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

Abstract

Photocurable materials that can be delivered as liquids and rapidly (within seconds) cured in situ using UV light are gaining increased interest in advanced minimally invasive procedures. The aim of this work was to synthesize and characterize fatty-acid-derived ester-urethane telechelic (methacrylate) macromonomers, suitable for photopolymerization. The commonly used dibutyltin dilaurate catalyst was replaced with bismuth neodecanoate, bismuth tris(2-ethylhexanoate), and zinc (II) acetyloacetonate as less-toxic alternative catalysts. Additionally, ethyl acetate was used as a “green” solvent. The progress of the two-step synthesis was monitored with infrared spectroscopy. The chemical structure and molecular weight of the obtained viscous materials was characterized with nuclear magnetic resonance spectroscopy and gel permeation chromatography. Photocrosslinking of the macromonomers into elastomeric films was achieved using 150 s per spot of UV light (20 mW/cm2) exposure. Mechanical tensile testing of the films indicated their elasticity up to 120% and low modulus typical for soft and elastomeric materials. Finally, in vitro cytotoxicity tests showed high cell viability for the case of materials synthesized using bismuth and zinc catalysts. Overall, our results indicate that bismuth and zinc catalysts are excellent alternatives to organotin compounds in the synthesis of photocurable methacrylate ester-urethanes for potential biomedical applications.

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

“…Synthesis of telechelic macromonomers was performed in two steps based on our previous work 17 and the reaction scheme is presented in Fig. 2.…”

“…Photopolymerization of the obtained macromonomers was performed according to the procedure thoroughly described in our previous work. 17 Briefly, the obtained telechelic macromonomers were mixed with a 2% w/w solution of Omnirad 819 photoinitiator in EtOAc. Then, the solvent was evaporated under reduced pressure and the obtained highly viscous liquid was poured onto a glass plate and was spread into a film with a steel applicator.…”

“…35) using murine fibroblast cell line L929, as described previously. 17 Extracts were prepared in duplicate, by incubating samples of each photocured material (3 cm 2 area, thickness 0.5 mm, cut into small pieces) in 1 mL of complete growth medium (Dulbecco's Modified Eagle Medium (DMEM), containing 10% Fetal Bovine Serum (FBS), 2 mM l -glutamine, 100 U mL −1 penicillin, and 100 μg mL −1 streptomycin) for 24 hours at 37 °C, in a 24-well plate. At the same time, 10 × 103 L929 cells (passages 10–25) were plated per well in a 96-well plate in complete growth medium and incubated for 24 hours in a cell culture incubator.…”

“…In our previous work, we demonstrated that bismuth and zinc-based homometallic catalysts can be attractive, less toxic alternatives to DBTDL for the synthesis of photocurable ester-urethane macromonomers for elastomeric networks preparation . In that work, we discussed there two possible catalysis mechanisms: insertion and Lewis acid. 17 Importantly, because isophorone diisocyanate (IPDI) is an asymmetric cycloaliphatic diisocyanate with primary and secondary isocyanate groups, the choice of catalyst plays an important role. Typically, the secondary cycloaliphatic group is more reactive than the primary aliphatic group.…”

“…Building upon our previous work, here we investigated synthesis of the telechelic macromonomers based on polyester diol using magnesium-titanium( iv ) butoxide as catalyst. We hypothesized that this heterometallic catalytic system would enhance selectivity toward the secondary isocyanate function of IPDI and would result in shorter reaction times than our previous work with bismuth and zinc-based homometallic catalysts, 17 while at the same time obtaining one dominant macromonomer that would remain non-toxic. Towards this aim, we examined chemical structure and physio-chemical properties of the obtained macromonomers and we performed the cytotoxicity screening of fabricated elastomeric networks to assess their suitability for medical applications, especially for delivery of a precursor in minimally invasive medical procedures.…”