Nanomaterials Used in Vivo Applications

A handful of nanomaterials are being studied in clinical trials or have already been approved by the FDA for use in humans and many proof-of-concept studies of nanomaterials in cell-culture and small-animal models for medical applications are under way.

Many of these nanomaterials are designed to target tumors in vivo and are intended for use either as drug carriers for therapeutic applications or as contrast agents for diagnostic imaging.

Nanomaterials Used as Drug Carriers or Contrast Agents for In Vivo Cancer Applications.Tumors have poor lymphatic drainage, and their vessels are highly porous. This enables nanomaterials to diffuse and accumulate in the tumor matrix. Nanomaterials that carry chemotherapeutic agents can target and kill tumor cells, whereas nanomaterials that are magnetic or fluorescent are used as imaging agents for detecting tumors.

Nanomaterials infused into the bloodstream can accumulate in tumors owing to the enhanced permeability and retention effect when the vasculature of immature tumors has pores smaller than 200 nm, permitting extravasation of nanoparticles from blood into tumor tissue. The infusion of antineoplastic drugs with nanomaterials as carriers results in an increased payload of drugs to the tumor, as compared with conventional infusion. With nanomaterials, the high ratio of surface area to volume permits high surface loading of therapeutic agents; in the case of organic nanomaterials, their hollow or porous core allows encapsulation of hundreds of drug molecules within a single carrier particle.
When the carrier particle degrades, the drug molecules are released, and the rate of degradation can even be controlled and fine-tuned according to the polymer composition. These nanomaterial delivery vehicles can also be coated with polymers, such as polyethylene glycol, to increase their half-life in the blood circulation, prevent opsonizing proteins from adhering to the nanomaterial surface, and reduce rapid metabolism and clearance. Moreover, the use of nanomaterials for drug delivery may minimize adverse effects by preventing the nonspecific uptake of therapeutic agents into healthy tissues.