Enhanced Interfacial Adhesion and Osteogenesis for Rapid “Bone-like” Biomineralization by PECVD-Based Silicon Oxynitride Overlays

Abstract

Structurally unstable fracture sites require metal fixative devices, which have long healing times due to their lack of osteoinductivity. Bioactive glass coatings lack in interfacial bonding, delaminate, and have reduced bioactivity due to the high temperatures used for their fabrication. Here, we test the hypothesis that low-temperature PECVD amorphous silica can enhance adhesion to the underlying metal surface and that N incorporation enhances osteogenesis and rapid biomineralization. A model Ti/TiO2-SiOx interface was formed by first depositing Ti onto Si wafers, followed by surface patterning, thermal annealing to form TiO2, and depositing SiOx/Si(ON)x overlays. TEM micrographs showed conformal SiOx layers on Ti/TiO2 overlays while XPS data revealed the formation of an elemental Ti-O-Si interface. Nanoscratch testing verified strong SiOx bonding with the underlying TiO2 layers. In vitro studies showed that the surface properties changed significantly to reveal the formation of hydroxycarbonate apatite within 6 h, and Si(ON)x surface chemistry induced osteogenic gene expression of human periosteal cells and led to a rapid "bone-like" biomineral formation within 4 weeks. XANES data revealed that the incorporation of N increased the surface HA bioactivity by increasing the carbonate to phosphate ratio. In conclusion, silicon oxynitride overlays on bone-implant systems enhance osteogenesis and biomineralization via surface nitrogen incorporation.

Silicon nitride enhances osteoprogenitor cell growth and differentiation via increased surface energy and formation of amide and nanocrystalline HA for craniofacial reconstruction

“…In this study, evaluations of the Si L‐ edge and Y M‐edge were conducted at the National Synchrotron Light Source facility (Canadian Light Source, CLS, University of Saskatchewan, Saskatoon, Saskatchewan, Canada). Details of the beam energy for each studied element are given in previous publications (Ilyas et al, , ; Varanasi et al, ) and in the Results section below. XANES analysis was used to determine the presence of Si‐O, Si‐N and Si‐Si bonds and how the presence of Yttrium affects these coordination structures.…”

“…This was attributed to many factors, including its surface chemistry, hydrophilicity and its strong electronegative surface sites, which promoted cell attachment and migration when compared to HA, Ti or PEEK (Bock et al, ; Pezzotti et al, ; Pezzotti, McEntire, Bock, Zhu, et al,). Based on prior work with amorphous silicon nitride (Ilyas, Lavrik, Kim, Aswath, & Varanasi, ), the presence of surface nitrogen induces the formation of N‐H moieties that act as precursors to the amide groups present in collagenous extracellular matrix (ECM). These moieties (e.g., Si‐N or N‐H bonding) in amorphous silicon nitride (index of refraction = 2.02) elevated specific expression of runt‐related transcription factor 2 (RUNX2), a key transcription factor involved in rapid regeneration of new bone, by nearly 2.5‐fold versus control‐treated samples (Ilyas et al, ).…”

Ionic silicon improves endothelial cells' survival under toxic oxidative stress by overexpressing angiogenic markers and antioxidant enzymes

“…All coatings were processed at a substrate temperature of 400°C, a chamber pressure of 900 mTorr, an inductively coupled plasma (ICP) power of 30 W, and an applied excitation frequency of 13.56 MHz. The source and flow rate of gas were as follows: 24 for SiH 4 /AR (15/85%), 155 for N 2 O, 225 for N 2 , and 50 for NH 4 (Ilyas et al, , ).…”

Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD)

“…53 For the PVD and PE-CVD SiO x layers, the silanol surface groups could act as binding sites for CaP related products. 52 As shown by the water contact angle measurements, the PVD film exhibits a higher hydrophilicity indicating a higher silanol surface density in comparison to the PE-CVD films. As such, despite the observed partial delamination of the PVD film after exposure to 37 °C SBF for 28 days, the Ca and P uptake was around 1-2 % and comparably higher than on the PE-CVD film where both elements were detected only in trace amounts < 1 %.…”

“…Biomineralization on SiO x based 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 22 films depends greatly on the stoichiometry and surface chemistry of the deposited film as well as its interfacial stability. 45,52 The presence of high densities of functional groups such as the applied -NH 2 and -SO 3 H moieties coupled to the SiO x surface can play an important role in shielding the film from intruding water and ions and therefore increase its resistance to delamination as well as potentially serve as nucleation seeds for the growth of important biominerals such as hydroxyapatite. 53 Analyses of the individual elemental film composition by EDX and XPS reveal several significant differences between PVD-P and PE-CVD-P.…”