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

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

β-Tricalcium phosphate (β-TCP) is widely used as bone implant material. It has been observed that doping the β-TCP structure with certain cations can help in combating bacteria and pathogenic microorganisms. Previous literature investigations have focused on tricalcium phosphate structures with silver, copper, zinc, and iron cations. However, there are limited studies available on the biological properties of β-TCP containing nickel and cobalt ions. In this work, Ca10.5-xNix(PO4)7 and Ca10.5-xCox(PO4)7 solid solutions with the β-Ca3(PO4)2 structure were synthesized by a high-temperature solid-state reaction. Structural studies revealed the β-TCP structure becomes saturated at 9.5 mol/% for Co2+ or Ni2+ ions. Beyond this saturation point, Ni2+ and Co2+ ions form impurity phases after complete occupying of the octahedral M5 site. The incorporation of these ions into the β-TCP crystal structure delays the phase transition to the α-TCP phase and stabilizes the structure as the temperature increases. Biocompatibility tests conducted on adipose tissue-derived mesenchymal stem cells (aMSC) using the (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) (MTT) assay showed that all prepared samples did not exhibit cytotoxic effects. Furthermore, there was no inhibition of cell differentiation into the osteogenic lineage. Antibacterial properties were studied on the C. albicans fungus and on E. coli, E. faecalis, S. aureus, and P. aeruginosa bacteria strains. The Ni- and Co-doped β-TCP series exhibited varying degrees of bacterial growth inhibition depending on the doping ion concentration and the specific bacteria strain or fungus. The combination of antibacterial activity and cell-friendly properties makes these phosphates promising candidates for anti-infection bone substitute materials.

Polyvinylpyrrolidone-Alginate-Carbonate Hydroxyapatite Porous Composites for Dental Applications

An alternative approach for the currently used replacement therapy in dentistry is to apply materials that restore tooth tissue. Among them, composites, based on biopolymers with calcium phosphates, and cells can be applied. In the present work, a composite based on polyvinylpyrrolidone (PVP) and alginate (Alg) with carbonate hydroxyapatite (CHA) was prepared and characterized. The composite was investigated by X-ray diffraction, infrared spectroscopy, electron paramagnetic resonance (EPR) and scanning electron microscopy methods, and the microstructure, porosity, and swelling properties of the material were described. In vitro studies included the MTT test using mouse fibroblasts, and adhesion and survivability tests with human dental pulp stem cells (DPSC). The mineral component of the composite corresponded to CHA with an admixture of amorphous calcium phosphate. The presence of a bond between the polymer matrix and CHA particles was shown by EPR. The structure of the material was represented by micro- (30-190 μm) and nano-pores (average 8.71 ± 4.15 nm). The swelling measurements attested that CHA addition increased the polymer matrix hydrophilicity by 200%. In vitro studies demonstrated the biocompatibility of PVP-Alg-CHA (95 ± 5% cell viability), and DPSC located inside the pores. It was concluded that the PVP-Alg-CHA porous composite is promising for dentistry applications.

Ion-Doped Calcium Phosphate-Based Coatings with Antibacterial Properties

Ion-substituted calcium phosphate (CP) coatings have been extensively studied as promising materials for biomedical implants due to their ability to enhance biocompatibility, osteoconductivity, and bone formation. This systematic review aims to provide a comprehensive analysis of the current state of the art in ion-doped CP-based coatings for orthopaedic and dental implant applications. Specifically, this review evaluates the effects of ion addition on the physicochemical, mechanical, and biological properties of CP coatings. The review also identifies the contribution and additional effects (in a separate or a synergistic way) of different components used together with ion-doped CP for advanced composite coatings. In the final part, the effects of antibacterial coatings on specific bacteria strains are reported. The present review could be of interest to researchers, clinicians, and industry professionals involved in the development and application of CP coatings for orthopaedic and dental implants.

Antibacterial Composite Material Based on Polyhydroxybutyrate and Zn-Doped Brushite Cement

A composite material based on electrospinning printed polyhydroxybutyrate fibers impregnated with brushite cement containing Zn substitution was developed for bone implant applications. Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy were applied for materials characterization. Soaking the composite in Ringer's solution led to the transformation of brushite into apatite phase, accompanied by the morphology changes of the material. The bending strength of the composite material was measured to be 3.1 ± 0.5 MPa. NCTC mouse fibroblast cells were used to demonstrate by means of the MTT test that the developed material was not cytotoxic. The behavior of the human dental pulp stem cells on the surface of the composite material investigated by the direct contact method was similar to the control. It was found that the developed Zn containing composite material possessed antibacterial properties, as testified by microbiology investigations against bacteria strains of Escherichia coli and Staphylococcus aureus. Thus, the developed composite material is promising for the treatment of damaged tissues with bacterial infection complications.

Bioactive Inorganic Materials for Dental Applications: A Narrative Review

Over time, much attention has been given to the use of bioceramics for biomedical applications; however, the recent trend has been gaining traction to apply these materials for dental restorations. The bioceramics (mainly bioactive) are exceptionally biocompatible and possess excellent bioactive and biological properties due to their similar chemical composition to human hard tissues. However, concern has been noticed related to their mechanical properties. All dental materials based on bioactive materials must be biocompatible, long-lasting, mechanically strong enough to bear the masticatory and functional load, wear-resistant, easily manipulated, and implanted. This review article presents the basic structure, properties, and dental applications of different bioactive materials i.e., amorphous calcium phosphate, hydroxyapatite, tri-calcium phosphate, mono-calcium phosphate, calcium silicate, and bioactive glass. The advantageous properties and limitations of these materials are also discussed. In the end, future directions and proposals are given to improve the physical and mechanical properties of bioactive materials-based dental materials.

Strontium Substituted β-Tricalcium Phosphate Ceramics: Physiochemical Properties and Cytocompatibility

Sr²⁺-substituted β-tricalcium phosphate (β-TCP) powders were synthesized using the mechano-chemical activation method with subsequent pressing and sintering to obtain ceramics. The concentration of Sr²⁺ in the samples was 0 (non-substituted TCP, as a reference), 3.33 (0.1SrTCP), and 16.67 (0.5SrTCP) mol.% with the expected Ca₃(PO₄)₂, Ca_2.9Sr_0.1(PO₄)₂, and Ca_2.5Sr_0.5(PO₄)₂ formulas, respectively. The chemical compositions were confirmed by the energy-dispersive X-ray spectrometry (EDX) and the inductively coupled plasma optical emission spectroscopy (ICP-OES) methods. The study of the phase composition of the synthesized powders and ceramics by the powder X-ray diffraction (PXRD) method revealed that β-TCP is the main phase in all compounds except 0.1SrTCP, in which the apatite (Ap)-type phase was predominant. TCP and 0.5SrTCP ceramics were soaked in the standard saline solution for 21 days, and the phase analysis revealed the partial dissolution of the initial β-TCP phase with the formation of the Ap-type phase and changes in the microstructure of the ceramics. The Sr²⁺ ion release from the ceramic was measured by the ICP-OES. The human osteosarcoma MG-63 cell line was used for viability, adhesion, spreading, and cytocompatibility studies. The results show that the introduction of Sr²⁺ ions into the β-TCP improved cell adhesion, proliferation, and cytocompatibility of the prepared samples. The obtained results provide a base for the application of the Sr²⁺-substituted ceramics in model experiments in vivo.