@article{MachatschekSchoeneRaschdorfetal.2019,
  author    = {Machatschek, Rainhard Gabriel and Sch{\"o}ne, Anne-Christin and Raschdorf, Elisa and Ihlenburg, Ramona and Schulz, Burkhard and Lendlein, Andreas},
  title     = {Interfacial properties of morpholine-2,5-dione-based oligodepsipeptides and multiblock copolymers},
  series = {MRS Communications},
  volume    = {9},
  journal   = {MRS Communications},
  number    = {1},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {2159-6859},
  doi       = {10.1557/mrc.2019.21},
  pages     = {170 -- 180},
  year      = {2019},
  abstract  = {Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air-water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air-water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.},
  language  = {en}
}
@misc{MachatschekSchoeneRaschdorfetal.2019,
  author    = {Machatschek, Rainhard Gabriel and Sch{\"o}ne, Anne-Christin and Raschdorf, Elisa and Ihlenburg, Ramona and Schulz, Burkhard and Lendlein, Andreas},
  title     = {Interfacial properties of morpholine-2,5-dione-based oligodepsipeptides and multiblock copolymers},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1106},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-46975},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469755},
  pages     = {170 -- 180},
  year      = {2019},
  abstract  = {Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air-water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air-water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.},
  language  = {en}
}
@article{PilusoVukicevieNoecheletal.2018,
  author    = {Piluso, Susanna and Vukicevie, Radovan and N{\"o}chel, Ulrich and Braune, Steffen and Lendlein, Andreas and Neffe, Axel T.},
  title     = {Sequential alkyne-azide cycloadditions for functionalized gelatin hydrogel formation},
  series = {European polymer journal},
  volume    = {100},
  journal   = {European polymer journal},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2018.01.017},
  pages     = {77 -- 85},
  year      = {2018},
  abstract  = {While click chemistry reactions for biopolymer network formation are attractive as the defined reactions may allow good control of the network formation and enable subsequent functionalization, tailoring of gelatin network properties over a wide range of mechanical properties has yet to be shown. Here, it is demonstrated that copper-catalyzed alkyne-azide cycloaddition of alkyne functionalized gelatin with diazides gave hydrogel networks with properties tailorable by the ratio of diazide to gelatin and diazide rigidity. 4,4′-diazido-2,2′-stilbenedisulfonic acid, which has been used as rigid crosslinker, yielded hydrogels with Young's moduli E of 50-390 kPa and swelling degrees Q of 150-250 vol.\%, while the more flexible 1,8-diazidooctane resulted in hydrogels with E = 125-280 kPa and Q = 225-470 vol.\%. Storage moduli could be varied by two orders of magnitude (G′ = 100-20,000 Pa). An indirect cytotoxicity test did not show cytotoxic properties. Even when employing 1:1 ratios of alkyne and azide moieties, the hydrogels were shown to contain both, unreacted alkyne groups on the gelatin backbone as well as dangling chains carrying azide groups as shown by reaction with functionalized fluorescein. The free groups, which can be tailored by the employed ratio of the reactants, are accessible for covalent attachment of drugs, as was demonstrated by functionalization with dexamethasone. The sequential network formation and functionalization with click chemistry allows access to multifunctional materials relevant for medical applications.},
  language  = {en}
}
@article{LuetzowHommesSchattmannNeffeetal.2018,
  author    = {L{\"u}tzow, Karola and Hommes-Schattmann, Paul J. and Neffe, Axel T. and Ahmad, Bilal and Williams, Gareth R. and Lendlein, Andreas},
  title     = {Perfluorophenyl azide functionalization of electrospun poly(para-dioxanone)},
  series = {Polymers for advanced technologies},
  volume    = {30},
  journal   = {Polymers for advanced technologies},
  number    = {5},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {1042-7147},
  doi       = {10.1002/pat.4331},
  pages     = {1165 -- 1172},
  year      = {2018},
  abstract  = {Strategies to surface-functionalize scaffolds by covalent binding of biologically active compounds are of fundamental interest to control the interactions between scaffolds and biomolecules or cells. Poly(para-dioxanone) (PPDO) is a clinically established polymer that has shown potential as temporary implant, eg, for the reconstruction of the inferior vena cava, as a nonwoven fiber mesh. However, PPDO lacks suitable chemical groups for covalent functionalization. Furthermore, PPDO is highly sensitive to hydrolysis, reflected by short in vivo half-life times and degradation during storage. Establishing a method for covalent functionalization without degradation of this hydrolyzable polymer is therefore important to enable the surface tailoring for tissue engineering applications. It was hypothesized that treatment of PPDO with an N-hydroxysuccinimide ester group bearing perfluorophenyl azide (PFPA) under UV irradiation would allow efficient surface functionalization of the scaffold. X-ray photoelectron spectroscopy and attenuated total reflectance Fourier-transformed infrared spectroscopy investigation revealed the successful binding, while a gel permeation chromatography study showed that degradation did not occur under these conditions. Coupling of a rhodamine dye to the N-hydroxysuccinimide esters on the surface of a PFPA-functionalized scaffold via its amine linker showed a homogenous staining of the PPDO in laser confocal microscopy. The PFPA method is therefore applicable even to the surface functionalization of hydrolytically labile polymers, and it was demonstrated that PFPA chemistry may serve as a versatile tool for the (bio-)functionalization of PPDO scaffolds.},
  language  = {en}
}
@article{TronciNeffePierceetal.2010,
  author    = {Tronci, Giuseppe and Neffe, Axel T. and Pierce, Benjamin Franklin and Lendlein, Andreas},
  title     = {An entropy-elastic gelatin-based hydrogel system},
  issn      = {0959-9428},
  doi       = {10.1039/C0jm00883d},
  year      = {2010},
  abstract  = {Gelatin is a non-immunogenic and degradable biopolymer, which is widely applied in the biomedical field e. g. for drug capsules or as absorbable hemostats. However, gelatin materials present limited and hardly reproducible mechanical properties especially in aqueous systems, particularly caused by the uncontrollable partial renaturation of collagen-like triple helices. Therefore, mechanically demanding applications for gelatin-based materials, such as vascular patches, i.e. hydrogel films that seal large incisions in vessel walls, and for induced autoregeneration, are basically excluded if this challenge is not addressed. Through the synthesis of a defined chemical network of gelatin with hexamethylene diisocyanate (HDI) in DMSO, the self-organization of gelatin chains could be hindered and amorphous gelatin films were successfully prepared having Young's moduli of 60-530 kPa. Transferring the crosslinking reaction with HDI and, alternatively, ethyl lysine diisocyanate (LDI), to water as reaction medium allowed the tailoring of swelling behaviour and mechanical properties by variation of crosslinker content while suppressing the formation of helices. The hydrogels had Young's moduli of 70-740 kPa, compressive moduli of 16-48 kPa, and degrees of swelling of 300-800 vol\%. Test reactions investigated by ESI mass spectrometry allowed the identification and quantification of reaction products of the crosslinking reaction. The HDI crosslinked networks were stabilized by direct covalent crosslinks (ca. 10 mol\%), supported by grafting (50 mol\%) and blending of hydrophobic oligomeric chains. For the LDI- based networks, less crosslinked (3 mol\%) and grafted species (5 mol\%) and much higher amounts of oligomers were observed. The adjustable hydrogel system enables the application of gelatin-based materials in physiological environments.},
  language  = {en}
}
@article{vonRuestenLangeLuetzowNeffeetal.2012,
  author    = {von R{\"u}sten-Lange, Maik and Luetzow, Karola and Neffe, Axel T. and Lendlein, Andreas},
  title     = {Characterization of oligo(ethylene glycol) and oligoglycerol functionalized poly(ether imide) by angle-dependent X-ray photoelectron spectroscopy},
  series = {Journal of applied biomaterials \& functional materials},
  volume    = {10},
  journal   = {Journal of applied biomaterials \& functional materials},
  number    = {3},
  publisher = {Wichtig},
  address   = {Milano},
  issn      = {2280-8000},
  doi       = {10.5301/JABFM.2012.10345},
  pages     = {215 -- 222},
  year      = {2012},
  abstract  = {Purpose: Previous investigations have shown that poly(ether imide) (PEI) membranes can be functionalized with aminated macromolecules. In this study we explored whether the characterization of PEI functionalized with oligo(ethylene glycol) (OEG) or linear, side chain methylated oligoglycerols (OGMe), by angle-dependent X-ray induced photoelectron spectroscopy (XPS) can be used to prove the functionalization, give insight into the reaction mechanism and reveal the spatial distribution of the grafts. Methods: PEI membranes were functionalized under alkaline conditions using an aqueous solution with 2 wt\% of alpha-amino-methoxy oligo(ethylene glycol) (M-n = 1,320 g.mol(-1)) or linear, side chain methylated monoamine oligoglycerols (M-n = 1,120, 1,800 or 2,270 g.mol(-1)), respectively. The functionalized membranes were investigated using XPS measurements at different detector angles to enable comparison between the signals related to the bulk and surface volume and were compared with untreated and alkaline-treated PEI membranes. Results: While at a perpendicular detector angle the bulk signals of the PEI were prominent, at larger surface volume-related detector angles, the signals for OGMe and OEG were determinable. Conclusion: The surface functionalization of PEI with OEG and OGMe could be verified by the angle-dependent XPS. The observations proved the functionalization at the PEI surface, as the polyethers were detected at angles providing signals of the surface volume. Furthermore, the chemical functions determined verified a covalent binding via the nucleophilic addition of the amine functionalized OGMe and OEG to the PEI imide function.},
  language  = {en}
}
@article{ZaupaNeffePierceetal.2011,
  author    = {Zaupa, Alessandro and Neffe, Axel T. and Pierce, Benjamin F. and Lendlein, Andreas and Hofmann, Dieter},
  title     = {A molecular dynamic analysis of gelatin as an amorphous material Prediction of mechanical properties of gelatin systems},
  series = {The international journal of artificial organs},
  volume    = {34},
  journal   = {The international journal of artificial organs},
  number    = {2},
  publisher = {Wichtig},
  address   = {Milano},
  issn      = {0391-3988},
  doi       = {10.5301/IJAO.2010.6083},
  pages     = {139 -- 151},
  year      = {2011},
  abstract  = {Biomaterials are used in regenerative medicine for induced autoregeneration and tissue engineering. This is often challenging, however, due to difficulties in tailoring and controlling the respective material properties. Since functionalization is expected to offer better control, in this study gelatin chains were modified with physically interacting groups based on tyrosine with the aim of causing the formation of physical crosslinks. This method permits application-specific properties like swelling and better tailoring of mechanical properties. The design of the crosslink strategy was supported by molecular dynamic (MD) simulations of amorphous bulk models for gelatin and functionalized gelatins at different water contents (0.8 and 25 wt.-\%). The results permitted predictions to be formulated about the expected crosslink density and its influence on equilibrium swelling behavior and on elastic material properties. The models of pure gelatin were used to validate the strategy by comparison between simulated and experimental data such as density, backbone conformation angle distribution, and X-ray scattering spectra. A key result of the simulations was the prediction that increasing the number of aromatic functions attached to the gelatin chain leads to an increase in the number of physical netpoints observed in the simulated bulk packing models. By comparison with the Flory-Rehner model, this suggested reduced equilibrium swelling of the functionalized materials in water, a prediction that was subsequently confirmed by our experimental work. The reduction and control of the equilibrium degree of swelling in water is a key criterion for the applicability of functionalized gelatins when used, for example, as matrices for induced autoregeneration of tissues.},
  language  = {en}
}
@article{ZhangRešetičBehletal.2021,
  author    = {Zhang, Pengfei and Rešetič, Andraž and Behl, Marc and Lendlein, Andreas},
  title     = {Multifunctionality in polymer networks by dynamic of coordination bonds},
  series = {Macromolecular chemistry and physics},
  volume    = {222},
  journal   = {Macromolecular chemistry and physics},
  number    = {3},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1521-3935},
  doi       = {10.1002/macp.202000394},
  pages     = {11},
  year      = {2021},
  abstract  = {The need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self-healing capability, fluorescence stimuli-responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)-phosphine coordination bonds, which in a polymer network act with their dynamic and non-covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium-phosphine ions across and through contacting areas of the material provide for reshaping and self-healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material-sensing capabilities.},
  language  = {en}
}
@article{SauterKratzFarhanetal.2022,
  author    = {Sauter, Tilman and Kratz, Karl and Farhan, Muhammad and Heuchel, Matthias and Lendlein, Andreas},
  title     = {Design and fabrication of fiber mesh actuators},
  series = {Applied materials today},
  volume    = {29},
  journal   = {Applied materials today},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2352-9407},
  doi       = {10.1016/j.apmt.2022.101562},
  pages     = {13},
  year      = {2022},
  abstract  = {Soft actuator performance can be tuned by chemistry or mechanical manipulation, but this adjustability is limited especially in view of their growing technological relevance. Inspired from textile engineering, we designed and fabricated fiber mesh actuators and introduced new features like anisotropic behavior and soft-tissue like elastic deformability. Design criteria for the meshes are the formation of fiber bundles, the angle between fiber bundles in different stacked layers and covalent crosslinks forming within and between fibers at their interfacial contact areas. Through crosslinking the interfiber bond strength increased from a bond transmitting neither axial nor rotational loads (pin joint) to a bond strength capable of both (welded joint). For non-linear elastic stiffening, stacked fiber bundles with four embracing fibers were created forming microstructural rhombus shapes. Loading the rhombus diagonally allowed generation of "soft tissue"-like mechanics. By adjustment of stacking angles, the point of strong increase in stress is tuned. While the highest stresses are observed in aligned and crosslinked fiber mats along the direction of the fiber, the strongest shape-memory actuation behavior is found in randomly oriented fiber mats. Fiber mesh actuators controlled by temperature are of high significance as soft robot skins and as for active patches supporting tissue regeneration.},
  language  = {en}
}
@article{TartivelBlockiBrauneetal.2022,
  author    = {Tartivel, Lucile and Blocki, Anna M. and Braune, Steffen and Jung, Friedrich and Behl, Marc and Lendlein, Andreas},
  title     = {An Inverse shape-memory hydrogel scaffold switching upon cooling in a tissue-tolerated temperature range},
  series = {Advanced materials interfaces},
  volume    = {9},
  journal   = {Advanced materials interfaces},
  number    = {6},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {2196-7350},
  doi       = {10.1002/admi.202101588},
  pages     = {9},
  year      = {2022},
  abstract  = {Tissue reconstruction has an unmet need for soft active scaffolds that enable gentle loading with regeneration-directing bioactive components by soaking up but also provide macroscopic dimensional stability. Here microporous hydrogels capable of an inverse shape-memory effect (iSME) are described, which in contrast to classical shape-memory polymers (SMPs) recover their permanent shape upon cooling. These hydrogels are designed as covalently photo cross-linked polymer networks with oligo(ethylene glycol)-oligo(propylene glycol)-oligo(ethylene glycol) (OEG-OPG-OEG) segments. When heated after deformation, the OEG-OPG-OEG segments form micelles fixing the temporary shape. Upon cooling, the micelles dissociate again, the deformation is reversed and the permanent shape is obtained. Applicability of this iSME is demonstrated by the gentle loading of platelet-rich plasma (PRP) without causing any platelet activation during this process. PRP is highly bioactive and is widely acknowledged for its regenerative effects. Hence, the microporous inverse shape-memory hydrogel (iSMH) with a cooling induced pore-size effect represents a promising candidate scaffold for tissue regeneration for potential usage in minimally invasive surgery applications.},
  language  = {en}
}