MALDI-MS-Based Quantitative Analysis for Ketone Containing Homoserine Lactones in Pseudomonas aeruginosa

Corrosive Pseudomonas aeruginosa detection by measuring pyocyanin with a lab-on-fiber optical surface plasmon resonance biosensor in aquatic environments

Oceanic facilities and equipment corrosion present considerable economic and safety concerns, predominantly due to microbial corrosion. Early detection of corrosive microbes is pivotal for effective monitoring and prevention. Yet, traditional detection methods often lack specificity, require extensive processing time, and yield inaccurate results. Hence, the need for an efficient real-time corrosive microbe monitoring technology is evident. Pseudomonas aeruginosa, a widely distributed microorganism in aquatic environments, utilizes its production of quinone-like compounds, specifically pyocyanin (PYO), to corrode metals. Here, we report a novel fiber optic surface plasmon resonance (SPR) sensor modified by the C-terminal of BrlR protein (BrlR-C), which is a specific receptor of PYO molecule, to detect P. aeruginosa in aquatic environments. The results showed that the sensor had a good ability to recognize PYO in the concentration range of 0-1 μg/mL, and showed excellent sensing performance in real-time monitoring the growth status of P. aeruginosa. With a strong selectivity of PYO, the sensor could clearly detect P. aeruginosa against other bacteria in seawater environment, and exhibited excellent anti-interference ability against variations in pH, temperature and pressure and other interfering substances. This study provides a useful tool for monitoring corrosive P. aeruginosa biofilm in aquatic environments, which is a first of its kind example that serves as a laboratory model for the application of fiber optic technology in real-world scenarios to monitoring biofilms in microbial corrosion and biofouling.

Effect of thermal hydrolysis pretreatment on the occurrence of N-acyl homoserine lactone during anaerobic digestion of waste activated sludge

This study sought to investigate the relationship between N-acyl homoserine lactones (AHLs) and methanogenic microorganisms, focusing on endogenous AHLs in the anaerobic digestion (AD) process. By analyzing waste activated sludge (WAS) samples, we examine the changes in microbial communities and the AHLs-methanogens connection. The Mantel test and Spearman correlation analysis were conducted to gain novel insights into the AD process. Our findings demonstrate that thermal hydrolysis pretreatment (THP) modifies AHL concentrations during AD, thereby enhancing methanogenic bacteria activity and regulating social interactions among microorganisms. In the Eth group (AD of THP samples labeled Eth), Methanobacterium and Methanosarcina accounted for over 80% of the methanogenic bacteria, with correlation coefficients greater than 0.5 between these bacterial taxa and N-hexyl-l-homoserine lactone (C6-HSL) and N-enanthyl-l-homoserine lactone (C7-HSL).

Comprehensive chiral GC-MS/MS and LC-MS/MS methods for identification and determination of N-acyl homoserine lactones

N-acyl homoserine lactones (N-HLs) are signaling molecules synthesized by gram-negative bacteria to communicate in a process called quorum sensing. Most reported methods for the analysis of N-HLs, which are chiral molecules, do not distinguish between enantiomers. Typical examples include biosensors, liquid chromatography with UV detection, gas chromatography coupled with a mass spectrometer (GC-MS) and liquid chromatography coupled with mass spectrometer (LC-MS). Recently, the production of both D,L-N-HLs have been reported in Vibrio fischeri and Burkholderia cepacia. Concentrations of the D-N-HLs were found at the limit of quantification for the employed method. Therefore, for further studies of the role of the D-N-HLs in bacterial physiology, more sensitive, reliable, and selective analytical methods are necessary. In this work, such comprehensive chiral analytical methods for the identification and determination of 18 N-HLs using solid phase extraction followed by GC-MS/MS and LC-MS/MS analyses were developed. Extraction recoveries for the more hydrophilic C4 N-HLs were <10% of all other N-HLs, thus offering a possible explanation as to their lack of detection in previous studies. The chiral separations of all 18 N-HLs derivatives were accomplished by the complementary GC-MS/MS and LC-MS/MS methods. The limit of detection for LC-MS/MS method was as low as 1 ppb. The limit of detection for the GC-MS/MS method was found to be one to three orders of magnitude higher than the LC-MS/MS method. Due to the high extraction recovery and a preconcentration factor of 100, concentrations as low as 10 ppt can be detected by LC-MS/MS in biological samples. The LC-MS/MS approach provided greater enantioselectivity for the larger, more hydrophobic N-HLs while GC-MS/MS provided better enantioselectivity for the smaller N-HLs.

Protocol: a simple method for biosensor visualization of bacterial quorum sensing and quorum quenching interaction on Medicago roots

BACKGROUND

Defining interactions of bacteria in the rhizosphere (encompassing the area near and on the plant root) is important to understand how they affect plant health. Some rhizosphere bacteria, including plant growth promoting rhizobacteria (PGPR) engage in the intraspecies communication known as quorum sensing (QS). Many species of Gram-negative bacteria use extracellular autoinducer signal molecules called N-acyl homoserine lactones (AHLs) for QS. Other rhizobacteria species, including PGPRs, can interfere with or disrupt QS through quorum quenching (QQ). Current AHL biosensor assays used for screening and identifying QS and QQ bacteria interactions fail to account for the role of the plant root.

METHODS

Medicago spp. seedlings germinated on Lullien agar were transferred to soft-agar plates containing the broad-range AHL biosensor Agrobacterium tumefaciens KYC55 and X-gal substrate. Cultures of QS and QQ bacteria as well as pure AHLs and a QQ enzyme were applied to the plant roots and incubated for 3 days.

RESULTS

We show that this expanded use of an AHL biosensor successfully allowed for visualization of QS/QQ interactions localized at the plant root. KYC55 detected pure AHLs as well as AHLs from live bacteria cultures grown directly on the media. We also showed clear detection of QQ interactions occurring in the presence of the plant root.

CONCLUSIONS

Our novel tri-trophic system using an AHL biosensor is useful to study QS interspecies interactions in the rhizosphere.

Characterization of Distinct Biofilm Cell Subpopulations and Implications in Quorum Sensing and Antibiotic Resistance

Bacteria change phenotypically in response to their environment. Free swimming cells transition to biofilm communities that promote cellular cooperativity and resistance to stressors and antibiotics. We uncovered three subpopulations of cells with diverse phenotypes from a single-species Pseudomonas aeruginosa PA14 biofilm, and used a series of steps to isolate, characterize, and map these cell subpopulations in a biofilm. The subpopulations were distinguishable by size and morphology using dynamic light scattering (DLS) and scanning electron microscopy (SEM). Additionally, growth and dispersal of biofilms originating from each cell subpopulation exhibited contrasting responses to antibiotic challenge. Cell subpopulation surface charges were distinctly different, which led us to examine the ionizable surface molecules associated with each subpopulation using mass spectrometry. Matrix assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis of cell subpopulations revealed ions unique to each subpopulation of cells that significantly co-localized with ions associated with quorum sensing. Transcript levels of algR, lasR, and rhlI in subpopulations isolated from biofilms differed from levels in planktonic stationary and mid-log cell subpopulations. These studies provide insight into diverse phenotypes, morphologies, and biochemistries of PA14 cell subpopulations for potential applications in combating bacterial pathogenesis, with medical, industrial, and environmental complications.

Rapid and Automatic Annotation of Multiple On-Tissue Chemical Modifications in Mass Spectrometry Imaging with Metaspace

On-tissue chemical derivatization is a valuable tool for expanding compound coverage in untargeted metabolomic studies with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Applying multiple derivatization agents in parallel increases metabolite coverage even further but results in large and more complex datasets that can be challenging to analyze. In this work, we present a pipeline to provide rigorous annotations for on-tissue derivatized MSI data using Metaspace. To test and validate the pipeline, maize roots were used as a model system to obtain MSI datasets after chemical derivatization with four different reagents, Girard's T and P for carbonyl groups, coniferyl aldehyde for primary amines, and 2-picolylamine for carboxylic acids. Using this pipeline helped us annotate 631 unique metabolites from the CornCyc/BraChem database compared to 256 in the underivatized dataset, yet, at the same time, shortening the processing time compared to manual processing and providing robust and systematic scoring and annotation. We have also developed a method to remove false derivatized annotations, which can clean 5-25% of false derivatized annotations from the derivatized data, depending on the reagent. Taken together, our pipeline facilitates the use of broadly targeted spatial metabolomics using multiple derivatization reagents.

Quorum quenching enzymes and their effects on virulence, biofilm, and microbiomes: a review of recent advances

INTRODUCTION

Numerous bacterial behaviors are regulated by a cell-density dependent mechanism known as Quorum Sensing (QS). QS relies on communication between bacterial cells using diffusible signaling molecules known as autoinducers. QS regulates physiological processes such as metabolism, virulence, and biofilm formation. Quorum Quenching (QQ) is the inhibition of QS using chemical or enzymatic means to counteract behaviors regulated by QS.

AREAS COVERED

We examine the main, diverse QS mechanisms present in bacterial species, with a special emphasis on AHL-mediated QS. We also discuss key in vitro and in vivo systems in which interference in QS was investigated. Additionally, we highlight promising developments, such as the substrate preference of the used enzymatic quencher, in the application of interference in QS to counter bacterial virulence.

EXPERT OPINION

Enabled via the recent isolation of highly stable quorum quenching enzymes and/or molecular engineering efforts, the effects of the interference in QS were recently evaluated outside of the traditional model of single species culture. Signal disruption in complex microbial communities was shown to result in the disruption of complex microbial behaviors, and changes in population structures. These new findings, and future studies, may result in significant changes in the traditional views about QS.

An eco-friendly sensor based on CQD@MIPs for detection of N-acylated homoserine lactones and its 3D printing applications

N-acylated homoserine lactones (AHLs), a class of auto-inducers produced by Gram-negative bacteria, are typical signaling molecules in quorum sensing (QS) systems. Importantly, AHLs play a key role in determining the virulence of foodborne pathogens and reflect the activity of spoilage bacteria. In this study, an eco-friendly fluorescence-sensing platform for the rapid and sensitive detection of AHLs was developed and characterized. Molecularly imprinted polymers embedded with yellow-emitting carbon quantum dots (CQDs) were obtained via the sol-gel process using furanone as an alternative template molecule, and long-wave-emitting CQDs with excellent optical properties were used as signal conversion materials. After template elution, the blotting cavities on the surface of the CQD@MIPs (molecularly imprinted polymers) were able to selectively recognize AHLs, demonstrating a stronger fluorescence response compared with the corresponding CQD@NIPs (non-imprinted polymers). Under optimal test conditions, a good linear relationship between the concentration of analyte and the relative fluorescence intensity of the CQD@MIPs was observed. The linear detection range was 0-2.0 μM, and the limit of detection (LOD) was 0.067 μM. Importantly, the proposed sensing platform functioned as an optical detection strategy that responded quickly (2 min) to AHLs. Additionally, this sensing platform was applied to the analysis of AHLs in bacterial supernatant samples with satisfactory results. More interestingly, the 3D-printing CQD@MIPs were tentative explored in this work, which was personalized and portable, has an advantage of point of care testing (POCT) detection in the future. Based on these results, this detection strategy has demonstrated substantial potential for application in and the field of food safety.

The role of quorum sensing in granular sludge: Impact and future application: A review

Quorum sensing (QS) is a process widely exist in bacteria, which refers to the cell-cell communication through secretion and sensing the specific chemical signal molecules named autoinducers. This review demonstrated recent research progresses on the specific impacts of signal molecules in the granular sludge reactors, such corresponding exogenous strategies contained the addition of QS signal molecules, QS-related enzymes and bacteria associated with QS process. Accordingly, the correlation between QS signaling molecule content and sludge granulation (including the formation and stability) was assumed, the comprehensive conclusion elucidated that some QS signals (acyl-homoserine lactone and Autoinducer 2) can accelerate the growth of particle diameter, the production of extracellular polymeric substance (EPS), microbial adhesion and change the microbiome structure. But diffusable signal factor (DSF) acted as a significant disincentive to the formation and stability of GS. As a result, it deserved serious attention on the value and role of QS signals in the GS. This review attempts to illuminate the potential method for addressing the main bottleneck: to accelerate the formation of granules and keep the high stability of GS for a long-term reactor. Therefore, review discussed the possible trends of GS: QS and intercellular/intracellular signaling which can lay a theoretical foundation for mechanism of GS formation and stability, would be of practical significance for further application in the future.

MALDI-TOF MS-based total serum protein fingerprinting for liver cancer diagnosis

Serum is one of the most commonly used samples in many studies to identify protein biomarkers to diagnose cancer. Although conventional enzyme-linked immunosorbent assay (ELISA) or liquid chromatography-mass spectrometry (LC-MS)-based methods have been applied as clinical tools for diagnosing cancer, there have been troublesome problems, such as inferior multiplexing capabilities, high development costs and long turnaround times, which are inappropriate for high-throughput analytical platforms. Here, we developed a simple and robust cancer diagnostic method using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based total serum protein fingerprinting. First, serum samples were simply diluted with distilled water and subsequently spotted onto a MALDI plate without prior chromatographic purification or separation. The sample preparation method was enough to collect reproducible total serum protein fingerprints and would be highly advantageous for high-throughput assay. Each of the integrated main spectrum profiles (MSPs), which are representative of liver cancer patients (n = 40) or healthy controls (n = 80), was automatically generated by the MALDI Biotyper 3 software. The reliability of the integrated MSPs was successfully evaluated in comparison with a blind test set (n = 31), which consisted of 13 liver cancer patients and 18 healthy controls. Additionally, our partial least squares discriminant analysis (PLS-DA) demonstrated a statistically significant difference in MALDI-TOF MS-based total serum protein fingerprints between liver cancer patients and healthy controls. Taken together, this work suggests that this method may be an effective high-throughput platform technology for various cancer diagnoses and disease evaluations.

Roles of quorum sensing in biological wastewater treatment: A critical review

Quorum sensing (QS) and quorum quenching (QQ) are increasingly reported in biological wastewater treatment processes because of their inherent roles in biofilm development, bacterial aggregation, granulation, colonization, and biotransformation of pollutants. As such, the fundamentals and ubiquitous nature of QS bacteria are critical for fully understanding the process of the wastewater treatment system. In this article, the details of QS-based strategies related to community behaviors and phenotypes in wastewater treatment systems were reviewed. The molecular aspects and coexistence of QS and QQ bacteria were also mentioned, which provide evidence that future wastewater treatment will indispensably rely on QS-based strategies. In addition, recent attempts focusing on the use of QQ for biofilm or biofouling control were also summarized. Nevertheless, there are still several challenges and knowledge gaps that warrant future targeted research on the ecological niche, abundance, and community of QS- and QQ-bacteria in environmental settings or engineered systems.

Metabolic Phenotyping and Strain Characterisation of Pseudomonas aeruginosa Isolates from Cystic Fibrosis Patients Using Rapid Evaporative Ionisation Mass Spectrometry

Rapid evaporative ionisation mass spectrometry (REIMS) is a novel technique for the real-time analysis of biological material. It works by conducting an electrical current through a sample, causing it to rapidly heat and evaporate, with the analyte containing vapour channelled to a mass spectrometer. It was used to characterise the metabolome of 45 Pseudomonas aeruginosa (P. aeruginosa) isolates from cystic fibrosis (CF) patients and compared to 80 non-CF P. aeruginosa. Phospholipids gave the highest signal intensity; 17 rhamnolipids and 18 quorum sensing molecules were detected, demonstrating that REIMS has potential for the study of virulence-related metabolites. P. aeruginosa isolates obtained from respiratory samples showed a higher diversity, which was attributed to the chronic nature of most respiratory infections. The analytical sensitivity of REIMS allowed the detection of a metabolome that could be used to classify individual P. aeruginosa isolates after repeated culturing with 81% accuracy, and an average 83% concordance with multilocus sequence typing. This study underpins the capacities of REIMS as a tool with clinical applications, such as metabolic phenotyping of the important CF pathogen P. aeruginosa, and highlights the potential of metabolic fingerprinting for fine scale characterisation at a sub-species level.

Miniaturized dispersive liquid-liquid microextraction and MALDI MS using ionic liquid matrices for the detection of bacterial communication molecules and virulence factors

The identification and quantification of molecules involved in bacterial communication are major prerequisites for the understanding of interspecies interactions at the molecular level. We developed a procedure allowing the determination of 2-heptyl-4(1H)-quinolone (HHQ) and 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) and the virulence factor pyocyanin (PYO) formed by the Gram-negative bacterium Pseudomonas aeruginosa. The method is based on dispersive liquid-liquid microextraction from small supernatant volumes (below 10 μL) followed by quantitative matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). The use of ionic liquid matrix led to a lowered limit of detection for pyocyanin and, due to suppression of matrix background signals, easy to interpret mass spectra compared to crystalline matrices. Using an isotope-labeled pyocyanin standard synthesized in small-scale synthesis, quantitative analysis spanning approximately one order of magnitude (0.5 to 250 fmol) was feasible. The method was successfully applied to the detection of the signaling molecules PQS and HHQ in cultures of P. aeruginosa strains isolated from sputum of cystic fibrosis patients and allowed a highly sensitive quantification of PYO from these cultures. Hence, the developed method bears the potential to be used for screening purposes in clinical settings and will help to decipher the molecular basis of bacterial communication. Graphical abstract Ionic liquid matrices for the detection and quantification of the toxin pyocyanin and other signaling molecules from P. aeruginosa by MALDI MS.

Identification and Quantification of N-Acyl Homoserine Lactones Involved in Bacterial Communication by Small-Scale Synthesis of Internal Standards and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

N-acyl homoserine lactones (AHL) are small signal molecules involved in the quorum sensing of many gram-negative bacteria, and play an important role in biofilm formation and pathogenesis. Present analytical methods for identification and quantification of AHL require time-consuming sample preparation steps and are hampered by the lack of appropriate standards. By aiming at a fast and straightforward method for AHL analytics, we investigated the applicability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Suitable MALDI matrices, including crystalline and ionic liquid matrices, were tested and the fragmentation of different AHL in collision-induced dissociation MS/MS was studied, providing information about characteristic marker fragments ions. Employing small-scale synthesis protocols, we established a versatile and cost-efficient procedure for fast generation of isotope-labeled AHL standards, which can be used without extensive purification and yielded accurate standard curves. Quantitative analysis was possible in the low pico-molar range, with lower limits of quantification reaching from 1 to 5 pmol for different AHL. The developed methodology was successfully applied in a quantitative MALDI MS analysis of low-volume culture supernatants of Pseudomonas aeruginosa. Graphical abstract ᅟ.

Porous monolith microfluidics for bacterial cell-to-cell communication assays

Genetically engineered bacteria can be used for a wide range of applications, from monitoring environmental toxins to studying complex communication networks in the human digestive system. Although great strides have been made in studying single strains of bacteria in well-controlled microfluidic environments, there remains a need for tools to reliably control and measure communication between multiple discrete bacterial populations. Stable long-term experiments (e.g., days) with controlled population sizes and regulated input (e.g., concentration) and output measurements can reveal fundamental limits of cell-to-cell communication. In this work, we developed a microfluidic platform that utilizes a porous monolith to reliably and stably partition adjacent strains of bacteria while allowing molecular communication between them for several days. We measured small molecule production by the bacterial populations in response to stimuli using analytical chemistry methods and measured fluorescent output. The results are compared with communication and diffusion delay models. This porous monolith microfluidic system enables bacterial cell-to-cell communication assays with dynamic control of inputs, relatively long-term experimentation with no cross contamination, and stable bacterial population size. This system can serve as a valuable tool in understanding bacterial communication and improving biosensor design capabilities.

Identification and Quantification of Acylated Homoserine Lactones in Shewanella baltica, the Specific Spoilage Organism of Pseudosciaena crocea, by Ultrahigh-Performance Liquid Chromatography Coupled to Triple Quadrupole Mass Spectrometry

Bacteria communicate with one another using chemical signal molecules called autoinducers, and the most prevalent autoinducers used by Gram-negative bacteria are N-acylated homoserine lactones (AHLs). However, AHLs are hardly detected in Shewanella baltica, the specific spoilage organism of Pseudosciaena crocea. In this study, we applied ultrahigh-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry to determine AHLs. This method enabled the quantification of up to 11 AHLs within 5.6 min with excellent sensitivity (ng/mL level) and linearity (r² > 0.99), which further detected 9 AHLs produced by S. baltica. Furthermore, by using a biofilm formation assay and statistical analysis, the biofilm-inducing activity of AHL in S. baltica was first revealed. Our results elucidated the physiological role of AHL in S. baltica and provided a satisfactory method to detect AHLs and a statistical model to predict food spoilage properties.

Simultaneous Quantification of Serum Nonesterified and Esterified Fatty Acids as Potential Biomarkers to Differentiate Benign Lung Diseases from Lung Cancer

In this study, we have employed graphene oxide as a matrix to simultaneously and directly quantify serum nonesterified and esterified fatty acids (FAs) using matrix-assisted laser/desorption ionization-Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS). Twelve serum nonesterified FAs combined with their individual esterified FAs (i.e., C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:2, C20:3, C20:4, C20:5, C22:5, and C22:6) were quantified based on their calibration curves with the correlation coefficients of >0.99, along with the analytical time of <1 min each sample. As a result, serum levels of twelve total FAs (TFAs) in 1440 serum samples from 487 healthy controls (HCs), 479 patients with benign lung diseases (BLDs) and 474 patients with lung cancer (LC) were determined. Statistical analysis indicated that significantly increased levels of C16:0, C16:1, C18:0, C18:1, C18:3, C20:3, and C22:6 and decreased levels of C20:5 were observed in LC patients compared with BLDs. Receiver operating characteristic (ROC) analysis revealed that panel a (C18:2, C20:3, C20:4, C20:5, C22:5, and C22:6), panel b (C18:0, C20:4, C20:5, and C22:6), and panel c (C16:1, C18:0, C18:1, C20:3, and C22:6) have exhibited good diagnostic ability to differentiate BLDs from LC relative to clinical uses of tumor markers (CEA and Cyfra 21-1).

Acyl-homoserine lactone-based quorum sensing and quorum quenching hold promise to determine the performance of biological wastewater treatments: An overview

Quorum sensing (QS) is a communication process between cells, in which bacteria secrete and sense the specific chemicals, and regulate gene expression in response to population density. Quorum quenching (QQ) blocks QS system, and inhibits gene expression mediating bacterial behaviors. Given the extensive research of acyl-homoserine lactone (AHL) signals, existences and effects of AHL-based QS and QQ in biological wastewater treatments are being subject to high concern. This review summarizes AHL structure, synthesis mode, degradation mechanisms, analytical methods, environmental factors, AHL-based QS and QQ mechanisms. The existences and roles of AHL-based QS and QQ in biomembrane processes, activated sludge processes and membrane bioreactors are summarized and discussed, and corresponding exogenous regulation strategy by selective enhancement of AHL-based QS or QQ coexisting in biological wastewater treatments is suggested. Such strategies including the addition of AHL signals, AHL-producing bacteria as well as quorum quenching enzyme or bacteria can effectively improve wastewater treatment performance without killing or limiting bacterial survival and growth. This review will present the theoretical and practical cognition for bacterial AHL-based QS and QQ, suggest the feasibility of exogenous regulation strategies in biological wastewater treatments, and provide useful information to scientists and engineers who work in this field.

A MALDI-MS-based quantitative analytical method for endogenous estrone in human breast cancer cells

The level of endogenous estrone, one of the three major naturally occurring estrogens, has a significant correlation with the incidence of post-menopausal breast cancer. However, it is challenging to quantitatively monitor it owing to its low abundance. Here, we develop a robust and highly sensitive mass-assisted laser desorption/ionization mass spectrometry (MALDI-MS)-based quantitative platform to identify the absolute quantities of endogenous estrones in a variety of clinical specimens. The one-step modification of endogenous estrone provided good linearity (R(2) > 0.99) and significantly increased the sensitivity of the platform (limit of quantitation: 11 fmol). In addition, we could identify the absolute amount of endogenous estrones in cells of the breast cancer cell line MCF-7 (34 fmol/10(6) cells) by using a deuterated estrone as an internal standard. Finally, by applying the MALDI-MS-based quantitative method to endogenous estrones, we successfully monitored changes in the metabolic expression level of estrones (17.7 fmol/10(6) letrozole-treated cells) in MCF-7 cells resulting from treatment with an aromatase inhibitor. Taken together, these results suggest that this MALDI-MS-based quantitative approach may be a general method for the targeted metabolomics of ketone-containing metabolites, which can reflect clinical conditions and pathogenic mechanisms.

Magnetic molecularly imprinted polymer nanoparticles based electrochemical sensor for the measurement of Gram-negative bacterial quorum signaling molecules (N-acyl-homoserine-lactones)

We have developed a novel and economical electrochemical sensor to measure Gram-negative bacterial quorum signaling molecules (AHLs) using magnetic nanoparticles and molecularly imprinted polymer (MIP) technology. Magnetic molecularly imprinted polymers (MMIPs) capable of selectively absorbing AHLs were successfully synthesized by surface polymerization. The particles were deposited onto a magnetic carbon paste electrode (MGCE) surface, and characterized by electrochemical measurements. Differential Pulse Voltammetry (DPV) was utilized to record the oxidative current signal that is characteristic of AHL. The detection limit of this assay was determined to be 8×10(-10)molL(-1) with a linear detection range of 2.5×10(-9)molL(-1) to 1.0×10(-7)molL(-1). This Fe3O4@SiO2-MIP-based electrochemical sensor is a valuable new tool that allows quantitative measurement of Gram-negative bacterial quorum signaling molecules. It has potential applications in the fields of clinical diagnosis or food analysis with real-time detection capability, high specificity, excellent reproducibility, and good stability.