An integrated microfluidic concentration gradient generator for mechanical stimulation and drug delivery

Mechanical stimuli, including fluid shear stress, osmotic pressure gradient, and extracellular matrix stiffness, significantly affect cellular interactions with drugs in biological structures. This paper introduces an integrated concentration gradient generator (CGG) capable of providing cell monolayers with these stimuli and demonstrates its design, fabrication, and quantification procedures. The proposed multi-layer chip consists of a CGG integrated with a membrane-based cell culture chamber (MCCC) and two bubble trappers for removal of micro-bubbles. The CGG provides cultured cells in the MCCC with four different concentrations of desirable inlet drug/chemical reagents. The MCCC is able to impose adjustable shear stresses, as well as osmotic pressure gradients on cell monolayers. The stiffness of the extracellular matrix (ECM) is also accommodating by utilizing a proper membrane in the MCCC. A numerical simulation based on the finite element method (FEM) is employed to design and optimize the integrated device, and then, the chip's performance is quantified using the experimental data. Finally, the biocompatibility of the proposed device is investigated by dynamic culturing of human lung cancer cells (A549 cell line) on the chip.