Europium-doped hydroxyapatite nanorods suppress lipopolysaccharide-induced inflammation in human periodontal ligament cells and attenuate alveolar bone loss in experimental periodontitis

Abstract Objectives To compare the effects of europium-doped hydroxyapatite (Eu-HAP) and undoped hydroxyapatite (HAP) on primary human periodontal ligament cells after lipopolysaccharide (LPS) withdrawal and on alveolar bone in experimental periodontitis. Materials and Methods PEGylated nanorods were characterized and tested at 10 μg/mL in cells from three donors after a 24-h LPS challenge and washout. We measured inflammatory and osteogenic transcripts andalkaline phosphatase activity. Ligature-treated rats received bilateral gingival injections of saline, HAP or Eu-HAP on seven dates from days 7 to 25. Micro-CT and histology were assessed on day 28 (four rats/group). Results Eu-HAP contained 8.0 wt% Eu (12.5 mol% of total Eu and Ca, versus 5% in the feed); its hydrodynamic diameter was 321 nm by dynamic light scattering. Compared with HAP, Eu-HAP lowered TNF and IL1B expression and increased ALPL and SPP1 expression; RUNX2 did not differ. IL1B expression was 1.5 times the unchallenged mean with Eu-HAP and 5.3 times that mean after LPS alone. At day 28, Eu-HAP yielded a shortercemento-enamel junction–alveolar bone crest distance than HAP (0.44 vs 0.58 mm; P = 0.0406) and a higher bone volume fraction (80% vs 73%; P = 0.0492). Osteoclast density was 21 versus 39 cells/mm². Conclusions Eu-HAP reduced inflammatory transcripts and enhanced selected osteogenic responses after LPS withdrawal. In rats, local Eu-HAP preserved more alveolar bone at the endpoint than HAP. Clinical Relevance The findings support preclinical evaluation ofEu-HAP for periodontal bone preservation. Its benefit alongside standard periodontal care remains unknown.