Poly(L-lysine hydrobromide) NEW

Poly(L-lysine hydrobromide) (PLL-HBr) is a synthetic, cationic polymer derived from the amino acid L-lysine. It's widely used in cell biology, biotechnology, and materials science, primarily as a surface coating to promote cell adhesion. Here's a detailed breakdown:

1. Chemical Structure

• Poly(L-lysine): A linear polymer where multiple L-lysine monomers are linked via peptide bonds (amide linkages).

• Hydrobromide Salt (HBr): The lysine side chains (amine groups, -NH₂) are protonated and paired with bromide ions (Br⁻). This makes the polymer water-soluble and strongly cationic (positively charged).

• General Formula: [-(CH₂)₄-NH₃⁺ Br⁻]- per lysine unit.

2. Key Properties

• Cationic Charge: At physiological pH, the amine groups are protonated, giving PLL a strong positive charge.

• Biocompatibility: Non-toxic at appropriate concentrations (though cytotoxic at high doses).

• Water Solubility: The HBr salt form ensures solubility in aqueous solutions.

• Molecular Weight Variability: Available in various MW ranges (e.g., 15–300 kDa). Higher MW = stronger adhesion but potential cytotoxicity.

3. Primary Applications

 A. Cell Culture & Tissue Engineering

• Cell Adhesion Promoter:

• Coats glass/plastic surfaces (e.g., culture dishes, coverslips, slides).

  Positively charged PLL binds negatively charged components of cell membranes (e.g., sialic acids, proteoglycans), enhancing attachment of anchorage-dependent cells (e.g., fibroblasts, neurons).

• Neuroscience: Critical for culturing primary neurons.

• Stem Cell Research: Improves adherence of delicate stem cells.

 B. Biomaterial & Diagnostic Coatings

• Microscopy Slides: Prevents tissue/cell detachment during staining/washing.

• Biosensors: Functionalizes surfaces for immobilizing DNA, proteins, or nanoparticles.

• Gene Delivery: Complexes with DNA (via charge interaction) for transfection (less common than polyethylenimine).

 C. Other Uses

• Electrostatic "Glue": Binds negatively charged molecules (e.g., DNA, RNA, heparin).

• Cryopreservation: Added to protect cells during freezing.

4. How to Use

• Typical Protocol:

• Dilute PLL-HBr in sterile water or buffer (e.g., 0.1 mg/mL).

  Coat surfaces (30 min–2 hrs, RT).

  Rinse thoroughly with water to remove excess/unbound PLL.

  Dry surfaces before seeding cells.

• Critical Note:

• Over-coating can cause cytotoxicity – optimize concentration/MW for your cell type.

  Always use sterile, endotoxin-free PLL for cell culture.

5. Safety & Handling

• Cytotoxicity: High concentrations or residual PLL can damage cells.

• Bromide Content: May interfere with bromide-sensitive assays (e.g., some halide detectors).

• Alternatives:

• Poly-D-lysine: Protease-resistant (longer-lasting coating).

  Natural polymers (e.g., laminin, collagen).

6. Key Differences from Poly-D-lysine

💡 In Summary

Poly(L-lysine hydrobromide) is a workhorse cationic polymer that makes surfaces "sticky" for cells and biomolecules. Its versatility in cell culture, diagnostics, and biomaterials stems from its strong positive charge and solubility. Always optimize its use to balance adhesion promotion and cytotoxicity!