Scientists have developed a new cancer drug. So far, they have
tested it only on (36) animals. The drug is designed to
(37) and kill cancer cells but not healthy cells.
First, the drug enters the cancer and destroys the supply of blood. Then
it releases (38) to destroy the cancer ceils.
Researchers at the Massachusetts Institute of Technology in Cambridge
carried out the study. The (39) appeared in Nature
(40) . A school news release called the drug an "anti-cancer
smart bomb." Ram Sasisekharan is a professor at M.I.T. He says
his team had to (41) three problems. They had to find a way
to destroy the blood vessels, then to (42) the growth of new
ones. But they also needed the blood vessels to supply chemicals to destroy the
cancer. So, the researchers designed a two-part "nanocell". The
cell is (43) in nanometers, or one thousand millionth of a
meter. (44) . The scientists say it was small
enough to pass through the blood vessels of the cancer, but it was too big to
enter normal blood vessels. The surface of the nanocells also helped them to
avoid natural defenses. (45) . That cut off
the blood supply and trapped the nanocell inside the cancer. Then, the nanocell
slowly released chemotherapy drugs to kill the cancer cells.
(46) .
【参考答案】
The particle used was two hundred nanometers--much, much sma......