Tailoring 3D cell culture templates with common hydrogels

Hydrogels are the simplest and most widespread 3D cell culture materials, but turning these homogeneous substrates into biomimetic templates proves difficult. To this end, we introduce a generic solution compatible with the most biologically relevant and often frail materials. Here we take control of the chemical environment driving radical reactions to craft common gels with patterned light. In a simple microreactor, we harness the well-known inhibition of radicals by oxygen to enable topographical photopolymerization. Strikingly, by sustaining an oxygen rich environment, we can also induce hydrogel photo-scission, which turns out to be a powerful and generic subtractive manufacturing method. We finally introduce a flexible patterned functionalization protocol based on available photo-linkers. Using these tools on the most popular hydrogels, we tailored soft templates where cells grow or self-organize into standardized structures. The platform we describe has the potential to set a standard in future 3D cell culture experiments. SignificanceLight based, engineering of hydrogel should not be solely restricted to chemically modified materials. Indeed, many researchers rely on common hydrogels to organ-ize cells but lack the structuration and functionalization methods to develop standardized in vitro models with human-like properties. We unlock this limitation by providing a scalable toolbox that operates on widespread generic hydrogels or hydrogel blends such as PEG, Agar, or Matrigel. We crafted tailored 3D cell culture templates with these materials, growing and self-organizing cell lines and primary neurons in a controlled manner. More largely, we encourage all engineers with a knack for hydrogels but who are not experts in organic chemistry, to adopt our toolbox.