Synthesis, rheological characterization, and proposed application of pre‐polyglycerol sebacate as ultrasound contrast agent based on theoretical estimation

Abstract

AbstractElastomers are employed in the field of acoustics as sound enhancers and making tissue‐mimicking phantoms for ultrasound imaging due to their good viscoelastic properties. Polyglycerol sebacate (PGS) is a relatively new biocompatible, biodegradable elastomer with low elastic modulus prepared via two‐step melt condensation reaction. The first step yields a soluble pre‐polymer while the second results in a cured insoluble tough elastomer. The elasticity of polymer is dependent upon curing time. Attractive aspects of pre‐PGS to be used as ultrasound contrast agent lie in its excellent viscoelastic properties, that is, low elastic modulus, near to lipids. This can give it acoustic properties of lipid microbubbles while keeping a stable response of polymeric microbubbles. In this study, pre‐PGS was synthesized via the melt‐condensation method and characterized by FTIR, NMR, TGA, melt flow index, contact angle, titration, and uniaxial compressive testing. Viscosity was measured by the Ostwald technique. These viscoelastic measurements were used to predict the acoustic response of pre‐PGS shell‐based microbubbles by running equations in MATLAB. Pre‐PGS showed an elastic modulus of 1.26 MPa and thermal stability up to 100°C. PGS showed much more elasticity than commercially available Sonovue ultrasound contrast agent, also it has low viscosity (0.016 Pa s) and density (1186 kg/m), due to which it has a low damping coefficient (4.32 × 106) compared to Sonovue (7.63 × 107), giving better oscillations in an acoustic field with higher scattering cross‐sectional area than standard Sonovue microbubbles. Based on these simulations pre‐PGS with 50%–60% degree of esterification showed excellent viscoelastic properties which make it an ideal material for microbubble ultrasound contrast agent.