Toward a Simplified Microfluidic Device for Ultra-Fast Genetic Analysis with Sample-In/Answer-Out Capability: Application to T-Cell Lymphoma Diagnosis

Current Trends of Microfluidic Single-Cell Technologies

The investigation of human disease mechanisms is difficult due to the heterogeneity in gene expression and the physiological state of cells in a given population. In comparison to bulk cell measurements, single-cell measurement technologies can provide a better understanding of the interactions among molecules, organelles, cells, and the microenvironment, which can aid in the development of therapeutics and diagnostic tools. In recent years, single-cell technologies have become increasingly robust and accessible, although limitations exist. In this review, we describe the recent advances in single-cell technologies and their applications in single-cell manipulation, diagnosis, and therapeutics development.

Microfluidic enzymatic DNA extraction on a hybrid polyester-toner-PMMA device

A polyester-toner-poly(methyl methacrylate) (PMMA) hybrid microdevice, which centrifugally introduces EA1 enzyme to a buccal swab for rapid DNA extraction.

Paper-based sample-to-answer molecular diagnostic platform for point-of-care diagnostics

Nucleic acid testing (NAT), as a molecular diagnostic technique, including nucleic acid extraction, amplification and detection, plays a fundamental role in medical diagnosis for timely medical treatment. However, current NAT technologies require relatively high-end instrumentation, skilled personnel, and are time-consuming. These drawbacks mean conventional NAT becomes impractical in many resource-limited disease-endemic settings, leading to an urgent need to develop a fast and portable NAT diagnostic tool. Paper-based devices are typically robust, cost-effective and user-friendly, holding a great potential for NAT at the point of care. In view of the escalating demand for the low cost diagnostic devices, we highlight the beneficial use of paper as a platform for NAT, the current state of its development, and the existing challenges preventing its widespread use. We suggest a strategy involving integrating all three steps of NAT into one single paper-based sample-to-answer diagnostic device for rapid medical diagnostics in the near future.

Applications of microfluidics for molecular diagnostics

Diagnostic assays implemented in microfluidic devices have developed rapidly over the past decade and are expected to become commonplace in the next few years. Hundreds of microfluidics-based approaches towards clinical diagnostics and pathogen detection have been reported with a general theme of rapid and customizable assays that are potentially cost-effective. This chapter reviews microfluidics in molecular diagnostics based on application areas with a concise review of microfluidics in general. Basic principles of microfabrication are briefly reviewed and the transition to polymer fabricated devices is discussed. Most current microfluidic diagnostic devices are designed to target a single disease, such as a given cancer or a variety of pathogens, and there will likely be a large market for these focused devices; however, the future of molecular diagnostics lies in highly multiplexed microfluidic devices that can screen for potentially hundreds of diseases simultaneously.

Nanocapillary electrophoretic electrochemical chip: towards analysis of biochemicals released by single cells

A novel nanocapillary electrophoretic electrochemical (Nano-CEEC) chip has been developed to demonstrate the possibility of zeptomole-level detection of neurotransmitters released from single living cells. The chip integrates three subunits to collect and concentrate scarce neurotransmitters released from single PC-12 cells, including a pair of targeting electrodes for single cells captured by controlling the surface charge density; a dual-asymmetry electrokinetic flow device for sample collection, pre-concentration and separation in a nanochannel; and an online electrochemical detector for zeptomole-level sample detection. This Nano-CEEC chip integrates a polydimethylsiloxane microchannel for cell sampling and biomolecule separation and a silicon dioxide nanochannel for sample pre-concentration and amperometric detection. The cell-capture voltage ranges from 0.1 to 1.5 V with a frequency of 1-10 kHz for PC-12 cells, and the single cell-capture efficiency is optimized by varying the duration of the applied field. All of the processes, from cell sampling to neurotransmitter detection, can be completed within 15 min. Catecholamines, including dopamine and norepinephrine (noradrenaline) released from coupled single cells, have been successfully detected using the Nano-CEEC chip. A detection limit of 30-75 zeptomoles was achieved, which is close to the levels released by a single neuron in vitro.

Nucleic acid extraction techniques and application to the microchip

As recently as the early 1990s, DNA purification was time-consuming, requiring the use of toxic, hazardous reagents. The advent of solid phase extraction techniques and the availability of commercial kits for quick and reliable DNA extraction has relegated those early techniques largely to the history books. High quality DNA can now be extracted from whole blood, serum, saliva, urine, stool, cerebral spinal fluid, tissues, and cells in less time without sacrificing recovery. Having achieved such a radical change in the methodology of DNA extraction, focus has shifted to adapting these methods to a miniaturized system, or "lab-on-a-chip" (A. Manz, N. Graber and H. M. Widmer, Sens. Actuators, B, 1990, 1, 244-248). Manz et al.'s concept of a "miniaturized total chemical analysis system" (microTAS) involved a silicon chip that incorporated sample pretreatment, separation and detection. This review will focus on the first of these steps, sample pretreatment in the form of DNA purification. The intention of this review is to provide an overview of the fundamentals of nucleic acid purification and solid phase extraction (SPE) and to discuss specific microchip DNA extraction successes and challenges. In order to fully appreciate the advances in DNA purification, a brief review of the history of DNA extraction is provided so that the reader has an understanding of the impact that the development of SPE techniques have had. This review will highlight the different methods of nucleic acid extraction (Table 1), including relevant citations, but without an exhaustive summary of the literature. A recent review by Wen et al. (J. Wen, L. A. Legendre, J. M. Bienvenue and J. P. Landers, Anal. Chem., 2008, 80, 6472-6479) covers solid phase extraction methods with a greater focus on their incorporation into integrated microfluidic systems.