The Science and Technology of Cancer Theranostic Nanomedicines: A primer for Clinicians and Pharmacists

Abstract

The term " theranostics " refers to simultaneous diagnostic imaging and treatment and " nanotheranostics " refers to the simultaneous diagnostic imaging and treatment that makes use of nanomaterials for selective delivery of an imaging agent and a chemotherapeutic agent to a target organ. Nanocarriers have special properties that make them suitable for design of the theranostic platform. These include enhanced permeation and retention (the EPR effect), the provision for active targeting by attachment of suitable ligands to their surface, and unique optical and magnetic properties. Advanced theranostic systems are multifunctional in that the nanocarrier contains a homing device or targeting agent that directs the carrier to the cancer tissue, an agent for imaging the cancer tissue, and a chemotherapeutic agent to be delivered selectively to the tumor. The core nanomaterial is often surface-modified to facilitate incorporation of the various functionalities. Several types of nanoparticles (NPs) have been employed as imaging and drug delivery agents, including both solid inorganic materials (Fe3O4 NPs, Gadolinium NPs, Gold NPs, carbon nanotubes, semiconductor quantum dots) and organic-based NPs, including liposomes, micelles, dendrimers and polymers. The nanotheranostic platform is capable of simultaneous imaging and therapy, as seen in the case of gold nanoparticles. Gold NPs can generate heat when irradiated with light of a specific wavelength, which can kill tumor cells due to hyperthermia. The high atomic number of gold and its X-ray absorption allows simultaneous tumor imaging via the fluorescence quenching effect or by computed tomography. Other methods of imaging such as Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), fluorescence and ultrasound may also be employed depending on the properties of the nanomaterial, while the tumor killing agent (drug, genes or hyperthermia) is being delivered selectively to the tumor. Molecular imaging can identify the location of the tumor cell within the body as well as provide information about the expression profile and stage of the disease. It can also reveal early tumor response to therapy that will facilitate determination of treatment regimens. Therefore, the incorporation of both diagnostic and therapeutic modalities onto the same nanomaterial is a promising strategy to improving the efficiency and safety of drug delivery systems. This review will focus on the basic science and technology involved in the design and development of Nano platforms capable of simultaneous delivery of diagnostic imaging agents and cancer therapeutic agents.