Zwitterionic Microgel Scaffolds Support Matrix Accumulation by Regulating Protein Adsorption

Substrate charge influences protein adsorption, cell adhesion, and biocompatibility. Hydrogels formed from zwitterionic polymers, which possess balanced cationic and anionic groups, are advantageous due to their high levels of hydration, ability to resist non-specific protein adsorption, high biocompatibility, and non-immunogenicity. Compared to bulk hydrogels, microgel-based scaffolds enhance cell proliferation, migration, cell-matrix interaction, and nutrient transport. However, previous studies using zwitterionic microgel scaffolds have not fully characterized how substrate charge influences cell behaviors such as viability, spreading, and extracellular matrix (ECM) deposition. In this study, microgels using polymers with various functional groups that imbue distinct substrate charges and emulsion-based microfluidics are fabricated. Charged proteins adsorbed more to substrates with an opposing charge. When seeding human mesenchymal stromal cells (MSCs) into microgel annealed scaffolds, we observed differences in cell viability and cell spreading as a function of substrate charge, with zwitterionic polymers best promoting viability and spreading. Lastly, it is found that zwitterionic microgel scaffolds maintained ECM accumulation in inflammatory conditions, while ECM deposition decreased in scaffolds formed from nonionic or negatively charged polymers. These data demonstrate that substrate charge influences protein adsorption, MSC adhesion, and subsequent ECM deposition, highlighting its importance in designing macroporous scaffolds for tissue engineering.