Sensitive Monitoring Research Articles

Recent Advances in Microfluidics for the Early Detection of Plant Diseases in Vegetables, Fruits, and Grains Caused by Bacteria, Fungi, and Viruses.

In the context of global population growth expected in the future, enhancing the agri-food yield is crucial. Plant diseases significantly impact crop production and food security. Modern microfluidics offers a compact and convenient approach for detecting these defects. Although this field is still in its infancy and few comprehensive reviews have explored this topic, practical research has great potential. This paper reviews the principles, materials, and applications of microfluidic technology for detecting plant diseases caused by various pathogens. Its performance in realizing the separation, enrichment, and detection of different pathogens is discussed in depth to shed light on its prospects. With its versatile design, microfluidics has been developed for rapid, sensitive, and low-cost monitoring of plant diseases. Incorporating modules for separation, preconcentration, amplification, and detection enables the early detection of trace amounts of pathogens, enhancing crop security. Coupling with imaging systems, smart and digital devices are increasingly being reported as advanced solutions.

Exploring uncharted territory: new frontiers in environmental DNA for tropical fisheries management.

Tropical ecosystems host a significant share of global fish diversity contributing substantially to the global fisheries sector. Yet their sustainable management is challenging due to their complexity, diverse life history traits of tropical fishes, and varied fishing techniques involved. Traditional monitoring techniques are often costly, labour-intensive, and/or difficult to apply in inaccessible sites. These limitations call for the adoption of innovative, sensitive, and cost-effective monitoring solutions, especially in a scenario of climate change. Environmental DNA (eDNA) emerges as a potential game changer for biodiversity monitoring and conservation, especially in aquatic ecosystems. However, its utility in tropical settings remains underexplored, primarily due to a series of challenges, including the need for a comprehensive barcode reference library, an understanding of eDNA behaviour in tropical aquatic environments, standardized procedures, and supportive biomonitoring policies. Despite these challenges, the potential of eDNA for sensitive species detection across varied habitats is evident, and its global use is accelerating in biodiversity conservation efforts. This review takes an in-depth look at the current state and prospects of eDNA-based monitoring in tropical fisheries management research. Additionally, a SWOT analysis is used to underscore the opportunities and threats, with the aim of bridging the knowledge gaps and guiding the more extensive and effective use of eDNA-based monitoring in tropical fisheries management. Although the discussion applies worldwide, some specific experiences and insights from Indian tropical fisheries are shared to illustrate the practical application and challenges of employing eDNA in a tropical context.

Machine learning powered CN-coordinated cobalt nanoparticles embedded cellulosic nanofibers to assess meat quality via clenbuterol monitoring

The World Anti-Doping Agency (WADA) has prohibited the use of clenbuterol (CLN) because it induces anabolic muscle growth while potentially causing adverse effects such as palpitations, anxiety, and muscle tremors. Thus, it is vital to assess meat quality because, athletes might have positive test for CLN even after consuming very low quantity of CLN contaminated meat. Numerous materials applied for CLN monitoring faced potential challenges like sluggish ion transport, non-uniform ion/molecule movement, and inadequate electrode surface binding. To overcome these shortcomings, herein we engineered bimetallic zeolitic imidazole framework (BM-ZIF) derived N-doped porous carbon embedded Co nanoparticles (CN-CoNPs), dispersed on conductive cellulose acetate-polyaniline (CP) electrospun nanofibers for sensitive electrochemical monitoring of CLN. Interestingly, the smartly designed CN-CoNPs wrapped CP (CN-CoNPs-CP) electrospun nanofibers offers rapid diffusion of CLN molecules to the sensing interface through amine and imine groups of CP, thus minimizing the inhomogeneous ion transportation and inadequate electrode surface binding. Additionally, to synchronize experiments, machine learning (ML) algorithms were applied to optimize, predict, and validate voltametric current responses. The ML-trained sensor demonstrated high selectivity, even amidst interfering substances, with notable sensitivity (4.7527 μA/μM/cm2), a broad linear range (0.002–8 μM), and a low limit of detection (1.14 nM). Furthermore, the electrode exhibited robust stability, retaining 98.07% of its initial current over a 12-h period. This ML-powered sensing approach was successfully employed to evaluate meat quality in terms of CLN level. To the best of our knowledge, this is the first study of using ML powered system for electrochemical sensing of CLN.

Highly catalytic sulfur-doped and bimetal-coordinated CoFe(CN)5NO nanoparticles coupled with PER/HCR amplification cascades for sensitive electrochemical aptamer luteinizing hormone assay

Sensitive monitoring of luteinizing hormone (LH), a glycoprotein that regulates the synthesis of regulatory steroid hormones, can facilitate the diagnosis of various reproductive diseases. In this work, a new and highly catalytic Sulfur-doped and bimetal-coordinated CoFe(CN)5NO (denoted as S–CoFe(CN)5NO) nanoparticles are synthesized. Such material is further used to construct high performance sensing interface and coupled with primer exchange reaction (PER) and hybridization chain reaction (HCR) amplification cascades for sensitive electrochemical aptamer-based LH assay. Target LH molecules bind aptamer sequences in DNA duplex probes to liberate ssDNA strands, which initiate subsequent PER/HCR amplification cascades for the capture of many ferrocene (Fc)-tagged DNAs on sensing interface. S–CoFe(CN)5NO subsequently leads to catalytic oxidation of these Fc tags for yielding substantially magnified currents for realizing ultrasensitive assay of LH with the detection limit of 0.69 pM in range from 5 pM to 10 nM. Owing to the high specificity of aptamer, such sensor has high selectivity and can achieve low levels of LH assay in diluted serum samples. With the successful demonstration for detecting trace LH, such sensor can be easily extended as a universal aptamer-based electrochemical sensing method for monitoring various target analytes in the biomedical and biological fields.

The construction of peroxidase-like Cu-BDC@FeMo6 for colorimetric detection of H2O2 and dopamine

Artificial mimic enzymes have attracted wide attention for their superior characteristics to natural enzymes in extensive applications of diagnosis and therapy. In this paper, a nanozyme Cu-BDC@FeMo6 was designed and fabricated by embedding polyoxometalate (NH4)3[FeMo6O18(OH)6]·6H2O (FeMo6) into a copper-based metal–organic framework (Cu-BDC). The integration of FeMo6 and Cu MOF based on the synergies of oxidability of FeMo6 and oxygen-driven reversible Cu+/Cu2+ enhanced the peroxidase mimicking activity, which accomplished the sensitive visual monitoring of H2O2 and dopamine (DA). The detection of H2O2 was driven by Cu-BDC@FeMo6 catalyzing the oxidation of TMB with colorimetric evolution to blue, and consecutive monitoring DA via the reverse process of reduction of ox-TMB was further achieved. The limit of detection (LOD) of H2O2 and DA were 10 μM and 2.27 μM, with excellent stability, and outstanding selectivity. The mechanism of the catalysis was further evaluated, and the generation of O2·- played a crucial role in the catalysis for oxidation. The logic gate design was constructed to illustrate the process and application. This work provides a feasible reference for the reasonable design of simulated enzyme in biosensor applications.

Metal Ion Responsive Luminescent Bio-Templated Co-Assemblies: Label-Free Detection of Multi-Metal Ions in Aqueous Media.

Recently, anionic bio-templates have emerged as promising platforms for designing dynamic and stimuli-responsive chromophoric assemblies capable of light harvesting in aqueous media thereby mimicking natural photosynthesis. Here, we present multi-metal ion-responsive luminescent co-assemblies between cationic pyrene-imidazolium amphiphile and anionic bio-templates (ATP, heparin, and DNA) in aqueous media. The anionic bio-templates enhance Förster resonance energy transfer (FRET) in the co-assemblies, with pyrene serving as an excellent donor for generating tunable multi-luminescent materials with embedded acceptor dyes. However, a significant loss in energy transfer towards acceptor dyes was observed in the presence of various metal ions, attributed to excimeric emission quenching facilitated by electron transfer between the pyrene chromophore and metal ions. Interestingly, detailed studies revealed that only ATP-based co-assemblies exhibited quenching phenomena in the presence of metal ions, contrasting with heparin and ctDNA co-assemblies. Additionally, label-free detection of multi-metal ions in aqueous environments, such as Fe2+, Fe3+, and Cu2+ ions, was successfully achieved with lower detection limits of 0.01 μM (3 ppb), 0.12 μM (30 ppb), and 0.58 μM (150 ppb) respectively. These co-assemblies hold significant promise for practical applications in environmental and biomedical sensing, enabling sensitive monitoring of metal ion concentrations.

Highly sensitive water pollution monitoring using colloid-processed organic photodetectors

Highly sensitive water pollution monitoring using colloid-processed organic photodetectors

Development and validation of a quantitative wipe sampling method to determine platinum contamination from antineoplastic drugs on surfaces in workplaces at Swedish hospitals.

Antineoplastic drugs (ADs) are frequently used pharmaceuticals in the healthcare, and healthcare workers can be occupationally exposed to ADs. Monitoring of surface contamination is a common way to assess occupational exposure to ADs. The objective was to develop and validate a sensitive and quantitative monitoring method to determine surface contaminations of Pt as a marker for Pt-containing ADs. The surface contaminations of Pt-containing ADs were monitored at four Swedish hospital workplaces. An analytical method was developed based on inductively coupled plasma mass spectrometry. The wipe sampling procedure was validated regarding different surface materials. The stability of collected wipe samples was investigated. Workplace surfaces were monitored by wipe sampling to determine contaminations of Pt-containing ADs. A wipe sampling and analytical method with a limit of detection of 0.1 pg Pt/cm2 was developed. Pt was detected in 67% of the wipe samples collected from four workplaces, and the concentrations ranged from <0.10 to 21100 pg/cm2. In 4% of samples, the detected surface contaminations of Pt in three hospital wards were above proposed hygienic guidance value (HGV) of Pt. In the hospital pharmacy, 9% of the detected surface contaminations of Pt were above lowest proposed HGV. A user-friendly, specific, and sensitive method for determination of surface contaminations of Pt from ADs in work environments was developed and validated. A large variation of contaminations was observed between detected surface contaminations of Pt in samples collected in wards, and it likely reflects differences in amounts handled and work practices between the wards.

New quasi-Co/Cu-MOF nanozyme coupled with entropy-driven DNA amplification cascades for highly sensitive electrochemical aptamer growth differentiation factor 15 assay

BackgroundThe monitoring of concentration variation of the newly developed growth differentiation factor 15 (GDF15) biomarker in human serum is of great significance for diagnosing cardiovascular diseases. Current methods for the detection of the GDF15 protein mainly are based on antibody-assisted immunoassays, which encounter the limitations in terms of sensitivity, complexity and costs. The development of simple and sensitive biosensors for GDF15 can therefore facilitate the diagnosis of cardiovascular diseases. ResultsA new bimetallic quasi-Cu/Co-MOF nanozyme with high catalytic performance for electrochemical reduction of H2O2 is synthesized via simple one-step precipitation and low-temperature calcination method. Such nanozymes are further employed as amplification tags and coupled with cyclic entropy-driven DNA signal enhancement strategies to construct ultrasensitive aptamer-based biosensor for detecting GDF15 in human serums. GDF15 molecules associate with two aptamers and release the ssDNA trigger sequences via target-binding induced displacement reaction. These ssDNAs subsequently initiate cyclic DNA-fueled strand displacement and catalytic hairpin assembly (CHA) reaction cascades for confining many quasi-Cu/Co-MOF nanozymes on sensor electrode, which yield drastically amplified H2O2 reduction current for detecting GDF15 down to 0.12 pg mL−1 with a dynamic range of 0.5 pg mL−1 to 20 ng mL−1. The electrochemical aptasensor also presents good reproducibility and selectivity and exhibits the capability to detect GDF15 in diluent serums. SignificanceOur aptamer-based GDF15 protein electrochemical assay clearly outperforms current existing antibody-based methods and the quasi-Cu/Co-MOF nanozyme/entropy-driven cascaded signal amplification means can be used as a universal strategy for sensitive monitoring of different biomolecular markers for diverse applications.

Monitoring of static and vibration responses of laminated composite materials using integrated carbon nanotube fibers

Carbon nanotube fibers or yarns (CNTYs) are lightweight, stiff, strong, electrically, and thermally conductive fiber-like materials that exhibit a piezoresistive response and could be integrated in glass-fiber/epoxy laminated composite materials to measure strain and to detect damage. Aiming at extending the scope of previous studies, this work is about the piezoresistive response of CNTY sensors integrated in composite laminates of industrial interest, accounting for interactions between the CNTY and the typical heterogeneous, anisotropic surrounding media, including the effects induced by the curing process of the composite matrix. This study reports experimental results on the mechanical response of laminated composite materials under quasi-static and vibration loading monitored using integrated CNTY sensors. A combination of CNTY sensor configurations and experimental setups were used to monitor the deformation and strains among the various layers of the laminated composites. As the laminated composites were mechanically loaded under quasi-static four-point bending, the CNTY sensors captured instantaneously the deformation as demonstrated by the change in their electrical resistance. Also, as the laminated composites were subjected to sinusoidal loading at specific frequencies, the integrated CNTY sensors were able to capture the loading cycles exactly including durations and peaks. Integrated sensing using CNTYs may offer a highly adaptive, practical, and sensitive structural monitoring method for a variety of applications.

A Ni-doped coral-like three-dimensional Mo2C nanorod for sensitive electrochemical monitoring of environmentally polluting nitrobenzene

This paper reports the synthesis of a Ni-doped coral-like three-dimensional Mo2C nanorod via the pyrolysis of polypyrrole (PPy)-loaded NiMoO4·xH2O nanorods for nitrobenzene (NB) detection. The incorporation of Ni species into Mo2C enhances dual-atom synergistic catalysis, while the inclusion of PPy as a preferred carbon source improves the composite's active area. The coral-like three-dimensional rod structure not only provides various types of sites for adsorbing reactants but also offers more channels for ion migration and electron transfer, promoting charge transfer and further enhancing its electrical conductivity. The resulting composite demonstrates a wide linear detection range (2.11–1053.61 μM), high sensitivity, low limit of detection (0.64 μM, S/N = 3), and excellent stability and anti-interference performance in NB detection. This novel composite preparation approach offers promising prospects for practical NB detection applications.

Adaptive optics retinal imaging in patients with usher syndrome.

To determine the structure of the cone photoreceptor mosaic in the macula in eyes with retinitis pigmentosa related to Usher syndrome using adaptive optics fundus (AO) imaging and to correlate these findings with those of the standard clinical diagnostics. Ten patients with a genetically confirmed retinitis pigmentosa in Usher syndrome due to biallelic variants in MYO7A or USH2A were enrolled in the study. All patients underwent a complete ophthalmological examination including best corrected visual acuity (BCVA), spectral-domain optical coherence tomography (SD-OCT) with fundus autofluorescence photography (FAF), full-field (ffERG) and multifocal electroretinography (mfERG) and Adaptive Optics Flood Illuminated Ophthalmoscopy (AO, rtx1™, Imagine Eyes, Orsay, France). The cone density was assessed centrally and at each 0.5 degree horizontally and vertically from 1-4 degree of eccentricity. In the AO images, photoreceptor cell death was visualized as a disruption of the cone mosaic and low cone density. In the early stage of the disease, cones were still visible in the fovea, whereas outside the fovea a loss of cones was recognizable by blurry, dark patches. The blurry patches corresponded to the parafoveal hypofluorescent ring in the FAF images and the beginning loss of the IS/OS line and external limiting membrane in the SD-OCT images. FfERGs were non-recordable in 7 patients and reduced in 3. The mfERG was reduced in all patients and correlated significantly (p <0.001) with the cone density. The kinetic visual field area, measured with III4e and I4e, did not correlate with the cone density. The structure of the photoreceptors in Usher syndrome patients were detectable by AO fundus imaging. The approach of using high-resolution technique to assess the photoreceptor structure complements the established clinical examinations and allows a more sensitive monitoring of early stages of retinitis pigmentosa in Usher syndrome.

Uniform monolayer of branched silver nanoplates-assembled nanoparticles for sensitive and reproducible SERS detection of harmful molecules

Surface-enhanced Raman scattering (SERS) technique can offer the fingerprint information of trace substances, and thus has wide potential applications in many fields. There is still a requirement to develop new and effective methods to construct high-performance SERS substrates. Here, a facile electrodeposition method is presented for fabricating large-scale uniform films assembled by branched silver (Ag) nanoplates. The morphology and structure of such film are highly uniform over a large area, which can ensure good spectral uniformity and reproducibility. There are dense sub-10 nm gaps between neighboring Ag nanoplates and between neighboring branches, forming plenty of hot spots. Therefore, the Ag nanoparticle monolayer exhibits high SERS activity along with excellent spectral repeatability. It is found that the limits of detection (LODs) towards rhodamine 6G and 4-aminothiophenol can reach 0.387 pM and 49.0 pM, respectively, showing high sensitivity of the designed SERS substrate. The enhancement factor of the prepared roughened Ag nanoparticle monolayer is computed to be as large as 2.37 × 108. Then, the highly roughened nanoparticle monolayer is used to detect cationic dye and fungicide (methylene blue, MB) and a synthetic cytokinin (6-benzylaminopurine, 6-BAP), and the corresponding LODs are determined down to 1.1 nM and 28.8 pM, respectively. Such LODs are much lower than the tolerance for MB and 6-BAP residues established by some authoritative regulations. Sensitive monitoring of 6-BAP residue on vegetables and fruits can also be achieved using such SERS substrate, indicating its promising application in environment monitoring and food safety supervision.

A Targeted, Bioinert LC-MS/MS Method for Sensitive, Comprehensive Analysis of Signaling Lipids.

Signaling lipids are key players in cellular processes. Despite their importance, no method currently allows their comprehensive monitoring in one analytical run. Challenges include a wide dynamic range, isomeric and isobaric species, and unwanted interaction along the separation path. Herein, we present a sensitive and robust targeted liquid chromatography-mass spectrometry (LC-MS/MS) approach to overcome these challenges, covering a broad panel of 17 different signaling lipid classes. It involves a simple one-phase sample extraction and lipid analysis using bioinert reversed-phase liquid chromatography coupled to targeted mass spectrometry. The workflow shows excellent sensitivity and repeatability in different biological matrices, enabling the sensitive and robust monitoring of 388 lipids in a single run of only 20 min. To benchmark our workflow, we characterized the human plasma signaling lipidome, quantifying 307 endogenous molecular lipid species. Furthermore, we investigated the signaling lipidome during platelet activation, identifying numerous regulations along important lipid signaling pathways. This highlights the potential of the presented method to investigate signaling lipids in complex biological systems, enabling unprecedentedly comprehensive analysis and direct insight into signaling pathways.

Deep-eutectic-solvent modulation of self-assembled multi-responsive films based on polyvinyl alcohol/cellulose nanocrystal and grape skin red for highly sensitive food monitoring

To enhance the mechanics performance, sensitivity and response range of multi-responsive photonic films, herein, a facile method for fabricating multi-responsive films is demonstrated using the evaporative self-assembly of a mixture of grape skin red (GSR), cellulose nanocrystal (CNC), polyvinyl alcohol (PVA) and deep eutectic solvent (DES). The prepared materials exhibited excellent thermal stability, strain properties, solvent resistance, ultraviolet (UV) resistance and antioxidant activity. Compared to a pure PVA film, the presence of GSR strengthened the antioxidant property of the film by 240.1 % and provided excellent UV barrier capability. The additional cross-linking of DES and CNC promoted more efficient phase fusion, yielding a film strain of 41.5 %. The addition of hydrophilic compound GSR, wetting and swelling due to the DES and the surface inhomogeneity of the films rendered the multi-responsive films high sensitivity, wide response range and multi-cyclic stability in environments with varying pH and humidity. A sample application showed that a PVA/CNC/DES film has the potential to differentiate between fresh, sub-fresh and fully spoiled shrimps. The above results help in designing intelligent thin film materials that integrate antioxidant properties, which help in monitoring the changes in food freshness and food packaging.

Engineering a far-red fluorescent probe for rapid detection of Hg(II) ions in both cells and zebrafish

Abnormal accumulation of mercury ions (Hg2+) in organisms can lead to severe central nervous system and other diseases. Therefore, the monitoring and detection of Hg2+ are of great significance for human health and environmental safety. Herein, we designed and synthesized a novel far-red to NIR emission fluorescent probe (Rho-Hg) based on rhodamine derivative as the fluorophore and thiospirolactone as the recognition site for turn-on detecting of Hg2+ in living cells and zebrafish. The probe Rho-Hg displayed superior sensitivity (detection limit = 17.5 nM), rapid response (<1 min), colorimetric change, high selectivity, and moderate pH stability. Leveraging this probe, we realized the real-time monitoring of Hg2+ in real samples, living cells and zebrafish. By fostering zebrafish embryos and larvae in Hg2+-containing nutrient solution, we noticed that Hg2+ was ingested into the zebrafish liver when zebrafish were grown up to 3 days old, and thus we successfully monitored the accumulation and changes of Hg2+ during zebrafish growth and development. Thus, the probe Rho-Hg could be a powerful tool for sensitive and real-time monitoring of Hg2+ in living systems.

Multistate Sensitivity Monitoring of Fusarium virguliforme to the SDHI Fungicides Fluopyram and Pydiflumetofen in the United States.

Sudden death syndrome (SDS), caused by Fusarium virguliforme, is an important yield-limiting disease of soybean (Glycine max). From 1996 to 2022, cumulative yield losses attributed to SDS in North America totaled over 25 million metric tons, which was valued at over US $7.8 billion. Seed treatments are widely used to manage SDS by reducing early season soybean root infection by F. virguliforme. Fluopyram (succinate dehydrogenase inhibitor [SDHI] - FRAC 7), a fungicide seed treatment for SDS management, has been registered for use on soybean in the United States since 2014. A baseline sensitivity study conducted in 2014 evaluated 130 F. virguliforme isolates collected from five states to fluopyram in a mycelial growth inhibition assay and reported a mean EC50 of 3.35 mg/liter. This baseline study provided the foundation for the objectives of this research: to detect any statistically significant change in fluopyram sensitivity over time and geographical regions within the United States and to investigate sensitivity to the fungicide pydiflumetofen. We repeated fluopyram sensitivity testing on a panel of 80 historical F. virguliforme isolates collected from 2006 to 2013 (76 of which were used in the baseline study) and conducted testing on 123 contemporary isolates collected from 2016 to 2022 from 11 states. This study estimated a mean absolute EC50 of 3.95 mg/liter in isolates collected from 2006 to 2013 and a mean absolute EC50 of 4.19 mg/liter in those collected in 2016 to 2022. There was no significant change in fluopyram sensitivity (P = 0.1) identified between the historical and contemporary isolates. A subset of 23 isolates, tested against pydiflumetofen under the same conditions, estimated an absolute mean EC50 of 0.11 mg/liter. Moderate correlation was detected between fluopyram and pydiflumetofen sensitivity estimates (R = 0.53; P < 0.001). These findings enable future fluopyram and pydiflumetofen resistance monitoring and inform current soybean SDS management strategies in a regional and national context.

A Novel Non-Contact Method for Monitoring the Acoustic Emission From Mixed Elastohydrodynamic Lubrication Contacts

Abstract Lubricated non-conformal contacts, such as between gear teeth, operate with high levels of mixed lubrication, where the amount of direct asperity contact depends on operating parameters that influence the film thickness. Understanding of the levels of surface interaction is key to optimizing component life, and there is considerable interest in sensitive monitoring methods such as Acoustic Emission (AE). Researchers have shown that AE can detect subtle changes in lubrication conditions, using sensors mounted directly on the rotating gears. However, the use of such sensors is complex and unsuitable for implementation in real gearboxes. The alternative, of using sensors placed on housings, is hampered by signal attenuation and noise. This paper presents a novel, non-contact stationary sensor, coupled by an oil film to the rotating gear, which is shown to be capable of detecting important changes in lubrication conditions with significantly higher consistency and precision than housing-mounted sensors, whilst avoiding the complexities of gear-mounted sensors.

Analysis of vibrational dynamics in cell-substrate interactions using nanopipette electrochemical sensors

Cell-substrate interaction plays a critical role in determining the mechanical status of living cell membrane. Changes of substrate surface properties can significantly alter the cell mechanical microenvironment, leading to mechanical changes of cell membrane. However, it is still difficult to accurately quantify the influence of the substrate surface properties on the mechanical status of living cell membrane without damage. This study addresses the challenge by using an electrochemical sensor made from an ultrasmall quartz nanopipette. With the tip diameter less than 100 nm, the nanopipette-based sensor achieves highly sensitive, noninvasive and label-free monitoring of the mechanical status of single living cells by collecting stable cyclic membrane oscillatory signals from continuous current versus time traces. The electrochemical signals collected from PC12 cells cultured on three different substrates (bare ITO (indium tin oxides) glass, hydroxyl modified ITO glass, amino modified ITO glass) indicate that the microenvironment more favorable for cell adhesion can increase the membrane stiffness. This work provides a label-free electrochemical approach to accurately quantify the mechanical status of single living cells in real-time, which may help to better understand the relationship between the cell membrane and the extra cellular matrix.

Identification and Quantification of Human Relaxin Proteins by Immunoaffinity-Mass Spectrometry.

The human relaxins belong to the Insulin/IGF/Relaxin superfamily of peptide hormones, and their physiological function is primarily associated with reproduction. In this study, we focused on a prostate tissue-specific relaxin RLN1 (REL1_HUMAN protein) and a broader tissue specificity RLN2 (REL2_HUMAN protein). Due to their structural similarity, REL1 and REL2 proteins were collectively named a 'human relaxin protein' in previous studies and were exclusively measured by immunoassays. We hypothesized that the highly selective and sensitive immunoaffinity-selected reaction monitoring (IA-SRM) assays would reveal the identity and abundance of the endogenous REL1 and REL2 in biological samples and facilitate the evaluation of these proteins for diagnostic applications. High levels of RLN1 and RLN2 transcripts were found in prostate and breast cancer cell lines by RT-PCR. However, no endogenous prorelaxin-1 or mature REL1 were detected by IA-SRM in cell lines, seminal plasma, or blood serum. The IA-SRM assay of REL2 demonstrated its undetectable levels (<9.4 pg/mL) in healthy control female and male sera and relatively high levels of REL2 in maternal sera across different gestational weeks (median 331 pg/mL; N = 120). IA-SRM assays uncovered potential cross-reactivity and nonspecific binding for relaxin immunoassays. The developed IA-SRM assays will facilitate the investigation of the physiological and pathological roles of REL1 and REL2 proteins.