© Cornell University

Schematic representation of a Cornell Dot, with several molecules of a fluorescent rhodamine dye encapsulated in the center. The dye has been modified with a group that links to the encapsulating silicon.

What is 30 times brighter than fluorescent markers, impervious to photobleaching, and won't leach heavy metals and other toxins into biological samples? Why, Cornell dots, of course – Ulrich Wiesner's attempt to make a cheaper, safer, and brighter biological marker.1

Cornell dots, named for the university where Wiesner is a professor of materials science and engineering, are molecules of fluorescent dyes encapsulated in a silica shell. Wrapping the dye in glass keeps the dyes' fluorophores from dissolving in the biological sample. The surface of the glass beads can be coated with any of a variety of ready-made "targeting molecules" (for instance, antibodies) matched to specific sites in a sample. By aggregating the beads at...

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