Photoacoustic imaging using nanoparticles to both image tumors and reveal information about their chemical environment is the subject of a perspective by Professor Raoul Kopelman in ACS Analytical Chemistry. A specific illustration of this technique for measuring oxygen levels in tumors that was recently published in ACS Nano.
When used with photoacoustic imaging, nanoparticles provide way to investigate tumors in living organisms in real time, even if the tumor is deep within an organism, Kopelman explains.
Photoacoustic imaging uses light and ultrasound to elicit a response from a signal molecule and to translate this response into precise information about a tumor and its chemical environment.
The nanoparticles’ key role is to protect the signal molecule until it is transported to the tumor. Without the nanoparticles, the signal molecule could react with other molecules in the blood before it even reaches a tumor, preventing its ability to give accurate information about the tumor.
Improving on exisiting diagnostic techniques
The combination of nanoparticles and photoacoustic imaging could give clinicians better information than that available with established techniques. For example, Kopelman explains, “CT and MRI have been around for a while. Each has had very important impacts on medicine, but they only provide structural imaging.”
Some techniques, like locally inserted electrodes, can provide chemical information but the electrodes can only be placed in some locations. “The patient’s chemical information provided to doctors has been lacking any details regarding its body location, distribution and time behavior," Kopelman points out. "Mostly, just blood and urine chemical tests have been available, and this hasn’t changed in a long time.”
In contrast, nanoparticles have the potential to find their way to all pertinent locations in the body and to provide real-time chemical information when used with photoacoustic imaging. For example, these nanoparticles have been used to more-effectively detect different chemicals in the environment around a tumor like oxygen (O2), acidity (low pH), and potassium ions (K+). Early detection could lead to more informed treatment decisions, specifically regarding choices of chemotherapy, radiation therapy, or immunotherapy. Kopelman puts it simply, “Different tumors need different methods of targeting.”
In the end, this combination of nanoparticles and photoacoustic imaging could change the way that cancer is diagnosed and treated. “The importance of this research is to provide critical chemical information about the tumor microenvironment to optimize doctors' decision-making on their choice of therapies for cancer patients,” Kopelman explains. "Rather than a 'one fits all' treatment protocol for cancer patients, this approach would allow for personalized medicine, a treatment that is tailor-made for the tumor of the patient, thus minimizing adverse side effects while maximizing the effectiveness of the therapy.”
ACS Analytical Chemistry Chemical Imaging in Vivo: Photoacoustic-Based 4-Dimensional Chemical Analysis
Chang H. Lee, Jeff Folz, Joel W. Y. Tan, Janggun Jo, Xueding Wang, and Raoul Kopelman Anal. Chem. 2019, 91, 2561−2569
ACS Nano "In Vivo Photoacoustic Lifetime Based Oxygen Imaging with Tumor Targeted G2 Polyacrylamide Nanosonophores"
Authors: Janggun Jo, Chang Heon Lee, Jeff Folz, Joel W. Y. Tan, Xueding Wang, Raoul Kopelman
UM Biomedical Engineering article on this technique "Reading cancer’s chemical clues"