Adam Lesniewski

Lysozyme detection on aptamer functionalized graphene-coated SPR interfaces.

The paper reports on a surface plasmon resonance (SPR)-based approach for the sensitive and selective detection of lysozyme. The SPR sensor consists of a 50 nm gold film coated with a thin film of reduced graphene oxide (rGO) functionalized with anti-lysozyme DNA aptamer. The SPR chip coating with rGO matrix was achieved through electrophoretic deposition of graphene oxide (GO) at 150 V. Electrophoretic deposition resulted in partial reduction of GO to rGO with a thickness depending on the deposition time. For very short time pulses of 20 s, the resulting rGO film had a thickness of several nanometers and was appropriate for SPR sensing. The utility of the graphene-based SPR sensor for the selective and sensitive detection of proteins was demonstrated using lysozyme as model protein. Functionalization of rGO matrix with anti-lysozyme DNA aptamer through π-stacking interactions allowed selective SPR detection of lysozyme. The graphene-based SPR biosensor provides a means for the label-free, concentration-dependent and selective detection of lysozymes with a detection limit of 0.5 nM.

Preparation of reduced graphene oxide–Ni(OH)2 composites by electrophoretic deposition: application for non-enzymatic glucose sensing

A sensitive and stable non-enzymatic sensing platform for D-glucose based on a reduced graphene oxide (rGO) matrix modified with Ni(OH)2 nanostructures was established. The sensing matrix was fabricated in one-step through an electrophoretic deposition approach. It is based on the mixing of negatively charged graphene oxide (GO) with nickel ions resulting in a positively charged composite making cathodic electrophoretic deposition possible. The thickness of the resulting rGO/Ni(OH)2 matrix deposited on Au could be controlled by varying the time of electrophoretic deposition. The rGO/Ni(OH)2 matrix was characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and cyclic voltammetry. The rGO/Ni(OH)2 electrodes exhibited excellent electrocatalytic behaviour towards glucose oxidation in alkaline medium. The response current of the sensor is linear to glucose concentrations from 15 μM to 30 mM with a sensitivity of 11.4 ± 0 mA cm−2 mM−1. The interface was much more stable than drop-cast films. These results pave the way for electrophoretic deposition as a competitive alternative over drop-casting for the fabrication of rGO modified interfaces.

Antibody modified gold nanoparticles for fast and selective, colorimetric T7 bacteriophage detection.

Herein, we report a colorimetric immunosensor for T7 bacteriophage based on gold nanoparticles modified with covalently bonded anti-T7 antibodies. The new immunosensor allows for a fast, simple, and selective detection of T7 virus. T7 virions form immunological complexes with the antibody modified gold nanoparticles which causes them to aggregate. The aggregation can be observed with the naked eye as a color change from red to purple, as well as with a UV-vis spectrophotometer. The aggregate formation was confirmed with SEM imaging. Sensor selectivity against the M13 bacteriophage was demonstrated. The limit of detection (LOD) is 1.08 × 10(10) PFU/mL (18 pM) T7. The new method was compared with a traditional plaque test. In contrast to biological tests the colorimetric method allows for detection of all T7 phages, not only those biologically active. This includes phage ghosts and fragments of virions. T7 virus has been chosen as a model organism for adenoviruses. The described method has several advantages over the traditional ones. It is much faster than a standard plaque test. It is more robust since no bacteria-virus interactions are utilized in the detection process. Since antibodies are available for a large variety of pathogenic viruses, the described concept is very flexible and can be adapted to detect many different viruses, not only bacteriophages. Contrary to the classical immunoassays, it is a one-step detection method, and no additional amplification, e.g., enzymatic, is needed to read the result.

Film electrode prepared from oppositely charged silicate submicroparticles and carbon nanoparticles for selective dopamine sensing

Film electrodes prepared from oppositely charged silicate submicroparticles and carbon nanoparticles was applied for selective dopamine sensing. Mesoporous silicate submicroparticles with tetraalkylammonium functionalities were prepared by sol-gel method. They were immobilised on an indium tin oxide film surface together with phenylsulphonated carbon nanoparticles by layer-by-layer method: alternative immersion into their suspensions. As it is shown by scanning electron microscopy the obtained film is composed of silicate submicroparticles covered by carbon nanoparticles. The nanoparticulate film is stable and its electroactive surface is significantly larger than substrate. Accumulation of redox active cations indicates that only fraction charged functionalities of carbon nanoparticles are employed in film formation. The obtained electrode exhibits catalytic properties towards dopamine oxidation and its interferences as ascorbic acid, uric acid and acetaminophen. This allows for selective determination of tenth micromolar concentration of dopamine in the presence of these interferences at milimolar level. The detection limit and linear range were determined to 0.1 × 10⁻⁶ mol dm⁻³ and 0.3-18 × 10⁻⁶ mol dm⁻³ respectively.