Sensitive Method Research Articles

Comparative Assessment of the Incidence of Unilateral and Bilateral Lower Limb Deep Venous Thrombosis in Symptomatic and Clinically Suspected Patients

Objective: Deep vein thrombosis (DVT) is a familiar coagulation pathology that can be diagnosed through Doppler ultrasonography. This is a highly specific and sensitive method for the assessment of thrombosis. The present study aims to assess the incidence of lower limb DVT in a cohort of symptomatic and clinically suspected Saudi Arabian patients. Methods: This is a retrospective study that incorporated 1051 DVT patients over three years between January 2015 and December 2017 which presented with signs and symptoms of single or bilateral disease. Data were collected on the history of oedema, swelling, pain, tenderness, weakness, hotness, redness, fever, and vomiting. Possible risk factors that may increase the probability of developing DVT were also recorded. Results: The incidence of bilateral lower limb DVT in suspected patients was 84.5% negative and 15.5% positive. Old age was found to be the most common risk factor that resulted in DVT. The incidence of DVT is more common among females, whereas males were with all the bilateral cases. Conclusions: Screening tests are needed for DVT in symptomatic and asymptomatic patients.

Modified throughput ninhydrin method for the qualitative assessment of dietary protein absorption in pig plasma.

Protein maldigestion and malabsorption lead to malnutrition and are a feature of exocrine pancreatic insufficiency (EPI). Although it is the current standard, measurement of nitrogen in stool to assess protease activity is indirect. Up to 80% of hydrolysed proteins appear in blood in the form of peptides, so we developed a method to measure peptide-derived amino acids in plasma as a relevant measure of proteolysis, verified its accuracy, precision, and linearity, and validated it in a porcine model. We modified a ninhydrin method. Large proteins were eliminated from plasma with 10 kDa-cut-off centrifugal filters. Free and total amino acids were measured in permeate before and after its hydrolysis. Peptide-derived amino acids were quantified by subtracting free amino acids from total amino acids. We verified the method in vitro and by comparing results in healthy and EPI pigs. The accuracy of the analysis was close to 100%, with excellent precision (mean relative standard deviation for low, medium, and high amino acid levels = 0.88%) and with stringent linearity (r2 = 0.986, %RE = 5.23). The high-throughput ninhydrin method detected levels of peptide-derived amino acids in vivo with maximal changes seen approximately 2 hours postprandially in young pigs. The AUC and Cmax were significantly higher in healthy compared to EPI pigs (P = .0026 and P = .0037, respectively). The high-throughput ninhydrin method is a sensitive, reliable, and practical method for the estimation of dietary peptide-derived amino acids. This assay endpoint could serve as a direct biomarker of protein digestion and absorption.

Detection of AFB1 by Immunochromatographic Test Strips Based on Double-Probe Signal Amplification with Nanobody and Biotin-Streptavidin System.

Aflatoxin B1 (AFB1) is highly toxic and difficult to prevent. It is mainly produced by fungi and exists in plants and animals and is classified by the World Health Organization as a class I carcinogen, posing a serious threat to human and animal health. Therefore, it is important to establish an efficient, sensitive, and on-site detection method for AFB1 to protect human health. The immunochromatographic test strip method is simple, sensitive, and can achieve real-time detection. However, traditional immunochromatographic test strips have low sensitivity due to their relatively weak optical properties. In this study, Nb-G8 was biotinylated using a chemical method. Two sizes of gold nanoflowers (AuNFs) were prepared and combined with biotinylated G8 and streptavidin to form two types of probes. These probes were sprayed on gold standard pads and expanded pads, respectively, to enhance the signals through the high affinity interaction between streptavidin and biotin. Under the optimal experimental conditions, the half maximal inhibitory concentration (IC50) of this method was 5.0 ng/mL and the limit of detection (IC10) was 0.03 ng/mL, which increased the sensitivity of the test strip by four-fold compared with that of the traditional biotinylated nanoantibody immunochromatography test strip and had a wider detection range. In conclusion, the use of a high-affinity amplification signal between biotin and streptavidin is a valuable method for the detection of aflatoxin.

Comparative Characteristics of Immunochromatographic Test Systems for Tylosin Antibiotic in Meat Products.

Tylosin (TYL) is a macrolide antibiotic widely used in animal husbandry. Due to associated health risks, there is a demand for sensitive methods for mass screening of TYL in products of animal origin. This article describes the development of lateral flow immunoassays (LFIAs) for TYL detection using direct (anti-TYL antibodies conjugated with nanoparticles) and indirect antibody labeling (anti-species antibodies conjugated with nanoparticles and combined with native anti-TYL antibodies). The choice of LFIA conditions, such as concentrations of hapten-protein conjugates, specific antibodies, and gold nanoparticle (GNP) conjugates with antibodies, as well as incubation time of reagents and the concentration of detergent in the sample buffer, is presented. The achieved limits of TYL detection using LFIAs with indirect labeling were 0.8 ng/mL (visual) and 0.07 ng/mL (instrumental), compared to 4 ng/mL (visual) and 0.4 ng/mL (instrumental) for the case of direct labeling. The sensitivity of the LFIA using the indirect format was up to seven times higher, allowing the determination of the target analyte at low concentrations. TYL detection in ground meat using LFIA with indirect antibody labeling ranged from 76-119%.

A Narrative Review of Chromatographic Bioanalytical Methods for Quantifying Everolimus in Therapeutic Drug Monitoring Applications

Background: Methods for measuring drug levels in the body are crucial for improving therapeutic drug monitoring (TDM) and personalized medicine. In solid-organ transplants, TDM is essential for the management of immunosuppressive drugs to avoid toxicity and organ rejection. Everolimus is a commonly used immunosuppressant with a small range of safe doses; therefore, it is important to adjust the dose according to each patient's needs. Therefore, reliable methods are required to accurately measure everolimus levels. This study aims to conduct a comprehensive and updated narrative review of chromatographic bioanalytical methods for everolimus quantification. Methods: The authors searched for original research articles published between 2013 and 2023 in Scopus and PubMed and found 295 articles after removing duplicates. Based on their titles and summaries, 30 articles were selected for a detailed review and 25 articles were included in the final analysis. Results: Among the 25 studies, 16 used protein precipitation, mainly with methanol, to prepare the samples, 12 used high-performance liquid chromatography, 11 used ultra-performance liquid chromatography, and 2 used both. Almost all the studies (24 of 25) used tandem mass spectrometry for detection, whereas only 1 used ultraviolet. Conclusions: This comprehensive review of bioanalytical methods for measuring everolimus using chromatography is a useful resource for researchers developing bioanalytical methods for TDM applications. Future trends in everolimus measurement include achieving lower detection limits, owing to the trend of reducing drug doses in therapy by improving sample extraction techniques and using more sensitive methods.

Exploring the Impact of In Vitro-Transcribed mRNA Impurities on Cellular Responses.

Advances in mRNA technology have enabled mRNA-based therapies to enter a new era of medicine. Such therapies benefit from a single, standardized in vitro transcription (IVT) manufacturing process applicable to a wide range of targets. This process includes several downstream purification steps, which aim to eliminate impurities that potentially affect safety and efficacy. However, it is not fully understood which impurities are the most critical; hence, some efforts are still needed to establish the correlation between RNA impurities and their role in limiting therapeutic efficacy. To study this relationship, we produced in vitro-transcribed mRNAs using several bacteriophage T7 RNA polymerases, including one wild-type and four engineered variants. Important attributes of the mRNA such as integrity, purity, and functional activity were then measured using advanced physicochemical and cellular assays. For impurities including abortive transcripts, mRNAs containing partial poly(A) tails, and double-stranded (ds)RNA byproducts, structure-function relationships have been established by tracking cellular responses (i.e., protein expression, reactogenicity) in multiple cell models. By varying the T7 RNA polymerase, different levels of sense-antisense dsRNA byproducts were measured by mass photometry, contributing directly to immunological reactogenicity in bone marrow-derived dendritic cells. T7 RNA polymerase differences with regard to short (<20 nucleotides) 3'-loopback dsRNA byproducts were also further investigated using native mass spectrometry by precisely resolving these impurities at the nucleotide level. Overall, this study highlights the importance of developing sensitive and advanced analytical methods to characterize IVT mRNA impurities and understand their interaction with cellular machinery in order to ensure quality control of RNA-based therapies.

Electrochemical Sensing Strategies for Synthetic Orange Dyes.

This review explores electrochemical sensing strategies for synthetic orange dyes, addressing the growing need for sensitive and selective detection methods in various industries. We examine the fundamental principles underlying the electrochemical detection of these compounds, focusing on their redox behavior and interaction with electrode surfaces. The review covers a range of sensor designs, from unmodified electrodes to advanced nanomaterial-based platforms. Chemically modified electrodes incorporating polymers and molecularly imprinted polymers are discussed for their enhanced selectivity. Particular attention is given to nanomaterial-based sensors, including those utilizing carbon nanotubes, graphene derivatives, and metal nanoparticles, which have demonstrated exceptional sensitivity and wide linear ranges. The potential of biological-based approaches, such as DNA interaction sensors and immunosensors, is also evaluated. Current challenges in the field are addressed, including matrix effects in complex samples and long-term stability issues. Emerging trends are highlighted, including the development of multi-modal sensing platforms and the integration of artificial intelligence for data analysis. The review concludes by discussing the commercial potential of these sensors in food safety, environmental monitoring, and smart packaging applications, emphasizing their importance in ensuring the safe use of synthetic orange dyes across industries.

Eco-Friendly Analytical Approach for Sensitive Spectrofluorimetric Determination of the Flavonoid Chrysin in Capsules and Human Plasma.

Chrysin is a plant flavonoid that has different therapeutic effects as anti-inflammatory, anti-cancer, anti-oxidant, and immune booster. Spectrofluorimetry has received a lot of interest lately because of itsecological greenness and analytical performance. This approach employed the native fluorescence of chrysin at 339nm following excitation at 231nm in distilled water. Modern advances in analytical chemistry have been used to lessen occupational and environmental concerns by employing distilled water as a dilution solvent throughmethod development and application. The approach was found to be excellent green supported byeco-scale score of 97and 0.94AGREErating, in addition to an overall whiteness score of 88.80. The design aimed to analyze chrysin in raw materials, Chrysin® capsules and human plasma. The method was linear over0.5-7.0ngmL⁻1 chrysin, with LOD of 0.06ngmL⁻1 and LOQ of 0.20ngmL⁻1. The offered methodwas effectively applied for determination of chrysin inthe commercial capsules Chrysin® and spiked human plasma samples with average recoveries of 99.76%and 99.98%, respectively for capsules andspiked human plasma. Up to date, no spectrofluorimetric method has been described for chrysin analysis, then, this presented an opportunity to develop a sensitive, quick, reliable, environmentally friendly, and valid fluorescence-based method.

Scientifc Validation and Chromatographic Method Development for the Estimation of Piperine in Herbal Formulation Babbularishta: A Quality Control Strategy for Critical Quality Attributes

Background: Babbularishta is an Ayurvedic medicine in liquid form used for the treatment of phthisis, skin diseases, urinary disorders,, and breathing problems. It is also beneficial in cases of blood disorders, acne, dermatitis, hemoptysis, lung injury, asthma, persistent cough, whooping cough, etc. Objective: The functional role of this study is to develop a simple, novel, precise, accurate, reliable, and selective RP-HPLC method for the estimation of piperine content in herbal drug formulations (Babbularista). Methods: A traditional approach to method development could fail to meet the desired separation. Consideration of the current regulatory requirement for analytical method development and RP-HPLC method for routine analysis of piperine in the herbal formulation has been optimized using an analytical Quality by Design (QbD) approach. Three laboratory formulations and three marketed preparations of Babularishta were investigated for organoleptic parameters, physicochemical parameters, and validation. The mobile phase composition (methanol and water % as A), pH (B), and flow rate (mL/min as C) were selected as independent variable,. In contrast, retention time (min. as Y2), area (AU as Y1) is selected as dependent variables. Results: The fingerprinting method was developed and optimized by using the AQbD approach. Piperine content was found to be in Piper nigrum (Marica) 3.01±0.01527 % w/w and in Piper longum (Pipali) 2.74±0.01154% w/w in Babbularista. Conclusion: An attempt has been made to develop quality control parameters of Babbularista by developing a suitable and sensitive HPLC methods for the quantitation of piperine in herbal drug formulations (Babbularista). The developed method was found to be simple, accurate, precise,, and economical for the estimation of piperine in herbal formulations.

A comparison of visual and molecular methods for inferring biological communities in aquaculture enriched sediments - Impact assessment and cost-benefit analysis

Nutrients introduced to the environment by finfish aquaculture pose environmental risks, which can be mitigated by robust environmental monitoring. Biological communities in soft sediments are good indicators of aquaculture derived environmental changes. Traditionally, monitoring programs have visually surveyed macrofauna communities. However, DNA metabarcoding is a potentially more efficient alternative. We compared alpha diversity, multivariate dispersion and taxonomic composition of macrofauna communities with metabarcoding derived bacterial and eukaryote communities along an organic enrichment gradient at a salmon farm in Tasmania, Australia. Additionally, we conducted a cost-benefit analysis comparing the approaches. All methods identified indicator taxa that changed in abundance over the enrichment gradient. Macrofauna analysis was the most sensitive method for detecting changes in alpha diversity, while metabarcoding was most sensitive for multivariate dispersion. Taxonomic composition of animal communities derived from the two methods differed drastically. Metabarcoding was cheaper than macrofauna for ≥93 samples and quicker for ≥14 samples.

Development of a rapid magnetic relaxation switching aptasensor for detection of saxitoxin using Fe3+/silver nanoparticles reaction system

Saxitoxin (STX) is a highly toxic marine bio-toxin, which has attracted great attention in the field of environmental and food safety. It is of crucial importance to develop efficient, sensitive and cost-effective methods for detecting STX. Here, we designed a magnetic relaxation switching (MRS) aptasensor for detection of STX based on FeCl3-regulated the aptamer-functionalized silver nanoparticles-coated magnetic nanoparticles (MNP@Ag NPs). In the light of the sensing effect of transverse relaxation time (T2) for optimizing, the etched time, the concentration of MNP@Ag NPs, the concentration of aptamers and incubation time were 15 min, 4 mg mL−1, 0.4 μM and 90 min, respectively. The MRS aptasensor showed good linearity amidst the sensing range of 0.2 μM to 1.0 μM and the limit of detection (LOD, S/N = 3) of 0.18 μM. Additionally, the MRS aptasensor demonstrated excellent sensitivity, reproducibility, and stability in clams and mantis shrimps. The recovery of STX ranged from 82.6 % to 101.5 % with low relative standard deviation (RSD) values, suggesting its effectiveness for detecting STX across a wide array of seafood samples.

Evaluation of Fecal Sample Pooling for Real-Time RT-PCR Testing SARS-CoV-2 in Animals

During the COVID-19 pandemic, veterinary diagnostic laboratories tested both human and animal samples and needed to ensure that they could accurately perform large numbers of diagnostic tests in a timely manner. Sample pooling, a methodology used effectively for over 80 years as a surveillance tool for screening large numbers of potentially infected individuals, was employed. Given its sensitivity, real-time polymerase chain reaction (PCR) is more suitable for employing this strategy, as compared to other less sensitive testing methods. In this study, we evaluated the capability of detecting SARS-CoV-2 in both 5-sample and 10-sample pools of feces using real-time reverse transcriptase polymerase chain reaction (rRT-PCR) as well as determined the level of sensitivity. A blinded method test (BMT) by an independent laboratory was conducted to assess the five-sample fecal pool. To complement detection capability, the stability of the genome within a PBS fecal suspension was measured under various time and temperature conditions across a 28-day period. Our results showed that the limit of detection for 5-sample and 10-sample fecal pools is 12.8 and 6.4 genome copies in a 25 µL PCR, respectively. The 5-sample and 10-sample pooling resulted in a cycle threshold (Ct) value loss of 2.35 and 3.45, as compared to Ct values of known positive individual samples, but consistent detection was still achieved in pools containing positive samples with an original Ct below 36 and 34, respectively. The simulation of clinical five-sample pooling showed that all positive samples could be detected regardless of the number (1–3) of positive samples in each pool. The BMT results demonstrated excellent sensitivity (100 copies/reaction) in five-sample pools for the detection of SARS-CoV-2 RNA even though a fecal matrix effect was observed. Finally, our results show that the SARS-CoV-2 genome remains stable over a wide range of time and temperature variations. Overall, our findings provide solid data to scale up SARS-CoV-2 testing capacity in veterinary diagnostic laboratories.

Development of a 17-plex STR typing system for the identification of individuals and parentage testing in cattle

Accurate identification of animals and the verification of their parentage can be used to pedigree populations and support selective breeding. The International Society for Animal Genetics recommended 16 cattle STRs for individual identification and parentage testing in cattle, but no multiplex STR typing system contains these 16 STRs. Here, we develop an efficient 17-plex multiplex typing system for cattle that contains the 16 ISAG recommend STRs and a sex-determining marker. Compared to the Bovine Parenting Typing Kit (containing 11 of the 16 ISAG recommend STRs), our new typing system not only increases the number of molecular markers, but also simplifies the PCR operation and shortens the time for the typing procedure (from 4.5 h to 1 h 37 min). Profile can be generated from a single PCR reaction using as little as 1 ng of DNA. The combined probabilities of paternity exclusion CPEduo and CPEtrio were 0.999804697 and 0.999999260, respectively. These results indicate that our 17-plex typing system is a fast, sensitive and species-specific method for the identification of individuals and their parentage for cattle. The application of this system will improve the efficiency of the identification of cattle individuals and their paternity, supporting population genetic research and the selective breeding of cattle.

Changes in Water Surplus or Deficit and Possible Drivers in the North China Plain During 1961–2022

ABSTRACTIn the North China Plain (NCP), the assessment of water surplus or deficit (WSD), which is calculated as precipitation minus reference evapotranspiration (ET0), holds significant implications for water resource management and agricultural irrigation decision‐making, given the region's long‐standing severe shortage of water resources. However, the magnitude, trend and climatic drivers of WSD remain poorly understood in the NCP. This study analysed the spatial and temporal characteristics of WSD, and quantified the contribution of climatic factors to WSD based on the sensitivity and contribution rate analysis methods with climatic data from 75 meteorological stations. The result showed that: (1) Annual WSD decreased mainly in northeastern NCP and increased significantly in southern NCP during 1961–2022. Annual WSD increased slightly from 1961 to 2022 at a rate of 1.63 mm a−2 mainly due to the more significant decrease (−1.88 mm a−2) in ET0 compared to precipitation (−0.25 mm a−2). (2) In terms of the sensitivity of WSD to climatic factors, relative humidity had the highest sensitivity, followed by net radiation, wind speed, precipitation and average air temperature. (3) Significant declines of wind speed were the most dominant factor affecting WSD variation in most part of NCP during most of a year, and net radiation of four stations in the western high‐elevation regions played the most important role. This study enhances comprehension of the impact of climate change on WSD in the NCP and provides a reference for improving management of agricultural water resources under NCP's evolving climatic conditions.

CuO@3D graphene modified glassy carbon electrode towards the detection of Orange II and Rhodamine B

Synthetic dyes are illegally used in foodstuffs and cause serious health issues in humans due to their carcinogenic nature. To avoid serious health issues, it is compulsory to detect and remove even the minute quantities of these harmful dyes in foodstuffs. Electrochemical sensors are accredited as an efficient and promising platform for the robust and sensitive determination of food toxins in various foodstuffs. Therefore, an efficient, facile, and competent sensor is devised for the simultaneous detection of Orange II (OR II) and Rhodamine B (RhB) supported by rGO and CuO nanoparticles. The synergism between rGO’s immense surface area and the adsorption properties of CuO enhances selectivity and response time for the detection of OR II and RhB. This work elaborated the synthesis, characterization, and electrochemical behavior of CuO@3DGr electrode towards simultaneous sensing of OR II and RhB. Physicochemical techniques were utilized to validate the fabrication of targeted material. On the other hand, the electrochemical features of the developed sensor were characterized by cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). Differential pulse voltammetry technique was employed to detect simultaneously Orange II and Rhodamine B on the surface of bare (GCE), GO/GCE, CuO/GCE, and CuO@3DGr/GCE. Multi-analyte detection is possible with DPV, a sensitive electrochemical method. Based on each toxin’s specific electrochemical signature, the sensor may generate separate peaks by delivering a sequence of potential pulses and detecting the ensuing current. The parameters which influence the performance of the modified sensor were carefully evaluated. Under ambient conditions, the developed sensor exhibited excellent electrocatalytic activity in oxidation at 0.67 V of OR II and 0.96 V RhB with a low limit of detection 08 nM for OR II and 4.5 nM for RhB in Britton- Robinson buffer (BRB pH:7). The described methodology allowed a robust and fast analysis of food toxins in different foodstuff establishing this sensor as a novel tool for detecting food toxins. Tap water was used to analyze the practical applicability of developed electrode material and suitable results were achieved. These results showed that the as-synthesized novel electrochemical sensor has the potential for ultrasensitive determination and detection of toxins in different foodstuffs.

A highly sensitive electrochemical aptasensor for detecting broad-spectrum estrogen molecules in clinical samples

The lack of sensitive and accurate monitoring methods for in vivo estrogen levels presents challenges for better prevention of estrogen-induced diseases. We have developed a label-free electrochemical aptasensor that demonstrates high sensitivity and selectivity for the broad-spectrum detection of estrogen molecules. This biosensor uses gold nanoparticles for electrochemical signal amplification and aptamers for broad-spectrum target recognition, enabling precise detection of trace amounts of estrogen in serum samples. The aptasensor demonstrates high sensitivity in estrogen detection, with a linear detection range of 0.01–1 nM and a minimum detection limit of 3 pM. It also exhibits excellent selectivity and interference resistance, with a detection error of less than 19 %, even in the presence of high concentrations of other biological substances. Additionally, molecular dynamics simulations were performed to provide insights into the molecular mechanism of aptamer broad-spectrum recognition and construction principles underlying the sensor. We anticipate that this aptasensor will serve as a robust, convenient, and cost-effective detection method, offering a valuable solution for the prevention of estrogen-induced diseases.

Development of a Lateral Flow Strip-Based Recombinase-Aided Amplification for Active Streptococcus dysgalactiae emerging in channel catfish (Ictalurus punctatus)

Streptococcus dysgalactiae has become an important pathogen affecting mammals and fish (especially farmed fish). The development of a rapid, accurate, and sensitive diagnostic method will aid in the prevention of S. dysgalactiae infection. In this study, a method combining recombinase-aided amplification and a lateral flow dipstick (RAA-LFD) was developed to detect active S. dysgalactiae infection. The RAA-LFD detection was based on the ISP gene of S. dysgalactiae as the target, which could be accomplished with the lowest detection limit of 1.002×102 pg/μL reaction under optimal reaction conditions of 39 °C for 15 min. RAA-LFD and conventional PCR were used to detect 50 experimental samples invaded by S. dysgalactiae disease materials. The results showed that the positive concordance rate of the two methods was 97.6%, the negative concordance rate was 90.0%, and the total concordance rate was 98.0%. Compared with conventional PCR, the Area Under the ROC Curve (AUC) of RAA-LFD was 0.950, and the sensitivity and specificity were 100% and 90%, respectively. The RAA-LFD of S. dysgalactiae infection is convenient for rapid clinical detection.

An optimized whole-body corticosteroid hormones quantification method by LC-MS/MS for assessing stress levels in European glass eels (Anguilla anguilla)

The European eel (Anguilla anguilla) juvenile stage exhibits facultative estuarine migration. The causes of this behavior are yet unknown but it may have an impact on the population's fate by altering the sex ratio of the population. Recent studies have highlighted potential stress-related issues in glass eels settling in estuaries but studying stress response in small organisms requires sensitive, accurate and precise analytical methods. The aims of the present study are (i) to develop a whole-body Liquid Chromatography-Mass Spectrometry (LC-MS/MS) method for the simultaneous determination of several stress hormones in low-body mass fish; (ii) to apply this method to glass eels to study their responses to acute stress (iii) to test the effect of anxiolytics (diazepam) on these responses. Our results showed that enhanced LC-MS/MS analysis reduced detection limits and improved accuracy and precision for the quantification at the individual level. Following an acute stress, cortisol concentration significantly increased in glass eels and a 15 h diazepam exposure significantly reduced cortisol levels highlighting a marked anxiolytic effect on this species.

Simultaneous Quantification of Serum Symmetric Dimethylarginine, Asymmetric Dimethylarginine and Creatinine for Use in a Routine Clinical Laboratory.

Background Symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA) are naturally occurring amino acids classed as uremic toxins by the EUTOX working group. SDMA is principally excreted through the kidneys and is a well-known renal function marker, ADMA is a potent inhibitor of nitric oxide production. Here, we describe the development of a rapid and sensitive liquid chromatography tandem mass spectrometry method for simultaneous measurement of SDMA, ADMA and creatinine. Method Serum samples were prepared by protein precipitation and dilution with acetonitrile prior to injection onto a Waters TQS-Micro. Multiple reaction monitoring was used to detect SDMA, ADMA, creatinine, and their corresponding internal standard transitions after separation with a HILIC analytical column. Sample stability and intra-individual variation studies were also assessed following ethical approval. Results The retention time for creatinine was 0.43, SDMA 1.10 and ADMA 1.14 minutes. Mean recovery for creatinine was 103%, SDMA was 100% and ADMA was 103%, matrix effects were minimal (<6%). Lower limit of quantitation for creatinine and SDMA/ADMA was 17.5 µmol/L and 0.1 µmol/L respectively. Analytical imprecision showed a coefficient of variation <10% for all analytes across the working range of the assays. Intra-individual variation for creatinine was 4.7%, SDMA 7.5% and ADMA 7.6%. Discussion We have developed a rapid assay for LC-MS/MS measurement of SDMA, ADMA and creatinine in a routine clinical laboratory. It is simple, reproducible, and easy to perform. The stability of SDMA and ADMA pre- and post-centrifugation allows for their routine use without any special sample handling requirements.

Discovering dynamics and parameters of nonlinear oscillatory and chaotic systems from partial observations

Despite rapid progress in data acquisition techniques, many complex physical, chemical, and biological systems remain only partially observable, thus posing the challenge to identify valid theoretical models and estimate their parameters from an incomplete set of experimentally accessible time series. Here, we combine sensitivity methods and ranked-choice model selection to construct an automated hidden dynamics inference framework that can discover predictive nonlinear dynamical models for both observable and latent variables from noise-corrupted incomplete data in oscillatory and chaotic systems. After validating the framework for prototypical FitzHugh-Nagumo oscillations, we demonstrate its applicability to experimental data from squid neuron activity measurements and Belousov-Zhabotinsky reactions, as well as to the Lorenz system in the chaotic regime. Published by the American Physical Society 2024