Carboxylic acid terminated, solution exfoliated graphite by organic acylation and its application in drug delivery

Abstract

Graphite nanosheets are considered as a promising material for a range of applications from flexible electronics to functional nanodevices such as biosensors, intelligent coatings and drug delivery. Chemical functionalization of graphite nanosheets with organic/inorganic materials offers an alternative approach to control the electronic properties of graphene, which is a zero band gap semiconductor in pristine form. In this paper, we report the aromatic electrophilic substitution of solution exfoliated graphite nanosheets (SEGn). The highly conjugated π-electronic system of graphite nanosheets enable it to have an amphiphilic characteristic in aromatic substitution reactions. The substitution was achieved through Friedel–Crafts (FC) acylation reaction under mild conditions using succinic anhydride as acylating agent and anhydrous aluminum chloride as Lewis acid. Such reaction renders towards the carboxylic acid terminated graphite nanosheets (SEGn–FC) that usually requires harsh reaction conditions. The product thus obtained was characterized using various spectroscopic and microscopic techniques. Highly stable water-dispersed sodium salt of carboxylic acid terminated graphite nanosheets (SEGn–FC-Na) was also prepared. A comparative sheet-resistance measurements of SEGn, SEGn–FC and SEGn–FC-Na were also done. Finally, the anticancer drug doxorubicin (DOX) was loaded on water dispersible SEGn–FC-Na with a loading capacity of 0.266 mg mg−1 of SEGn–FC-Na and the release of DOX from this water-soluble DOX-loaded SEGn–FC-Na at two different temperatures was found to be strongly pH dependent. Selective carboxylic acid terminated solution exfoliated graphite nanosheets were achieved through Friedel–Crafts acylation reaction and dispersed in water by making Na-salt of the same. Anticancer drug doxorubicin was successfully loaded onto this highly water dispersible Na-salt and the drug release was found to be pH dependant. The low cost and efficient drug release make it a potential carrier for targeted drug delivery.