Poly(ethylene glycol) methacrylate hydrolyzable microspheres for transient vascular embolization

Poly(ethylene glycol) methacrylate (PEGMA) hydrolyzable microspheres intended for biomedical applications were readily prepared from poly(lactide-co-glycolide) (PLGA)-poly(ethylene glycol) (PEG)-PLGA crosslinker and PEGMA as a monomer using a suspension polymerization process. Additional co-monomers, methacrylic acid and 2-methylene-1,3-dioxepane (MDO), were incorporated into the initial formulation to improve the properties of the microspheres. All synthesized microspheres were spherical in shape, calibrated in the 300-500 μm range, swelled in phosphate-buffered saline (PBS) and easily injectable through a microcatheter. Hydrolytic degradation experiments performed in PBS at 37 °C showed that all of the formulations tested were totally degraded in less than 2 days. The resulting degradation products were a mixture of low-molecular-weight compounds (PEG, lactic and glycolic acids) and water-soluble polymethacrylate chains having molecular weights below the threshold for renal filtration of 50 kg mol−1 for the microspheres containing MDO. Both the microspheres and the degradation products were determined to exhibit minimal cytotoxicity against L929 fibroblasts. Additionally, in vivo implantation in a subcutaneous rabbit model supported the in vitro results of a rapid degradation rate of microspheres and provided only a mild and transient inflammatory reaction comparable to that of the control group.