Mechanical characterization of oligo(ethylene glycol)-based hydrogels by dynamic nanoindentation experiments.

Oligo(ethylene glycol)-based (OEG) hydrogel samples of varying cross-link densities and degrees of swelling were characterized through dynamic nanoindentation testing. Experiments were performed using a non-standard nanoindentation method, which was validated on a standard polystyrene sample. This method maximizes the capability of the instrument to measure the stiffness and damping of highly compliant, viscoelastic materials. Experiments were performed over the frequency range of 1 to 50 Hz, using a 1mm diameter flat punch indenter. A hydration method was adopted to avoid sample dehydration during testing. Values of storage modulus (E') ranged from 3.5 to 8.9 MPa for the different OEG-hydrogel samples investigated. Samples with higher OEG concentrations showed greater scatter in the modulus measurements and it is attributed to inhomogeneities in these materials. The (E') values did not show a strong variation over frequency for any of the samples. Values of loss modulus (E") were two orders of magnitude lower than the storage modulus, resulting in very low values of loss factor (E"/E'<0.1). These are characteristics of strong gels, which present negligible viscous properties.

Triple-shape effect in polymer-based composites by cleverly matching geometry of active component with heating method.

A triple-shape effect is created for a segmented device consisting of an active component encapsulated in a highly flexible polymer network. Segments with the same composition but different interface areas can be recovered independently either at specific field strengths (Hsw ) during inductive heating, at a specific time during environmentally heating, or at different airflow during inductive heating at constant H. Herein the type of heating method regulates the sequence order.

Behaviour of fibroblasts on water born acrylonitrile-based copolymers containing different cationic and anionic moieties.

The chemical composition of a substrate can influence the adhesion, viability and proliferation of cells seeded on the substrate. The aim of this work was to investigate the influence of different cationic or anionic moieties in acrylonitrile-based copolymers on the interaction with fibroblasts. A series of ten different types of acrylonitrile-based copolymers with a random sequence structure was prepared using a water born synthesis process to exclude potential residues of organic solvents. As charged comonomers cationic methacrylic acid-2-aminoethylester hydrochloride (AEMA), N-3-amino-propyl-methacrylamide hydrochloride (APMA) and anionic 2-methyl-2-propene-1-sulfonic acid sodium salt (NaMAS) were utilized. By application of a specific sintering procedure the copolymer materials were processed into transparent disks for conducting cell tests in direct contact. The copolymers were analyzed with respect to their composition and surface properties. Cytotoxicity tests of the polymer extracts, as well as of the disks were performed with L929 mouse fibroblasts. All copolymers showed no cytotoxic effects. Furthermore, for higher molar ratios of AEMA an increase in cell growth could be observed, which might be a hint that higher charge densities are favorable for the proliferation of L929 cells.

Upscaling the synthesis of biodegradable multiblock copolymers capable of a shape-memory effect.

Thermoplastic, phase-segregated multiblock copolymers (MBC) with shape-memory capability consisting of poly(ε-caprolactone) (PCL) switching segments and poly(p-dioxanone) (PDO) or poly(ω-pentadecalactone) (PPD) hard segments were prepared on a scale of several kilograms following a newly developed upscaling procedure. Dihydroxytelechelic poly(ether)esters were coupled by an aliphatic diisocyanate gaining products of sufficiently high molecular weights. The obtained biodegradable MBC exhibited good elastic properties and a shape-memory effect (SME) with a switching temperature (T (sw)) around body temperature. The yield of the synthesis could be improved and reaction time reduced, while mechanical and shape-memory properties were not affected. These multifunctional materials, which are now available in a larger scale have a high application potential as smart implant materials especially for minimally invasive surgery.

Common genetic variants in the interleukin-6 and chitotriosidase genes are associated with the risk for serious infection in children undergoing therapy for acute myeloid leukemia.

Infectious complications represent a substantial cause of morbidity and mortality in children undergoing therapy for acute myeloid leukemia (AML). Since it has been shown that alterations in innate immune pathways contribute to the risk for serious infections, we analyzed well-characterized variants in innate immune genes (TNF, IL6, IL8, MPO, CHIT, FCGR2A, TLR2, and TLR4) to determine their possible contribution to infectious complications during therapy for pediatric AML. The study population consisted of 168 North European Caucasian children enrolled on the clinical trial AML-BFM 93. We found an association between Gram-negative bacterial infection and common, functional variants in two genes, IL6 and CHIT. The risk for infection was significantly higher in children with the G allele in the IL6 promoter at -174 bp (P=0.026) and in patients with the H allele of CHIT (P=0.033). The promoter variant in IL6 has been shown to increase expression while the H allele disrupts both function and circulating levels. Our data suggest that variant alleles of both IL6 and CHIT could influence susceptibility to infection with Gram-negative bacteria in children undergoing therapy for AML. Follow-up studies, namely replication association studies and in vitro investigation of these common polymorphisms, are warranted to confirm these observations.

Investigations on the development and regression of corticosteroid-induced thinning of the skin in various parts of the human body during and after topical application of amcinonide.

In 15 subjects 6 different parts of the body were treated with the potent topical corticosteroid (CS) amcinonide once a day for 21 days. The skin thickness of the treated areas was measured sonographically at intervals of 2 days. After completion of the CS application the regression of the CS-induced reduction in skin thickness was measured for a further 14 days. A clear thinning of the skin could be measured after only 4 days and continued up to the 21st day of treatment. This thinning regressed completely in all areas after 10-12 days. The thinning and regression curves were very similar for all body areas. Differences in intensity of thinning were evident. No tachyphylaxis was detected.

Vitamin status of inpatients with chronic cephalgia and dysfunction pain syndrome and effects of a vitamin supplementation.

66 female inpatients with dysfunction pain syndrome, chronic cephalgia and facial pain participated in a randomized, placebo-controlled double-blind study, half the patients receiving a multivitamin preparation for 12 days and the other half a placebo. The biochemically determined vitamin status at the start of the study revealed gaps in the coverage of the vitamin supply, particularly with regard to the vitamins thiamin, riboflavin and folic acid. 65% of the patients showed a subclinical vitamin deficiency of two or more vitamins. With regard to the development of pain during the study no statistically significant differences could be determined, however, between the active-treatment and placebo groups. Nevertheless, a clear reduction in pain was more frequently observed in the active-treatment group, and a deterioration of pain more frequently in the placebo group. A reduction in pain was reported more often by patients in whom the values of alpha-ETK, alpha-EGOT, folic acid and cyanocobalamin improved in the course of the study. Vitamin administration in physiological doses evidently have only weak effects on the behavior of pain; analgesic vitamin effects may be presumed in the case of correspondingly high therapeutic doses for a prolonged period.