Tough photopolymers based on vinyl esters for biomedical applications

Additive and Lithographic Manufacturing of Biomedical Scaffold Structures Using a Versatile Thiol-Ene Photocurable Resin

Additive and lithographic manufacturing technologies using photopolymerisation provide a powerful tool for fabricating multiscale structures, which is especially interesting for biomimetic scaffolds and biointerfaces. However, most resins are tailored to one particular fabrication technology, showing drawbacks for versatile use. Hence, we used a resin based on thiol-ene chemistry, leveraging its numerous advantages such as low oxygen inhibition, minimal shrinkage and high monomer conversion. The resin is tailored to applications in additive and lithographic technologies for future biofabrication where fast curing kinetics in the presence of oxygen are required, namely 3D inkjet printing, digital light processing and nanoimprint lithography. These technologies enable us to fabricate scaffolds over a span of six orders of magnitude with a maximum of 10 mm and a minimum of 150 nm in height, including bioinspired porous structures with controlled architecture, hole-patterned plates and micro/submicro patterned surfaces. Such versatile properties, combined with noncytotoxicity, degradability and the commercial availability of all the components render the resin as a prototyping material for tissue engineers.

Mono-substitution of symmetric diesters: selectivity of Mycobacterium smegmatis acyltransferase variants

Selective mono-substitution of symmetric diesters was demonstrated using an immobilized Mycobacterium smegmatis esterase/acyltransferase (MsAcT) variant.

Silane-Acrylate Chemistry for Regulating Network Formation in Radical Photopolymerization

Photoinitiated silane-ene chemistry has the potential to pave the way toward spatially resolved organosilicon compounds, which might find application in biomedicine, microelectronics, and other advanced fields. Moreover, this approach could serve as a viable alternative to the popular photoinitiated thiol-ene chemistry, which gives access to defined and functional photopolymer networks. A difunctional bis(trimethylsilyl)silane with abstractable hydrogens (DSiH) was successfully synthesized in a simple one-pot procedure. The radical reactivity of DSiH with various homopolymerizable monomers (i.e., (meth)acrylate, vinyl ester, acrylamide) was assessed via 1H NMR spectroscopic studies. DSiH shows good reactivity with acrylates and vinyl esters. The most promising silane-acrylate system was further investigated in cross-linking formulations toward its reactivity (e.g., heat of polymerization, curing time, occurrence of gelation, double-bond conversion) and compared to state-of-the-art thiol-acrylate resins. The storage stability of prepared resin formulations is greatly improved for silane-acrylate systems vs thiol-ene resins. Double-bond conversion at the gel point (DBCgel) and overall DBC were increased, and polymerization-induced shrinkage stress has been significantly reduced with the introduction of silane-acrylate chemistry. Resulting photopolymer networks exhibit a homogeneous network architecture (indicated by a narrow glass transition) that can be tuned by varying silane concentration, and this confirms the postulated regulation of radical network formation. Similar to thiol-acrylate networks, this leads to more flexible photopolymer networks with increased elongation at break and improved impact resistance. Additionally, swelling tests indicate a high gel fraction for silane-acrylate photopolymers.

Photochemically Driven Polymeric Network Formation: Synthesis and Applications

Polymeric networks have been intensely investigated and a large number of applications have been found in areas ranging from biomedicine to materials science. Network fabrication via light-induced reactions is a particularly powerful tool, since light provides ready access to temporal and spatial control, opening an array of synthetic access routes for structuring the network geometry as well as functionality. Herein, the most recent light-induced modular reactions and their use in the formation of precision polymeric networks are collated. The synthetic strategies including photoinduced thiol-based reactions, Diels-Alder systems, and photogenerated reactive dipoles, as well as photodimerizations, are discussed in detail. Importantly, applications of the fabricated networks via the aforementioned reactions are highlighted with selected examples. Concomitantly, we provide future directions for the field, emphasizing the most critically required advances.

Exploring Network Formation of Tough and Biocompatible Thiol-yne Based Photopolymers

This work deals with the in-depth investigation of thiol-yne based network formation and its effect on thermomechanical properties and impact strength. The results show that the bifunctional alkyne monomer di(but-1-yne-4-yl)carbonate (DBC) provides significantly lower cytotoxicity than the comparable acrylate, 1,4-butanediol diacrylate (BDA). Real-time near infrared photorheology measurements reveal that gel formation is shifted to higher conversions for DBC/thiol resins leading to lower shrinkage stress and higher overall monomer conversion than BDA. Glass transition temperature (T_g ), shrinkage stress, as well as network density determined by double quantum solid state NMR, increase proportionally with the thiol functionality. Most importantly, highly cross-linked DBC/dipentaerythritol hexa(3-mercaptopropionate) networks (T_g ≈ 61 °C) provide a 5.3 times higher impact strength than BDA, which is explained by the unique network homogeneity of thiol-yne photopolymers.

Tough and degradable photopolymers derived from alkyne monomers for 3D printing of biomedical materials

Photo curing of low-cytotoxic alkyne carbonate/thiol formulations leads to tough polymers with adjustable degradation behavior for 3D printing of biomedical devices.