Surface modification of yttria-stabilised zirconia at nanoscale for in vitro study / Soon Ginny

Soon, Ginny (2018) Surface modification of yttria-stabilised zirconia at nanoscale for in vitro study / Soon Ginny. PhD thesis, University of Malaya.

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Abstract

This study has utilised a straightforward yet economical approach to fabricate arrays of nanoislands on miscut yttria-stabilised zirconia substrates. These self-assembled nanostructures were produced with two simple procedures: source deposition by powder-suspension-based method and annealing treatment. At varying dwell times, the nanostructures formed on the substrates were observed for their morphology, alignment, and coverage. The use of miscut surfaces has successfully improved the alignment and coverage of nanoislands, in which surfaces with different miscut angles also appeared to influence the spacing between them. Also, the introduction of miscut to the surface has demonstrated to be more effective in fabricating aligned nanostructures at a larger scale. The annealing treatment at 1100 oC for 5 h has fabricated significantly ordered nanoislands on 10-degree miscut substrates compared to other profiles in this work. Hence, these nanopatterned substrates underwent several characterisations prior to in vitro studies involving different types of cells. In particular, osteoblasts, primary bovine chondrocytes, and human mesenchymal stem cells have been used to explore the interaction between cells and nanostructures to ensure the good cytocompatibility of substrates. In comparison with the untreated substrates, the nanopatterned substrates were demonstrated to have a better affinity with water, in other words, a more hydrophilic surface. Their surface roughness at the nanoscale has also been enhanced due to the presence of nanostructures. Energy dispersive x-ray (EDX) and x-ray diffraction (XRD) results showed the respective elements found in the nanopatterned substrate and its phase wherein the elements contained in the substrate agreed well with the XRD results as well. In general, the cells have exhibited positive response in contact with the nanopatterned substrates. Both osteoblasts and chondrocytes have shown an up-regulated proliferation rate over time. Enhanced cell attachment has also been observed on the nanopatterned substrates, which was attributed to the surface qualities and the availability of extensive anchorage points. The osteoblast differentiation was also believed to be improved by the imposed nanostructures as the ALP activity and mineralisation process were more active compared to those on the control group. On the other hand, it is suggested that further measures are required to facilitate the functionality of cartilage tissue as the enhancement of chondrocyte function was not evident with the use of surface nanofeatures alone. The immunofluorescence staining has also illustrated an outstanding focal adhesion of human adiposed-derived mesenchymal stem cells (ADMSCs) on the nanopatterned samples. As expected, the ADMSC proliferation rate was significantly enhanced at different time intervals in comparison with the untreated samples. The osteogenic potential of nanostructures has also been highlighted in this study.

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