Inflammatory cell response to ultra-thin amorphous and crystalline hydroxyapatite surfaces

Abstract

It has been suggested that surface modification with a thin hydroxyapatite (HA) coating enhances the osseointegration of titanium implants. However, there is insufficient information about the biological processes involved in the HA-induced response. This study aimed to investigate the inflammatory cell response to titanium implants with either amorphous or crystalline thin HA. Human mononuclear cells were cultured on titanium discs with a machined surface or with a thin, 0.1 μm, amorphous or crystalline HA coating. Cells were cultured for 24 and 96 h, with and without lipopolysaccharide (LPS) stimulation. The surfaces were characterized with respect to chemistry, phase composition, wettability and topography. Biological analyses included the percentage of implant-adherent cells and the secretion of pro-inflammatory cytokine (TNF-α) and growth factors (BMP-2 and TGF-β1). Crystalline HA revealed a smooth surface, whereas the amorphous HA displayed a porous structure, at nano-scale, and a hydrophobic surface. Higher TNF-α secretion and a higher ratio of adherent cells were demonstrated for the amorphous HA compared with the crystalline HA. TGF-β1 secretion was detected in all groups, but without any difference. No BMP-2 secretion was detected in any of the groups. The addition of LPS resulted in a significant increase in TNF-α in all groups, whereas TGF-β1 was not affected. Taken together, the results show that thin HA coatings with similar micro-roughness but a different phase composition, nano-scale roughness and wettability are associated with different monocyte responses. In the absence of strong inflammatory stimuli, crystalline hydroxyapatite elicits a lower inflammatory response compared with amorphous hydroxyapatite.

Biomimetic Calcium Phosphate Coatings for Bioactivation of Titanium Implant Surfaces: Methodological Approach and In Vitro Evaluation of Biocompatibility

“…HA coatings are known to improve the cell attachment and proliferation of bone marrow-derived mesenchymal stem cells (BMSC) and osteoblast-like cells [16][17][18]. Likewise, the amorphous HA coatings used in this study had a beneficial impact on the osteoblastic expansion, confirming the results of Rydén et al [74]. Cells seeded on amorphous HA adhered in a higher cell number compared to Ti and crystalline HA after 24 h [74].…”

Nanofibrillar cellulose wound dressing supports the growth and characteristics of human mesenchymal stem/stromal cells without cell adhesion coatings

“…In addition, the angiogenic potential of hASCs was evaluated by measuring their expression of FGF2 and VEGF. In the preliminary results with lower cell densities, we observed increased FGF2, IL-6, and TNF-α secretion in cells grown on NFC dressing, which may indicate a reaction towards a foreign material [65], result from suboptimal cell density, or propose enhanced angiogenic potential and/or wound healing properties of hASCs on NFC [66]. On the other hand, the used gelatin coating on NFC dressing during the preliminary experiments may have influenced the results since gelatin has been shown to affect cell behavior and pro-inflammatory cytokine secretion [67].…”

“…Since hASCs have a natural capability to affect the wound healing process and to modulate the immune reaction by secreting a wide variety of cytokines and growth factors, we evaluated their inflammatory response by measuring pro-inflammatory cytokines IL-6 and TNF-α [65]. In addition, the angiogenic potential of hASCs was evaluated by measuring their expression of FGF2 and VEGF.…”

Delivery of Mesenchymal Stem Cells from Gelatin–Alginate Hydrogels to Stomach Lumen for Treatment of Gastroparesis

“…The absence of other lower-angle diffraction peaks of alginate (at 13.570° and 22.750° [ 30 ]) and the characteristic peak of gelatin (at 2θ = 20.90° for triple-helical crystalline structure [ 31 ]) show the strong interactions between alginate and gelatin in the scaffold and more crystalline characteristics [ 32 ]. The crystalline nature indicates that the gelatin was modified with alginate after being crosslinked, which can provide better tissue culture properties for the scaffold, such as cell adhesion, hydrophilicity, increased biomechanical functionality, and biodegradation rate [ 33 ]. The components of the gelatin–alginate scaffold were determined by FTIR spectroscopy after being frozen and lyophilized.…”