Performing single-cell surgery with a laser-powered nanoblade.

Mitochondria, often called the cell’s energy powerhouse, are small organelles which reside in a cell’s cytoplasm and convert food into energy or building blocks.  Mutations in mitochondrial DNA, or mtDNA, can cause devastating diseases that mainly affect tissues and cells with high-energy demands.  Although specific mtDNA diseases are rare, the collective prevalence of mtDNA diseases from all types of mtDNA mutations is estimated to be 1 in 5,000 people.

To study this aspect of cells, researchers need the ability to take the innards out, manipulate them, and put them back, a feat yet to be achieved.  Now, researchers from UCLA have developed a novel ‘nanoblade’ that can slice through a cell’s membrane to insert mitochondria. The team state that their new technology could pave the way for specific research on how and why these diseases occur, and point to pathways to develop treatments.  The opensource study is published in the journal Cell Metabolism.

Previous studies show that human mitochondria produce ATP and metabolites to support development and maintain cellular homeostasis. Mutations in mtDNA occur mainly in the 24 non-coding genes, with specific mutations implicated in early death, neuromuscular and neurodegenerative diseases, cancer, and diabetes. A significant barrier to new insights in mitochondrial biology and clinical applications for mtDNA disorders is the general inability to manipulate the mtDNA sequence.  The current study demonstrates that mitochondria with healthy mtDNA can be delivered into cells with damaged mtDNA using a photothermal nanoblade.

The current study developed a nanoblade apparatus consisting of a microscope, laser, and titanium-coated micropipette to act as the blade, operated using a joystick controller. Results show that when a laser pulse strikes the titanium, the metal heats up, forming a bubble which punctures the cell membrane and creates a passageway several microns wide which the mitochondria can be pushed through. Data findings show that the cell then rapidly repairs the membrane defect.

The lab used the nanoblade to insert tagged mitochondria from human breast cancer cells and embryonic kidney cells into cells without mitochondrial DNA. Results show that the mitochondria had been successfully transferred and replicated by 2% of the cells, with a range of functionality.  The group state that their new approach for mitochondrial transfer into cells could open new possibilities for understanding how specific mtDNA mutations alter cell metabolism and potentially provide a way forward in treating specific mtDNA diseases.

The team surmise that their findings show the photothermal nanoblade can open a micron-sized pore through a cell membrane by utilizing an ultrafast laser-induced cavitation bubble for precision cutting.  They go on to add that this process also keeps cells alive as the nanoblade tool never enters the cell; it is in this way that the delivery of large-sized, slow-diffusing cargo, such as mitochondria can be achieved.  For the future, the researchers are now engineering an approach that incorporates the nanoblade into a high-throughput system that could deliver cargo, such as mitochondria, into as many as 100,000 cells per minute.

Source: UCLA