(39f) Endothelial Cell Culture in a Ceramic Microfluidic Device
Microfluidic devices possess many qualities that make them attractive to research. First, their small dimensions make it possible to carry out reactions and other processes with a minimal amount of starting materials and waste. This makes them potentially useful for screening compounds in the pharmaceutical industry or evaluating reactions on a small scale. Their compact dimensions also make it possible to create self-contained devices that can be portable enough for fieldwork or implantable in the human body as a sensor. Another important characteristic of these devices is that the channel size can be fabricated to mimic vascular and cellular dimensions. The size of a capillary in the human body ranges from 5-10 um. This fits within the range of conditions able to be replicated by microfluidics. By recreating the conditions within the body, such as pressure and sheer stress, one could more accurately model the natural environment for cells or other tissue. A cell in its native environment could have a significantly different response to stimulus than a cell grown in a cell culture flask and static solution.
To date, microfluidic devices have been fabricated almost exclusively from two materials: Polydimethylsiloxane (PDMS) and glass. Glass has the disadvantage of requiring extremely hazardous hydrofluoric acid to etch the channels. PDMS also has some less desirable properties. For instance, its flexible structure gives the fabrication an inherent lack of reproducibility and durability, which would preclude its use in the field or as an implantable device in the body. To take microfluidics from an interesting research subject to a commercial product will require a durable, rigid, uniform substrate with a high precision, reproducible fabrication technique. In addition, the substrate needs to be suitable for some type of analytical measurement technique, primarily optical or electronic. Low temperature co-fired ceramic (LTCC) materials and processing methods meet these criteria.
The goal of the current study is to show that LTCC materials can be used to construct a microfluidic device containing a viable cell cultures grown on gold electrodes. This device will incorporate trans-endothelial electrical resistance (TEER) measurements allowing potential applications in flow based cell culture studies and cell based sensors. To facilitate the binding of cells to the gold electrodes, a self-assembled monolayer (SAM) was formed on the surface of a gold printed LTCC chip. RGDS peptide, which is known to mediate HUVEC binding, was linked to the SAM using a carbonyldiimidizole (CDI) reaction. Human umbilical vein endothelial cells (HUVECs) were then seeded onto the surface of the electrode. Initial results suggest that it is possible to bind HUVEC cells to gold electrodes selectively over the LTCC substrate. This binding and selectivity may be able to be optimized through careful selection of conjugation solvents as well as an agitation step post-seeding to remove cells non-specifically bound to the LTCC. In the near future, this method will be implemented to achieve a microfluidic device containing a viable cell culture.