Surface roughness effect on the cellular uptake of layered double hydroxide nanoparticles

Layered double hydroxide (LDH) particles with a uniform size of ~200 nm were prepared by the hydrothermal method, and fluorescein moiety was introduced into their gallery space. Through modifying synthesis routes such as ion-exchange and reconstruction, final LDH particles were obtained with a smooth and rough surface, respectively. Thanks to the topotactic ion-exchange and systematic reconstruction, the two LDH had the same particle dimension, surface charge and colloidal properties except for surface roughness. Cell viability test employing human lung adenocarcinoma epithelial cells (A549) showed that both the LDH, regardless of surface roughness showed sufficient biocompatibility up to a concentration of 200 μg/mL. According to fluorescence assisted cell sorting and confocal microscopy, we could quantitatively and qualitatively confirm that the smooth particles were more advantageous in terms of cellular uptake compared to rough particles. According to a series of biological assays with or without proteins, we could suggest that the benefit of smooth-surfaced LDH was related to their higher protein adsorption property compared to rough particles; protein adsorption was considered to enhance both colloidal stability in biological fluid and cellular interaction at the membrane.