... although they raise less cytotoxicity issues due to the lack of solvents or initiators.1,2 ... 25 to 50 °C; (c) concentration of oligomer in PBS, from 2.5 to 7.5%;. (d) molar ratio of .... through filtration with a 22 μm sterile filter. The specimens ... Figure 1. MALDI-TOF/MS spectrum of oligomer mixture after 24 h of depolymerization.