Development of an accurate and sensitive method for lactate analysis in exhaled breath condensate by LC MS/MS

Rapid Measurement of Lactate in the Exhaled Breath Condensate: Biosensor Optimization and In-Human Proof of Concept

Lactate concentration is of increasing interest as a diagnostic for sepsis, septic shock, and trauma. Compared with the traditional blood sample media, the exhaled breath condensate (EBC) has the advantages of non-invasiveness and higher user acceptance. An amperometric biosensor was developed and its application in EBC lactate detection was investigated in this paper. The sensor was modified with PEDOT:PSS-PB, and two different lactate oxidases (LODs). A rotating disk electrode and Koutecky-Levich analysis were applied for the kinetics analysis and gel optimization. The optimized gel formulation was then tested on disposable screen-printed sensors. The disposable sensors exhibited good performance and presented a high stability for both LOD modifications. Finally, human EBC analysis was conducted from a healthy subject at rest and after 30 min of intense aerobic cycling exercise. The sensor coulometric measurements showed good agreement with fluorometric and triple quadrupole liquid chromatography mass spectrometry reference methods. The EBC lactate concentration increased from 22.5 μM (at rest) to 28.0 μM (after 30 min of cycling) and dropped back to 5.3 μM after 60 min of rest.

A Selective Fluorescent l-Lactate Biosensor Based on an l-Lactate-Specific Transcription Regulator and Förster Resonance Energy Transfer

Selective detection of l-lactate levels in foods, clinical, and bacterial fermentation samples has drawn intensive attention. Many fluorescent biosensors based on non-stereoselective recognition elements have been developed for lactate detection. Herein, the allosteric transcription factor STLldR from Salmonella enterica serovar Typhimurium LT2 was identified to be stereo-selectively respond to l-lactate. Then, STLldR was combined with Förster resonance energy transfer (FRET) to construct a fluorescent l-lactate biosensor FILLac. FILLac was further optimized by truncating the N- and C-terminal amino acids of STLldR between cyan and yellow fluorescent proteins. The optimized biosensor FILLac_10N0C exhibited a maximum emission ratio change (ΔR_max) of 33.47 ± 1.91%, an apparent dissociation constant (K_d) of 6.33 ± 0.79 μM, and a limit of detection of 0.68 μM. FILLac_10N0C was applied in 96-well microplates to detect l-lactate in bacterial fermentation samples and commercial foods such as Jiaosu and yogurt. The quantitation results of FILLac_10N0C exhibited good agreement with that of a commercial l-lactate biosensor SBA-40D bioanalyzer. Thus, the biosensor FILLac_10N0C compatible with high-throughput detection may be a potential choice for quantitation of l-lactate in different biological samples.

Dual-Color Fluorescent Hydrogel Microspheres Combined with Smartphones for Visual Detection of Lactate

Since it is difficult for human eyes to distinguish between two identical colors with only <15% variation in brightness, mono-color fluorescent hydrogel microspheres have some limitations in the detection of lactate. Herein, we prepared novel dual-color fluorescent hydrogel microspheres, which can achieve hue transformation. Microspheres were prepared by introducing a fluorescent nanoparticle as the reference signal while CdTe QDs were used as the response signal. We used smartphones with image processing software to collect and analyze data. In this way, the signal of lactate was converted to RGB (red, green, and blue) values, which can be quantitatively read. Within 10 to 1500 μM, the R/G values of the microspheres had a linear relationship with the logarithm of the lactate concentration. Moreover, color cards for lactate detection were prepared, from which the color change and concentration of lactate could be easily read by the naked eye. It is worth mentioning that this method was successfully applied to screen patients with hyperlactatemia.

Mosquito Attractants

Vector control and personal protection against anthropophilic mosquitoes mainly rely on the use of insecticides and repellents. The search for mosquito-attractive semiochemicals has been the subject of intense studies for decades, and new compounds or odor blends are regularly proposed as lures for odor-baited traps. We present a comprehensive and up-to-date review of all the studies that have evaluated the attractiveness of volatiles to mosquitoes, including individual chemical compounds, synthetic blends of compounds, or natural host or plant odors. A total of 388 studies were analysed, and our survey highlights the existence of 105 attractants (77 volatile compounds, 17 organism odors, and 11 synthetic blends) that have been proved effective in attracting one or several mosquito species. The exhaustive list of these attractants is presented in various tables, while the most common mosquito attractants - for which effective attractiveness has been demonstrated in numerous studies - are discussed throughout the text. The increasing knowledge on compounds attractive to mosquitoes may now serve as the basis for complementary vector control strategies, such as those involving lure-and-kill traps, or the development of mass trapping. This review also points out the necessity of further improving the search for new volatile attractants, such as new compound blends in specific ratios, considering that mosquito attraction to odors may vary over the life of the mosquito or among species. Finally, the use of mosquito attractants will undoubtedly have an increasingly important role to play in future integrated vector management programs.

Screening of Potential Stress Biomarkers in Sweat Associated with Sports Training

BACKGROUND

Intense and continuous physical training in sports is related with psychological and physiological stress, affecting the health and well-being of athletes. The development of non-invasive sampling methodologies is essential to consider sweat as a potential biological fluid for stress biomarker assessment. In the current work, the identification in sweat samples of potential molecules that may be used as stress biomarkers was pursued.

METHODS

A sweat pool sample from football players after a 90-min intense training game was studied.

RESULTS

An analysis method using liquid chromatography with detection by tandem mass spectrometry (LC-MSMS) to attain a screening profile of sweat composition is presented. The major focus was on neurotransmitters (e.g. monoamines and metabolites) and other biological molecules related with physical training, such as precursors of biogenic amines (phenylaniline, tyrosine, etc.).

CONCLUSIONS

This study allowed the identification of small biomolecules, neurotransmitters and other related molecules in sweat that are potentially associated with stress conditions. The developed methodology intends to contribute to the assessment and study of physical and psychological stress biomarkers related with intense sports using non-invasive methods.

The effect of blood lactate and NT-proBNP predict the survival in patients with invasive mechanical ventilation

Background

Respiratory failure is one of the most common critical diseases. It has already been reported that invasive mechanical ventilation (IMV) should be used to treat respiratory failure. The present study aims to evaluate the prognostic value of blood lactate and NT-proBNP in patients with IMV.

Methods

We retrospectively included 353 patients who were hospitalized in the emergency department of Shanghai Sixth People’s Hospital from 2016 to 2019. All patients had IMV. R&D Human Premixed Multi-Analyte Kit detected the expression of various inflammatory factors in serum. Receiver operating characteristic (ROC) curve analysis, survival analysis, and multivariate cox proportional hazards analysis were implemented as statistical analysis methods.

Results

The mean duration of hospitalization was 25.5±20.6 days. Twenty-four men and 41 women died. Compared with the survivors, the nonsurvivors were older, had different types of diagnosis, longer ventilation time, and shorter survival time (P<0.05). Also, the expression levels of PCT, NT-proBNP, lactate in 12 h and lactate in 24 h in the nonsurvivors were significantly higher than those in the survivor group (P<0.05). There was a significant correlation between these parameters and ventilation times (P<0.001). The results showed that age, NT-proBNP, and lactate were independent predictors of survival rate. ROC analysis showed that the cut-off values of age, NT-proBNP and lactate were 61.5 years, 230.5 pg/mL and 3.7 mmol/L, respectively. Patients aged ≥61.5 years or NT-proBNP ≥230.5 pg/mL or lactate ≥3.7 mmol/L had a worse prognosis. Therefore, patients with three parameters higher than cut-off value had the lowest survival rate, while patients with three parameters lower than cut-off value had the best survival rate.

Conclusions

Blood lactate and NT-proBNP may be used as biomarkers to predict the prognosis of patients undergoing IMV.

UHPLC-QTOF/MS-based metabolomics investigation for the protective mechanism of Danshen in Alzheimer's disease cell model induced by Aβ1-42

INTRODUCTION

Alzheimer's disease (AD) is a chronic neurodegenerative disorder with neither definitive pathogenesis nor effective therapy so far. Danshen, the dried root and rhizome of Salvia miltiorrhiza Bunge, is used extensively in Alzheimer's disease treatment to ameliorate the symptoms, but the underlying mechanism remains to be clarified.

OBJECTIVES

To investigate potential biomarkers for AD and elucidate the protective mechanism of Danshen on AD cell model.

METHODS

An ultra high performance liquid chromatography-quadrupole time of flight mass spectrometry (UHPLC-QTOF/MS)-based approach combined with partial least squares discriminant analysis (PLS-DA) has been developed to discriminate the metabolic modifications between human brain microvascular endothelial cell (hBMEC) and AD cell model induced by amyloid-β protein (Aβ_1-42). To further elucidate the pathophysiology of AD, related metabolic pathways have been studied.

RESULTS

Thirty-three distinct potential biomarkers were screened out and considered as potential biomarkers corresponding to AD, which were mostly improved and partially restored back to normalcy in Danshen pre-protection group. It was found that AD was closely related to disturbed arginine and proline metabolism, glutathione metabolism, alanine aspartate and glutamate metabolism, histidine metabolism, pantothenate and CoA biosynthesis, phenylalanine tyrosine and tryptophan biosynthesis, citrate cycle and glycerophospholipid metabolism, and the protective mechanism of Danshen in AD cell model may be related to partially regulating the perturbed pathways.

CONCLUSIONS

These outcomes provide valuable evidences for therapeutic mechanism investigation of Danshen in AD treatment, and such an approach could be transferred to unravel the mechanism of other traditional Chinese medicine (TCM) and diseases.

Exhaled Breath Condensate: Pilot Study of the Method and Initial Experience in Healthy Subjects

Analysis of Exhaled breath condensate (EBC) is a re-discovered approach to monitoring the course of the disease and reduce invasive methods of patient investigation. However, the major disadvantage and shortcoming of the EBC is lack of reliable and reproducible standardization of the method. Despite many articles published on EBC, until now there is no clear consensus on whether the analysis of EBC can provide a clue to diagnosis of the diseases. The purpose of this paper is to investigate our own method, to search for possible standardization and to obtain our own initial experience. Thirty healthy volunteers provided the EBC, in which we monitored the density, pH, protein, chloride and urea concentration. Our results show that EBC pH is influenced by smoking, and urea concentrations are affected by the gender of subjects. Age of subjects does not play a role. The smallest coefficient of variation between individual volunteers is for density determination. Current limitations of EBC measurements are the low concentration of many biomarkers. Standardization needs to be specific for each individual biomarker, with focusing on optimal condensate collection. EBC analysis has a potential become diagnostic test, not only for lung diseases.

Non-volatile compounds in exhaled breath condensate: review of methodological aspects

In contrast to bronchial and nasal lavages, the analysis of exhaled breath condensate (EBC) is a promising, simple, non-invasive, repeatable, and diagnostic method for studying the composition of airway lining fluid with the potential to assess lung inflammation, exacerbations, and disease severity, and to monitor the effectiveness of treatment regimens. Recent investigations have revealed the potential applications of EBC analysis in systemic diseases. In this review, we highlight the analytical studies conducted on non-volatile compounds/biomarkers in EBC. In contrast to other related articles, this review is classified on the basis of analytical techniques and includes almost all the applied methods and their methodological limitations for quantification of non-volatile compounds in EBC samples, providing a guideline for further researches. The studies were identified by searching the SCOPUS database with the keywords "biomarkers," "non-volatile compounds," "determination method," and "EBC."