The Carney Lab is part of the Department of Biomedical Engineering at the University of California, Davis.
Using extracellular vesicles (EVs) to engineer better diagnostics and therapeutics
EVs are a heterogenous grouping of nanoparticles released by every type of cell ever tested, including those comprising humans, plants, bacteria, yeast, and so on. They are commonly referred to as exosomes, but now we appreciate that exosomes only represent a fraction of the total vesicles in circulating biofluids (like blood, saliva, etc), thus "EV" is more appropriate umbrella term.
We recently published a review in Nature Nanotechnology on the topic of heterogeneity of EVs, and how it can be exploited for increasing their potential in drug delivery and therapeutics.
EVs are like biological taxicabs, responsible for trafficking important biomolecular messengers between cells. Cancer cells hijack the EV communication pathway for nefarious purposes. Cancer cell EVs can reprogram immune cells to evade detection or "terraform" distant sites in the body to help create ideal niches for metastatic invasion. These behaviors severely impede effective treatment and management of cancer.
Early detection translates to more options for treatment, and better outcomes for patients
And yet, it's their role in cancer that provides us with an excellent opportunity for diagnostics. Since these tiny biological nanoparticles can be found in very high numbers in blood, saliva, sweat, urine, cerebrospinal fluid and many other biofluids, and considering that their molecular payload indicates their function, EVs are excellent candidates for the next-generation of disease biomarkers that are more effective. Many projects in our lab center around fishing out the needle-in-the-haystack cancer-associated EVs amongst the healthy background to detect cancer earlier than is currently possible. Here are UC Davis, we are collaborating with numerous physicians and surgeons at the Medical Center to collect patient samples and use them to develop and validate our new platforms.
Learning the lessons from EVs to improve targeting and cell uptake of synthetic nanoparticles
We are interested in studying the mechanisms that EVs use to target and penetrate tissues and cells of their choosing. These natural vesicles have been perfected by nature during the last hundreds of millions of years, and can teach us how to engineer better drug delivery systems. A current major barrier in drug delivery is how to effectively target only the cells you want, after navigating a series of protective barriers throughout the body. EVs do this naturally! But how? We don't know! This is one of the exciting directions we are exploring...
Raman spectroscopy and nanoplasmonics - our tools to detect EVs
EVs 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. In our 2015 study, we demonstrated that single vesicles from cancer EVs look different from healthy ones (they have an altered level of cholesterol). It's also possible to perform such optical trapping after labeling EVs with fluorescent dyes to better visualize them as we demonstrated in our 2017 publication in ACS Analytical Chemistry. This is an exciting tool to dig into the chemical composition of EVs, and the scientists responsible for inventing optical tweezers won the Physics Nobel Prize in 2018!
If you are interested in the details of performing label-free Raman analysis of EVs, check out Prof. Carney's massive open online course (MOOC) on the topic (this lecture was performed as part of the educational outreach MOOC III program of the International Society for Extracellular Vesicles):
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, or even handheld portable devices. Yet in general, Raman scattering is very weak, often necessitating long measurements and expensive equipment to obtain useful spectra. However, Raman scattering signal can be significantly boosted -- up to even 14 or 15 orders of magnitude (!) -- simply by putting your sample in the vicinity of a nanostructured plasmonic material, like 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. We recently reviewed all the cool and modern studies using nanoplasmonics to analyze EVs. Bottom line: there are some interesting results to date, but we have our work cut out for us to validate these new techniques to the point that we can get them the clinic to help patients.
We've recently reported the development of a new inexpensive, hybrid nanomaterial suitable for analyzing EVs that shows great promise for analyzing cancer patient samples. Currently we are exploring the application of novel hybrid nanomaterials with unique plasmonic characteristics to greatly increase the sensitivity of EV detection and characterization using this SERS effect. You can read more this NIH funded project here. This approach could significantly boost the sensitivity and specificity of EV-based cancer diagnostics platforms to levels appropriate for clinical adoption.
Funding
We acknowledge generous funding from the following agencies:
- National Science Foundation (NSF)
- National Institutes of Health (NIH)
- HNC SPORE at UC Anschutz
- Environmental Health Sciences Center (EHSC)
- American Cancer Society (ACS)
- Ovarian Cancer Education and Research Network (OCERN)
- UC Davis Comprehensive Cancer Center’s Women’s Cancer Care & Research (WeCARE) program.