Versatile oligo(ethylene glycol)-based biocompatible microgels for loading/release of active bio(macro)molecules

The present study aims in the understanding of the effect of oligo(ethylene glycol)-based biocompatible microgels inner structure on the encapsulation/release mechanisms of different types of cosmetic active molecules. For that, multi-responsive microgels were synthesized using three types of cross-linkers: ethylene glycol dimethacrylate (EGDMA), oligo(ethylene glycol) diacrylate (OEGDA) and N,N-methylenebisacrylamide (MBA). The inner morphology of the microgels synthesized was studied by ¹H-nuclear magnetic resonance (¹H NMR) and small-angle neutron scattering (SANS) techniques and no effect of cross-linker type on microgel microstructure was observed in the case of analysing purified microgel dispersions. Moreover, all the microgels synthesized presented conventional swelling/de-swelling behavior as a function of temperature and pH. Two hydrophobic, one hydrophilic, and one macromolecule as cosmetic active molecules were effectively loaded into different microgel particles via hydrophobic interactions and hydrogen-bonding interactions between -OH groups of active molecules and ether oxygens of different microgel particles. Their release profiles as a function of cross-linker type used and encapsulated amounts were studied by Peppas-Sahlin model. No effect of the cross-linker type was observed due to the similar inner structure of all the microgels synthesized.