Influence of Satellite Groups on Telechelic Antimicrobial Functions of Polyoxazolines

Abstract

The antimicrobial activity of poly(alkyloxazoline) telechelics with one quaternary N,N-dimethyldodecylammonium (DDA) end group was found to be greatly controlled by the non-bioactive distal end group, the so-called satellite group. In systematic investigations, the nature of the latter groups was varied to explore the mechanism of the satellite effect. To this end, poly(2-alkyl-1,3-oxazoline)s (alkyl = ethyl, methyl) with a DDA-group at the terminating end and varying alkyl, aminoalkyl, and polyphenyloxazoline block satellite groups, have been synthesized. Poly(oxazoline) derivatives with polydispersity indices of 1.06-1.20 and molecular weights from 2,200 to 12,800 g . mol(-1) could be obtained. The macromolecular structures have been confirmed by NMR spectroscopy and ESI-MS measurements. The polymers were investigated with regard to their antibacterial efficiency towards the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli. It was found that the introduction of alkyl chain satellites of 4-10 carbon atoms in length afforded antimicrobial activity of the polymers against both microbes that was about 2-3 times higher than that of the well-known structurally comparable low molecular weight biocide, dodecyltrimethylammonium chloride (DTAC). Based on the antimicrobial effects of the investigated polymers, a mechanism for the satellite effect was proposed.

Antimicrobial Polymers in Solution and on Surfaces: Overview and Functional Principles

“…Further, a similar derivative containing polyethylene glycol (PEG) showed a 5-10 times lower antimicrobial activity compared to the polyoxazolines. Interestingly, the group distal to the biocide, the so-called satellite group, controls the activity of the whole molecule in a range of 3 orders of magnitude [52]. We propose that this effect is due to the amphipatic behaviour of the macromolecules, i.e., they form unimolecular micelles in solutions and refold at the surface of microbial cell membranes.…”

Design Strategies for Functionalized Poly(2-oxazoline)s and Derived Materials

“…In case of the hexadecyl satellite group, the penetration of the DDA (N,N-dimethyldodecylammonium) functionality is prevented. Tiller et al examined the great influence of the satellite groups on the antimicrobial activity of poly(2-oxazoline)s in an expanded study [44] (Scheme 2). pMeOx, pEtOx, and the corresponding block copolymers with pPhOx with varying satellite groups and a dimethyl-n-dodecylammonium end-group were synthesized and their antibacterial activities against Staphylococcus aureus and Escherichia coli were examined.…”

“…Scheme 2. Structural formula of telechelic pMeOx exhibiting antimicrobial activity (for details, see reference [44] [50]. These homo poly(2-oxazoline)s were used for click-reactions applied onto azide-terminated silicon substrates using microwave irradiation [51].…”

Poly(2‐oxazoline)s: Alive and Kicking

“…Other recent studies on structure-property relationships in poly(2-oxazoline)s include their use as compatibilizer, [19] their lower critical solution temperature (LCST), [20,21] micellization behavior, [22] as well as antimicrobial properties. [23,24] However, the generally long polymerization times for 2-oxazolines that range from days to weeks [25,26] represent a major disadvantage that obstructs fast synthesis and screening of libraries of poly(2-oxazoline)s. Therefore, the use of microwave irradiation has been investigated as an alternative heat source for the polymerization of 2-oxazolines. The use of dielectric heating has already resulted in faster and cleaner reactions in a variety of organic syntheses because of the fast and homogeneous noncontact heating, whereby the use of closed reaction conditions provides easy access to high-temperature conditions.…”