Mechanochemical Synthesis of Hydroxyapatite Nanopowder: Effects of Rotation Speed and Milling Time on Powder Properties

Preparation, Characterization, and Biocompatibility Assessment of Polymer-Ceramic Composites Loaded with Salvia officinalis Extract

In the present work, hydroxyapatite-polymer materials were developed. The preparation, as well as characterization of the ceramic-polymer composites based on polyvinylpyrrolidone, sodium alginate, and gelatin were described. The system was enriched with the addition of common sage extract (Salvia officinalis). The antioxidant potential of sage aqueous extract and total polyphenol content was determined. The antioxidant capacity and total phenolic content of extract were equal to 86.06 ± 0.49% and 16.21 ± 0.58 mg gallic acid equivalents per gram of dry weight, respectively. Incubation studies in selected biological liquids were carried out to determine the biomineralization capacity on the surface of the composites and to examine the kinetics of release of the active substances from within the material. As a result of the incubation, a gradual release of the extract over time from the polymer matrix was observed; moreover, the appearance of new apatite layers on the composite surface was recorded as early as after 14 days, which was also confirmed by energy-dispersive X-ray spectroscopy (EDS) microanalysis. The composites were analyzed with Fourier transform infrared spectroscopy (FTIR) spectroscopy, and the morphology was recorded by scanning electron microscope (SEM) imaging. The in vitro biological studies allowed their cytotoxic effect on the reference L929 fibroblasts to be excluded. Further analysis of the biomaterials showed that enrichment with polyphenols does not support the adhesion of L929 cells to the surface of the material. However, the addition of these natural components stimulates human monocytes that constitute the first step of tissue regeneration.

Composites Based on Hydroxyapatite and Whey Protein Isolate for Applications in Bone Regeneration

Hydroxyapatite (HAp) is a bioactive ceramic with great potential for the regeneration of the skeletal system. However, its mechanical properties, especially its brittleness, limit its application. Therefore, in order to increase its ability to transmit stresses, it can be combined with a polymer phase, which increases its strength without eliminating the important aspect of bioactivity. The presented work focuses on obtaining organic-inorganic hydrogel materials based on whey protein isolate (WPI) reinforced with nano-HAp powder. The proportion of the ceramic phase was in the range of 0-15%. Firstly, a physicochemical analysis of the materials was performed using XRD, FT-IR and SEM. The hydrogel composites were subjected to swelling capacity measurements, potentiometric and conductivity analysis, and in vitro tests in four liquids: distilled water, Ringer's fluid, artificial saliva, and simulated body fluid (SBF). The incubation results demonstrated the successful formation of new layers of apatite as a result of the interaction with the fluids. Additionally, the influence of the materials on the metabolic activity according to ISO 10993-5:2009 was evaluated by identifying direct contact cytotoxicity towards L-929 mouse fibroblasts, which served as a reference. Moreover, the stimulation of monocytes by hydrogels via the induction of nuclear factor (NF)-κB was investigated. The WPI/HAp composite hydrogels presented in this study therefore show great potential for use as novel bone substitutes.

Mechanochemical Synthesis of Nanocrystalline Hydroxyapatite from Ca(H2PO4)2.H2O, CaO, Ca(OH)2, and P2O5 Mixtures

This paper reports the progress of the mechanochemical synthesis of nanocrystalline hydroxyapatite (HA) starting from six different powder mixtures containing Ca(H₂PO₄)₂.H₂O, CaO, Ca(OH)₂, and P₂O₅. The reaction kinetics of HA phase formation during high-energy ball milling was systematically investigated. The mechanochemical reaction rate of the Ca(H₂PO₄)₂.H₂O–Ca(OH)₂ powder mixture found to be very fast as the HA phase started to form at around 2 min and finished after 30 min of ball milling. All six powder mixtures were transformed entirely into HA, with the crystallite size between 18.5 and 20.2 nm after 1 h and between 22.5 and 23.9 nm after 2 h of milling. Moreover, the lattice strain was found to be 0.8 ± 0.05% in the 1 h milled powder and 0.6 ± 0.05% in all six powders milled for 2 h. This observation, i.e., coarsening of the HA crystal and gradual decrease of the lattice strain with the increase of milling time, is opposite to the results reported by other researchers. The gradual increase in crystallite size and decrease in lattice strain result from dynamic recovery and recrystallization because of an increase in the local temperature of the powder particles trapped between the balls and ball and reactor wall during the high-energy collision.

Synthesis and characterization of biomimetic bioceramic nanoparticles with optimized physicochemical properties for bone tissue engineering

Calcium phosphate bioceramics nanoparticles such as nano-hydroxyapatite (nHA) and nano-tricalcium phosphate (nTCP) are the main focus of basic and applied research for bone tissue regeneration. In particular, a combination of these two phases (nHA + nTCP) which refers to as "nano-biphasic calcium phosphates (nBCP)" is of interest due to the preferred biodegradation nature compared to single-phase bioceramics. However, the available synthesis processes are challenging and the biomaterials properties are yet to be optimized to mimic the physiochemical properties of the natural nanoscale bone apatite. In this study, a new approach was developed for the production of optimized bioceramic nanoparticles aiming to improve their biomimecity for better biological performances. Nanoparticles were synthesized through a carefully controlled and modified wet mechano-chemical method combined with a controlled solid-state synthesis. Different processing variables have been analyzed including; milling parameters, post-synthesis treatment, and calcination phase. Detailed physicochemical characterizations of nanoparticles revealed higher crystallinity (∼100%), lower crystallite/particle size (58 nm), higher homogeneity, reduced particle agglomeration size (6 μm), and a closer molar ratio (1.8) to biological apatite compared to control and standard samples. Furthermore, the study group was confirmed as calcium-deficient carbonate-substituted BCP nanoparticles (nHA/nβ-TCP: 92/8%). As such, the introduced method can afford an easier and accurate control over nanoparticle physiochemical properties including the composition phase which can be used for better customization of biomaterials for clinical applications. The findings of this article will also help researchers in the further advancement of production strategies of biomaterials. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1654-1666, 2019.