Supramolecular architecture based on the self-assembling of multiwall carbon nanotubes dispersed in polyhistidine and glucose oxidase: Characterization and analytical applications for glucose biosensing

An amperometric biosensor of L-fucose in urine for the first screening test of cancer

Quantitative routine detection of fucose, which is a cancer marker, in urine is effective for the preliminary screening of cancer. Amperometric biosensing methods have the advantage of being simple, rapid, and precise for urinalysis. However, coexisting electroactive interferences such as ascorbic acid (AA), dopamine (DA), and uric acid (UA) prevent accurate measurements. In this work, an amperometric l-fucose biosensor unaffected by interferences was developed and utilizes direct electron transfer type bioelectrocatalysis of pyrroloquinoline quinone (PQQ)-dependent pyranose dehydrogenase from Coprinopsis cinerea (CcPDH). The isolated PQQ domain from CcPDH was immobilized on gold nanoparticle (AuNP)-modified electrodes, which obtained a catalytic current at a lower potential than the oxidation potential of the interfering compounds. Applying an operating potential of -0.1 V vs. Ag|AgCl (3 M NaCl) enabled the detection of l-fucose while completely eliminating the oxidation of AA, DA, and UA on the electrodes. The increase in the specific area of the electrodes by increasing the AuNP drop-casting time resulted in an improvement in the sensor performance. The biosensor exhibited a linear range for l-fucose detection between 0.1 mM and 1 mM (R² = 0.9996), including a cut-off value, the sensitivity was 3.12 ± 0.05 μA mM^-1 cm^-2, and the detection limit was 13.6 μM at a signal-to-noise ratio of three. The biosensor can be used to quantify the concentration of l-fucose at physiological levels and does not require urine preprocessing, making it applicable to practical use for point-of-care testing with urine.

Effect of gold nanoparticles on the structure and electron-transfer characteristics of glucose oxidase redox polyelectrolyte-surfactant complexes

Efficient electrical communication between redox proteins and electrodes is a critical issue in the operation and development of amperometric biosensors. The present study explores the advantages of a nanostructured redox-active polyelectrolyte-surfactant complex containing [Os(bpy)2Clpy](2+) (bpy=2,2'-bipyridine, py= pyridine) as the redox centers and gold nanoparticles (AuNPs) as nanodomains for boosting the electron-transfer propagation throughout the assembled film in the presence of glucose oxidase (GOx). Film structure was characterized by grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM), GOx incorporation was followed by surface plasmon resonance (SPR) and quartz-crystal microbalance with dissipation (QCM-D), whereas Raman spectroelectrochemistry and electrochemical studies confirmed the ability of the entrapped gold nanoparticles to enhance the electron-transfer processes between the enzyme and the electrode surface. Our results show that nanocomposite films exhibit five-fold increase in current response to glucose compared with analogous supramolecular AuNP-free films. The introduction of colloidal gold promotes drastic mesostructural changes in the film, which in turn leads to a rigid, amorphous interfacial architecture where nanoparticles, redox centers, and GOx remain in close proximity, thus improving the electron-transfer process.