Bio-Butterfingers

Semiconductor nanocrystals have been used to discover a host of new biomolecular phenomena because of their uniquely bright and stable florescence emission. Recently, a new class of nanocrystal – nanoplatelets – has excited researchers because of a number of potential applications from cellular imaging, to metastatic tracking, and drug delivery.

“Nanoplatelets have an emission band two to four times narrower than most other types of light emitters,” says Andrew Smith, assistant professor of Bioengineering at the University of Illinois at Urbana-Champaign, US. “This property could allow us to fluorescently tag two to four times more molecules simultaneously, which is very useful for studying cells and tissues.” But only if they are stable within biological solutions; typically, nanoplatelets aggregate in biological media because of the their unusual shape, losing fluorescence in the process.

Smith and his colleagues set out to overcome this caveat by developing lipoprotein-nanoplatelets (L-NPLs). “L-NPLs are a combination of lipoproteins and nanoplatelets, and are kind of structured like a microscopic Butterfinger candy bar,” says Smith. “The crispy peanut butter center is similar to the nanoplatelet – a flat sheet made out of a hard material; whereas surrounding it on all sides – like a chocolate covering – are the soft, organic lipoproteins and lipids.” And just like a Butterfinger hides its 270 calories and 11 grams of fat in a relatively innocuous chocolate coating, the lipoproteins disguise nanoplatelets as something that cells would like to eat, which Smith says they do vigorously. Most importantly, the lipoprotein layer allows nanoplatelets to retain their fluorescent properties in vivo.

“It’s the first time that anyone has been able to demonstrate the use of nanoplatelets and quantum well-like structures in cells,” says Smith. “But perhaps more importantly, we uniquely found that they enter cells rapidly, which sets the stage for their use to optically encode cells and to explore the unknown interactions between flat materials and biology.”

The researchers are also confident that L-NPLs could be used to track metastatic cancer cells in the body or deliver drugs to tumor cells. “Their efficiency of entry into cells is really striking, and this could potentially be an efficient way to transport things into cells, such as medicinal compounds, or DNA, that are traditionally hard to deliver,” says Smith.