Biocompatible Germanium-Enriched Nanocomposite Coatings on Titanium Designed Toward Preventing Early Inflammation and Promoting Osteogenic Differentiation

Abstract

The study seeks to develop a multifunctional germanium-enriched nanocomposite coating on titanium and to evaluate its ability to modulate early inflammatory responses while promoting osteogenic differentiation in a dental pulp stem cell (DPSC)-based regenerative model. A multifunctional Ti/Coating composed of nanohydroxyapatite (nHAp) particles, chitosan-oligolactate (ChOL), and germanium (Ge) was developed using a combined anodizing/anaphoretic electrodeposition approach. The Ti/Coating system exhibited good biocompatibility, as confirmed by microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays, with cell viability consistently exceeding 90% and moderate LDH release across all time points. Annexin V/PI assay demonstrated a predominance of viable cells (>94%), while intracellular ROS analysis indicated moderate oxidative activity. Gene expression analysis revealed significant downregulation of pro-inflammatory markers (TNF-α, IL-1β, IL-6, COX-2, and MAPK), suggesting attenuation of inflammatory signalling. Flow cytometry further demonstrated reduced CD120b (TNFR2) expression, while intracellular TNF-α levels remained unchanged, indicating selective modulation at the receptor level. In addition, the Ti/Coating promoted osteogenic differentiation, as evidenced by enhanced mineralization, and upregulation of osteogenic genes (ALP, RUNX2, BMP2).