Center for Implantable Technology and Sensors

Ljubljana, Slovenia

Center for Implantable Technology and Sensors

Ljubljana, Slovenia
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Peclin P.,Center for Implantable Technology and Sensors | Rozman J.,Center for Implantable Technology and Sensors | Rozman J.,University of Ljubljana
IFMBE Proceedings | Year: 2017

The methodology, technology of fabrication and testing a multielectrode spiral cuff for selective activation of fibres in particular superficial regions of a peripheral nerve is presented. Stimulating electrodes were made of 0.03-mm-thick platinum foil strips with 99.99 wt.% purity. Optimum conditions for welding the stainless steel wire with the platinum foil and to reveal the microstructure of the welds were defined using the scanning electron microscopy. The electrochemical performance of platinum electrodes within a multi- electrode spiral cuff was investigated “in vitro” while stimulating performance was tested “in vivo”. The fabricated cuff consists of 33 electrodes organised in eleven longitudinal groups of three electrodes. The total cuff length is 17 mm and internal diameter is 2.5mm to fit the size of the human cervical vagus nerve. Results show that welds do not show any welding defects. The results of “in vitro” testing showed that potentials across the electrode-electrolyte interface did not exceed the safe potential limits for water electrolysis. The observed effects of “in vivo” testing with a stimuli train via triplet of electrodes 1 and current intensity ic=2.5 mA, modified selectively autonomic control of the SA and/or AV node. © Springer Nature Singapore Pte Ltd. 2017.

Zuzek M.C.,University of Ljubljana | Rozman J.,Center for Implantable Technology and Sensors | Rozman J.,University of Ljubljana | Peclin P.,Center for Implantable Technology and Sensors | And 2 more authors.
Biomedizinische Technik | Year: 2017

The ability to selectively stimulate AαAβ-fibers and Aδ-fibers in an isolated rat sciatic nerve (SNR) was assessed. The stimulus used was a current, biphasic pulse with a quasitrapezoidal cathodic phase and rectangular anodic phase where parameters were systematically varied: intensity of the cathodic phase (ic); width of the cathodic phase (tc); width of the cathodic exponential decay (texp) and time constant of the exponential decay (τexp). A SNR was stimulated using a pair of hook electrodes while conduction velocity (CV) and compound action potentials (CAP) were measured at two sites along the SNR using another two pairs of electrodes. Results showed that the highest CAP1 (8.5-9 mV), shall be expected when parameters of the stimulus were within the following range: ic=3.8-4 mA, tc =350-400μs and texp=330-440 μs. Results also showed that with ascending tc and texp, CV of the corresponding superficial region of the SNR was reduced in both, conduction velocity of CAP1 and conduction velocity of CAP2. It was concluded that action potentials (APs) were activated in the Aβ-fibers and Aδ-fibers along with a slight AP inhibition in the Aβ-fibers. The obtained results, could serve as a tool for developing multi-electrode systems that potentially enable fiber-type selective stimulation of nerve fibers. © 2017 Walter de Gruyter GmbH, Berlin/Boston.

Mirkovic T.,University of Ljubljana | Knezevic I.,University of Ljubljana | Radan I.,University of Ljubljana | Rozman J.,Center for Implantable Technology and Sensors | And 2 more authors.
Signa Vitae | Year: 2012

Activation of the parasympathetic pathway leads to negative chronotropic, dromotropic, and inotropic changes of heart function. The ability to selectively stimulate certain superficial compartments of peripheral nerves has been demonstrated previously. The aim of the present study was to find a clinically acceptable selective biphasic vagus nerve stimulation technique, which could allow gradual regulation of heart rate and systemic arterial pressure. In two patients, the left vagus nerve was stimulated with a combination of quasi-trapezoidal cathodic and rectangular anodic current pulses with different stimulation frequencies (10Hz, 20Hz, 30Hz) and increasing current. The heart rate and systemic arterial pressure decreased with increasing current at all different stimulation frequencies (p<0.05). The heart rate and arterial pressure response was more gradual with 10Hz compared to 20Hz/30Hz vagus nerve stimulation (p<0.05). In conclusion, selective vagus nerve stimulation, with a combination of quasi-trapezoidal cathodic and rectangular anodic current pulses at 10Hz, offers gradual heart rate and systolic arterial pressure control.

Rozman J.,Center for Implantable Technology and Sensors | Rozman J.,University of Ljubljana | Zuzek M.C.,University of Ljubljana | Frangez R.,University of Ljubljana | Ribaric S.,University of Ljubljana
Materiali in Tehnologije | Year: 2016

In this study we designed and tested a four-probe, bio-impedance measurement set-up for peripheral nerves, based on the Red Pitaya open-source measurement and control tool. The set-up was tested on an isolated rat sciatic nerve (RSN) while it was stimulated with specific current stimulating pulses. The measurements tested the hypothesis that the specific waveform of a stimulating pulse elicits current differences at the double layer (DL) interface between the platinum (Pt) stimulating electrode and the nerve tissue. Impedance spectroscopy was used to electrically characterize the interface between the Pt electrode and the nerve tissue and measure the interface electrical impedance (Z). An analysis of the frequency response and the impedance, with specific current stimulating pulses, characterised the structure and the composition-related electrical properties of the RSN. An analysis of the voltage responses (VRs), measured at the same time, showed that the maximum negative polarization across the electrode-electrolyte interface (Emc) and the maximum positive polarization across the electrode-electrolyte interface (Ema) did not exceed the safety limits for water electrolysis. We conclude that the voltage and current changes, elicited at the DL of the interface between the Pt stimulating electrode and the nerve tissue, do not lead to tissue damage. Based on the obtained electrophysiological results we conclude that the developed stimulating electrodes and the stimulus pattern could act as a useful tool for developing nerve-stimulating electrodes.

Peclin P.,Center for Implantable Technology and Sensors | Bizjak M.,University of Ljubljana | Pribosek M.,Marko Pribosek | Godec M.,Slovenian Institute of Metals And Technology | And 2 more authors.
Materiali in Tehnologije | Year: 2013

In the past few decades, considerable efforts have been devoted to develop neuroprosthetics that interface selectively with the human nervous system via multi-electrode spiral cuffs, using implantable electronic devices. The objective of this study was to investigate the structural properties of a cold-rolled platinum foil used to manufacture multi-electrode spiral nerve cuffs. To achieve this objective, thick cold-rolled platinum foil strips 0.03 mm with 99.99 % purity were used. For this purpose, the strips were mounted into the sample holder within the furnace of a custom-designed set-up. The resistivity measurements were made using a 4-point probe technique in which the strips were subjected to dynamic annealing in an argon atmosphere within the temperature range between room temperature and 900 °C. Finally, the microstructures of the strips, prepared using standard metallographic techniques, were investigated using light microscopy. In the resistivity measurements, a small change is observed at !280 °C. This change could be explained as the partial recovery elicited by a decrease of the dislocation density. Above 500 °C, a significant decrease in the resistivity was recorded, and the decrease reached a maximum at !750 °C. These results provide a deeper insight into the fabrication of platinum foil to be used in the further development of multi-electrode neural stimulating spiral cuffs. The most important finding is that the results of the resistivity measurements provide one criterion for selecting materials, and that the appropriate thermal and mechanical working processes are required to fabricate stimulating electrodes. These results may make cold-rolled platinum ribbon the best material for the long-term application of multi-electrode spiral cuffs in SNS.

Lainscak M.,University Clinic of Respiratory and Allergic Diseases Golnik | Lainscak M.,Applied Cachexia Research | Podbregar M.,University of Ljubljana | Kovacic D.,General Hospital Celje | And 3 more authors.
Respiratory Medicine | Year: 2011

Chronic obstructive pulmonary disease (COPD) frequently coexists in patients with chronic heart failure (CHF) and is a key factor for beta blocker underprescription and underdosing. This study compared effects of bisoprolol and carvedilol in patients with both conditions. This was a randomized open-label study, of bisoprolol and carvedilol during initiation and uptitration to target of maximal tolerated dose. Pulmonary function testing, 12-lead electrocardiogram, and N-terminal pro brain natriuretic peptide were measured at baseline and follow-up. We randomized 63 elderly patients (73±9 years, 81 men, left ventricular ejection fraction 33±7) with mild to moderate CHF (54 New York Heart Assocation class II) and moderate to severe COPD (76 Global initiative for chronic Obstructive Lung Disease stage 2). Target dose was tolerated by 31 (49) patients and 19 (30) patients experienced adverse events during follow-up (19 bisoprolol, 42 carvedilol, p = 0.045). Study medication had to be withdrawn in 8 (13) patients (bisoprolol: 2 due to hypotension, 1 due to bradycardia; carvedilol: 2 due to hypotension and 1 due to wheezing, dyspnoea, and oedema, respectively). Forced expiratory volume in 1 st second significantly increased in bisoprolol (1561±414ml to 1698±519ml, p = 0.046) but not carvedilol (1704±484 to 1734±548, p = 0.44) group. Both agents reduced heart rate (bisoprolol: 75±14 to 68±10, p = 0.007; carvedilol 78±14 to 72±12, p = 0.016) and had no effect on N-terminal pro brain natriuretic peptide. Beta blockers frequently caused adverse events, and thus 49 of patients could tolerate the target dose. Bisoprolol induced demonstrable improvement in pulmonary function and caused less adverse events. © 2011 Elsevier Ltd. All rights reserved.

Hocevar Z.,University of Ljubljana | Rozman J.,Center for Implantable Technology and Sensors | Paska A.V.,University of Ljubljana | Frangez R.,University of Ljubljana | And 2 more authors.
Journal of Ultrasound in Medicine | Year: 2012

Objectives - This study evaluated the possible effects of ultrasound (US) on gene expression in brain tissue of rat embryos. Methods - Four groups (n = 5 each) of pregnant Wistar Han rats were exposed to US for different durations (55, 100, 145, and 195 seconds) via a multifrequency transducer in the 2-dimensional imaging mode with a pulse duration of 1.29 microseconds, a pulse repetition frequency of 1 kHz, and a derated spatial-peak pulse-average intensity of 222.4 W/cm 2 on day 5, 9, 7, or 13 of gestation. Gene expression profiling was performed in fetal brain tissue (n = 5 per group) by quantitative reverse transcription-polymerase chain reaction arrays. Results - The results indicated substantial alterations in gene expression. The most differentially expressed genes were Adamts5, Gadd45a, Npy2r, and Chrna1, which are implicated in important developmental signaling pathways. Conclusions - On the basis of our findings, routine short US examinations for monitoring fetal development are not contraindicated, but prolonged exposures should be used only when needed to obtain important diagnostic information. © 2012 by the American Institute of Ultrasound in Medicine.

PubMed | Center for Implantable Technology and Sensors and University of Ljubljana
Type: Journal Article | Journal: Artificial organs | Year: 2015

The trend in neural prostheses using selective nerve stimulation for electrical stimulation therapies is headed toward single-part systems having a large number of working electrodes (WEs), each of which selectively stimulate neural tissue or record neural response (NR). The present article reviews the electrochemical and electrophysiological performance of platinum WE within a ninety-nine-electrode spiral cuff for selective nerve stimulation and recording of peripheral nerves, with a focus on the vagus nerve (VN). The electrochemical properties of the WE were studied in vitro using the electrochemical impedance spectroscopy (EIS) technique. The equivalent circuit model (ECM) of the interface between the WE and neural tissue was extracted from the EIS data and simulated in the time domain using a preset current stimulus. Electrophysiological performance of in-space and fiber-type highly selective vagus nerve stimulation (VNS) was tested using an isolated segment of a porcine VN and carotid artery as a reference. A quasitrapezoidal current-controlled pulse (stimulus) was applied to the VN or arterial segment using an appointed group of three electrodes (triplet). The triplet and stimulus were configured to predominantly stimulate B-fibers and minimize the stimulation of A-fibers. The EIS results revealed capacitive charge transfer predominance, which is a highly desirable property. Electrophysiological performance testing indicated the potential existence of certain parameters and waveforms of the stimulus for which the contribution of the A-fibers to the NR decreased slightly and that of the B-fibers increased slightly. Findings show that the design of the stimulating electrodes, based on the EIS and ECM results, could act as a useful tool for nerve cuff development.

Peclin P.,Center for Implantable Technology and Sensors | Rozman J.,Center for Implantable Technology and Sensors
2013 36th International Convention on Information and Communication Technology, Electronics and Microelectronics, MIPRO 2013 - Proceedings | Year: 2013

In this study we have developed a model of using a thirty-nine-electrode spiral nerve cuff for selective stimulation of fibres in the left vagus nerve of a man to control the heart rate and tachycardia in particular. Furthermore, according to our recent work on experiments in human, we predicted the precisely defined stimulus shape and parameters. In a forthcoming study we are to conduct experiments to determine the effect of cervical selective vagus nerve stimulation (VNS) on the atrial fibrillation in a man using a developed model and designed implantable thirty-nine-electrode spiral cuff. Specifically, we intend to look at the effects on the atrial fibrillation when the superficial compartments of the left vagus nerve, including the cardiac branches containing nerve fibres A, B and C, are selectively stimulated with the precisely defined stimulation parameters. © 2013 MIPRO.

PubMed | Center for Implantable Technology and Sensors
Type: Journal Article | Journal: Australasian physical & engineering sciences in medicine | Year: 2014

In this study, the electrochemical performance of platinum electrodes within a multi-electrode spiral cuff to be used for selective nerve stimulation was investigated. The original cuff, simplified into a half-cuff, contained a single row of nine electrodes (0.52mm) at a distance of 2mm from its inner surface. Cyclic voltammetry was used to investigate the electrochemical reactions at the electrode-electrolyte interface, to define a potential window within which the electrode could be safely used in selective nerve stimulation, to calculate the charge injection capacity and cathodal charge storage capacity. Voltage transients retrieved during excitation with quasitrapezoidal biphasic current pulses, tested by selective nerve stimulation of the isolated porcine left cervical vagus nerve segment, were used to determine the maximum polarization across the electrode-electrolyte interface and to calculate cathodic charge injection capacity of the electrode. The results show that the most negative and most positive potentials across the electrode-electrolyte interface reached -0.54 and 0.59V; these did not exceed the safe potential limits for water electrolysis. Furthermore, the time integral of the cathodic current by cyclic voltammetry measured over the potential range of water electrolysis, actually representing the cathodal charge storage capacity, was approximately -4mCcm(-2). The charge injection capacity, representing the maximum charge density injected in a current stimulation pulse, using only reversible processes, however, was around 75Ccm(-2). In conclusion, both, the tested stimulation pulse and electrode are suitable for efficient and safe selective nerve stimulation.

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