Microoxygraph Device for Biosensoristic Applications

Oxygen consumption rate (OCR) is a significant parameter helpful to determine in vitro respiratory efficiency of living cells. Oxygen is an excellent oxidant and its electrocatalytic reduction on a noble metal allows accurately detecting it. By means of microfabrication technologies, handy, low-cost, and disposable chip can be attained, minimizing working volumes and improving sensitivity and response time. In this respect, here is presented a microoxygraph device (MOD), based on Clark’s electrode principle, displaying many advantageous features in comparison to other systems. This lab-on-chip platform is composed of a three-microelectrode detector equipped with a microgrooved electrochemical cell, sealed with a polymeric reaction chamber. Au working/counter electrodes and Ag/AgCl reference electrode were fabricated on a glass slide. A microchannel was realized by photoresist lift-off technique and a polydimethylsiloxane (PDMS) nanoporous film was integrated as oxygen permeable membrane (OPM) between the probe and the microreaction chamber. Electrochemical measurements showed good reproducibility and average response time, assessed by periodic injection and suction of a reducing agent. OCR measurements on 3T3 cells, subjected, in real time, to chemical stress on the respiratory chain, were able to show that this chip allows performing consistent metabolic analysis

MPC for tracking with optimal closed-loop performance

Abstract-This paper deals with the tracking problem for constrained linear systems using a model predictive control (MPC) law. As it is well known, MPC provides a control law suitable for regulating a constrained linear system to a given target steady state. Asymptotic stability and constraint fulfilment for any finite prediction horizon is typically ensured by means of a suitable choice of the terminal cost and constraint. However, when the target operating point changes, the feasibility of the controller may be lost and the controller fails to track the reference. Recently, a novel MPC formulation has been proposed to solve this problem, ensuring feasibility and asymptotic convergence to any admissible steady state. On the other hand, this control law can not ensure the local optimality of the proposed controller, which is a desirable property of predictive controllers. In this paper, this controller is extended considering a generalized offset cost function. Sufficient conditions on this function are given to ensure the local optimality property. Besides, this novel formulation allows to consider as target operation points, states which may be not equilibrium points of the linear systems. In this case, it is proved in this paper that the proposed control law steers the system to an admissible steady state (different to the target) which is optimal with relation to the offset cost function. Thanks to the proposed generalization, the offset cost function could be chosen according to some steady performance criterium. Therefore, the proposed controller for tracking achieves an optimal closed-loop performance during the transient as well as an optimal steady state in case of not admissible target. These properties are illustrated in an example

Aneurysms and pseudoaneurysms in dialysis access

Aneurysms are a common and often difficult complication seen with arteriovenous vascular access for haemodialysis. The purpose of this narrative review is to define and describe the scale of the problem and suggested therapeutic strategies. A narrative review of the published literature illustrated by individual cases is presented with the aim of summarising the relevant literature. The definitions of aneurysm are inconsistent throughout the literature and therefore systematic review is impossible. They vary from qualitative descriptions to quantitative definitions using absolute size, relative size and also size plus characteristics. The incidence and aetiology are also ill defined but separation into true aneurysms and false, or pseudoaneurysms may be helpful in planning treatment, which may be conservative, surgical or radiological. The lack of useful definitions and classification along with the multitude of management strategies proposed make firm evidence based conclusions difficult to draw. Further robust well designed studies are required to define best practice for this common problem

Liver Support Systems

Liver insufficiency is a dramatic syndrome, with multiple organ involvement. A multiplicity of toxic substances (hydrophilic like ammonia and lipophylic like bilirubin or bile acids or mercaptans) are released into the systemic circulation, thus altering many enzymatic cellular processes. The patient\u2019s death while on the transplantation waiting list is frequent, because of organ scarcity. Systems to support liver function may be useful to avoid further complications due to the typical toxic state, \u201cbridging\u201d the patients to the transplantation, or, in the event of an acute decompensation of a chronic liver disease, sustain liver function long enough to permit organ\u2019s regeneration and functional recovery. An ideal liver support system should substitute the main functions of the liver (detoxification, synthesis and regulation). Extracorporeal systems now available may be totally artificial or bio-artificial. While the first are only able to perform detoxification, the second may add the functions of synthesis (plasma proteins, coagulation factors \u2026) and regulation (neurotransmitters). Bioartificial liver working with isolated hepatocytes and a synthetic membrane in an extracorporeal system, are however still far from being ready for clinical use. At present, liver insufficiency may be treated with an extracorporeal support technology aimed either to detoxification alone or to a real purification. Charcoal hemoperfusion or exchange/absorption resins may be used for blood detoxification. Blood or plasma-exchange, from a theoretical point of view, could be suited for a polyvalent intoxication, as liver failure is; however, the multi-compartmental distribution of some solutes largely endangers the efficacy of these procedures. Selective plasmapheresis techniques are now available for some solutes (e.g. styrene for bilirubin) and may progressively reduce the plasma levels and presumably the deposits of the solute. Novel treatments introduced to improve detoxification, mainly of the protein-bound substances, are the molecular adsorbent recirculation system system (MARS) and Prometheus systems. MARS performs an albumin dialysis, where albumin is the exogenous carrier for the toxic substances, and different experiences have proved its efficacy mainly in the treatment of hepatic encephalopathy, while data on survival are still limited to small case series. With Prometheus, the most recent system developed for a wide detoxification, albumin-bound toxins are directly removed in two separate cartridges with different solute affinity, without the need for exogenous albumin; plasmadsorption is then coupled with a real dialysis process. After initial, promising results, the efficacy of Prometheus in the patients hard end-points will be evaluated in a large international trial. On the whole, liver support systems may offer, in many cases, a survival benefit. Stem cells are however, even in this filed, the real, great hope for the future of patients with end-stage liver disease

Liver support systems

none4Liver insufficiency is a dramatic syndrome, with multiple organ involvement. A multiplicity of toxic substances (hydrophilic like ammonia and lipophylic like bilirubin or bile acids or mercaptans) are released into the systemic circulation, thus altering many enzymatic cellular processes. The patient’s death while on the transplantation waiting list is frequent, because of organ scarcity. Systems to support liver function may be useful to avoid further complications due to the typical toxic state, “bridging” the patients to the transplantation, or, in the event of an acute decompensation of a chronic liver disease, sustain liver function long enough to permit organ’s regeneration and functional recovery. An ideal liver support system should substitute the main functions of the liver (detoxification, synthesis and regulation). Extracorporeal systems now available may be totally artificial or bio-artificial. While the first are only able to perform detoxification, the second may add the functions of synthesis (plasma proteins, coagulation factors …) and regulation (neurotransmitters). Bioartificial liver working with isolated hepatocytes and a synthetic membrane in an extracorporeal system, are however still far from being ready for clinical use. At present, liver insufficiency may be treated with an extracorporeal support technology aimed either to detoxification alone or to a real purification. Charcoal hemoperfusion or exchange/absorption resins may be used for blood detoxification. Blood or plasma-exchange, from a theoretical point of view, could be suited for a polyvalent intoxication, as liver failure is; however, the multi-compartmental distribution of some solutes largely endangers the efficacy of these procedures. Selective plasmapheresis techniques are now available for some solutes (e.g. styrene for bilirubin) and may progressively reduce the plasma levels and presumably the deposits of the solute. Novel treatments introduced to improve detoxification, mainly of the protein-bound substances, are the molecular adsorbent recirculation system system (MARS) and Prometheus systems. MARS performs an albumin dialysis, where albumin is the exogenous carrier for the toxic substances, and different experiences have proved its efficacy mainly in the treatment of hepatic encephalopathy, while data on survival are still limited to small case series. With Prometheus, the most recent system developed for a wide detoxification, albumin-bound toxins are directly removed in two separate cartridges with different solute affinity, without the need for exogenous albumin; plasmadsorption is then coupled with a real dialysis process. After initial, promising results, the efficacy of Prometheus in the patients hard end-points will be evaluated in a large international trial. On the whole, liver support systems may offer, in many cases, a survival benefit. Stem cells are however, even in this filed, the real, great hope for the future of patients with end-stage liver disease.noneSantoro A.; Mancini E.; Ferramosca E.; Faenza S.Santoro A.; Mancini E.; Ferramosca E.; Faenza S

Coronary artery calcium screening : implications for clinical practice

Cardiovascular disease is the most common cause of death in the Western hemisphere, and in the majority of cases the event announcing the presence of atherosclerosis is either sudden death or a disabling myocardial infarction or stroke. Although traditional risk factors are present in most individuals suffering a cardiovascular event, the prognostic ability of risk factors to predict events in the short term is limited. The focus of research has therefore turned to the application of noninvasive modalities to image the atherosclerotic plaque in its preclinical stages. Measurements of coronary artery calcium serve as a quantitative reflection of the severity of coronary artery disease, and greater calcium burdens correlate with more advanced disease. Coronary artery calcium has been shown in several studies to add prognostic value to traditional risk factors in patients at intermediate risk, and in this group of patients it may be cost effective. There is, however, an inherent danger in raising the cost of care by increasing downstream unnecessary testing if such screening were to be applied to low-risk individuals. This article is a systematic review of the most relevant literature regarding the utilization of coronary artery calcium screening as a tool to refine risk assessment and to evaluate the efficacy of therapy for atherosclerosis