title: Permeability and micromechanical properties of silk ionomer microcapsules.
abstract: We studied the pH-responsive behavior of layer-by-layer (LbL) microcapsules fabricated from silk fibroin chemically modified with different poly amino acid side chains: cationic (silk-poly L-lysine, SF-PL) or anionic (silk-poly-L-glutamic acid, SF-PG). We observed that stable ultrathin shell microcapsules can be assembled with a dramatic increase in swelling, thickness, and microroughness at extremely acidic (pH < 2.5) and basic (pH > 11.0) conditions without noticeable disintegration. These changes are accompanied by dramatic changes in shell permeability with a 2 orders of magnitude increase in the diffusion coefficient. Moreover, the silk ionomer shells undergo remarkable softening with a drop in Young's modulus by more than 1 order of magnitude due to the swelling, stretching, and increase in material porosity. The ability to control permeability and mechanical properties over a wide range for the silk-based microcapsules, with distinguishing stability under harsh environmental conditions, provides an important system for controlled loading and release and applications in bioengineering.
authors: School of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu, P R China.
authors: Chunhong
authors: C
authors: Ye
authors: Irina
authors: I
authors: Drachuk
authors: Rossella
authors: R
authors: Calabrese
authors: Hongqi
authors: H
authors: Dai
authors: David L
authors: DL
authors: Kaplan
authors: Vladimir V
authors: VV
authors: Tsukruk
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D002214:Capsules; D004058:Diffusion; D005349:Fibroins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D055595:Mechanical Phenomena; D055616:Microtechnology; D010539:Permeability; D011094:Polyethyleneimine / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D002214:Capsules; D011108:Polymers; D011094:Polyethyleneimine; D005349:Fibroins