Browsing by Author "Douman, Samantha F"

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    Aptamer-driven biosensor technology for the quantitative analysis of C-reactive protein
    (John Wiley and Sons Inc, 2025) Oranzie, Marlon; January, Jaymi L; Sanga, Nelia A.; Leve, Zandile D; Mini, Sixolile; Cupido, Candice; Douman, Samantha F; Iwuoha, Emmanuel I.
    C-reactive protein (CRP) is a widely recognized biomarker for early myocardial infarction (MI) detection, released into the bloodstream during heart inflammation. Traditional assays for CRP detection, like ELISA and immunoradiometric assays, are costly, time-consuming, and require large sample volumes. Aptasensors are becoming increasingly popular for MI diagnosis due to their affordability, simplicity, and potential for point-of-care use. In this study, an electrochemical aptasensor incorporating mercaptosuccinic acid-capped nickel selenide quantum dots (MSA-NiSe2 QD) were developed for CRP detection. The amine-modified aptamer was immobilized on the MSA-NiSe2 QD using EDC/NHS coupling chemistry. Chronocoulometric measurements showed high selectivity towards CRP in phosphate buffer, with a linear range of 10–110 pg/mL and a detection limit of 2.80 pg/mL. Cross-reactivity experiments confirmed the aptasensor's high selectivity for CRP. Testing in human serum samples demonstrated recovery rates of 94–100.5 %, indicating its suitability for clinical diagnostics. Validation studies with a commercial CRP ELISA kit showed the aptasensor's superior sensitivity in both physiological buffer and human serum.
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    Electrochemiluminescence at 3D Printed Titanium Electrodes
    (Frontiers Media SA, 2021) Douman, Samantha F; De Eguilaz, Miren Ruiz; Cumba, Loanda R
    The fabrication and electrochemical properties of a 3D printed titanium electrode array are described. The array comprises 25 round cylinders (0.015 cm radius, 0.3 cm high) that are evenly separated on a 0.48 × 0.48 cm square porous base (total geometric area of 1.32 cm2 ). The electrochemically active surface area consists of fused titanium particles and exhibits a large roughness factor ≈17. In acidic, oxygenated solution, the available potential window is from ∼-0.3 to +1.2 V. The voltammetric response of ferrocyanide is quasi-reversible arising from slow heterogeneous electron transfer due to the presence of a native/oxidatively formed oxide. Unlike other metal electrodes, both [Ru(bpy)3] 1+ and [Ru(bpy)3] 3+ can be created in aqueous solutions which enables electrochemiluminescence to be generated by an annihilation mechanism. Depositing a thin gold layer significantly increases the standard heterogeneous electron transfer rate constant, ko , by a factor of ∼80 to a value of 8.0 ± 0.4 × 10−3 cm s−1 and the voltammetry of ferrocyanide becomes reversible. The titanium and gold coated arrays generate electrochemiluminescence using tri-propyl amine as a co-reactant. However, the intensity of the gold-coated array is between 30 (high scan rate) and 100-fold (slow scan rates) higher at the gold coated arrays. Moreover, while the voltammetry of the luminophore is dominated by semi-infinite linear diffusion, the ECL response is significantly influenced by radial diffusion to the individual microcylinders of the array.