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Network Formation of DNA/Polyelectrolyte Fibrous Aggregates Adsorbed at the Water–Air Interface
journal contribution
posted on 2019-10-18, 20:29 authored by N. S. Chirkov, A. V. Akentiev, R. A. Campbell, S.-Y. Lin, K. A. Timoshen, P. S. Vlasov, B. A. NoskovIt
is discovered that complexes of DNA and hydrophobically modified
polyelectrolytes form a rigid network of threadlike or fibrous aggregates
at the liquid–gas interface whose morphology can dramatically
affect the mechanical properties. While mixed solutions of DNA and
poly(N,N-diallyl-N,N-dimethylammonium chloride) (PDADMAC) exhibit
no notable surface activity, the complexes formed from DNA with poly(N,N-diallyl-N-butyl-N-methylammonium chloride) are surface-active, in contrast
to either of the separate components. Further, complexes of DNA and
poly(N,N-diallyl-N-hexyl-N-methylammonium chloride) (PDAHMAC) with
its longer hydrophobic side chains exhibit pronounced surface activity
with values of surface pressures up to 16 mN/m and dynamic surface
elasticity up to 58 mN/m. If the PDAHMAC nitrogen to DNA phosphate
molar ratio, N/P, is between 0.6 and 3, abrupt compression of the
adsorption layer leads unexpectedly to a noticeable decrease of the
surface elasticity. The application of imaging techniques reveals
that this effect is a consequence of the destruction of a rigid network
of threadlike DNA/polyelectrolyte aggregates at the interface. The
toroidal aggregates, which are typical for the bulk phase of DNA/PDADMAC
solutions in this range of N/P ratios, are not observed in the surface
layer. The observed link between the mechanical properties and interfacial
morphology of surface-active complexes formed from DNA with hydrophobically
modified polyelectrolytes indicates that tuning polyelectrolyte hydrophobicity
in these systems may be a means to develop their use in applications
ranging from nonviral gene-delivery vehicles to conductive nanowires.