Abstract
Graphitic-phase carbon nitride (g-C&sub3;N&sub4;) is a graphene analogue, which has attracted much attention for its unique physicochemical properties. The bulk g-C&sub3;N&sub4; is often fragmented and ionized to nanosheets, obtaining improved performance or confer novel properties. It is reported that g-C&sub3;N&sub4; nanosheets using different processing methods can be modified with different functional groups, resulting in different electrical characteristics. However, the surface charge of g-C&sub3;N&sub4; nanosheets is seldom mentioned as a factor influencing their biological applications. In our present study, we prepared two kinds of uniformly dispersed g-C&sub3;N&sub4; nanosheets of high quality, the carboxyl- and amino-rich g-C&sub3;N&sub4; nanosheets. Although both the carboxyl- and amino-rich g-C&sub3;N&sub4; nanosheets displayed good biocompatibility in vitro and in vivo, however, they are at very different levels of surface charge, which are relative to different cellular uptake, penetration mechanism and lysosome escape ability of the nanosheets.