Two‐photon polymerization (2PP) is a lithography‐based 3D printing method allowing the fabrication of 3D structures with sub‐micrometer resolution. This work focuses on the characterization of gelatin–norbornene (Gel–NB) bioinks which enables the embedding of cells via 2PP. The high reactivity of the thiol‐ene system allows 2PP processing of cell‐containing materials at remarkably high scanning speeds (1000 mm s−1) placing this technology in the domain of bioprinting. Atomic force microscopy results demonstrate that the indentation moduli of the produced hydrogel constructs can be adjusted in the 0.2–0.7 kPa range by controlling the 2PP processing parameters. Using this approach gradient 3D constructs are produced and the morphology of the embedded cells is observed in the course of 3 weeks. Furthermore, it is possible to tune the enzymatic degradation of the crosslinked bioink by varying the applied laser power. The 3D printed Gel–NB hydrogel constructs show exceptional biocompatibility, supported cell adhesion, and migration. Furthermore, cells maintain their proliferation capacity demonstrated by Ki‐67 immunostaining. Moreover, the results demonstrate that direct embedding of cells provides uniform distribution and high cell loading independently of the pore size of the scaffold. The investigated photosensitive bioink enables high‐definition bioprinting of well‐defined constructs for long‐term cell culture studies.

TailingReversible protection MALDI Resistant subpopulation a b s t r a c tThis study investigates the mechanisms underlying the deviation from ChickeWatson kinetics, namely a tailing curve, during the disinfection of viruses by chlorine dioxide (ClO 2 ). Tailing has been previously reported, but is typically attributed to the decay in disinfectant concentration. Herein, it is shown that tailing occurs even at constant ClO 2 concentrations. Four working hypothesis to explain the cause of tailing were tested, specifically changes in the solution's disinfecting capacity, aggregation of viruses, resistant virus subpopulations, and changes in the virus properties during disinfection. In experiments using MS2 as a model virus, it was possible to rule out the solution's disinfecting capacity, virus aggregation and the resistant subpopulation as reasons for tailing. Instead, the cause for tailing is the deposition of an adduct onto the virus capsid over the course of the experiment, which protects the viruses. This adduct could easily be removed by washing, which restored the susceptibility of the viruses to ClO 2 . This finding highlights an important shortcoming of ClO 2 , namely its self-limiting effect on virus disinfection. It is important to take this effect into account in treatment applications to ensure that the water is sufficiently disinfected before human consumption. ª 2013 Elsevier Ltd. All rights reserved. IntroductionChlorination is among the oldest and most commonly used disinfection process worldwide. However, over the years it has been shown that chlorine produces harmful by-products such as trihalomethanes and other halogenated compounds with potential carcinogenic effects (Xie, 2004). It is therefore of interest to investigate other disinfectants that have a similar disinfection potential but generate fewer problematic byproducts. As a good alternative, chlorine dioxide (ClO 2 ) has shown to efficiently disinfect water for human consumption (Huang et al., 1997;Jin et al., 2013;Zoni et al., 2007).Importantly, it is effective at inactivating Cryptosporidium, whereas free chlorine is not (Chauret et al., 2001). Except from exhibiting a good disinfection capacity, ClO 2 can also oxidize iron and manganese, as well as help controlling taste and odor compounds (Aieta and Berg, 1986;Li et al., 1996). The disadvantage of using chlorine dioxide is that it reacts to chlorite, which may be neurotoxic at high doses (Xie, 2004). In 1908, Chick published the first model for describing bacteria inactivation by disinfecting agents (Chick, 1908) Available online at www.sciencedirect.com journal homepage: www.else vier.com/locate /wa tres w a t e r r e s e a r c h 4 8 ( 2 0 1 4 ) 8 2 e8 90043-1354/$ e see front matter ª

Thermoplastic polyurethane elastomers (TPUs) with a biodegradable chain extender and different nonaromatic diisocyanate hard segments were synthesized and tested concerning their thermal, mechanical, and degradation properties and for their processability regarding electrospinning. The design of the TPUs was based on the structural modification of the hard segment using linear aliphatic hexamethylene diisocyanate (HMDI), more rigid alicyclic 4,4′‐methylene bis(cyclohexylisocyanate) (H12MDI), 1,3‐bis(isocyanatomethyl)cyclohexane (BIMC), or isophorone diisocyanate (IPDI). The soft segment consisted of poly(tetrahydrofuran). Bis(2‐hydroxyethyl) terephthalate (BET) was used as chain extender with cleavable ester bonds. Some of the polyurethanes based on alicyclic diisocyanate showed better mechanical performance than the less rigid HMDI‐based TPU. The TPU in vitro degradability was tested for 25 days at elevated temperatures in PBS buffer and indicated a bulk erosion process. Electrospinning experiments were conducted and promising results with respect to further applicability of these materials in vascular tissue engineering were obtained. © 2018 The Authors Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2214–2224