Hierarchical hydroxyapatite/polyelectrolyte microcapsules capped with AuNRs for remotely triggered drug delivery.

In the present paper, a smart drug delivery platform combining the hollow hierarchical hydroxyapatite (HAP), chitosan/hyaluronic acid polyelectrolyte multilayers and Au nanorods (AuNRs) had been prepared via a layer-by-layer (LbL) technique. AuNRs capped on the surface of HAP/polyelectrolyte hybrid microcapsules acted as the "gate-keeper" to obstruct the leakage of loaded drug and endow the hybrid microcapsules with excellent near-infrared (NIR)-triggered drug release property. In vitro drug release results indicated that the hybrid microcapsules exhibited distinguished pH- and NIR-responsive drug release properties. More interestingly, relatively high DOX release could be observed at pH 4.5 upon NIR laser irradiation owing to the hybrid matrix disintegration in acidic media and the noteworthy photothermal transition effect of AuNRs. The cell viability results demonstrated that the hybrid microcapsules possessed excellent biocompatibility. The present paper provides a facile and green route to fabricate hierarchical multi-responsive drug carriers with high drug loading capacity and outstanding biocompatibility, which are highly attractive for remotely controllable drug delivery.