Crystallographically engineered, hydrothermally crystallized hydroxyapatite films: an in vitro study of bioactivity

Abstract

The aim of this study was to evaluate the bioactivity of hydroxyapatite films composed of hexagonal single crystals that display {1010} and {0001} crystallographic faces. The effect of engineered [0001] crystallographic orientation was investigated in parallel. Films were deposited by triethyl phosphate/ethylenediamine-tetraacetic acid doubly regulated hydrothermal crystallization on Ti6Al4V substrates (10, 14, 24 h). Bioactivity was investigated by analysis of MC3T3-E1 pre-osteoblast spreading using scanning electron microscopy and quantitative analysis of cell metabolic activity (Alamar Blue) (0-28 days). Scanning electron microscopy and X-ray diffraction were used to evaluate the ability of films to support the differentiation of MC3T3-E1 pre-osteoblasts into matrix-secreting, mineralizing osteoblasts. Results demonstrated that all films enabled MC3T3-E1 cells to spread, grow, and differentiate into matrix-secreting osteoblasts, which deposited biomineral that could not be removed after extraction of organic material. Differences in [0001] HA crystallographic orientation were not, however, found to significantly affect bioactivity. Based on these results, it is concluded that these hydrothermal hydroxyapatite films are non-toxic, bioactive, osteoconductive, and biomineral bonding. The lack of a relationship between reported hydroxyapatite crystallographic face specific protein adsorption and bulk HA bioactivity are discussed in terms of crystallographic texture, surface roughness, assay robustness, and competitive protein adsorption.

Effect of Calcium Phosphate Particle Shape and Size on Their Antibacterial and Osteogenic Activity in the Delivery of Antibiotics in Vitro

“…Still, no directly observable damaging effects of any of the materials on cells was observed during this phenotypic assessment. Single-plane imaging of the interface between the cells and the microscopic particle conglomerates (Figure 11a) demonstrated good spreading of osteoblastic cells on their surfacethe effect which is a direct morphological indicator of osteoconductivity of the given surface 34 and that particularly in the case of sample D (Figure 11a,b). The blue-stained cell nucleus was correspondingly observed elongated in the direction of the particle surface, while the red-stained f-actin cytoskeleton fully enwrapped it, suggesting an intimate contact between the biological and the inorganic phase.…”

Osteogenic and antimicrobial nanoparticulate calcium phosphate and poly-(d,l-lactide-co-glycolide) powders for the treatment of osteomyelitis

“…Blue-stained cell nucleus is correspondingly observed elongated in the direction of the particle surface, while red-stained factin cytoskeleton of confluent cells typically fully enwraps the particle surface (Figs.8, 10a, 12). The intimate interaction between the cells and the particles, being a direct morphological indicator of the surface’s osteoconductivity [22], was evidenced for all the sparsely soluble CAP phases, with or without loaded CL: HAP, ACP and DCPA (Figs.8, 9, 12). No significant difference in cell response to CAP particles was observed depending on whether the incubation lasted for 7, 10 or 21 days.…”

Effect of microstructure characteristics on tetracalcium phosphate–nanomonetite cement in vitro cytotoxicity

“…Interesting results were found in papers focused on the role of nanohydroxyapatite particle morphology or nanotopography on the adherence and proliferation of osteoblasts. The small morphological change of nanohydroxyapatite particles from spherical to needle-like (size < 100 nm) caused about a 50% reduction in cell proliferation [43] but no differences between the specific protein adsorption or osteoblast proliferation on hydrothermally crystallized hydroxyapatite films with various crystallographic orientation of hydroxyapatite and the film roughness were demonstrated [44]. Similarly, a lower cell density was observed on hydroxyapatite substrates with the needle-like particles than on substrates composed of the spherical particles and a more detailed study of the protein adsorption suggested an increase in the migration of osteoblasts on hydroxyapatite with spherical nanoparticles compared with the needle-like shaped hydroxyapatite [45].…”