Grafting titanium nitride surfaces with sodium styrene sulfonate thin films

Abstract

The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxynitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were $1.5 and $1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260 6 70 ng/cm 2

Response of mesenchymal stem cells to surface topography of scaffolds and the underlying mechanisms

“…One way to understand this is the design of surfaces where chemistries are arranged in different patterns that create different topological cues to control cell adhesion and hence the downstream signaling. Previous studies have shown that patterns of click chemistry, 11 photolithography (by UV crosslinking), [18][19][20] and alkanethiol self-assembled monolayers (SAMs) 21,22 all directed cell adhesion and lineage specification. For example, adhesive sites spaced 34 or 62 nm apart directed mesenchymal stem cells (MSCs) to mature into osteoblasts or adipose cells, respectively.…”

“…Due to micro/nanoscale fabrication method advancements, breakthroughs in materials surface modification techniques, such as acidic treatment, 8,9 nitride coatings, [10][11][12] and selective laser melting, [13][14][15] have enabled the manufacture of microand nanoscale surface structured scaffolds that more closely simulate the in vivo environment of stem cells. 16 As a result, scaffolds used for regeneration have progressed from the passive distribution of stem cells and chemical agents to controllably ''smart'' scaffolds that actively direct tissue regeneration.…”