bm7b01313_si_001.pdf (1.64 MB)
Controlling Enzymatic Polymerization from Surfaces with Switchable Bioaffinity
journal contribution
posted on 2017-10-31, 00:00 authored by Mohammad Divandari, Jonas Pollard, Ella Dehghani, Nico Bruns, Edmondo M. BenettiThe affinity of surfaces
toward proteins is found to be a key parameter
to govern the synthesis of polymer brushes by surface-initiated biocatalytic
atom transfer radical polymerization (SI-bioATRP). While the “ATRPase”
hemoglobin (Hb) stimulates only a relatively slow growth of protein
repellent brushes, the synthesis of thermoresponsive grafts can be
regulated by switching the polymer’s attraction toward proteins
across its lower critical solution temperature (LCST). Poly(N-isopropylacrylamide) (PNIPAM) brushes are synthesized
in discrete steps of thickness at temperatures above LCST, while the
biocatalyst layer is refreshed at T < LCST. Multistep
surface-initiated biocatalytic ATRP demonstrates a high degree of
control, results in high chain end group fidelity and enables the
synthesis of multiblock copolymer brushes under fully aqueous conditions.
The activity of Hb can be further modulated by tuning the accessibility
of the heme pocket within the protein. Hence, the multistep polymerization
is accelerated at acid pH, where the enzyme undergoes a transition
from its native to a molten globule conformation. The controlled synthesis
of polymer brushes by multistep SI-bioATRP highlights how a biocatalytic
synthesis of grafted polymer films can be precisely controlled through
the modulation of the polymer’s interfacial physicochemical
properties, in particular of the affinity of the surface toward proteins.
This is not only of importance to gain a predictive understanding
of surface-confined enzymatic polymerizations, but also represents
a new way to translate bioadhesion into a controlled functionalization
of materials.