Projekt wyznaczania tribologicznych parametrów komórek chrząstki stawowej w inteligentnych bioreaktorach

Tematem badań jest optymalizacja hodowli chrząstki stawowej pod kątem tribologicznym poprzez sterowanie różnymi parametrami przepływu, np. ciśnieniem, prędkością przepływu, drganiami, wartościami sił tarcia, które powstają w trakcie opływu komórek cieczą biologiczną w bioreaktorze. W celu weryfikacji przeprowadzanej optymalizacji planuje się zbudowanie prototypu minibioreaktora. W niniejszej pracy przedstawiony zostanie opis modelu przepływu cieczy lepkiej w warstwie granicznej oraz przepływu potencjalnego przy uwzględnieniu warunków brzegowych dla prędkości płynów biologicznych w warstwie przyściennej hodowanych chondrocytów, jak również preparatów tkankowych chrząstki stawowej. Uzyskane wartości sił tarcia na drodze analityczno-numerycznej są w trakcie badań porównywane z wartościami sił tarcia pomierzonymi mikroskopem sił atomowych. Wyniki analityczno-numeryczne uzyskane będą współczesnymi metodami hydromechaniki w zakresie cienkich warstw granicznych, a także metodami hydrosprężystości i hipersprężystości w obszarach warstw wierzchnich opływanych miękkich tkanek.

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The topic of presented research are the tribological aspects of optimization of human joint cultivation using the control tools to make changes of various flow parameters such as pressure, flow velocity, vibrations, forces of friction values, which are generated during the flow of biological liquids around the cells in bioreactor. For this matter the building of mini-bioreactor prototype is provided. The model of viscous liquid flow in boundary layer and potential flow will be determined using the hydrodynamic equation with boundary conditions for bio-liquids formulated near to the cells as well near to the tissue samples of cartilage joint. During the analytical and numerical examinations will be determined flow velocity field sof visco-elastic, non Newtonian, nutrient, biological fluids and friction forces generated during the cultivation process near to the cell surfaces. Additional will be considered potential flows of the joint liquids which feeds cartilage joint after transplantation. The values of friction forces obtained on the analytical and numerical way will be compared with the values of friction forces measured by means of the microscope of atomic forces. Analytical and numerical results will be obtained by means of contemporary methods of hydrodynamic of thin layer as well of the hydro-elasticity and hyper-elasticity methods of soft tissues. The core of the presented problem is to numerically and experimentally determine or to indicate values of optimum pressure and liquid velocity values appearing near the cells and to find ways of controlling the friction forces between biological particles of nutrient or pharmacological liquid and cell body in the thin boundary layer. Investigations of the physical and strength features are expected to the performed for various kinds of human joint cartilage, namely sound and pathological cartilages at different human age. To start treating surface structure of chondrocytes and joint cartilage it is absolutely necessary to have at one's disposal at proper model of liquid flow in the thin layer and to obtain the proper values of friction forces. As more and more young people suffer damages of joint cartilage, it is necessary to make an attempt to regenerate the lesions of the human joint. Such treatments have been so far performed by applying the chondrocytes transplantation. In the future, transplantation of all cartilage parts cultivated in advance in bioreactor, and either reproduction or renewal of a part of cartilage inside the living joint is expected. To perform such transplantations in a large scale it is necessary to acquire the knowledge on the realization and modification of the cultivation process, and -simultaneously-on ways for decreasing production costs of chondrocytes. Optimization of the flow parameters and adjustment of the liquid flow to transplanted cartilage kind, is of an influence on successful performance of a transplantation. The aim of the performed research is to elaborate proper flow models for cell cultivation in bioreactor, and proper flow models of lubrication in human joint gap. In such investigations it is necessary to validate and verify the presented analytical and numerical flow models. Therefore the building of bioreactor prototype is provided for to make it possible to measure some material parameters. Non- invasive methods of determining friction forces and controlling their values during lubrication of cells on the superficial layer of human joint cartilage can effectively help disclosing the early abrasive wear of cartilage joint and monitoring the osteoporosis development. This fact motivates to performed the investigations in question as the knowledge on friction forces in human joints and control methods of the forces can provide the information necessary for conducting prophylaxis and therapy. The flow parameters of nutrient liquid in bioreactor have a great importance for the development of chondrocytes and their quality. The process of cultivation of chondrocytes is more difficult than that of other cells. This fact first of all results from an applied method of nourishment of cells. In many scientific centers the nutrient liquid is delivered to the bioreactor by changeable pressure impulses. According to the author's knowledge, during the cultivation one should apply optimum flow parameters, i.e. optimum values of pressure, liquid velocity and friction forces. Determination of friction forces and strategy of their control during the cells cultivation in bioreactors and regeneration of human joint cartilage has a great influence on the choice and observation of optimum friction forces for a given cultivated cartilage and graft. The described research is very sensible because the friction forces j on nano- level, which arise during the nutrient liquid flow round the cells, have great influence on their recreation and growth in bioreactor and on graft functioning. The presented research provides an important impact for developing the new scientific domain such as cyto-tribology, histo-tribology or tribology of cells and tissue. According to the author's knowledge such scientific domains are completely new have been not so far initiated by any scientific centre and in any area of tribology and tissue engineering. To develop such scientific domains the knowledge is demanded not only in the field of tissue engineering but also in nano-tribology, and thin layer hydrodynamic. Also, such research devices such as incubators, bioreactors and atomic force microscopes are necessary to measure geometrical surface structures of as small dimensions as 20 žm x 20 žm and friction forces of the order of žN, which arise on such small surfaces. The gained experience in analytical, numerical and experimental determining the distributions of steady and unsteady flow velocity of nutrient liquid, pressure, capacities, friction forces, friction coefficients, wear in the thin layer around the cells cultivated in bioreactors and in the thin boundary layer lubricating human joints, permits to apply this knowledge to determine - with the use of analogous methods - the similar parameters but concerning in mechanical devices, for example slide journal bearings. The most excellent slide bearings are those biological in the aspects of their material and constructions. Such bearings are shaped by the nature over many thousand years of evolution. Lubricating liquids in bio-bearings change their viscosities under external impulses. Bio bearings (bio-joints) can adjust themselves to existing external conditions. The facts inspire to seek materials of similar properties for the machinery bearings and to develop intelligent designs and materials, which could change their features during operation and adjust themselves to external working conditions. It can be stated, that bioreactors, cultivation of cells, bio-joints and bio-bearings create future call for production of self- regenerating mechanisms and machinery bearings capable of adjusting themselves to existing external and environmental working conditions. It very rarely happens that the experiences gained during development process of machinery bearings can be transferred to the construction of bio-joints.