Da Eun Oh

Nitrofurantoin (NFT) is a widely used antibiotic that requires sensitive and reliable detection due to its potential environmental and health impacts. In this study, a poly(O-cresolphthalein complexone)/electrochemically reduced graphene oxide (POC/ERGO) nanocomposite was electrochemically fabricated via one-step process and applied to a modified GCE for the electrochemical detection of nitrofurantoin. The sensing performance of the POC/ERGO-GCE was evaluated using CV and DPV. The developed sensor exhibited a wide linear detection range from 1 to 500 μM, and a low detection limit of 78.90 nM as determined by DPV. In addition, it demonstrated excellent anti-interference capability, good reproducibility and selectivity toward NFT, confirming the reliability of the proposed sensing platform. The enhanced performance is attributed to the increased electrochemically active surface area and improved electron transfer properties of the POC/ERGO-GCE. These results indicate that the proposed platform provides a reliable approach for the electrochemical detection of nitrofurantoin and offers a promising foundation for the development of antibiotic sensing systems.

Plasmonic photothermal PCR is a nucleic acid amplification technique that utilizes the localized surface plasmon resonance effect of plasmonic nanomaterials under the irradiation of light with specific wavelengths to achieve rapid thermal cycling. PPT-PCR is considered as a next-generation PCR technique due to the potential to be applied to the development of point-of-care diagnostics and the fast, sensitive and accurate detection performance. In this study, we present a integrated molecular diagnostic platform that combines PPT-PCR with a carbon nanotube-based field-effect transition sensor for fast and sensitive quantification of DNA target. The swCNT-FET sensor exhibits excellent sensitivity, capable of detecting low concentrations of target nucleic acids within minutes after PPT-PCR amplification. Besides, to improve the specificity of the assay, we introduce a hairpin structured primer to generate amplicons with an external single-strand tail that can hybridize with probes modified on the swCNT-FET sensor. With this design, a limitation of detection of 1.5 aM achieved within 20min.

In this work, a glassy carbon electrode (GCE) modified with reduced graphene oxide and β-cyclodextrin (rGO/β-CD) nanocomposite was developed for the electrochemical detection of nitrofurantoin (NFT). The structural and morphological characteristics of the synthesized nanocomposite were determined using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Moreover, the electrochemical behavior of the modified electrodes was thoroughly examined using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), with the rGO/β-CD-modified glassy carbon electrode (GCE) demonstrating superior electron transfer capability. Key experimental parameters, including scan rate, material loading, and solution pH, were systematically optimized. After optimizing the experimental conditions, the modified sensor showed excellent electrocatalytic performance and selectivity toward NFT, achieving a broad linear detection range from 0.5 to 120 μM, a low limit of detection (LOD) of 0.048 μM, and a high sensitivity of 12.1 µA µM^–1 cm^–2 using differential pulse voltammetry (DPV). Furthermore, the fabricated electrode exhibited good anti-interference ability, stability, precision, and real-time applicability for NFT detection in a wastewater sample. These results highlight the potential of the rGO/β-CD nanocomposite as a high-performance platform for electrochemical sensing applications.

Graphene, known for its outstanding physical and chemical properties, is widely used in various fields, including electronics and biomedicine. Reduced graphene oxide (rGO) is preferred for electrochemical applications due to its enhanced water solubility and dispersion. Electrochemically reduced graphene oxide (ErGO) is particularly advantageous as it can be prepared under mild conditions and simplifies sensor fabrication; however, ErGO-based electrochemical sensors often lack specificity. Bioreceptors like proteins, enzymes, and DNA/RNA aptamers are incorporated to provide high specificity. This study introduces a guanine (G)/cytosine (C)-modified ErGO electrode (G/C@ErGO-GCE) for the sensitive electrochemical detection of doxorubicin (DOX) with good selectivity. The G/C mixture acts as a bioreceptor and is anchored on the ErGO-GCE surface via π-π interactions. The G/C@ErGO-GCE was characterized using scanning electron microscopy, contact angle measurement, Raman spectroscopy, and electrochemical methods. The sensor demonstrated excellent dynamic range (DPV: 10 nM to 1 µM, CA: 30 nM to 1.3 µM), sensitivity (DPV: 2.17 µA/µM, CA: 6.79 µA/µM), limit of detection (DPV: 84 nM, CA: 34 nM), and selectivity for DOX detection, highlighting its potential for biomedical applications and pharmacokinetic studies.

An electrochemically reduced graphene oxide (ERGO) electrode-based electrochemical assay was developed for rapid, sensitive, and straightforward analysis of both activity and inhibition of the endonuclease EcoRV. The procedure uses a DNA substrate designed for EcoRV, featuring a double-stranded DNA (dsDNA) region labeled with methylene blue (MB) and a single-stranded DNA (ssDNA) region immobilized on the ERGO surface. The ERGO electrode, immobilized with the DNA substrate, was subsequently exposed to a sample containing EcoRV. Upon enzymatic hydrolysis, the cleaved dsDNA fragments were detached from the ERGO surface, leading to a decrease in the MB concentration near the electrode. This diminished the electron transfer efficiency for MB reduction, resulting in a decreased reduction current. This assay demonstrates excellent specificity and high sensitivity, with a limit of detection (LOD) of 9.5 × 10⁻³ U mL⁻¹. Importantly, it can also measure EcoRV activity in the presence of aurintricarboxylic acid, a known inhibitor, highlighting its potential for drug discovery and clinical diagnostic applications.

We present a novel approach that integrates electrical measurements with molecular dynamics (MD) simulations to assess the activity of type-II restriction endonucleases, specifically EcoRV. Our approach employs a single-walled carbon nanotube field-effect transistor (swCNT-FET) functionalized with the EcoRV substrate DNA, enabling the detection of enzymatic cleavage events. Notably, we leveraged the methylene blue (MB) tag as an "orientation guide" to immobilize the EcoRV substrate DNA in a specific direction, thereby enhancing the proximity of the DNA cleavage reaction to the swCNT surface and consequently improving the sensitivity in EcoRV detection. We conducted computational modeling to compare the conformations and electrostatic potential (ESP) of MB-tagged DNA with its MB-free counterpart, providing strong support for our electrical measurements. Both conformational and ESP simulations exhibited robust agreement with our experimental data. The inhibitory efficacy of the EcoRV inhibitor aurintricarboxylic acid (ATA) was also evaluated, and the selectivity of the sensing device was examined.

We developed a transparent and flexible electrochemical sensor using a platform based on a network of single-walled carbon nanotubes (SWCNTs) for the non-enzymatic detection of hydrogen peroxide (H₂O₂) released from living cells. We decorated the SWCNT network on a poly(ethylene terephthalate) (PET) substrate with platinum nanoparticles (PtNPs) using a potentiodynamic method. The PtNP/SWCNT/PET sensor synergized the advantages of a flexible PET substrate, a conducting SWCNT network, and a catalytic PtNP and demonstrated good biocompatibility and flexibility, enabling cell adhesion. The PtNP/SWCNT/PET-based sensor demonstrated enhanced electrocatalytic activity towards H₂O₂, as well as excellent selectivity, stability, and reproducibility. The sensor exhibited a wide dynamic range of 500 nM to 1 M, with a low detection limit of 228 nM. Furthermore, the PtNP/SWCNT/PET sensor remained operationally stable, even after bending at various angles (15°, 30°, 60°, and 90°), with no noticeable loss of current signal. These outstanding characteristics enabled the PtNP/SWCNT/PET sensor to be practically applied for the direct culture of HeLa cells and the real-time monitoring of H₂O₂ release by the HeLa cells under drug stimulation.

We developed a transparent and flexible electrochemical sensor using a platform based on a network of single-walled carbon nanotubes (SWCNTs) for the non-enzymatic detection of hydrogen peroxide (H2O2) released from living cells. We decorated the SWCNT network on a poly(ethylene terephthalate) (PET) substrate with platinum nanoparticles (PtNPs) using a potentiodynamic method. The PtNP/SWCNT/PET sensor synergized the advantages of a flexible PET substrate, a conducting SWCNT network, and a catalytic PtNP, and demonstrated good biocompatibility and flexibility, enabling cell adhesion. The PtNP/SWCNT/PET-based sensor demonstrated enhanced electrocatalytic activity towards H2O2 as well as excellent selectivity, stability, and reproducibility. The sensor exhibited a wide dynamic range of 500 nM to 1 M, with a low detection limit of 228 nM. In addition, Furthermore, the PtNP/SWCNT/PET sensor remained operationally stable even after bending at various angles (15°, 30°, 60°, and 90°) with no noticeable loss of current signal. These outstanding characteristics enabled the PtNP/SWCNT/PET sensor to be practically applied for the direct culture of HeLa cells and the real-time monitoring of H2O2 release by the HeLa cells under drug stimulation.

We developed an electrochemical sensing tool based on the electropolymerization of L-threonine (Thr) followed by the deposition of graphene oxide (GO) and multi-walled carbon nanotube (MWCNT) on the glassy carbon electrode (GCE). The surface morphological study of the proposed electrodes confirmed the formation of composites consisting of poly(Thr), MWCNT, and GO on the GCE by FE-SEM and the structural characterization of the MWCNT/GO composite was confirmed by Raman and ATR-IR analysis. The prepared electrode (MWCNT/GO/Poly(Thr)/GCE) showed high catalytic activity for paracetamol (PCT) determination in comparison with bare GCE, Poly(Thr)/GCE, and MWCNT/GO/GCE. The proposed sensor showed an excellent linear response of MWCNT/GO/Poly(Thr)/GCE toward PCT with a detection limit of 0.16 µM by differential pulse voltammetry. In the presence of norepinephrine (NEP) and folic acid (FA), the voltammetric signal of PCT was not significantly disturbed, revealing the good selectivity of the proposed sensor. Moreover, the designed sensor displayed sufficient repeatability, satisfactory reproducibility, and acceptable stability. Finally, the proposed sensor has been successfully applied for the determination of PCT in tablet formulation and human serum samples.