Microchip-based small, dense low-density lipoproteins assay for coronary heart disease risk assessment

Small, dense low-density lipoprotein (sdLDL) has been accepted as an emerging cardiovascular risk factor, and there has been an increasing interest in analytical methods for sdLDL profiling for diagnosis. Serum sdLDL may be measured by different laboratory techniques, but all these methods are laborious, time-consuming, and costly. Recently, we have demonstrated that a low-temperature bonding of quartz microfluidic chips for serum lipoproteins analysis (Zhuang, G., Jin, Q., Liu, J., Cong, H. et al., Biomed. Microdevices 2006, 8, 255-261). In contrast to this previous study, we chose SDS as anionic surfactant to modify both lipoproteins and the channel surface to minimize lipoprotein adsorption and improve the resolution of lipoprotein separation. Two major LDL subclass patterns including large, buoyant LDL (lLDL), sdLDL, and high-density lipoprotein (HDL) were effectively separated with high reproducibility. RSD values of the migration time (min) and peak areas of standard LDL and HDL were 6.28, 4.02, 5.02, and 2.5%, respectively. Serum lipoproteins of 15 healthy subjects and 15 patients with coronary heart disease (CHD) were separated by microchip CE. No peaks of sdLDL were detected in serum samples of healthy subjects while sdLDL fractional peaks were observed in patients' entire serum samples. These results suggested that the microchip-based sdLDLs assay was a simple, rapid, and highly efficient technique and significantly improved the analysis of CHD risk factors.