Direct assessment of very-low-density lipoprotein by mass sensitive sensor with molecularly imprinted polymers

Abstract

Very-low-density lipoprotein (VLDL) contributes to the buildup of atherosclerotic plaque in the arteries and can lead to coronary heart disease. In clinical laboratory testing, the cholesterol content of VLDL (VLDL-C) cannot be assessed directly by the enzymatic colorimetric assay as it can for other lipoproteins, due to lack of a specific sample pretreatment technique. VLDL concentration relies on analyzing the endogenous triglycerides (TGs) bound in its particles and then converting to the VLDL-C estimate TGs/5. This estimation is valid for at least 12 h-fasted serum when exogenous TGs attached to chylomicrons (CMs) have been cleared from the circulation. A quartz crystal microbalance (QCM)-based sensor was generated using biomimetic sensing elements as a molecularly imprinted polymer (MIP) to directly measure actual VLDL. A novel VLDL-MIP was synthesized using methacrylic acid (MAA) and N-vinylpyrrolidone (VP) in the ratio 1:1 (v/v) as functional monomers in the presence of N, N′-(1,2-dihydroxyethylene) bis(acrylamide) (DHEBA) as a crosslinking agent. The VLDL-MIP sensor showed high sensitivity with a linear response from 2.5 mg dL−1 to 100 mg dL−1 of VLDL-C with a limit of detection at 1.5 mg dL−1. Recoveries of 96–103% were achieved when the VLDL-MIP sensor was used for VLDL assessment at 38–71 mg dL−1 concentrations. Repeatability and reproducibility of the sensor were very good with coefficients of variation at 1.63–4.74% and 4.25–9.04%, respectively. The sensor demonstrated low cross-reactivity with other lipoproteins; 6–7% of low-density lipoprotein (LDL) signals, 2–4% high-density lipoprotein (HDL), and 1% CMs compared to the signal of VLDL. Sensor results for 12 h-fasted serum and non-fasted serum correlated well with VLDL estimates TGs/5, with coefficients of determination (R2) at 0.9967 and 0.9932, respectively. This new sensor offers a new strategy for direct VLDL assessment from non-fasted serum without other sample pretreatment steps than dilution.