Microfluidic devices for embryonic and larval zebrafish studies.

Zebrafish or Danio rerio is an established model organism for studying the genetic, neuronal and behavioral bases of diseases and for toxicology and drug screening. The embryonic and larval stages of zebrafish have been used extensively in fundamental and applied research due to advantages offered such as body transparency, small size, low cost of cultivation and high genetic homology with humans. However, the manual experimental methods used for handling and investigating this organism are limited due to their low throughput, labor intensiveness and inaccuracy in delivering external stimuli to the zebrafish while quantifying various neuronal and behavioral responses. Microfluidic and lab-on-a-chip devices have emerged as ideal technologies to overcome these challenges. In this review paper, the current microfluidic approaches for investigation of behavior and neurobiology of zebrafish at embryonic and larval stages will be reviewed. Our focus will be to provide an overview of the microfluidic methods used to manipulate (deliver and orient), immobilize and expose or inject zebrafish embryos or larvae, followed by quantification of their responses in terms of neuron activities and movement. We will also provide our opinion in terms of the direction that the field of zebrafish microfluidics is heading toward in the area of biomedical engineering.

Lab-on-a-plate: extending the functionality of MALDI-MS and LDI-MS targets.

We review the literature that describes how (matrix-assisted) laser desorption/ionization (MA)LDI target plates can be used not only as sample supports, but beyond that: as functional parts of analytical protocols that incorporate detection by MALDI-MS or matrix-free LDI-MS. Numerous steps of analytical procedures can be performed directly on the (MA)LDI target plates prior to the ionization of analytes in the ion source of a mass spectrometer. These include homogenization, preconcentration, amplification, purification, extraction, digestion, derivatization, synthesis, separation, detection with complementary techniques, data storage, or other steps. Therefore, we consider it helpful to define the "lab-on-a-plate" as a format for carrying out extensive sample treatment as well as bioassays directly on (MA)LDI target plates. This review introduces the lab-on-plate approach and illustrates it with the aid of relevant examples from the scientific and patent literature.

Capacitively coupled contactless conductivity detection for microseparation techniques - recent developments.

An overview of the developments of capacitively coupled contactless conductivity detection in CE and related techniques over approximately the last 2 years is given. The method has seen strong growth, and diverse new applications are being reported. Besides more advanced techniques on conventional capillaries, these include further developments of detection on lab-on-chip devices as well as in miniaturized chromatographic systems and some methods not involving separations. An increasing number of reports are based on the now readily available commercial detectors, but, while few publications on fundamental studies have appeared recently, interesting new approaches on creating low cost devices have also appeared.

Toner and paper-based fabrication techniques for microfluidic applications.

The interest in low-cost microfluidic platforms as well as emerging microfabrication techniques has increased considerably over the last years. Toner- and paper-based techniques have appeared as two of the most promising platforms for the production of disposable devices for on-chip applications. This review focuses on recent advances in the fabrication techniques and in the analytical/bioanalytical applications of toner and paper-based devices. The discussion is divided in two parts dealing with (i) toner and (ii) paper devices. Examples of miniaturized devices fabricated by using direct-printing or toner transfer masking in polyester-toner, glass, PDMS as well as conductive platforms as recordable compact disks and printed circuit board are presented. The construction and the use of paper-based devices for off-site diagnosis and bioassays are also described to cover this emerging platform for low-cost diagnostics.

Liquid chromatography on chip.

LC is one of the most powerful separation techniques as illustrated by its leading role in analytical sciences through both academic and industrial communities. Its implementation in microsystems appears to be crucial in the development of mu-Total Analysis System. If electrophoretic techniques have been widely used in miniaturized devices, LC has faced multiple challenges in the downsizing process. During the past 5 years, significant breakthroughs have been achieved in this research area, in both conception and use of LC on chip. This review emphasizes the development of novel stationary phases and their implementation in microchannels. Recent instrumental advances are also presented, highlighting the various driving forces (pressure, electrical field) that have been selected and their respective ranges of applications.

[Microchip electrochromatography: the latest developments and applications].

This review summarizes recent developments and applications of microchip electrochromatography (microCEC) mainly in the past five years between 2005 and 2009 with a focus on column technologies. In addition, some new improvements in the chip design and fabrication, sample preconcentration, electroosmotic flow control as well as mechanisms that govern electrochromatographic separation are described and reviewed. The features and limitations of several practical aspects of their applications are highlighted.

Chip-mass spectrometry for glycomic studies.

The introduction of micro- and nanochip front end technologies for electrospray mass spectrometry addressed a major challenge in carbohydrate analysis: high sensitivity structural determination and heterogeneity assessment in high dynamic range mixtures of biological origin. Chip-enhanced electrospray ionization was demonstrated to provide reproducible performance irrespective of the type of carbohydrate, while the amenability of chip systems for coupling with different mass spectrometers greatly advance the chip/MS technique as a versatile key tool in glycomic studies. A more accurate representation of the glycan repertoire to include novel biologically-relevant information was achieved in different biological sources, asserting this technique as a valuable tool in glycan biomarker discovery and monitoring. Additionally, the integration of various analytical functions onto chip devices and direct hyphenation to MS proved its potential for glycan analysis during the recent years, whereby a new analytical tool is on the verge of maturation: lab-on-chip MS glycomics. The achievements until early beginning of 2007 on the implementation of chip- and functional integrated chip/MS in systems glycobiology studies are reviewed here.

Chemiluminescent enzyme immunoassays: a review of bioanalytical applications.

This review gives an overview of the most recent and innovative developments in the field of chemiluminescent immunoassays through carefully selected examples. First, assays using microtiter plates for high-throughput or multiplexed assays aiming to achieve more complex assays through the multiplication of parameters per wells will be described. Systems will then be presented that have been recently developed, motivated by integration and miniaturization of existing immunoassays in more complex experimental setups. Finally, enhanced-performance chemiluminescent biochips, based on chemiluminescent reaction intensification, will be introduced.

Proteome-on-a-chip: mirage, or on the horizon?

Proteomics has emerged as the next great scientific challenge in the post-genome era. But even the most basic form of proteomics, proteome profiling, i.e., identifying all of the proteins expressed in a given sample, has proven to be a demanding task. The proteome presents unique analytical challenges, including significant molecular diversity, an extremely wide concentration range, and a tendency to adsorb to solid surfaces. Microfluidics has been touted as being a useful tool for developing new methods to solve complex analytical challenges, and, as such, seems a natural fit for application to proteome profiling. In this review, we summarize the recent progress in the field of microfluidics in four key areas related to this application: chemical processing, sample preconcentration and cleanup, chemical separations, and interfaces with mass spectrometry. We identify the bright spots and challenges for the marriage of microfluidics and proteomics, and speculate on the outlook for progress.

Future lab-on-a-chip technologies for interrogating individual molecules.

Advances in technology have allowed chemical sampling with high spatial resolution and the manipulation and measurement of individual molecules. Adaptation of these approaches to lab-on-a-chip formats is providing a new class of research tools for the investigation of biochemistry and life processes.

Enzymatic microreactors in chemical analysis and kinetic studies.

The fields of application of microreactors are becoming wider every year. A considerable number of papers have been published recently reporting successful application of enzymatic microreactors in chemistry and biochemistry. Most are devices with enzymes immobilized on beads or walls of microfluidic channels, whilst some use dissolved enzymes to run a reaction in the microfluidic system. Apart from model systems, mostly with glucose oxidase, horseradish peroxidase and alkaline phosphatase, the principal fields of application of microreactors are tryptic digestion of proteins and polymerase chain reaction in automated analyses of proteomic and genetic material, respectively. Enzymatic microreactors also facilitate characterization of enzyme activity as a function of substrate concentration, and enable fast screening of new biocatalysts and their substrates. They may constitute key parts of lab-on-a-chip and muTAS, assisting the analysis of biomolecules. This review provides systematic coverage of examples of reports on enzymatic microreactors published recently, as well as relevant older papers.

Micro- and nanotechnology in cell separation.

This review describes recent work in cell separation using micro- and nanoscale technologies. These devices offer several advantages over conventional, macroscale separation systems in terms of sample volumes, low cost, portability, and potential for integration with other analytical techniques. More importantly, and in the context of modern medicine, these technologies provide tools for point-of-care diagnostics, drug discovery, and chemical or biological agent detection. This review describes work in five broad categories of cell separation based on (1) size, (2) magnetic attraction, (3) fluorescence, (4) adhesion to surfaces, and (5) new emerging technologies. The examples in each category were selected to illustrate separation principles and technical solutions as well as challenges facing this rapidly emerging field.

Multiplexed microsphere diagnostic tools in gene expression applications: factors and futures.

Microarrays have received significant attention in recent years as scientists have firstly identified factors that can produce reduced confidence in gene expression data obtained on these platforms, and secondly sought to establish laboratory practices and a set of standards by which data are reported with integrity. Microsphere-based assays represent a new generation of diagnostics in this field capable of providing substantial quantitative and qualitative information from gene expression profiling. However, for gene expression profiling, this type of platform is still in the demonstration phase, with issues arising from comparative studies in the literature not yet identified. It is desirable to identify potential parameters that are established as important in controlling the information derived from microsphere-based hybridizations to quantify gene expression. As these evolve, a standard set of parameters will be established that are required to be provided when data are submitted for publication. Here we initiate this process by identifying a number of parameters we have found to be important in microsphere-based assays designed for the quantification of low abundant genes which are variable between studies.