Development of microfluidic devices using 3D printing for cell culture and drug testing

Cell culturing and in vitro testing are the cornerstone investigations that allowed the development of medicine and biology in the last century. Nevertheless, the most of studies requires a series of operations that involve manual handling of liquid substances through pipetting devices. Those, in addition to being highly time-consuming, are accompanied by the possibility of errors related to the manual dexterity and experience of the operator. Therefore, it clearly emerged the necessity to develop smart biomedical devices that may help end-users to save time and enable more controlled procedure. Automatic pipetting helped to face this problem, but on the other hand the complexity of in-vitro studies still request considerable human efforts. In this context, multiwell plates, also known as microwell plates or multiwells, are the basic tools for performing such experiments. Smart multiwell systems, in which different wells are connected by microfluidic channels, would allow for the reduction of manual operations. In this way, the manual pipetting of samples into the wells is completely replaced by the presence of a microfluidic system that connects the various wells and is, in turn, connected to a pumping system. This allows for the automation of cell proliferation and/or drug response tests, optimizing execution times and minimizing operator intervention. Nevertheless, the fabrication of these smart devices is mainly performed by injection molding, i.e. defined geometries are produced, which limit the freedom of automation of experiments. To make a further step in this direction, the aim of this thesis is to produce a smart plate using additive manufacturing (AM) techniques, which allow the creation of complex geometries from a CAD model which can be user-defined. Specifically, for the development of this device, Digital Light Processing (DLP) was chosen. DLP is a technique that belongs to the vat photopolymerization class, where polymerization of the resin in the vat is induced through irradiation (UV or visible light) and allows high precision and superior complexity when compared to other AM technologies. For the fabrication of the smart plate, two different resins were selected: one that promotes cell adhesion, poly(ethylene glycol) diacrylate 250 (PEGDA 250), and one that inhibits it without inducing cytotoxic effects (TEGORad 2800). Specifically, the base of the object and the bottom of the wells were made with PEGDA, while the channels and wells were made with TEGORad. Once the device was obtained, microfluidic simulations were conducted using Comsol software, which allowed to simulate various flow rates permitted by the two-head peristaltic pump. Simulation tests were then reproduced in real experiments to verify the reliability of these tests. Finally, studies were conducted for verifying the cytocompatibility of the material and biological studies on cell viability. For the cell viability study, tests were conducted with three different cell types: human fibroblasts (HFF1), keratinocytes (HaCaT), and endothelial cells (EC). The successful implementation of this strategy opens to new possibilities of automated, large-scale studies, leaving at the same time the design-of-experiment freedom to investigators.