In vitro effect of a corrosive hostile ocular surface on candidate biomaterials for keratoprosthesis skirt

Abstract

Aim: Keratoprosthesis (KPro) devices are prone to long-term corrosion and microbiological assault. The authors aimed to compare the inflammatory response and material dissolution properties of two candidate KPro skirt materials, hydroxyapatite (HA) and titania (TiO(2)) in a simulated in vitro cornea inflammation environment.

Methods: Lipopolysaccharide-stimulated cytokine secretions were evaluated with human corneal fibroblasts on both HA and TiO(2). Material specimens were subjected to electrochemical and long-term incubation test with artificial tear fluid (ATF) of various acidities. Topography and surface roughness of material discs were analysed by scanning electron microscopy and atomic force microscopy.

Results: There were less cytokines secreted from human corneal fibroblasts seeded on TiO(2) substrates as compared with HA. TiO(2) was more resistant to the corrosion effect caused by acidic ATF in contrast to HA. Moreover, the elemental composition of TiO(2) was more stable than HA after long-term incubation with ATF.

Conclusions: TiO(2) is more resistant to inflammatory degradation and has a higher corrosion resistance as compared with HA, and in this regard may be a suitable material to replace HA as an osteo-odonto-keratoprosthesis skirt. This would reduce resorption rates for KPro surgery.

Figure 1

Fold change of cytokine expression level at the material surface of lipopolysaccharide (LPS)-stimulated human cornea fibroblasts. All data are relative to the readings of their individual group without LPS treatment. Data are represented as mean ± SE. *p<0.05 between hydroxyapatite (HA) and (titania) TiO_2. bFGF: basic fibroblastic growth factor, G-CSF: granulocyte colony-stimulating factor, GM-CSF: granulocytes macrophage colony-stimulating factor, GS: glass slide. n=6, IFN: interferon, IL: interleukin, IP: induced protein, MIP: macrophage inflammatory protein, TNF: tumour necrosis factor, VEGF: vascular endothelial growth factor.

Figure 2

Representative scanning electronic microscopy (SEM) images of hydroxyapatite (HA) and titania (TiO₂) for electrochemical test. A_1–3: HA; B_1–3: TiO₂. A₁ and B₁: Before treatment; A₂ and B₂: After electrochemical test in artificial tear fluid at pH 6.5; A₃ and B₃: After electrochemical test in artificial tear fluid at pH 5. The scale bar in all images is 10 μm.

Figure 3

Atomic force microscopy (AFM) scanning and data analysing of hydroxyapatite (HA) and titania (TiO₂) for electrochemical test. A: Representative 3D topography of material discs. A_1–3: HA; A_4–6: TiO₂. A₁ and A₄: Before treatment; A₂ and A₅: After electrochemical test in artificial tear fluid at pH 6.5; A₃ and A₆: After electrochemical test in artificial tear fluid at pH 5. B: Histogram showing the relationship of average roughness (Ra) with pH value of artificial tear fluid. All data are normalised to untreated specimens and represented as mean ± SE. n=12.

Figure 4

Representative scanning electronic microscopy (SEM) images of hydroxyapatite (HA) and titania (TiO₂) for long-term corrosion test. A_1–3: HA; B_1–3: TiO₂. A₁ and B₁: Before treatment; A₂ and B₂: After long-term incubation in artificial tear fluid at pH 6.5; A₃ and B₃: After long-term incubation in artificial tear fluid at pH 5. The scale bar in all images is 10 μm.

Figure 5

Atomic force microscopy (AFM) scanning and data analysing of hydroxyapatite (HA) and titania (TiO₂) for long-term corrosion test. A: Representative 3D topography of material discs. A_1–3: HA; A_4–6: TiO₂. A₁ and A₄: Before treatment; A₂ and A₅: After long-term corrosion test in artificial tear fluid at pH 6.5; A₃ and A₆: After long-term corrosion test in artificial tear fluid at pH 5. B: Histogram showing the relationship of average roughness (Ra) with pH value of artificial tear fluid. All data are normalised to untreated specimens and represented as mean ± SE. n=12.