Quantum dots – a versatile tool in plant science?

Quantum dots (QDs) have been introduced as a promising new tool in life sciences, because of their unique optical properties [1]. They are highly stable during excitation and have characteristic absorption and emission spectra [2]. The emission peak of these nanoparticles is comparatively narrow and the dots fluoresce brighter than organic fluorescent dyes. Thus particle visibility is enhanced and weaker laser intensity is required for the imaging process. QDs can be excited using different wavelengths from UV up to the emission wavelength. Hence it is possible to excite simultaneously QDs emitting at different wavelengths potentially facilitating a simpler handling of multicolor-labelled samples.Initial attempts to synthesize semiconductor crystals resulted in QDs trapped in glass [2-4]. Later, nanoparticles were developed that could be dispersed in various solvents and whose surface could be derivatized. After hydrophilic coating of QDs with mercaptoacidic acid, dehydrolipoic acid or other reagents, nanocrystals became applicable in biology [5]. The core of the quantum dot particle is composed of a mixture of cadmium and selenide. This sphere, having a diameter of 20 to 55 ？ [6], is coated with 1–2 monolayers of ZnS measuring 3,1 ？.Proteins, antibodies, DNA or other molecules of interest can be attached to QDs allowing a wide range of applications in life sciences [7]. The complete QD-streptavidin conjugate has a diameter of 10 to 15 nm [8]. Hence quantum dots have been employed in live cell imaging [1,9], diagnostic and therapeutic purposes [10], immunohistochemistry [11] and in fluorescence in situ hybridisation (FISH) experiments [12,13]. However, until now there have been no reports of applications of QDs in plant research [14,15]. In order to test whether the application of nanoparticle techniques could improve the sensitivity of in situ hybridisation on plant chromosomes, we conducted a range of comparative test experiments. In addition QDs were employed for