Modification of montmorillonite nanolayers as a pH-responsive carrier of biomolecules: Delivery of vitamin B12

In this study nanolayers of montmorillonite (MMT) were modified in order to develop a pH-responsive nanocarrier for delivery of vitamin B12. The vitamin B12 was adsorbed on the MMT nanolayers via cationic bridge mechanism by electrostatic attraction force. A facile treatment of MMT nanolayers was done by increasing the cation or anion concentration of the external surface of nanolayers. In all modified samples the interlayer spaces were filled with a cation (Na+). Such treatment mostly affected the place of adsorption of vitamin B12 which the MMT sample with the external surface of nanolayers enriched with anion (Cl-) tent to adsorb vitamin in the interlayer spaces due to the existence of cations just in the interlayer spaces. However, when the surfaces of nanolayers were enriched with the cation (Na+) vitamin B12 just adsorbed on the external surface of the nanolayers and almost no adsorption in the interlayer spaces was detected. The in vitro release results showed that almost no vitamin B12 was released from modified MMT nanolayers at low pH however by increasing the pH, vitamin started to release with steady kinetics. This could be due to the highly controlled mechanism of adsorption of the vitamin on the nanolayers (cation bridge) which was just desorbed when the highly acidic (highly saturated medium with H+) change to neutral condition (with increasing the possibility of exchangeable anions with the vitamin complex). In addition, the modification of MMT nanolayers affected the amount of vitamin released which when vitamin was intercalated in the interlayer space the release of vitamin became more difficult. The results showed that the modified MMT nanolayers preserved vitamin from the harsh condition of gastric before being released, making it a promising nanocarrier for drug delivery applications. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.