Monodisperse Porous Microspheres with pH-Responsive Permeability and Reactivity

Microparticles made from stimuli-responsive materials are promising structures for controlled release, adsorption materials, and sensors. We envision them also to mimic autonomous muscle-like contraction and expansion cycles. This requires a combination of reaction-induced volume switching and switchable substrate supply. For this purpose, we report the synthesis of enzymatic active, monodisperse, porous, and pH-responsive microspheres. The microspheres were synthesized by utilizing a versatile flow chemistry device combining droplet formation, UV-initiated free radical polymerization, and superimposed phase separation between the polymer and a water–methanol mixture. Uptake experiments revealed the switchable permeability for glucose. This switchable permeability adjusts the enzymatic conversion rate of glucose by changing the microparticles swelling state. The developed synthetic and fluidic framework will allow rendering the microparticle diameter and porosity as well as the conversion rates. Balancing these rates adequately may enable autonomous contraction and expansion cycles of such microparticles.