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Kausaite-Minkstimiene A.,Vilnius University | Mazeiko V.,Vilnius University | Ramanaviciene A.,Vilnius University | Ramanaviciene A.,State Research Institute Center for Innovative Medicine | And 2 more authors.
Biosensors and Bioelectronics | Year: 2010

In this article a new method for fabrication of enzymatic electrodes suitable for design of amperometric glucose biosensor and/or anode of biofuel cell powered by glucose is presented. Glucose oxidase (GOx) E.C. 1.1.3.4. from Penicillium vitale was immobilized on the carbon rod electrode by cross-linking it with glutaraldehyde (GOx-electrode). Catalytic activity of immobilized GOx was exploited for polymerisation of aniline by taking a high concentration of hydrogen peroxide produced during the catalytic action of immobilized GOx and locally lowered pH due to the formation of gluconic acid; it created optimal conditions for the polymerisation of aniline. The GOx layer was self-encapsulated within formed polyaniline (PANI) matrix (GOx/PANI-electrode). Properties of the GOx/PANI-electrode have been studied and results were compared with GOx-electrode. The results show that the upper detection limit of glucose using GOx-electrode was dramatically changed by the formation of PANI layer. An increase in the upper detection limit, optimal pH region for operation and stability of GOx based electrode modified by PANI was detected when comparing that of an unmodified GOx-electrode. © 2010 Elsevier B.V. Source


German N.,State Research Institute Center for Innovative Medicine | German N.,Institute of Semiconductor Physics | Ramanavicius A.,Vilnius University | Ramanavicius A.,Institute of Semiconductor Physics | Ramanaviciene A.,Vilnius University
Sensors and Actuators, B: Chemical | Year: 2014

A biosensor based on glucose oxidase (GOx) immobilized on gold nanoparticles (Au-NPs) electrochemically predeposited on the surface of graphite rod (GR) electrode was developed (GOx/Au-NPs/GR). Main analytical characteristics of this biosensor were determined and compared with those determined using a biosensor setup without Au-NP modification (GOx/GR). The highest analytical signal of GOx/Au-NPs/GR electrode was observed after 13 nm Au-NP deposition on the electrode from 0.8 nmol L-1 solution lasting 20 min, when cyclic voltammetry was performed in the range from 0.0 to +1.0 V vs Ag/AgCl. The best analytical characteristics of the developed biosensor were obtained after 25 mg mL-1 GOx immobilization on the Au-NPs/GR electrode. Analytical signal registered using GOx/Au-NPs/GR electrode was 2.08 times higher in comparison to GOx/GR electrode. The registered currents of both electrodes were linearly dependent on glucose concentration in the range of 0.1-10 mmol L-1. The developed GOx/Au-NPs/GR electrode was characterized by high sensitivity, which was equal to 101.02 μA mM -1 cm-2 in the linear glucose detection range. The limit of detection was 0.083 mmol L-1 with relative standard deviation of 6% for GOx/Au-NPs/GR electrode. This study demonstrates a successful practical exploitation of the developed biosensor in a human serum sample. © 2014 Elsevier B.V. Source


Tamulaitiene M.,Vilnius University | Tamulaitiene M.,National Osteoporosis Center | Alekna V.,Vilnius University | Alekna V.,State Research Institute Center for Innovative Medicine
BMC Public Health | Year: 2012

Background: Few epidemiological data on hip fractures were previously available in Lithuania. The aim of this study was to estimate the incidence and hospital costs of hip fractures in Vilnius in 2010. Methods: Data were collected from the medical charts of all patients admitted to hospitals in Vilnius (population, 548,835) due to new low-energy trauma hip fracture, during 2010. The estimated costs included ambulance transportation and continuous hospitalisation immediately after a fracture, which are covered by the Lithuanian healthcare system. Results: The incidence of new low-energy trauma hip fractures was 252 (308 women and 160 men) per 100,000 inhabitants of Vilnius aged 50-years or more. There was an exponential increase in the incidence with increasing age. The overall estimated cost of hip fractures in Vilnius was 1,114,292 EUR for the year 2010. The greatest part of the expenditure was accounted for by fractures in individuals aged 65-years and over. The mean cost per case was 2,526.74 EUR, and cost varied depending on the treatment type. Hip replacement did not affect the overall mean costs of hip fracture. The majority of costs were incurred for acute (53%) and long-term care (35%) hospital stays, while medical rehabilitation accounted for only 12% of the overall cost. The costs of hip fracture were somewhat lower than those found in other European countries. Conclusion: The data on incidence and costs of hip fractures will help to assess the importance of interventions to reduce the number of fractures and associated costs. © 2012 Tamulaitiene and Alekna; licensee BioMed Central Ltd. Source


German N.,State Research Institute Center for Innovative Medicine | Ramanavicius A.,Vilnius University | Ramanavicius A.,Institute of Semiconductor Physics | Voronovic J.,Vilnius University | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

Different glucose biosensors based on glucose oxidase (GOx) immobilised on bare carbon rod electrode (CR) modified with gold nanoparticles (Au-NPs) of (i) 3.5. nm (GOx/3.5Au-NPs/CR), (ii) 6. nm (GOx/6Au-NPs/CR) and (iii) 13. nm (GOx/13Au-NPs/CR) were investigated and compared with biosensors based on GOx immobilised on bare CR (GOx/CR). Enzymatic polymerisation of pyrrole was applied to increase linear detection range of biosensors. The influence of the formed polypyrrole layer on sensitivity and Michaelis-Menten kinetics of designed electrochemical biosensors was investigated. The linear glucose detection interval for GOx/CR and GOx/Au-NPs/CR electrodes was dependent on the duration of polymerisation. © 2012 Elsevier B.V. Source


Oztekin Y.,Vilnius University | Oztekin Y.,Selcuk University | Krikstolaityte V.,Vilnius University | Ramanaviciene A.,Vilnius University | And 3 more authors.
Biosensors and Bioelectronics | Year: 2010

This study is focused on possible application of some 1,10-phenanthroline derivatives (PDs) in the development of biosensors and biofuel cells. Differently from some other studies, the PDs that were not involved into structures of metal complexes were investigated. Five PDs [1,10-phenanthroline monohydrate (PMH); 5-nitro-1,10-phenanthroline (5NP); 5-amino-1,10-phenanthroline (5AP), 5-amino,6-nitro-1,10-phenanthroline (5A6NP) and 5,6-diamino-1,10-phenanthroline (56DAP)] were selected for this study. Bioelectrochemical responses of PDs and glucose oxidase (GOX)-modified graphite rod electrodes (GREs) were studied amperometrically and potentiometrically. The best redox mediators for GOX were found on PDs containing amino groups: 5AP and 56DAP. Amperometrical measurements have shown that 5NP derivative was also acting as a redox mediator but activity of 5NP was approximately four times lower than 5AP and three times lower than 56DAP. This study clearly illustrates that some PDs can be applied as redox mediators for oxidases and are suitable for the development of reagent-less biosensors and biofuel cells. Since amino groups can be very easily involved in the formation of chemical bounds, the amino-PDs are interesting compounds for the development of nanobiotechnological tools by bottom-up technique. © 2010 Elsevier B.V. Source

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