Cancer affects all of us,

especially the ones that come back
over and over again.

The highly invasive 
and drug-resistant ones,

the ones that defy medical treatment,

even when we throw our best drugs at them.

Engineering at the molecular level,

working at the smallest of scales,

can provide exciting new ways

to find the most aggressive
forms of cancer.

Cancer is a very clever disease.

There are some forms of cancer,

which, fortunately, we've learned
how to address relatively well

with known and established drugs
and surgery.

But, there's some forms of cancer
that don't respond

to these approaches

and the tumor survives
or comes back,

even after an onslaught of drugs.

We can think of these
very aggresive forms of cancer

as kind of super villains in a comic book.

They're clever, they're adaptable,

and they're very good at staying alive.

And, like most super villains
these days,

their super powers come from
a genetic mutation.

The genes that are modified
inside these tumor cells

can enable and encode for new
and unimagined modes of survival,

allowing the cancer cell
to live through

even our best chemotherapy treatments.

One example is a trick 
in which a gene allows

a cell, even as the drug
approaches the cell,

to push the drug out before the drug
can have any effect.

Imagine the cell effectively
spits out the drug.

This is just one example
of the many genetic tricks

in the bad of our super villain, cancer.

All due to mutant genes.

So, we have a super villain
with incredible super powers

and we need a new and 
powerful mode of attack.

Actually, we can turn off a gene,

the key is a set of molecules
called siRNA.

siRNA are short sequences
of genetic code

that guide a cell to block
a certain gene.

Each siRNA molecule
can turn off a specific gene

inside the cell.

For many years since its discovery,

scientists have been very excited

about how we can apply
these gene blockers in medicine.

But, there is a problem.

siRNA works well inside the cell.

But if it gets exposed to the enzymes
that reside

in our bloodstream and our tissues,

it degrades within seconds.

It has to be packaged, protected
through its journey through the body

on its way to its final target
inside the cancer cell.

So, here's our strategy:

first, we'll dose the cancer cell
with siRNA, the gene blocker,

and silence those viral genes,

and they'll we'll whap (?) it
with a chemo drug.

But how do we carry that out?

Using molecular engineering,

we can actually design 
a super weapon

that can travel through the blood stream.

It has to be tiny enough
that it can get through the blood stream,

it's got to be small enough
to penetrate the tumor tissue,

and it's got to be tiny enough
to be taken up

inside the cancer cell.

To do this job well, it has to be
about one 100th the size

of a human hair.

Let's take a closer look
at how we can build this nanoparticle.

First, let's start with 
the nanoparticle core.

It's a tiny capsule that contains
the chemotherapy drug.

This is the poison that will
actually end the tumor cell's life.

Around this core, we'll wrap
a very thin,

nanometer-think blanket
of siRNA.

This is our gene blocker.

Because siRNA is strongly negatively charged,

we can protect it with a nice
protect layer

of postively charged polymer.

The two oppositely charged molecules
stick together throough charge attracttion,

and that provides us with a protective
layer