Microfluidic Chip-based Immunosensor

Microfluidic technologies is drawing increasing attention for which they offer a number of useful capabilities:very little samples and reagents consumption; low cost; separation and detection samples with high resolution and sensitivity; shortened time for analysis and so on. Due to all these advantages, microfluidic chips have been used in relevant application areas such as clinical, environmenta, and food analysis while other areas, such as molecular analysis (DNA and RNA), forensics, biodefense. Immunoassay system, especially the enzyme-linked immunosorbent assay (ELISA) method, has become one of the most widely used methods for the determination of various important biomarkers in clinical diagnosis. Compared with conventional immunoassay, microchip-based immunoassay has more exciting applications in clinical and biochemical analysis, especially in point-of-care testing (POCT). The conventional heterogeneous immunoassay requires a relatively long assay time and large quantities of expensive antibody reagents as well as involves troublesome liquid-handling procedures. As we know, coronary heart disease (CHD) which is drawing increasing attention is threatening more and more people's lives nowadays. Conventionally, the diagnosis of CHD dominantly depends on the number of risk factors, the typical symptom in clinical and cardiograph. The raise of low density lipoprotein (LDL) and decrease of high density lipoprotein (HDL) are both the risk factors for CHD. Although the LDL cholesterol has served us well in clinic and in fact has resulted a lot of advance in prevention of coronary heart disease. But measuring LDL cholesterol is not a measurement of LDL particle number. There is substantial clinical evidence that apoB and apoA I may provide a more trust-worthy cardiovascular risk measurement than LDL cholesterol, and apoB and apoA I do reflect better assessments of total atherogenic burden to the vascular system.1. Introduction of microfluidics, immunoassay and coronary heart diseaseA review on Lab-on-a-chip is presented. Microfluidics is very important in analytical area, and it has a lot of advantages. coronary heart disease is one of the most dangerous disease that threaten our lives. Chip-based immunoassay on biomarkers of coronary heart disease can help us to predict it and it has potential values in clinical analysis. 2. Apolipoprotein B100 analysis in microchip with electrochemical detectionApolipoprotein B100 (apoB) is the major protein of the cholesterol-rich low-density lipoprotein (LDL). Measuring LDL or VLDL cholesterol may not reflect the actual number of these atherogenic particles and apoB does reflect a better assessment of total athrogenic burden to the vascular system making apoB analysis particularly important. In this work, a simple and sensitive method has been developed to determine picoliter apoB-100s using the PMMA microfluidic chip coupled with three-electrode electrochemical detection system. After the PMMA microchannel being modified with poly(ethleneimine) (PEI) which contains abundant NH2 groups, the apoB-100 antibodies can be easily absorbed on the surface of the microchannel. Afterwards, alkaline phosphatase (ALP) is labeled in this immunosensor and apoB-100 can be detected by ELISA method. The PEI modification has been characterized by ATR-FTIR. This method performs very well with a detectable linear concentration range of 1-800 pg mL-1 and a detection limit of 1 pg mL-1. A real serum sample has further been detected by this microchip-based immunoassay method. The result shows that this kind of method is practicable and has the potential application in clinical analysis and diagnosis.3. Apolipoprotein AⅠanalysis in microchip with electrochemical detectionApolipoprotein AⅠ(apoAⅠ) is the major protein of high-density lipoprotein (HDL) and is one biomarkers of CHD. In this work, a simple and sensitive method has been developed to determine picoliter apoAⅠusing the PMMA microfluidic chip coupled with electrochemical detection system. The results show that this kind of method is practicable and has the potential application in clinical analysis and diagnosis.