Mechanically Programmable DNA Hydrogel Microparticles for 3D Cellular Systems

Hydrogel microparticles (HMPs) are powerful tools to study and manipulate cellular behavior in 3D cell culture systems and animal models. Here, fully DNA-based HMPs are presented, whose material properties can be precisely tuned by sequence-programmable design of self-assembling DNA nanostructures. These DNA-HMPs offer control over size, stiffness, viscoelasticity and ligand presentation. They are formed by microfluidic encapsulation of two types of orthogonal DNA nanostars and a sequence-complementary DNA linker in water-in-oil droplets. By varying the valency of the DNA nanostar designs, tunable mechanical properties are achieved - spanning three orders of magnitude in Young's modulus from $30\mathrm{Pa}$ to $6.5k\mathrm{Pa}$ with distinct viscoelastic behavior. Click-chemistry based functionalization with the small fibronectin-derived peptide cyclic-RGD (c[RGD]) enables integration into fibroblast spheroids. DNA-HMPs are stably retained within the spheroids for several days and undergo remodeling, indicating active interactions between the cells and the DNA-HMPs. Combining programmable material properties and inherent biocompatibility of DNA with straightforward functionalization and stimuli-responsiveness, these DNA-HMPs represent a versatile tool to probe and manipulate tissue behaviors in 3D cell cultures.