Smart portable electrophoresis instrument based on multipurpose microfluidic chips with electrochemical detection

Rapid analysis of intraperitoneally administered morphine in mouse plasma and brain by microchip electrophoresis-electrochemical detection

Animal studies remain an essential part of drug discovery since in vitro models are not capable of describing the complete living organism. We developed and qualified a microchip electrophoresis-electrochemical detection (MCE-EC) method for rapid analysis of morphine in mouse plasma using a commercial MCE-EC device. Following liquid-liquid extraction (LLE), we achieved within-run precision of 3.7 and 4.5% (coefficient of variation, CV, n = 6) and accuracy of 106.9% and 100.7% at biologically relevant morphine concentrations of 5 and 20 µM in plasma, respectively. The same method was further challenged by morphine detection in mouse brain homogenates with equally good within-run precision (7.8% CV, n = 5) at 1 µM concentration. The qualified method was applied to analyze a set of plasma and brain homogenate samples derived from a behavioral animal study. After intraperitoneal administration of 20 mg/kg morphine hydrochloride, the detected morphine concentrations in plasma were between 6.7 and 17 µM. As expected, the morphine concentrations in the brain were significantly lower, ca. 80–125 nM (280–410 pg morphine/mg dissected brain), and could only be detected after preconcentration achieved during LLE. In all, the microchip-based separation system is proven feasible for rapid analysis of morphine to provide supplementary chemical information to behavioral animal studies.

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.

Total polyphenols content in white wines on a microfluidic flow injection analyzer with embedded optical fibers

Absorbance detection in food microdevices has not been thoroughly used due to low levels of sensitivity in measurements. Thus, it is necessary to develop microfluidic methods for improving photometric detection. For this purpose, a simple coupled-optical-fiber-polydimethylsiloxane (PDMS) microdevice was developed, to quantify polyphenols content in white wine employing the Folin-Ciocalteu reaction method. A 6V and 10W halogen lamp with an optical path length of 7mm between optical fibers, which were placed into the microchip, using guides at the outlet of the flow, increased the level of sensitivity during detection. The linear range was from 0.03mmol/L to 0.18mmol/L. Thus, the corresponding equation was: Abs=4.00(±0.16) [tannic acid]+0.17(±0.017). Intra-laboratory repeatability and reproducibility percentages were 2.95% and 6.84%, respectively. Such results were compared to those obtained from applying the conventional flow-injection analysis method, based on the same type of reaction. The relative error between methods was less than 13%.

A Novel One-Step Fabricated, Droplet-Based Electrochemical Sensor for Facile Biochemical Assays

A simple, novel concept for the one-step fabrication of a low-cost, easy-to-use droplet-based electrochemical (EC) sensor is described, in which the EC reagents are contained in a droplet and the droplet assay is operated on a simple planar surface instead of in a complicated closed channel/chamber. In combination with an elegant carbon electrode configuration, screen-printed on a widely available polyethylene terephthalate (PET) substrate, the developed sensor exhibits a stable solution-restriction capacity and acceptable EC response, and thus can be used directly for the detection of different analytes (including ascorbic acid (AA), copper ions (Cu(2+)), 2'-deoxyguanosine 5'-triphosphate (dGTP) and ferulic acid (FA)), without any pretreatment. The obtained, acceptable linear ranges/detection limits for AA, Cu(2+), dGTP and FA are 0.5-10/0.415 mM, (0.0157-0.1574 and 0.1574-1.5736)/0.011 mM, 0.01-0.1/0.008 mM and 0.0257-0.515/0.024 mM, respectively. Finally, the utility of the droplet-based EC sensor was demonstrated for the determination of AA in two commercial beverages, and of Cu(2+) in two water samples, with reliable recovery and good stability. The applicability of the droplet-based sensor demonstrates that the proposed EC strategy is potentially a cost-effective solution for a series of biochemical sensing applications in public health, environmental monitoring, and the developing world.

A potentiostat featuring an integrator transimpedance amplifier for the measurement of very low currents--Proof-of-principle application in microfluidic separations and voltammetry

This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 μA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

A fully integrated microdevice for biobarcode assay based biological agent detection

An integrated microdevice, consisting of a micropump, a passive mixer, a magnetic separation chamber, and a microcapillary electrophoretic channel, was constructed for biobarcode assay based multiplex biological agent detection in a sample-to-answer-out manner within 30 min with high sensitivity.

Present state of microchip electrophoresis: state of the art and routine applications

Microchip electrophoresis (MCE) was one of the earliest applications of the micro-total analysis system (μ-TAS) concept, whose aim is to reduce analysis time and reagent and sample consumption while increasing throughput and portability by miniaturizing analytical laboratory procedures onto a microfluidic chip. More than two decades on, electrophoresis remains the most common separation technique used in microfluidic applications. MCE-based instruments have had some commercial success and have found application in many disciplines. This review will consider the present state of MCE including recent advances in technology and both novel and routine applications in the laboratory. We will also attempt to assess the impact of MCE in the scientific community and its prospects for the future.

Electromigrative separation techniques in forensic science: combining selectivity, sensitivity, and robustness

In this review we introduce the advantages and limitations of electromigrative separation techniques in forensic toxicology. We thus present a summary of illustrative studies and our own experience in the field together with established methods from the German Federal Criminal Police Office rather than a complete survey. We focus on the analytical aspects of analytes' physicochemical characteristics (e.g. polarity, stereoisomers) and analytical challenges including matrix tolerance, separation from compounds present in large excess, sample volumes, and orthogonality. For these aspects we want to reveal the specific advantages over more traditional methods. Both detailed studies and profiling and screening studies are taken into account. Care was taken to nearly exclusively document well-validated methods outstanding for the analytical challenge discussed. Special attention was paid to aspects exclusive to electromigrative separation techniques, including the use of the mobility axis, the potential for on-site instrumentation, and the capillary format for immunoassays. The review concludes with an introductory guide to method development for different separation modes, presenting typical buffer systems as starting points for different analyte classes. The objective of this review is to provide an orientation for users in separation science considering using capillary electrophoresis in their laboratory in the future.

From chip-in-a-lab to lab-on-a-chip: towards a single handheld electronic system for multiple application-specific lab-on-a-chip (ASLOC)

We present a portable, battery-operated and application-specific lab-on-a-chip (ASLOC) system that can be easily configured for a wide range of lab-on-a-chip applications. It is based on multiplexed electrical current detection that serves as the sensing system. We demonstrate different configurations to perform most detection schemes currently in use in LOC systems, including some of the most advanced such as nanowire-based biosensing, surface plasmon resonance sensing, electrochemical detection and real-time PCR. The complete system is controlled by a single chip and the collected information is stored in situ, with the option of transferring the data to an external display by using a USB interface. In addition to providing a framework for truly portable real-life developments of LOC systems, we envisage that this system will have a significant impact on education, especially since it can easily demonstrate the benefits of integrated microanalytical systems.