Affordable Fluorescence

We all love the beauty of fluorescence, as neatly highlighted by the prevalence of fluorescent images in the Node’s recent Development cover competition.

Such aesthetic data comes at a price however; expensive mercury vapour lamps, or lasers are integral components of the fluorescent microscope. These powerful light sources provide energy which is absorbed by the fluorophore, and subsequently re-emitted as fluorescence. It was believed that the cheaper halogen lamps found on standard bright field microscopes simply lacked the power to do this effectively.

A recent PLoS one article has shown this to be untrue, potentially broadening the availability of fluorescent microscopy by lowering costs, and narrowing the “scientific gap” between developing and developed nations.

The Wakayama lab, from RIKEN CDB, fitted excitation and emission filters to both inverted and upright halogen lamp microscopes, these were then used to examine specimens labelled using fluorescently tagged secondary antibodies. The results are impressive: the presented images are almost as good as those obtained using a mercury vapour lamp.

Cdx2 (green) and Oct3/4 (red) antibody labelled mouse blastocyst- imaged using a halogen-lamp microscope

Halogen lamp microscopes typically have a single light source, and inserting a filter in this way would normally disable standard bright field illumination, a major limitation preventing effective manipulation of fluorescent samples. This technical obstacle was overcome by clever design. The excitation filter is of smaller diameter than the condenser, thus unfiltered light can pass around its periphery under the control of a movable diaphragm.  In this way the single halogen lamp source can simultaneously provide fluorescent and bright field illumination. Practical applications of the apparatus were demonstrated in the article by the removal of fluorescently tagged chromosomes from mouse and bovine oocytes.

The pages of the Node itself are testament to the power of fluorescent imaging to inspire and delight. Wakayama’s team are hoping that inexpensive modification of existing halogen microscopes in schools and teaching labs will help bring science to life for the next generation of budding researchers.

Yamagata K, Iwamoto D, Terashita Y, Li C, Wakayama S, Hayashi-Takanaka Y, Kimura H, Saeki K, & Wakayama T (2012). Fluorescence cell imaging and manipulation using conventional halogen lamp microscopy. PloS one, 7 (2) PMID: 22347500

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