Advisor(s)

V. P. Torchilin

Contributor(s)

Samuel J. Gatley, Roger W. Giese, Rebecca Carrier, Akio Ohta

Date of Award

4-2012

Date Accepted

4-2012

Degree Grantor

Northeastern University

Degree Level

Pharm.D.

Degree Name

Doctor of Pharmacy

Department or Academic Unit

Bouvé College of Health Sciences. School of Pharmacy.

Keywords

cell-penetrating peptide, liposomes and micelles, monoclonal antibody, multifunctional nanocarriers, pH-sensitive polymer, tumor drug delivery

Disciplines

Medicinal and Pharmaceutical Chemistry | Pharmaceutics and Drug Design | Pharmacy and Pharmaceutical Sciences

Abstract

A tumor is an abnormally growing mass of cells. Ordinary chemotherapeutic agents used to prevent tumor growth produce more side effects and less than desired therapeutic effect. Targeted drug-delivery systems are necessary to provide and maintain an optimum drug concentration in target tissues and cells. Long-circulating nanoparticles have the ability to passively and actively target tumors and deliver the anticancer drugs. Passive targeting can be achieved by prolonged circulation and retention of the drug-loaded nanoparticles in the tumor, via enhanced permeability and retention (EPR) effect. Active targeting is possible by attaching various ligands to the nanoparticles to specifically target the tumors. These multifunctional particles help in improving the pharmacokinetic profile of the drug, improve the drug bioavailability and reduce undesired side-effects in the non-target organs. The main long-term goal of this project is the development of multifunctional micelles and liposomes that increase the delivery of anticancer drugs to the tumor.

Passive targeting of nanoparticles can be achieved by using polyethylene glycol-phosphatidylethanolamine (PEG-PE) coating to prevent uptake of the nanoparticles by macrophages and make the particle long-circulating. For active targeting, several moieties can be attached to the particle surface. Anti-nucleosome monoclonal antibody 2C5 recognizes a broad variety of tumor cells via the tumor cell surface-bound nucleosomes. It can recognize murine and human tumor cells, but not normal cells. Cell-penetrating peptides (CPPs) have shown enhanced transport of cargoes through the plasma membrane into the cells. Stimuli-sensitive PEG-hydrazone (Hz)-PE conjugate (with a low pH-sensitive hydrazone bond between PEG and PE) which is stable at normal pH and can shield the CPP function.

In this study, micelles and liposomes were modified with a CPP-PEG-PE conjugate to improve the transport of these nanocarriers into the cells. Since CPPs are susceptible to enzymatic degradation and non-specific cellular interactions, they were shielded by the PEG-Hz-PE conjugate. At normal pH (as found in circulation), the PEG-Hz-PE shielded the CPP and at low pH (as found in tumors), when this polymer underwent hydrolysis, PEG detached to expose the CPP and increased the internalization of the micelles and liposomes. CPP modified pH-sensitive micelles loaded with anticancer drug paclitaxel, improved tumor cell association and cytotoxicity in vitro. Intratumor injections of these micelles demonstrated apoptosis in tumors developed subcutaneously in mice and established this proof of concept.

Liposomes were further modified with mAb 2C5-PEG-PE. Recognition of the tumor cells during the first phase of delivery was imparted by the attached mAb 2C5. During the second phase of delivery, the exposure of the shielded TATp upon hydrolysis of pH-sensitive polymer at the slightly acidic pH of the tumor cell environment, improved the uptake of drug-loaded liposomes by tumor cells. Thus, tumor cell recognition and uptake of the liposomes was obtained in a controlled fashion. Moreover, the growth of subcutaneously developed drug-resistant and drug-sensitive tumors in nude mice was inhibited and substantial decrease in the mean tumor weights was obtained by intravenous injection of these drug-loaded multifunctional liposomes. In this way, nanoparticles can be modified with multiple functionalities to improve tumor targeting and enhance the effect of an anticancer agent.

Document Type

Dissertation

Rights Holder

Anjali Vasant Apte


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