Water‐Soluble Poly(N‐isopropylacrylamide)–Graphene Sheets Synthesized via Click Chemistry for Drug Delivery

Covalently functionalized graphene sheets are prepared by grafting a well‐defined thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM‐grafted graphene sheets (PNIPAM‐GS) consist of about 50% polymer, which endows the sheets with a good solubility and stability in physiological solutions. The PNIPAM‐GS exhibits a hydrophilic to hydrophobic phase transition at 33 °C, which is relatively lower than that of a PNIPAM homopolymer because of the interaction between graphene sheets and grafted PNIPAM. Moreover, through π–π stacking and hydrophobic interaction between PNIPAM‐GS and an aromatic drug, the PNIPAM‐GS is able to load a water‐insoluble anticancer drug, camptothecin (CPT), with a superior loading capacity of 15.6 wt‐% (0.185 g CPT per g PNIPAM‐GS). The in vitro drug release behavior of the PNIPAM‐GS‐CPT complex is examined both in water and PBS at 37 °C. More importantly, the PNIPAM‐GS does not exhibit a practical toxicity and the PNIPAM‐GS‐CPT complex shows a high potency of killing cancer cells in vitro. The PNIPAM‐GS is demonstrated to be an effective vehicle for anticancer drug delivery.