Figure 4.

Generation of controllable protein gradients via localized, sustained release from a microsphere depot. (A) Schematic of the microsphere depot combined with a PEGDA hydrogel. (B) Photographs of the completed multicomponent hydrogel. (C) Fluorescence images of BSA gradient generation (pseudocolored to indicate fluorescence intensity distribution). Left: 10 mg · mL⁻¹ BSA-loaded microspheres. Middle: 30 mg · mL⁻¹ BSA-loaded microspheres. Right: 60 mg · mL⁻¹ BSA-loaded microspheres. (D) Concentration gradients in hydrogels containing 60 mg · mL⁻¹ (◆), 30 mg · mL⁻¹ (■), and 10 mg · mL⁻¹ BSA (▲). (E) Concentration gradients in hydrogels containing lysozyme (◆), ovalbumin (■), and BSA (▲). Lysozyme has the lowest hydrodynamic radius of the three proteins while BSA has the highest. (F) BSA Concentration gradients in hydrogels composed of 5% (◆), 10% (■), and 15% PEGDA (▲). These results demonstrate multiple mechanisms for tailoring gradient characteristics by controlling material properties. Figure portions C–F reproduced with permission from ref.^[60] Copyright Wiley-VCH Verlag GmbH & Co. KGaA.