Microfluidic Probe for Direct Write of Soft Cell Scaffolds.

摘要

3D cell cultures replicate the in-vivo physiology much more accurately than 2D cell cultures; but it remains challenging to recreate the 3D in-vivo tissue architecture of soft tissues in-vitro. Different methods have been developed to print cell scaffolds in 3 dimensions, the two most popular being inkjet printing and direct extrusion. Extrusion is promising because 3D structures can be written directly; however, they incur a high shear stress, which was shown to damage or even kill cells.;We have designed and fabricated a novel microfluidic probe (MFP) and developed a direct write method to dispense alginate fibers seeded with cells and to construct a 3D cell scaffold. This system allows for low shear stress deposition of cells inside of a fiber onto the surface because a liquid is used, which gelates only after extrusion while still being surrounded by an ensheathing liquid. The MFP comprises two main intersecting microchannels, one for the alginate precursor solution and one for the sheath flow of calcium chloride, which triggers the gelation of the alginate. The main branching point is designed so as to ensheath the alginate solution, which solidifies into a fiber. The diameter of this fiber can be tuned in diameters of around 100 μm before exiting through the nozzle of the device. We further devised a declogging mechanism that was required for practical applications of the MFP. A declogging microchannel was added connected to a chelating agent, that could be flowed and lead to the dissolution of any alginate gelated inside of the probe. Throughout this project, i) different probe designs were considered and tested, ii) different fabrication methods were examined and used to fabricate the different probes, iii) the fiber dimensions were measured and characterized as a function of the liquid flow rates, iv) different parameter of the probe, and v) liquid were examined to reduce curl formation during direct writing, vi) glass substrate was surface coated to optimize the binding of the fibers onto the surface, vii) and multiple layers of fiber were deposited onto the glass substrate. Finally cell viability was optimized and cells were loaded directly within 3D scaffolds and shown to grow.