Watching DNA condensation induced by poly(amido amine) dendrimers with time-resolved cryo-TEM

The condensation of DNA by poly(amido amine) dendrimers of generation 1, 2, and 4 has been followed by time-resolved cryogenic transmission electron microscopy (cryo-TEM). The recorded images show that significant morphological rearrangement occurs for DNA condensed with the lower generation dendrimers leading to the formation of toroidal aggregates. Higher charge density dendrimers, on the other hand, give rise to globular aggregates, where no transient morphologies are observed. We suggest that the dendrimers in this case are kinetically trapped as soon as they bind to the DNA strand.