Fatty-acid-derived ester-urethane macromonomers synthesized using bismuth and zinc catalysts

Synthesis and Characterization of Photocurable Difunctional Monomers for Medical Applications

Photocurable materials offer a rapid transition from a liquid to a solid state, and have recently received great interest in the medical field. However, while dental resins are very popular, only a few materials have been developed for soft tissue repair. This study aims to synthesize a difunctional methacrylate monomer using a dibutyltin dilaurate which is suitable for the photocuring of soft materials. These soft materials were compared with PhotoBioCure® (Szczecin, Poland) material with a similar molecular weight, of Mn ~7000 g/mol on average. Infrared spectroscopy was used to monitor the two-step synthesis catalyzed with dibutyltin dilaurate, while spectroscopic and chromatographic methods were used to determine the chemical structure and molecular weight of the monomers. Photopolymerization kinetics under varying light intensities were explored in a nitrogen atmosphere for representative difunctional monomers. The mechanical testing of the resulting elastomeric films confirmed tensile strength and modulus values consistent with soft tissue parameters in the range of 3-4 MPa. The 3D printability of the macromonomers was also assessed. Additionally, cytotoxicity assessments using cultured cells showed a high cell viability (97%) for all new materials. Overall, we demonstrate that difunctional methacrylate monomers converted to flexible solids during photopolymerization show great potential for biomedical applications.

Eco-Friendly and Ready-To-Market Polyurethanes: A Design of Experiment-Guided Substitution of Toxic Catalyst and Fossil-Based Isocyanate

In this contribution, we tackle the replacement of the Hg-based catalyst and fossil-derived isocyanate precursors toward the formulation of a more sustainable polyurethane thermosetting resins (PUs), emulating the performance of a fully fossil-based one employed in industrial encapsulation of optoelectronics. A mixed Bi-Zn catalyst and a 71 % bio-based isocyanate are exploited at this aim through multivariate chemometric approaches, namely Design of Experiment (DoE). DoE allows us to investigate the effect of different formulation factors on selected parameters, such as the film flexibility and transparency or the gel time. More in detail, it is found that a low amount of Zn-rich catalytic mixture leads to a ready-to-market polyurethane only when a fossil-based isocyanate is used. Differently, PUs formulated with bio-based isocyanate, albeit showing a higher bio-based content, present an insufficient optical purity, jeopardizing their market acceptability. Nevertheless, adding a negligible amount of a specific long chain fatty acid as reactivity modulator in the formulation leads to a bubbles-free and ready-to-market resin showing an impressive 65 % w/w content of circular and bio-based components.

Enhanced Synthesis of Poly(1,4-butanediol itaconate) via Box-Behnken Design Optimization

At present, there are too few organ and tissue donors. Due to the needs of the medical market, scientists are seeking new solutions. Those can be found in tissue engineering by synthesizing synthetic cell scaffolds. We have decided to synthesize a potential UV-crosslinked bio-ink for 3D printing, poly(1,4-butanediol itaconate), in response to emerging needs. Diol polyesters are commonly investigated for their use in tissue engineering. However, itaconic acid makes it possible to post-modify the obtained polymer via UV-crosslinking. This work aims to optimize the synthesis of poly(1,4-butanediol itaconate) in the presence of a catalyst, zinc acetate, without using any toxic reactant. The experiments used itaconic acid and 1,4-butanediol using the Box-Behnken mathematical planning method. The input variables were the amount of the catalyst used, as well as the time and temperature of the synthesis. The optimized output variables were the percentage conversion of carboxyl groups, the percentage of unreacted C=C bonds, and the product's visual and viscosity analysis. The significance of the varying synthesis parameters was determined in each statistical model. The optimum conditions were as follows: amount of catalyst 0.3%nCOOH, reaction time 4 h, and temperature 150 °C. The temperature had the most significant impact on the product characteristics, mainly due to side reactions. Experimentally developed models of the polymerization process enable the effective synthesis of a polymer "tailor-made" for a specific application.

Injectable and photocurable macromonomers synthesized using a heterometallic magnesium-titanium metal-organic catalyst for elastomeric polymer networks

Injectable and in situ photocurable biomaterials are receiving a lot of attention due to their ease of application via syringe or dedicated applicator and ability to be used in laparoscopic and robotic minimally invasive procedures. The aim of this work was to synthesize photocurable ester-urethane macromonomers using a heterometallic magnesium-titanium catalyst, magnesium-titanium(iv) butoxide for elastomeric polymer networks. The progress of the two-step synthesis of macromonomers was monitored using infrared spectroscopy. The chemical structure and molecular weight of the obtained macromonomers were characterized using nuclear magnetic resonance spectroscopy and gel permeation chromatography. The dynamic viscosity of the obtained macromonomers was evaluated by a rheometer. Next, the photocuring process was studied under both air and argon atmospheres. Both the thermal and dynamic mechanical thermal properties of the photocured soft and elastomeric networks were investigated. Finally, in vitro cytotoxicity screening of polymer networks based on ISO10993-5 revealed high cell viability (over 77%) regardless of curing atmosphere. Overall, our results indicate that this heterometallic magnesium-titanium butoxide catalyst can be an attractive alternative to commonly used homometallic catalysts for the synthesis of injectable and photocurable materials for medical applications.

Bio-Based Photoreversible Networks Containing Coumarin Groups for Future Medical Applications

Photocurable biomaterials that can be delivered as liquids and rapidly (within seconds) cured in situ using UV light are gaining increased interest in advanced medical applications. Nowadays, fabrication of biomaterials that contain organic photosensitive compounds have become popular due to their self-crosslinking and versatile abilities of changing shape or dissolving upon external stimuli. Special attention is paid to coumarin due to its excellent photo- and thermoreactivity upon UV light irradiation. Thus, by modifying the structure of coumarin to make it reactive with a bio-based fatty acid dimer derivative, we specifically designed a dynamic network that is sensitive to UV light and able to both crosslink and re-crosslink upon variable wave lengths. A simple condensation reaction was applied to obtain future biomaterial suitable for injection and photocrosslinking in situ upon UV light exposure and decrosslinking at the same external stimuli but at different wave lengths. Thus, we performed the modification of 7-hydroxycoumarin and condensation with fatty acid dimer derivatives towards a photoreversible bio-based network for future medical applications.