Influence of Synthesis Conditions on Gadolinium-Substituted Tricalcium Phosphate Ceramics and Its Physicochemical, Biological, and Antibacterial Properties

Abstract

Gadolinium-containing calcium phosphates are promising contrast agents for various bioimaging modalities. Gadolinium-substituted tricalcium phosphate (TCP) powders with 0.51 wt% of gadolinium (0.01Gd-TCP) and 5.06 wt% of (0.1Gd-TCP) were synthesized by two methods: precipitation from aqueous solutions of salts (1) (Gd-TCP-pc) and mechano-chemical activation (2) (Gd-TCP-ma). The phase composition of the product depends on the synthesis method. The product of synthesis (1) was composed of β-TCP (main phase, 96%), apatite/chlorapatite (2%), and calcium pyrophosphate (2%), after heat treatment at 900 °C. The product of synthesis (2) was represented by β-TCP (main phase, 73%), apatite/chlorapatite (20%), and calcium pyrophosphate (7%), after heat treatment at 900 °C. The substitution of Ca2+ ions by Gd3+ in both β-TCP (main phase) and apatite (admixture) phases was proved by the electron paramagnetic resonance technique. The thermal stability and specific surface area of the Gd-TCP powders synthesized by two methods were significantly different. The method of synthesis also influenced the size and morphology of the prepared Gd-TCP powders. In the case of synthesis route (1), powders with particle sizes of tens of nanometers were obtained, while in the case of synthesis (2), the particle size was hundreds of nanometers, as revealed by transmission electron microscopy. The Gd-TCP ceramics microstructure investigated by scanning electron microscopy was different depending on the synthesis route. In the case of (1), ceramics with grains of 1–50 μm, pore sizes of 1–10 µm, and a bending strength of about 30 MPa were obtained; in the case of (2), the ceramics grain size was 0.4–1.4 μm, the pore size was 2 µm, and a bending strength of about 39 MPa was prepared. The antimicrobial activity of powders was tested for four bacteria (S. aureus, E. coli, S. typhimurium, and E. faecalis) and one fungus (C. albicans), and there was roughly 30% of inhibition of the micro-organism’s growth. The metabolic activity of the NCTC L929 cell and viability of the human dental pulp stem cell study demonstrated the absence of toxic effects for all the prepared ceramic materials doped with Gd ions, with no difference for the synthesis route.

Polyvinylpyrrolidone—Alginate—Carbonate Hydroxyapatite Porous Composites for Dental Applications

“…This can be explained by the peculiarity of synthesis by precipitation, often characterized by the presence of a small amount of impurities of initial reagents. A small amount of pyrophosphate was also found in the developed composition of PVP-Alg-CHA [ 22 ].…”

“…CaP is available in the form of cements [ 12 ], granules [ 13 ] or powders [ 14 ]. CaP may contain substituting ions [ 15 , 16 , 17 ] to impart osteoinductive (Sr) [ 18 ] or antibacterial (Cu, Zn, Ag, Mn, Gd) [ 19 , 20 , 21 , 22 , 23 ] properties. For dental applications, carbonate hydroxyapatite (CHA, Ca 10 (PO 4 ) 6 (CO 3 ) 0.5 (OH) is a good choice, because of its similar composition to the mineral component of dentin [ 24 ].…”

Antimicrobial and Cell-Friendly Properties of Cobalt and Nickel-Doped Tricalcium Phosphate Ceramics

“…The spectra of the Co-series samples were almost identical. Only the 1.0Ni-TCP sample in the Ni-series showed slight differences, with bands at 1213 cm −1 and 726 cm −1 assigned to P2O7 4− [28]. These differences were attributed to trace amounts of impurities in the initial components, as the intensity was low.…”

“…To enhance the antibacterial properties of β-TCP-based materials, a number of compositions were developed. These compositions contain ions with antibacterial properties, such as Zn 2+ [16,17], Cu 2+ [8,18], Mn 2+ [19,20], Fe 3+ [21][22][23], Ag + [24], and Gd 3+ ions [25][26][27][28], as well as borate or silicate anions [29,30].…”

Exploring Borate-Modified Calcium Phosphate Ceramics: Antimicrobial Potential and Cytocompatibility Assessment

“…A promising approach involves incorporating ions with antibacterial properties, such as zinc, copper, gadolinium, manganese, etc., into bioresorbable CP matrices. This not only introduces antibacterial activity but also enhances the rate of bioresorption compared to matrices without ion doping [ 10 , 11 , 12 , 13 ].…”