Browsing by Author "Bijelic, Goran"
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Item Adsorption characteristics of stoichiometric and nonstoichiometric molecular polyelectrolyte complexes on silicon oxynitride surfaces(2011-02-01) Shovsky, Alexander; Bijelic, Goran; Varga, Imre; Makuška, Ričardas; Claesson, Per M.; MercadoAdsorption properties of stoichiometric and nonstoichiometric polyelectrolyte complexes (PECs) have been investigated by means of dual polarization interferometry (DPI) and X-ray photoelectron spectroscopy (XPS). Poly(sodium styrenesulfonate) (NaPSS) of molecular weight 4300 g/mol was used as polyanion, and two bottle-brush copolymers possessing different molar ratios of the cationic segment methacryloxyethyltrimethylammonium chloride (METAC) and the nonionic segment poly(ethylene oxide) methyl ether methacrylate (PEO 45MEMA) were used as polycations. They are referred to as PEO 45MEMA:METAC-25 and PEO45MEMA:METAC-50, where the last digits denote the mol % of charged main-chain segments. The time evolution of the adsorbed amount, thickness, and refractive index of the PEC layers were determined in aqueous solution using DPI. We demonstrate that cationic, uncharged, and negatively charged complexes adsorb to negatively charged silicon oxynitride and that maximum adsorption is achieved when small amounts of PSS are present in the complexes. The surface composition of the adsorbed PEC layers was estimated from XPS measurements that demonstrated very low content of NaPSS. On the basis of these data, the PEC adsorption mechanism is discussed and the competition between PSS and negative surface sites for association with the cationic polyelectrolyte is identified as a key issue.Item Computational and experimental model of transdermal iontophorethic drug delivery system(2017-11-30) Filipovic, Nenad; Saveljic, Igor; Rac, Vladislav; Graells, Beatriz Olalde; Bijelic, Goran; Biomateriales; MercadoThe concept of iontophoresis is often applied to increase the transdermal transport of drugs and other bioactive agents into the skin or other tissues. It is a non-invasive drug delivery method which involves electromigration and electroosmosis in addition to diffusion and is shown to be a viable alternative to conventional administration routs such as oral, hypodermic and intravenous injection. In this study we investigated, experimentally and numerically, in vitro drug delivery of dexamethasone sodium phosphate to porcine skin. Different current densities, delivery durations and drug loads were investigated experimentally and introduced as boundary conditions for numerical simulations. Nernst–Planck equation was used for calculation of active substance flux through equivalent model of homogeneous hydrogel and skin layers. The obtained numerical results were in good agreement with experimental observations. A comprehensive in-silico platform, which includes appropriate numerical tools for fitting, could contribute to iontophoretic drug-delivery devices design and correct dosage and drug clearance profiles as well as to perform much faster in-silico experiments to better determine parameters and performance criteria of iontophoretic drug delivery.Item Design of a photoelectrochemical lab-on-a-chip immunosensor based on enzymatic production of quantum dots in situ(2022-04-22) Díez-Buitrago, Beatriz; Fernández-San Argimiro, Francisco Javier; Lorenzo, Jaione; Bijelic, Goran; Briz, Nerea; Pavlov, Valeri; Tecnalia Research & Innovation; Biomateriales; Mercado; SGIn this work we report the development and validation of a photoelectrochemical immunosensor on the basis of alkaline phosphatase (ALP)-linked immunoassay for the detection of human serum albumin as a model analyte. In this biosensor, oriented immobilization of capture antibodies on aminated polystyrene was achieved via physical adsorption. After the interaction with the analyte, ALP immobilised on the surface through the sandwich immunoassay catalyses the hydrolysis of sodium thiophosphate (TP) to hydrogen sulphide (H2S) which in the presence of cadmium ions yields CdS quantum dots (QDs). The electrical current is generated in the course of the photoelectrochemical process (PEC) during irradiation of the CdS QDs with a UV LED (365 nm) on home-made screen-printed carbon electrodes modified with a conductive polymer. Reaction time, steps and volumes were optimized for the miniaturization of the process in order to develop a lab-on-a-chip platform. The microfluidic system was designed with optimised parameters to fabricate the immunosensor combining the immunoassay with PEC detection. The final system presents a sensitivity comparable to that of the commercial kit thanks to the signal amplification enabled by the enzymatic growth of CdS QDs in situ. This photoelectrochemical immunosensing strategy potentially opens up a new avenue for the detection of a wide range of analytes of interest due to the universal and effective enzymatic signal amplification method. Moreover, the developed bioanalytical device allows for a great reduction of time and reagents compared to exiting commercial assays, making it suitable for point-of-care applications.Item Fabrication of ultrahigh-molecular-weight polyethylene porous implant for bone application(2020-09-01) Olalde, Beatriz; Ayerdi-Izquierdo, Ana; Fernández, Rubén; García-Urkia, Nerea; Atorrasagasti, Garbiñe; Bijelic, Goran; Biomateriales; MercadoPorous implants play a crucial role in allowing ingrowth of host connective tissue and thereby help in keeping the implant in its place. With the aim of mimicking the microstructure of natural extracellular matrix, ultrahigh-molecular-weight polyethylene (UHMWPE) porous samples with a desirable pore size distribution were developed by combining thermally induced phase separation and salt leaching techniques. The porous UHMWPE samples consisted of a nanofibrous UHMWPE matrix with a fibre diameter smaller than 500 nm, highly interconnected, with a controllable pore diameter from nanoscale to 300 μm. Moreover, a porous UHMWPE sample was also developed as a continuous and homogeneous coating onto the UHMWPE dense sample. The dense/porous UHMWPE sample supported human foetal osteoblast 1.19 cell line proliferation and differentiation, indicating the potential of porous UHMWPE with a desirable pore size distribution for bone application. An osseointegration model in the sheep revealed substantial bone formation within the pore layer at 12 weeks via SEM evaluation. Ingrown bone was more closely opposed to the pore wall when compared to the dense UHMWPE control. These results indicate that dense/porous UHMWPE could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic application.Item Helping Hand grasp rehabilitation: Preliminary assessment on chronic stroke patients(IEEE Computer Society, 2017-08-10) Crema, Andrea; Guanziroli, Eleonora; Maleševic, Nebojsa; Colombo, Maria; Liberali, Davide; Proserpio, Davide; Bijelic, Goran; Keller, Thierry; Molteni, Franco; Micera, Silvestro; MercadoThe Helping Hand (HH) system is a novel grasp rehabilitation platform aimed at simplifying the clinical usage of wearable electrode arrays for neuromuscular electrical stimulation (NMES). In a randomized dose-matched, clinical study we evaluate usability and effectiveness of the HH treatment, and of other enriched upper limb rehabilitation treatments, and compare the outcomes. This paper shows the preliminary clinical results of the trial on 5 chronic stroke patients throughout a 9 weeks, 3 hours per week, hand preshaping training.Item High-throughput roll-to-roll production of polymer biochips for multiplexed DNA detection in point-of-care diagnostics(2020-11-21) Toren, Pelin; Smolka, Martin; Haase, Anja; Palfinger, Ursula; Nees, Dieter; Ruttloff, Stephan; Kuna, Ladislav; Schaude, Cindy; Jauk, Sandra; Rumpler, Markus; Hierschlager, Bettina; Katzmayr, Ingo; Sonnleitner, Max; Thesen, Manuel W.; Lohse, Mirko; Horn, Martin; Weigel, Wilfried; Strbac, Matija; Bijelic, Goran; Hemanth, Suhith; Okulova, Nastasia; Kafka, Jan; Kostler, Stefan; Stadlober, Barbara; Hesse, Jan; Tecnalia Research & Innovation; SG; MercadoRoll-to-roll UV nanoimprint lithography has superior advantages for high-throughput manufacturing of micro- or nano-structures on flexible polymer foils with various geometries and configurations. Our pilot line provides large-scale structure imprinting for cost-effective polymer biochips (4500 biochips/hour), enabling rapid and multiplexed detections. A complete high-volume process chain of the technology for producing structures like μ-sized, triangular optical out-couplers or capillary channels (width: from 1 μm to 2 mm, height: from 200 nm up to 100 μm) to obtain biochips (width: 25 mm, length: 75 mm, height: 100 μm to 1.5 mm) was described. The imprinting process was performed with custom-developed resins on polymer foils with resin thicknesses ranging between 125–190 μm. The produced chips were tested in a commercial point-of-care diagnostic system for multiplexed DNA analysis of methicillin resistant Staphylococcus aureus (e.g., mecA, mecC gene detections). Specific target DNA capturing was based on hybridisation between surface bound DNA probes and biotinylated targets from the sample. The immobilised biotinylated targets subsequently bind streptavidin–horseradish peroxidase conjugates, which in turn generate light upon incubation with a chemiluminescent substrate. To enhance the light out-coupling thus to improve the system performance, optical structures were integrated into the design. The limits-of-detection of mecA (25 bp) for chips with and without structures were calculated as 0.06 and 0.07 μM, respectively. Further, foil-based chips with fluidic channels were DNA functionalised in our roll-to-roll micro-array spotter following the imprinting. This straightforward approach of sequential imprinting and multiplexed DNA functionalisation on a single foil was also realised for the first time. The corresponding foil-based chips were able to detect mecA gene DNA sequences down to a 0.25 μM concentration.Item MiR-219a-5p Enriched Extracellular Vesicles Induce OPC Differentiation and EAE Improvement More Efficiently Than Liposomes and Polymeric Nanoparticles(2020-02) Osorio-Querejeta, Iñaki; Carregal-Romero, Susana; Ayerdi-Izquierdo, Ana; Mäger, Imre; Nash, Leslie A.; Wood, Matthew; Egimendia, Ander; Betanzos, M.; Alberro, Ainhoa; Iparraguirre, Leire; Moles, Laura; Llarena, Irantzu; Möller, Marco; Goñi-de-Cerio, Felipe; Bijelic, Goran; Ramos-Cabrer, Pedro; Muñoz-Culla, Maider; Otaegui, David; Tecnalia Research & Innovation; Biomateriales; MercadoRemyelination is a key aspect in multiple sclerosis pathology and a special effort is being made to promote it. However, there is still no available treatment to regenerate myelin and several strategies are being scrutinized. Myelination is naturally performed by oligodendrocytes and microRNAs have been postulated as a promising tool to induce oligodendrocyte precursor cell differentiation and therefore remyelination. Herein, DSPC liposomes and PLGA nanoparticles were studied for miR-219a-5p encapsulation, release and remyelination promotion. In parallel, they were compared with biologically engineered extracellular vesicles overexpressing miR-219a-5p. Interestingly, extracellular vesicles showed the highest oligodendrocyte precursor cell differentiation levels and were more effective than liposomes and polymeric nanoparticles crossing the blood–brain barrier. Finally, extracellular vesicles were able to improve EAE animal model clinical evolution. Our results indicate that the use of extracellular vesicles as miR-219a-5p delivery system can be a feasible and promising strategy to induce remyelination in multiple sclerosis patients.Item Multichannel electrotactile feedback with spatial and mixed coding for closed-loop control of grasping force in hand prostheses(2017-03) Dosen, Strahinja; Markovic, Marko; Strbac, Matija; Belic, Minja; Kojic, Vladimir; Bijelic, Goran; Keller, Thierry; Farina, Dario; SG; Mercado; Tecnalia Research & InnovationProviding somatosensory feedback to the user of a myoelectric prosthesis is an important goal since it can improve the utility as well as facilitate the embodiment of the assistive system. Most often, the grasping force was selected as the feedback variable and communicated through one or more individual single channel stimulation units (e.g., electrodes, vibration motors). In the present study, an integrated, compact, multichannel solution comprising an array electrode and a programmable stimulator was presented. Two coding schemes (15 levels), spatial and mixed (spatial and frequency) modulation, were tested in able-bodied subjects, psychometrically and in force control with routine grasping and force tracking using real and simulated prosthesis. The results demonstrated that mixed and spatial coding, although substantially different in psychometric tests, resulted in a similar performance during both force control tasks. Furthermore, the ideal, visual feedback was not better than the tactile feedback in routine grasping. To explain the observed results, a conceptual model was proposed emphasizing that the performance depends on multiple factors, including feedback uncertainty, nature of the task and the reliability of the feedforward control. The study outcomes, specific conclusions and the general model, are relevant for the design of closed-loop myoelectric prostheses utilizing tactile feedback.Item Numerical simulation of iontophoresis in the drug delivery system(2016-08-17) Filipovic, Nenad; Zivanovic, Marko; Savic, Andrej; Bijelic, Goran; Tecnalia Research & Innovation; MercadoThe architecture and composition of stratum corneum act as barriers and limit the diffusion of most drug molecules and ions. Much effort has been made to overcome this barrier and it can be seen that iontophoresis has shown a good effect. Iontophoresis represents the application of low electrical potential to increase the transport of drugs into and across the skin or tissue. Iontophoresis is a noninvasive drug delivery system, and therefore, it is a useful alternative to drug transportation by injection. In this study, we present a numerical model and effects of electrical potential on the drug diffusion in the buccal tissue and the stratum corneum. The initial numerical results are in good comparison with experimental observation. We demonstrate that the application of an applied voltage can greatly improve the efficacy of localized drug delivery as compared to diffusion alone.Item Relationship between Electromyographic Signal Amplitude and Thickness Change of the Trunk Muscles in Patients with and Without Low Back Pain(2015-09-23) Djordjevic, Olivera; Konstantinovic, Ljubica; Miljkovic, Nadica; Bijelic, Goran; MercadoObjectives: To compare the relative thickness change of the transversal abdominal (TrA) and lumbar multifidus (LM) muscles during activation in individuals with and without low back pain (LBP), and to establish a relationship between surface electromyography (sEMG) signal amplitude and the relative thickness change of the corresponding muscle during clinically relevant activity, with preferential activation of TrA/LM. Materials and Methods: Thirty-seven pain-free participants and 36 LBP patients were assessed by ultrasound for thickness changes of TrA and LM and by sEMG for changes of electrical activity of the same muscles. sEMG is done with wireless LUMBIA system. The position of the sEMG sensors and activation maneuvers were chosen carefully. Results: Significant group effect was found for relative thickness change of TrA (F 1,142 =60.69, P<0.0001) and LM (F 1,142 =36.01, P<0.0001). We found significant correlations between relative thickness change of TrA and sEMG signal amplitude on both sides for LBP (r=0.46 to 0.63, P<0.05) and pain-free patients (r=0.43-0.47, P<0.05). The correlation between LM thickness change and sEMG was significant in pain-free participants for both sides (r=0.36 to 0.38 P<0.05), and right LM in LBP participants (r=0.43, P<0.05), but not for LM in LBP group (r=0.16, P=0.351). Discussion: US and sEMG measurements can be used for objective TrA/LM assessment. Correlation results suggest that the relative change of the muscle thickness could be used as the indicator of the muscle activity. Insight into the activity of TrA/LM in pain-free individuals and LBP patients during and after painful episodes may clarify the role of functional abnormalities of these muscles in LBP.Item Remote Health-Monitoring of First Responders over TETRA Links(Institute of Electrical and Electronics Engineers Inc., 2022) Farag, Hossam; Kostic, Milos; Vujic, Aleksandar; Bijelic, Goran; Stefanovic, Cedomir; SG; MercadoIn this paper, we investigate communication performance of a system for remote health-monitoring of first responders over Terrestrial Trunked Radio (TETRA) radio links. The system features a smart garment that periodically records and sends physiological parameters of first responders to a remote agent, which processes the recordings and feeds back the health-status notifications and warnings in the form of electrotactile stimuli. The choice of TETRA as the connectivity solution is driven by its routine use by first responders, thus representing a convenient and economically-effective connectivity basis. However, the support for data communications in TETRA is limited and in practice reduced to the Short Data Service, which adversely affects the delay and failure probability of the messages exchanges in the system, as shown in the paper. Nevertheless, when the system is examined and optimized in terms of the peak Age-of-Information, a metric suitable to characterize the quasi-periodic nature of the considered monitoring process, we show that its performance becomes rather favorable, enabling timely insights into the first responders' health status.Item SixthSense: Smart Integrated Extreme Environment Health Monitor with Sensory Feedback for Enhanced Situation Awareness(Institute of Electrical and Electronics Engineers Inc., 2022) Bijelic, Goran; Iceta, Nerea Briz; Stefanovic, Cedomir; Morschhauser, Andreas; Leyenda, Ana Belen Carballo; Paletta, Lucas; Falk, Andreas; Kostic, Milos; Strbac, Matija; Jorgovanovic, Nikola; Jobst, Gerhard; Paradiso, Rita; Magenes, Giovanni; Bolado, Pablo Fanjul; Vujic, Aleksandar; Eschenbacher, Philip; Mercado; SG; SGNatural disasters occurring in inaccessible rural areas are on the rise, leading to the multiplication of first responders' missions. However, engagement in fighting wildfires or participating in rescue missions includes risks for the well-being of the engaged first responders. Consequently, a system that monitors their actions and provides real-time and actionable information without obstructing their operational capacity is needed. The EU-funded SIXTHSENSE project aims to improve the efficiency and safety of first responders' engagement in difficult environments by optimizing on-site team coordination and mission implementation. The project proposes an innovative wearable health monitoring system based on multimodal biosensor data that enables first responders to detect risk factors early on and allows real-time monitoring of all deployed responders. This paper is an introduction to the overall concept of the project, to the methodology and the system architecture, moreover details on Alpha version of SixthSense prototype are presented.Item A TETRA-Based System for Remote Health Monitoring of First Responders: Peak AoI Assessment in Direct and Trunked Mode(2023-05-15) Farag, Hossam; Vujic, Aleksandar; Kostic, Milos; Bijelic, Goran; Stefanovic, Cedomir; SG; MercadoIn this article, we study peak age of information (PAoI) performance of a novel Internet of Things (IoT) solution for remote health monitoring of first responders over terrestrial trunked radio (TETRA) links. The solution features a set of sensors embedded in a smart garment that periodically records and sends physiological parameters of first responders to a remote agent. The received data are analyzed by the remote agent, which feeds back notifications and warnings to the first responders in the form of electrotactile stimuli. The communication in the system is performed over the TETRA short data service (SDS), which is the default option for the development of third-party applications and which has rather limited capabilities. The choice of PAoI as the parameter of interest is motivated by its suitability to measure data freshness in IoT applications with periodic monitoring. We derive closed-form expressions of PAoI for different packet-management schemes allowed by the TETRA standard and verify the analytical results through extensive simulations under varying message generation rates. Our results provide important insights on the expected PAoI performance, which can be used for the system design guidelines. To the best of our knowledge, this is the first work that analyzes AoI performance of the TETRA networks.