Doctor of Philosophy (PhD)


Department of Chemistry

Document Type



Globally cell culture is an $18.98 billion industry as of 2020, with an 11.6 percent annual growth rate. Drug discovery has an estimated worth of $69.8 billion in 2020 and is predicted to grow to $110.4 billion by 2025. Three-dimensional (3D) cell culture of cancer cells is one of the rapidly growing felids since it better recapitulates in vivo conditions compared to two-dimensional (2D) models. However, it is challenging to grow 3D tumor spheroids outside the body, and some of the existing technology can generate these spheroids outside the human body but poorly mimic in vivo tumor models. Therefore, there is a greater need for developing new materials, microtools for 3D cell culture, and drug discovery applications.

One of the ways to generate in vivo like 3D tumor spheroid is to utilize soft scaffold materials, commonly known as hydrogels but there are few of these hydrogels in the market. In this work, a biocompatible and biodegradable thiol-acrylate (TA) hydrogel was synthesized from two low-cost monomers (ETTMP 1300 and PEGDA 700) that act as scaffolds to support in vitro 3D cell culture and microfluidic applications. The hydrogel formulations with a thiol-to-acrylate molar ratio of 1.05 were found to be optimal for both 2D and 3D cultures and seen to facilitate spheroid growth in a 96-well plate. However, the low throughput, difficulties in controlling the size, and high genetic heterogeneity within the generated spheroid from 96-well plates lead to investigatigation droplet microfluidic devices, which offer a promising alternative to 96-well plates and address many of these issues. A two-layer polydimethylsiloxane (PDMS) based microfluidic device was developed. Spheroids were generated by encapsulating cells in novel TA hydrogel scaffold droplets and cultured for seven days in the device under continuous media flow using a customized gravity-driven system to eliminate the need for syringe pumps. This device can generate spheroids in a high throughput manner with excellent control over spheroid size, and drug susceptibility study can be done. Besides these applications, hydrogel has also been used to build a microfluidic gradient generator to study cellular migration, growth, and drug response in a variety of biological systems. One form of common device combines a hydrogel and PDMS to create 'flow-free' gradients; however, its need for negative flow or external clamps to maintain fluid-tight seals between the two layers has limited its use. Therefore, an alternative two-layer flow-free microfluidic gradient generator was developed using thiol-acrylate chemistry where two layers formed fluid-tight channels due to a strong adhesive interaction between the two layers. The diffusion of molecules through the TAMR/H system was confirmed experimentally and chemorepulsive response of a motile strain of GFP-expressing E. coli was studied.



Committee Chair

Pojman, John A.