Visualizing Alpha-Fetoprotein Level in Undiluted Serum Based on Microfluidic Particle Accumulation

Alpha-fetoprotein (AFP) is an abundant plasma protein produced by the liver of the human fetus. When abnormally elevated in adult serum, its level can be an essential biomarker for various cancers. In addition, maternal AFP serum levels can be used to screen congenital disorders such as down syndrome and neural tube defects. Here, we report a portable method for visualizing AFP levels in serum. Magnetic microparticles (MMPs) and polystyrene microparticles (PMPs) are designed to bind with AFP simultaneously. By loading the particle solution into a microfluidic chip with a magnetic separator, unconnected PMPs can be separated and continue flowing forward until being trapped at a particle dam. Ultimately, the accumulation length of PMPs enables visualization of AFP levels. This device can be adapted to sensitive mode (70 min incubation) with a limit of detection (LOD) of 15.8 ng/ml and rapid mode (15 min incubation) with a LOD of 34.3 ng/ml in undiluted serum samples, providing a strategy for fast and visual quantitative detection of serum AFP.