Cyclin A(2) IS a prognostic indicator in early-stage cancer. However, since most of peptide-protein bindings do not produce an easily measurable output signal, this severely hinders homogeneous detection of protein using peptide as detection probe: Cyclin A(2) can be detected as low as 0.6 mu m using a well-known p21 ((WAF-1)) consensus senquence for a specific cyclin A(2) binding motif, which is incorporated into a Tb3+ chelating macrocycle by chemical modification at the N-terminus of CM B. Herein, a simple, ultra-sensitive, and selective signal-on fluorescence assay is developed for detection of a prognostic indicator in early-stage cancer, cylin A(2.) Graphene oxide (GO) is even superior to SWNTs for cyclin A(2) detection. The direct detection limit using graphene oxide is 0.5 nm, 10-fold better than using SWNTs, and 1200-fold better than the latest reported value of 0.6 mu m using the Tb3+ chelating macrocyle modified p21((WAF-1)) peptide.