Studies of a novel bone-targeted nano drug delivery system with a HAP core-PSI coating structure for tanshinol injection

Tanshinol (Tan) has good therapeutic effects on osteoporosis, fracture, and bone trauma repair. However, it is easily oxidised, has low bioavailability and a short half-life. To solve these problems, the study aimed to develop a novel bone-targeted nano-sustained-release drug delivery system PSI-HAPs for the systemic administration of Tan. This proposed system has hydroxyapatite (HAP) as the core to load drug and polysuccinimide (PSI), PEG-PSI (Polyethylene glycol, PEG), and ALN-PEG-PSI (Alendronate sodium, ALN) as the coating materials to form nanoparticles. The article examines the various PSI-HAPs' entrapping efficiency (EE, %), drug loading capacity (DLC, %), and distribution to determine the best PSI-HAP formulation in vivo. The in vivo experiment showed that the ALN-PEG-PSI-HAP (ALN-PEG/PSI molar ratio = 1:20) was the best preparation due to its higher distribution on bone (120 h) and lower distribution in the other tissues. The determined preparation was a uniformly spherical or sphere-like nanoparticle with a negative zeta potential. Additionally, it exhibited pH-sensitive drug release in PBS based on an in vitro drug release test. The proposed PSI-HAP preparations were prepared in the water solution using a facile preparation process without ultrasound, heating, and other conditions, which can significantly affect the stability of drugs.