Resorbable embolization microspheres: influence of the addition of ionic charges for drug loading on elasticity and viscoelasticity

Purpose We developed Resorbable Embolization Microspheres (REM) and modified its composition by adding ionic groups to enable loading of ionic drugs for chemoembolization. However, ionic groups, which are hydrophilic, will modify drastically their mechanical properties. Our objective was to check that after chemical modifications, elasticity (Young’s modulus) and viscoelasticity (Relaxation time), the two main mechanical properties of REM for targeting (Hidaka K, J Mech Behav Biomed Mater. 2012), were comparable to the ones of the gold standard Embosphere (ES). Materials and Methods Synthetic hydrogel REM were made of a hydrolytic resorbable crosslinker and an acrylic monomer by suspension polymerization. An ionically loadable group (methacrylic acid) was added at different concentrations: 0% (REM-0), 2.5% (REM-2.5), 5% (REM-5) and 10% (REM-10). Compression and relaxation tests were performed on single particle with REM and ES (sizes from 600 to 1200μm, 8 repetitions for each type), and their Young’s moduli and Relaxation half times (RHTs) were determined. The elasticity was evaluated by applying Hertz theory with the assumptions of incompressibility (Poisson’s ratio of 0.5). Results All REM supported a compression of 50% without breakage nor residual deformation. The Young’s moduli of REM inversely correlated with the amount of ionic group (p Conclusion The addition of ionic groups to REM gave them the same elasticity and viscoelasticity than ES. The transformation to make REM loadable is not detrimental to their mechanical properties. Table 1