Abstract
Calcium phosphate is the most important inorganic constituent of biological tissues, and synthetic calcium phosphate has been widely used as biomaterials. In this study, a facile method has been developed for the fabrication of amorphous calcium phosphate (ACP)/polylactide-block-monomethoxy(polyethyleneglycol) hybrid nanoparticles and ACP porous nanospheres. Europium-doping is performed to enable photoluminescence (PL) function of ACP porous nanospheres. A high specific surface area of the europium-doped ACP (Eu3+:ACP) porous nanospheres is achieved (126.7 m2/g). PL properties of Eu3+:ACP porous nanospheres are investigated, and the most intense peak at 612 nm is observed at 5 mol% Eu3+ doping. In vitro cytotoxicity experiments indicate that the as-prepared Eu3+:ACP porous nanospheres are biocompatible. In vitro drug release experiments indicate that the ibuprofen-loaded Eu3+:ACP porous nanospheres show a slow and sustained drug release in simulated body fluid. We have found that the cumulative amount of released drug has a linear relationship with the natural logarithm of release time (ln(t)). The Eu3+:ACP porous nanospheres are bioactive, and can transform to hydroxyapatite during drug release. The PL properties of drug-loaded nanocarriers before and after drug release are also investigated.
Highlights
The development of multifunctional nanosystems, for maximum therapeutic benefit including early diagnoses of the diseases and delivery of suitable therapeutic drugs, holds a promise for the future of clinical treatment to enhance therapeutic efficacy [1,2]
The morphology of the as-prepared hybrid amorphous calcium phosphate (ACP)/PLAmPEG and ACP were investigated with Transmission electron microscopy (TEM) (Figure 1)
The X-ray diffraction (XRD) pattern of the as-prepared ACP/PLAmPEG hybrid nanoparticles (Figure 2a) shows no discernable peaks of crystalline calcium phosphate but a characteristic hump of amorphous phase at around 2θ = 30°, indicating that the sample consisted of ACP [44]
Summary
The development of multifunctional nanosystems, for maximum therapeutic benefit including early diagnoses of the diseases and delivery of suitable therapeutic drugs, holds a promise for the future of clinical treatment to enhance therapeutic efficacy [1,2]. For the preparation of europium-doped Eu3+:ACP porous nanospheres, europium nitrate aqueous solution was added into the calcium source solution before mixing with phosphate source solution. The typical drug loading and in vitro drug release experiments were performed as follows: 0.5 g of dried powder of Eu3+:ACP porous nanospheres was added into 50 mL hexane solution with an ibuprofen concentration of 40 mg/mL. The Eu3+:ACP porous nanospheres with loaded drug was centrifuged, and 2 mL supernatant was analyzed by UV-Vis absorption spectroscopy at a wavelength of 263 nm to calculate the ibuprofen storage. The drug loaded Eu3+:ACP porous nanospheres were washed with fresh hexane, dried at 60°C in air, and compacted into disks (0.3 g each, diameter 10 mm) at a pressure of 3 MPa. Each disk was immersed into 200 mL of SBF at 37°C under shaking at a constant rate using a desk-type oscillator (THI-92A, China). The Brunauer-Emmett-Teller (BET) surface area and pore size distribution were measured with an accelerated surface area and porosimetry system (ASAP 2010)
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