Abstract
Hydrogel microparticles were copolymerized with surface-immobilized DNA. Particles derived from a microfluidic device and particles derived from mechanical homogenization were compared. The hypothesis was tested that a controlled droplet generation mechanism would produce more homogeneous particles. Surprisingly, the DNA content of both particle types was similarly inhomogeneous. To make this test possible, a simple, low cost, and rapid method was developed to fabricate a microfluidic chip for droplet generation and in-line polymerization. This method used a low-cost laser cutter ($400) and direct heat bonding (no adhesives or intermediate layers). The flow focusing droplet generator produced droplets and hydrogel particles 10–200 μm in diameter.
Highlights
We used a low-cost microfluidic technique to test whether mechanical homogenization is responsible for inhomogeneous partitioning of cholesterol-modified DNA into droplets
We developed a method for generating microfluidic chips that is simple and inexpensive and may find use elsewhere
We present a low-cost microfluidic fabrication, reliable bonding without a bonding layer or adhesive, microfluidic droplet generation, and in situ polymerization to generate particles coated with DNA
Summary
We used a low-cost microfluidic technique to test whether mechanical homogenization is responsible for inhomogeneous partitioning of cholesterol-modified DNA into droplets. We found that mechanical homogenization and microfluidic droplet generation methods produce significant inhomogeneity in the DNA contents of the droplets. The similarity between the two results suggests that amphiphilic molecules dispersed into droplets may be partitioned unevenly irrespective of the droplet formation mechanism This fact should be considered in future applications of droplet microfluidics and analytical methods based on water dispersed in oil. To test this hypothesis, we required a microfluidic chip so that we could observe and control droplet generation and confirm a single step mechanism. Several low-cost approaches have been demonstrated to fabricate devices for droplet microfluidics. For a comparison of this method in approximate cost and features, see Table 1
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