Amidoxime-Containing Zr and Hf Atomic Layer Deposition Precursors for Metal Oxide Thin Films.

In this article, we discuss the synthesis of eight novel zirconium and hafnium complexes containing amidoxime ligands as potential precursors for atomic layer deposition (ALD). Two amidoximes, viz., (E)-N'-hydroxy-N,N-dimethylacetimidamide (mdaoH) and (Z)-N'-hydroxy-N,N-dimethylpivalimidamide (tdaoH), along with their Zr and Hf homoleptic complexes, Zr(mdao)4 (1), Hf(mdao)4 (2), Zr(tdao)4 (3), and Hf(tdao)4 (4) were prepared. We further synthesized heteroleptic compounds with different physical properties by introducing cyclopentadienyl (Cp) ligand, namely, CpZr(mdao)3 (5), CpHf(mdao)3 (6), CpZr(tdao)3 (7), and CpHf(tdao)3 (8). Thermogravimetric analysis was used for the assessment of the evaporation characteristics of complexes 1, 2, 5, and 6, and it revealed multistep weight losses with high residues. On the other hand, the thermogravimetric analysis curves of complexes 3, 4, 7, and 8 comprising tdao ligands revealed single-step weight losses with moderate residues. Single-crystal X-ray diffraction studies of complexes 1, 3, and 7 showed that all of the complexes have monomeric molecular structures. Complex 7 exhibited a low melting point (75 °C), good volatility, and high thermal stability compared with other complexes. Therefore, an atomic layer deposition process for the growth of ZrO2 was developed by using ZrCp(tdao)3 (7) as a novel precursor.

Influence of growth temperature on dielectric strength of Al2O3 thin films prepared via atomic layer deposition at low temperature.

Thin films grown via atomic layer deposition (ALD) suffer from insufficient growth rate and unreliability for temperature-sensitive electronic substrates. This study aimed to examine the growth characteristics and dielectric strength of ALD Al2O3 films grown at low temperatures (≤ 150 °C) for potential application in flexible electronic devices. The growth rate of the Al2O3 films increased from 0.9 to 1.1 Å/cycle with increasing temperature and saturated at growth temperatures ≥ 150 °C, which is the critical temperature at which a complete oxidation reaction occurred. The dielectric strength was also improved with increasing growth temperature, and the films grown at 150 °C showed a high breakdown field strength (~ 8.3 MV/cm), attributable to the decrease in the carbon impurities and oxygen defects, as confirmed by X-ray photoelectron spectroscopy. Even at low growth temperatures (≤ 150 °C), ALD Al2O3 films showed an overall amorphous structure and extremely smooth surfaces regardless of the growth temperature.

Comparative analysis of fixation configurations and their effect on outcome after medial open-wedge high tibial osteotomy.

PURPOSE: The purposes of this study were to analyze and compare 1) the postoperative fixation configurations, and 2) radiological and clinical outcomes between the new conceptual fixation device (LCfit) and the conventional locking plates. METHODS: Retrospective comparative analysis of 304 cases who underwent open-wedge high tibial osteotomy with four different locking plate systems including the LCfit system was conducted. In analyzing the fixation configuration of each locking plate system, the plate position, the gap between plate and bone, screw angle, and screw length were evaluated from postoperative CT scans. The clinical outcomes and radiological parameters of four patient groups corresponding to the four locking plate systems were also compared. RESULTS: In the analysis of the fixation configurations, the LCfit system showed more posteromedial plate position, decreased gap between plate and bone, reduced screw angle, and longer screw length compared to the other three locking plates. However, there were no significant differences in clinical outcomes and radiological parameters such as hip-knee-ankle angle, weight-bearing line position, medial proximal tibial angle, and posterior slope between the four groups. CONCLUSION: The newly designed fixation system (LCfit) for open-wedge high tibial osteotomy showed fixation configurations that have theoretical mechanical advantages over conventional anatomical locking plates. However, there were no significant differences in clinical outcomes and radiological parameters between LCfit and the other locking plate systems. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Retro-tubercular gap widening can be caused by inappropriate anterior osteotomy and large opening gap in the medial biplanar open-wedge HTO.

PURPOSE: The purpose of this study was to investigate the causes of retro-tubercular gap widening and to confirm whether this widened gap causes instability of the osteotomy configuration during open-wedge high tibial osteotomy (OWHTO). METHODS: Operative records and radiologic findings of patients who underwent biplanar medial OWHTO between 2014 and 2016 were retrospectively evaluated. To identify the osteotomy configuration including lateral hinge fracture, postoperative simple radiographs and CT images were analyzed. Postoperative CT scan was used to evaluate the widening of the retro-tubercular gap, thickness, and axial angle of retro-tubercular osteotomy, as well as the ratios of anterior and posterior osteotomy, and hinge length. The correlation of each factor was evaluated and analyzed in accordance with the lateral hinge fracture (LHF). RESULTS: Widening of the retro-tubercular gap showed a significant correlation with the axial angle of retro-tubercular osteotomy, anterior osteotomy ratio, and opening gap distance, but not with the thickness of retro-tubercular osteotomy, posterior osteotomy ratio, and hinge length ratio. The LHF group showed significantly larger value than the non-LHF group with respect to the thickness of retro-tubercular osteotomy (P = 0.003), axial angle of retro-tubercular osteotomy (P = 0.033), retro-planar gap distance (P = 0.001), anterior osteotomy ratio (P = 0.000), and opening gap distance (P = 0.003). The hinge length ratio was smaller in the LHF group than in the non-LHF group (P = 0.001). However, the posterior osteotomy ratio was not different between the two groups (n.s.). CONCLUSION: Retro-tubercular gap widening can be caused by inappropriate anterior osteotomy and large opening gap distance, which can be related to LHF. Therefore, anterior cortical osteotomy may also be an important factor for preventing instability of the proximal fragment in biplanar OWHTO. LEVEL OF EVIDENCE: Case-control study, Level III.

Assembly of collagen-binding peptide with collagen as a bioactive scaffold for osteogenesis in vitro and in vivo.

Bioactive scaffolds inducing cell adhesion, differentiation have been premise for optimal formation of target tissue. Collagen has been employed as a tissue regenerative scaffold especially for bone regeneration and has been chemically surface-modified to present bioactivity. Herein, we show that peptide, denoted as collagen-binding motif (CBM, GLRSKSKKFRRPDIQYPDATDEDITSHM) identified from osteopontin (OPN) protein, was able to specifically bind collagen without chemical conjugation, while presenting apatite forming capability in vitro and in vivo. Collagen surface alone was not able to induce noticeable apatite nucleation however, mineralization was evident when assembled with CBM peptide, implying that the collagen-CBM assembly played a pivotal role in biomineralization. In vivo result further demonstrated that the CBM peptide in complex with material was able to induce bone formation by helping mineralization in the bone defect. Taken together, the CBM peptide herein and its assembly with collagen can be applied as an inducer of biomineralization as well as a bioactive scaffold for bone regeneration.

Characterization of the surface immobilized synthetic heparin binding domain derived from human fibroblast growth factor-2 and its effect on osteoblast differentiation.

Fibroblast growth factor (FGF)-2 regulates a variety of cellular functions, such as proliferation and differentiation, by binding to cell surface FGF receptors (FGFRs) in the presence of heparin proteoglycans. FGF-2 is known as a heparin-binding growth factor, but the localization of the heparin binding site has not been fully investigated until now. We used two potential heparin binding domains of FGF-2, the residues 105-111 (F105, YKRSRYT) and 119-135 (F119, KRTGQYKLGSKTGPGQK). Peptides could be stably immobilized onto the surface of tissue culture plates. Using solid phase binding assays, we demonstrated that both peptides had higher binding affinity toward heparin compared with nonbinding control sequence. The biological significance of these sites was tested by cell attachment and osteoblast differentiation studies. Cell attachment to the peptides F105 and F119 increased in a dose-dependent manner. Heparin and heparinase treatments decreased cell adhesion to both F105 and F119. This demonstrates that both F105 and F119 interact with cell-surface heparan sulfate proteoglycans, suggesting that FGF-2 has two heparin binding sites. In addition, osteoblast differentiation, confirmed by ALPase activity and mineralization, was increased by surface immobilized peptide F105 and F119. Taken together, these heparin binding peptides could be applied as biological agents enhancing osteoblast differentiation as well as surface modification tools in the tissue regeneration area, especially for bone regeneration.