Biomedical subjects

Arunas Ramanavicius

Publications and source records attributed to Arunas Ramanavicius.

7 recordsLinked to original sources

PubMed2006

AFM study of conducting polymer polypyrrole nanoparticles formed by redox enzyme - glucose oxidase - initiated polymerisation.

Redox enzyme - glucose oxidase E.C. 1.1.3.4 from Penecillum vitale (GOx) - initiated polypyrrole (Ppy) synthesis was applied for the formation of polypyrrole based nanoparticles. The increase in optical absorbance at lambda=460 nm was exploited for the monitoring of polypyrrole polymerisation process. The shape and size of the formed Ppy nanoparticles was also monitored by means of contact mode AFM. The highest increase in the diameter of the formed Ppy nanoparticles was detected during 15-day period. AFM imaging was performed in contact mode to investigate the shape and flexibility of particles deposited on the SiO2 and Pt surfaces. Contact mode AFM investigations allowed us to conclude that after drying at 50 degrees C the formed Ppy particles are more flexibly deposited on the Pt electrode if compared to those deposited on the SiO2 substrate. The application of well-shaped Ppy nanoparticles in biomedicine, chromatography and bioanalysis may be predicted.

Electric Conductivity↗

PubMed2005

Biofuel cell based on direct bioelectrocatalysis.

A biofuel cell, consisting of two 3mm diameter carbon rod electrodes and operating at ambient temperature in aqueous solution, pH 6, is described. Biofuel cell based on enzymes able to exchange directly electrons with carbon electrodes was constructed and characterized. Anode of the biofuel cell was based on immobilized Quino-hemoprotein alcohol dehydrogenase from Gluconobacter sp. 33 (QH-ADH), cathode on co-immobilized glucose oxidase from Aspergilus niger (GO(x)) and microperoxidase 8 from the horse heart (MP-8) acting in the consecutive mode. Two enzymes GO(x) and MP-8 applied in the design of biofuel cell cathode were acting in consecutive mode and by hydrogen peroxide oxidized MP-8 was directly accepting electrons from carbon rod electrode. If ethanol was applied as an energy source the maximal open circuit potential of the biofuel cell was -125 mV. If glucose was applied as energy source the open circuit potential of the cell was +145 mV. The maximal open circuit potential (270 mV) was achieved in the presence of extent concentration (over 2 mM) of both substrates (ethanol and glucose). Operational half-life period (tau(1/2)) of the biofuel cell was found to be 2.5 days.

Alcohol Dehydrogenase↗

PubMed2004

Wiring of PQQ-dehydrogenases.

The performance of pyrroloquinoline quinone (PQQ) dependent alcohol dehydrogenase (ADH) and two types of PQQ-glucose dehydrogenases in solution and when immobilized on the carbon paste electrodes modified with ferrocene derivatives is investigated. The immobilization of ADH consisting of PQQ and four hemes improves its stability up to 10 times. Both PQQ and heme moieties are involved in the electron transport from substrate to electrode. The ferrocene derivatives improve the electron transport 10-fold. Membrane-bound alcohol dehydrogenase from Gluconobacter sp. 33, intracellular soluble glucose dehydrogenase from Acinetobacter calcoaceticus L.M.D. 79.41 (s-GDH), and the membrane-bound enzyme (m-GDH) from Erwinia sp. 34-1 were purified and investigated. Soluble and membrane-bound PQQ-glucose dehydrogenases display different behavior during the immobilization on the modified carbon electrodes. The immobilization of s-GDH leads to a decrease in both stability and substrate specificity of the enzyme. This suggests that PQQ dissociates from the enzyme active center and operates as a free-diffusing mediator. The rate-limiting step of the process is likely the loading of PQQ onto the apo-enzyme. The immobilization of m-GDH leads to its substantial stabilization and improves the substrate specificity. The nature of m-GDH binding to the electrode surface is presumably similar to the binding to the cell membrane through its anchor-subunit. The enzyme operates as an enzyme and mediator complex.

Adsorption↗

PubMed2004

Molecularly imprinted polypyrrole-based synthetic receptor for direct detection of bovine leukemia virus glycoproteins.

Preparation and basic characterization of polypyrrole-based molecularly imprinted polymer (MIP) for label-free detection of bovine leukemia virus (BLV) glycoprotein gp51 (gp51) is firstly described. Polypyrrole (Ppy) was selected as a matrix for preparation of MIP. Polypyrrole doped by gp51 (gp51/Ppy) was prepared by electrochemical deposition of this polymer on the surface of platinum-black electrode. Then, molecules of gp51 were removed from polymeric backbone and molecularly imprinted polypyrrole (mPpy) was ready for recognition of gp51 in the aqueous solution. Pulsed amperometric detection (PAD) was applied for label-free detection of gp51 in the samples. Anti-gp51 antibodies and secondary antibodies labeled with horseradish peroxidase (HRP) were involved as markers for the control of mPpy preparation procedures. Control experiments were also simultaneously performed by spectrophotometrical detection of HRP activity. Application of anti-gp51 and HRP labelled secondary antibodies confirmed that generation of analytical signal was based on redoping of mPpy by gp51. During our experiments, only few mPpy redoping/dedoping cycles were effective, but generally this method seems to be very effective for the future development of mPpy-based MIPs. Preparation, electrochemical investigation and control procedures are described in the current paper.

Biomimetic Materials↗

PubMed2004

Pulsed amperometric detection of DNA with an ssDNA/polypyrrole-modified electrode.

Pulsed amperometric detection (PAD) of target DNA with platinum electrodes modified by single-stranded DNA (ssDNA) entrapped within polypyrrole (ssDNA/Ppy) is reported for the first time. Single-stranded DNA 20-mers complementary to the target DNA were used to construct the DNA biosensors. Polymerase chain reaction (PCR) amplified bovine leukaemia virus (BLV) provirus DNA was used as target DNA. Electrochemical impedance spectroscopic (EIS) investigation of ssDNA/Ppy before and after incubation in target DNA-containing sample revealed significant changes in terms of an imaginary (Z") vs. a real (Z') component. The PAD results were in good agreement with EIS investigations. The PAD method was selected, because it does not require such sophisticated equipment as it is used to perform EIS and the results obtained can be more easily estimated. Optimum conditions for performing PAD and evaluating an analytical signal were elaborated. No label-binding step was necessary for detection of target DNA in PCR-amplified amplicons and detection time was reduced by as much as 30-35 min. The changes of PAD signals were at least 6-7 times higher if ssDNA/Ppy-modified electrodes instead of blank Ppy-modified electrodes were incubated in the target DNA solutions. If ssDNA/Ppy modified electrodes were incubated in non-complementary (control) DNA solution changes in PAD signals were smaller than those detected after incubation in complementary (target) DNA-containing solution by a factor of at least 6-8.

Animals↗

PubMed2004

Chronic caffeine intake affects lysozyme activity and immune cells in mice.

The aim of this study was to examine the effect of caffeine on the activity of lysozyme and some immune parameters of mice. The mice were divided into five groups. Group 1, the control group, was given water. The other four groups were administered various concentrations of caffeine by oral intubation (group 2, 2 mg x kg(-1); group 3, 20 mg x kg(-1); group 4, 40 mg x kg(-1); group 5, 200 mg x kg(-1)). It was found that the activity of lysozyme in the serum depended on the caffeine dose. Compared with the control (group 1), lysozyme activity was 1.4-times higher in group 2, 1.6-times higher in the group 3, and 1.8-times higher in groups 4 and 5 (P < 0.05). In group 3 a significant increase in spleen weight was detected and the spleen index was 2.1-times (P < 0.05) higher compared with control. In group 3 the number of monocytes and neutrophils was 2.5-times higher (P < 0.05) compared with control. In group 5 the caffeine increased the number of neutrophils 2.7-times and increased the number of eosinophils 4.6-times (P < 0.05) compared with control. Our study revealed that caffeine played an important role in the development of protective immune response.

Animals↗

PubMed2002

Bioelectrochemical application of some PQQ-dependent enzymes.

This paper focuses on the use of PQQ-dependent enzymes (PQQ enzymes) in amperometrical biosensors and gives emphasis on their innovative designs and applications. The study covers some aspects in the evolution of biosensors based on PQQ enzymes. Main attention is focused on the electrochemical properties of PQQ enzymes as very promising materials for the formation of electrochemical biosensors. Immobilization approaches and redox mediators recently used in PQQ enzymes based biosensors are reviewed. The acceptance of polypyrrole as a very promising immobilization matrix for some PQQ enzymes is discussed.

Alcohol Dehydrogenase↗