Light‐Switchable Polymer from Cationic to Zwitterionic Form: Synthesis, Characterization, and Interactions with DNA and Bacterial Cells

Abstract

A novel cationic polymer poly(N,N-dimethyl-N-[3-(methacroylamino) propyl]-N-[2-[(2-nitrophenyl)methoxy]-2-oxo-ethyl]ammonium chloride) is synthesized by free-radical polymerization of N-[3-(dimethylamino)propyl] methacrylamide and subsequent quaternization with o-nitrobenzyl 2-chloroacetate. The photolabile o-nitrobenzyl carboxymethyl pendant moiety is transformed to the zwitterionic carboxybetaine form upon the irradiation at 365 nm. This feature is used to condense and, upon the light irradiation, to release double-strand DNA tested by gel electrophoresis and surface plasmon resonance experiments as well as to switch the antibacterial activity to non-toxic character demonstrated for Escherichia coli bacterial cells in solution and at the surface using the self-assembled monolayers.

Structures and Synthesis of Zwitterionic Polymers

“…Thus, chances are very high to obtain rather clean polyzwitterions if not the amine, but the quaternized ammonium derivative is already engaged as monomer in the polymerization. This variant has been refined recently to selectively labile ester groups such as photo-cleavable ones (Figure 10) [398,403]. Figure 10.…”

“…Figure 10. Examples for polycations that can be converted to polyzwitterions by photo-deprotection of the carboxylate group [398,403]. …”

“…Still, it must be kept in mind that responsiveness implies reversibility of the changes induced after applying a counter-stimulus. Many chemical "switching" processes, as e.g., the hydrolysis or photo-deprotection of ester groups that convert polycations into polycarboxybetaines (see Figure 10) [398,403,438,439], or polyzwitterions into polyanions [151][152][153]440], are not reversible, at least not under aqueous conditions.…”

Switchable Materials Containing Polyzwitterion Moieties

“…Recently, a photolysis of a photolabile unit for the preparation of switchable polymers poly (15) and poly (16) [51,61] was reported. Their structures are shown in Table 3.…”

“…In the poly(15) [61] switch to the polyzwitterionic state, poly(16) was enabled via the abstraction of a photolabile o-nitrobenzyl-carboxymethyl pendant during irradiation at 365 nm in PBS solution. In the polycationic state, poly(15) was able to bind double-strand DNA (dsDNS), showing the size of the DNA complex of 170 nm in solution and on a dextrane-modified surface.…”