost-effective property are urgently needed. Herein, we first overview the basic concepts, causes, and critical monitoring indicators associated with meat spoilage. Then, the conventional detection methods for meat spoilage are outlined objectively in their strengths and weaknesses. In addition, we place the focus on the recent research advances of emerging non-destructive devices and systems for assessing meat spoilage. These novel strategies demonstrate their powerful potential in the real-time evaluation of meat spoilage.

A smartphone-based diagnostic analyzer for point-of-care milk somatic cell counting.

BACKGROUND: Mastitis, a pervasive and detrimental disease in dairy farming, poses a significant challenge to the global dairy industry. Monitoring the milk somatic cell count (SCC) is vital for assessing the incidence of mastitis and the quality of raw cow's milk. However, existing SCC detection methods typically require large-scale instruments and specialized operators, limiting their application in resource-constrained settings such as dairy farms and small-scale labs. To address these limitations, this study introduces a novel, smartphone-based, on-site SCC testing method that leverages smartphone capabilities for milk somatic cell identification and enumeration, offering a portable and user-friendly testing platform. RESULTS: The central findings of our study demonstrate the effectiveness of the proposed method for counting milk somatic cells. Its on-site applicability, facilitated by the microfluidic chip, optical system, and smartphone integration, heralds a paradigm shift in point-of-care testing (POCT) for dairy farms and smaller laboratories. This approach bypasses complex processing and presents a user-friendly solution for real-time SCC monitoring in resource-limited settings. This device boasts several unique features: small size, low cost (<$1,000 total manufacturing cost and <$1 per test), and high accuracy. Remarkably, it delivers test results within just 2 min. Actual-sample testing confirmed its consistency with results from the commercial Bentley FTS/FCM cytometer, affirming the reliability of the proposed method. Overall, these results underscore the potential for transformative change in dairy farm management and laboratory testing practices. SIGNIFICANCE: In summary, this study concludes that the proposed smartphone-based method significantly contributes to the accessibility and ease of SCC testing in resource-limited environments. By fostering the use of POCT technology in food safety control, particularly in the dairy industry, this innovative approach has the potential to revolutionize the monitoring and management of mastitis, ultimately benefiting the global dairy sector.

Development of a new fluorescence immunochromatography strip for detection of chloramphenicol residues in chicken muscles.

BACKGROUND: Chloramphenicol (CAP), an antimicrobial drug that is widely used in animal feed, would have a negative effect on human health due to its low elimination rate and relatively high residue in animal food. It is important to develop a rapid and economic method to determine CAP in animal food to ensure that human health is not affected. RESULTS: A new fluorescence immunochromatography strip was developed and established for the detection of CAP residue in chicken muscles for the first time. A CAP-bovine serum albumin conjugate, monoclonal antibody and polyclonal antibody against CAP were applied to constitute a fluorescence immunochromatography strip. The fluorescence intensity was detected by a charge-coupled device scanner and transformed to a digital value. The CAP linearity working range was from 0.1 ng mL(-1) to 20 ng mL(-1) with a limit of detection of 0.1 ng mL(-1) within 10 min. The performance of the strip assay was compared with a commercial ELISA kit and the correlation coefficient was 0.99, which indicated that the new strip assay had a good quantification ability for CAP. CONCLUSION: The fluorescence immunochromatography strip was successfully applied to the detection of CAP residues in chicken samples. To our knowledge, it is the first report regarding the development of a fluorescence immunochromatography method for screening CAP in animal samples.