_TECHNOLOGY Molecular science

_Different Kind of Crystal Ball

A new method has been discovered for growing spherical crystals that could be used for drug delivery.

_Christopher Li

Li is a professor in the Department of Materials Science and Engineering in the College of Engineering and head of the Soft Materials Lab.

No two snowflakes are alike, they say. And some are very different, indeed.

A Drexel materials scientist has discovered a way to grow a spherical, microscopic crystal — like a snowflake but in a 3-D orb — in a lab that could be used to encapsulate medication for more effective delivery inside the body.

The discovery was detailed by Professor Christopher Li and lead author Wenda Wang, a ’15 Drexel graduate who is currently a post-doctoral researcher at Princeton University, along with other collaborators in a paper in Nature Communications.

Before now, crystals have grown in rigid, structured formations; think of how snowflake crystals are webs of straight lines connecting to form a grid.

Crystals form this way because their molecules are predisposed to align themselves in a way that links them via the strongest electrochemical bond available. But crystal formation is strongly influenced by the environment in which a crystal forms. Li uses this molecular property to engineer his hollow crystal spheres.

Early tests indicate that Li’s “crystalsomes” are a few hundred times stronger than liposomes, which makes them a sturdier option for medicine encapsulation.

His “crystalsomes” are named for their similarity to liposomes — tiny bubbles with the same membrane as cells that are being explored for use as biological packages for delivering drug treatments.

Li made his crystalsomes spherical by containing them inside a droplet. A rough equivalent of this would be forcing a single snowflake to form inside a tiny snow globe, rather than in the open expanse of the atmosphere.

To do this, the research team employed a little trick that you might recognize if you’ve ever tried to make vinaigrette. They created a tiny bubble of oil to encase water molecules. When the surfactant bubble was cooled to the appropriate temperature, the molecules inside began to crystalize. But rather than forming an angular web of connections, the molecules, instead, lined up along the interior of the oil bubble — crystallizing in a hollow, spherical shape.

With funding from the National Science Foundation, Li’s team is now exploring ways to control the shape and strength of the spheres by making them out of different molecules.