develop novel ‘dot’ system to improve cancer detection:

develop novel ‘dot’ system to improve cancer detection:

Context

• Researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) have developed a proof-of-concept nanosystem that dramatically improves the visualization of tumors.

Explanation

• The article published in Nature Communications mentions that the platform achieves a five-fold increase over existing tumor-specific optical imaging methods.
• This novel approach produces bright tumor signals by delivering “quantum dots” to cancer cells without any toxic effects.

Who developed it?

• Xiangyou Liu, Ph.D., and Gary Braun, Ph.D., developed the method in the laboratories of Kazuki Sugahara, M.D., Ph.D., additional assistant professor at SBP and adjunct associate research scientist at Columbia University, and Erkki Ruoslahti, M.D., Ph.D., distinguished professor at SBP.

What is Tumor Imaging?

• Tumor imaging is an integral part of cancer detection, treatment and tracking the progress of patients after treatment.
• This new method getting developed will contribute to more personalized and potentially more effective interventions to improve the clinical outcomes of cancer patients.

Details about the new method

• The new method utilizes quantum dots, QDs — tiny particles that emit intense fluorescent signals when exposed to light — and an “etchant” that eliminates background signals.
• The QDs are delivered intravenously, and some of them leave the bloodstream and cross membranes, entering cancer cells.
• Fluorescent signals emitted from excess QDs that remain in the bloodstream are then made invisible by injecting the etchant.

How does an etchant functions?

• The novelty of this developed nanosystem is how the etchant works.
• The etchant and the QDs undergo a “cation exchange” that occurs when zinc in the QDs is swapped for silver in the etchant.
• Silver-containing QDs lose their fluorescent capabilities, and because the etchant can’t cross membranes to reach tumor cells, the QDs that have reached the tumor remain fluorescent.
• Thus, the entire process eliminates background fluorescence while preserving tumor-specific signals.

How was this method developed?

• The method was developed using mice harboring human breast, prostate and gastric tumors.
• QDs were actively delivered to tumors using iRGD, a tumor penetrating peptide that activates a transport pathway that drives the peptide along with bystander molecules — in this case fluorescent QDs — into cancer cells.
• iRGD methodology was originally developed in Ruoslahti’s lab.

First of its kind

• This is one unique example of a background-destroying etchant being used to enhance the specificity of imaging.
• It was encouraging to achieve a tumor-specific contrast index (CI) between five- and ten-fold greater than the general cut-off for optical imaging, which is 2.5.

Way forward

• The focus will be on developing the novel nanosystem to work with routine imaging tests like PET scans and MRIs.
• A new company is in the process of being founded to further develop the platform for human use.