High-throughput intracellular delivery of proteins and plasmids
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Intracellular delivery of macromolecules is crucial for the success of many research and clinical applications. Several conventional intracellular delivery methods have been used for many years but are still inadequate for several applications because of the issues associated with toxicity, low-throughput, and/or difficulty to target certain cell types. In this study, we developed and evaluated new high-throughput intracellular delivery methods for the efficient delivery of macromolecules while maintaining high cell viability. First, we studied the feasibility of using an array of nanoneedles, with sharp tip diameters in the range of tens of nanometers, to physically make transient holes in cell membranes for intracellular delivery. Puncture loading and centrifuge loading methods were developed and assessed for the effect of various experimental parameters on cell viability and delivery efficiency of fluorescent molecules. In both methods, high-throughput intracellular delivery was feasible by creating transient holes in cell membranes with the sharp tips of the nanoneedles. The second physical intracellular delivery method we studied was a novel microfluidic device that created transient holes in the cell membrane by mechanical deformation and shear stress to the cell. We observed efficient delivery of fluorescent molecules and studied the effect of device design and flow pressure on the delivery efficiency compared to data in the literature. We accounted for cell loss and clogging in the microfluidic devices and determined the true loss of cell viability associated with this method. Lastly, we investigated the possibility of intracellular delivery using nanoparticles on a leukemia cell line. Among number of materials for nanoparticles tested, mesoporous silica/poly-L-lysine nanoparticles were selected for further intracellular delivery study based on cell viability and intracellular delivery capability. We demonstrated the co-delivery of protein and plasmid by encapsulating into and coating onto the surface of the nanoparticles, respectively, which would be advantageous for certain therapeutic strategies. In summary, this work introduced two new intracellular delivery methods involving nanoneedles and novel nanoparticles, and provided an early, independent assessment of microfluidic delivery, showing the strengths and weaknesses of each method. These methods can be further optimized for a number of laboratory and clinical applications with continued research.