In exemplary implementations, transplantation of nucleic acids into cells occurs in microfluidic chambers. The nucleic acids may be large nucleic acid molecules with more than 100 kbp. In some cases, the microfluidic chambers have only one orifice that opens to a flow channel. In some cases, flow through a microfluidic chamber temporarily ceases due to closing one or more valves. Transplantation occurs during a period in which the contents of the chambers are shielded from shear forces. Diffusion, centrifugation, suction from a vacuum channel, or dead-end loading may be used to move cells or buffers into the chambers.