Carboxylated Polystyrene Latex Beads (8.0–8.9 µm) – Catalog #B2025466

Carboxylated polystyrene latex beads (Catalog #B2025466) are supplied as 5 mL of a uniform suspension of polymer spheres, 8.0 to 8.9 micrometers in diameter. Each particle carries carboxyl (–COOH) groups on its surface that are ionized at physiological pH, creating a stable negative charge. This carboxylation enables straightforward chemical coupling of proteins, peptides, antibodies, and other ligands via carbodiimide or other standard chemistries. The beads' larger micrometer size makes them easy to handle in routine laboratory workflows and suitable for applications where optical resolution or bead recovery is important.

Scientific Overview

Polystyrene has been the material of choice for bead-based diagnostics and immunoassays for decades because of its chemical stability, uniform synthesis at defined sizes, straightforward chemical modification, and reliable performance in automated and manual laboratory workflows. Carboxylation via copolymerization with methacrylic acid or post-synthetic treatment adds ionizable surface groups that are negatively charged at physiological pH. This negative charge stabilizes the suspension against aggregation (through electrostatic repulsion) and provides a chemical handle for ligand attachment via carbodiimide-mediated coupling, streptavidin–biotin interactions, or other conjugation strategies.

At 8–9 µm, these beads are at the larger end of the practical range for immunoassays and flow cytometry. At this size, beads are easy to see under a light microscope, can be recovered magnetically if paramagnetic material is incorporated, and provide sufficient surface area for high-affinity antibody or protein coating. The size is ideal for applications where the operator needs clear visual feedback, such as manual bead-based assays, and for flow-cytometry experiments where larger particles are preferred for optical resolution or gating.

Key applications include:

• Immunoassays with high optical readout (bead-based ELISA, sandwich assays)
• Flow cytometry and fluorescence-activated cell sorting (FACS) with antibody-coated beads
• Manual bead-based assays where visual handling is important
• Protein capture and affinity purification
• Bead-based diagnostic platforms and point-of-care assays

Usage & Handling Guidance

Store the suspension at 2–8°C in the original container. Invert several times before use to ensure even distribution. For protein coating, dilute the beads into ultrapure water or phosphate-buffered saline and activate with carbodiimide (e.g., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, or EDAC) and N-hydroxysuccinimide (NHS) to form reactive esters on the carboxyl groups, then incubate with the target protein or antibody. Specific coupling protocols depend on the protein's pI, concentration, and desired coating density; optimization may be required for your application.

• Activation: Use EDAC/NHS chemistry to convert carboxyl groups to reactive N-hydroxysuccinimide esters for amine-coupling. Follow published protocols for your target biomolecule.
• Protein concentration: For antibody coating, test a range of antibody concentrations (typically 1–10 µg/mL) and incubation times to find the optimal density for your assay.
• Washing and blocking: After coupling, wash beads thoroughly and block with BSA or non-fat milk to reduce non-specific binding.
• Visual inspection: The larger bead size allows visual inspection for aggregation; beads should appear as a uniform suspension when resuspended.

What You Get

• 5 mL of carboxylated polystyrene latex bead suspension
• Uniform 8.0–8.9 µm particles with well-defined negative surface charge
• A convenient starting material for flow cytometry, immunoassay development, and bead-based diagnostic platforms
• For research use only (RUO)

Why Researchers Choose It

• Large, uniform size for easy visual handling and microscopy
• Straightforward surface chemistry for protein and antibody immobilization
• Excellent for flow cytometry and optical detection methods
• Proven track record in bead-based immunoassays and diagnostics
• Stable aqueous suspension ready to use

Frequently Asked Questions (FAQ)

• How do I couple antibodies to the beads?
  Activate the carboxyl groups using EDAC/NHS chemistry to form reactive succinimide esters, then incubate with your antibody of interest. The amine groups on your antibody will form amide bonds with the activated carboxyls. For optimal coating, test a range of antibody concentrations and incubation times specific to your antibody.
• Are these beads suitable for flow cytometry?
  Yes, excellent. The 8–9 µm size is ideal for flow cytometry and allows for easy gating and optical resolution. Fluorescently labeled beads are commonly used as controls and in bead-based assays.
• Can I see the beads under a microscope?
  Yes. At 8–9 µm, the beads are easily visible under a light microscope (40x or 100x objective), which makes manual assays and visual inspection straightforward.
• What is the binding capacity?
  Binding capacity depends on the target protein's size and the desired coating density. Test with your specific antibody or protein to determine optimal coverage for your assay.
• How should I store coated beads?
  Store coated beads at 2–8°C in storage buffer (typically PBS with 0.02% sodium azide as a preservative). Do not freeze unless specifically indicated.
• Can I get a TDS or COA?
  Yes. Request a quote or contact us and we will provide available lot documentation.

References

• Gupta SK, Guesdon JL, Avrameas S, Talwar GP. Sandwich enzyme immunoassay of human chorionic gonadotropin using polystyrene beads as solid support. Ann Inst Pasteur Immunol (1985). 1985;136D(1):47-55.
• Hashida S, Ishikawa S, Nakamoto H, Tanaka S, Kojima M, Ishikawa E. Simple and more sensitive immune complex transfer enzyme immunoassay for antibody IgG to reverse transcriptase of HIV-1 using microplates, modified polystyrene solid phase and fluororeader. J Clin Lab Anal. 1996;10(5):294-301.
• Schoof E, John MR, Arndt B, Gao P, Theuer D, Sieg A, Schmidt-Gayk H. Solid phase competitive luminescence immunoassay for immunoglobulin A in faeces: development and clinical validation. Clin Chim Acta. 1997;261(1):1-17.