Iron ions selective biosensor (Fe3+) based on zinc oxide nano-rods thin film symbolic as ZnO-(NRs)TF will be developed and prepared. The potentiometric response for ZnO-(NRs)TF deposited on conducting plastic and silicon substrates as working electrode versus reference electrode (Ag/AgCl) was found to be linear against logarithmic FeCl3 with concentration range between 10-6 M and 10-2 M. The ZnO-(NRs)TF will be grown on conducting plastic and silicon substrates using two methods (Sol - Gel and aqueous chemical growth (ACG)) by seed layers and nano-rod growth will be investigated. For fabricate an advanced extracellular iron biosensor, the ZnO-(NRs) on plastic and silicon substrates were coated with a thin layer of specific ionophore membrane to be used for iron concentration measurements in extracellular solution. The prepared sample crystallinity and microstructure will be characterized by x-ray diffraction (XRD) which, imply that ZnO-(NRs)TF sample crystallite sizes are in the nano-scale. The prepared samples morphology was characterized by Field emission scanning electron microscope (FESEM).