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1. Mechanically adaptive implants fabricated with poly(2-hydroxyethyl methacrylate)-based negative photoresists

   https://doi.org/10.1039/D0TB00980F  

   Monney, Baptiste; Hess-Dunning, Allison E.; Gloth, Paul; Capadona, Jeffrey R.; Weder, Christoph (January 2020, Journal of Materials Chemistry B)

   Neural implants that are based on mechanically adaptive polymers (MAPs) and soften upon insertion into the body have previously been demonstrated to elicit a reduced chronic tissue response than more rigid devices fabricated from silicon or metals, but their processability has been limited. Here we report a negative photoresist approach towards physiologically responsive MAPs. We exploited this framework to create cross-linked terpolymers of 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate and 2-ethylhexyl methacrylate by photolithographic processes. Our systematic investigation of this platform afforded an optimized composition that exhibits a storage modulus E ′ of 1.8 GPa in the dry state. Upon exposure to simulated physiological conditions the material swells slightly (21% w/w) leading to a reduction of E ′ to 2 MPa. The large modulus change is mainly caused by plasticization, which shifts the glass transition from above to below 37 °C. Single shank probes fabricated by photolithography could readily be implanted into a brain-mimicking gel without buckling and viability studies with microglial cells show that the materials display excellent biocompatibility. 

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2. Bottlebrush Hydrogels with Hidden Length: Super‐Swelling and Mechanically Robust

   https://doi.org/10.1002/adfm.202410905  

   Wang, Claire J; Vashahi, Foad; Moutsios, Ioannis; Umarov, Akmal Z; Ageev, Georgiy G; Wang, Zilu; Ivanov, Dimitri A; Dobrynin, Andrey V; Sheiko, Sergei S (August 2024, Advanced Functional Materials)

   Abstract Hydrogels are explored for applications in agriculture, water purification, and biomedicine, leveraging softness, elasticity, and high water uptake. However, hydrogels are notoriously brittle, especially at high water content. This shortcoming puts the improvement of hydrogel mechanics at the forefront of current research. Yet modern strategies for enhancing gel resilience come at the expense of softness and swelling. This problem is addressed using bottlebrush networks with disentangled strands and hidden length reservoirs, which synergistically enhance gel swelling and robustness while maintaining their softness. Implementing a facile one‐pot synthesis of single‐stranded bottlebrush networks with a relatively hydrophobic poly(2‐hydroxyethyl methacrylate) (PHEMA) backbone and hydrophilic poly(2‐methyl‐2‐oxazoline) (PMOx) side chains, hydrogels are prepared with a modulus below <1 kPa and swelling ratios up to 125 that can withstand up to 10‐fold extension. 

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3. Effect of the solvent on the conformation of monocrotaline as determined by isotropic and anisotropic NMR parameters

   https://doi.org/10.1002/mrc.4968  

   de_Melo_Sousa, Cleyton_Marcos; Giordani, Raquel_Brandt; de_Almeida, Wamberto_Alristenio_Moreira; Griesinger, Christian; Gil, Roberto_R; Navarro‐Vázquez, Armando; Hallwass, Fernando (December 2019, Magnetic Resonance in Chemistry)

   Abstract The conformation in solution of monocrotaline, a pyrrolizidine alkaloid presenting an eleven‐membered macrocyclic diester ring, has been investigated using a combination of isotropic and anisotropic nuclear magnetic resonance parameters measured in four solvents of different polarity (D₂O, DMSO‐d₆, CDCl₃, and C₆D₆). Anisotropic nuclear magnetic resonance parameters were measured in different alignment media, based on their compatibility with the solvent of interest: cromoglycate liquid crystal solution was used for D₂O, whereas a poly (methyl methacrylate) polymer gel was chosen for CDCl₃and C₆D₆, and a poly (hydroxyethyl methacrylate) gel for DMSO‐d₆. Whereas the pyrrolizidine ring shows anE₆exo‐puckered conformation in all of the solvents, the macrocyclic eleven‐membered ring adopts different populations ofsyn‐parallel andanti‐parallel relative orientation of the carbonyl groups according to the polarity of the solvent. 

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4. Nematic colloids at liquid crystal–air interfaces via photopolymerization

   https://doi.org/10.1039/d0sm01311k  

   Wei, Xiaoshuang; Sbalbi, Nicholas; Bradley, Laura C. (October 2020, Soft Matter)

   null (Ed.)

   We demonstrate the preparation of colloidal crystals at nematic liquid crystal–air interfaces by simultaneous photopolymerization and assembly. Polymer colloids are produced by polymerization-induced phase separation of 2-hydroxyethyl methacrylate in the non-reactive liquid crystal (LC) 4-cyano-4′-pentylbiphenyl (5CB) using an open-cell setup. Colloids adsorbed to the nematic 5CB–air interface form non-close-packed hexagonal crystals that cover the entire interface area. We examine the mechanism of growth and assembly for the preparation of LC-templated interfacial colloidal superstructures. 

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5. Clickable decellularized extracellular matrix as a new tool for building hybrid-hydrogels to model chronic fibrotic diseases in vitro

   https://doi.org/10.1039/D0TB00613K  

   Petrou, Cassandra L.; D’Ovidio, Tyler J.; Bölükbas, Deniz A.; Tas, Sinem; Brown, R. Dale; Allawzi, Ayed; Lindstedt, Sandra; Nozik-Grayck, Eva; Stenmark, Kurt R.; Wagner, Darcy E.; et al (August 2020, Journal of Materials Chemistry B)

   null (Ed.)

   Fibrotic disorders account for over one third of mortalities worldwide. Despite great efforts to study the cellular and molecular processes underlying fibrosis, there are currently few effective therapies. Dual-stage polymerization reactions are an innovative tool for recreating heterogeneous increases in extracellular matrix (ECM) modulus, a hallmark of fibrotic diseases in vivo . Here, we present a clickable decellularized ECM (dECM) crosslinker incorporated into a dynamically responsive poly(ethylene glycol)-α-methacrylate (PEGαMA) hybrid-hydrogel to recreate ECM remodeling in vitro . An off-stoichiometry thiol–ene Michael addition between PEGαMA (8-arm, 10 kg mol −1 ) and the clickable dECM resulted in hydrogels with an elastic modulus of E = 3.6 ± 0.24 kPa, approximating healthy lung tissue (1–5 kPa). Next, residual αMA groups were reacted via a photo-initiated homopolymerization to increase modulus values to fibrotic levels ( E = 13.4 ± 0.82 kPa) in situ . Hydrogels with increased elastic moduli, mimicking fibrotic ECM, induced a significant increase in the expression of myofibroblast transgenes. The proportion of primary fibroblasts from dual-reporter mouse lungs expressing collagen 1a1 and alpha-smooth muscle actin increased by approximately 60% when cultured on stiff and dynamically stiffened hybrid-hydrogels compared to soft. Likewise, fibroblasts expressed significantly increased levels of the collagen 1a1 transgene on stiff regions of spatially patterned hybrid-hydrogels compared to the soft areas. Collectively, these results indicate that hybrid-hydrogels are a new tool that can be implemented to spatiotemporally induce a phenotypic transition in primary murine fibroblasts in vitro . 

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