Abstract
Li+/Eu3+ dual-doped calcium apatite analogues were fabricated using a microwave stimulated hydrothermal technique. XRPD, FT-IR, micro-Raman spectroscopy, TEM and SAED measurements indicated that obtained apatites are single-phased, crystallize with a hexagonal structure, have similar morphology and nanometric size as well as show red luminescence. Lithium effectively modifies the local symmetry of optical active sites and, thus, affects the emission efficiency. Moreover, the hydrodynamic size and surface charge of the nanoparticles have been extensively studied. The protein adsorption (lysozyme, LSZ; bovine serum albumin, BSA) on the nanoparticle surface depended on the type of cationic dopant (Li+, Eu3+) and anionic group (OH−, Cl−, F−) of the apatite matrix. Interaction with LSZ resulted in a positive zeta potential, and the nanoparticles had the lowest hydrodynamic size in this protein medium. The cytotoxicity assessment was carried out on the human osteosarcoma cell line (U2OS), murine macrophages (J774.E), as well as human red blood cells (RBCs). The studied apatites were not cytotoxic to RBCs and J774.E cells; however, at higher concentrations of nanoparticles, cytotoxicity was observed against the U2OS cell line. No antimicrobial activity was detected against Gram-negative bacteria with one exception for P. aeruginosa treated with Li+-doped fluorapatite.
Highlights
The nanoapatites: HAp, ClAp and FAp were obtained by a microwave-stimulated hydrothermal method using: Ca(NO3 )2 ·4H2 O (99+% Acros Organics, Geel, Belgium), CaCl2 ·2H2 O (99.9% Alfa Aesar, Haverhill, MA, USA), (NH4 )2 HPO4 (≥98% Avantor Performance Materials Poland S.A, Gliwice, Poland), Eu2 O3 (99.99% Alfa Aesar, Haverhill, MA, USA), Li2 CO3 (99.9% Alfa Aesar, Haverhill, MA, USA) and NH4 F (98% Alfa Aesar, Haverhill, MA, USA) as starting substrates and NH3 ·H2 O
According to the X-ray powder diffractograms (XRPD) analysis, the obtained materials are identified as hexagonal apatites belonged to the P63 /m space group
Our results strongly indicate that nanoapatites does not induce any harmful effects on human red blood cells (RBCs)’ membrane structure and function in vitro during both short (60 min) and long (24 h) incubation
Summary
An ideal diagnostic and therapeutic (theranostics) system should possess the ability to transport active pharmaceutical compounds to target cells or tissues and release them in a controlled manner simultaneously dealing with a real-time monitoring of treatment effect based on photoluminescence properties of rare earth ions (RE3+ ) [8]. Three analogues of apatite: hydroxyapatite (Ca10 (PO4 ) (OH) ; HAp), chlorapatite (Ca10 (PO4 ) Cl2 ; ClAp) and fluorapatite (Ca10 (PO4 ) F2 ; FAp) have been evaluated in terms of cytotoxicity in cell-culture studies. These matrices have been modified (while maintaining the crystal structure) using cationic dopants, lithium (Li+ ) and europium (Eu3+ ) ions.
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