Precisely controlled delivery of magnesium ions thru sponge-like monodisperse PLGA/nano-MgO-alginate core-shell microsphere device to enable in-situ bone regeneration

Publication date: August 2018
Source:Biomaterials, Volume 174
Author(s): Zhengjie Lin, Jun Wu, Wei Qiao, Ying Zhao, Karen H.M. Wong, Paul K. Chu, Liming Bian, Shuilin Wu, Yufeng Zheng, Kenneth M.C. Cheung, Frankie Leung, Kelvin W.K. Yeung
A range of magnesium ions (Mg²⁺) used has demonstrated osteogenic tendency in vitro. Hence, we propose to actualize this concept by designing a new system to precisely control the Mg²⁺ delivery at a particular concentration in vivo in order to effectively stimulate in-situ bone regeneration. To achieve this objective, a monodisperse core-shell microsphere delivery system comprising of poly (lactic-co-glycolic acid) (PLGA) biopolymer, alginate hydrogel, and magnesium oxide nano-particles has been designed by using customized microfluidic capillary device. The PLGA-MgO sponge-like spherical core works as a reservoir of Mg²⁺ while the alginate shell serves as physical barrier to control the outflow of Mg²⁺ at ∼50 ppm accurately for 2 weeks via its adjustable surface micro-porous network. With the aid of controlled release of Mg²⁺, the new core-shell microsphere system can effectively enhance osteoblastic activity in vitro and stimulate in-situ bone regeneration in vivo in terms of total bone volume, bone mineral density (BMD), and trabecular thickness after operation. Interestingly, the Young's moduli of formed bone on the core-shell microsphere group have been restored to ∼96% of that of the surrounding matured bone. These findings indicate that the concept of precisely controlled release of Mg²⁺ may potentially apply for in-situ bone regeneration clinically.

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