The Carney Lab is part of the Department of Biomedical Engineering at the University of California, Davis.
We engineer nanoplasmonic materials and substrates for developing new diagnostic platforms for rapid and accurate detection and monitoring of cancer. We are particularly focused on isolation and analysis of nano-sized circulating particles called extracellular vesicles (EVs).
A major class of EVs, known as exosomes, are released by every type of cell ever tested, including those comprising humans, plants, bacteria, and yeast. They are like biological taxicabs, responsible for trafficking important biomolecular messengers between cells. Cancer cells hijack the exosome communication pathway for nefarious purposes. They can reprogram immune cells to evade detection or “terraform” distant sites in the body to create ideal niches for metastatic invasion. Such behaviors severely impede effective treatment and management of cancer.
And yet, it’s their role in cancer that provides us with an excellent opportunity to exploit them. Since they can be found in very high numbers in blood, urine, saliva, and other biofluids, and their molecular payload indicates their function, exosomes are excellent candidates for next-generation disease biomarkers that are more effective than current strategies.
Exosomes are extremely small and highly chemically diverse. In circulation, healthy and diseased vesicles are all mixed together. It is clear that novel approaches are needed to distinguish and characterize cancer-associated EVs, especially at early stages of the disease, when they are present in very low number. To do this, we are exploiting the unique interaction of light with nanoscale biological matter to make rapid, label-free measurements.
Upon interacting with light, the vibrations of the molecules comprising EVs can subtly alter the energy of the light in a highly specific manner. Such Raman scattered photons can be sensitively collected and analyzed using state-of-the-art microscopes. The resulting spectra serve as chemical fingerprints that readily reflect cancer-specific features of the analyzed samples in real-time.
We have taken this approach a step further by performing Raman spectroscopy analysis on single vesicles, made possible by trapping them with a highly focused laser. It is possible to perform such optical trapping after labeling exosomes with fluorescent dyes to better visualize them. Here are our optical tweezers in action:
Nanoplasmonics – SERS
Raman scattering has many advantages: it’s label-free, gives unique spectroscopic information to fingerprint chemicals, and can be readily adopted to clinical platforms. Yet in general, Raman scattering is very weak, often necessitating long measurements to obtain useful spectra. However, Raman scattering signal can be significantly boosted — up to even 14 or 15 orders of magnitude — simply by being placed very closely to a nanostructured plasmonic material, such as a gold nanoparticle or nano-roughened silver surface. This effect, known as Surface Enhanced Raman Scattering, or SERS, overcomes the traditional inherent weakness of Raman techniques.
Currently we are exploring the application of novel hybrid nanomaterials with unique plasmonic characteristics to greatly increase the sensitivity of exosome detection and characterization using the SERS effect. This approach could significantly boost the sensitivity and specificity of exosome-based cancer diagnostics platforms to levels appropriate for clinical adoption.
Carney Lab Mind Map
The following map summarizes our major avenues of research. We will continue to update our site as our experiments evolve, so be sure to come back again in the future!