Liposomes, hollow spheres made of lipids, have been studied for years as a mechanism for delivering chemotherapy drugs to cancer cells. The problem is that the drugs can leak out of the liposomes before they reach their target, which reduces the dose to the tumor cells and increases side effects in non-cancerous cells. Now, a team of scientists have reported in ACS' Nano Letters that they found a way to stabilize the liposomes that involved embedding a stiff “nanobowl” inside.
Previously, researchers had tried several ways to keep liposomes from leaking, including using polymers to coat the surface or crosslinking lipids. The problem with these approaches is that they can change the properties of the liposomes, making them interact differently with the cells.
Chao Fang, Jonathan Lovell and colleagues set out to find a new way to stabilize the liposomes that keeps the surfaces intact. They did so by using “nanobowls,” which are tiny concave structures with a small opening that allows the drug to escape into the layers of the liposome once inside a tumor cell. The researchers thought that by assembling the lipid bilayer around the nanobowl, they could get the right structure that could physically support the liposome.
The team made silica nanobowls and loaded a chemotherapy drug into a water-filled center. The liposomes that were stabilized with the nanobowls were less leaky than their non-stabilized counterparts under sheer stress, similar to what’s found in blood vessels. In an experiment using mice, the mice had metastatic breast tumors transplanted inside them and they were injected with chemotherapy drugs, using both the nanobowl and a conventional method. The mice treated with nanobowls had smaller tumors than the other group, they lived longer, and there was no metastasis. The researchers believe that their new method is “easy for wide application and holds potential for clinical translation.”