A compact short-capillary based high-speed capillary electrophoresis bioanalyzer

3D printed cartridge for high-speed capillary electrophoresis with sheath liquid thermostatting and contactless conductivity detection

The high-speed capillary electrophoresis (HSCE) method is a technique that utilizes a high electric field strength applied through a short capillary to reduce the time required for sample separation. However, the increased electric field strength may result in pronounced Joule heating effects. To address this, we describe a 3D-printed cartridge with integrated contactless conductivity detection (C⁴D) head and a sheath liquid channel. The C⁴D electrodes and Faraday shield layers are fabricated by casting Wood's metal in chambers inside the cartridge. Effective thermostatting of the short capillary is achieved by flowing Fluorinert liquid, which provides better heat dissipation compared to airflow. A HSCE device is created by using the cartridge and a modified slotted-vial array sample-introduction approach. Analytes are introduced through electrokinetic injection. With the help of sheath liquid thermostatting, background electrolyte concentration can be increased to several hundred mM, resulting in improved sample stacking and peak resolutions. Additionally, the baseline signal is flattened. Typical cations such as NH₄⁺, K⁺, Na⁺, Mg²⁺, Li⁺, and Ca²⁺ can be separated within 22 s with an applied field strength of 1200 V/cm. The limit of detection ranges from 2.5 to 4.6 μM with a relative standard deviation of migration times of 1.1-1.2% (n = 17). The method has been applied to detect cations in drinking water and black tea leaching for drink safety testing, and to identify explosive anions in paper swabs. Samples can be directly injected without the need for dilution.

LIFGO: A modular laser-induced fluorescence detection system based on plug-in blocks

In this work, a laser-induced fluorescence (LIF) detection system built in a modular assembling mode was developed based on commercial LEGO blocks and 3D printed blocks. We designed and fabricated a variety of 3D printed building blocks fixed with optical components, including laser light source, filters, lens, dichroic mirror, photodiode detector, and control circuits. Utilizing the relatively high positioning precision of the plug-in blocks, a modular construction strategy was adopted using the flexible plug-in combination of the blocks to build a highly sensitive laser-induced fluorescence detection system, LIFGO. The LIFGO system has a simple structure which could be constructed by inexperienced users within 3 h. We optimized the structure and tested the performance of the LIFGO system, and its detection limits for sodium fluorescein solution in 100 μm i.d. and 250 μm i.d. capillaries were 7 nM and 0.9 nM, respectively. Based on the LIFGO system, we also built a simple capillary electrophoresis (CE) system and applied it to the analysis of DNA fragments to demonstrate its application possibility in biochemical analysis. The separation of 7 fragments in DL500 DNA markers were completed in 600 s. Because of the features of low cost (less than $100) and easy-to-build construction, we introduced the LIFGO system to the experimental teaching of instrumental analysis for undergraduate students. The modular construction form of the LIF detection system greatly reduces the threshold of instrument construction, which is conducive to the popularization of the LIF detection technique in routine laboratories as well as the reform of experimental teaching mode.

Handheld laser-induced fluorescence detection systems with different optical configurations

There is a growing urgent requirement for miniaturized laser-induced fluorescence (LIF) detection systems in many research fields. In this work, miniaturized LIF detectors with three different optical configurations of orthogonal, confocal, and oblique were developed, using a laser diode as the excitation source and a photodiode as the photodetector. The computer simulation and experimental methods were used to investigate the distributions of laser scattered light and fluorescent light near the detection window. Other conditions including the solution preparation, sample flow rate, alignment method and filter model were also optimized. Under the optimized conditions, the detection limits of sodium fluorescein for orthogonal and confocal LIF detectors were 40 pM and 50 pM, respectively, while the limit of detection (LOD) for oblique LIF detector were 1 nM (45°) and 7 nM (67.5°). We further built a fully integrated handheld orthogonal LIF detector with a total size of 50 × 20 × 46 mm³, a cost of $380, and a detection limit of 10 pM for sodium fluorescein. It is expected that such a LIF detector could be applied in field analysis as a portable instrument or in other analysis systems as a detection module.

3D printed two-in-one on-capillary detector: Combining contactless conductometric and photometric detection for capillary electrophoresis

In this work, for the first time, a 3D printed two-in-one on-capillary detector, combining contactless conductometric detection (C⁴D) and photometric detection (PD), is fabricated for capillary electrophoresis (CE). The C⁴D Faraday shield (FS) is printed using electrically conductive composite polylactic acid (PLA) to minimize the stray capacitance. Non-conductive PLA is also used to print the insulator of FS to prevent the electrical conduction with two stainless steel electrodes. A novel collimator, consisting of two partially aligned pinholes, is printed by conductive material to collimate the light-emitting diode beam. The C⁴D detection has a signal-to-noise ratio of 1092 ± 2 for 200 μM potassium on a 25 μm id capillary. The PD detection shows excellent linearity with stray light down to 8% and an effective path length at 73% of a 75 μm id capillary. The analytical performance is demonstrated by CE separation and detection of cations. PD shows limits of detection (LODs) of 1.3, 0.9, and 1.7 μM for cobalt, copper and zinc, which are complexed with 4-(2-Pyridylazo) resorcinol, while C⁴D shows LODs of 1.2, 1.4, 21 and 2.6 μM for potassium, sodium, cobalt and zinc, respectively.

High-throughput monitoring of biomass conversion reaction with automatic time-resolved analysis

Reactions of biomass conversions are of great importance in fine chemistry for substantial development. While numerous studies have been performed to search for functional materials to catalyze biomass conversions, a robust and high-throughput analytical method is rather limited, which may hamper further integration and automation of the reactions. Here we propose an automatic and sequential method for the investigation of glucose conversion. By combining sequential sample injection and high-speed capillary electrophoresis (HSCE) techniques, we can monitor the glucose conversion from the beginning toward the end with a good temporal resolution. The HSCE assays are performed using short capillaries (effective length of 10 cm, i.d./o.d. of 50 μm/365 μm), and the analytes are separated at an electric field of 467 V/cm and are detected by UV-absorption at 200 nm with mixed 0.2 mM CTAB, 10 mM borate, 20 mM sorbic acid (pH 12.2) as the background electrolyte. All compounds involved in the reaction, including all products (fructose, 5-hydroxymethylfurfural, formic acid and levulinic acid) and the remaining substrate glucose, are efficiently separated and simultaneously detected from just one analysis with a temporal resolution of one minute. The method exhibits high-resolution separation, a wide linear range with limit-of-detection down to μg/mL-level, as well as excellent repeatability in sequential analysis. It is indicated that the proposed method is of great value in the analysis of complicated biomass conversion and could be potentially applied in various catalytic chemical reactions.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Complete capillary electrophoresis process on a drone: towards a flying micro-lab

Hazardous remote places exist in the world. Why should health or life be risked sending a scientist to the investigation site, as the remote analytical instrumentation exists? Different scientific fields require instruments that could be used on-site (in situ), therefore the purpose of this work was to design a fully automated chemical analysis system small enough to be mountable on a drone. Here we show an autonomous analytical system with sampling capability on a drone. The system is suited for the remote and autonomous analysis of volatile and non-volatile chemicals in the air. The designed system weighs less than 800 g. Data are transmitted wirelessly. Collected substances are separated automatically without the intervention of the operator using the method of capillary zone electrophoresis. The analytes are detected using a miniaturized contactless conductivity detector quantifying them down to less than 1 μM. In this work, we demonstrated sampling and separation of volatile amines (triethylamine and diethylamine) and organic acids (acetic and formic acids), non-volatile inorganic cations (K⁺, Ca²⁺, Na⁺), and protein (bovine serum albumin) in the aerosol state. It was shown that the capillary electrophoretic analysis can be performed on a hovering drone. We anticipate our work to be a starting point for more sophisticated, autonomous complex sample analysis. We believe that our designed instrument will enable the investigation of hazardous places in different research fields.

Silicon Photomultipliers as a Low-Cost Fluorescence Detector for Capillary Electrophoresis

Capillary electrophoresis (CE) is a highly efficient separation method capable of handling small sample volumes (∼pL) and low (∼yoctomole) detection limits and, as such, is ideal for applications that require high sensitivity, such as single-cell analysis (Chen et al. Anal. Chem. 1996, 68 (4), 690-696; Cohen et al. Annu. Rev. Anal. Chem. 2008, 1 (1), 165-190; Vickerman et al. ACS Chem. Biol. 2018, 13 (7), 1741-1751). Low-cost CE instrumentation is quickly expanding, but low-cost, open-source fluorescence detectors with ultrasensitive detection limits are lacking (Vickerman et al. ACS Chem. Biol. 2018, 13 (7), 1741-1751; Fang et al. Electrophoresis 2016, 37 (17-18), 2376-2383; Casto et al. Anal. Chem. 2019, 40 (1), 65-78). Silicon photomultipliers (SiPM) are inexpensive, low-footprint detectors with the potential to fill the role as a detector when cost, size, and customization are important. In this work, we demonstrate the use of a SiPM in CE with zeptomolar detection limits and a dynamic range spanning 5 orders of magnitude, comparable to photomultiplier detectors. The performance of these detectors was measured using a continuous wave excitation laser in an epifluorescence detection configuration. We characterize the performance of the SiPM as a highly sensitive detector by measuring enzyme activity in single cells. This simple, small footprint, and low-cost (<$130) light detection circuit will be beneficial for open-source, portable, and budget-friendly instrumentation requiring high sensitivity.

Laser-induced fluorescence detector with a fiber-coupled micro GRIN lens for capillary electrophoresis

Capillary electrophoresis coupled with sheath-flow laser-induced fluorescence (LIF) detection has been shown to offer outstanding sensitivity for chemical and biochemical analysis. However, a major drawback remains with the complexity of the optical configuration traditionally employed. Here we present a simplified confocal optics based on fiber optics and micro gradient-index (GRIN) lenses for modular optical design in capillary electrophoresis with laser-induced fluorescence. We demonstrate the use of the optical system with a sheath-flow cuvette as the laser-induced fluorescence detector for capillary electrophoresis. The system's performance was established with concentration detection limits of 8±2pM and mass detection limits of 57 zeptomole for a standard sodium fluorescein sample.

Consecutive and automatic detection of multi-gene mutations from colorectal cancer samples by coupling droplet array-based capillary electrophoresis and PCR-RFLP

The efficacy of targeted therapy is associated with multi-gene mutation status. Carrying out effective multi-genotyping analysis in combination has been a challenge in clinical settings. We therefore developed a droplet-based capillary electrophoresis (CE) system coupled with PCR-restriction fragment length polymorphism (PCR-RFLP) technology to detect multi-gene mutations from a small volume of samples. A 16 × 16 200-nL droplet array for sample encapsulation was constructed on a glass chip. The electrophoresis system consisted of a tapered vertical capillary filled with polyvinylpyrrolidone, a laser-induced fluorescence detector, and a high voltage power supply. Notably, a droplet-based electrokinetic sample introduction method and a "∩" shape capillary were developed to facilitate consecutive droplet sampling using a home-made automatic control module. The DL2000 DNA marker was consecutively separated, achieving high migration time and plate number reproducibility. The system was further applied to detect PCR-RFLP products. For colorectal cancer (CRC) cell lines, KRAS, BRAF, and PIK3CA were genotyped with a sensitivity of 0.25%. For CRC patient specimens, 30 samples were consecutively and automatically multi-genotyped without inter-sample contamination, with a lowest mutation frequency of 0.37%. For the first time, we developed a droplet-based CE system for consecutive DNA analysis with low sample consumption. This automated CE system could be further developed to integrate the full process of gene mutation detection, serving as a more effective platform for individualised therapy.

The effect of electrophoretic parameters on separation performance of short DNA fragments

Effective separation of short DNA fragments is important for the identification of PCR or LAMP products. We investigated the effect of electric field strength, sample plug width, effective length of the capillary, concentration and molecular weight of polymer on the separation performance of small DNA. Results demonstrated that the sample plug played a non-negligible role in the peak broadening. The migration time of DNA was exponentially decreased with the increase of electric field strength. Increasing effective length of capillary, concentration or molecular weight of HEC may improve the separation performance, but it was at the cost of long migration time.

A Low-Cost Palmtop High-Speed Capillary Electrophoresis Bioanalyzer with Laser Induced Fluorescence Detection

In this work, we developed a miniaturized palmtop high-speed capillary electrophoresis (CE) system integrating whole modules, including picoliter-scale sample injection, short capillary-based fast CE, high-voltage power supply, orthogonal laser induced fluorescence (LIF) detection, battery, system control, on-line data acquisition, processing, storage, and display modules. A strategy of minimalist miniaturization combining minimal system design and low-cost system construction was adopted to achieve the instrument miniaturization with extremely low cost, which is differing from the current microfabrication strategy used in most reported miniaturized CE systems. With such a strategy, the total size of the bioanalyzer was minimized to 90 × 75 × 77 mm (length × width × height) and the instrument cost was reduced to ca. $500, which demonstrated the smallest and lowest-cost CE instrument with LIF detection in so far reported systems. The present bioanalyzer also exhibited comparable analytical performances to previously-reported high-speed CE systems. A limit of detection of 1.02 nM sodium fluorescein was obtained. Fast separations were achieved for multiple types of samples as amino acids, amino acid enantiomers, DNA fragments, and proteins with high efficiency. We applied this instrument in colorectal cancer diagnosis for detecting KRAS mutation status by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

Recent advances in amino acid analysis by capillary electromigration methods: June 2015-May 2017

In the tenth edition of this article focused on recent advances in amino acid analysis using capillary electrophoresis, we describe the most important research articles published on this topic during the period from June 2015 to May 2017. This article follows the format of the previous articles published in Electrophoresis. The new developments in amino acid analysis with CE mainly describe improvements in CE associated with mass spectrometry. Focusing on applications, we mostly describe clinical works, although metabolomics studies are also very important. Finally, works focusing on amino acids in food and agricultural applications are also described.

Advances in capillary electrophoresis and the implications for drug discovery

INTRODUCTION

Many screening platforms are prone to assay interferences that can be avoided by directly measuring the target or enzymatic product. Capillary electrophoresis (CE) and microchip electrophoresis (MCE) have been applied in a variety of formats to drug discovery. CE provides direct detection of the product allowing for the identification of some forms of assay interference. The high efficiency, rapid separations, and low volume requirements make CE amenable to drug discovery. Areas covered: This article describes advances in capillary electrophoresis throughput, sample introduction, and target assays as they pertain to drug discovery and screening. Instrumental advances discussed include integrated droplet microfluidics platforms and multiplexed arrays. Applications of CE to assays of diverse drug discovery targets, including enzymes and affinity interactions are also described. Expert opinion: Current screening with CE does not fully take advantage of the throughputs or low sample volumes possible with CE and is most suitable as a secondary screening method or for screens that are inaccessible with more common platforms. With further development, droplet microfluidics coupled to MCE could take advantage of the low sample requirements by performing assays on the nanoliter scale at high throughput.