The penetration behavior of nanoparticles in mucous depends
on
physicochemical properties of the nanoparticles and the mucus microenvironment,
due to particle–mucin interactions and the presence of the
mucin mesh space filtration effect. To date, it is still unclear how
the surface properties of nanoparticles influence their mucus penetration
behaviors in various physiological and pathophysiological conditions.
In this study, we have prepared a comprehensive library of amine-,
carboxyl-, and PEG-modified silica nanoparticles (SNPs) with controlled
surface ligand densities. Using multiple particle tracking, we have
studied the mechanism responsible for the mucus penetration behaviors
of these SNPs. It was found that PEG- and amine-modified SNPs exhibited
pH-independent immobilization under iso-density conditions, while
carboxyl-modified SNPs exhibited enhanced movement only in weakly
alkaline mucus. Biophysical characterizations demonstrated that amine-
and carboxyl-modified SNPs were trapped in mucus due to electrostatic
interactions and hydrogen bonding with mucin. In contrast, high-density
PEGylated surface formed a brush conformation that shields particle–mucin
interactions. We have further investigated the surface property-dependent
mucus penetration behavior using a murine airway distribution model.
This study provides insights for designing efficient transmucosal
nanocarriers for prevention and treatment of pulmonary diseases.