| 1. |
- Cai, Yixiao, 1986-
(författare)
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Bio-Nano Interactions : Synthesis, Functionalization and Characterization of Biomaterial Interfaces
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Current strategies for designing biomaterials involve creating materials and interfaces that interact with biomolecules, cells and tissues. This thesis aims to investigate several bioactive surfaces, such as nanocrystalline diamond (NCD), hydroxyapatite (HA) and single crystalline titanium dioxide, in terms of material synthesis, surface functionalization and characterization.Although cochlear implants (CIs) have been proven to be clinically successful, the efficiency of these implants still needs to be improved. A CI typically only has 12-20 electrodes while the ear has approximately 3400 inner hair cells. A type of micro-textured NCD surface that consists of micrometre-sized nail-head-shaped pillars was fabricated. Auditory neurons showed a strong affinity for the surface of the NCD pillars, and the technique could be used for neural guidance and to increase the number of stimulation points, leading to CIs with improved performance.Typical transparent ceramics are fabricated using pressure-assisted sintering techniques. However, the development of a simple energy-efficient production method remains a challenge. A simple approach to fabricating translucent nano-ceramics was developed by controlling the morphology of the starting ceramic particles. Translucent nano-ceramics, including HA and strontium substituted HA, could be produced via a simple filtration process followed by pressure-less sintering. Furthermore, the application of such materials as a window material was investigated. The results show that MC3T3 cells could be observed through the translucent HA ceramic for up to 7 days. The living fluorescent staining confirmed that the MC3T3 cells were visible throughout the culture period.Single crystalline rutile possesses in vitro bioactivity, and the crystalline direction affects HA formation. The HA growth on (001), (100) and (110) faces was investigated in a simulated body fluid in the presence of fibronectin (FN) via two different processes. The HA layers on each face were analysed using different characterization techniques, revealing that the interfacial energies could be altered by the pre-adsorbed FN, which influenced HA formation.In summary, micro textured NCD, and translucent HA and FN functionalized single crystalline rutile, and their interactions with cells and biomimetic HA were studied. The results showed that controlled surface properties are important for enhancing a material’s biological performance.
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| 2. |
- Cai, Yixiao, et al.
(författare)
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Bioderived Calcite as Electrolyte for Solid Oxide Fuel Cells : A Strategy toward Utilization of Waste Shells
- 2017
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 5:11, s. 10387-10395
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Tidskriftsartikel (refereegranskat)abstract
- The excessive consumption of synthesized materials and enhanced environmental protection protocols necessitate the exploitation of desirable functionalities to handle our solid waste. Through a simple calcination and composite strategy, this work envisages the first application of biocalcite derived from the waste of crayfish shells as an electrolyte for solid oxide fuel cells (SOFCs), which demonstrates encouraging performances within a low temperature range of 450-550 degrees C. The single cell device, assembled from calcined waste shells at 600 degrees C (CWS600), enables a peak power density of 166 mW cm(-2) at 550 degrees C, and further renders 330 and 256 mW cm(-2) after compositing with perovskite La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF) and layer-structured LiNi0.8Co0.15Al0.05O2 (LNCA), respectively. Notably, an oxygen-ion blocking fuel cell is used to confirm the proton-conducting property of CWS600 associated electrolytes. The practical potential of the prepared fuel cells is also validated when the cell voltage of the cell is kept constant value over 10 h during a galvanostatic operation using a CWS600-LSCF electrolyte. These interesting findings may increase the likelihood of transforming our solid municipal waste into electrochemical energy devices, and also importantly, provide an underlying approach for discovering novel electrolytes for low-temperature SOFCs.
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| 3. |
- Cai, Yixiao, et al.
(författare)
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Biomineralization on Single Crystalline Rutile : The Modulated Growth of Hydroxyapatite by Fibronectin in a Simulated Body Fluid
- 2016
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Ingår i: RSC Advances. - 2046-2069. ; 6, s. 35507-35516
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to probe the complex interaction between surface bioactivity and protein adsorption on single crystalline rutile. Our previous studies have shown that single crystalline rutile possessed in vitro bioactivity and the crystalline faces affected the hydroxyapatite (HA) formation. However, upon implantation, a fast adsorption of proteins, from the biological fluids, is intermediated by a water layer towards the biomaterial interface. Thus the effect of protein on the bioactivity must be addressed. In this study, the HA growth dynamics on (001), (100) and (110) faces was investigated in a simulated body fluid with the presence of fibronectin (FN) by two different processes. The surface adhesion of each face before and after FN adsorption, as revealed by direct numerical values, was determined by atomic force microscopy (AFM) based peak force quantitative nanomechanical mapping (PF-QNM) for the first time. The findings suggest the surface energies of FN pre-adsorbed (001), (100) and (110) faces have been enhanced, leading to the subsequent accelerated HA formation. Furthermore, (001) and (100) faces were found to have larger coverage of HA crystals than (110) face at an early stage. In addition, various characterizations were performed to probe the chemical and crystal structures of as-grown biomimetic HA crystals, and in particular, the Ca/P ratio variations at different soaking time points.
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| 4. |
- Cai, Yixiao, et al.
(författare)
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Changes in secondary structure of alpha-synuclein during oligomerization induced by reactive aldehydes
- 2015
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 464:1, s. 336-341
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Tidskriftsartikel (refereegranskat)abstract
- The oxidative stress-related reactive aldehydes 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) have been shown to promote formation of alpha-synuclein oligomers in vitro. However, the changes in secondary structure of alpha-synuclein and the kinetics of the oligomerization process are not known and were the focus of this study. Size exclusion chromatography showed that after 1 h of incubation, HNE induced the formation of an oligomeric alpha-synuclein peak with a molecular weight of about similar to 2000 kDa, which coincided with a decreasing similar to 50 kDa monomeric peak. With prolonged incubation (up to 24 h) the oligomeric peak became the dominating molecular species. In contrast, in the presence of ONE, a similar to 2000 oligomeric peak was exclusively observed after 15 min of incubation and this peak remained constant with prolonged incubation. Western blot analysis of HNE-induced alpha-synuclein oligomers showed the presence of monomers (15 kDa), SDS-resistant low molecular (30-160 kDa) and high molecular weight oligomers (>= 260 kDa), indicating that the oligomers consisted of both covalent and non-covalent protein. In contrast, ONE-induced alpha-synuclein oligomers only migrated as covalent cross-linked high molecular-weight material (>= 300 kDa). Both circular dichroism (CD) and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy showed that the formation of HNE- and ONE-induced oligomers coincided with a spectral change from random coil to beta-sheet. However, ONE-induced alpha-synuclein oligomers exhibited a slightly higher degree of beta-sheet. Taken together, our results indicate that both HNE and ONE induce a change from random coil to beta-sheet structure that coincides with the formation of alpha-synuclein oligomers; albeit through different kinetic pathways depending on the degree of cross-linking. (C) 2015 Elsevier Inc. All rights reserved.
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| 5. |
- Cai, Yixiao, et al.
(författare)
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Fabrication of translucent nanoceramics via a simple filtration method
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:121, s. 99848-99855
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Tidskriftsartikel (refereegranskat)abstract
- Generally, particle packing density, grain size and morphology are the important factors that affect the transparency of ceramics. In order to achieve better transparency of ceramics, efforts should be developed to eliminate or minimize light scattering or absorption. Therefore the porosity and size of crystals in a ceramic body should be strictly controlled. Typical transparent ceramics are fabricated by pressure-assisted sintering techniques such as hot isostatic pressing (HIP), spark plasma sintering (SPS), and pressure-less sintering (PLS). However, a simple energy efficient production method remains a challenge. In this study, we describe a simple fabrication process via a facile filtration system that can fabricate translucent hydroxyapatite based ceramics. The translucent pieces yielded from filtration exhibit optical transmittance that was confirmed by UV spectroscopy. Briefly, the morphology and size of ceramic nanoparticles, filtration pressure and filtration time are important parameters to be discussed. Compared with different hydroxyapatite nanoparticles, spherical nanoparticles easily form a densely packed structure, followed by sintered ceramics. When the strontium content in HA increases, the morphology of HA changes from nano-spheres to nano-rods, following a decrease in transparency. A pressure filtration model combining Darcy's law and the Kozeny-Carman relation has been discussed to simulate and explain why the translucent ceramics can be fabricated via such a simple process. This method could be further applied to prepare other translucent functional ceramics by controlling the size and morphology of ceramic particles.
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| 6. |
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| 7. |
- Cai, Yixiao, et al.
(författare)
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Strategy towards independent electrical stimulation from cochlear implants : Guided auditory neuron growth on topographically modified nanocrystalline diamond
- 2016
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 31, s. 211-220
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Tidskriftsartikel (refereegranskat)abstract
- Cochlear implants (CI) have been used for several decades to treat patients with profound hearing loss. Nevertheless, results vary between individuals, and fine hearing is generally poor due to the lack of discrete neural stimulation from the individual receptor hair cells. A major problem is the deliverance of independent stimulation signals to individual auditory neurons. Fine hearing requires significantly more stimulation contacts with intimate neuron/electrode interphases from ordered axonal re-growth, something current CI technology cannot provide.Here, we demonstrate the potential application of micro-textured nanocrystalline diamond (NCD) surfaces on CI electrode arrays. Such textured NCD surfaces consist of micrometer-sized nail-head-shaped pillars (size 5 5 lm2) made with sequences of micro/nano-fabrication processes, including sputtering, photolithography and plasma etching.The results show that human and murine inner-ear ganglion neurites and, potentially, neural progenitor cells can attach to patterned NCD surfaces without an extracellular matrix coating. Microscopic methods revealed adhesion and neural growth, specifically along the nail-head-shaped NCD pillars in an ordered manner, rather than in non-textured areas. This pattern was established when the inter-NCD pillar distance varied between 4 and 9 lm.The findings demonstrate that regenerating auditory neurons show a strong affinity to the NCD pillars, and the technique could be used for neural guidance and the creation of new neural networks. Together with the NCD’s unique anti-bacterial and electrical properties, patterned NCD surfaces could provide designed neural/electrode interfaces to create independent electrical stimulation signals in CI electrode arrays for the neural population.
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| 8. |
- Cai, Yixiao, et al.
(författare)
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Utilization of Translucent Hydroxyapatite Nano-Ceramics as a Bio-Window Material
- 2016
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Ingår i: Nano Advances. ; 1, s. 45-49
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Tidskriftsartikel (refereegranskat)abstract
- Bioceramic materials are importantlyused in the field ofhard tissue engineering. The direct detection of cell response is almost impossible for mostof bioceramics due to theiropaqueness. Thus,the live tracking of cell behavior cannot be performedon these ceramics. In this study, we proposea strategy thatdirect observation of cell growth through hydroxyapatite (HA)ceramics can be realized by employing a translucent hydroxyapatite (tHA) nano-ceramic. We obtained MC3T3 preosteoblast cells and cultured them in the presence of tHA for up to 7 days. The results show that MC3T3cells were able to be seen through the tHA. In addition, live fluorescent staining confirmed that the MC3T3 cells were viable throughout the culture time period. The findings reveal the as-fabricated tHA nano-ceramics can bepotentialas a bio-window material for cell adhesion and proliferation.
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