Hydroxyapatite nanowhiskers embedded in chondroitin sulfate microspheres as colon targeted drug delivery systems

An inorganic/organic hybrid material with a triggering mechanism for specific drug delivery at the colon was synthesized. First, hydroxyapatite nanowhiskers (n-HA) with a high aspect ratio, narrow particle size distribution and high surface area, ca. 67 m² g^-1, are prepared. As proof-of-concept, terbinafine, a fungicidal agent, was loaded onto the n-HA, obtaining a drug loading of 40.63 mg of terbinafine per gram of n-HA. Hydroxyapatite nanowhiskers loaded with terbinafine were encapsulated with chondroitin sulfate (CS) microspheres, using chemically modified glycidyl methacrylate by performing ultrasonic microemulsion polymerization. The obtained hybrid materials were characterized by TEM, SEM, FTIR, and NMR. Dispersed n-HA in CS microspheres was obtained for different n-HA contents, from 1 to 10% (w/w). In vitro studies have been carried out to investigate terbinafine release from hybrid microspheres in simulated gastric fluid and simulated intestinal fluid. The studies demonstrated that sustained drug release can be obtained using the developed hybrid material.