Immunologically cloaked and target-specific peptide ligands

Abstract

It is a prerequisite for effective systemic delivery of target to identify and recognize specific molecules that can target cells with a high affinity and specificity. Moerover, avoiding phagocytosis mechanism by macrophage is also important for delivery. In order to delivery systems to be effective for treatment, it is necessary to satisfy the following two conditions: passive and active targeting. It should be possible to reach target tumor tissues through various anatomical or immunological barriers without loss of drug in the blood stream after administration. Moreover, after reaching the target, only target cells should be selectively killed. These two basic strategies also play a role in improving patient survival and quality of life by reducing the toxicity that increases the intracellular concentration of the drug and at the same time limits the therapeutic concentration of the drug. Here, I demonstrate the interaction between biomolecules and ligands. First, I introduce a self-peptide on capsid of T7 bacteriophage for effective phage therapy with their prolonged blood circulation by escaping from the phagocytosis of macrophages based on CD47 and SIRP alpha interaction. Second, molecular dynamic simulation is used to identify the target peptide ligand due to the structural change of the P2 beta-sheet that occurs when the fibrinogen is changed to fibrin. The novel heptameric peptide has a linear structure with proline residue fixation. To confirm this experimentally, recombinant protein of fibrinogen gamma module and truncated fibrinogen gamma module without P2 beta-sheet are produced. FPLC is used to confirm that the peptides excavated in vacancy caused by removal of P2 beta-sheet are specifically bound. Third, I evaluate and utilize the fibrin-binding peptide that can specifically and strongly target fibrin deposited around A549 human lung carcinoma because of high expression level of fibrinogen mRNA of A549. It shows high affinity of the targeting peptide specifically to A549 in vitro and in vivo. This will be promising properties for a targeted delivery of small molecular drugs, peptides, proteins, and nanocarriers to lung cancer cells. I expect that the targeting peptide can be utilized as a lung cancer targeting moiety having significant implications for the lung cancer targeted treatments. Moreover, I identify a novel peptide targeting islet cells of pancreas using biopanning with M13 phage display. This thesis focuses on the structural and functional changes of target proteins from a microscopic point of view, rather than macroscopic targeted ligand studies. It is expected that this mechanism-based ligand discovery research will become a basis for application to various fields. The identification and application of novel functional peptides are promising approach to improve in vivo targeting efficiency of various nanocarriers to specific affected area and the efficacy of therapeutic agents incorporated within the nanocarriers.