Better cancer-killing drill developed

Scientists are getting closer to perfecting molecule-sized motors that drill through the surface of cancer cells, killing them in an instant without damaging the healthy tissue.

The researchers at Rice University and North Carolina State University in the US successfully activated the motors with precise two-photon excitation via near-infrared light.

Unlike the ultraviolet light they first used to drive the motors, the new technique, described in the journal ACS Nano, does not damage adjacent, healthy cells.

In 2017, the same team reported the development of molecular motors enhanced with small proteins that target specific cancer cells.

Once in place and activated with light, the paddle-like motors spin up to three million times a second, allowing the molecules to drill through the cells' protective membranes and killing them in minutes.

Since then, researchers have worked on a way to eliminate the use of damaging ultraviolet light.

In two-photon absorption, a phenomenon predicted in 1931 and confirmed 30 years later with the advent of lasers, the motors absorb photons in two frequencies and move to a higher energy state, triggering the paddles.

"Multiphoton activation is not only more biocompatible but also allows deeper tissue penetration and eliminates any unwanted side effects that may arise with the previously used UV light," said Robert Pal of Durham University in the UK.

The researchers tested their updated motors on skin, breast, cervical and prostate cancer cells in the lab.

Once the motors found their targets, lasers activated them with a precision of about 200 nanometres.

In most cases, the cells were dead within three minutes, they said.

The researchers believe the motors also drill through chromatin and other components of the diseased cells, which could help slow metastasis.

Since the motors target specific cells, work is underway to adapt them to kill antibiotic-resistant bacteria as well, said James Tour from Rice University.

"We continue to perfect the molecular motors, aiming toward ones that will work with visible light and provide even higher efficacies of kill toward the cellular targets, he said.