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Dive into the research topics where Alessandro Bizzarri is active.

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Featured researches published by Alessandro Bizzarri.


Circulation | 2011

Increased Adipose Tissue Oxygen Tension in Obese Compared With Lean Men Is Accompanied by Insulin Resistance, Impaired Adipose Tissue Capillarization, and Inflammation

Gijs H. Goossens; Alessandro Bizzarri; Nicolas Venteclef; Yvonne Essers; Jack P.M. Cleutjens; Ellen Konings; Johan W.E. Jocken; Merima Čajlaković; Volker Ribitsch; Karine Clément; Ellen E. Blaak

Background— Adipose tissue (AT) dysfunction in obesity contributes to chronic, low-grade inflammation that predisposes to type 2 diabetes mellitus and cardiovascular disease. Recent in vitro studies suggest that AT hypoxia may induce inflammation. We hypothesized that adipose tissue blood flow (ATBF) regulates AT oxygen partial pressure (AT PO2), thereby affecting AT inflammation and insulin sensitivity. Methods and Results— We developed an optochemical measurement system for continuous monitoring of AT PO2 using microdialysis. The effect of alterations in ATBF on AT PO2 was investigated in lean and obese subjects with both pharmacological and physiological approaches to manipulate ATBF. Local administration of angiotensin II (vasoconstrictor) in abdominal subcutaneous AT decreased ATBF and AT PO2, whereas infusion of isoprenaline (vasodilator) evoked opposite effects. Ingestion of a glucose drink increased ATBF and AT PO2 in lean subjects, but these responses were blunted in obese individuals. However, AT PO2 was higher (hyperoxia) in obese subjects despite lower ATBF, which appears to be explained by lower AT oxygen consumption. This was accompanied by insulin resistance, lower AT capillarization, lower AT expression of genes encoding proteins involved in mitochondrial biogenesis and function, and higher AT gene expression of macrophage infiltration and inflammatory markers. Conclusions— Our findings establish ATBF as an important regulator of AT PO2. Nevertheless, obese individuals exhibit AT hyperoxia despite lower ATBF, which seems to be explained by lower AT oxygen consumption. This is accompanied by insulin resistance, impaired AT capillarization, and higher AT gene expression of inflammatory cell markers. Clinical Trial Registration— URL: http://www.trialregister.nl. Unique identifier: NTR2451.


Biosensors and Bioelectronics | 2009

Optical oxygen sensors based on Pt(II) porphyrin dye immobilized on S-layer protein matrices

Sylvia R. Scheicher; Birgit Kainz; Stefan Köstler; Michael Suppan; Alessandro Bizzarri; Dietmar Pum; Uwe B. Sleytr; Volker Ribitsch

This paper describes the development of planar and fiber optic oxygen sensors utilizing surface layer (S-layer) proteins as immobilization matrix for oxygen sensitive dyes. S-layer proteins have the intrinsic capability to reassemble into two-dimensional arrays in suspension and at interfaces. Due to their crystalline character the distribution of functional groups, such as carboxylic groups, is repeated with the periodicity of the lattice and thus allows the reproducible and geometrically distinct binding of functional molecules. For the development of oxygen sensors an oxygen sensitive Pt(II) porphyrin dye was covalently bound to the S-layer matrix. Measurement of the oxygen concentration was performed by phase modulation fluorimetry. Setups comprising low cost optoelectronic components like LEDs and silicon photodiodes were constructed. For both sensor setups (planar and fiber optic) variations in the oxygen concentrations resulted in distinct and reproducible changes in luminescence lifetime and intensity. The luminescence quenching efficiency of these sensors was found to be 1.5-1.9 (expressed as the ratio of signal under nitrogen and air) which compares well to other sensor systems using luminophores embedded in polymer matrices. These results demonstrated the application potential of S-layers as immobilization matrices in the development of (bio-)sensors.


ieee sensors | 2009

Opto-chemical method for ultra-low oxygen transmission rate measurement

Martin Tscherner; Christian Konrad; Alessandro Bizzarri; Michael Suppan; Merima Čajlaković; Volker Ribitsch; F. Stelzer

A highly sensitive alternative to established methods for measuring oxygen transmission rates of ultra-barrier membranes is presented. The key idea is the employment of an opto-chemical sensor (a luminescent dye immobilized in a matrix) which has vital advantages over electrochemical sensors, such as consumption-less detection and extraordinary sensitivity. The luminescent response to modulated light, which is altered in the presence of oxygen, is recorded by an opto-electronic instrument in a non-invasive manner. Provided with said sensing system, a reusable stand-alone permeation cell was developed. Unlike in conventional devices, the permeating oxygen is accumulated while being simultaneously monitored. The demonstrator unit achieves a limit of detection in the 10−5 cm3 m−2 day−1 bar−1 regime. It is therefore among the most sensitive O2 permeability testers, outperforming commercial instruments by two orders of magnitude, yet offering reusability and similar convenience in operation.


ieee sensors | 2007

New developments of an optochemical measurement system for the continuous monitoring in subcutaneous tissue by microdialysis

Alessandro Bizzarri; Christian Konrad; Merima Čajlaković; Volker Ribitsch

The monitoring of dissolved 02 in blood and organic tissues is extremely useful for physiological and respiratory studies and for monitoring the health conditions of hospitalized patients. Based on these demands an optochemical measurement system for the continuous monitoring of 02 in subcutaneous adipose tissue of critically ill patients is reported The system consists of a miniaturized flow trough cell including an 02 sensitive layer, an optoelectronic measuring unit and a microdialysis catheter for the extraction of the biological fluid. The measurement principle is the phase modulation fluorometry. The sensor allows the 02 measurement in the range 0-300 mmHg, with a resolution better than 1 mmHg and an accuracy better than plusmn1 mmHg. With respect to a previously reported instrumentation, this measurement system shows a high degree of miniaturization and an improved production reproducibility of the optochemical sensing layers. This new instrumentation has been extensively validated in laboratory and in-vivo tests.


ieee sensors | 2009

Simultaneously monitoring of tissue O 2 and CO 2 partial pressures by means of miniaturized implanted fiber optical sensors

Merima Čajlaković; Alessandro Bizzarri; Michael Suppan; Christian Konrad; Martin Tscherner; Volker Ribitsch; E. Beran; Igor Knez

A novel opto-chemical sensor instrumentation based on fiber optical micro-sensors for the simultaneous detection of pO2 and pCO2 in tissues is presented. The adopted sensing principle for both parameters is the measurement of luminescence lifetime via phase modulation fluorometry. Respect to currently used blood-gas analysers that require blood sampling and are associated with blood loss, this instrumentation allows on-line continuous measurements. Compared to electrochemical micro sensors, it is advantageous because of intrinsic higher sensitivity, no analyte consumption and less electromagnetic interferences. The results of the laboratory characterization and of tests in in vivo experiments of the proposed instrumentation are reported.


Advanced environmental, chemical, and biological sensing technologies. Conference | 2005

Interstitial pH, pO2 and pCO2 controlled by optical sensors

Francesco Baldini; Alessandro Bizzarri; Merima Čajlaković; Ambra Giannetti; Christian Konrad; Andrea Mencaglia

The continuous monitoring of interstitial pH, pO2 and pCO2 contained in the adipose tissue of intensive care patients, is one of the objective of the four year European project CLINICIP (Closed Loop Insulin Infusion in Critically Ill Patients). A glass capillary on line with the microfluidic system, is the solid support onto which the appropriate chemistry is immobilised. The optical working principle applied for the detection of oxygen and carbon dioxide is the modulation of the fluorescence lifetime, whereas absorption modulation is the approach followed for the pH detection. On this basis, two different optoelectronic units were developed for the interrogation of the glass capillary, one for life-time measurements and the other for absorption measurements. Preliminary tests demonstrated a resolution of 0.03 pH units for pH; ≤ 0.55 mmHg for oxygen and ≤ 0.6 mmHg for carbon dioxide; and an accuracy of 0.07 pH units for pH; ≤ 1 mmHg for oxygen and ≤ 1.5 mmHg for carbon dioxide.


Archive | 2012

Optochemical Sensor Systems for In-Vivo Continuous Monitoring of Blood Gases in Adipose Tissue and in Vital Organs

Merima Čajlaković; Alessandro Bizzarri; Gijs H. Goossens; Igor Knez; Michael Suppan; Ismar Ovcina; Volker Ribitsch

Merima Cajlakovic1, Alessandro Bizzarri1, Gijs H. Goossens2, Igor Knez3, Michael Suppan1, Ismar Ovcina3 and Volker Ribitsch1 1Joanneum Research Forschungsgesellschaft mbH, MATERIALS Institute for Surface Technologies and Photonic, Sensorsystems, Graz, 2Department of Human Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 3Department of Cardiac Surgery, University Clinic of Surgery, Medical University Graz, Graz, 2The Netherlands 1,3Austria


ieee sensors | 2007

Optical Sensors Based on S-Layer Proteins

C. Konrad; Michael Suppan; Alessandro Bizzarri; Sylvia R. Scheicher; Volker Ribitsch; Birgit Kainz; Dietmar Pum; Uwe B. Sleytr

In this paper the use of a special class of self assembling protein materials for optical sensor technology is discussed. These S-layer proteins were reassembled into well defined nanostructures on solid sensor surfaces. The covalent immobilization of fluorescent dyes onto these protein structures was investigated. Following this approach a new oxygen sensitive system based on S-layers functionalized with Pt(II) metalloporphyrin is described. A luminescence lifetime based measurement system for dissolved oxygen sensing was successfully developed.


Circulation | 2012

Response to Letter Regarding Article, “Increased Adipose Tissue Oxygen Tension in Obese Compared With Lean Men Is Accompanied by Insulin Resistance, Impaired Adipose Tissue Capillarization, and Inflammation”

Gijs H. Goossens; Yvonne Essers; Ellen Konings; Johan W.E. Jocken; Ellen E. Blaak; Alessandro Bizzarri; Merima Čajlaković; Volker Ribitsch; Karine Clément; Nicolas Venteclef; Jack P.M. Cleutjens

We thank Drs Lecoultre and Tam for their thoughtful comments and interest in our recent publication.1 They question whether the higher adipose tissue (AT) oxygen partial pressure (Po2) in obese insulin resistant men compared with lean insulin sensitive men should be considered as hyperoxia. Abdominal subcutaneous AT Po2 showed substantial interindividual variation both in our study (range 24–85 mm Hg)1 and in another human study that assessed AT Po2 in subcutaneous AT of the abdomen.2 We also demonstrated that pharmacological and physiological manipulation of AT blood flow induced concomitant alterations in AT Po2 in lean subjects. In our opinion, these findings indicate substantial flexibility of AT …


Analytica Chimica Acta | 2006

Continuous oxygen monitoring in subcutaneous adipose tissue using microdialysis.

Alessandro Bizzarri; Hans Koehler; Merima Čajlaković; Alen Pasic; Lukas Schaupp; Ingo Klimant; Volker Ribitsch

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Ellen Konings

Maastricht University Medical Centre

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