These are synonyms that we use interchangeably. We only offer round or spherical material and no other shapes. We sometimes classify or name our particles as spheres or beads, and depending upon size, we may describe them as microparticles or nanoparticles. They may also be described as ‘events’ when describing the number of beads per time interval read by an instrument, such as 100 events per second or 10,000 events per run. Otherwise, beads can be described as spheres or particles. These terms are common in the community and literature.

Most of our particles are polystyrene in nature. Some select beads are silica, PMMA, or colloidal gold nanoparticles. We also offer PS and silica beads with a magnetic nature, using magnetite or chromium dioxide.

The density of polystyrene is 1.05g/mL, silica is ~1.95 g/mL, PMMA is 1.18 g/mL, gold is ~19 g/mL, chromium dioxide is 4.89 g/mL, and magnetite is 5.24 g/mL. For our magnetic polystyrene particles, we dry mass and then burn the particles at ~1000C and mass the remaining to determine the %magnetite or chromium dioxide content and utilize those ratios to determine the density of magnetic particles. On the very high end, our magnetic polystyrene particles’ density can be up to ~2.6 g/mL, but most often, they are around 1.1-1.8 g/mL.

Polystyrene is polymerized linearly by initiating liquid styrene with potassium persulfate or benzoyl peroxide. Divinyl benzene is added to the polymerization process to crosslink polystyrene chains perpendicular to the main chains. Particles made in this manner are named ‘crosslinked.’ This allows for a more stable particle in some solvents like THF, DMSO, or acetonitrile, for example, in the case of polypeptide synthesis, among many other protocols. This crosslinking method can be very useful for increased sphericity of larger particles, say over 10-15 um. Our crosslinked catalog numbers are denoted with an ‘X,’ for example, ‘PP’ vs. ‘PPX’ or ‘CM’ vs. ‘CMX’ as the prefix in the catalog number.

Polystyrene, PMMA, and Silica are evaluated as non-toxic. This polymer is used in many industries and is often in direct contact with humans and other animals. A body of literature utilizes polystyrene and similar particles in various cell and model animal studies. We offer our particles as Research Use Only products. Therefore, they are not to be ingested or inhaled by end users. Buffers also contain salts or surfactants that end users should not ingest or inhale. If reagents come into contact with your eyes, flush the contact area immediately.

No. We do not offer porous particles.

The refractive index of polystyrene is ~1.6, silica ~1.45, and PMMA ~1.5.

We do not test the surface charge of the beads. The surface charge of the beads is typically reported as net negative. We polymerize the polystyrene particles with styrene using potassium persulfate or benzoyl peroxide initiators, resulting in some partial or full negative charge groups within the polymer itself. Both amine and carboxyl functionalized beads differ, but both are often reported to us as net negative. Typically, the data is reported as electrophoretic mobility or zeta potential, which is buffer-dependent. Feel free to contact our support team, and we can discuss this further if desired.

Most typically, uncoated particles and particles that are only functionalized can be stored at ambient room temperature and have an expiry of 3 years after receipt and one year after opening. It is recommended to store particles once opened at 2-8oC. Coated particles need to be stored at 2-8oC and will have an expiry of 1 year after receipt. The exceptions are those uncoated beads that contain BSA in solution. They will need to be refrigerated and have a shorter expiry. The storage conditions can be found on the Technical Data Sheets for the product, and expiry information can be found on Certificates of Analysis, each of which is Lot dependent. Fluorescent particles, coated or dyed, will need to be stored PROTECTED FROM LIGHT. They are supplied in foil pouches, amber bottles, or both. Do not freeze particles or undergo freeze-thaw cycles.

Polystyrene particles are very stable. They melt at ~240oC and may become embrittled at above ~105oC. They can be used for PCR, cycling ~96oC readily. For most common reactions around 37oC-70oC they are not compromised. They are stable in aqueous buffers. They can be stored and washed repeatedly in very mild organic solvents like ethanol or isopropyl alcohol. They will dissolve in very polar organic solvents like chloroform, dichloromethane, or acetone. Silica is stable in those solvents. Crosslinked polystyrene is more stable and able to be utilized in washes with, say, THF, DMSO, or acetonitrile for specific protocols – but crosslinked polystyrene will still dissolve in the organic solvents above, like acetone. We can consult on these more specific procedures. The PS beads are very hearty and not prone to breaking, tearing, or shredding unless under conditions of previous embrittlement or multiple freeze-thaw cycles. We have not tested the beads under prolonged ultracentrifugation for particles larger than 0.08 um. 40,000 xG or faster speeds may cause unforeseen consequences.

All particles arrive in solution with ~0.02% Sodium Azide as an anti-biological preservative. Uncoated particles arrive in MiliQ water. Many AccuCount or Rainbow beads also contain a bit of surfactant, such as 0.02-0.05% NP-40 substitute, others of which have ~0.05% BSA. Coated particles are delivered in 1x PBS, phosphate buffered saline, or isotonic buffered saline (IBS), a phosphate buffer with sodium and potassium chloride salt. You can find the buffer of each catalog number on the TDS provided with the particles in hardcopy or upon request of our team.

Begin by rolling out or vortexing beads to increase singlets. If the beads are not protein-coated, brief, repeated bath sonication can be applied. The best way to increase singlets is often by using surfactants. 0.05-0.1% BSA can be added or ~0.01-0.02% non-ionic surfactant such as NP-40 substitute, Tween20, Ecosurf E9, Triton X-100.

Below is a table of common centrifuge settings. If you are using particles smaller than 0.08 um, please contact us, and we can supply some other techniques.

One should begin by rolling out or vortexing beads to resuspend particles. If the beads are not protein coated, brief, repeated bath sonication can be applied if desired. If desired, further monodispersity can be achieved by using surfactants. 0.05-0.1% BSA can be added or ~0.01-0.02% non-ionic surfactant such as NP-40 substitute, Tween20, Ecosurf E9, Triton X-100.

Washing beads involves setting, removing supernatant, adding a new buffer, and resuspending them. Settling can be either by gravity or other techniques, often magnetic or centrifugation. Then, removal of the supernatant, most often by decanting or pipetting. Then MiliQ, DI water, PBS, or other preferred buffer or sheath fluid is added, and the particles are resuspended by vortexing or rotation, among other methods. Often, two washes in succession are preferable.

The beads are not provided sterile. Spherotech particles are in a solvent with 0.02% sodium azide as an anti-biological. If sterility is needed, the particles can be washed once with 70% alcohol or 3% hydrogen peroxide by centrifugation and resuspension as follows:

1. Add 2-3 drops (or desired volume) of particles to 1 mL of dilution buffer in a 1.5 mL microfuge tube.
2. Centrifuge, remove the supernatant, and resuspend the particles in 1 mL of 70 % alcohol or 3% hydrogen peroxide by vortexing.
3. After 5 mins, centrifuge, remove the supernatant, and resuspend in 1 mL of sterile dilution buffer.
4. Vortex, centrifuge, remove the supernatant and resuspend in 1 ml of sterile dilution buffer.

You can lyophilize or nebulize particles using appropriate techniques and safety equipment. Drying beads by heat or evaporation will likely cause irreversible aggregation and is not recommended. We cannot guarantee the quality of the particles once dried or the ability to reconstitute them into solution.

Ferromagnetic particles are made utilizing chromium dioxide and demonstrate a permanent dipole moment. The only way to release the magnetic dipole would be to vigorously vortex or sonicate the particles. Paramagnetic particles have a temporary dipole moment and are more commonly utilized. When a field is applied, they will align, but when the field is released, they too will release and will resuspend readily. Paramagnetic particles are made with magnetite.

Rainbow beads are polystyrene particles that have multiple fluorescent dyes encapsulated within such that they are excitable across and below the visible spectra and emit therein. Ultra Rainbow beads have all of the dyes within them that Rainbow beads contain, as well as an extra UV and Far Red dyes to reach further into that excitation range. Each and both can be used as alignment particles across all flow cytometer channels, and the multipeak kits of each may be used for calibration and extrapolation.

Our standard fluorescent particles, the prefix ‘FP,’ are particles with organic soluble dyes internally encapsulated within. They are as stable as other polystyrene beads. They should be protected from light, as they will dim with long, continuous light exposure, but can be stored at ambient or room temperature. The primary exception is the EasyComp compensation particles, with the prefix ECFP. These are particles we offer that are surface-coated with common fluorophores such as FITC, PE, APC, etc. They should be stored at 2-8°C and protected from light.

Paramagnetic particles are made from polymerizing polymer particles and then polymerizing a layer of magnetite to the surface. A smooth particle is made in the same way but with an additional layer of polymer polymerized over the magnetic surface. Crosslinked magnetic particles vary in the original polymer particle. Polystyrene is polymerized linearly by initiating liquid styrene with potassium persulfate or benzoyl peroxide. Divinyl benzene is added to the polymerization process to crosslink polystyrene chains perpendicular to the main chains. Particles made in this manner are named ‘crosslinked’. These crosslinked beads then have magnetite polymerized to the surface as the traditional paramagnetic particles. We do also offer superparamagnetic or high iron nanoparticles, both polystyrene and silica. These have magnetite cores which are surrounded by polymer or silica.

The three main methods are passive coating, covalent coupling, and carrier protein. You can begin with a plain particle and coat the particles with your protein of interest by rotation at ambient or ~37°C in a buffer at near physiological pH. You can covalently couple to functionalized particles. The most common routes are EDAC chemistry, EDC or EDC/NHS protocols in MES buffers, or copper-free Click Chemistry. The third coating method is by carrier protein. The most common method of this type is utilizing streptavidin/avidin/neutravidin and biotin binding. You can get a biotinylated or avidin-modified protein of interest and our complimentary streptavidin/avidin/neutravidin or biotin-coated particles. For instance, if you have a biotinylated antibody, you can procure our streptavidin beads and incubate them together at ambient or ~37°C under rotation. This results in antibody-coated particles for your assay development or isolation goals. Please get in touch with support if you have follow-up questions or more specifics about an individual method generalized protocol.

The three main methods are passive coating, covalent coupling, and carrier protein. You can begin with a plain particle and coat the particles with your protein of interest by rotation at ambient or ~37°C in a buffer at near physiological pH. You can covalently couple to functionalized particles. The most common routes are EDAC chemistry, EDC or EDC/NHS protocols in MES buffers, or copper-free Click Chemistry. The third coating method is by carrier protein. The most common method of this type is utilizing streptavidin/avidin/neutravidin and biotin binding. You can get a biotinylated or avidin-modified protein of interest and our complimentary streptavidin/avidin/neutravidin or biotin-coated particles. For instance, if you have a biotinylated antibody, you can procure our streptavidin beads and incubate them together at ambient or ~37°C under rotation. This results in antibody-coated particles for your assay development or isolation goals. Please contact support if you have follow-up questions or more specifics about an individual method generalized protocol.