Physical characterization and rapid prototyping of functional biomedical adhesives for membrane- and electrode-integrated cell-based lab-on-a-chip systems

Abstract

To gain progress in medicine and drug research the human body has to be understood as precise as possible. The human body is made up of various organs. Each organ has representative functional units. In regards of those units the pathology and drug uptake has to be understand. The widely spread method to either static culture cells of those functional units or conduct animal trials are quite unsatisfactory. Beside the major lack in the transferability of animal models, it is ethical questionable to conduct animal trials. Static cultivation has the disadvantage to not mimic the physiological microenvironment inside the tissue. This gap is closed by cultivating cells in a perfused lab-on-a-chip system which mimics the microenvironment of the tissue. With this technology cell are dynamically cultured with defined parameters regarding: topographical guidance, mechanical stimuli and biochemical gradients as well as cell to cell interaction, tissue to tissue interfaces, cell morphologies and biomechanics. By engineering those factors and integrating electrical sensors to enhance the read out of this microenvironment, a dynamic complex model of an organ or the functional unit of it can be created. The placenta develops during pregnancy to support the growing child with functions essential for survival, like oxygen and nutrients supply. This exchange between the maternal and the fetal blood circuit happens a the microvilli, the functional unit of the placenta. There syncytiotrophoblast are exposed to the maternal blood. The syncytiotrophoblast build up a paracellular barrier where the cells are fixed to each other by tight junctions. The placenta barrier is remodeled by creating a membrane integrated cell based lab-on-a-chip system. Here two microfluidic channels are separated by porous polyester membrane. BeWo b30 cells, derived from a human placenta choriocarcinoma are cultured on this membrane to model the placenta barrier between the maternal blood as the upper channel and the fetal blood as the lower channel. The key parameter, the tightness of the barrier, is observed by measuring the establishment oftight junctions. By integrating electrodes in the membrane integrated cell based lab-on-a-chip systemthe trans-epithelial electrical resistance can be measured during the experiment. The increase of the resistance over the epithelial membrane is directly linked to the formation of tight junctions. To conduct a proper experiment a interface is designed and tested for 4 weeks. The interface ensures an easy and leakage free connection of the chip to the lab environment. The engineering of the membrane- and electrode-integrated cell-based lab-on-a-chip system is carried out by using functional biomedical adhesives. The advantage of the pressure sensitive double-sided adhesive tapes is, that they only require a one-step manufacturing (cutting) which results in a superior short time for concept-to-chip. Pressure sensitive double-sided adhesive tapes offer rapid prototyping with in less than one hour. Because they have an already incorporated biocompatible adhesive layer they can easily bonded to glass and membranes by applying pressure. This very fast bonding procedure reduces the time for concept-to-chip radically. To choose the best pressure sensitive double-sided adhesive tape out of ARcare 92712, ARcare 90445, ARcare 90106 and ARseal 90880, the tapes are physically characterized in regards of the tolerance of the cut structures, level of barrier to vapor, hydrophilicity of the adhesive layers and the highest bonding strength to the membranes. To ensure proper cell culturing in the chip, cell compatibility as well as cell viability is studied. ARcare 90445 shows the smallest tolerance, no vapor rate, the highest hydrophilicity, the highest bonding strength to membranes and the best cell compatibility as well as as negligible influence on the cell viability. Further more the optical properties give no further restrictions. Powder blasting is conducted and used to create higher channel structures and connection holes through glass. The membrane- and electrode-integrated cell-based lab-on-a-chip system is manufactured within 3h and to proof the evidence of the lab-on-a-chip system TEER measurement with BeWo b30 cells are carried out over 7 days. The influence of the trans-epithelial electrical resistance by the cells is proven through trypsin which detaches the cells from the membrane. A functional membrane- and electrode-integrated cell-based lab-on-a-chip system is established.