Tween 20-capped gold nanoparticles for selective extraction of free low-molecular-weight thiols in saliva followed by capillary electrophoresis with contactless conductivity detection

Application of capillary electrophoresis with capacitively contactless conductivity detection for biomedical analysis

The coupling of capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4 D) has become convenient analytical method for determination of small molecules that do not possess chromogenic or fluorogenic group. The implementations of CE with C4 D in the determination of inorganic and organic ions and amino acids in biomedical field are demonstrated. Attention on background electrolyte composition, sample treatment procedures, and the utilize of multi-detection systems are described. A number of tables summarizing highly developed CE-C4 D methods and the figures of merit attained are involved. Lastly, concluding remarks and perspectives are argued.

Instant Candida albicans Detection Using Ultra-Stable Aptamer Conjugated Gold Nanoparticles

Fungal pathogens such as Candida albicans have significant impacts on women's health and the economy worldwide. Current detection methods often require access to laboratory facilities that are costly, inconvenient, and slow to access. This often leads to self-diagnosis, self-treatment and eventual antifungal resistance. We have created a rapid (within five minutes), cost-effective, and user-friendly method for the early detection of Candida albicans. Our platform utilises aptamer-tagged-gold-core-shell nanoparticles for Candida albicans detection based on the presence of 1,3-β-d glucan molecules. Nanoparticle aggregation occurs in the presence of Candida albicans fungal cells, causing a redshift in the UV-visible absorbance, turning from pink/purple to blue. This colour change is perceptible by the naked eye and provides a "yes"/"no" result. Our platform was also capable of detecting Candida albicans from individual yeast colonies without prior sample processing, dilution or purification. Candida albicans yeast cells were detected with our platform at concentrations as low as 5 × 105 cells within a 50 μL sample volume. We believe that this technology has the potential to revolutionise women's health, enabling women to test for Candida albicans accurately and reliably from home. This approach would be advantageous within remote or developing areas.

Investigation of interactions between biological thiols and gold nanoparticles by capillary electrophoresis with laser-induced fluorescence

Biological thiols spontaneously form a stable Au-S dative bond with gold nanoparticles (AuNP) that might be used for their selective extraction and enrichment in biological samples. In this work, interactions of selected biological thiols (glutathione, cysteine, homocysteine [Hcys], cysteamine [CA], and N-acetylcysteine) with AuNP stabilized by different capping agents (citrate, Tween 20, Brij 35, CTAB, SDS) were investigated by UV-Vis spectroscopy and capillary electrophoresis with laser-induced fluorescence. Spectrophotometric measurements showed aggregation of Hcys and CA with AuNP. In contrast, it was confirmed by CE-LIF that biological thiols were adsorbed to all types of AuNP. Citrate-capped AuNP were selected for AuNP-based extraction of biological thiols from exhaled breath condensate (EBC). Dithiothreitol was utilized for desorption of biological thiols from the AuNP surface, which was followed by derivatization with eosin-5-maleimide and CE-LIF analysis. AuNP-based extraction increased the sensitivity of CE-LIF analysis; however, further optimization of methodology is necessary for accurate quantification of biological thiols in EBC.

Recent developments in capillary and microchip electroseparations of peptides (2021-mid-2023)

This review article brings a comprehensive survey of developments and applications of high-performance capillary and microchip electromigration methods (zone electrophoresis in a free solution or in sieving media, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography) for analysis, micropreparation, and physicochemical characterization of peptides in the period from 2021 up to ca. the middle of 2023. Progress in the study of electromigration properties of peptides and various aspects of their analysis, such as sample preparation, adsorption suppression, electroosmotic flow regulation, and detection, are presented. New developments in the particular capillary electromigration methods are demonstrated, and several types of their applications are reported. They cover qualitative and quantitative analysis of synthetic or isolated peptides and determination of peptides in complex biomatrices, peptide profiling of biofluids and tissues, and monitoring of chemical and enzymatic reactions and physicochemical changes of peptides. They include also amino acid and sequence analysis of peptides, peptide mapping of proteins, separation of stereoisomers of peptides, and their chiral analyses. In addition, micropreparative separations and physicochemical characterization of peptides and their interactions with other (bio)molecules by the above CE methods are described.

Gold Nanoparticles-Based Colorimetric Assays for Environmental Monitoring and Food Safety Evaluation

Recent years have witnessed an exponential increase in the research on gold nanoparticles (AuNPs)-based colorimetric sensors to revolutionize point-of-use sensing devices. Hence, this review is compiled focused on current progress in the design and performance parameters of AuNPs-based sensors. The review begins with the characteristics of AuNPs, followed by a brief explanation of synthesis and functionalization methods. Then, the mechanisms of AuNPs-based sensors are comprehensively explained in two broad categories based on the surface plasmon resonance (SPR) characteristics of AuNPs and their peroxidase-like catalytic properties (nanozyme). SPR-based colorimetric sensors further categorize into aggregation, anti-aggregation, etching, growth-mediated, and accumulation-based methods depending on their sensing mechanisms. On the other hand, peroxidase activity-based colorimetric sensors are divided into two methods based on the expression or inhibition of peroxidase-like activity. Next, the analytes in environmental and food samples are classified as inorganic, organic, and biological pollutants, and recent progress in detection of these analytes are reviewed in detail. Finally, conclusions are provided, and future directions are highlighted. Improving the sensitivity, reproducibility, multiplexing capabilities, and cost-effectiveness for colorimetric detection of various analytes in environment and food matrices will have significant impact on fast testing of hazardous substances, hence reducing the pollution load in environment as well as rendering food contamination to ensure food safety.

Applications of capillary electrophoresis in the fields of environmental, pharmaceutical, clinical and food analysis (2019-2021)

So far, the potential of capillary electrophoresis (CE) in the application fields has been increasingly excavated due to the advantages of simple operation, short analysis time, high-resolution, less sample consumption and low cost. This review examines the implementations and advancements of CE in different application fields (environmental, pharmaceutical, clinical and food analysis) covering the literature from 2019 to 2021. In addition, ultrasmall sample injection volume (nanoliter range) and short optical path lead to relatively low concentration sensitivity of the most frequently used UV-absorption spectrophotometric detection, so the pretreatment technology being developed has been gradually utilized to overcome this problem. Despite the review is focused on the development of CE in the fields of environmental, pharmaceutical, clinical and food analysis, the new sample pretreatment techniques of microextraction and enrichment which fit excellently to CE in recent three years are also described briefly. This article is protected by copyright. All rights reserved.

Separation Methods in Biomedical Analysis, a Booming Field

Many scientific endeavors are dependent upon the accurate quantification of drugs and endogenous substances, such as pharmacokinetics [...]

Fluorescence-Raman dual-mode quantitative detection and imaging of small-molecule thiols in cell apoptosis with DNA-modified gold nanoflowers

The monitoring of small-molecule thiols (especially glutathione) has attracted widespread attention due to their involvement in numerous physiological processes in living organisms and cells. In this work, a dual-mode nanosensor was designed to detect small-molecule thiols, which is based on the "on-off" switch of fluorescence resonance energy transfer (FRET) and surface-enhanced Raman scattering (SERS). Briefly, DNA was modified by Cy5 (signal probe) and disulfide bonds (recognition element). Gold nanoflowers (AuNFs) were used as the fluorescence-quenching and SERS-enhancing substrate. However, small-molecule thiols can cleave disulfide bonds and release short Cy5-labeled chains, causing the recovery of the fluorescence signal and a decrease of the SERS signal. The nanosensor showed a sensitive response to small-molecule thiols represented by GSH, with a linear range of 0.01-3 mM and a detection limit of 913 nM. In addition, it competed with other related biological interferences and presented good stability and better selectivity towards small-molecule thiols. Most importantly, the developed nanosensor had been successfully applied to in situ imaging and quantitative monitoring of the concentration of small-molecule thiols which changed during T-2 toxin-induced apoptosis in HeLa cells. Meanwhile, nanosensors are also versatile with their potential applications and can be easily extended to the detection and imaging of other human cell lines. The proposed method combines the dual advantages of fluorescence and SERS, which has broad prospects for in situ studies of physiological processes involving small-molecule thiols in biological systems.

Recent developments in capillary and microchip electroseparations of peptides (2019-mid 2021)

The review provides a comprehensive overview of developments and applications of high performance capillary and microchip electroseparation methods (zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography) for analysis, microscale isolation, and physicochemical characterization of peptides from 2019 up to approximately the middle of 2021. Advances in the investigation of electromigration properties of peptides and in the methodology of their analysis, such as sample preparation, sorption suppression, EOF control, and detection, are presented. New developments in the individual CE and CEC methods are demonstrated and several types of their applications are shown. They include qualitative and quantitative analysis, determination in complex biomatrices, monitoring of chemical and enzymatic reactions and physicochemical changes, amino acid, sequence, and chiral analyses, and peptide mapping of proteins. In addition, micropreparative separations and determination of significant physicochemical parameters of peptides by CE and CEC methods are described.