Immunoassay lab-on-a-chip

Abstract. Microfluidics is key to miniaturize bio-chemical and biomedical methods and processes into chip based technology. Basics of electrokinetic microfluidics will be reviewed first. Three types of lab-on-a-chip devices, PCR lab-on-a-chip, flow cytometer lab-on-a-chip and immunoassay lab-on-a-chip are discussed here. The working principle, key microfluidic processes and the current status of these lab-on-a-chip devices are reviewed. 

In the development of lab-on-a-chip technology, a key is to develop the ability to pump the liquids and transport sample/reagent molecules as well as biological cells in a microchannel network. This can be achieved by using the electroosmotic flow and electrophoresis. Mixing of different solutions and dispensing a specified amount of one solution from one microchannel into another microchannel are important to many microfluidic chips. There are extensive research works done in these areas [1]. Furthermore, precise control of temperature is often critical to on-chip biochemical reactions. In the following the PCR lab-on-a-chip, flow cytometer lab-on-a-chip and immunoassay lab-on-a-chip will be reviewed. 

Refer to the following entries within this encyclopedia for examples of applications Lab-on-a-Chip Devices for Drug Delivery, Lab-on-a-Chip Devices for Biodefense Applications, Lab-on-a-Chip Devices for Chemical Analysis, Lab-on-a-Chip Devices for Immunoassays, Lab-on-a-Chip Devices for Protein Analysis, PCR Lab-on-Chip Devices, Integrated Micro Devices for Biological Applications, Integrated Microfluidic Systems for Medical Diagnostics. 

The use of ELISA is broad and it finds applications in many biological laboratories over the last 30 years many tests have been developed and vahdated in different domains such as clinical diagnostics, pharmaceutical research, industrial control or food and feed analytics for instance. Our work has been to redesign the standard ELISA test to fit in a microfluidic system with disposable electrochemical chips. Many applications are foreseen since the biochemical reagents are directly amenable from a conventional microtitre plate to our microfluidic system. For instance, in the last 5 years, we have reported previous works with this concept of microchannel ELISA for the detection of thromboembolic event marker (D-Dimer) [4], hormones (TSH) [18], or vitamin (folic acid) [24], It is expected that similar technical developments in the future may broaden the use of electroanalytical chemistry in the field of clinical tests as has been the case for glucose monitoring. This work also contributes to the novel analytical trend to reduce the volume and time consumption in analytical labs using lab-on-a-chip devices. Not only can an electrophoretic-driven system benefit from the miniaturisation but also affinity assays and in particularly immunoassays with electrochemical detection. 

While a wide range of opportunities exist, such as environmental, clinical, and trace analysis, the principal application for labs-on-a-chip is in the analysis of biological samples. The miniaturized dimensions allow extremely small sample volumes to be analyzed, and a microchip format can allow chemical reaction, mixing, sample manipulation, and multiplexing to be performed. Single-cell analysis, immunoassays, protein and peptide separations, DNA analysis and sequencing, and polymerase chain reactions have all been performed on microchip devices [48]. 

S. Lutz, P. Lang, I. Malki, D. Mark, J. Ducree, R. Zengerle, and F. von Stetten, Lab-on-a-Chip Cartridge for Processing of Immunoassays with Integrated Sample Preparation, 2008. 

Chip immimoassay for whole blood Lab-on-a-chip immimoassay Microfluidic whole blood immunoassay... 

Our first successful effort at miniaturizing assays came with capillary-based immunoassays. More recently, we have developed several miniaturized immunoassays using paramagnetic microbeads to serve as the heterogeneous surface. Currently we are investigating different automated electrochemical im-munosensor systems with the aim of extending ECIA to lab-on-a-chip systems. In the remainder of this chapter, we wiU present the accomplishments in each of these areas. 

Reproduced from L. Ge, S. Wang, X. Song, S. Ge, J. Yu, 3D origami-based multifunction-integrated immunodevice low-cost and multiplexed sandwich chemiluminescence immunoassay on microfiuidic paper-based analytical device, Lab on a Chip 12 (2012) 3150-3158, with permission of The Royal Society of Chemistry. 

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