Cloaking strategy makes nanoparticles look, act like cells

BY CLOAKING nanoparticles in the membranes of white blood cells, scientists at The Methodist Hospital Research Institute (Houston, Texas) may have found a way to prevent the body from recognizing and destroying them before they deliver their drug payloads. The group describes its "LeukoLike Vectors", or LLVs, in the January issue of Nature Nanotechnology.

"Our goal was to make a particle that is camouflaged within our bodies and escapes the surveillance of the immune system to reach its target undiscovered," said Ennio Tasciotti, Ph.D., the study's principal investigator and co-chair of the Department of Nanomedicine and is the director of the Surgical Advanced Technology Lab at The Methodist Hospital. "We accomplished this with the lipids and proteins present on the membrane of the very same cells of the immune system. We transferred the cell membranes to the surfaces of the particles and the result is that the body now recognizes these particles as its own and does not readily remove them."

Nanoparticles can deliver different types of drugs to specific cell types, for example, chemotherapy to cancer cells. But for all the benefits they offer and to get to where they need to go and deliver the needed drug, nanoparticles must somehow evade the body's immune system that recognizes them as intruders. The ability of the body’s defenses to destroy nanoparticles is a major barrier to the use of nanotechnology in medicine. Systemically administered nanoparticles are captured and removed from the body within few minutes. With the membrane coating, they can survive for hours unharmed.

"Our cloaking strategy prevents the binding of opsonins -- signaling proteins that activate the immune system," Dr Tasciotti said. "We compared the absorption of proteins onto the surface of uncoated and coated particles to see how the particles might evade the immune system response."

Dr Tasciotti and his group took metabolically active leukocytes (white blood cells) and developed a procedure to separate membranes from cell innards. By coating their nanoparticles with intact membranes in their native composition of lipids and proteins, the researchers created the first drug-carrying nanoparticles that look and act like cells -- leukolike vectors.

"Using the membranes of white blood cells to coat a nanoparticle has never been done before," he said. "LLVs are half man-made -- the synthetic silicon core -- and half made of man -- the cell membrane."

SNEAKERS