Cancer antigen 125 (CA 125) is widely used as diagnostic biomarker for ovarian cancer. Change in the concentration level of CA 125 is associated with disease progression or regression. CA 125 posseses a phosphorylation site and protein backbone is phosphorylated on serine, before secretion. In this study, we have developed an imprinting method for CA 125 recognition and determination. In this method, methacryloyl antipyrine europium (III) [(MAAP)(2)-Eu(III)] and methacryloyl antipyrine terbium (III) [(MAAP)(2)-Tb(III)) have been used as new metal-chelating monomers via metal coordination chelation interactions. Phosphoserine (PS) has been used as a template for the detection of CA 125. PS imprinted carbon nanotube (CNT) and Fe2O3 nanoparticle (SPN) have cavities that are selective for CA 125. The binding affinity of the PS imprinted CNT and SPN nanosensor has been investigated using Langmuir adsorption isotherms and affinity constants (K-affinity) have found to be 1.85 10(5) M-1 for PS and 13.510(-3) mLU(-1) and 7.73 10(-3) mLU(-1) for CA 125 (for CNT and SPN, respectively). Detection limit of PS imprinted CNT nanosensor for PS and CA 125 have been found to be 1.77 10(-10) M and 0.49 UmL(-1), respectively. Human serum samples have been spiked with different concentrations of CA 125 (in pH 7.4 PBS) to investigate the feasibility of the nanosensors for clinical applications. Experimental results have been revealed that prepared nanosensors have been exhibited better sensivity, recovery and reproducibility.