Nanoparticles Working Together

A two-component, nanoparticle-based system efficiently pinpoints and delivers drugs to tumor cells in mice by using blood-clotting enzymes to enable the components to communicate, according to a report in Nature Materials (DOI: 10.1038/nmat3049).

Developed by a team led by Sangeeta N. Bhatia, a bioengineer at MIT, the communicating particles are able to deliver 40 times as high a dose of drug as one type of particle can deliver by itself. Although “sequential dosing schemes have been tried before with particles” that bind one another rather than communicate, Bhatia says, they “have lacked the signal amplification of our method.” This approach could enable physicians to administer to patients a smaller amount of chemotherapeutics than is currently used, thus reducing the side effects of treatment.

The system consists of two types of nanoparticles: polyethylene glycol-coated gold nanorods and cancer-drug-bearing liposomes tagged with a peptide that binds to an enzyme in the blood-clotting cascade.

First, the researchers inject mice with the nanorods. When they shine near-infrared light on the rodents’ tumors, the light locally heats the nanorods that find their way into the tumor. The heat damages the tumors’ blood vessels and initiates clotting. The researchers then inject the mice with the tagged liposomes loaded with the cancer drug doxorubicin.

As people in distress might send a flare to direct rescuers to their location, the nanorods direct the drug-carrying liposomes to the tumor through the clotting enzyme to which the liposomes are designed to bind.

In addition to delivering a higher concentration of doxorubicin to tumors than liposomes alone can, the two-component nanosystem also prevented tumor growth in mice for more than 20 days after treatment, the researchers show.

“This work demonstrates the innate benefits that can be offered through the use of different nanoparticles united into one treatment strategy,” says Dean Ho, a biomedical engineer at Northwestern University. Future studies, he says, should illuminate a spectrum of diseases to which scientists can apply this coordinated approach.