Search Results (3)

We have fabricated a new highly reproducible, stable, and sensitive cellulose paper-based Surfaced-enhanced Raman scattering (SERS) sensor substrate for non-enzymatic label-free glucose detection. To enhance reproducibility, stability, and sensitivity, the cellulose paper (CP) substrate has been modified with a naturally derived biocompatible polymer, chitosan (CS), followed by depositing enormous amount of plasmonic silver nanoparticles (AgNPs) on CP/CS and finally forming a self-assembling monolayer of 4-mercaptophenyl boronic acid (MPBA) on CP/CS/AgNPs (CP/CS/AgNPs/MPBA). The SERS sensor substrate is characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) spectroscopy techniques. The glucose sensing is achieved by monitoring the SERS intensity of C-S and B-O stretching vibrations at 1072 cm⁻¹ in MPBA, which is gradually increased with increasing concentration of glucose due to the increasing orientation change of MPBA on AgNPs. The results show that the proposed glucose paper-based SERS sensor exhibits a high analytical enhancement factor (AEF) (3.4 × 10⁷), enhanced reproducibility (<7%), improved stability (>5 weeks), excellent selectivity towards other metabolic compounds, and high sensitivity with a limit of detection (LOD) of 0.74 mM and a linear dynamic range between 1.0 and 7.0 mM. The practical application of this SERS sensor is examined in real spiked and non-spiked human blood serum samples for the detection of glucose, and satisfactory recovery results have been obtained, demonstrating the potentiality of the present paper-based SERS sensor for non-enzymatic label-free glucose detection in real biological samples. Full article

Sialic acid (SA) is a well-known component of glycoproteins, which have applications in various functional processes on the cell’s surface. The colorimetric is a simpler and more convenient method for measuring SA due to its low-cost apparatus and visual signal changes. This work focused on the unpredictable interparticle crosslinking aggregation of the functionalized gold nanoparticles (AuNPs) in complex media. We proposed a balance of the Derjaguin–Landau–Verwey–Overbeek (DLVO)-type aggregation and molecule-based interaction method to solve this problem. Here, we report a novel colorimetric assay for the determination of SA using 4-mercaptophenyl boronic acid (4-MPBA) as an analyte’s recognition molecule, and negative charge PEG₄₀₀ was used to repulsive the interparticle crosslinking. The proposed sensing platform shows a linear relationship between the ratio of the absorbance intensity (A₅₂₅/A₆₆₀) and concentration of SA from 0.05 to 8 mM (R² = 0.997) and a detection limit of 48 μM was observed. The novel gold-based colorimetric sensor is easy to fabricate, reproducible in its test performance and has been successfully applied for the detection of SA in biological and healthcare product samples. Full article

The importance of glucose in many biological processes continues to garner increasing research interest in the design and development of efficient biotechnology for the sensitive and selective monitoring of glucose. Here we report on a surface-enhanced Raman scattering (SERS) detection of 4-mercaptophenyl boronic acid (4-MPBA)-immobilized gold-silver core-shell assembled silica nanostructure (SiO₂@Au@Ag@4-MPBA) for quantitative, selective detection of glucose in physiologically relevant concentration. This work confirmed that 4-MPBA converted to 4-mercaptophenol (4-MPhOH) in the presence of H₂O₂. In addition, a calibration curve for H₂O₂ detection of 0.3 µg/mL was successfully detected in the range of 1.0 to 1000 µg/mL. Moreover, the SiO₂@Au@Ag@4-MPBA for glucose detection was developed in the presence of glucose oxidase (GOx) at the optimized condition of 100 µg/mL GOx with 1-h incubation time using 20 µg/mL SiO₂@Au@Ag@4-MPBA and measuring Raman signal at 67 µg/mL SiO₂@Au@Ag. At the optimized condition, the calibration curve in the range of 0.5 to 8.0 mM was successfully developed with an LOD of 0.15 mM. Based on those strategies, the SERS detection of glucose can be achieved in the physiologically relevant concentration range and opened a great promise to develop a SERS-based biosensor for a variety of biomedicine applications. Full article