Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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Author: search.filters.author.Yan, EveliasPublication Index: search.filters.publicationIndex.Scopus

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  • 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.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Colorimetric Assaying of Exosomal Metabolic Biomarkers
    (MDPI, 2023) Yan, Evelias; Goyal, Garima; Yıldız, Ümit Hakan; Boehm, Bernhard O.; Palaniappan, Alagappan
    Exosomes released into the extracellular matrix have been reported to contain metabolic biomarkers of various diseases. These intraluminal vesicles are typically found in blood, urine, saliva, breast milk, cerebrospinal fluid, semen, amniotic fluid, and ascites. Analysis of exosomal content with specific profiles of DNA, microRNA, proteins, and lipids can mirror their cellular origin and physiological state. Therefore, exosomal cargos may reflect the physiological processes at cellular level and can potentially be used as biomarkers. Herein, we report an optical detection method for assaying exosomal biomarkers that supersedes the state-of-the-art time consuming and laborious assays such as ELISA and NTA. The proposed assay monitors the changes in optical properties of poly(3-(4-methyl-3'-thienyloxy) propyltriethylammonium bromide) upon interacting with aptamers/peptide nucleic acids in the presence or absence of target biomarkers. As a proof of concept, this study demonstrates facile assaying of microRNA, DNA, and advanced glycation end products in exosomes isolated from human plasma with detection levels of ~1.2, 0.04, and 0.35 fM/exosome, respectively. Thus, the obtained results illustrate that the proposed methodology is applicable for rapid and facile detection of generic exosomal biomarkers for facilitating diseases diagnosis.
  • Article
    Citation - WoS: 35
    Citation - Scopus: 44
    Current Trends and Challenges in Point-Of Urinalysis of Biomarkers in Trace Amounts
    (Elsevier, 2022) Yeasmin, Sanjida; Ammanath, Gopal; Önder, Ahmet; Yan, Evelias; Yıldız, Ümit Hakan; Palaniappan, Alagappan; Liedberg, Bo
    Urinalysis enables non-invasive point-of-care (POC) testing of numerous biomarkers at their physiological and elevated levels, obviating the need for sophisticated equipment or trained personnel. POC urinalysis is used to identify biomarkers that are rich in urine (greater than 1 μM), such as lactate, uric acid, glucose, ions, and adenosine. Urine also contains biomarkers such as small molecules, nucleic acids, neurotransmitters, and drugs in trace amounts (less than 1 μM). These biomarkers are of significant importance for health care monitoring, diagnosis of various disorders (cancer, metabolic diseases, etc.) and illicit drug control (cocaine, steroids, etc.). While POC detection of urinary biomarkers at higher concentration (μM to mM) levels is feasible, direct assaying of biomarkers in nM to fM levels is challenging, as assay responses are typically masked by interferences from the urine sample matrix. This report is a consolidated review of emerging trends and challenges in the POC urinalysis for detecting biomarkers that are less abundant in urine. The sensing mechanisms, analytical device fabrication, discrete and integrated sample pre-treatment procedures for POC assaying of urinary markers in trace amounts are elaborated. Subsequently, the utilization of smart data analytics for facilitating personalized urinalysis is presented. A comprehensive outlook on associated challenges in POC urinalysis of biomarkers in trace amounts is further provided, which would facilitate the advancement of POC urinalysis for a wide range of healthcare applications.