Mesoporous silica nanoparticles functionalized with hyaluronic acid. Effect of the biopolymer chain length on cell internalization.

Mesoporous silica nanoparticles (MSNs) were functionalized with amino groups (MSN-NH2) and then with hyaluronic acid, a biocompatible biopolymer which can be recognized by CD44 receptors in tumor cells, to obtain a targeting drug delivery system. To this purpose, three hyaluronic acid samples differing for the molecular weight, namely HAS (8-15 kDa), HAM (30-50 kDa) and HAL (90-130 kDa), were used. The MSN-HAS, MSN-HAM, and MSN-HAL materials were characterized through zeta potential and dynamic light scattering measurements at pH = 7.4 and T = 37 °C to simulate physiological conditions. While zeta potential showed an increasing negative value with the increase of the HA chain length, an anomalous value of the hydrodynamic diameter was observed for MSN-HAL, which was smaller than that of MSN-HAS and MSN-HAM samples. The cellular uptake of MSN-HA samples on HeLa cells at 37 °C was studied by optical and electron microscopy. HA chain length affected significantly the cellular uptake that occurred at a higher extent for MSN-NH2 and MSN-HAS than for MSN-HAM and MSN-HAL samples. Cellular uptake experiments carried out at 4 °C showed that the internalization process was inhibited for MSN-HA samples but not for MSN-NH2. This suggests the occurrence of two different mechanisms of internalization. For MSN-NH2 the uptake is mainly driven by the attractive electrostatic interaction with membrane phospholipids, while MSN-HA internalization involves CD44 receptors overexpressed in HeLa cells.