Hydrogel-swelling behavior translated into improved protein loading and release capacities. (A) Loading effciency of anti-TNF-α antibody in P(MAA-g-EG) and P(MAA-co-NVP) microparticles (≤75 μm) formulated with TEGDMA, PEGDMA-400, and PEGDMA-1000 as cross-linkers. Hydrogel microparticles were incubated in an anti-TNF-α solution in PBS (pH 7.4), and 1 N HCl was added to the solution to lower the pH and collapse the microparticles. (B) Anti-TNF-α antibody release from P(MAA-g-EG) hydrogel microparticles synthesized with different cross-linkers: PEGDMA-1000, PEGDMA-400, and TEGDMA. Protein release from the microparticles was studied under dynamic pH conditions (from pH 3.0 to pH 7.4) to mimic the transit of the particles through the GI tract. Released protein was quantified using MicroBCA protein assay.