Bioderived 4D Printable Terpene Photopolymers from Limonene and β-Myrcene

Synthesis of Bio-Based Polyester Resins for Vat Photopolymerization 3D Printing

Driven by environmental considerations, the scientific community has directed great effort towards the synthesis of new materials derived from renewable resources. However, for photocurable resins, most commercially available building blocks still rely on petroleum-based precursors. Herein, we present a simple synthesis route for bio-based acrylate-modified polyester resins, whose viscosity is sufficiently low for processing them with vat photopolymerization 3D printing. The established synthesis route enables the gradual substitution of fossil-based raw materials with bio-based alternatives. The acid number, color and viscosity of the bio-based acrylic resins are characterized and photocurable formulations are prepared by adding a radical photoinitiator. The photopolymerization kinetics, and thermomechanical and mechanical properties of the photopolymers are investigated as a function of the resin structure and benchmarked against a commercially available petroleum-based counterpart. Finally, the processability of the new bio-based resins via digital light processing 3D printing is demonstrated and test specimens are successfully 3D printed with a resolution in the millimeter range.

4D Printable Salicylic Acid Photopolymers for Sustained Drug Releasing, Shape Memory, Soft Tissue Scaffolds

3D printing of pharmaceuticals offers a unique opportunity for long-term, sustained drug release profiles for an array of treatment options. Unfortunately, this approach is often limited by physical compounding or processing limitations. Modification of the active drug into a prodrug compound allows for seamless incorporation with advanced manufacturing methods that open the door to production of complex tissue scaffold drug depots. Here we demonstrate this concept using salicylic acids with varied prodrug structures for control of physical and chemical properties. The role of different salicylic acid derivatives (salicylic acid, bromosalicylic allyl ester, iodosalicylic allyl ester) and linker species (allyl salicylate, allyl 2-(allyloxy)benzoate, allyl 2-(((allyloxy)carbonyl)oxy)benzoate) were investigated using thiol-ene cross-linking in digital light processing (DLP) 3D printing to produce porous prodrug tissue scaffolds containing more than 50% salicylic acid by mass. Salicylic acid photopolymer resins were all found to be highly reactive (solidification within 5 s of irradiation at λ = 405 nm), while the cross-linked solids display tunable thermomechanical behaviors with low glass transition temperatures (Tgs) and elastomeric behaviors, with the carbonate species displaying an elastic modulus matching that of adipose tissue (approximately 65 kPa). Drug release profiles were found to be zero order, sustained release based upon hydrolytic degradation of multilayered scaffolds incorporating fluorescent modeling compounds, with release rates tuned through selection of the linker species. Cytocompatibility in 2D and 3D was further demonstrated for all species compared to polycarbonate controls, as well as salicylic acid-containing composites (physical incorporation), over a 2-week period using murine fibroblasts. The use of drugs as the matrix material for solid prodrug tissue scaffolds opens the door to novel therapeutic strategies, longer sustained release profiles, and even reduced complications for advanced medicine.