Tuesday, 17 June 2014

Nanoshell Shields Foreign Enzymes Used to Starve Cancer Cells from Immune System

Nanoengineers at the University of California, San Diego have developed a
nanoshell to protect foreign enzymes used to starve cancer cells as
part of chemotherapy.

Enzymes are naturally smart machines that are responsible for many
complex functions and chemical reactions in biology. However, despite
their huge potential, their use in medicine has been limited by the
immune system, which is designed to attack foreign intruders. For
example, doctors have long relied on an enzyme called asparaginase to
starve cancer cells as a patient undergoes chemotherapy. But because
asparaginase is derived from a nonhuman organism, E. Coli, it is quickly
neutralized by the patient’s immune system and sometimes produces an
allergic reaction. In animal studies with asparaginase, and other
therapeutic enzymes, the research team found that their porous hollow
nanoshell effectively shielded enzymes from the immune system, giving
them time to work.

The shell’s pores are too small for the enzyme to escape but big enough
for diffusion of amino acids that feed cancer cells in and out of the
particle. The enzymes remain trapped inside where they deplete any amino
acids that enter. Photo courtesy of Inanc Ortac.

Asparaginase works by reacting with amino acids that are an essential
nutrient for cancer cells. The reaction depletes the amino acid,
depriving the abnormal cells from the nutrients they need to
proliferate.

“Ours is a pure engineering solution to a medical problem,” said Inanc
Ortac (Ph.D. '13), who developed the technology as part of his doctoral
research in the laboratory of nanoengineering professor Sadik Esener at
UC San Diego Jacobs School of Engineering.

The nanoshell acts like a filter in the bloodstream. The enzymes are
loaded into the nanoparticle very efficiently through pores on its
surface and later encapsulated with a shell of nanoporous silica. The
shell’s pores are too small for the enzyme to escape but big enough for
diffusion of amino acids that feed cancer cells in and out of the
particle. The enzymes remain trapped inside where they deplete any amino
acids that enter. "This is a platform technology that may find applications in many
different fields. Our starting point was solving a problem for cancer
therapeutics,” said Ortac.