Long-term normothermic machine preservation of human livers: What is needed to succeed?

While short-term machine perfusion (≤24 h) allows for resuscitation and viability assessment of high-risk donor livers, the donor organ shortage might be further remedied by long-term perfusion machines. Extended preservation of injured donor livers may allow reconditioning, repair and regeneration. This review summarizes the necessary requirements and challenges for long-term liver machine preservation, which requires integrating multiple core physiological functions to mimic the physiological environment inside the body. A pump simulates the heart in the perfusion system, including automatically controlled adjustment of flow and pressure settings. Oxygenation and ventilation are required to account for the absence of the lungs, combined with continuous blood gas analysis. To avoid pressure necrosis and achieve heterogenic tissue perfusion during preservation, diaphragm movement should be simulated. An artificial kidney is required to remove waste products and control the perfusion solution's composition. The perfusate requires an oxygen carrier, but will also be challenged by coagulation and activation of the immune system. The role of the pancreas can be mimicked through closed-loop control of glucose concentrations by automatic injection of insulin or glucagon. Nutrients and bile salts, generally transported from the intestine to the liver, have to be supplemented when preserving livers long-term. Especially for long-term perfusion, the container should allow maintenance of sterility. In summary, the main challenge to develop a long-term perfusion machine is to maintain the liver's homeostasis in a sterile, carefully controlled environment. Long-term machine preservation of human livers may allow organ regeneration and repair, thereby ultimately solving the shortage of donor livers.

Control system for glucose level regulation in peritoneal dialysis

Kidney failure leads to the serious health issues associated with abnormal water-salt balance. In this case, peritoneal dialysis therapy is often prescribed: 1-2 liters of dialysis solution is administered in peritoneal cavity for 3-4 hours. During this time, due to diffusion and osmosis, toxins and excess water are transferred from blood to solution. One of the method’s downsides is the transition of glucose (osmotic agent) into the bloodstream, which leads to a gradual decrease in the fluid removal rate. To mitigate this problem, one must use the system, which will measure current glucose concentration and inject glucose into solution to compensate absorption. The paper proposes such a control system for automatic regulation of the glucose concentration in peritoneal dialysate solution. Its structure, elements, their functions and characteristics are discussed. Proposed system is capable to work autonomously or can be incorporated into wearable “artificial kidney” device.

IR-Photometry Method for Measuring Glucose Concentration in Peritoneal Dialysis Fluid

Introduction. The transition of glucose into the blood during automated peritoneal dialysis with regeneration of the dialysis fluid leads to a decreased removal of excess fluid from the body and corresponding violations of the water-salt balance.Aim. To consider a system for automatically maintaining the concentration of glucose in the dialysate solution, which provides effective ultrafiltration, as well as to propose a non-contact photometric feedback sensor.Materials and methods. The sensor is an optical system of an IR laser diode with a power of 30 mW and a wavelength of 1600 nm, a photodiode and a quartz tube, through which the test solution circulates. The sensor measures the attenuation of the radiation passing through the solution in a pulsed mode and calculates the glucose concentration. The selected combination of digital filters provides compensation for the noise of the optical system. Experimental studies of the efficiency of the sensor were carried out on peritoneal dialysis solutions with various concentrations of urea, creatinine, uric acid and glucose. At the beginning of the experiments, the sensor was calibrated in a pure solution.Results. It was shown that the developed sensor makes it possible to measure the concentration of glucose in a solution for peritoneal dialysis in the range of 42…220 mmol / l with a relative error of about 15%. The time of one measurement is about 1 minute, which makes it possible to obtain up-to-date information on the current concentration of the solution.Conclusion. This combination of characteristics will allow the sensor to be used in artificial kidney wearable devices for assessing the glucose content in the solution, calculating the time to change the solution and as a feedback sensor in a system for maintaining the concentration of the osmotic agent.

The Use of Polymeric Materials in Modern Dentistry

The achievements and discoveries of chemical science have firmly established themselves in all branches of humanity. One of the most significant chemistry possibilities is the polymerization and polycondensation of compounds, which, in turn, are methods for producing polymers. Polymers are high molecular weight compounds consisting of many units (monomers) linked by chemical bonds. Unique polymer compounds are the basis of plastics, chemical fibers, rubber, paints, and varnishes, adhesives [8]. Polymers are used for the manufacture of removable prostheses, materials for fillings and inlays, orthodontic appliances, artificial teeth, dental implants, as well as in the creation of artificial heart valves, artificial kidney devices, artificial circulation, artificial heart [6].