RESUMO
A multi-functional microfluidic chip with multi-orifice flow fractionation ( MOFF) and magnetic capture technique was developed to specifically separate and capture the HepG2 cells in artificial samples. The chip contained a glass substrate and a polydimethylsiloxane ( PDMS) microchannel cover plate. The PDMS cover plate consisted of 3 injection channels of 10-mm-long, a MOFF separation zone and a hexagonal cavity cell enrichment-detection zone. Among which, the MOFF separation zone had a total length of 20 mm and was consisted of 80 semi-rhombic shrinkage / expansion units with a length of 0. 18 mm, a depth of 50 μm, a shrinkage area width of 0. 06 mm, and an expansion area of 0. 20 mm. The angle between each group of shrinkage / expansion units was 103. 0°. In this experiment, HepG2-blood cell suspension was used as the sample. Based on the principle that the magnetic bead surface-modified c-Met antibody could specifically bind to HepG2 cells, an immunomagnetic bead ( Anti-MNCs) suspension at a concentration of 50 μg / mL was prepared by surface carboxylated beads, EDC (1 mg / mL), NHS (1 mg / mL) and c-Met antibody. Under the optimized flow rate (50 μL/ min), a few HepG2 in suspension samples were efficiently captured at the detection zone of chip via a magnetic field; the carbon quantum dots were prepared by microwave heating with citric acid and thiourea to label HepG2 cells which achieved in-situ fluorescence visualization of captured HepG2. Cells captured in the chip detection area were counted by microscope. The capture rate of HepG2 cells was 88. 5% ±6. 7% (106 blood cells and 10 HepG2 cells per 500 μL). The results demonstrated that the developed multifunctional microfluidic chip may serve as a promising tool for separation and capture of tumour cells.