BioSciences - Polysciences, Inc.

Additional Particles
Protein Coupling Troubleshooting
Microspheres & Particles
Below are some solutions for protein coupling troubleshooting. If you do not see a solution to the problem you are experiencing, please
email us at: info@polysciences.com
Problem Solution
Clumping prior to use
Clumping after procedure
• Carbodiimide addition causes clumping
• Glutaraldehyde addition causes clumping
• Protein addition causes clumping
• Washing causes clumping
Low binding
Variable coating
Coating, but no reaction
Centrifuge not practical
Nonspecific adsorption
Small proteins bound, but not reactive
Long-term storage leaches protein
Careful sonication
Isolate which step causes clumping
Add slowly, agitate beads, decrease bead concentration
Add slowly, agitate beads, decrease bead concentration; add an excess
of glutaraldehyde to avoid chemical crosslinking of particles; clumping
will typically resolve by the conclusion of the protein coupling
Increase protein concentration
Add surfactant or reduce washing steps
Move pH closer to protein isoelectric point
Use pure water - no contaminants; use fresh reagents
Optimize pH away from isoelectric point
Use membrane filtration, dialysis, or spin fibers for small particles
Use an alternative for BSA (glycine, casein)
Use a crosslinking agent to extend coupling away from
the surface of the bead
Try covalent attachment or lyophilize final product
Special Properties
Many applications in the life sciences demand added properties, such as fluorescence or a visible color, or iron oxide inclusions for
magnetic separations. Polymer spheres (and some polymer-based magnetic spheres) are often internally dyed via organic solvent swelling
and many standard products are available. Dye concentrations can be adjusted to produce beads with different intensities to meet special
needs, such as QuantumPlex for multiplexed flow cytometric assays or our Dragon Green or Flash Red Intensity Standards, which support
imaging applications and associated instrument QC. Many surface- or internally-labeled fluorescent beads are also available as specialized
flow cytometry standards.
Various types of superparamagnetic microparticles are available as well – with different matrices, magnetite content, surface groups, etc.
For new assays or applications, magnetic beads should be evaluated with application demands in mind.
The following tables provide product suggestions for common microsphere applications. These are offered as general guidelines only.
Further literature research and screening experiments may be appropriate.
For more information please call (800) 523-2575 or visit: polysciences.com 305