Biofunctionalization of titanium implant with chitosan/siRNA complex through loading-controllable and time-saving cathodic electrodeposition

Although titanium (Ti) implants are already being broadly used, further improvement is still mandatory for improving its clinical performance. To this end, small interfering RNA (siRNA) biofunctionalization may present a novel strategy. In this study, siRNA biofunctionalization was realized on a titania nanotube array (TNT) on Ti by the cathodic electrodeposition (CED) of a chitosan (CS)/siRNA complex. The siRNA deposition amount was linearly correlated to the current density and the siRNA release profile was sensitive to the pH value of the surrounding solution. To confirm the activity of the cathodically electrodeposited siRNA, the siRNA targeting green fluorescent protein (siGFP) was introduced by CED, and the primary rat mesenchymal stem cells (rMSCs) encoding a GFP expression motif were seeded. High siRNA delivery efficiency and sustained target gene down-regulation were observed, which were much better than the conventional CS/siRNA nanoparticle delivery system and were related to the enhanced siRNA access into the cytoplasm. Simultaneously, good cytocompatibility was observed from the CS/siRNA biofunctionalization, as indicated by the good cell adhesion and viability. Finally, the siRNA targeting casein kinase-2 interacting protein-1 (siCkip-1), reported to have osteogenic potential, was introduced by CED to assess the potential of CS/siRNA biofunctionalization for application in bone implants. The CS/siCkip-1 biofunctionalization magnificently enhanced the osteogenic differentiation of rMSCs in terms of improved osteogenesis related gene expression, collagen secretion and calcium deposition, showing high promise for application in bone implants. The study demonstrates a new and convenient way to functionalize the biomedical metal implants with CS/siRNA for surface activation via local siRNA delivery.