Krzysztof Stolarczyk

Hybrid biobattery based on arylated carbon nanotubes and laccase.

Single-walled carbon nanotubes (SWCNT) were covalently modified with anthracene and anthraquinone and used for the construction of cathodes for biocatalytic reduction of dioxygen. The nanotubes with aromatic groups casted onto the electrode increased the working surface of the electrode and enabled efficient direct electron transfer (DET) between the enzyme and the electrode. The aryl groups enter the hydrophobic pocket of the T1 center of laccase responsible for exchanging electrons with the substrate. Glassy carbon electrode covered with arylated SWCNT and coated with a layer of neutralized Nafion containing laccase was found to be a very efficient cathode in the hybrid battery. Zn wire covered with a Nafion film served as the anode. The cell parameters were determined: power density was 2 mW/cm(2) and the open circuit potential was 1.5 V.

Biosupercapacitors for powering oxygen sensing devices

A biofuel cell comprising electrodes based on supercapacitive materials - carbon nanotubes and nanocellulose/polypyrrole composite was utilized to power an oxygen biosensor. Laccase Trametes versicolor, immobilized on naphthylated multi walled carbon nanotubes, and fructose dehydrogenase, adsorbed on a porous polypyrrole matrix, were used as the cathode and anode bioelectrocatalysts, respectively. The nanomaterials employed as the supports for the enzymes increased the surface area of the electrodes and provide direct contact with the active sites of the enzymes. The anode modified with the conducting polymer layer exhibited significant pseudocapacitive properties providing superior performance also in the high energy mode, e.g., when switching on/off the powered device. Three air-fructose biofuel cells connected in a series converted chemical energy into electrical giving 2 mW power and open circuit potential of 2V. The biofuel cell system was tested under various externally applied resistances and used as a powering unit for a laboratory designed two-electrode minipotentiostat and a laccase based sensor for oxygen sensing. Best results in terms of long time measurement of oxygen levels were obtained in the pulse mode -45 s for measurement and 15 min for self-recharging of the powering unit.

The dual role of self-assembled monolayers of a tetraazamacrocyclic copper(II) complex in ascorbate oxidation catalysis

Abstract The copper(II) complex with 1,4,8-trimethyl-11-(2-thioethyl)-1,4,8,11-tetraazacyclotetradecane was adsorbed on the surface of glassy carbon (GCE) and gold electrodes using the self-assembly method. More stable coverage of the electrode was obtained using a gold substrate when the complex is anchored to the electrode through its thioethyl substituent. The amount of the complex on the electrode surface based on the charge of the Cu 2+ /Cu + peak points to the nearly monolayer coverage of the electrode surface. The catalytic effect of the monolayer towards ascorbic acid oxidation was observed in neutral and alkaline solutions, and ascribed to the electrostatic interaction of ascorbate anion with the positively charged copper complex bound to the electrode surface. In dioxygenated solutions, the copper complex adsorbed on the electrode catalyses both the electrooxidation and auto-oxidation of ascorbate. The copper-catalyzed autoxidation of ascorbic acid leads to a decrease of the ascorbate electrooxidation peak with time. The progress of this reaction was monitored based on the changes of the electrooxidation current. Copper catalyzed autoxidation of ascorbate is known to require turnover between Cu 2+ and Cu + ions. This indicates that the molecules of the copper complex anchored through the thiol groups to the gold electrode, and tightly packed on the surface play a dual role in the ascorbate oxidation process. The role of the monolayer in enhancing the autoxidation of ascorbic acid resembles the function of copper in some biological complexes catalyzing in vivo ascorbate oxidation.

Reticulated vitreous carbon as a scaffold for enzymatic fuel cell designing

Three - dimensional (3D) electrodes are successfully used to overcome the limitations of the low space - time yield and low normalized space velocity obtained in electrochemical processes with two - dimensional electrodes. In this study, we developed a three - dimensional reticulated vitreous carbon - gold (RVC-Au) sponge as a scaffold for enzymatic fuel cells (EFC). The structure of gold and the real electrode surface area can be controlled by the parameters of metal electrodeposition. In particular, a 3D RVC-Au sponge provides a large accessible surface area for immobilization of enzyme and electron mediators, moreover, effective mass diffusion can also take place through the uniform macro - porous scaffold. To efficiently bind the enzyme to the electrode and enhance electron transfer parameters the gold surface was modified with ultrasmall gold nanoparticles stabilized with glutathione. These quantum sized nanoparticles exhibit specific electronic properties and also expand the working surface of the electrode. Significantly, at the steady state of power generation, the EFC device with RVC-Au electrodes provided high volumetric power density of 1.18±0.14mWcm-3 (41.3±3.8µWcm-2) calculated based on the volume of electrode material with OCV 0.741±0.021V. These new 3D RVC-Au electrodes showed great promise for improving the power generation of EFC devices.

Synthesis and characterization of genistein conjugated with gold nanoparticles and the study of their cytotoxic properties

&NA; Gold nanoparticles conjugated with drug substances are used in diagnostics and therapies. Apart from the combinations involving gold nanoparticles conjugated with drug substances through linkers, a direct bonding is also known. In our paper the example of such a direct bonding between gold nanoparticles and genistein (AuNPs‐GE) is presented. This conjugate was obtained in a one‐pot synthesis and the formation of AuNPs‐GE was monitored in terms of color change and UV‐Vis spectroscopy. It has been shown that genistein reduces Au3+ ions to spherical Au0 nanocrystallites and acts as a stabilizing agent. The efficiency of the purification of the conjugate from free genistein was controlled by the capillary electrophoresis. Gold nanoparticles are homogeneously shaped and have a narrow range of size from 14 to 33 nm and the size of the nanoparticles modified with genistein is around 64.64 ± 0.41 nm, as measured by the TEM and DSL techniques, respectively. The zeta potential of the gold nanoparticles modified with genistein is −19.32 ± 0.82 mV and suggests a high stability of the nanoparticles and lower toxicity for the normal cells. The identity of genistein on the gold nanoparticles was proved by the electrochemistry, NMR and Raman spectroscopy. The mechanism of the conjugate forming has been proposed. The coverage of gold nanoparticles with genistein 5.09% (m/m) has been calculated from the TGA analysis. Moreover, it has been proved that the obtained conjugate is characterized by a high cytotoxic activity towards cancer cells, as observed in the cell line test. Graphical abstract Figure. No caption available.

Functionalization of Electrode Surfaces with Monolayers of Azocompounds and Gold Clusters

Properties of monolayers of azocrown compound self-assembled on gold substrates were studied using voltammetry and scanning tunneling microscopy. The surface concentrations of this compound in monolayers were determined from the area of the voltammetric reduction peaks. The area per one molecule estimated from voltammetry experiments is 0.65 nm2. This value was comparable with the limiting molecular area of the compound in the Langmuir–Blodgett film at the air–water interface. We also observed the presence of gold clusters and other gold structures by STM when a gold electrode modified with azocrown compound was dipped into the tetrachloroaurate solution. Even better spectra of clusters were obtained following one voltammetric scan in the range 0.5 to −0.6 V. After more cycles or if we condition the electrode at 0.4 V the clusters aggregate into wires.

CE method for the in-process control of the synthesis of active substances conjugated with gold nanoparticles

&NA; A fast capillary electrophoresis method was developed and validated for the in‐process control (IPC) of the synthesis of active substances (APIs) with gold nanoparticles (AuNPs). The capillary electrophoresis method was key to ensure that the reaction step conducted in order to obtain AuNP and API conjugates will produce the expected product without the presence of free APIs, which is a critical parameter determining the quality of the synthetic material. Capillary electrophoresis was performed using uncoated fused‐silica capillaries with the effective length of 40 cm, 50 &mgr;m i.d. and the background electrolyte consisted of 20 mM borate buffer (pH 8.5) with the application of hydrodynamic injection 50 mbar/5s, voltage 20 kV, temperature of the capillary cassette 25 °C and UV detection at 261 nm for GE, 541 nm for AuNP‐GE, 227 nm for PE and 535 nm for AuNP‐PE. During validation the specificity, linearity, accuracy, precision, range, and stability of the sample solution were confirmed. The linear regression (R2 = 0.999) between the corrected peak areas of the analytes and their amount was fulfilled in the range from 2.4 &mgr;g/mL to 0.3 mg/mL for genistein and from 4.6 &mgr;g/mL to 0.6 mg/mL for pemetrexed. Within this range the method was proved to be accurate (99.0% for genistein and 99.9% for pemetrexed) and precise for both analytes with the intra‐day RSD values of 0.77% and 0.97% for the migration time of genistein and pemetrexed, respectively. The inter‐day RSD values were 1.90% and 2.27% for the migration time of genistein and pemetrexed, respectively. The LOD and LOQ values for pemetrexed were 1.4 &mgr;g/mL and 4.6 &mgr;g/mL, respectively, and for genistein 0.72 &mgr;g/mL and 2.4 &mgr;g/mL, respectively. The results obtained during the validation indicate that the method is sufficient to be applied for the IPC of the synthesis of APIs with gold nanoparticles. Graphical abstract A universal and fast capillary electrophoresis method was developed and validated for the in‐process control (IPC) of active substances (APIs) synthesis with nanogold particles (AuNPs), as a key to ensure that a reaction step conducted by in order to obtain AuNPs and API conjugates will produce an expected product. During the validation the specificity, linearity, accuracy, precision, range, and stability of the sample solution were confirmed. The results obtained during the validation indicate that the method is sufficient to apply for the IPC of APIs synthesis with nanogold particles. Figure. No caption available. HighlightsIn‐process control (IPC) of active substances (APIs) synthesis with nanogold particles.(AuNPs) using CE method.The developed method fulfilled all validation acceptance criteria.New application of CE method in the pharmaceutical nanotechnology.

Design and Molecular Modeling of Abiraterone-Functionalized Gold Nanoparticles

The aim of our work was the synthesis and physicochemical characterization of a unique conjugate consisting of gold nanoparticles (AuNPs) and a pharmacologically active anticancer substance abiraterone (AB). The direct coupling of AB with gold constitutes an essential feature of the unique AuNPs–AB conjugate that creates a promising platform for applications in nanomedicine. In this work, we present a multidisciplinary, basic study of the obtained AuNPs–AB conjugate. Theoretical modeling based on the density functional theory (DFT) predicted that the Aun clusters would interact with abiraterone preferably at the N-side. A sharp, intense band at 1028 cm−1 was observed in the Raman spectra of the nanoparticles. The shift of this band in comparison to AB itself agrees well with the theoretical model. AB in the nanoparticles was identified by means of electrochemistry and NMR spectroscopy. The sizes of the Au crystallites measured by XRPD were about 9 and 17 nm for the nanoparticles obtained in pH 7.4 and 3.6, respectively. The size of the particles as measured by TEM was 24 and 30 nm for the nanoparticles obtained in pH 7.4 and pH 3.6, respectively. The DLS measurements revealed stable, negatively charged nanoparticles.