Subramani: In Vitro Evaluation of Osteoblast Response and Activity on Carbon Nanotube-coated Titanium Surfaces

While Temporary Anchorage Devices (TADs) have become increasingly utilized by orthodontic professionals to assist in the process of moving teeth, commercially available TADs exhibit a disappointing 25 to 40% failure rate. Currently TADs are manufactured with smooth titanium surfaces (pure titanium or titanium alloy (Ti-6Al-4V)) because complete osseointegration is a disadvantage which complicates the removal of TADs. On the other hand, lack of osseointegration is also one of the factors for the failure of TADs. The success of TADs also depends on other factors like proper initial mechanical stability, loading quality and quantity. Clinically there are difficulties encountered in the removal of TADs due to increased osseointegration even on the smoother surface of the TADs. Therefore the balance lies in the fabrication of an ideal surface that could stimulate initial osseointegration and facilitate the removal of TADs once after the desired tooth movement is achieved. Having a layer of nanoscale structure like carbon nanotubes coated on the titanium surface would stimulate initial osseointegration and it is hypothesized that it can act as an interfacial layer facilitating the removal of TADs. We also hypothesize that TADs which are partially or fully coated with carbon nanotubes (CNTs), would exhibit a reduced failure rate over the current TADs without overly enhancing osseointegration that would impede their removal. To evaluate these hypotheses, we will test the biological responsiveness of rat bone marrow-derived osteoblasts to uncoated titanium surfaces and surfaces coated with functionalized/non-functionalized single or multi-walled CNTs in this in vitro study. Our objective is to evaluate osteoblast adhesion, proliferation and differentiation on these surfaces in vitro and to determine whether the presence of CNTs positively or negatively influence osteoblast response. We hope to identify a titanium surface coated with CNTs that will facilitate enhanced osteoblast adhesion and activity without producing adverse effects on osteoblast response. The specific aim of this in vitro study is to coat single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) on titanium surfaces (discs) and to evaluate osteoblast responses (adhesion, proliferation and differentiation) on these CNT-coated titanium substrates. Uncoated titanium surface and a glass substrate will be used as controls. Functionalized and non-functionalized CNTs will be coated on to titanium discs and the surface characteristics will be evaluated using Scanning Electron Microscopy and surface profilometry before cell culture experiments. Rat bone marrow-derived osteoblasts will be cultured on to these substrates and Scanning Electron Microscopy (SEM), confocal, fluorescent and Atomic Force Microscopy (AFM) will be employed to evaluate osteoblast adhesion, proliferation and differentiation using DNA, alkaline phosphatase, total protein analyses and mineralized matrix formation assays in cell culture. We hypothesize that carbon nanotube coated titanium surface can stimulate osteoblast adhesion, proliferation, differentiation and mineralized matrix formation in vitro. The effect of functionalized and non-functionalized SWCNT/MWCNT coating on titanium surface will also be evaluated in this study. The results from this in vitro study will be beneficial for the design of an ideal surface for evaluation in a separate animal study in the future. It will be of great scientific importance to the orthodontic community to explore further and utilize carbon nanotube-coated titanium surface for its applications in orthodontic mini-implants (TADs).