Ralf Wyrwa

Release of metronidazole from electrospun poly(l-lactide-co-d/l-lactide) fibers for local periodontitis treatment

OBJECTIVES We aimed to achieve detailed biomaterials characterization of a drug delivery system for local periodontitis treatment based on electrospun metronidazole-loaded resorbable polylactide (PLA) fibers. METHODS PLA fibers loaded with 0.1-40% (w/w) MNA were electrospun and were characterized by SEM and DSC. HPLC techniques were used to analyze the release profiles of metronidazole (MNA) from these fibers. The antibacterial efficacy was determined by measuring inhibition zones of drug-containing aliquots from the same electrospun fiber mats in an agar diffusion test. Three pathogenic periodontal bacterial strains: Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were studied. Cytotoxicity testing was performed with human gingival fibroblasts by: (i) counting viable cells via live/dead staining methods and (ii) by exposing cells directly onto the surface of MNA-loaded fibers. RESULTS MNA concentration influenced fiber diameters and thus w/w surface areas: diameter being minimal and area maximal at 20% MNA. HPLC showed that these 20% MNA fibers had the fastest initial MNA release. From the third day, MNA release was slower and nearly linear with time. All fiber mats released 32-48% of their total drug content within the first 7 days. Aliquots of media taken from the fiber mats inhibited the growth of all three bacterial strains. MNA released up to the 28th day from fiber mats containing 40% MNA significantly decreased the viability of F. nucleatum and P. gingivalis and up to the 2nd day also for the resistant A. actinomycetemcomitans. All of the investigated fibers and aliquots showed excellent cytocompatibility. SIGNIFICANCE This study shows that MNA-loaded electrospun fiber mats represent an interesting class of resorbable drug delivery systems. Sustained drug release properties and cytocompatibility suggest their potential clinical applicability for the treatment of periodontal diseases.

Light-triggered CO release from nanoporous non-wovens

The water insoluble and photoactive CO releasing molecule dimanganese decacarbonyl (CORM-1) has been non-covalently embedded into poly(l-lactide-co-d/l-lactide) fibers via electrospinning to enable bioavailability and water accessibility of CORM-1. SEM images of the resulting hybrid non-wovens reveal a nanoporous fiber morphology. Slight CO release from the CORM-1 in the electrospinning process induces nanoporosity. IR spectra show the same set of carbonyl bands for the CORM-1 precursor and the non-woven. When the material was exposed to light (365-480 nm), CO release from the incorporated CORM-1 was measured via heterogeneous myoglobin assay, a portable CO electrode and an IR gas cuvette. The CO release rate was wavelength dependent. Irradiation at 365 nm resulted in four times faster release than at 480 nm. 3.4 μmol of CO per mg non-woven can be generated. Mouse fibroblast 3T3 cells were used to show that the hybrid material is non-toxic in the darkness and strongly photocytotoxic when light is applied.

Novel (N-Ferrocenylmethyl)amines and (N-Ferrocenylmethylen)imines derived from vicinal steroid amino alcohols and amines: synthesis, molecular structure, and biological activity

Novel steroidal (N-ferrocenylmethyl)amines with potential biologic activity and of potential interest as chiral ligands for metal complexation were synthesized. The new compounds were screened in vitro for their potential as antimicrobial agents. The synthesis of the new steroidal ferrocenes, including two X-ray crystal structures and biologic assays, are described. The 16-(ferrocenylmethyl)amino-estratrienes 4a-d, 7b, and 10b exhibited outstanding broad antimicrobial activity particularly against mycobacteria and multi-resistant staphylococci. Thus, they can be considered as new lead structures. In contrast, the analogous 3 alpha-(ferrocenylmethyl)amino-cholestanes 12 possessed only weak activity. The reaction of the four isomeric amino alcohols 1a-d (Scheme 1) with ferrocenecarbaldehyde was studied. 1b and 1c with 16/17-trans configuration yielded nearly quantitatively the (E)-Schiff bases 2b and 2c (Scheme 2). In contrast to the trans-compounds, condensation of the cisconfigurated amino alcohols 1a and 1d furnished tautomeric mixtures of the Schiff bases (2a and 2d, respectively) and their corresponding 1,3-oxazolidines (3a and 3d, respectively). The novel (N-ferrocenylmethyl)amines 4a-d were obtained in excellent yields by reduction of the tautomer mixtures and the uniform Schiff bases with sodium borohydride in ethanol. Starting with the 16 beta-hydroxy compound 5a, the synthesis of 16 beta- and 16 alpha-amino-3-methoxy-estra-1,3,5(10)-triene (6b, 9b) is described. The corresponding 16-(N-ferrocenylmethyl)amines 7b and 10b and the 3 alpha-(N-ferrocenylmethyl)amino-cholestanes 12 were synthesized (Scheme 3) for comparison in biologic tests.

Synthesis of N,N-bis[2-(2-pyridyl)ethyl]amino steroids and related compounds intended as chiral ligands for copper ions

Abstract Compounds with the N , N -bis[2-(2-pyridyl)ethyl]amino structure (RPY2) are useful tridentate ligands for copper(I) ions, which can bind and activate oxygen from the atmosphere. For diastereoselective and enantioselective oxidation reactions, hitherto unknown chiral ligands possessing tripodal structures have been synthesized starting from homochiral steroids. The double Michael addition of primary steroidal amines and aminoalcohols to 2-vinyl pyridine was not very succesful. However, homochiral bidentate ligands with N- [2-(2-pyridyl)ethyl]amino steroid structure could be obtained by this procedure in most cases. New routes (acylation of the bidentate ligands with 2-pyridylacetic acid followed by BH 3 ·THF reduction, or reductive amination of steroidal ketones, acylation and borane reduction) to the desired tridentate RPY2, also at sterically hindered positions, are described. In the last reaction sequence, ‘mixed’ tridentate ligands can also be obtained. Copper complexation and oxygen activation with these ligands are briefly discussed.

Beiträge zur chemie organometallischer metallacyclischer nebengruppenmetallverbindungen

Abstract A new synthetic route to Li 2 Ni(C 4 H 8 ) 2 (Solv) x (Solv = diethylether, Et 2 O, x = 1 ( 1 ); tetramethylethylendiamin, TMED, x = 2 ( 2 ); tetrahydrofuran, THF, 4 ( 3 )) is described. (Li(THF) 2 ) 2 Ni(C 4 H 8 ) 2 ( 3 ) has been characterized by X-ray studies. The 1 H and 13 C NMR spectral properties of the metallacycles are reported.

Light-triggered NO release from a nanofibrous non-woven

Light-controlled NO delivery systems promise new applications in phototherapies. For this purpose, a ruthenium nitrosyl complex [(2)Ru(NO)(Cl)] with the novel ligand N,N′-(1,2-phenylene)bis(1-methyl-1H-imidazole-2-carboxamide) (2) has been synthesised and characterised in detail. The photoactive {Ru–NO}6 nitrosyl released NO in DMSO upon exposure to low-intensity UV-A light (λ = 366 nm). In order to create an applicable system the water-insoluble [(2)Ru(NO)(Cl)] was embedded into poly(L-lactide-co-D/L-lactide) nanofibrous non-wovens by electrospinning. Exposure of a 25 wt% non-woven of [(2)Ru(NO)(Cl)] to UV-A light resulted in a continuous release of NO into an aqueous solution. The cytoxicity of the non-woven against 3T3 mouse fibroblasts was very low.

Beiträge zur chemie organometallischer metallacyclischer nebengruppenmetallverbindungen XII. Synthese, NMR-spektroskopische untersuchung und kristallstruktur von 1—vergleichende DTA-untersuchungen von 1 und unsubstituierten nickelacyclopentan-komplexen der zusammensetzung (L = TMEDA, THF, d8-THF)

The complex 1 was synthesized with good yield by treatment of NiCp2 with the dilithium compound LiCH2CMe2CMe2CH2Li 2. It was characterized by elemental analysis, 1H and 13C NMR and X-ray spectroscopy. The crystal data and the final R values are as follows: crystal system: orthorhombic, space group Pnma (No. 62) with cell parameters a = 17.849(3) A, b = 13.138(2) A, c = 14.516(1) A, Z = 4 and R = 0.062, RW = 0.060. The average distance LiNi (2.506(7) A) is only little larger than the sum of the covalence radii of the two elements (2.38 A). According to DTA studies, the following decomposition temperatures of the complexes 1, 3, (L = THF 4, d8-THF 5) resulted: 1 (234°C), 3 (182°C), 4 (108°C), 5 (108°C). Surprisingly they vary considerably. After the DTA measurement, the gas phases above the solid decomposition residues were analyzed by gas chromatography and mass spectroscopy. The results of these investigations are reported.

Electrospun Poly(ester-Urethane)- and Poly(ester-Urethane-Urea) Fleeces as Promising Tissue Engineering Scaffolds for Adipose-Derived Stem Cells

An irreversible loss of subcutaneous adipose tissue in patients after tumor removal or deep dermal burns makes soft tissue engineering one of the most important challenges in biomedical research. The ideal scaffold for adipose tissue engineering has yet not been identified though biodegradable polymers gained an increasing interest during the last years. In the present study we synthesized two novel biodegradable polymers, poly(ε-caprolactone-co-urethane-co-urea) (PEUU) and poly[(L-lactide-co-ε-caprolactone)-co-(L-lysine ethyl ester diisocyanate)-block-oligo(ethylene glycol)-urethane] (PEU), containing different types of hydrolytically cleavable bondings. Solutions of the polymers at appropriate concentrations were used to fabricate fleeces by electrospinning. Ultrastructure, tensile properties, and degradation of the produced fleeces were evaluated. Adipose-derived stem cells (ASCs) were seeded on fleeces and morphology, viability, proliferation and differentiation were assessed. The biomaterials show fine micro- and nanostructures composed of fibers with diameters of about 0.5 to 1.3 µm. PEUU fleeces were more elastic, which might be favourable in soft tissue engineering, and degraded significantly slower compared to PEU. ASCs were able to adhere, proliferate and differentiate on both scaffolds. Morphology of the cells was slightly better on PEUU than on PEU showing a more physiological appearance. ASCs differentiated into the adipogenic lineage. Gene analysis of differentiated ASCs showed typical expression of adipogenetic markers such as PPARgamma and FABP4. Based on these results, PEUU and PEU meshes show a promising potential as scaffold materials in adipose tissue engineering.

Bactericidal Effect of a Photoresponsive Carbon Monoxide-Releasing Nonwoven against Staphylococcus aureus Biofilms

ABSTRACT Staphylococcus aureus is a leading pathogen in skin and skin structure infections, including surgical and traumatic infections that are associated with biofilm formation. Because biofilm formation is accompanied by high phenotypic resistance of the embedded bacteria, they are almost impossible to eradicate by conventional antibiotics. Therefore, alternative therapeutic strategies are of high interest. We generated nanostructured hybrid nonwovens via the electrospinning of a photoresponsive carbon monoxide (CO)-releasing molecule [CORM-1, Mn2(CO)10] and the polymer polylactide. This nonwoven showed a CO-induced antimicrobial activity that was sufficient to reduce the biofilm-embedded bacteria by 70% after photostimulation at 405 nm. The released CO increased the concentration of reactive oxygen species (ROS) in the biofilms, suggesting that in addition to inhibiting the electron transport chain, ROS might play a role in the antimicrobial activity of CORMs on S. aureus. The nonwoven showed increased cytotoxicity on eukaryotic cells after longer exposure, most probably due to the released lactic acid, that might be acceptable for local and short-time treatments. Therefore, CO-releasing nonwovens might be a promising local antimicrobial therapy against biofilm-associated skin wound infections.

Development of novel electrospun dual-drug fiber mats loaded with a combination of ampicillin and metronidazole

OBJECTIVE Our study was performed with the aim of preparing electrospun polylactide fibers with a combination of ampicillin (AMP) and metronidazole (MNZ) and investigating their drug release behavior and the antibacterial effect on Aggregatibacter actinomycetemcomitans and other oral pathogens. METHODS AMP and MNZ were integrated as a combination in two separate fibers (dual fiber mats - DFW mix) of electrospun PLA fiber mats by means of multijet electrospinning and in a single fiber (single fiber mats - SFW mix). HPLC (high-performance liquid chromatography) was used to measure the released drug quantities. Agar diffusion tests were used to determine the antibacterial effect of the eluates on A. actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis and Enterococcus faecalis. The neutral red test was made to examine the cytocompatibility of the eluates with human gingival fibroblasts (hGFs). RESULTS The release of the active agents varied with the antibiotic concentrations initially used in the fiber mats, but also with the distribution of the active agents in one or two fibers. Of the total quantity of MNZ (AMP), the SFW mix fiber mats released >60% (>70%) within a span of 5min, and 76% (71%) after 96h. With these drug concentrations released by the fiber mats (≥5m%), an antibacterial effect was achieved on A. actinomycetemcomitans and on all other species tested. Fiber mats and their eluates have no cytotoxic influence on human gingival fibroblasts (hGFs). SIGNIFICANCE Electrospun AMP/MNZ-loaded polymer fibers are a potential drug delivery system for use in periodontal and endodontic infections.