Claudia Mattheis

Effect of Guanidinylation on the Properties of Poly(2-aminoethylmethacrylate)-Based Antibacterial Materials

The effect of converting ammonium into guanidine moieties, compared to other factors such as molecular weight or hydrophobicity, on the antibacterial activity is investigated for homo- and copolymers of 2-aminoethylmethacrylate in solution or coatings. Polymers are obtained by free radical polymerization, polymer-analogous guanidinylation is conducted with cyanamide; non-leaching immobilization is achieved by LBL assembly of homopolymers or crosslinking of functional sidegroups in copolymers. Antibacterial activity to Escherichia coli or Bacillus subtilis is determined by different standard methods. Guanidinylation improves antibacterial activity and speed as well as cytotoxicity of hydrophilic homo- and copolymers in solution or coatings.

Closing One of the Last Gaps in Polyionene Compositions: Alkyloxyethylammonium Ionenes as Fast-Acting Biocides

Alkyloxyethylammonium ionenes are reported as biocompatible biocides with a time of biocidal action within a few minutes. The presence of both ethoxyethyl and aliphatic spacers besides long alkyl chain substituents on the quaternary nitrogen atom differentiates these biocides structurally from the known polyionenes. The influence of alkyl spacer length, counter ion and length of the pendant alkyl groups on the antibacterial properties is studied. E. coli is adopted as a test organism. MIC and MBC values are determined via broth dilution methods; time-dependent tests are accomplished by determining the number of viable cells with the spread-plate method after different contact times. Structural characterization is conducted via NMR and mass spectrometry techniques.

Antimicrobial Hydantoin-grafted Poly(ε-caprolactone) by Ring-opening Polymerization and Click Chemistry

Novel degradable and antibacterial polycaprolactone-based polymers are reported in this work. The polyesters with pendent propargyl groups are successfully prepared by ring-opening polymerization and subsequently used to graft antibacterial hydantoin moieties via click chemistry by a copper(I)-catalyzed azide-alkyne cycloaddition reaction. The well-controlled chemical structures of the grafted copolymers and its precursors are verified by FT-IR spectroscopy, NMR spectroscopy, and GPC characterizations. According to the DSC and XRD results, the polymorphisms of these grafted copolymers are mostly changed from semicrystalline to amorphous depending on the amount of grafted hydantoin. Antibacterial assays are carried out with Bacillus subtilis and two strains of Escherichia coli and show fast antibacterial action.

Antimicrobial Hydantoin-Containing Polyesters

A new N-hydantoin-containing biocompatible and enzymatically degradable polyester with antibacterial properties is presented. Different polyesters of dimethyl succinate, 1,4-butanediol, and 3-[N,N-di(β-hydroxyethyl)aminoethyl]-5,5-dimethylhydantoin in varying molar ratios are prepared via two-step melt polycondensation. The antibacterially active N-halamine form is obtained by subsequent chlorination of the polyesters with sodium hypochlorite. Chemical structures, thermal properties, and spherulitic morphologies of the copolymers are studied adopting FT-IR, NMR, TGA, DSC, WAXD, and POM. The polyesters exhibit antibacterial activity against Escherichia coli. The adopted synthetic approach can be transferred to other polyesters in a straightforward manner.

Thermo-Switchable Antibacterial Activity

A copolymer system of 2-aminoethyl methacrylate and N-isopropylacrylamide comprises novel properties: changes in conformation and hydrophilicity upon heating influence the antibacterial activity and result in a switchable biocidal effect. The copolymers are characterized via NMR, MALDI-ToF MS, phase transition behavior, and antibacterial tests with E. coli or B. subtilis. MIC and MBC are determined using standard dilution methods, temperature-dependence via incubation at different temperatures and cytotoxicity by MTT tests. The copolymers exhibit lower MIC in globule than coil conformation, crosslinking on cotton results in non-leaching materials with better antibacterial activity above than below the phase-transition point.

Phantom Ring-Closing Condensation Polymerization: Towards Antibacterial Oligoguanidines

The first example of phantom ring-closing condensation polymerization for the synthesis of oligoguanidines is presented. A new oligoguanidine with a ring structure was achieved in one step by the condensation reaction of a triamine, like diethylenetriamine, with guanidine hydrochloride. The condensation reaction proceeded by selective ring-closure towards the formation of five-membered rings in the oligomer backbone. The resulting polymer repeat unit structure was different from the starting monomers (phantom polymer) and was formed by elimination of three molecules of ammonia per repeat unit. The inter-, intra-, and inter-molecular reaction sequences led to the new structure as proved by different spectroscopic techniques (atmospheric pressure chemical-ionization mass spectrometry, and one-dimensional and two-dimensional homo- and heteronuclear correlation NMR experiments) as well as supported by quantum chemical investigations. Preliminary results regarding antibacterial use of the resulting oligoguanidine were also promising and showed its effect within 15-30 min as an antibacterial material.

Exploring suitable oligoamines for phantom ring-closing condensation polymerization with guanidine hydrochloride

Different model compounds were applied in step-growth condensation reactions with guanidine hydrochloride in order to explore the scope of tri- and oligoamine applicability for phantom ring-closing condensation polymerization processes. The selective formation of five-membered rings was proven by APCI mass spectrometry, different one- and two-dimensional homo- and heteronuclear coupling NMR techniques and investigated via quantum chemical calculations. Furthermore the possibility of ring-closing reactions among guanidine hydrochloride and merely secondary amines was precluded. The obtained oligomers were exposed to antibacterial tests and exhibited a moderate activity towards Escherichia coli.