Biomimetic Cell-Substrate of Chitosan-Cross-linked Polyaniline Patterning on TiO 2 Nanotubes Enables hBM-MSCs to Differentiate the Osteoblast Cell Type.

Titanium-based substrates are widely used in orthopedic treatments and hard tissue engineering. However, many of these titanium (Ti) substrates fail to interact properly between the cell-to-implant interface, which can lead to loosening and dislocation from the implant site. As a result, scaffold implant-associated complications and the need for multiple surgeries lead to an increased clinical burden. To address these challenges, we engineered osteoconductive and osteoinductive biosubstrates of chitosan (CS)-cross-linked polyaniline (PANI) nanonets coated on titanium nanotubes (TiO ₂ NTs) in an attempt to mimic bone tissue's major extracellular matrix. Inspired by the architectural and tunable mechanical properties of such tissue, the TiO ₂ NTs-PANI@CS-based biofilm conferred strong anticorrosion, the ability to nucleate hydroxyapatite nanoparticles, and excellent biocompatibility with human bone marrow-derived mesenchymal stem cells (hBM-MSCs). An in vitro study showed that the substrate-supported cell activities induced greater cell proliferation and differentiation compared to cell-TiO ₂ NTs alone. Notably, the bone-related genes (collagen-I, OPN, OCN, and RUNX 2) were highly expressed within TiO ₂ NTs-PANI@CS over a period of 14 days, indicating greater bone cell differentiation. These findings demonstrate that the in vitro functionality of the cells on the osteoinductive-like platform of TiO ₂ NTs-PANI@CS improves the efficiency for osteoblastic cell regeneration and that the substrate potentially has utility in bone tissue engineering applications.