Phage display is a well-established approach for the identification peptides that bind to a desired cell type. While chemical synthesis of selected peptides often results in ligands with low affinity, a multivalent tetrameric presentation of the peptides dramatically improves affinity. One of the primary uses of these peptides is conjugation to nanoparticle-based therapeutics for specific delivery to target cell type. One major advantage of phage display lies in its ability to rapidly identify target-specific reagents with pharmacological activity as agonists or antagonists. Cell surface proteins are especially important, because they have potential utility as diagnostic markers and therapeutic targets. Identification of ligands for these proteins will allow use of these ligands as diagnostic and therapeutic tools and permit the investigation of receptor function. The aim of this proposal is to identify peptide(s) specifically target targeting DU145 cell line. To this end, phage display library and biopanning procedures are used for screening and isolation of targeted phage. The present research focuses on evaluating the suitability of these small molecules as novel tumor markers for diagnosis and categorization of prostate tumors. Targeted phages as molecular imaging nanoparticles are a special class of pharmaceuticals that target specific biochemical signatures associated with disease and allow for noninvasive imaging on the molecular level. Because changes in biochemistry occur before diseases reach an advanced stage, molecular imaging probes make it possible to locate and stage disease, track the effectiveness of drugs, treat disease, monitor response, and select patients to allow for more personalized diagnosis and treatment of disease.