Fabrication And Application Of Sericin-based Microcapsules With Biomimetic Structures

Since phospholipid microcapsules was fabricated by simulating the structure of cellmembrane, the applications of microcapsules were developed quickly, specifically in the aspectsof microcapsules being used as drug carriers to exclusively target cancer cells, tumour cells andcontrolled drug-release, they display well prospect. Due to very excellent biocompatibility andbiodegradability, so polypeptide-based and protein-based microcapsules were researched verybroadly. But the methods of fabricating microcapsules require sophisticated processes or organicsolvent, therefore, it is a hot issue that innovative ways need be proposed to fabricatepolypeptide-based and protein-based microcapsules through simple, easy andenvironment-friendly process.In this paper, the sericin-based microcapsules were fabricated through only one step wayin which Ca2+ion induced sericin to self-assemble in water solution and mild reaction condition.We also researched the effect of varied reaction condition on the morphologies and sizes ofmicrocapsules. And that, we discussed the self-assembly process and mechanism of cocoon-likesericin-based microcapsules by DLS, FTIR-ATR, CD, EDX, TEM and the stability anddrug-loaded and drug-released of cocoon-like sericin-based microcapsules by UV. Detailedcontents and results as follow:1. We fabricated spherical, cocoon-like microcapsules and hollow protein tubes by varyingreaction conditions. The microcapsules possessing homogeneous morphology and narrow sizedistribution were easily self-assembled in low sericin concentration, neutral pH and25~37℃.The size of sericin-based microcapsules was reduced when we increased the shock rate. So,sericin was assembled into hollow tubes in220rpm, cocoon-like microcapsules in150rpm,spherical microcapsules in80rpm. The size sericin-based microcapsules was increased when weincreased the Ca2+concentration. Therefore, sericin was assembled into spherical microcapsulesin low Ca2+concentration, cocoon-like microcapsules in high Ca2+concentration. We made100nm spherical microcapsules through increasing the molecular weight of sericin protein. 2. Due to research the self-assembly process of cocoon-like microcapsules, we found that theself-assembly process of cocoon-like microcapsules can be separated into three stages,respectively long-term aging stage, quick self-assembly stage, stable stage. The results of CD,ATR indicated Ca2+ion induces sericin to change conformation from random coil to-sheet. Theresults of Mapping indicated Ca2+ion were homogeneous distribution in the shell of cocoon-likemicrocapsules. So, the hydrophobic-sheet and the chelation of Ca2+and sericin inducecommonly sericin to self-assemble orderly.3. The cocoon-like microcapsules are more stable in acid environment than alkalineenvironment. The load rate of Methylene blue reached to26.25%. The release of methylene bluefrom cocoon-like microcapsules was separated into three stages in PBS buffer solution (pH7.4,T37℃), respectively,burst release stage, constant rate release stage, moderating release stage.