Chemiluminescence

Shining bright without light

In the world of microscopy, fluorescence is king, but chemiluminescence is snapping at its heels.

The ability to analyse samples by making them glow in the dark using chemically luminescent molecules has great potential, if for no other reason than it has fewer drawbacks.

If you don’t need to use direct light, there is no risk of autofluorescence, for example, or of damaging light-sensitive samples.

Chemiluminescence has been challenging and not technically viable, however, because it has been difficult to control. But Australian researchers may now have the answer.

In a paper in the journal Cell Reports Physical Science, a team from Curtin University describes a “technically simple solution” for converting chemical energy into light energy only at specific sites. The light stimulus can excite a luminescent dye under effectively dark conditions.

“Most biological cells and chemicals generally do not like exposure to light because it can destroy things – similar to how certain plastics lose their colours after prolonged sun exposure, or how our skin can get sunburnt,” says lead researcher Yan Vogel.

“The light that shines on the samples is often too damaging for the living specimens and can be too invasive, interfering with the biochemical process and potentially limiting the study and scientists’ understanding of the living organisms.”

Co-author Simone Ciampi says that to date two-dimensional control of chemical energy conversion into light energy has been difficult because there have been few tools available to trigger transient chemical changes at a specific microscopic site.

“Of the tools that are available, such as photoacids and photolabile protecting groups, direct light input or physical probes are needed to activate them, which are intrusive to the specimen,” he says.

“Our new method, however, only uses external light shining on the back of an electrode to generate localised and microscopic oxidative hot-spots on the opposite side of the electrode.

“Basically, the light shines on an opaque substrate, while the other side of the sample in contact with the specimen does not have any exposure to the external light at all. The brief light exposure activates the chemicals and makes the sample glow in the dark.”

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