Poly(2-oxazoline)-derived contact biocides: contributions to the understanding of antimicrobial activity.

A set of poly(2-oxazoline)-derived (co-)polymers was prepared by microwave-assisted polymerizations and acid-mediated hydrolysis and tested for antimicrobial activity in 50 × 50 × 2 mm PP compound plates containing 5 wt% of the polymers. Antimicrobial activity against gram-negative E. coli and P. aeruginosa as well as C. albicans depended only on the degree of hydrolysis, while antimicrobial activity against gram-positive S. aureus was only observed for hydrolyzed poly(2-nonyl-2-oxazoline)s. The surface energies of the compound plates compared to pure PP were hardly altered, and the compounds can be considered as alternatives for PP. The presence of the biocide additives at the surface of the PP compound plates could be shown by combined ATR-IR, zeta potential, and SEM-EDX measurements. Antimicrobial activity was maintained during double incubation as well as for lowered amounts of the biocide additive of 1% in PP compound plates.

Strategies for the synthesis of poly(2-oxazoline)-based hydrogels.

Poly(2-oxazoline)-based networks currently receive great interest due to their versatile properties that can be tailor made by desktop-planned modifications. This feature summarizes strategies for the preparation of these networks, comprising the in situ cross-linking as well as polymer-analogous cross-linking routines such as (reversible) complex formation, physical processes, and covalent bond formation (involving reactions with olefinic species as well as with epoxides, isocyanates, aldehydes, acids, and their derivatives). Reflecting prominent application examples in the biomedic(in)al sector, poly(2-oxazoline)-co-polyester networks are described in a dedicated section.

Synthesis of poly(2-oxazoline)-based hydrogels with tailor-made swelling degrees capable of stimuli-triggered compound release.

A 32-membered library of poly(2-oxazoline)-based hydrogels of the composition pEtOx(m) -pPhOx(n) -pPBO(q) (m/n = 150/0, 100/50, 50/100, and 0/150; q = 1.5-30) was prepared from 2-ethyl- (EtOx), 2-phenyl-2-oxazoline (PhOx), and phenylene-1,3-bis-(2-oxazoline) (PBO). The polymerizations were performed from ground monomer mixtures at 140 °C in a single-mode microwave reactor in reaction times as short as 1 h. Purified hydrogels, containing no residual monomers, were obtained in yields of 95% or higher. Acid-mediated hydrolysis rates as well as swelling degrees of the hydrogels were adjustable over a broad range; swelling degrees in water/ethanol/dichloromethane ranged from 0 to 13.8/11.7/20.0. The hydrogels could incorporate organic molecules according to in situ or post-synthetic routines. Post-synthetic routines enabled for the preparation of hydrogels from which the incorporated compounds were only released through diffusion processes if the solvent was changed or through hydrogel degradation if the pH was lowered.

Simple protocols for NMR analysis of the enantiomeric purity of chiral primary amines.

A simple three-component chiral derivatization protocol for determining the enantiopurity of chiral primary amines by 1H NMR spectroscopic analysis is described here. The method involves condensation of the amines with 2-formylphenylboronic acid and enantiopure 1,1'-bi-2-naphthol. This approach affords a mixture of diastereoisomeric iminoboronate esters whose ratio can be determined by the integration of well-resolved diastereotopic resonances in their 1H NMR spectra, thus enabling the enantiopurity of the parent amine to be determined easily. The protocol, as described, takes less than 90 min to complete.

Simple protocols for NMR analysis of the enantiomeric purity of chiral diols.

A three-component chiral derivatization protocol for determining the enantiopurity of chiral diols by (1)H NMR spectroscopic analysis is described here. The present approach involves the derivatization of 1,2- 1,3- and 1,4-diols with 2-formylphenylboronic acid and enantiopure alpha-methylbenzylamine. This method affords a mixture of diastereoisomeric iminoboronate esters whose ratio can be determined by integration of well-resolved diastereotopic resonances in their (1)H NMR spectra, thus enabling the determination of the enantiopurity of the parent diol. The protocol as described takes less than 90 min to complete.

DNA binding of tilorone: 1H NMR and calorimetric studies of the intercalation.

The fluorene derivative tilorone has received great attention as a DNA intercalator and has been widely recognized as an inducer of interferon. The biological activity of tilorone is known to be related to its binding mode with DNA; however, few structural and thermodynamic studies have elaborated on this issue. This paper presents two-dimensional (2-D) NMR and isothermal titration calorimetry (ITC) for the tilorone/DNA complex, coupled with circular dichroism (CD) spectroscopy and viscosity measurements. NMR investigation suggests that tilorone binds to DNA through intercalation, showing greater affinity for insertion between AT base pairs than between CG pairs. CD spectral changes were observed for T/B (tilorone/DNA base pair molar ratio) ratios greater than the stoichiometric ratio generally expected for intercalators (i.e., T/B = 0.5, according to the neighbor-exclusion principle). However, there was a clear plateau in the CD intensity between T/B < 0.35 and T/B > 0.45. From comparison with NMR and other measurements, we postulate that CD changes below the plateau should be related to the intercalation and the latter to electrostatic interactions and nonspecific bindings. ITC data showed that DeltaH < -TDeltaS < 0, which indicated that tilorone/DNA binding is enthalpy controlled. The magnitude of Kb (the binding constant) was of the same order as that of ethidium bromide. The stoichiometric number, obtained from ITC, CD, and UV data, implied a relatively smaller value (0.28-0.35) than that of the neighbor-exclusion principle. This is because side chains located in the groove disrupt further intercalation to the adjacent sites.

Simple protocol for NMR analysis of the enantiomeric purity of diols.

[reaction: see text] A practically simple three-component chiral derivatization protocol for determining the enantiopurity of chiral 1,2-, 1,3-, and 1,4-diols by (1)H NMR spectroscopic analysis is described. The method involves treatment with 2-formylphenylboronic acid and enantiopure alpha-methylbenzylamine to afford a mixture of diastereoisomeric iminoboronate esters whose ratio is an accurate reflection of the enantiopurity of the parent diol.

Simple protocol for NMR analysis of the enantiomeric purity of primary amines.

[reaction: see text] A practically simple three-component chiral derivatizing protocol for determining the enantiopurity of 13 chiral primary amines by (1)H NMR spectroscopic analysis is described, including analysis of those that contain remote stereocenters.