but they're very tiny particles now.

但他们是很小的颗粒
In section this afternoon we'll talk about how you make these kinds of particles,

今天下午的讨论课我们要讲如何制作这些颗粒
and you'll actually be able to make some.

你们可以来实际制作一些
These particular ones are made of the same kind of polymer that slowly degrades,

这些也是用同样的可缓慢降解的聚合物制成的
but they're very small, they're a micron or so in diameter.

但却很小直径大约在一微米左右
They're much,much smaller than a needle and they can be injected through a needle.

远远小于针的直径所以他们可以被注射
You just imagine suspending these particles which look like dust in water,

想象一下这些像悬浮在水中灰尘一样的颗粒
and then injecting them through a needle.

然后用针头注射进体内
They also have the property that you can put drugs in them

你同样可以往这些颗粒中
at fairly high concentration and the drugs are released slowly over time.

加入很高浓度的药物这些药物会缓慢释放
If I put a needle into a tissue and introduce these particles,

如果用针头把这些颗粒注射进组织
the particles will sit there at the tissue site

它们就会留在组织里