However, detection is challenging without good imaging agents; contrast materials which when injected into patients, allow for imaging such as MRI and CT to function with better sensitivity and specificity, enabling medical professionals to diagnose with accuracy, and for surgeons to identify the exact margins of tumors.
"For instance, if the problem is colon cancer, this is detected via endoscopy," Zavaleta said. "But an endoscope is literally just a flashlight on the end of a stick, so it will only give information about the structure of the colon - you can see a polyp and know you need to take a biopsy."
"But if we could provide imaging tools to help doctors see whether that particular polyp is cancerous or just benign, maybe they don't even need to take it," she said. Illuminated nanoparticles move through a blood vessel to find cancer. The coloring dyes were incorporated into nanoparticles to allow for more sensitive imaging contrast when identifying cancerous cells.
To achieve this, the team has discovered a unique source of optical contrasting agents from the household coloring dyes and pigments that we routinely encounter. These "optical inks" can be attached to cancer-targeting nanoparticles to improve cancer detection and localization.
The dyes and pigments were discovered from common coloring agents that already have U.S. Food and Drug Administration (FDA) approval, which the team hopes may enable them to be more easily and safely implemented in imaging practice.
One of the safety challenges of imaging using nanoparticles, is that often these nanoparticles can have a prolonged retention in organs like the liver and the spleen, which are responsible for trying to break down the nanoparticle. Because of these safety concerns, it's crucial to consider biodegradable nanomaterials. Currently, there are a limited amount of optical contrast agents approved for clinical use.
The team has developed a nanoparticle that will carry these highly pigmented imaging agents as a "payload." Zavaleta said the particles are of a specific size that enables them to passively penetrate into tumor areas, but can also be retained due to their size. Most of the imaging contrast agents used in the clinic today are small molecule dyes.
"With small molecules, you may be able to see them accumulate in tumor areas initially, but you'd have to be quick before they end up leaving the tumor area to be excreted," Zavaleta said. "Our nanoparticles happen to be small enough to seep through, but at the same time big enough to be retained in the tumor, and that's what we call the enhanced permeability and retention effect."
The nanoparticle can also be "decorated" with a larger payload of the dye than previous small molecule imaging agents, which the team has shown under fluorescence imaging leads to brighter signal and significant localization of the nanoparticles in tumors.
"If you encapsulate a bunch of dyes in a nanoparticle, you're going to be able to see it better because it is going to be brighter," Zavaleta said. "It's like using a packet of dyes rather than just one single dye."
MEDICA-tradefair.com; Source: University of Southern California
