Preparation of Ultrathin, Robust Protein Microcapsules
through Template-Mediated Interfacial Reaction between Amine and Catechol
Groups
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Abstract
A novel approach to the synthesis
of protein microcapsules is developed
through template-mediated interfacial reaction. Protein-doped CaCO<sub>3</sub> templates are first synthetized via coprecipitation and then
coated with a catechol-containing alginate (AlgDA) layer. Afterward,
the templates are exposed to ethylenediamine tetraacetic acid disodium
(EDTA) solution to dissolve CaCO<sub>3</sub>. During CaCO<sub>3</sub> dissolution, the generated CO<sub>2</sub> gas pushes protein molecules
moving to the AlgDA layer, and thereby Michael addition and Schiff
base reactions proceed, forming the shell of protein microcapsules.
Three kinds of proteins, namely, bovine serum albumin, catalase, and
protamine sulfate, are utilized. The shell thickness of microcapsule
varies from 25 to 82 nm as the doping amount of protein increased
from 2 to 6 mg per 66 mg CaCO<sub>3</sub>. The protein microcapsules
have a robust but flexible shell and can be reversibly deformed upon
exposure to osmotic pressure. The bioactivity of protein microcapsules
is demonstrated through enzymatic catalysis experiments. The protein
microcapsules remain about 80% enzymatic activity of the equivalent
free protein. Hopefully, our approach could be extended to many other
applications such as drug/gene delivery, tissue scaffolds, and catalysis
due to the universality of Michael reaction and Schiff base reactions