Functionalization of polyethylene (PE) beads was accomplished via radiation induced graft copolymerization of acrylic acid/acrylamide (AAc/AAm) binary comonomer of different compositions onto such beads. Factors affecting the grafting yield were optimized and the occurrence of the grafted chains was confirmed by following the FTIR spectra of the grafted beads. SEM analyses were used to follow the variation of the morphology of the grafting and immobilization onto PE beads. Some bio-active molecules such as Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Thyroid-stimulating hormone (TSH), and Prolactin were immobilized to the radiation functionalized PE beads. The parameters may affect the immobilization process such as degree of grafting, temperature, and pH of the coupling buffer and the coupling period were investigated. The obtained results show that the grafting of AAc offers a better immobilization environment than those of AAm and their copolymer. It is found that the highest immobilization degree would be achieved at pH 7 and 37 degrees C for 24 h. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3725-3733, 2012