Topic Overview:
Carbon nanotubes, hollow single-walled cylinders composed of carbon atoms that are approximately 100,000 times smaller than the size of a human hair, are generating considerable interest and excitement for their potential application in biomedical sensing, molecular diagnostics, and drug delivery. Their ability to interact with individual biomolecules while maintaining an interface with traditional microelectronics makes for a unique platform from which to study molecular systems with unsurpassed sensitivity.

As an innovator in nanoelectronic sensor technology, Dr. Star is developing carbon nanotubes and nanocapsules for a variety of medical diagnostic and therapeutic purposes. For example, Star has shown that by “decorating” carbon nanotubes with various polymer, metal, and semiconducting nanoparticles, selective detection of exhaled breath components that serve as biomarkers for health and disease can be achieved. He has developed a number of breath analyte carbon nanotube sensors, including oxygen and carbon dioxide to measure ventilation, nitric oxide to gauge asthma severity, and hydrogen sulfide to detect foul breath. The sensors have the added feature of being able to function inside a handheld device such as a battery-operated breath analyzer, conferring practical advantages of compact size, portability, and low cost that are especially appealing to the home medical diagnostics and care industries.

Molecular screening using carbon nanotubes is another area of exploration currently under way in the Star lab. Traditional methods rely on optical detection using fluorescent-labeled oligonucleotides and bulky, expensive microscope equipment. By attaching DNA probe strands to the surface of a carbon nanotube, Star demonstrated label-free detection of hybridization of specific DNA sequences. To illustrate the practical utility of this new nanoelectronic detection method, Star developed an allele-specific assay to detect the presence of the H63D mutation in the HFE gene that is responsible for hereditary hemochromatosis.

The inherent capacity of carbon nanotubes to form nanocapsules containing organic materials and particles makes drug delivery and energy storage yet another promising biomedical application. In a proof of concept, Star and his colleagues demonstrated a novel and chemically inert encapsulation method for the confinement of commercially available gold nanoparticles within graphitic nanocapsules. They also showed that coating of nanocapsules with phospholipids stimulates targeted engulfment of the nanocapsules in vivo by lung alveolar macrophages in mice. The Star lab continues to investigate the factors and properties that affect a nanocapsule’s rate of uptake and promote bioenzymatic degradation after particle release.