Introduction: Poly(ethylene glycol) polyurethane hydrogels (PEG-PUs) represent a versatile class of biomaterials with significant potential in tissue engineering and are steadily gaining traction in clinical applications (2). Traditionally, polyurethanes are synthesized through various methods, many of which involve the reaction of isocyanates with diols. However, this study presents a non-isocyanate synthetic route which offers enhanced control over the gel's physical and mechanical properties, facilitating precise engineering of the pancreatic ductal adenocarcinoma (PDAC) microenvironment.
Materials and
Methods: The synthesis of the reaction intermediate 1,4-butyl(biscarbonylimidazolide) (BBCI) was completed through the reaction of chain extender 1,4-butanediol (BD) and 1,1’-carbonyldiimidazole (CDI). This reaction took place overnight in a three necked round-bottom flask under a blanket of argon. 80 mmol of BD was first dissolved in ethyl acetate then 200 mmol of CDI was added in small amounts to ensure complete dissolution. The product, BBCI, was purified using a fritted funnel to separate the solid product from liquid. Then the product was washed thoroughly with ethyl acetate to remove by-products. The BBCI was characterized using H NMR and observed to have imidazole peaks (1). In a subsequent reaction, using DMF as a solvent, 500 mg of the diamine amine-PEG-amine was added to 55.7 mg of BBCI to react with available imidazolide groups, forming a PEG-urethane with BD as a chain extender. After 24 h, 600 mg of amine-PEG-acrylate was added to further extend the PEG urethane polymer chain and cap either end of the resulting polymer with photoactive acrylate end groups. The polymer product was precipitated in cold diethyl ether and filtered to collect the solid PEG-PU product. This product was vacuum dried overnight and characterized by H NMR using a Bruker Advance 400 Spectrometer. To observe how HUVECs interact with the PEG-PU gels, a 24-well plate was filled with PEG-PU and PEG-RGDS solution and exposed to UV light to form hydrogels. The HUVECs were then seeded onto the surface of the hydrogels and incubated at 37 Celsius for two days.
Results, Conclusions, and Discussions: Swelling studies were conducted to determine the differences in swelling ratios between PEGDA hydrogels and the PEG-PU hydrogels. Both sets of gels were weighed and photographed before incubation in PBS at 37°C. The PEGDA gels had an initial average mass of 62g while the PEG-PU hydrogels had an initial mass average of 70.9g (Figure B). After 45 minutes, the PEG-PU gels had an average mass of 150.1 g, almost twice their original mass (Figure B). The PEGDA gels swelled to an average mass of 70.9g after 45 minutes, indicating that PEG-PU gels swell to a greater extent than PEGDA gels, suggesting increased porosity in the PEG-PU crosslinked polymer network. After 4 hours, the PEGDA gels swelled to an average mass of 81g while the PEG-PU gels swelled to an average mass of 159g, almost three times the original mass (Figure A). These studies show that the use of polyurethane gels is a promising application in engineering the PDAC microenvironment. While further studies must be conducted to determine whether cells can proliferate on these materials, non-isocyanate PEG-PU hydrogels will continue to show promise in clinical application.
