Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Maria Tsivou is active.

Publication


Featured researches published by Maria Tsivou.


Analytical Biochemistry | 2009

Stabilization of human urine doping control samples.

Maria Tsivou; D. Livadara; Dimitrios G. Georgakopoulos; Michael A. Koupparis; Julia Atta-Politou; Costas Georgakopoulos

Sport urine samples collected worldwide are not always shipped refrigerated from the collection sites to the World Anti-Doping Agency (WADA) Accredited Laboratories, especially when multiple days of transport are required [1,2]. Commensal urethral flora, urinary pathogens, and species of the environment may contaminate urine specimens [1,3–8] because sample collection procedures are not carried out under sterile conditions. As a result, enzymatic activities produced by microbial contamination may cause changes to the natural androgenic steroid profiles [1,4–10], nicking of human chorionic gonadotropin (hCG) molecule, and subsequent dissociation of gonadotropins [11–15] as well as shifting of erythropoietin (EPO) electrophoretic bands [16–18]. Also, during the past couple of years, antidoping science has been concerned about proteolytic enzymes, or alias proteases, added on purpose to distort the analysis results by degrading EPO [19–22]. The occurrence of degraded urine samples varies over the course of the year, with a peak during summer depending on the country where the specimens are collected as well as the duration of transportation [6,23,24]. If delays are unavoidable and refrigeration of samples is not possible, an effective method of preserving urine specimen is desirable. Up to the current time, no stabilization method has been applied in the urine collection material [2,3,6,20]. The purpose of this


Analytical Biochemistry | 2009

Stabilization of human urine doping control samples: II. microbial degradation of steroids.

Maria Tsivou; D. Livadara; Dimitrios G. Georgakopoulos; Michael A. Koupparis; Julia Atta-Politou; Costas Georgakopoulos

The transportation of urine samples, collected for doping control analysis, does not always meet ideal conditions of storage and prompt delivery to the World Anti-Doping Agency (WADA) accredited laboratories. Because sample collection is not conducted under sterile conditions, microbial activity may cause changes to the endogenous steroid profiles of samples. In the current work, funded by WADA, a chemical mixture consisting of antibiotics, antimycotic substances and protease inhibitors was applied in urine aliquots fortified with conjugated and deuterated steroids and inoculated with nine representative microorganisms. Aliquots with and without the chemical mixture were incubated at 37 degrees C for 7 days to simulate the transportation period, whereas another series of aliquots was stored at -20 degrees C as reference. Microbial growth was assessed immediately after inoculation and at the end of the incubation period. Variations in pH and specific gravity values were recorded. Gas chromatography-mass spectrometry (GC-MS) analysis was performed for the detection of steroids in the free, glucuronide, and sulfate fractions. The addition of the chemical stabilization mixture to urine samples inhibited microorganism growth and prevented steroid degradation at 37 degrees C. On the other hand, four of the nine microorganisms induced alterations in the steroid profile of the unstabilized samples incubated at 37 degrees C.


Analytical and Bioanalytical Chemistry | 2011

Stabilization of human urine doping control samples: a current opinion

Maria Tsivou; Dimitrios G. Georgakopoulos; Helen Dimopoulou; Michael Α. Koupparis; Julia Atta-Politou; Costas Georgakopoulos

Transportation of doping control urine samples from the collection sites to the World Anti-doping Agency (WADA) Accredited Laboratories is conducted under ambient temperatures. When sample delivery is not immediate, microbial contamination of urine, especially in summer, is a common phenomenon that may affect sample integrity and may result in misinterpretation of analytical data. Furthermore, the possibility of intentional contamination of sports samples during collection with proteolytic enzymes, masking the abuse of prohibited proteins such as erythropoietin (EPO) and peptide hormones, is a practice that has already been reported. Consequently, stabilization of urine samples with a suitable method in a way that protects samples’ integrity is important. Currently, no stabilization method is applied in the sample collection equipment system in order to prevent degradation of urine compounds. The present work is an overview of a study, funded by WADA, on degradation and stabilization aspects of sports urine samples against the above threats of degradation. Extensive method development resulted in the creation of a mixture of chemical agents for the stabilization of urine. Evaluation of results demonstrated that the stabilization mixture could stabilize endogenous steroids, recombinant EPO, and human chorionic gonadotropin in almost the entire range of the experimental conditions tested.


Bioanalysis | 2014

Advances in the detection of designer steroids in anti-doping

Wadha Abushareeda; Argyro Fragkaki; Ariadni Vonaparti; Yiannis S. Angelis; Maria Tsivou; Khadija Saad; Souheil Kraiem; Emmanouil Lyris; Mohammed Alsayrafi; Costas Georgakopoulos

The abuse of unknown designer androgenic anabolic steroids (AAS) is considered to be an issue of significant importance, as AAS are the choice of doping preference according to World Anti-doping Agency statistics. In addition, unknown designer AAS are preferred since the World Anti-doping Agency mass spectrometric identification criteria cannot be applied to unknown molecules. Consequently, cheating athletes have a strong motive to use designer AAS in order to both achieve performance enhancement and to escape from testing positive in anti-doping tests. To face the problem, a synergy is required between the anti-doping analytical science and sports anti-doping regulations. This Review examines various aspects of the designer AAS. First, the structural modifications of the already known AAS to create new designer molecules are explained. A list of the designer synthetic and endogenous AAS is then presented. Second, we discuss progress in the detection of designer AAS using: mass spectrometry and bioassays; analytical data processing of the unknown designer AAS; metabolite synthesis; and, long-term storage of urine and blood samples. Finally, the introduction of regulations from sports authorities as preventive measures for long-term storage and reprocessing of samples, initially reported as negatives, is discussed.


Clinica Chimica Acta | 2010

Stabilization of human urine doping control samples: III. Recombinant human erythropoietin

Maria Tsivou; Helen Dimopoulou; I. P. Leontiou; Dimitrios G. Georgakopoulos; Michael A. Koupparis; Julia Atta-Politou; Costas Georgakopoulos

BACKGROUND The tampering of athletes urine samples by the addition of proteolytic enzymes during the doping control sampling procedure was reported recently. The aim of the current study, funded by the World Anti-Doping Agency (WADA), was the application of a stabilization mixture in urine samples to chemically inactivate proteolytic enzymes and improve the electrophoteric signal of erythropoietin (EPO) in human urine. METHODS The stabilization mixture applied was a combination of antibiotics, antimycotic substances and protease inhibitors. A series of incubation experiments were conducted under controlled conditions in the presence and absence of the stabilization mixture in urine aliquots spiked with six proteases. Two different analytical techniques were applied for the qualitative and quantitative EPO measurement: isoelectric focusing (IEF) and chemiluminescent immunoassay respectively. RESULTS The addition of the chemical stabilization mixture into urine aliquots substantially improved EPO detection in the presence of proteolytic enzymes following incubation at 37 degrees C or storage at -20 degrees C. CONCLUSIONS The results of this study indicated that the stabilization of urine prior to the sample collection procedure with the proposed chemical mixture might prove to be a useful tool for the preservation of anti-doping samples.


Journal of Chromatography B | 2013

A generic screening methodology for horse doping control by LC–TOF-MS, GC–HRMS and GC–MS

Maroula K. Kioussi; Emmanouil Lyris; Yiannis S. Angelis; Maria Tsivou; Michael A. Koupparis; Costas Georgakopoulos

In the present study a general screening protocol was developed to detect prohibited substances and metabolites for doping control purposes in equine sports. It was based on the establishment of a unified sample preparation and on the combined implementation of liquid and gas chromatographic MS analysis. The sample pretreatment began with two parallel procedures: enzymatic hydrolysis of sulfate and glucuronide conjugates, and methanolysis of the 17β-sulfate steroid conjugates. The extracts were treated for LC-TOF-MS, GC-HRMS and GC-MS assays. The majority of the prohibited substances were identified through a high mass accuracy technique, such as LC-TOF-MS, without prior derivatization. The sample preparation procedure included the formation of methylated and trimethylsilylated derivatives common in toxicological GC-MS libraries. The screening method was enhanced by post-run library searching using automated mass spectral deconvolution and identification system (AMDIS) combined with deconvolution reporting software (DRS). The current methodology is able to detect the presence of more than 350 target analytes in horse urine and may easily incorporate a lot of new substances without changes in chromatography. The full scan acquisition allows retrospective identification of prohibited substances in stored urine samples after reprocessing of the acquired data. Validation was performed for sixty representative compounds and included limit of detection, matrix interference - specificity, extraction recovery, precision, mass accuracy, matrix effect and carry over contamination. The suitability of the method was demonstrated with previously declared positive horse urine samples.


Drug Testing and Analysis | 2017

Doping control container for urine stabilization: a pilot study

Maria Tsivou; Evangelia Giannadaki; Fiona Hooghe; K. Roels; Wim Van Gansbeke; Flaminia Garribba; Emmanouil Lyris; Koen Deventer; Monica Mazzarino; Francesco Donati; Dimitrios G. Georgakopoulos; Peter Van Eenoo; Costas Georgakopoulos; Xavier de la Torre; Francesco Botrè

Urine collection containers used in the doping control collection procedure do not provide a protective environment for urine, against degradation by microorganisms and proteolytic enzymes. An in-house chemical stabilization mixture was developed to tackle urine degradation problems encountered in human sport samples, in cases of microbial contamination or proteolytic activity. The mixture consists of antimicrobial substances and protease inhibitors for the simultaneous inactivation of a wide range of proteolytic enzymes. It has already been tested in lab-scale, as part of World Anti-Doping Agencys (WADA) funded research project, in terms of efficiency against microbial and proteolytic activity. The present work, funded also by WADA, is a follow-up study on the improvement of chemical stabilization mixture composition, application mode and limitation of interferences, using pilot urine collection containers, spray-coated in their internal surface with the chemical stabilization mixture. Urine in plastic stabilized collection containers have been gone through various incubation cycles to test for stabilization efficiency and analytical matrix interferences by three WADA accredited Laboratories (Athens, Ghent, and Rome). The spray-coated chemical stabilization mixture was tested against microorganism elimination and steroid glucuronide degradation, as well as enzymatic breakdown of proteins, such as intact hCG, recombinant erythropoietin and small peptides (GHRPs, ipamorelin), induced by proteolytic enzymes. Potential analytical interferences, observed in the presence of spray-coated chemical stabilization mixture, were recorded using routine screening procedures. The results of the current study support the application of the spray-coated plastic urine container, in the doping control collection procedure. Copyright


Analytical and Bioanalytical Chemistry | 2010

Stabilization of human urine doping control samples: IV. Human chorionic gonadotropin

Maria Tsivou; Helen Dimopoulou; Dimitris G. Georgakopoulos; Michael Α. Koupparis; Julia Atta-Politou; Costas Georgakopoulos


Drug Testing and Analysis | 2017

Challenges in detecting substances for equine anti-doping

A.G. Fragkaki; N. Kioukia-Fougia; Polyxeni Kiousi; Maroula K. Kioussi; Maria Tsivou


Drug Testing and Analysis | 2018

HUMAN IN‐VIVO METABOLISM STUDY OF LGD‐4033

A.G. Fragkaki; P. Sakellariou; Polyxeni Kiousi; N. Kioukia-Fougia; Maria Tsivou; M. Petrou; Yiannis S. Angelis

Collaboration


Dive into the Maria Tsivou's collaboration.

Top Co-Authors

Avatar

Dimitrios G. Georgakopoulos

Agricultural University of Athens

View shared research outputs
Top Co-Authors

Avatar

Julia Atta-Politou

National and Kapodistrian University of Athens

View shared research outputs
Top Co-Authors

Avatar

Emmanouil Lyris

Olympic Athletic Center of Athens Spiros Louis

View shared research outputs
Top Co-Authors

Avatar

Helen Dimopoulou

Olympic Athletic Center of Athens Spiros Louis

View shared research outputs
Top Co-Authors

Avatar

Michael A. Koupparis

National and Kapodistrian University of Athens

View shared research outputs
Top Co-Authors

Avatar

Polyxeni Kiousi

National and Kapodistrian University of Athens

View shared research outputs
Top Co-Authors

Avatar

Yiannis S. Angelis

Olympic Athletic Center of Athens Spiros Louis

View shared research outputs
Top Co-Authors

Avatar

Argyro Fragkaki

Olympic Athletic Center of Athens Spiros Louis

View shared research outputs
Top Co-Authors

Avatar

D. Livadara

National and Kapodistrian University of Athens

View shared research outputs
Top Co-Authors

Avatar

Maroula K. Kioussi

National and Kapodistrian University of Athens

View shared research outputs
Researchain Logo
Decentralizing Knowledge