Vaccines in use today are designed to protect us from malicious microbial invaders, but some of the most devastating diseases around are born within are own bodies.

Cancer is one of those diseases, and it has led scientists to design a vaccine that is unlike any of the ones you've winced at in the doctor's office as a kid.

Making the vaccines involves packing tumor cells harvested from cancer patients into an intricate, ultra-compressible spongy material known as a cryogel. That squishy package of cells and other components then gets loaded into a syringe and squeezed through the needle back into the patient's body, where it triggers the immune system to attack the cancer cells, according to a paper published in the journal Nature Communications.

Vaccines in general work by setting off an immune response. They provide an essentially harmless sample of the virus, bacteria, or in this case, cancer cells that cells in the immune system can get a head start on training an army specialized for fighting off that particular threat. The soldiers in this army are called antibodies, which are molecules customized for capturing a specific type of cell or particle so that other components of the immune system can destroy it.

That's why, along with the tumor cells from the patient, the scientists load molecules that stimulate the immune system into the cryogel. Previous designs for cancer vaccines have turned to genetically engineering the cancer cells themselves to spark an immune system response, but this new approach is simpler and less expensive.

Those special immune-stimulating molecules tell immune cells to come over and check out the cancer cells trapped in the cryogel. The immune system then starts producing antibody soldiers ready to seek and destroy cells that match the genetic signature they "remember" encountering in the cryogel injected in the vaccine.

The cryogel itself is important because it is highly structured, yet is mostly empty space. Cryogels are a kind of hydrogel, materials that get their name from their remarkable ability to absorb many times their weight in water — a fully-soaked hydrogel is 99 percent water. The structure of the cryogel affords the scientists a high degree of control over the release of the immune-stimulating molecules while still being squishy enough to fit through the tip of a needle for minimally invasive administration.

So far, the researchers have only tested the vaccine in animals, but the results are encouraging. When they tried out the vaccine using cells from melanoma tumors, they saw a strong immune response in the animals that caused tumors to shrink. They also found evidence that the vaccine may even protect animals from growing tumors in the first place.

Even if this cancer vaccine doesn't pan out, the intricate structure of cryogels could be used for other purposes as well, according to the researchers, including drug delivery.

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