Thermosensitive star polymer pompons with a core–arm structure as thermo-responsive controlled release drug carriers

In contrast with traditional chemotherapy, controlled drug delivery systems provide many advantages. Herein, a thermosensitive star polymer pompon with a core–arm structure was synthesized using a grafting-on method as a thermo-responsive controlled release drug carrier. Single-chain cyclized/knotted poly tetra(ethylene glycol) diacrylate (polyTEGDA) was used as the hydrophobic core, and thermosensitive linear poly(N-isopropylacrylamide-co-N-methylolacrylamide) (poly(NIPAM-co-NMA)) was selected as the hydrophilic arm. Below or above its lower critical solution temperature (LCST), the linear poly(NIPAM-co-NMA) grafted onto the polyTEGDA core adopted a stretched or curled status, respectively, then the drug could be loaded in or extruded out. The LCST of star polyTEGDA-b-poly(NIPAM-co-NMA) was adjusted to slightly above body temperature (37 °C). The antitumor drug doxorubicin (DOX) was successfully loaded into the pompons with a high loading capacity of 19.45%. The cumulative release of DOX from loaded pompons in vitro for 72 hours was 71% and 20.7% at 42 °C and 37 °C, respectively, indicating that the excellent temperature-controlled release characteristics result from the unique thermo-responsive extrusion effect. Moreover, DOX loaded polyTEGDA-b-poly(NIPAM-co-NMA) pompons achieved better antitumor ability against ovarian carcinoma SKOV3 cells at 42 °C compared with that at 37 °C. These results suggest that star polyTEGDA-b-poly(NIPAM-co-NMA) pompons have considerable promise as thermo-responsive controlled drug delivery carriers.