@article{RazzaqBehlLendlein2019,
  author    = {Razzaq, Muhammad Yasar and Behl, Marc and Lendlein, Andreas},
  title     = {Magneto-Mechanical Actuators with Reversible Stretching and Torsional Actuation Capabilities},
  series = {MRS Advances},
  volume    = {4},
  journal   = {MRS Advances},
  number    = {19},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.123},
  pages     = {1057 -- 1065},
  year      = {2019},
  abstract  = {Composite actuators consisting of magnetic nanoparticles dispersed in a crystallizable multiphase polymer system can be remotely controlled by alternating magnetic fields (AMF). These actuators contain spatially segregated crystalline domains with chemically different compositions. Here, the crystalline domain associated to low melting transition range is responsible for actuation while the crystalline domain associated to the higher melting transition range determines the geometry of the shape change. This paper reports magnetomechanical actuators which are based on a single crystalline domain of oligo(omega-pentadecalactone) (OPDL) along with covalently integrated iron(III) oxide nanoparticles (ioNPs). Different geometrical modes of actuation such as a reversible change in length or twisting were implemented by a magneto-mechanical programming procedure. For an individual actuation mode, the degree of actuation could be tailored by variation of the magnetic field strengths. This material design can be easily extended to other composites containing other magnetic nanoparticles, e.g. with a high magnetic susceptibility.},
  language  = {en}
}
@article{LehmannFranzToebbensetal.2019,
  author    = {Lehmann, Frederike and Franz, Alexandra and Toebbens, Daniel M. and Levcenco, Sergej and Unold, Thomas and Taubert, Andreas and Schorr, Susan},
  title     = {The phase diagram of a mixed halide (Br, I) hybrid perovskite obtained by synchrotron X-ray diffraction},
  series = {RSC Advances},
  volume    = {9},
  journal   = {RSC Advances},
  number    = {20},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2046-2069},
  doi       = {10.1039/c8ra09398a},
  pages     = {11151 -- 11159},
  year      = {2019},
  abstract  = {By using synchrotron X-ray powder diffraction, the temperature dependent phase diagram of the hybrid perovskite tri-halide compounds, methyl ammonium lead iodide (MAPbI3, MA+ = CH3NH3+) and methyl ammonium lead bromide (MAPbBr3), as well as of their solid solutions, has been established. The existence of a large miscibility gap between 0.29 ≤ x ≤ 0.92 (±0.02) for the MAPb(I1-xBrx)3 solid solution has been proven. A systematic study of the lattice parameters for the solid solution series at room temperature revealed distinct deviations from Vegard's law. Furthermore, temperature dependent measurements showed that a strong temperature dependency of lattice parameters from the composition is present for iodine rich compositions. In contrast, the bromine rich compositions show an unusually low dependency of the phase transition temperature from the degree of substitution.},
  language  = {en}
}
@article{BalkBehlLendlein2019,
  author    = {Balk, Maria and Behl, Marc and Lendlein, Andreas},
  title     = {Hydrolytic Degradation of Actuators Based on Copolymer Networks From Oligo(epsilon-caprolactone) Dimethacrylate and n-Butyl Acrylate},
  series = {MRS advances},
  volume    = {4},
  journal   = {MRS advances},
  number    = {21},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.202},
  pages     = {1193 -- 1205},
  year      = {2019},
  abstract  = {Shape-memory polymer actuators often contain crystallizable polyester segments. Here, the influence of accelerated hydrolytic degradation on the actuation performance in copolymer networks based on oligo(epsilon-caprolactone) dimethacrylate (OCL) and n-butyl acrylate is studied The semi-crystalline OCL was utilized as crosslinker with molecular weights of 2.3 and 15.2 kg.mol(-1) (ratio: 1:1 wt\%) and n-butyl acrylate (25 wt\% relative to OCL content) acted as softening agent creating the polymer main chain segments within the network architecture. The copolymer networks were programmed by 50\% elongation and were degraded by means of alkaline hydrolysis utilizing sodium hydroxide solution (pH = 13). Experiments were performed in the range of the broad melting range of the actuators at 40 degrees C. The degradation of test specimen was monitored by the sample mass, which was reduced by 25 wt\% within 105 d .45 degradation products, fragments of OCL with molecular masses ranging from 400 to 50.000 g.mol(-1) could be detected by NMR spectroscopy and GPC measurements. The cleavage of ester groups included in OCL segments resulted in a decrease of the melting temperature (T-m) related to the actuator domains (amorphous at the temperature of degradation) and simultaneously, the T-m associated to the skeleton domain was increased (semi-crystalline at the temperature of degradation). The alkaline hydrolysis decreased the polymer chain orientation of OCL domains until a random alignment of crystalline domains was obtained. This result was confirmed by cyclic thermomechanical actuation tests. The performance of directed movements decreased almost linearly as function of degradation time resulting in the loss of functionality when the orientation of polymer chains disappeared. Here, actuators were able to provide reversible movements until 91 d when the accelerated bulk degradation procedure using alkaline hydrolysis (pH = 13) was applied. Accordingly, a lifetime of more than one year can be guaranteed under physiological conditions (pH = 7.4) when, e.g., artificial muscles for biomimetic robots as potential application for these kind of shape-memory polymer actuators will be addressed.},
  language  = {en}
}
@article{KuhnlaReinthalerBrauneetal.2019,
  author    = {Kuhnla, A. and Reinthaler, Markus and Braune, Steffen and Maier, A. and Pindur, Gerhard and Lendlein, Andreas and Jung, Friedrich},
  title     = {Spontaneous and induced platelet aggregation in apparently healthy subjects in relation to age},
  series = {Clinical hemorheology and microcirculation : blood flow and vessels},
  volume    = {71},
  journal   = {Clinical hemorheology and microcirculation : blood flow and vessels},
  number    = {4},
  publisher = {IOS Press},
  address   = {Amsterdam},
  issn      = {1386-0291},
  doi       = {10.3233/CH-199006},
  pages     = {425 -- 435},
  year      = {2019},
  abstract  = {Thrombotic disorders remain the leading cause of mortality and morbidity, despite the fact that anti-platelet therapies and vascular implants are successfully used today. As life expectancy is increasing in western societies, the specific knowledge about processes leading to thrombosis in elderly is essential for an adequate therapeutic management of platelet dysfunction and for tailoring blood contacting implants. This study addresses the limited available data on platelet function in apparently healthy subjects in relation to age, particularly in view of subjects of old age (80-98 years). Apparently healthy subjects between 20 and 98 years were included in this study. Platelet function was assessed by light transmission aggregometry and comprised experiments on spontaneous as well as ristocetin-, ADP- and collagen-induced platelet aggregation. The data of this study revealed a non-linear increase in the maximum spontaneous platelet aggregation (from 3.3\% +/- 3.3\% to 10.9\% +/- 5.9\%). The maximum induced aggregation decreased with age for ristocetin (from 85.8\% +/- 7.2\% to 75.0\% +/- 7.8\%), ADP (from 88.5\% +/- 4.6\% to 64.8\% +/- 7.3\%) and collagen (from 89.5\% +/- 3.0\% to 64.0\% +/- 4.0\%) in a non-linear manner (linear regression analysis). These observations indicate that during aging, circulating platelets become increasingly activated but lose their full aggregatory potential, a phenomenon that was earlier termed "platelet exhaustion". In this study we extended the limited existing data for spontaneous and induced platelet aggregation of apparently healthy donors above the age of 75 years. The presented data indicate that the extrapolation of data from a middle age group does not necessarily predict platelet function in apparently healthy subjects of old age. It emphasizes the need for respective studies to improve our understanding of thrombotic processes in elderly humans.},
  language  = {en}
}
@article{DengZouWangetal.2019,
  author    = {Deng, Zijun and Zou, Jie and Wang, Weiwei and Nie, Yan and Tung, Wing-Tai and Ma, Nan and Lendlein, Andreas},
  title     = {Dedifferentiation of mature adipocytes with periodic exposure to cold},
  series = {Clinical hemorheology and microcirculation : blood flow and vessels},
  volume    = {71},
  journal   = {Clinical hemorheology and microcirculation : blood flow and vessels},
  number    = {4},
  publisher = {IOS Press},
  address   = {Amsterdam},
  issn      = {1386-0291},
  doi       = {10.3233/CH-199005},
  pages     = {415 -- 424},
  year      = {2019},
  abstract  = {Lipid-containing adipocytes can dedifferentiate into fibroblast-like cells under appropriate culture conditions, which are known as dedifferentiated fat (DFAT) cells. However, the relative low dedifferentiation efficiency with the established protocols limit their widespread applications. In this study, we found that adipocyte dedifferentiation could be promoted via periodic exposure to cold (10 degrees C) in vitro. The lipid droplets in mature adipocytes were reduced by culturing the cells in periodic cooling/heating cycles (10-37 degrees C) for one week. The periodic temperature change led to the down-regulation of the adipogenic genes (FABP4, Leptin) and up-regulation of the mitochondrial uncoupling related genes (UCP1, PGC-1 alpha, and PRDM16). In addition, the enhanced expression of the cell proliferation marker Ki67 was observed in the dedifferentiated fibroblast-like cells after periodic exposure to cold, as compared to the cells cultured in 37 degrees C. Our in vitro model provides a simple and effective approach to promote lipolysis and can be used to improve the dedifferentiation efficiency of adipocytes towards multipotent DFAT cells.},
  language  = {en}
}
@article{MazurekBudzynskaRazzaqBehletal.2019,
  author    = {Mazurek-Budzynska, Magdalena and Razzaq, Muhammad Yasar and Behl, Marc and Lendlein, Andreas},
  title     = {Shape-Memory Polymers},
  series = {Functional Polymers},
  journal   = {Functional Polymers},
  publisher = {Springer},
  address   = {Cham},
  isbn      = {978-3-319-95987-0},
  issn      = {2510-3458},
  doi       = {10.1007/978-3-319-95987-0_18},
  pages     = {605 -- 663},
  year      = {2019},
  abstract  = {Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of changing their shape on demand. A shape-memory function is a result of the polymer architecture together with the application of a specific programming procedure. Various possible mechanisms to induce the shape-memory effect (SME) can be realized, which can be based on thermal transitions of switching domains or on reversible molecular switches (e.g., supramolecular interactions, reversible covalent bonds). Netpoints, which connect the switching domains and determine the permanent shape, can be either provided by covalent bonds or by physical intermolecular interactions, such as hydrogen bonds or crystallites. This chapter reviews different ways of implementing the phenomenon of programmable changes in the polymer shape, including the one-way shape-memory effect (1-W SME), triple-and multi-shape effects (TSE/ MSE), the temperature-memory effect (TME), and reversible shape-memory effects, which can be realized in constant stress conditions (rSME), or in stress-free conditions (reversible bidirectional shape-memory effect (rbSME)). Furthermore, magnetically actuated SMPs and shape-memory hydrogels (SMHs) are described to show the potential of the SMP technology in biomedical applications and multifunctional approaches.},
  language  = {en}
}
@article{FolikumahNeffeBehletal.2019,
  author    = {Folikumah, Makafui Yao and Neffe, Axel T. and Behl, Marc and Lendlein, Andreas},
  title     = {Thiol Michael-Type reactions of optically active mercapto-acids in aqueous medium},
  series = {MRS advances : a journal of the Materials Research Society},
  volume    = {4},
  journal   = {MRS advances : a journal of the Materials Research Society},
  number    = {46-47},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.308},
  pages     = {2515 -- 2525},
  year      = {2019},
  abstract  = {Defined chemical reactions in a physiological environment are a prerequisite for the in situ synthesis of implant materials potentially serving as matrix for drug delivery systems, tissue fillers or surgical glues. 'Click' reactions like thiol Michael-type reactions have been successfully employed as bioorthogonal reaction. However, due to the individual stereo-electronic and physical properties of specific substrates, an exact understanding their chemical reactivity is required if they are to be used for in-situ biomaterial synthesis. The chiral (S)-2-mercapto-carboxylic acid analogues of L-phenylalanine (SH-Phe) and L-leucine (SH-Leu) which are subunits of certain collagenase sensitive synthetic peptides, were explored for their potential for in-situ biomaterial formation via the thiol Michael-type reaction. In model reactions were investigated the kinetics, the specificity and influence of stereochemistry of this reaction. We could show that only reactions involving SH-Leu yielded the expected thiol-Michael product. The inability of SH-Phe to react was attributed to the steric hindrance of the bulky phenyl group. In aqueous media, successful reaction using SH-Leu is thought to proceed via the sodium salt formed in-situ by the addition of NaOH solution, which was intented to aid the solubility of the mercapto-acid in water. Fast reaction rates and complete acrylate/maleimide conversion were only realized at pH 7.2 or higher suggesting the possible use of SH-Leu under physiological conditions for thiol Michael-type reactions. This method of in-situ formed alkali salts could be used as a fast approach to screen mercapto-acids for thio Michael-type reactions without the synthesis of their corresponding esters.},
  language  = {en}
}
@article{FriessWischkeLendlein2019,
  author    = {Friess, Fabian and Wischke, Christian and Lendlein, Andreas},
  title     = {Microscopic analysis of shape-shiftable oligo(epsilon-caprolactone)-based particles},
  series = {MRS advances},
  volume    = {4},
  journal   = {MRS advances},
  number    = {59-60},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.392},
  pages     = {3199 -- 3206},
  year      = {2019},
  abstract  = {Spherical particles are routinely monitored and described by hydrodynamic diameters determined, e.g., by light scattering techniques. Non-spherical particles such as prolate ellipsoids require alternative techniques to characterize particle size as well as particle shape. In this study, oligo(epsilon-caprolactone) (oCL) based micronetwork (MN) particles with a shape-shifting function based on their shape-memory capability were programmed from spherical to prolate ellipsoidal shape aided by incorporation and stretching in a water-soluble phantom matrix. By applying light microscopy with automated contour detection and aspect ratio analysis, differences in characteristic aspect ratio distributions of non-crosslinked microparticles (MPs) and crosslinked MNs were detected when the degrees of phantom elongation (30-290\%) are increased. The thermally induced shape recovery of programmed MNs starts in the body rather than from the tips of ellipsoids, which may be explained based on local differences in micronetwork deformation. By this approach, fascinating intermediate particle shapes with round bodies and two opposite sharp tips can be obtained, which could be of interest, e.g., in valves or other technical devices, in which the tips allow to temporarily encage the switchable particle in the desired position.},
  language  = {en}
}
@article{VogelEbelHecketal.2019,
  author    = {Vogel, Stefanie and Ebel, Kenny and Heck, Christian and Sch{\"u}rmann, Robin Mathis and Milosavljevic, Aleksandar R. and Giuliani, Alexandre and Bald, Ilko},
  title     = {Vacuum-UV induced DNA strand breaks},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {21},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {4},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c8cp06813e},
  pages     = {1972 -- 1979},
  year      = {2019},
  abstract  = {Radiation therapy is a basic part of cancer treatment. To increase the DNA damage in carcinogenic cells and preserve healthy tissue at the same time, radiosensitizing molecules such as halogenated nucleobase analogs can be incorporated into the DNA during the cell reproduction cycle. In the present study 8.44 eV photon irradiation induced single strand breaks (SSB) in DNA sequences modified with the radiosensitizer 5-bromouracil (U-5Br) and 8-bromoadenine ((8Br)A) are investigated. U-5Br was incorporated in the 13mer oligonucleotide flanked by different nucleobases. It was demonstrated that the highest SSB cross sections were reached, when cytosine and thymine were adjacent to U-5Br, whereas guanine as a neighboring nucleobase decreases the activity of U-5Br indicating that competing reaction mechanisms are active. This was further investigated with respect to the distance of guanine to U-5Br separated by an increasing number of adenine nucleotides. It was observed that the SSB cross sections were decreasing with an increasing number of adenine spacers between guanine and U-5Br until the SSB cross sections almost reached the level of a non-modified DNA sequence, which demonstrates the high sequence dependence of the sensitizing effect of U-5Br. (8Br)A was incorporated in a 13mer oligonucleotide as well and the strand breaks were quantified upon 8.44 eV photon irradiation in direct comparison to a non-modified DNA sequence of the same composition. No clear enhancement of the SSB yield of the modified in comparison to the non-modified DNA sequence could be observed. Additionally, secondary electrons with a maximum energy of 3.6 eV were generated when using Si as a substrate giving rise to further DNA damage. A clear enhancement in the SSB yield can be ascertained, but to the same degree for both the non-modified DNA sequence and the DNA sequence modified with (8Br)A.},
  language  = {en}
}
@article{PoghosyanAdamyanShahinyanetal.2019,
  author    = {Poghosyan, Armen H. and Adamyan, Maksim P. and Shahinyan, Aram A. and Koetz, Joachim},
  title     = {AOT Bilayer Adsorption on Gold Surfaces},
  series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry},
  volume    = {123},
  journal   = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry},
  number    = {4},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1520-6106},
  doi       = {10.1021/acs.jpcb.8b11471},
  pages     = {948 -- 953},
  year      = {2019},
  abstract  = {A molecular dynamics study was done to reveal the adsorption properties of sodium dioctyl sulfosuccinate (AOT) bilayers on gold Au(111) surfaces. Examining the rotational mobility of AOT molecules, we track that the correlation time of AOT molecules on the adsorbed layer is much higher. The data estimating the diffusive motion of AOT molecule show a substantially lower rate of diffusion (similar to 10(-10) cm(2)/s) in the adsorbed layers in comparison to other ones. The results show that an adsorbed layer is more rigid, whereas the outer layers undergo considerable lateral and vertical fluctuations.},
  language  = {en}
}