@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{PilusoLendleinNeffe2017,
  author    = {Piluso, Susanna and Lendlein, Andreas and Neffe, Axel T.},
  title     = {Enzymatic action as switch of bulk to surface degradation of clicked gelatin-based networks},
  series = {Polymers for advanced technologies},
  volume    = {28},
  journal   = {Polymers for advanced technologies},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {1042-7147},
  doi       = {10.1002/pat.3962},
  pages     = {1318 -- 1324},
  year      = {2017},
  abstract  = {Polymer degradation occurs under physiological conditions in vitro and in vivo, especially when bonds susceptible to hydrolysis are present in the polymer. Understanding of the degradation mechanism, changes of material properties over time, and overall rate of degradation is a necessary prerequisite for the knowledge-based design of polymers with applications in biomedicine. Here, hydrolytic degradation studies of gelatin-based networks synthesized by copper-catalyzed azide-alkyne cycloaddition reaction are reported, which were performed with or without addition of an enzyme. In all cases, networks with a stilbene as crosslinker proofed to be more resistant to degradation than when an octyl diazide was used. Without addition of an enzyme, the rate of degradation was ruled by the crosslinking density of the network and proceeded via a bulk degradation mechanism. Addition of Clostridium histolyticum collagenase resulted in a much enhanced rate of degradation, which furthermore occurred via surface erosion. The mesh size of the hydrogels (>7nm) was in all cases larger than the hydrodynamic radius of the enzyme (4.5nm) so that even in very hydrophilic networks with large mesh size enzymes may be used to induce a fast surface degradation mechanism. This observation is of general interest when designing hydrogels to be applied in the presence of enzymes, as the degradation mechanism and material performance are closely interlinked. Copyright (c) 2016 John Wiley \& Sons, Ltd.},
  language  = {en}
}
@article{AdelsbergerBivigouKoumbaMiasnikovaetal.2015,
  author    = {Adelsberger, Joseph and Bivigou Koumba, Achille Mayelle and Miasnikova, Anna and Busch, Peter and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.},
  title     = {Polystyrene-block-poly (methoxy diethylene glycol acrylate)-block-polystyrene triblock copolymers in aqueous solution-a SANS study of the temperature-induced switching behavior},
  series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft},
  volume    = {293},
  journal   = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft},
  number    = {5},
  publisher = {Springer},
  address   = {New York},
  issn      = {0303-402X},
  doi       = {10.1007/s00396-015-3535-6},
  pages     = {1515 -- 1523},
  year      = {2015},
  abstract  = {A concentrated solution of a symmetric triblock copolymer with a thermoresponsive poly(methoxy diethylene glycol acrylate) (PMDEGA) middle block and short hydrophobic, fully deuterated polystyrene end blocks is investigated in D2O where it undergoes a lower critical solution temperature-type phase transition at ca. 36 A degrees C. Small-angle neutron scattering (SANS) in a wide temperature range (15-50 A degrees C) is used to characterize the size and inner structure of the micelles as well as the correlation between the micelles and the formation of aggregates by the micelles above the cloud point (CP). A model featuring spherical core-shell micelles, which are correlated by a hard-sphere potential or a sticky hard-sphere potential together with a Guinier form factor describing aggregates formed by the micelles above the CP, fits the SANS curves well in the entire temperature range. The thickness of the thermoresponsive micellar PMDEGA shell as well as the hard-sphere radius increase slightly already below the cloud point. Whereas the thickness of the thermoresponsive micellar shell hardly shrinks when heating through the CP and up to 50 A degrees C, the hard-sphere radius decreases within 3.5 K at the CP. The volume fraction decreases already significantly below the CP, which may be at the origin of the previously observed gel-sol transition far below the CP (Miasnikova et al., Langmuir 28: 4479-4490, 2012). Above the CP, small, and at higher temperatures, large aggregates are formed by the micelles.},
  language  = {en}
}
@article{PilusoHieblGorbetal.2011,
  author    = {Piluso, Susanna and Hiebl, Bernhard and Gorb, Stanislav N. and Kovalev, Alexander and Lendlein, Andreas and Neffe, Axel T.},
  title     = {Hyaluronic acid-based hydrogels crosslinked by copper-catalyzed azide-alkyne cycloaddition with tailorable mechanical properties},
  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.2011.6394},
  pages     = {192 -- 197},
  year      = {2011},
  abstract  = {Biopolymers of the extracellular matrix are attractive starting materials for providing degradable and biocompatible biomaterials. In this study, hyaluronic acid-based hydrogels with tunable mechanical properties were prepared by the use of copper-catalyzed azide-alkyne cycloaddition (known as "click chemistry"). Alkyne-functionalized hyaluronic acid was crosslinked with linkers having two terminal azide functionalities, varying crosslinker density as well as the lengths and rigidity of the linker molecules. By variation of the crosslinker density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-4 kPa were prepared. The washed materials contained a maximum of 6.8 mg copper per kg dry weight and the eluate of the gel crosslinked with diazidostilbene did not show toxic effects on L929 cells. The hyaluronic acid-based hydrogels have potential as biomaterials for cell culture or soft tissue regeneration applications.},
  language  = {en}
}
@article{BertzWoehlBruhnMietheetal.2013,
  author    = {Bertz, Andreas and W{\"o}hl-Bruhn, Stefanie and Miethe, Sebastian and Tiersch, Brigitte and Koetz, Joachim and Hust, Michael and Bunjes, Heike and Menzel, Henning},
  title     = {Encapsulation of proteins in hydrogel carrier systems for controlled drug delivery influence of network structure and drug size on release rate},
  series = {Journal of biotechnology},
  volume    = {163},
  journal   = {Journal of biotechnology},
  number    = {2},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0168-1656},
  doi       = {10.1016/j.jbiotec.2012.06.036},
  pages     = {243 -- 249},
  year      = {2013},
  abstract  = {Novel hydrogels based on hydroxyethyl starch modified with polyethylene glycol methacrylate (HES-P(EG)(6)MA) were developed as delivery system for the controlled release of proteins. Since the drug release behavior is supposed to be related to the pore structure of the hydrogel network the pore sizes were determined by cryo-SEM, which is a mild technique for imaging on a nanometer scale. The results showed a decreasing pore size and an increase in pore homogeneity with increasing polymer concentration. Furthermore, the mesh sizes of the hydrogels were calculated based on swelling data. Pore and mesh size were significantly different which indicates that both structures are present in the hydrogel. The resulting structural model was correlated with release data for bulk hydrogel cylinders loaded with FITC-dextran and hydrogel microspheres loaded with FITC-IgG and FITC-dextran of different molecular size. The initial release depended much on the relation between hydrodynamic diameter and pore size while the long term release of the incorporated substances was predominantly controlled by degradation of the network of the much smaller meshes.},
  language  = {en}
}
@article{ZhongAdelsbergerNiedermeieretal.2013,
  author    = {Zhong, Qi and Adelsberger, Joseph and Niedermeier, M. A. and Golosova, Anastasi and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Funari, S. S. and Papadakis, Christine M. and M{\"u}ller-Buschbaum, Peter},
  title     = {The influence of selective solvents on the transition behavior of poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) thick films},
  series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft},
  volume    = {291},
  journal   = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft},
  number    = {6},
  publisher = {Springer},
  address   = {New York},
  issn      = {0303-402X},
  doi       = {10.1007/s00396-012-2879-4},
  pages     = {1439 -- 1451},
  year      = {2013},
  abstract  = {Thick poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) [P(S-b-MDEGA-b-S)] films (thickness 5 mu m) are prepared from different solvents on flexible substrates by solution casting and investigated with small-angle X-ray scattering. As the solvents are either PS- or PMDEGA-selective, micelles with different core-shell micellar structures are formed. In PMDEGA-selective solvents, the PS block is the core and PMDEGA is the shell, whereas in PS-selective solvents, the order is reversed. After exposing the films to liquid D2O, the micellar structure inside the films prepared from PMDEGA-selective solvents remains unchanged and only the PMDEGA (shell part) swells. On the contrary, in the films prepared from PS-selective solvents, the micelles revert the core and the shell. This reversal causes more entanglements of the PMDEGA chains between the micelles. Moreover, the thermal collapse transition of the PMDEGA block in liquid D2O is significantly broadened. Irrespective of the solvent used for film preparation, the swollen PMDEGA shell does not show a prominent shrinkage when passing the phase transition, and the transition process occurs via compaction. The collapsed micelles have a tendency to densely pack above the transition temperature.},
  language  = {en}
}