AIE luminogen bridged hollow hydroxyapatite nanocapsules for drug delivery

A new type of organophosphonic acid, (4,4'-(1,2-diphenylethene-1,2-diyl)bis(4,1-phenylene))bis(methylene)diphosphonic acid (PATPE), based on tetraphenylethene has been prepared, and its ester derivative exhibits the characteristic property of aggregation-induced emission (AIE) in DMSO-H2O solution. The PATPE is then fabricated into hydroxyapatite by a one-pot condensation process to form hollow mesoporous nanocapsules of ellipsoidal morphology. The AIE luminogen-bridged hollow hydroxyapatite nanocapsules emit strong blue light under UV irradiation, which is further used for drug delivery using ibuprofen (IBU) as a model drug. The fluorescence intensity of the materials varies greatly with the loading and release of IBU, suggesting that the drug release process may be tracked in terms of the change of luminescence intensity. The biocompatibility of AIE luminogen functionalized material is also evaluated on HUH7 human hepatoma cells using the MTT assay. The low cytotoxicity of the materials reveals that the as-prepared multifunctional hydroxyapatite will be a new candidate for simultaneous drug delivery and cell imaging in potential bioapplications.