Synthesis of Hyaluronic acid-Tyramine Microgels for Sustained Protein Release

Microgels are hydrophilic polymer matrix with high water content suitable for encapsulation and delivery of biomolecules. In this study, hyaluronic acid (HA) microgels were synthesized using a water in oil emulsion method. First, hyaluronic acid was modified with tyramine, and then the microemulsion was produced by homogenizing the polymer solution in isooctane as an oil phase. HA microdroplets were crosslinked via enzymatic method by addition of horseradish peroxidase (enzyme) and hydrogen peroxide, and stable microgels were produced in a mild crosslinking reaction. According to the results, larger microgels were achieved by increasing the initial polymer concentration. Two sample proteins, Bovine serum albumin (BSA) and lysozyme, were incorporated in the polymer network to investigate the encapsulation efficiency of the microgels. The results demonstrated that the proposed method has a high efficiency for protein encapsulation (> 70%). The release profiles showed that lysozyme, as a cationic protein, was released in a sustained manner over a period of two weeks. However, BSA, as a negatively charged protein, showed a faster release rate. The simple method of microgel fabrication, besides the sustained release of the encapsulated proteins, makes the HA microgels a promising vehicle for delivery of cationic proteins.