Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Department: search.filters.department.Izmir Institute of TechnologyPublisher: search.filters.publisher.Elsevier Science Sa

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 8
    Micro-Arc and Thermal Oxidized Titanium Matrix Composites for Tribocorrosion-Resistant Biomedical Implants
    (Elsevier Science Sa, 2024) Sousa, Luis; Costa, Natalia A.; Rossi, Andre; Simoes, Sonia; Toptan, Fatih; Alves, Alexandra C.
    Superior tribocorrosion resistance is offered by titanium matrix composites (TMCs) compared to their unreinforced matrix metal, but bioactivity concerns are raised for biomedical applications. Simple methods such as micro -arc oxidation (MAO) and thermal oxidation (TO) are employed to enhance the bioactivity and degradation resistance of Ti. However, the impact of those surface treatments on TMC surfaces is poorly understood. Therefore, the present work aimed to explore the influence of MAO and TO treatments on the surfaces of in - situ Ti-TiB-TiC and ex - situ Ti-B 4 C composites, and to assess their corrosion and tribocorrosion performance. Corrosion and tribocorrosion tests were conducted in phosphate-buffered saline solution (PBS) at body temperature. Electrochemical assays were performed by means of potentiodynamic polarization scans while additional potentiostatic tests were performed for the untreated ex - situ composites. Tribo-electrochemical assays were conducted under open circuit potential (OCP) and under normal loads of 0.5 and 10 N against a 10 mm diameter alumina ball in a reciprocating ball -on -plate tribometer. Results revealed reinforcement detachments in ex - situ composites after both treatments. This was primarily attributed to oxide layer growth at the reinforcement/reaction zone interface. Hence, the use of MAO and TO on ex - situ Ti-B 4 C composites may not be appropriate for biomedical applications, mainly because the B 4 C particles tend to detach during the treatment. In contrast, TOtreated in - situ composites displayed excellent combination of corrosion and tribocorrosion performance, even under elevated applied loads, mainly due to the existence of the oxygen diffusion zone (ODZ) beneath the oxide surface produced by TO, together with the more stable electrochemical properties observed during steady -state conditions.
  • Article
    Free-Standing Three-Dimensional Graphene Scaffolds for Protease Functional Assay
    (Elsevier Science Sa, 2024) Ng, Zhi Kai; Yan, Evelias; Goyal, Garima; Gudlur, Sushanth; Kanagavel, Deepankumar; Yildiz, Umit Hakan; Teo, Edwin Hang Tong
    Three-dimensional graphene scaffolds (3d-GS) of high porosity possessing good fluorescence quenching properties are potential candidates for the development of optical biosensors. Herein, we demonstrate the feasibility of utilising intact and free-standing 3d-GS for sensitive detection of proteases, a class of disease diagnosis bio-markers of significant interest. Recombinant OmpT was employed as a model protease for validating the pro-posed methodology. A short (15-residue) peptide sequence encoding a specific recognition site for OmpT was end-labelled with a fluorescent dye (5-FAM) whose fluorescence is quenched when the peptide is anchored to 3d-GS. However, in the presence of OmpT, the peptide is cleaved and released from 3d-GS, resulting in a sig-nificant recovery in fluorescence. The functional assay described herein involves a single step fabrication process of anchoring the peptide to 3d-GS. The integrity of the 3d-GS is hypothesised to overcome the concern of dynamic requenching associated with the typical homogeneous assays based on graphene, yielding a limit of detection (LOD) of similar to 140 nM, which is over an order higher than homogeneous assays performed using the same composition of graphene in powdered form. To the best of our knowledge, this is the first report on utilising free-standing 3d-GS for facile assaying of proteases.