Cancer-Seeking Microbubbles Make Tumor Cells Self-Destruct

Delivering large cancer drugs into tumor cells without damaging healthy tissue has long been a major challenge in oncology. Many promising therapies fail because their molecules are too large to enter cells efficiently or cause harmful effects in healthy tissues. Researchers have now developed an ultrasound-based technique that uses microscopic bubbles to temporarily open cell membranes, enabling targeted delivery of large cancer drugs directly into tumor cells.

A research team at Duke University (Durham, NC, USA) has developed a delivery platform called Sonoporation-assisted Precise Intracellular Nanodelivery, or SonoPIN. The method combines ultrasound and engineered microbubbles to create tiny, temporary openings in cell membranes, allowing large therapeutic molecules to enter targeted cancer cells. The researchers tested the approach using a class of emerging cancer drugs known as proteolysis-targeting chimeras (PROTACs). These molecules work by binding to specific disease-related proteins and recruiting enzymes that mark those proteins for destruction through the cell’s natural protein-degradation system.

In cancer cells, PROTACs can target the protein BRD4, which plays an important role in tumor growth and survival. Destroying this protein disrupts the cancer cells’ ability to reproduce and survive, effectively triggering cell death. However, PROTAC molecules are relatively large and typically struggle to enter cells. To overcome this challenge, the researchers attached microbubbles to cancer cells using synthetic nucleic acid strands designed to recognize specific receptors found on tumor cells.

When exposed to ultrasound, the microbubbles rapidly collapse, generating localized mechanical forces that create nanoscopic pores in nearby cell membranes. These temporary openings allow PROTAC molecules to enter the targeted cells before the membranes quickly reseal. In laboratory experiments, the researchers optimized ultrasound intensity and frequency to achieve efficient delivery. The findings, published in Proceedings of the National Academy of Sciences, showed that cancer cells exposed to the SonoPIN platform absorbed significantly more PROTAC molecules, glowing seven times brighter than cells treated with conventional delivery methods when fluorescent markers were attached to the drugs.

The targeted delivery approach produced notable results in benchtop experiments. Approximately 50 percent of the cancer cells exposed to the system self-destructed, while 99 percent of nearby non-targeted healthy cells remained viable. Because the technique relies on mechanical delivery rather than biological uptake mechanisms, it may enable the delivery of large therapeutic molecules that would otherwise struggle to penetrate cell membranes. This could expand the range of drugs that can be used to treat difficult cancers while reducing harmful off-target effects.

The research team plans to test the technology in animal models to evaluate its performance in living systems. The scientists have also applied for a patent covering the platform. If successful in future studies, the approach could involve injecting tumor-targeting microbubbles and therapeutic molecules into the bloodstream while directing ultrasound waves at specific tumor locations. This would allow clinicians to precisely deliver powerful treatments to cancer cells while minimizing damage to healthy tissues.

“Because SonoPIN relies on a mechanical delivery approach rather than biological engulfment, it could theoretically deliver therapeutics of almost any size,” said Tony Jun Huang, the William Bevan Distinguished Professor of Mechanical Engineering and Materials Science at Duke. “We would also be excited to see how it performs with therapeutics such as large gene-editing complexes.”

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