Publications (4)14.46 Total impact
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Article: Subcutaneous blood pressure monitoring with an implantable optical sensor.
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ABSTRACT: We introduce a minimally invasive, implantable system that uses pulse transit time to determine blood pressure. In contrast to previous approaches, the pulse wave is detected by a photoplethysmographic (PPG) signal, acquired with high quality directly on subcutaneous muscle tissue. Electrocardiograms (ECG) were measured with flexible, implantable electrodes on the same tissue. PPG detection is realized by a flat 20 mm x 6 mm optoelectronic pulse oximeter working in reflection mode. The optical sensor as well as the ECG electrodes can be implanted using minimally invasive techniques, with only a small incision into the skin, making long-term monitoring of blood pressure in day-to-day life for high-risk patients possible. The in vivo measurements presented here show that the deviation to intra-arterial reference measurements of the systolic blood pressure in a physiologically relevant range is only 5.5 mmHg, demonstrated for more than 12 000 pulses. This makes the presented sensor a grade B blood pressure monitor.Biomedical Microdevices 05/2013; · 3.03 Impact Factor -
Article: Scaffold-based transplantation of akt1-overexpressing skeletal myoblasts: functional regeneration is associated with angiogenesis and reduced infarction size.
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ABSTRACT: Myoblast-based therapy can improve cardiac function after infarction and is conventionally performed by direct injection. A scaffold-based transfer could overcome injection-associated problems. In upgrading this approach we transplanted skeletal myoblasts (SkM) overexpressing the prosurvival gene Akt1. SkM were transfected with pcDNA3-huda-Akt1 and seeded on polyurethane scaffolds. These scaffolds were transplanted in rats 2 weeks after myocardial infarction. Hemodynamics were analyzed before therapy and 6 weeks later. Infarction size and capillary density were performed thereafter. Additional groups received injections of Akt1-transfected or untransfected myoblasts, scaffolds seeded with untransfected myoblasts, or sham operation. Deterioration of global systolic left ventricular function could be inhibited by all therapeutic approaches. In addition, transplantation of Akt1-transfected cells, either scaffold-based or injected, was superior with regard to systolic properties of the left ventricular wall. This effect was accompanied by smaller infarction sizes and angiogenesis. Scaffolds with untransfected myoblasts yielded also smaller infarctions than injections of untransfected myoblasts. Both Akt groups profited with regard to dP/dt(min). In contrast, other diastolic parameters pointed at impaired relaxation and stiffer myocardium especially in the Akt1-scaffold group. In conclusion, SkM overexpressing Akt1 can maintain myocardial function after infarction, reduce infarction size, and induce neovascularization. Scaffold-based cell transfer does not augment this reverse remodeling capacity.Tissue Engineering Part A 01/2011; 17(1-2):205-12. · 4.64 Impact Factor -
Article: Human neonatal thymus-derived mesenchymal stromal cells: characterization, differentiation, and immunomodulatory properties.
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ABSTRACT: Mesenchymal stromal cells represent an attractive cell population for cell transplantation and tissue engineering purposes. The aim of this study was to search for neonatal thymus-derived mesenchymal stromal cells (nTMSC) and further characterize the differentiation and immunomodulatory properties thereof. The thymus glands of 13 infants undergoing congenital cardiac surgery were removed. After in vitro isolation and expansion, we identified adherent stromal cells with substantial proliferation potential. As characterized by FACS, the pattern of surface antigen expression of nTMSC resembled bone marrow stromal cells. Full mesenchymal differentiation potential is maintained during proliferation as confirmed by cultures for osteogenic, chondrogenic, and adipogenic lineages. After 5-azacytidine enrichment, morphological characteristics of cardiomyocytes were achieved. For immunologic investigations, the influence of nTMSC on the proliferative behavior of peripheral blood mononuclear cells was studied as a measure of the immune response. The nTMSC did not stimulate an allogeneic reaction in this coculture. Further, the expression of immunologically relevant markers was measured. Alike MSC from other origins, nTMSC did not express MHC-II. In contrast to mature MSC, some nTMSC even lack the expression of MHC-I. Our results confirm that the neonatal thymus contains mesenchymal stromal cells (nTMSC) with full mesenchymal differentiation potential and immunomodulatory properties.Tissue Engineering Part A 02/2009; 15(7):1787-96. · 4.64 Impact Factor -
Article: Development of an implantable pulse oximeter.
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ABSTRACT: A long-term implantable photoplethysmographic sensor system is proposed. The system employs an elastic cuff which is directly wrapped around an arterial blood vessel. The optically transparent cuff is equipped with light emitting diodes and a photo transistor including the technology of pulse oximetry. The sensor will permit real-time, continuous monitoring of important vital parameters such as arterial blood oxygen saturation and pulse rate over a long-term period in vivo. We emphasize on the specific requirements for design and instrumentation of the implantable sensor and discuss first in vitro data acquired with that new photonics-based sensor.IEEE transactions on bio-medical engineering 03/2008; 55(2 Pt 1):581-8. · 2.15 Impact Factor
