Picture a few nasty cancer cells swimming stealthily alongside billions of healthy blood cells— it is difficult for clinicians to trap them and diagnose cancer affirmatively. Scientists from India and Germany have now surmounted this challenge — they have created ‘micro-rockets’ out of carbon-nanotubes to selectively capture such tumour cells from a large population of blood cells1.

Using a chemical ‘fuel’ that can propel these rockets up or down in an artificial cell suspension, the scientists have been able to trap and transport tumour cells to diagnose specific cancers. The micro-rockets can also be used to detect trace chemicals, deliver drugs and penetrate tissues during non-invasive surgeries, lead researcher Jayant Khandare told Nature India.

Scientists have earlier devised microfluidic devices to capture and isolate tumours but the devices have been slow and inefficient. It is difficult to detect tumour cells in cancer patients since for every millilitre of blood, only 10-100 tumour cells appear in a sea of about a billion normal blood cells.

Researchers from Actorius Innovations and Research, Maharashtra Institute of Pharmacy and Piramal Life Sciences Limited teamed up with peers from Institut für Chemie, Freie Universität Berlin to synthesise the new efficient micro-rockets. They loaded iron oxide nanoparticles on the inner surface of oxidized carbon nanotubes. On the outer surface of the rockets, they attached transferrin, a protein highly expressed on the cell membranes of specific cancer cells.

Researchers (from left) Jayant Khandare, Shashwat Banerjee and Ganesh Khutale.
The micro-rockets swam up or down in hydrogen peroxide-based aqueous solutions as also in biological fluids. “The nanoparticles worked as catalysts and broke down hydrogen peroxide, generating oxygen molecules that formed bubbles,” explains Khandare. When the bubbles dispersed, the micro-rockets moved down due to gravity. In a few seconds, the small bubbles united, increasing the bubble volume and propelling the micro-rockets up with their buoyancy. The researchers found that increasing hydrogen peroxide concentration increased the speed of the micro-rockets and vice-versa.

The task then was to see if the micro-rockets could capture tumour cells in an artificial cell suspension. The researchers tested the micro-rockets in a suspension that contained human colon tumour cells mixed with human peripheral blood mononuclear cells and hydrogen peroxide. The micro-rockets successfully captured about 85% of the cancer cells from the suspension in five minutes.

The micro-rockets could become a potential tool for non-invasive liquid biopsy at an early stage of metastasis, Khandare says.

The micro-rockets could be useful as an alternative isolation and detection strategy for circulating tumour cells, says Chitta Ranjan Patra who studies anticancer properties of nanoparticles at CSIR-Indian Institute of Chemical Technology, Hyderabad. However, the concept should be validated by identifying and capturing circulating tumour cells from the blood of cancer patients, he adds.

These tiny rockets could also be used to monitor chemical processes in various industries as they can isolate and degrade industrial pollutants, Khandare says.