Dendrimer-functionalized halloysite nanotubes for effective drug delivery

Halloysite nanotubes functionalized with polyamidoamine dendrimer were prepared and characterized. The material studied was applied as a carrier of three model therapeutic compounds - chlorogenic acid, ibuprofen and salicylic acid. It showed higher adsorption capacity for the drugs studied (123.16 mg/g for chlorogenic acid; 182.72 mg/g for ibuprofen; 39.52 mg/g for salicylic acid) compared to raw halloysite and 3-aminopropyl-trimethoxysilane functionalized halloysite nanotubes. The experimental adsorption data fits the Langmuir model. As a result of surface functionalization of halloysite with the dendrimer, the release rate of chlorogenic and salicylic acid decreased, while the release profile of ibuprofen was similar to that of 3-aminopropyl-trimethoxysilane functionalized nanotubes. The release kinetics of chlorogenic acid and salicylic acid followed Higuchi model and the release exponents indicated a Fickian diffusion mechanism. The release mode of ibuprofen followed the first order kinetics and the mechanism was described as non-Fickian (anomalous) transport. The in vivo toxicity studies showed that the dendrimer -functionalized halloysite had no effect on the living organisms used in the bioassays.