Hydrogel microwells with customizable bottom design: A one-step approach to spheroid formation

Abstract

Conical microwells featuring a variety of bottom-shape features have received increased recognition because of their enhanced surface characteristics that improve the in vitro-in vivo correlation in a wide range of biological applications, such as in three-dimensional cell culture models, specifically cell spheroidal formation, and drug screening. Conventional and microfluidics-based emerging fabrication techniques for the formation of such conically shaped microwells with uniform spatiotemporal control require complex multistep procedures and costly equipment, or they face challenges in developing slanted V-shaped well bottoms. Herein, we developed a microfluidics-based method to produce three-dimensional microwells with slanted V-shaped well bottoms by exploring the 3D-shape tuning ability using a non-uniform photolithographic technique (NUPL), through a variation in the UV light intensity profile induced by the presence of magnetic nanoparticles, which makes an opaque precursor solution. We also characterize the change in the microwell's bottom profile through variation of UV dose. Finally, the effects of conical shape tuning parameters, that is, the non-uniformity of UV light intensity and aspect ratio (diameter/height), on the microwell depth and bottom shape is investigated. Using NUPL, we demonstrate the facile and single-step synthesis of conical microwells with highly slanted sidewalls that are used to create chondrocyte spheroids as a proof of concept.