Examining the transferrin-transferrin receptor system as a possible mechanism for cell specific targeting with liposomes

Citation

Totten, Nancy Susanne Demcak (1989) Examining the transferrin-transferrin receptor system as a possible mechanism for cell specific targeting with liposomes. Master's thesis, California Institute of Technology. doi:10.7907/2qfc-mj80. https://resolver.caltech.edu/CaltechTHESIS:03292010-094148072

Abstract

This research focuses on targeting capabilities which may be applied for delivery of liposomes to T cells. Two methods of targeting were investigated. The first involved IgG purified from goat antisera to aportion of the viral envelope of Human Immunodeficiency Virus (HIV). The IgG was derivatized with the N-hydroxysuccinimide ester of palmitic acid (NHSP) to increase its hydrophobicity so that it could be incorporated into the lipid bilayer of egg phosphatidylcholine liposomes. The second method used transferrin to coat liposomes made from egg phosphatidylcholine and egg phosphatidylethanolamine, 5:1 weight ratio, respectively. In this method the transferrin receptor (TfR) serves as a target for the delivery of transferrin (Tf) coated liposomes to cells. From previous observations made at the City of Hope as well as data from a resent paper, HIV infected cells appear to have an increased affinity for Tf. This increased affinity is most likely associated with an increase in cell surface TfRs. The H-9 cell line, which can be infected with HIV, has been characterized for the number of TfRs per cell and for the binding of Tf. Attaching IgG or Tf to a liposome will alter the protein structure. Thus, the receptor-ligand affinity characteristics of IgG as well as the affinity of iron for Tf and of Tf-Fe for TfR will change. As a result, the type of association which links IgG or Tf to the liposome will affect the targeting ability of the IgG or Tf coated liposomes. Many methods of associating IgG with liposomes have been studied. The method of choice is one of the most successful ways for the use of liposome delivery. It involves the attachment of palmitoyl chains to the IgG followed by insertion of the now hydrophobic IgG into the lipid membrane. Only a few procedures for attaching Tf and liposomes have previously been tried. I have examined a new method for attaching Tf to liposomes, involving the use of water soluble carbodiimide. The crosslinking of Tf and liposome has been observed with a maximum efficiency of 1 Tf molecule for 4 liposomes. For both IgG and Tf coated liposomes, an average diameter of 45-50nm was determined.

Thesis Files