Hydrogels have been engineered for a variety of biomedical applications, including biosensing, drug delivery, cell delivery, and tissue engineering. The fabrication of hydrogels into nanoscale and microscale particles has been a subject of intense activity and promises to extend their range of applicability. As hydrogels are reduced in size, their interfacial properties represent an increasingly significant contribution to their function and behavior. Hydrogel microparticle-based biosensing and drug delivery platforms, for instance, requires delicate spatial control over the conjugation of biofunctional groups and network architecture, which impacts their mechanical properties and molecular permeability and diffusivity. Here, we demonstrate the ability to tune, with extraordinary precision, the interfacial properties of PEGDA particles generated in a droplet microfluidic device exploiting oxygen-inhibited photopolymerization. We demonstrate the broad utility of these engineered microgels by creating spherical particles with complex but predictable radial crosslinking density gradients. Immunoassays were conducted to examine the network properties of these particles, revealing a high degree of structural tenability, which, in turn, dictates macromolecule encapsulation and release profiles, as well as the presence of radial crosslinking gradients that impact the availability of functional groups.