Nanoparticle-based model of anti-inflammatory drug releasing LbL coatings for uncemented prosthesis aseptic loosening prevention

Abstract

Introduction: The only treatment for aseptic loosening is the replacement of the prosthesis through revision surgery. A preventive approach, achieved through anti-inflammatory drugs released from the device, has shown to be a viable strategy; however, the performance of these devices is not yet satisfactory thus further improvements are necessary.

Methods: We used titanium nanoparticles as a model for implant surfaces and developed a coating containing dexamethasone (DEX) using layer-by-layer deposition.

Results: The amount of deposited drug depended on the number of layers and the release was sustained for months. The efficiency of the released DEX in reducing inflammation markers (tumor necrosis factor alpha and IL-6) produced by human monocytes and macrophages was similar to the pure drug at the same concentration without negative impacts on the viability and morphology of these cells.

Conclusion: These coatings were not inferior to medical grade titanium (the standard material used in uncemented devices) regarding their ability to sustain osteoblasts and fibroblasts growth.

Keywords: aseptic loosening; cementless prosthesis; dexamethasone; titanium.

Figure 1

Example of transmission electron microscopy images of (A) bare TiO₂ nanoparticles, (B) amino functionalized (TiO₂-NH₂) nanoparticles and (C) LbL coated (Q10). Bar represents 100 nm. (D) Thermograms of different LbL-DEX-coated Ti-O-NH₂ substrate. Abbreviations: DEX, dexamethasone; LbL, layer-by-layer.

Figure 2

Cumulative release of DEX from LbL-Ti-O-NH₂ surfaces at pH=5 (A) and pH=7.3 (B) for different number of quadruple layers (Q1, Q3, Q5, Q7 and Q10). Abbreviations: PBAE, poly-beta-amino-ester; DEX-P, dexamethasone phosphate.

Figure 3

Mitochondrial activity of activated (A) and non-activated (B) THP-1 cells exposed to media containing DEX-P or elutes from DEX released from LbL assembly for 6 and 24 hrs. LPS concentration of 1 µg/mL. Abbreviations: LPS, lipopolysaccharides; LbL, layer-by-layer; DEX, dexamethasone; DEX-P, dexamethasone phosphate.

Figure 4

IL-6 expression of activated (A) and non-activated (B); TNFα expression of activated (C) and nonactivated (D) THP-1 cells post-exposure to media containing DEX-P or elutes from DEX released from LbL assembly for 6 and 24 hrs. LPS concentration of 1 µg/mL was used. (* represents significant differences p<0.05) Abbreviations: DEX-P, dexamethasone phosphate; LbL, layer-by-layer; DEX, dexamethasone; LPS, lipopolysaccharides; TNFα, tumor necrosis factor alpha.

Figure 5

Actin staining epifluorescent images of human macrophages (A) LPS- DEX-; (B) LPS+ DEX-; (C) LPS+ DEX-P and (D) LPS+ DEX from release buffer after 24-hr exposure assessed by confocal microscopy. Actin rings and nuclei of cells were stained with phalloidin-FITC and DAPI, respectively; arrows indicate pseudopods. Bar corresponds to 20 µm. Abbreviations: LPS, lipopolysaccharides; DEX, dexamethasone; DEX-P, dexamethasone phosphate.

Figure 6

Mitochondrial activity of Saos-2 (A) and fibroblasts (B) cells exposed to media containing DEX-P or elutes from LbL assembly for 1, 2 and 3 days expressed as % of uncoated nanoparticles. (* represents significant differences compared to release from uncoated nanoparticles p<0.05). Abbreviations: DEX-P, dexamethasone phosphate; LbL, layer-by-layer.

Figure 7

Actin staining epifluorescent images of human osteoblast (Saos-2) (A) no DEX; (B) LPS; (C) LPS+ DEX-P and (D) DEX from release buffer after 24-hr exposure assessed by confocal microscopy. Actin rings and nuclei of cells were stained with phalloidin-FITC and DAPI, respectively. Bar corresponds to 20 µm. Abbreviations: LPS, lipopolysaccharides; DEX, dexamethasone; DEX-P, dexamethasone phosphate.

Figure 8

Actin staining epifluorescent images of human fibroblasts (A) no DEX; (B) LPS; (C) LPS+ DEX-P and (D) DEX from release buffer after 24-hr exposure assessed by confocal microscopy. Actin rings and nuclei of cells were stained with phalloidin-FITC and DAPI, respectively. Bar corresponds to 20 µm. Abbreviations: LPS, lipopolysaccharides; DEX, dexamethasone; DEX-P, dexamethasone phosphate.