Controlled Layer-By-Layer Polymer/DNA Coating of Carbon Nanotubes for Gene Delivery Applications

Considering the growing attention toward gene delivery, different vectors have been developed; viral and non-viral. Although viral vectors have shown higher DNA transfection efficacies, but features such as their complicated preparation procedure, the risk of being immunogenic, and their limited capacity for gene transfer, has led scientists to think about non-viral carriers. Using nanoparticles as genetic carriers introduced a new era in this field. Due to their ease of functionalization, less toxicity, and higher capacity, nanoparticles are now considered as suitable carriers for gene delivery. Moreover, one-dimensional nanomaterials have proved to have better cell internalization. As an interesting method to form or manipulate polymeric nanoparticles, we have recently developed microfluidic devices for having adjustable and uniform particles at nanoscale. Applying variable central and lateral flows, the resulted particles can be tuned as our desires.  In the present work, we have used short length carbon nanotubes (CNTs) as our carrier due to its needle like structure that makes it suitable for cell internalization. Then it is coated it in a layer-by-layer procedure, through sequentional microfluidic platform, with Chitosan (decorate CNT with positive charges), plasmid DNA, and again Chitosan (protect DNA and provide positive charges). The first chitosan layer balances the charge for better DNA interaction, performed in the first micromixer, and the final chitosan coat, which is done in the third micromixer, tunes the charge for better cell internalization. The results confirm the ability of our microfluidic systems to finely tune the coating thickness (in each step), DNA loading content, and the overall charge of these vectors which can affect the protein expression of target cells.