(649c) Enhanced Microfluidic Immunomagnetic Separation Based on Microfabricated Patterns from Ferromagnetic Nanoparticles

Isolation of specific cells from complex biological samples has been of growing interest in cellular studies, disease and medicine researches. Immunomagnetic separation, which is the use of antibody functionalized magnetic beads to bind specific proteins on target cells and separate cells by external magnetic field, is a widely used method for their simple operation and high isolation specificity. Microfluidics, which allows tiny quantities of liquids to be controlled and manipulated, provides a powerful platform for sorting of small amount of cells from heterogeneous cell mixtures, especially when the sample is rare and precious. However, low magnetic force generated by limited magnetic field gradient of external magnet has been a big obstacle for enhancement of current cell sorters. Low flow rates were required for continuous microfluidic separation, which brought the problem of low throughput and non-specific cell absorption (e.g. low purity of isolated cells). Embedding a pattern of magnetic material on the bottom of a microfluidic channel is way to concentrate field lines from an external magnetic field source. However, current methods involve complicated fabrications that require advanced facilities, trained personal and high-cost materials. In our study, we proposed a simple microfluidic device containing ferromagnetic structure for cell capture. The ferromagnetic pattern was formed from magnetic nanoparticle suspension. The fabrication needs basic soft lithography instruments, cost-effective materials and simple operation only. The dimension of the pattern is controllable and reproducible. We tested the ability of our microfluidic channels in capturing magnetic beads coated RAW 264.7 cells, and found that ferromagnetic embedded channel performed up to over 4 times higher capture rate compared to no patterned channel. Mathematical models were built to simulate the magnetic field distribution inside channels, which matched the experimental data very well. We envision that our device will be useful for sorting primary cell samples from scarce sources (e.g. animals, human).