Nanobubbles Kill or Modify Cells

Photo: Nanobubbles in cells

The unique use for tunable plasmonic nanobubbles developed in the Rice lab of Dmitri Lapotko shows promise to replace several difficult processes now used to treat cancer patients, among others, with a fast, simple, multifunctional procedure.

The research was carried out at Rice by biochemist Lapotko, research scientist and lead author Ekaterina Lukianova-Hleb and undergraduate student Martin Mutonga, with assistance from the Baylor College of Medicine (BCM), Texas Children’s Hospital and the University of Texas.

Plasmonic nanobubbles that are 10,000 times smaller than a human hair cause tiny explosions. The bubbles form around plasmonic gold nanoparticles that heat up when excited by an outside energy source – in this case, a short laser pulse – and vaporize a thin layer of liquid near the particle’s surface. The vapor bubble quickly expands and collapses. Lapotko and his colleagues had already found that plasmonic nanobubbles kill cancer cells by literally exploding them without damage to healthy neighbors, a process that showed much higher precision and selectivity compared with those mediated by gold nanoparticles alone, he said.

The new project takes that remarkable ability a few steps further. A series of experiments proved a single laser pulse creates large plasmonic nanobubbles around hollow gold nanoshells, and these large nanobubbles selectively destroy unwanted cells. The same laser pulse creates smaller nanobubbles around solid gold nanospheres that punch a tiny, temporary pore in the wall of a cell and create an inbound nanojet that rapidly “injects” drugs or genes into the other cells.

In their experiments, Lapotko and his team placed 60-nanometer-wide hollow nanoshells in model cancer cells and stained them red. In a separate batch, they put 60-nanometer-wide nanospheres into the same type of cells and stained them blue.

After suspending the cells together in a green fluorescent dye, they fired a single wide laser pulse at the combined sample, washed the green stain out and checked the cells under a microscope. The red cells with the hollow shells were blasted apart by large plasmonic nanobubbles. The blue cells were intact, but green-stained liquid from outside had been pulled into the cells where smaller plasmonic nanobubbles around the solid spheres temporarily pried open the walls.

Plasmonic nanobubble technology promises “a method of doing multiple things to a cell population at the same time,” said Malcolm Brenner, a professor of medicine and of pediatrics at BCM and director of BCM’s Center for Cell and Gene Therapy, who collaborates with the Rice team. “For example, if I want to put something into a stem cell to make it turn into another type of cell, and at the same time kill surrounding cells that have the potential to do harm when they go back into a patient — or into another patient — these very tunable plasmonic nanobubbles have the potential to do that.”; Source: Rice University