Fraunhofer Society

About: Fraunhofer Society is a government organization based out in Munich, Germany. It is known for research contribution in the topics: Laser & Silicon. The organization has 24736 authors who have published 40168 publications receiving 820894 citations.

Killing of adherent oral microbes by a non-thermal atmospheric plasma jet.

Abstract: Atmospheric plasma jets are being intensively studied with respect to potential applications in medicine. The aim of this in vitro study was to test a microwave-powered non-thermal atmospheric plasma jet for its antimicrobial efficacy against adherent oral micro-organisms. Agar plates and dentin slices were inoculated with 6 log(10) c.f.u. cm(-2) of Lactobacillus casei, Streptococcus mutans and Candida albicans, with Escherichia coli as a control. Areas of 1 cm(2) on the agar plates or the complete dentin slices were irradiated with a helium plasma jet for 0.3, 0.6 or 0.9 s mm(-2), respectively. The agar plates were incubated at 37 degrees C, and dentin slices were vortexed in liquid media and suspensions were placed on agar plates. The killing efficacy of the plasma jet was assessed by counting the number of c.f.u. on the irradiated areas of the agar plates, as well as by determination of the number of c.f.u. recovered from dentin slices. A microbe-killing effect was found on the irradiated parts of the agar plates for L. casei, S. mutans, C. albicans and E. coli. The plasma-jet treatment reduced the c.f.u. by 3-4 log(10) intervals on the dentin slices in comparison to recovery rates from untreated controls. The microbe-killing effect was correlated with increasing irradiation times. Thus, non-thermal atmospheric plasma jets could be used for the disinfection of dental surfaces.

Mutagenicity testing for chemical risk assessment: update of the WHO/IPCS Harmonized Scheme.

Abstract: Since the publication of the International Programme on Chemical Safety (IPCS) Harmonized Scheme for Mutagenicity Testing, there have been a number of publications addressing test strategies for mutagenicity. Safety assessments of substances with regard to genotoxicity are generally based on a combination of tests to assess effects on three major end points of genetic damage associated with human disease: gene mutation, clastogenicity and aneuploidy. It is now clear from the results of international collaborative studies and the large databases that are currently available for the assays evaluated that no single assay can detect all genotoxic substances. The World Health Organization therefore decided to update the IPCS Harmonized Scheme for Mutagenicity Testing as part of the IPCS project on the Harmonization of Approaches to the Assessment of Risk from Exposure to Chemicals. The approach presented in this paper focuses on the identification of mutagens and genotoxic carcinogens. Selection of appropriate in vitro and in vivo tests as well as a strategy for germ cell testing are described.

Chemical tailoring of gelatin to adjust its chemical and physical properties for functional bioprinting

Abstract: Double chemical functionalization of gelatin by methacrylation and acetylation of free amino groups enables control over both the viscous behavior of its solutions and the mechanical properties of the resulting hydrogels after photochemical crosslinking. The degree of methacrylation is controlled by the molar excess of methacrylic anhydride applied. Tenfold molar excess leads to highly methacrylated gelatin (GM10), resulting in solutions with low viscosities within the inkjet-printable range (10 wt%: 3.3 ± 0.5 mPa s, 37 °C) and crosslinked hydrogels with high storage moduli G′ (10 wt%: 15.2 ± 6.4 kPa). Twofold excess of methacrylic anhydride leads to less methacrylated gelatin (GM2) proper for preparation of soft hydrogels (10 wt%: G′ = 9.8 ± 4.6 mPa s) but its solutions are highly viscous (10 wt%: 14.2 ± 1.1 mPa s, 37 °C) and thus prone to clogging printing nozzles. Here we show that additional introduction of acetyl functionalities into GM2 results in a significant decrease in solution viscosity (10 wt%: 2.9 ± 0.2 mPa s, 37 °C) and prevention of physical gel formation. In such a manner twofold functionalized gelatin can be inkjet-printed while the degree of chemical crosslinking remains low and the resulting gels are soft. Thus, by adjustable twofold modification of gelatin, i.e. inserting photochemically reactive and inert groups, a versatile bioink for inkjet bioprinting is created, which allows for addressing ECM based hydrogel matrices with a broad range of physical properties. Moreover, bioinks are proven to be cytocompatible and proper for inkjet printing of viable mammalian cells.