Multifunctional Nanomaterials and Their Applications in Drug Delivery and Cancer Therapy

Abstract

The field of nanotechnology has led to the development of many innovative strategies for effective detection and treatment of cancer, overcoming limitations associated with conventional cancer diagnosis and therapy. Multifunctional nanoparticle systems can integrate imaging, targeting and treatment moieties on the surface and in the core, resulting in targeted delivery of the imaging or treatment modalities, specifically to the tumor. Multifunctional nanoparticles also enable simultaneous delivery of multiple treatment agents, resulting in effective combinatorial therapeutic regimens against cancer. In this review, various multifunctional nanoparticle systems that feature a variety of targeting moieties for in vitro and/or in vivo cancer imaging and therapy are discussed.

Keywords: cancer therapy; drug delivery; imaging; multifunctional nanoparticles; nanotechnology; tumor targeting.

Figure 1

The three main classes of functionalities that comprise a multifunctional nanoparticle for cancer diagnostics and therapy. A tumor-specific targeting moiety, such as the folate molecule, recognizes the folate receptor on the tumor cell surface to provide directed delivery of an imaging probe, for example the Cy5 fluorescent molecule, and/or the treatment agent, for example the chemotherapy drug paclitaxel.

Figure 2

Inorganic and organic nanoparticle (NP) materials. Multifunctional NPs can be synthesized using two basic types of NPs; organic (micelles, liposomes, nanogels and dendrimers) and inorganic (superparamagnetic iron oxide (SPIO), gold, quantum dots (QD) and lanthanide ions.

Figure 3

Organic nanoparticles (NPs): nanomicelles, liposomes, nanogels and dendrimers. (a) Nanomicelles are constructed by the assembly of amphiphilic blocks with a hydrophobic head and a hydrophilic outer tail. Imaging and treatment agents are encapsulated inside the hydrophobic core; (b) Liposome NPs are made up of lipid bilayers that carry drug inside the hydrophobic core or inside the lipid bilayer; (c) Polymeric nanogels are synthesized by crosslinking activated polymer chains, creating an inner porous space that can accommodate multiple payloads and imaging moieties; (d) Dendrimers are highly branched polymers that are synthesized by repeated branching cycles. The inner core and the outer branches provide multiple points of conjugation of imaging, targeting and treatment modalities.

Figure 4

Inorganic NPs. Four important inorganic nanomaterials used in the construction of multifunctional NPs are SPIO, gold, QD and lanthanide ions.

Figure 5

Schematic diagram representing the mode of action of targeted multifunctional nanoparticle (NP). The NP encapsulating a chemotherapy drug is targeted to the cancer cell surface by the cancer cell-specific ligand. The NP then binds to the cancer cell surface by recognizing the receptor, resulting in internalization of the NP by endocytosis. Inside the cancer cell, the NP undergoes endosomal escape, leading to the release of the treatment cytotoxic drug, which then activates consecutive steps, resulting in cell death.