Turn-on fluorescence sensor for the detection of heparin based on rhodamine B-modified polyethyleneimine-graphene oxide complex.

Rhodamine B modified Polyethyleneimine (PEI) (called RB-PEI) with strong fluorescence intensity was synthesized, which contained high positively charged amine groups. The fluorescence intensity of RB-PEI can be quenched by graphene oxide (GO). The high efficiency of the quenching was caused by the non-covalent binding of RB-PEI to the GO surface by electrostatic and π-π interactions, forming a RB-PEI/GO complex. However, adding heparin caused intense fluorescence to be recovered, and this was caused by the anionic heparin removing the RB-PEI from the GO surface, forming a fluorescent RB-PEI/heparin complex. Under optimal conditions, the change in the fluorescence intensity when heparin was added was proportional to the heparin concentration over the range 0.09-0.9 U mL(-1). The detection limit for heparin was 0.00132 U mL(-1), which was lower than that has been achieved using other methods. This approach offers a new quantitative method for determining heparin.