Enhancing Surface Coverage and Growth in Layer-by-Layer
Assembly of Protein Nanoparticles
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Abstract
Thin films of bovine serum albumin
(BSA) nanoparticles are fabricated
via layer-by-layer assembly. The surface of BSA nanoparticles have
two oppositely acting functional groups on the surface: amine (NH<sub>2</sub>) and carboxylate (COO<sup>–</sup>). The protonation
and deprotonation of these functional groups at different pH vary
the charge density on the particle surface, and entirely different
growth can be observed by varying the nature of the complementary
polymer and the pH of the particles. The complementary polymers used
in this study are poly(dimethyldiallylammonium chloride) (PDDAC) and
poly(acrylic acid) (PAA). The assembly of BSA nanoparticles based
on electrostatic interaction with PDDAC suffers from the poor loading
of the nanoparticles. The assembly with PAA aided by a hydrogen bonding
interaction shows tremendous improvement in the growth of the assembly
over PDDAC. Moreover, the pH of the BSA nanoparticles was observed
to affect the loading of nanoparticles in the LbL assembly with PAA
significantly