In vitro controlled release of vitamin C from Ca/Al layered double hydroxide drug delivery system

• Vitamin C intercalated Ca–Al layered double hydroxide (Ca2Al–VC) was prepared.
• Thermal stability of VC was improved after intercalation.
• Release property of vitamin C was studied in a phosphate buffer at pH 7.4.
• Ca2Al–VC significantly extends the release time of VC in the buffer.
• An ion exchange process occurs in phosphate buffer solution.

A new drug delivery system for vitamin C (VC), Ca/Al layered double hydroxide (LDH), is demonstrated in this work. VC anions were intercalated successfully in the Ca/Al LDH gallery by a coprecipitation method. The interlayer space of 9.8 Å suggests that VC anions are vertical to the LDH layers in the form of interdigitated bilayer. The loading of VC in LDH is 36.4 wt.%. The thermal stability of VC is significantly enhanced after intercalation. In vitro VC release results show that the release time of VC in a phosphate buffer at pH 7.4 was significantly extended, and the maximal percentage of VC released is 80% of the total. The Avrami–Erofe'ev equation most satisfactorily explains the release kinetics of VC, which is that the release of VC is mainly dominated by the ion-exchange reaction.