Mojmír Trefulka

Can voltammetry distinguish glycan isomers

The analysis of glycan isomers is an important task in glycomics. This study reveals for the first time that two oligosaccharide pentamers can be distinguished electrochemically. 3α,6α-mannopentaose (MPO) and verbascose (VBS) were modified using Os(VI)-temed and the carbohydrate adducts measured directly in the reaction mixture using cyclic voltammetric (CV) and square wave voltammetric (SWV) stripping at the hanging mercury drop electrode. Some CV and SWV responses of MPO were found to differ from those of VBS at full electrode coverage, requiring µM concentrations at short accumulation time-intervals. Similar results were obtained at partial electrode coverage at nM concentrations. These results afford an opportunity for the development of a new simple and inexpensive glycan analysis.

Subnanomolar Determination of Dopamineby Electrochemical Sensor based on AuNPs-MWCNTs and Mannan-Os (VI) Adducts

Electroactive adducts, comprising 3α,6α–mannan attached to the six-valent osmium complex with N,N,N´,N?-tetramethylenediamine (simply denoted, Man- Os (VI) tmen) was immobilized on the surface of graphite electrodes via a simple adsorption route and then covered with poly(sodium-4 styrene sulfonate) (PSS). Cyclic voltammograms of modified electrodes GE/Man-Os (VI) tmen showed a clear and well-resolved anodic peak for 1 mM of dopamine DA, ascorbate AA, and urate UA at the potential range of -50 to +350 mV vs. Ag|AgCl|(KClsat.) the sensor GE/Man-Os (VI) tmen/PSS was successfully used for sensitive and selective determination of DA in the presence of an excess concentration of AA and UA, 5 mM and 0.5 mM respectively, using differential pulse voltammetry. Under optimized conditions, the peak current densities were linear from 0.1 nM to 20 μM of DA with a sensitivity of 358 μA μΜ-1 and a detection limit LOD (3SD/slope) of 2.8 nM. Further modifying of the sensor using multiwall carbon nanotubes decorated with gold nanoparticles (AuNPs-MWCNTs) led to substantial improvement in its analytical characteristics. The linear response of the electrode modified GE/ AuNPs-MWCNT/Man-Os (VI) tmen to DA was spanned from 1 pM to 40 μM with a high sensitivity of 624.49 μA μΜ-1 and a LOD (3SD/slope) of 0.17 pM.