Preparation of Protamine-Titania Microcapsules Through Synergy Between Layer-by-Layer Assembly and Biomimetic Mineralization

A novel approach combining layer-by-layer (LbL) assembly with biomimetic mineralization is proposed to prepare protamine-titiania hybrid microcapsules. More specifically, these microcapsules are fabricated by alternative deposition of positively charged protamine layers and negatively charged titania layers on the surface of CaCO3 microparticles, followed by dissolution of the CaCO3 microparticles using EDTA. During the deposition process, the protamine layer induces the hydrolysis and condensation of a titania precursor, to form the titania layer. Thereafter, the negatively charged titania layer allows a new cycle of deposition step of the protamine layer, which ensures a continuous LbL process. The morphology, structure and chemical composition of the microcapsules are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Moreover, these protamine-titania hybrid microcapsules are first employed as the carrier for the immobilization of yeast alcohol dehydrogenase (YADH), and the encapsulated YADH displays enhanced recycling stability. This approach may open a facile, general, and efficient way to prepare organic-inorganic hybrid materials with different compositions and shapes.