Microwave-Assisted Synthesis of Biocompatible Europium-Doped Calcium Hydroxyapatite and Fluoroapatite Luminescent Nanospindles Functionalized with Poly(acrylic acid)

Abstract

Europium-doped calcium hydroxyapatite and fluoroapatite nanophosphors functionalized with poly(acrylic acid) (PAA) have been synthesized through a one-pot microwave-assisted hydrothermal method from aqueous basic solutions containing calcium nitrate, sodium phosphate monobasic, and PAA, as well as sodium fluoride in the case of the fluoroapatite particles. In both cases a spindlelike morphology was obtained, resulting from an aggregation process of smaller subunits which also gave rise to high specific surface area. The size of the nanospindles was 191 (32) × 40 (5) nm for calcium hydroxyapatite and 152 (24) × 38 (6) nm for calcium fluoroapatite. The luminescent nanoparticles showed the typical red luminescence of Eu3+, which was more efficient for the fluoroapatite particles than for the hydroxyapatite. This is attributed to the presence of OH– quenchers in the latter. The nanophosphors showed negligible toxicity for Vero cells. Both PAA-functionalized nanophosphors showed a very high (up to at least 1 week) colloidal stability in 2-(N-morpholino)ethanesulfonic acid (MES) at pH 6.5, which is a commonly used buffer for physiological pH. All these features make both kinds of apatite-based nanoparticles promising tools for biomedical applications, such as luminescent biolabels and tracking devices in drug delivery systems.

Modified fluorapatite as highly efficient catalyst for the synthesis of chalcones via Claisen–Schmidt condensation reaction

“…including: sol-gel process [27], solid-state reaction [28,29] and the hydrothermal process [30]. The replacement of traditional homogeneous catalysts by heterogeneous catalysts is a field of growing interest from both an industrial and an academic point of view.…”

Luminescence variations in europium-doped silicon-substituted hydroxyapatite nanobiophosphor via three different methods

“…Introduction of Si to HA resulted in substitution of phosphate ion (PO 4 3− ) by silicate ion (SiO 4 4− ) in the HA crystal structure, and siliconsubstituted HA (Si-HA) has become a subject of great attention in biomedical research [11]. Similarly, europium is a suitable activator for doping into calcium-based materials because they exhibit significant advantages compared with available phosphor such as lower toxicities, photostabilities, high thermal and chemical stabilities, high luminescence quantum yield, and sharp emission band [12,13].…”

Rare earth based nanostructured materials: synthesis, functionalization, properties and bioimaging and biosensing applications

“…Several examples can be cited in which these complexes have been used in aqueous solutions such as the synthesis of NaGdF 4 nanorods (100 nm) at 180°C from solutions containing Gd(NO 3 ) 3 and NaF [48], and the synthesis of BaGdF 5 porous nanospheres of sizes ranging from 65 to 119 nm from solutions containing gadolinium and barium nitrate and NaBF 4 at 180°C in butyl amine, which was used to increase the pH [106]. Some RE phosphates have been also synthesized in this way as it is the case of YPO 4 Figure 1F) [46]. Finally, PVP has been used for the synthesis of 50 × 10 nm GdPO 4 :Ln 3+ (Ln = Ce + Tb, Eu, Yb + Er) nanorods by treatment at 180°C of aqueous solutions of Gd(NO 3 ) 3 and Na 2 HPO 4 [112].…”