Smart H₂O₂-Responsive Drug Delivery System Made by Halloysite Nanotubes and Carbohydrate Polymers

A novel chemical hydrogel was facilely achieved by coupling 1,4-phenylenebisdiboronic acid modified halloysite nanotubes (HNTs-BO) with compressible starch. The modified halloysite nanotubes (HNTs) and prepared hydrogel were characterized by solid-state nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The linkage of B-C in the hydrogel can be degraded into B-OH and C-OH units in the presence of H₂O₂ and result in the degradation of the chemical hydrogel. Pentoxifylline was loaded into the lumen of the HNTs-BO, and then gave the pentoxifylline-loaded hydrogel. The drug release profile shows that it was no more than 7% dissolved when using phosphate buffer solution (PBS) as the release medium. Notably, a complete release (near 90%) can be achieved with the addition of H₂O₂ ([H₂O₂] = 1 × 10^-4 M), suggesting a high H₂O₂ responsiveness of the as-formed hydrogel. The drug release results also show that the "initial burst release" can be effectively suppressed by loading pentoxifylline inside the lumen of the HNTs rather than embedding the drug in the hydrogel network. The drug-loaded hydrogel with H₂O₂-responsive release behavior may open up a broader application in the field of biomedicine.