Sensitive determination of malondialdehyde in exhaled breath condensate and biological fluids by capillary electrophoresis with laser induced fluorescence detection

A highly sensitive Golgi-targeted fluorescent probe for the simultaneous detection of malondialdehyde and formaldehyde in living systems and foods

Malondialdehyde (MDA) and formaldehyde (FA) are highly active carbonyl substances widely present in both biological and abiotic systems. The detection of MDA and FA is of great significance for disease diagnosis and food safety monitoring. However, due to the similarity in structural properties between MDA and FA, very few probes for synergistically detecting MDA and FA were reported. In addition, functional abnormalities in the Golgi apparatus are closely related to MDA and FA, but currently there are no fluorescent probes that can detect MDA and FA in the Golgi apparatus. Therefore, we constructed a simple Golgi-targetable fluorescent probe GHA based on hydrazine moiety as the recognition site to produce a pyrazole structure after reaction with MDA and to generate a CN double bond after reaction with FA, allowing MDA and FA to be distinguished due to different emission wavelengths during the recognition process. The probe GHA has good specificity and sensitivity. Under the excitation of 350 nm, the blue fluorescence was significantly enhanced at 424 nm when the probe reacted with MDA, and the detection limit was 71 nM. At the same time, under the same excitation of 350 nm, the reaction with FA showed a significant enhancement of green fluorescence at 520 nm, with a detection limit of 12 nM for FA. And the simultaneous and high-resolution imaging of MDA and FA in the Golgi apparatus of cells was achieved. In addition, the applications of the probe GHA in food demonstrated it can provide a powerful method for food safety monitoring. In summary, this study offers a promising tool for the synergistic identification and determination of MDA and FA in the biosystem and food, facilitating the revelation of their detailed functions in Golgi apparatus and the monitoring of food safety.

Malondialdehyde Analysis in Biological Samples by Capillary Electrophoresis: The State of Art

Lipid peroxidation occurs when substances, such as reactive oxygen species, attack lipids. Polyunsaturated fatty acids are the main targets. Several products are formed, including primary products such as lipid hydroperoxides and secondary products such as malondialdehyde (MDA), the most used lipid peroxidation biomarker. As MDA levels are elevated in several diseases, MDA is an essential indicator for assessing pathological states. The thiobarbituric acid reactive substances assay is the most widely used method for MDA determination. However, it lacks specificity. Capillary Electrophoresis (CE) is a separation technique that has been used to quantify MDA in biological samples. This technique has advantages such as the low amount of biological sample required, absence or low volume of organic solvent, short analysis time, separation of interferents, sample preparation step with only protein precipitation, and the possibility of direct detection of the MDA, without derivatization. To our knowledge, this review article is the first to show the CE background for analyzing MDA in biological samples. Therefore, given the potential of MDA in evaluating pathological states, this article demonstrates the potential of CE to become a reference method for MDA determination in clinical analysis laboratories, which will play a significant role in diagnosing and monitoring diseases.

An open source 3D printed autosampler for capillary electrophoresis

BACKGROUND

In-house built capillary electrophoresis (CE) systems represent a significant share of laboratory instrumentation. In most of these instruments, sample injection is effected manually with low to moderate precision and requires skilled operators. Although few automated samplers have been previously developed, typically only one sample at a time can be injected. If a series of samples is to be analyzed, manual intervention is required. In the present work, we developed and constructed a fully automated, open source, CE autosampler, able to handle up to 14 different samples that can be used as a modular component of any in-house built CE instrument.

RESULTS

An inexpensive, 3D printed, open source, autosampler for CE was developed. The autosampler consists of two parts: an injection unit with carousel containing sample and electrolyte vials and a flushing unit, containing a miniature pressure/vacuum pump. The autosampler is operated by an Arduino Mega microcontroller and an Arduino code written in the laboratory. The injection sequence is entered through a keypad and LCD display by the user. The instrument can operate autonomously for extended periods of time. It was used for fully automated analysis and/or calibration of up to 14 samples with excellent injection repeatability reaching less than 2.7% RSD for peak areas. The sampler performance was tested with two independently built CE instruments, a CE system with contactless conductivity detection (C4D) and a CE system with laser induced fluorescence (LIF) detector.

SIGNIFICANCE AND NOVELTY

A novel, 3D printed, Arduino-based autosampler for CE was developed. The autosampler allows autonomous hydrodynamic injection of up to 14 different samples with fully programmable injection sequence, including capillary flushing and high voltage and data acquisition control. It provides the missing instrumental sampling setup for laboratory made CE instruments. It can be simply constructed based on the open-source blueprints in any laboratory and be a useful and time-saving add-on to any modular CE instrument.

Detection of Pyrophosphate and Alkaline Phosphatase Activity Based on PolyT Single Stranded DNA - Copper Nanoclusters

The determination of pyrophosphate and alkaline phosphatase activity plays a significant role in medical diagnosis. In this work, a label-free "ON-OFF-ON" fluorescence strategy is developed for the analysis of pyrophosphate and alkaline phosphatase activity. Using PolyT single strand DNA as templates to synthesize fluorescent copper nanoparticles, the coordination effect of pyrophosphoric acid on Cu²⁺ inhibited the generation of fluorescence. Afterwards, the addition of alkaline phosphatase into hydrolyze pyrophosphoric acid resulted in the release of Cu^2+, whereby the fluorescence intensity could be recovered. Thereupon enhanced-sensitivity for alkaline phosphatase was obtained (0.1 mU/L), much better than previously reported methods. Meanwhile, it could be performed directly in homogeneous solution, which was very close to the actual activity level of alkaline phosphatase under physiological conditions. Likewise, satisfactory results were also obtained in specificity assessment, which demonstrated its potential application in clinical diagnosis. Notably, a new, sensitive, low-cost, short-time, and high-sensitivity platform for alkaline phosphatase detection was constructed, and the design of biosensor using DNA-templated Copper nanoclusters (CuNCs) was instructed in this study.

A simple and sensitive preconcentration strategy by coupling salting-out assisted liquid-liquid extraction with online three-step stacking for the determination of potent anti-tumour compound vinblastine and its precursor in biological samples by capillary electrophoresis

A sensitive capillary electrophoresis strategy was developed by combining salting-out assisted liquid-liquid extraction and online three-step stacking to detect trace quantities of antitumour indole alkaloids in complex biological samples. The proposed strategy fully exploits these two technologies such that extraction, online stacking and separation are combined in a fast and efficient manner. First, salting-out assisted liquid-liquid extraction was used to extract three indole alkaloids (vinblastine sulfate, catharanthine sulfate and vindoline) from complex biomasses. An appropriate volume of acetonitrile (ACN) was mixed with a faecal aqueous solution to precipitate proteins. The mixed solution was vortexed, followed by the addition of ammonium sulfate ((NH₄)₂SO₄) to induce two-phase separation. Alkaloids were effectively extracted into the organic phase, which was then subjected to capillary electrophoresis (CE) analysis. The sensitivity of capillary electrophoresis was effectively improved by online three-step stacking. Good linearity of the calibration curve for each indole alkaloid was obtained in the concentration range of 0.1-1 μg/mL. Under optimal conditions, the sensitivity of ordinary injection was increased by up to 2366-fold, confirming the applicability of the proposed strategy for the sensitive determination of trace indole alkaloids in complex biological samples.

Breathomics: Review of Sample Collection and Analysis, Data Modeling and Clinical Applications

Metabolomics research is rapidly gaining momentum in disease diagnosis, on top of other Omics technologies. Breathomics, as a branch of metabolomics is developing in various frontiers, for early and noninvasive monitoring of disease. This review starts with a brief introduction to metabolomics and breathomics. A number of important technical issues in exhaled breath collection and factors affecting the sampling procedures are presented. We review the recent progress in metabolomics approaches and a summary of their applications on the respiratory and non-respiratory diseases investigated by breath analysis. Recent reports on breathomics studies retrieved from Scopus and Pubmed were reviewed in this work. We conclude that analyzing breath metabolites (both volatile and nonvolatile) is valuable in disease diagnoses, and therefore believe that breathomics will turn into a promising noninvasive discipline in biomarker discovery and early disease detection in personalized medicine. The problem of wide variations in the reported metabolite concentrations from breathomics studies should be tackled by developing more accurate analytical methods and sophisticated numerical analytical alogorithms.

Optimization of background electrolyte composition for simultaneous contactless conductivity and fluorescence detection in capillary electrophoresis of biological samples

In this article, optimization of BGE for simultaneous separation of inorganic ions, organic acids, and glutathione using dual C⁴ D-LIF detection in capillary electrophoresis is presented. The optimized BGE consisted of 30 mM 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid, 15 mM 2-amino-2-hydroxymethyl-propane-1,3-diol, and 2 mM 18-crown-6 at pH 7.2 and allowed simultaneous separation of ten inorganic anions and cations, three organic acids and glutathione in 20 min. The samples were injected hydrodynamically from both capillary ends using the double-opposite end injection principle. Sensitive detection of anions, cations, and organic acids with micromolar LODs using C⁴ D and simultaneously glutathione with nanomolar LODs using LIF was achieved in a single run. The developed BGE may be useful in analyses of biological samples containing analytes with differing concentrations of several orders of magnitude that is not possible with single detection mode.

Capillary electrophoresis of small ions and molecules in less conventional human body fluid samples: A review

In recent years, advances in sensitive analytical techniques have encouraged the analysis of various compounds in biological fluids. While blood serum, blood plasma and urine still remain the golden standards in clinical, toxicological and forensic science, analyses of other body fluids, such as breast milk, exhaled breath condensate, sweat, saliva, amniotic fluid, cerebrospinal fluid, or capillary blood in form of dried blood spots are becoming more popular. This review article focuses on capillary electrophoresis and microchip electrophoresis of small ions and molecules (e.g. inorganic cations/anions, basic/acidic drugs, small acids/bases, amino acids, peptides and other low molecular weight analytes) in various less conventional human body fluids and hopes to stimulate further interest in the field.

Sensitive determination of aldehyde metabolites in exhaled breath condensate using capillary electrophoresis with laser-induced fluorescence detection

A novel capillary electrophoresis with laser-induced fluorescence detection method has been developed for the analysis of aldehyde metabolism biomarkers for oxidative stress in exhaled breath condensate (EBC), and fluorescein 5-thiosemicarbazide was used as a derivatization reagent. In a simple capillary zone electrophoresis mode, ten low molecular weight aldehydes (LMWAs) could be well separated within 30 min. The reaction efficiency was doubled by increasing sample solution pH and magnetic stirring, and the LODs of this method reached 0.16-3.4 nM (S/N = 3). Acceptable recoveries (82.1-115%) were obtained for EBC samples, and the RSD data were within 7.9%. This developed method has been applied for the analyses of EBC samples and evaluation of the correlation between smoking and the contents of aldehyde metabolites in EBC. Due to no need of buffer additives and sample preconcentration, this proposed method may provide an appealing alternative for the trace analyses of LMWAs in noninvasive biofluids. Graphical abstract ᅟ.

Analysis of malondialdehyde in human plasma samples through derivatization with 2,4-dinitrophenylhydrazine by ultrasound-assisted dispersive liquid-liquid microextraction-GC-FID approach

A sensitive and reliable ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) procedure was developed and validated for extraction and analysis of malondialdehyde (MDA) as an important lipids-peroxidation biomarker in human plasma. In this methodology, to achieve an applicable extraction procedure, the whole optimization processes were performed in human plasma. To convert MDA into readily extractable species, it was derivatized to hydrazone structure-base by 2,4-dinitrophenylhydrazine (DNPH) at 40 °C within 60 min. Influences of experimental variables on the extraction process including type and volume of extraction and disperser solvents, amount of derivatization agent, temperature, pH, ionic strength, sonication and centrifugation times were evaluated. Under the optimal experimental conditions, the enhancement factor and extraction recovery were 79.8 and 95.8%, respectively. The analytical signal linearly (R² = 0.9988) responded over a concentration range of 5.00-4000 ng mL^-1 with a limit of detection of 0.75 ng mL^-1 (S/N = 3) in the plasma sample. To validate the developed procedure, the recommend guidelines of Food and Drug Administration for bioanalytical analysis have been employed.

Hollow Pt-Functionalized SnO2 Hemipill Network Formation Using a Bacterial Skeleton for the Noninvasive Diagnosis of Diabetes

Hollow-structured nanomaterials are presented as an outstanding sensing platform because of their unique combination of high porosity in both the micro- and nanoscale, their biocompatibility, and flexible template applicability. Herein, we introduce a bacterial skeleton method allowing for cost-effective fabrication with nanoscale precision. As a proof-of-concept, we fabricated a hollow SnO₂ hemipill network (HSHN) and a hollow Pt-functionalized SnO₂ hemipill network (HPN). A superior detecting capability of HPN toward acetone, a diabetes biomarker, was demonstrated at low concentration (200 ppb) under high humidity (RH 80%). The detection limit reaches 3.6 ppb, a level satisfying the minimum requirement for diabetes breath diagnosis. High selectivity of the HPN sensor against C₆H₆, C₇H₈, CO, and NO vapors is demonstrated using principal component analysis (PCA), suggesting new applications of HPN for human-activity monitoring and a personal healthcare tool for diagnosing diabetes. The skeleton method can be further employed to mimic nanostructures of biomaterials with unique functionality for broad applications.

Recent advances in CE and microchip-CE in clinical applications: 2014 to mid-2017

CE and microchip CE (ME) are powerful tools for the analysis of a number of different analytes and have been applied to a variety of clinical fields and human samples. This review will present an overview of the most recent applications of these techniques to different areas of clinical medicine during the period of 2014 to mid-2017. CE and ME have been applied to clinical chemistry, drug detection and monitoring, hematology, infectious diseases, oncology, endocrinology, neonatology, nephrology, and genetic screening. Samples examined range from serum, plasma, and urine to lest utilized materials such as tears, cerebral spinal fluid, sweat, saliva, condensed breath, single cells, and biopsy tissue. Examples of clinical applications will be given along with the various detection systems employed.