Investigation of diffusion of biomolecules and cells in microfluidic chips

Microfluidic systems has a wide range of work in many areas such as analytical chemistry, drug discovery and development research, diagnostic kits, point-of-care testing, enzymatic-chemical synthesis, determination of biological molecules, organ-on-a-chip in the medical and life sciences applications. Microfluidic chips have recently received much attention, due to their advantage of being able to produce fast results with very low volumes, high efficiency and reproducibility. The main objective of microfluidic technologies is to provide innovative and low cost microfluidic devices to the biotechnology, biomedical and pharmaceutical industries. Therefore, it is very important to understand the transport events of cells and biomolecules in microfluidic systems. In this thesis study, we investigated the diffusion of substrate molecules in a microfluidic chip which can perform biocatalytic transformations of saponin glycosides and carried out mathematical modelling. For this purpose, the substrate solution were fed to the system at a certain concentration in time with the flow and the output currents were collected. By analyzing the output substrate concentrations, the hydrodynamic diffusion coefficients of the molecules were determined by using the Fick's law diffusion model. Then, mathematical model equivalents which constitute the model dynamics of the system and the model for scale-up were determined. In addition to the study of diffusion of biomolecules in microfluidic chips, a spheroid-based, three-dimensional (3D) lung-on-a-chip platform that simulates in vivo conditions was developed and the effect of potential drug molecule on the lung carcinoma cell line formed within the spheroid structures was investigated. For this, the cytotoxic activity of the potential drug on the A549 lung carcinoma and MRC-5 lung fibroblast cell lines was determined, and then the efficiency of the drug in in vivo 3D microfluidic cell culture systems which was a bridge between living tissue was investigated. In order to create a three-dimensional structure in the microfluidic chips, a matrix-based spheroid culture was carried out. Morphologies of spheroids were observed by light microscopy depending on time and spheroid size and counts were determined by ImageJ analysis. In addition, cell viability of spheroids was investigated by live & dead fluorescent staining test at the end of the experiment. In this study, the 3D lung spheroid culture developed on the lung-on-a-chip platform has contributed to the quantitative and qualitative understanding of the cell-cell interaction effect mimicking the cancer microenvironment as well as the well-organized spheroid formation.