Engineering surface modification of biodegradable periodic mesoporous organosilica for adenosine loading

Surface modification can improve specific properties of nanocarrier systems, such as drug penetration and encapsulation, depending on the charge of the modified surface. In this research, the surface of biodegradable periodic mesoporous organosilica nanoparticles was single-surface-modified using amine as the positive amino (-NH 2 ) group and phosphonate (-PO 3 ) as the negative group. The successful modification of the particle surface charge was confirmed using zeta potential measurements and elemental analysis. Scanning electron microscopy images revealed that the surface-modified nanoparticles and the unmodified nanoparticles had similar shapes and sizes. The modification influences porous characters and the zeta potential but not the size and morphology of nanoparticles. Adenosine was used as a model drug to study the effect of surface charge on drug loading capacity. The hydrophilicity due to phosphonate modification enhanced the loading capacity of the water-soluble anticancer drug owing to the high electrostatic attraction. The difference in loading capacity is attributable to the difference in the physiological function of nanoparticles. The experimental results of all nanoparticles fitted with a second-order kinetic model revealed adenosine loading on particles based on multilayer adsorption. Additionally, the loading of all types of particles was suitable for an intra-particle diffusion mechanism. These results provide a comparison between the properties of pristine and surface-modified biodegradable periodic mesoporous organosilica in drug-loading applications.