|
Hydroxyapatite (HA) granules are frequently used in orthopedics and maxillofacial surgeries to
fill bone defects and stimulate the regeneration process. Optimal HA granules should have high
biocompatibility, high microporosity and/or mesoporosity, and high specific surface area (SSA), which
are essential for their bioabsorbability, high bioactivity (ability to form apatite layer on their surfaces)
and good osseointegration with the host tissue. Commercially available HA granules that are sintered
at high temperatures (≥ 900 °C) are biocompatible but show low porosity and SSA (2–5 m2/g), reduced
bioactivity, poor solubility and thereby, low bioabsorbability. HA granules of high microporosity
and SSA can be produced by applying low sintering temperatures (below 900 °C). Nevertheless,
although HA sintered at low temperatures shows significantly higher SSA (10–60 m2/g) and improved
bioabsorbability, it also exhibits high ion reactivity and cytotoxicity under in vitro conditions. The
latter is due to the presence of reaction by-products. Thus, the aim of this study was to fabricate novel
biomaterials in the form of granules, composed of hydroxyapatite nanopowder sintered at a high
temperature (1100 °C) and a biopolymer matrix: chitosan/agarose or chitosan/β-1,3-glucan (curdlan).
It was hypothesized that appropriately selected ingredients would ensure high biocompatibility
and microstructural properties comparable to HA sintered at low temperatures. Synthesized
granules were subjected to the evaluation of their biological, microstructural, physicochemical, and
mechanical properties. The obtained results showed that the developed nanocomposite granules
were characterized by a lack of cytotoxicity towards both mouse preosteoblasts and normal human
fetal osteoblasts, and supported cell adhesion to their surface. Moreover, produced biomaterials had
the ability to induce precipitation of apatite crystals after immersion in simulated body fluid, which,
combined with high biocompatibility, should ensure good osseointegration after implantation.
Additionally, nanocomposite granules possessed microstructural parameters similar to HA sintered at a
low temperature (porosity approx. 50%, SSA approx. 30 m²/g), Young’s modulus (5–8 GPa) comparable
to cancellous bone, and high fluid absorption capacity. Moreover, the nanocomposites were prone to
biodegradation under the influence of enzymatic solution and in an acidic environment. Additionally,
it was noted that the hydroxyapatite nanoparticles remaining after the physicochemical dissolution of
the biomaterial were easily phagocytosed by mouse macrophages, mouse preosteoblasts, and normal
human fetal osteoblasts (in vitro studies). The obtained materials show great potential as bone tissue
implantation biomaterials with improved bioresorbability. The obtained materials show great potential
as bone tissue implantation biomaterials with improved bioresorbability.
|
