Selection of easily accessible PCR-and bio-compatible materials for microfluidic chips

Conventional fabrication of microfluidic chip is a complicated and time, effort and material consuming process. Consequently, due to high expenses, it has poor applicability for performing mass biological analysis by microfluidics. In this study, we report several measures to make simple, low-cost and rapidly fabricated two-dimensional (2D) and three-dimensional (3D) microfluidic chips for biological analysis. We employed various easily accessible and polymerase chain reaction (PCR) compatibility verified materials in the process of design, patterning and bonding. Firstly, we established a simple method for evaluating the PCR compatibility of various common materials, as DNA and proteins are common components or targets in biological analysis. These materials employed in fabricating microfluidic chips, include silicon, several kinds of silicon oxide, glasses, plastics, wax, and adhesives. Two-temperature PCR was performed with these materials to determine their PCR-inhibitory effect. In most cases, the addition of bovine serum albumin (BSA) effectively improved the reaction yield. We also studied the individual PCR components from the standpoint of adsorption. Most of the materials did not inhibit the DNA, although they noticeably interacted with the polymerase. Our results provide an overview of materials that are PCR-friendly for fabricating microfluidic devices. The PCR reaction, without any additives, performed best with pyrex glass, and it performed worst with PMMA. Then, based on the results of the PCR-compatible screening test, we concentrated on fabricating microfluidic chips using easily accessible materials, such as paper and wax. We successfully shortened the whole fabrication process for complicated 2D and 3D microfluidic chips from the usual several days into several minutes by using easily accessible materials and methods. We demonstrated that these types of chips have good bio-compatibility enabling their applications in many biological analyses such as PCR and DNA capillary electrophoresis. We also dramatically simplified the process of fabricating complicated 3D chips by using cyanoacrylate-based resin or adhesive wax as the bonding material to integrate chip materials such as paper, glass slides or other polymer films. With this process, a 3D microfluidic chip is achievable by vacuating and venting the chip. And the bio-compatibility and applicability of the paper-based 3D microfluidic chip was verified in the applications such as PCR, HeLa cell electroporation and the chemotaxis of E. coli. In all, our PCR-compatibility test provides good hints as to the selection of materials for microfluidic chips employed in biological analysis. Base on this, we succeeded in fabricating complicated microfluidic chips using easily accessible materials that may make it much more applicable than conventional methods.