where 𝑀 𝑡 is the amount of diffusing substance released after time 𝑡 and 𝑀 ∞ is the corresponding quantity after infinite time, and 𝐷 is the diffusion coefficient. To account for a fraction of immobilized EVs in the gel, the function 𝑓 𝑚𝑜𝑏 𝑀 𝑡 /𝑀 ∞ was fitted to the release profiles, where 𝑓 𝑚𝑜𝑏 is the mobile fraction. In the model fit, 𝑙 was set equal to the experimentally determined gel thickness (1.26 mm).