Runtao Zhong

Determination of SARS-coronavirus by a microfluidic chip system.

We have developed a new experimental system based on a microfluidic chip to determine severe acute respiratory syndrome coronavirus (SARS‐CoV). The system includes a laser‐induced fluorescence microfluidic chip analyzer, a glass microchip for both polymerase chain reaction (PCR) and capillary electrophoresis, a chip thermal cycler based on dual Peltier thermoelectric elements, a reverse transcription‐polymerase chain reaction (RT‐PCR) SARS diagnostic kit, and a DNA electrophoretic sizing kit. The system allows efficient cDNA amplification of SARS‐CoV followed by electrophoretic sizing and detection on the same chip. To enhance the reliability of RT‐PCR on SARS‐CoV detection, duplex PCR was developed on the microchip. The assay was carried out on a home‐made microfluidic chip system. The positive and the negative control were cDNA fragments of SARS‐CoV and parainfluenza virus, respectively. The test results showed that 17 positive samples were obtained among 18 samples of nasopharyngeal swabs from clinically diagnosed SARS patients. However, 12 positive results from the same 18 samples were obtained by the conventional RT‐PCR with agarose gel electrophoresis detection. The SARS virus species can be analyzed with high positive rate and rapidity on the microfluidic chip system.

Simply and reliably integrating micro heaters/sensors in a monolithic PCR-CE microfluidic genetic analysis system

A novel fabrication process was presented to construct a monolithic integrated PCR‐CE microfluidic DNA analysis system as a step toward building a total genetic analysis microsystem. Microfabricated Titanium/Platinum (Ti/Pt) heaters and resistance temperature detectors (RTDs) were integrated on the backside of a bonded glass chip to provide good thermal transfer and precise temperature detection for the drilled PCR‐wells. This heater/RTD integration procedure was simple and reliable, and the resulting metal layer can be easily renewed when the Ti/Pt layer was damaged in later use or novel heater/RTD design was desired. A straightforward “RTD‐calibration” method was employed to optimize the chip‐based thermal cycling conditions. This method was convenient and rapid, comparing with a conventional RTD‐calibration/temperature adjustment method. The highest ramping rates of 14°C/s for heating and 5°C/s for cooling in a 3‐μL reaction volume allow 30 complete PCR cycles in about 33 min. After effectively passivating the PCR‐well surface, successful λ‐phage DNA amplifications were achieved using a two‐ or three‐temperature cycling protocol. The functionality and performance of the integrated microsystem were demonstrated by successful amplification and subsequent on‐line separation/sizing of λ‐phage DNA. A rapid assay for Hepatitis B virus, one of the major human pathogens, was performed in less than 45 min, demonstrating that the developed PCR‐CE microsystem was capable of performing automatic and high‐speed genetic analysis.

Organ-on-a-Chip: New Platform for Biological Analysis

Direct detection and analysis of biomolecules and cells in physiological microenvironment is urgently needed for fast evaluation of biology and pharmacy. The past several years have witnessed remarkable development opportunities in vitro organs and tissues models with multiple functions based on microfluidic devices, termed as “organ-on-a-chip”. Briefly speaking, it is a promising technology in rebuilding physiological functions of tissues and organs, featuring mammalian cell co-culture and artificial microenvironment created by microchannel networks. In this review, we summarized the advances in studies of heart-, vessel-, liver-, neuron-, kidney- and Multi-organs-on-a-chip, and discussed some noteworthy potential on-chip detection schemes.

Microfluidic device for integrated restriction digestion reaction and resulting DNA fragment analysis

A microfluidic system combining temperature‐controlled reactor, analyte delivery, chip electrophoresis (CE) separation, and fluorescence detection was developed, in which the heaters, resistance temperature detectors, enzymatic reactors, CE channels, and pneumatic valves/pumps were integrated onto a single glass–PDMS chip. The microdevice was used to perform the digestion reaction, followed by on‐line electrophoresis separation and detection of the resulting fragments with endonuclease BamHI and FokI as models. Pneumatic valves/pumps served not only for isolating the reaction region from the separation medium to prevent contamination, but also for delivering and quantitatively diluting the fluid from the reaction chamber to the CE section. Thus enzymatic reaction and electrophoresis separation could be insulated and connected as needed. A dynamic coating procedure with the use of PVP and mannitol was firstly adopted for glass–PDMS hybrid chip‐based DNA separations, leading to an improved separation efficiency with reproducible migration time and theoretical plates. The expected 263‐ and 287‐bp digestion products of BamHI and FokI were definitely verified by the size‐based electrophoretic separation and detection. The whole integrated reaction‐CE system can be manipulated in a simple manner with good reproducibility, which is expected to be applied in other on‐line analysis of various biochemical reactions.

A rapid, straightforward, and print house compatible mass fabrication method for integrating 3D paper‐based microfluidics

Three‐dimensional (3D) paper‐based microfluidics, which is featured with high performance and speedy determination, promise to carry out multistep sample pretreatment and orderly chemical reaction, which have been used for medical diagnosis, cell culture, environment determination, and so on with broad market prospect. However, there are some drawbacks in the existing fabrication methods for 3D paper‐based microfluidics, such as, cumbersome and time‐consuming device assembly; expensive and difficult process for manufacture; contamination caused by organic reagents from their fabrication process. Here, we present a simple printing–bookbinding method for mass fabricating 3D paper‐based microfluidics. This approach involves two main steps: (i) wax‐printing, (ii) bookbinding. We tested the delivery capability, diffusion rate, homogeneity and demonstrated the applicability of the device to chemical analysis by nitrite colorimetric assays. The described method is rapid (<30 s), cheap, easy to manipulate, and compatible with the flat stitching method that is common in a print house, making itself an ideal scheme for large‐scale production of 3D paper‐based microfluidics.