Antoine THILL
thill@ARBOIS.CEREGE.FR

I have used polystyrene latex beads from Molecular Probes and Interfacial Dynamics that absorbs both YOYO-1 and DAPI. YOYO absorbs nicely at 488 and emits at ~510 nm.

Neal Nicklaus
nnicklaus@cave.sarnoff.com

Molecular probes sells kits of labelled beads of various diameters.

-Rachel Rachel Teitelbaum
teitelba@AECOM.YU.EDU

To an aqueous suspension of latex beads add a few microliters of Nile Red (e.g. molecular Probes cat #N-1142) stock solution, which is about 5mg/ml in DMSO. I'm sure other hydrophobic dyes can be used as well, such as the Di I series. I didn't even need to wash free dye from the beads. Nile Red has little or no fluorescence except in a non-polar environment.

Richard Thrift
Richard_Thrift@DEPOTECH.COM

Hi again,
Thank you for your answers. But I'm affraid I do not ask my question properly. In fact I already have latex spheres (0.8 micron). I am using thoses spheres in experiments where surface properties are important. I do not want to buy new and unknown spheres and change the whole experiment. I just want to label the spheres after the experiment was done.

So, I am wondering if anyone here have experience in labelling latex unlabelled spheres with a fluorescent probe suitable for 488, 568 or 647 nm. The latex surface is modified with -COOH groups.

Antoine THILL
thill@ARBOIS.CEREGE.FR

The latex beads I related absorbing YOYO-1 and DAPI also have carboxyl modified surfaces.

Neal Nicklaus
nnicklaus@seq.sarnoff.com

We are also using fluorescently labelled latex beads from molecular probes (sold by Interchim s.a. Montlucon, France).

We used 10 um and 15 um beads with the following characteristics

10 um latex beads (cat. No. L-5032, lot no. 6942) Ex. 530 nm, Em. 560 nm
15 um latex beads (cat. No. L-5073, lot no. 6946) Ex. 580 nm, Em. 605 nm

The products are normally used for blood flow measurements, so they are supplied as sterile suspensions. They are also supplied at usable concentrations (1,055 g/cm3), so at normal optical magnifications (10 to 40 x) it is possible to find plenty of beads in the field of view. They are also highly fluorescent and seem quite stable to fading. Unfortunately, 1.) they are expensive, and 2.) they are just sold as 'red' or 'orange' fluorescent and we have been unable to find which dyes they contain. If anyone has this information, we would like to know (for interest).

We have also used latex beads of smaller size (0,7, 2,35 and 4 um) supplied by Chemunex (Maisons Alfort, France). The beads are labelled with fluorescein, coumarin-6, and fluorescein respectively. With these beads however we found that the concentrations in which they were supplied (7.10 x E4 beads/ml) were too small for our requirements, and we couldn't see many beads in one field of view.

Paul M. Baldwin & Daniel J. Gallant
e-mail gallant@nantes.inra.fr