Online Monitoring of Lactate Efflux by Multi-Channel Microfluidic Chip-Mass Spectrometry for Rapid Drug Evaluation

An online multichannel microfluidic chip-mass spectrometry (MS) platform was developed for cell metabolism studies. Paper-spray ionization was employed for microsampling from different microchannels and, at the same time, the interface for direct MS analysis without any sample pretreatment. Near-real-time MS sensing of lactate in different microfluidic channels could be achieved in a preprogrammed and automatic manner. Influences of hypoxia on lactate efflux from normal cells and cancer cells, as well as the differential inhibitory effects and dose–response information on α-cyano-4-hydroxycinnamate on cancer cells of different types were exhibited. The potential of further coupling MS, complementary to optical and electrochemical techniques, to microfluidic devices for cell studies was thus demonstrated

Determination of Ammonia in Water Based on Chemiluminescence Resonance Energy Transfer between Peroxymonocarbonate and Branched NaYF₄:Yb³⁺/Er³⁺ Nanoparticles

The ultraweak chemiluminescence (CL) from the reaction of hydrogen peroxide and carbonate is strongly enhanced by the branched NaYF₄:Yb³⁺/Er³⁺ nanoparticle (NP) in the presence of aqueous ammonia. It was explained that ammonia catalyzes the decomposition of peroxymonocarbonate, which is the product of hydrogen peroxide mixing with bicarbonate, making the formation of (CO₂)₂*, (O₂)₂*, and ¹O₂. The excitation energy, carried by these emitter intermediates, can be transferred to NaYF₄:Yb³⁺/Er³⁺ NP. The CL intensity is directly proportional to the concentration of ammonia present in the solution. A flow-injection CL system with high sensitivity, selectivity, and reproducibility is proposed for the determination of aqueous ammonia. The proposed method exhibited advantages in a larger linear range from 0.5 μmol L^–1 to 50 μmol L^–1 and a lower detection limit of 1.1 × 10^–8 mol L^–1 (S/N = 3). This method has been successfully applied to the evaluation of ammonia in water samples with recoveries from 95% to 108%. The relative standard deviations are 1.8% and 4.1% for intra-assay and inter-assay precision, respectively

Plasmon-Assisted Enhancement of the Ultraweak Chemiluminescence Using Cu/Ni Metal Nanoparticles

Cu/Ni nanoparticles (NPs) with stable fluorescence and excellent water dispersion were synthesized through a facile aqueous solution method with a similar Kirkendall effect. Ultraweak chemiluminescence (CL) from the oxidation reaction between sodium hydrogen carbonate (NaHCO₃) and hydrogen peroxide (H₂O₂) in neutral medium was significantly enhanced by 60 ± 5 nm Cu/Ni NP with a copper and nickel molar ratio of 1:2. The enhancement of the time-dependent CL was dependent on the composition of the NP and the order of reagent addition. On the basis of studies of CL emission spectra, electron spin resonance spectra, UV–vis absorption, and fluorescence spectra, a mechanism of plasmon-assisted metal catalytic effect for this metal NP (MNP)-enhanced CL was proposed. The surface plasmons of MNP can obtain energy from chemical reaction, forming the activated MNP (MNP*), which was coupled to ·OH radical to produce the new adduct ·OH-MNP*. The ·OH-MNP* can accelerate the reaction rate of HCO₃^– for the generation of emitter intermediate (CO₂)₂*, which can lead the enhanced CL for the overall reaction

Aggregation-Induced Structure Transition of Protein-Stabilized Zinc/Copper Nanoclusters for Amplified Chemiluminescence

A stable, water-soluble fluorescent Zn/Cu nanocluster (NC) capped with a model protein, bovine serum albumin (BSA), was synthesized and applied to the reaction of hydrogen peroxide and sodium hydrogen carbonate. A significantly amplified chemiluminescence (CL) from the accelerated decomposition of peroxymonocarbonate (HCO₄^–) by the nanosluster was observed. The CL reaction led to a structure change of BSA and aggregation of Zn/Cu NCs. In the presence of H₂O₂, Zn/Cu–S bonding between BSA scaffolds and the encapsulated Zn/Cu@BSA NC was oxidized to form a disulfide product. Zn/Cu@BSA NCs were prone to aggregate to form larger nanoparticles without the protection of scaffolds. It is revealed that the strong CL emission was initiated from the catalysis of Zn/Cu@BSA NC and the surface plasmon coupling of the formed Zn/Cu nanoparticles in a single chemical reaction. This amplified CL was successfully exploited for selective sensing of hydrogen peroxide in environmental samples

Qualitative and Quantitative Analysis of Tumor Cell Metabolism via Stable Isotope Labeling Assisted Microfluidic Chip Electrospray Ionization Mass Spectrometry

In this work, a stable isotope labeling assisted microfluidic chip electrospray ionization mass spectrometry (SIL-chip–ESI-MS) platform for qualitative and quantitative analysis of cell metabolism was developed. Microfluidic cell culture, drug-induced cell apoptosis analysis, and cell metabolism measurements were performed simultaneously on the specifically designed device. MCF-7 cells were cultivated in vitro and exposed in anticancer agent (genistein and genistein-<i>d</i>₂) for cell-based drug assay. A dual-isotopic labeling was presented for effective qualitative analysis of multiplex metabolites. Interestingly, three coeluting pairs of isotopomers appeared with an <i>m</i>/<i>z</i> difference of two. Despite complex biological matrixes, they can be easily recognized and identified by chip–ESI-MS/MS, which significantly facilitates candidate biomarker discovery. The quantitative performance of this system was evaluated using genistein as a model drug by means of stable isotope dilution analysis. The linear equation obtained is <i>y</i> = 0.06<i>x</i> – 3.38 × 10^–3 (<i>R</i>² = 0.995) at the dynamic range from 0.5 to 40 μM. The detection limit is 0.2 μM. The method shows an excellent stability of 2.2% relative standard deviation (RSD) and a good repeatability of 5.5% RSD. Our results have successfully demonstrated the capability of selective and quantitative analysis of cell-based drug absorption and metabolites with high stability, sensitivity, and repeatability on the chip–ESI-MS system. Consequently, the present device shows promise as a high-throughput, low-cost, and online platform for cell metabolism studies and drug screening processes

Development of a highly sensitive and selective microplate chemiluminescence enzyme immunoassay for the determination of free thyroxine in human serum-4

<p><b>Copyright information:</b></p><p>Taken from "Development of a highly sensitive and selective microplate chemiluminescence enzyme immunoassay for the determination of free thyroxine in human serum"</p><p></p><p>International Journal of Biological Sciences 2007;3(5):274-280.</p><p>Published online 20 Apr 2007</p><p>PMCID:PMC1865090.</p><p>© Ivyspring International Publisher. This is an open-access article distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by-nc-nd/3.0/). Reproduction is permitted for personal, noncommercial use, provided that the article is in whole, unmodified, and properly cited.</p

Evaluation of the Absorption of Methotrexate on Cells and Its Cytotoxicity Assay by Using an Integrated Microfluidic Device Coupled to a Mass Spectrometer

An integrated microfluidic device was developed for high-throughput drug screening with an online electrospray ionization quadrupole time-of-flight mass spectrometer (ESI-Q-TOF MS). The multiple gradient generator followed by an array of microscale cell culture chambers and on-chip solid-phase extraction (SPE) columns for sample pretreatment prior to mass analysis was integrated in the device which was fabricated in one single step. By using the combination system, the process for characterization of drug absorption and evaluation of cytotoxicity could be simultaneously realized. To validate the feasibility, the absorption of methotrexate and its effects on HepG2 and Caco-2 cells were investigated. With the increasing concentration of drugs, the percentage of apoptotic cells appeared in a dose-dependent fashion. By comparison with the results obtained from ESI-Q-TOF MS analysis and cytotoxicity assay, we found that higher intracellular drug concentration resulted in increased cell cytotoxicity. The technique presented herein provides an easy protocol to screen drugs rapidly with low drug consumption, high throughput, and high sensitivity

Development of a highly sensitive and selective microplate chemiluminescence enzyme immunoassay for the determination of free thyroxine in human serum-3

<p><b>Copyright information:</b></p><p>Taken from "Development of a highly sensitive and selective microplate chemiluminescence enzyme immunoassay for the determination of free thyroxine in human serum"</p><p></p><p>International Journal of Biological Sciences 2007;3(5):274-280.</p><p>Published online 20 Apr 2007</p><p>PMCID:PMC1865090.</p><p>© Ivyspring International Publisher. This is an open-access article distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by-nc-nd/3.0/). Reproduction is permitted for personal, noncommercial use, provided that the article is in whole, unmodified, and properly cited.</p

Development of a highly sensitive and selective microplate chemiluminescence enzyme immunoassay for the determination of free thyroxine in human serum-1

<p><b>Copyright information:</b></p><p>Taken from "Development of a highly sensitive and selective microplate chemiluminescence enzyme immunoassay for the determination of free thyroxine in human serum"</p><p></p><p>International Journal of Biological Sciences 2007;3(5):274-280.</p><p>Published online 20 Apr 2007</p><p>PMCID:PMC1865090.</p><p>© Ivyspring International Publisher. This is an open-access article distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by-nc-nd/3.0/). Reproduction is permitted for personal, noncommercial use, provided that the article is in whole, unmodified, and properly cited.</p

Microfluidic Chip-Based Modeling of Three-Dimensional Intestine–Vessel–Liver Interactions in Fluorotelomer Alcohol Biotransformation

Plyfluoroalkyl substance (PFAS), featured with incredible persistence and chronic toxicity, poses an emerging ecological and environmental crisis. Although significant progress has been made in PFAS metabolism in vivo, the underlying mechanism of metabolically active organ interactions in PFAS bioaccumulation remains largely unknown. We developed a microfluidic-based assay to recreate the intestine–vessel–liver interface in three dimensions, allowing for high-resolution, real-time images and precise quantification of intestine–vessel–liver interactions in PFAS biotransformation. In contrast to the scattered arrangement of vascular endothelium on the traditional d-polylysine-modified two-dimensional (2D) plate, the microtubules in our three-dimensional (3D) platform formed a dense honeycomb network through the ECM, with longer tubular structures. Additionally, the slope culture of epithelial cells in our platform exhibited a closely arranged and thicker cell layer than the planar culture. To dynamically monitor the metabolic crosstalk in the intestinal–vascular endothelium–liver interaction under exposure to fluorotelomer alcohols (FTOHs), we combined the chip with a solid-phase extraction-mass spectrometry (SPE-MS) system. Our findings revealed that endothelial cells were involved in the metabolic process of FTOHs. The transformation of intestinal epithelial and hepatic epithelial cells produces toxic metabolite fluorotelomer carboxylic acids (FTCAs), which circulate to endothelial cells and affect angiogenesis. This system shows promise as an enhanced surrogate model and platform for studying pollutant exposure as well as for biomedical and pharmaceutical research