Christoph P. Fik

Impact of Functional Satellite Groups on the Antimicrobial Activity and Hemocompatibility of Telechelic Poly(2-methyloxazoline)s

Polyoxazolines with a biocidal quarternary ammonium end-group are potent biocides. Interestingly, the antimicrobial activity of the whole macromolecule is controlled by the nature of the group at the distal end. These nonreactive groups are usually introduced via the initiator. Here we present a study with a series of polymethyloxazolines with varying satellite groups introduced upon termination of the polymerization reaction. This allowed us to introduce a series of functional satellites, including hydroxy, primary amino, and double-bond-containing groups. The resulting telechelic polyoxazolines were explored regarding their antimicrobial activity and toxicity. It was found that the functional satellite groups greatly controlled the minimal inhibitory concentrations against the bacteria Staphylococcus aureus and Escherichia coli in a range of 10 to 2500 ppm. Surprisingly, the satellite groups also controlled the hemotoxicity but in a different way than the antimicrobial efficiency.

Organosoluble enzyme conjugates with poly(2-oxazoline)s via pyromellitic acid dianhydride.

The use of enzymes in organic solvents offers a great opportunity for the synthesis of complex organic compounds and is therefore in focus of current research. In this work we describe the synthesis of poly(2-methyl-1,3-oxazoline) (PMOx) and poly(2-ethyl-1,3-oxazoline) (PEtOx) enzyme conjugates with hen-egg white lysozyme, RNase A and α-chymotrypsin using a new coupling technique. The POXylation was carried out reacting pyromellitic acid dianhydride subsequently with ethylenediamine terminated POx and then with the NH₂-groups of the respective enzymes. Upon conjugation with the polymers, RNase A and lysozyme became fully soluble in DMF (1.4 mg/ml). These are the first examples of fully POXylated proteins, which become organosoluble. The synthesized enzyme conjugates were characterized by SDS-PAGE, isoelectric focusing, dynamic light scattering and size exclusion chromatography, which all indicated the full POXylation of the enzymes. The modified enzymes even partly retained their activity in water. With α-chymotrypsin as example we could demonstrate that the molecular weight of the attached polymer significantly influences the activity.

Well-defined amphiphilic poly(2-oxazoline) ABA-triblock copolymers and their aggregation behavior in aqueous solution.

Self-organization of block copolymers in solution is a way to obtain advanced functional superstructures. The synthesis of well-defined polymethyloxazoline-block-polyphenyloxazoline-block-polymethyloxazoline triblock copolymers is described and proven by (1) H NMR spectroscopy, SEC, and ESI-MS. The surprisingly water- soluble block copolymers do self-organize in aqueous solutions uniquely forming three coexisting well-defined structures: unimolecular micelles, micellar aggregates, and very form-stable polymersomes. This is the first example of a polymersome forming ABA-triblock copolymer with a glassy middle block. The spherical vesicles are analysed by scanning electron microscopy and transmission electron microscopy. It could be shown that these vesicles are indeed hollow spheres.

Telechelic Poly(2-oxazoline)s with a Biocidal and a Polymerizable Terminal as Collagenase Inhibiting Additive for Long-Term Active Antimicrobial Dental Materials

Dental repair materials face the problem that the dentin below the composite fillings is actively decomposed by secondary caries and extracellular proteases. To address this problem, poly(2-methyloxazoline) with a biocidal and a polymerizable terminal was explored as additive for a commercial dental adhesive. 2.5 wt% of the additive rendered the adhesive contact-active against Streptococcus mutans and washing with water for 101 d did not diminish this effect. The adhesive with 5 wt% additive kills S. mutans cells in the tubuli of bovine dentin. Further, the additive inhibits bacterial collagenase at 0.5 wt% and reduces activity of MMP-9. Human MMPs bound to dentin are inhibited by 96% in a medium with 5 wt% additive. Moreover, no adverse effect on the enamel/dentine shear bond strength was detected.

Ultrahigh-Aspect Ratio Microfiber-Furs as Plant-Surface Mimics Derived from Teeth

IO N The biomimetic of micro-, nanoand hierarchically structured hairy surfaces of plant origins is in focus of current research, inter alia, because of their extraordinary water-droplet and airbubble storage capability. [ 1–5 ] The latter is based on the great fl exibility of high-aspect-ratio fi laments (trichomes) and thus such surfaces show a typical Cassie-Baxter behavior, [ 6 , 7 ] i.e., water droplets are attached to the surface of air cushions and air pockets are entrapped underneath water. Particularly, the remarkable air-retaining properties make such surfaces economically and ecologically attractive for applications, in which a reduced drag of fl oating units (e.g. ships) in fl uid fl ow is desirable. [ 4 ] Typical examples of such hairy plant surfaces with aspect ratios of 100:1 and higher are the tops of lady’s mantle ( Alchemilla vulgaris ) leaves [ 5 ] and the undersides of Corokia cotoneaster (fam. Argophyllaceae ) leaves. Figure 1 shows a macro image of a Corokia cotoneaster leaf underside covered with water droplets. So far, it is not possible to exactly reproduce such natural hairy surfaces, particularly with respect to a high hair density of less than 10 μ m inter-fi lament distances and aspect ratio of more than 100:1. While the generation of microand nanohairs is readily achievable thanks to advanced spinning technologies such as electro spinning, these fi bers cannot easily be attached end-on in the required high densities. [ 8 ]

Development of Novel Photoinitiators as Substitutes of Camphorquinone for the LED Induced Polymerization of Methacrylates: A Bis‐Silyl Ketone

A new photoinitiator based on a bis-silylketone (BSK) structure is proposed as a novel compound leading to highly efficient initiating silyl radicals for the polymerization of methacrylates (e.g., a bisphenol A-glycidyl methacrylate/triethyleneglycol dimethacrylate blend (70%/30% w/w)) upon exposure to a blue light emitting diode and a green laser diode. The polymerization profiles are recorded by real time Fourier transform IR (FTIR) spectroscopy. Absorption, fluorescence, electron spin resonance (ESR), and steady state experiments are used to investigate the involved chemical mechanisms. Molecular orbital calculations are also carried out. Remarkably, BSK efficiently works in the presence of an iodonium salt. The overall mechanism for the initiation step is clarified. This novel class of silyl radical generating photoinitiators is really promising for the photopolymerization of methacrylates, e.g., in dental materials.