Fabrication of Hybrid Nanocapsules by Calcium Phosphate Mineralization of Shell Cross-Linked Polymer Micelles and Nanocages

Self-assembled shell cross-linked poly(acrylic acid-b-isoprene) (PAA78-b-PI97) micelles or cross-linked PAA nanocages in aqueous solution were used as templates for the preparation of novel polymer−inorganic nanocapsules. The hybrid nanostructures were typically 50−70 nm in diameter and consisted of spherical polymer nanoparticles or nanocages enclosed within a continuous 10−20 nm thick surface layer of amorphous calcium phosphate. Nucleation of calcium phosphate specifically in association with the polymer nanoparticles was facilitated by low supersaturation levels and by sequestration of Ca2+ ions within the carboxylate-rich PAA domains prior to addition of HPO42-. Modifications in ionic concentrations were used to control the calcium phosphate surface layer thickness and prepare mineralized cross-linked PAA-b-PI micelles with variable shell permeability. The permeability of β-carotene into the hydrophobic PI core of mineralized shell cross-linked PAA-b-PI micelles was reduced by approximately 50 or 100...