Polylysine–modified sensor chips (PLY)
XanTec’s Polylysine (PLY) sensor chip is based on a 3D poly-L-lysine hydrogel matrix grafted onto a hydrophilic adhesion promoter on a gold support. In contrast to anionic carboxymethyl-dextran (CMD) or linear polycarboxylate (HC) coatings, the PLY matrix is strongly polycationic and therefore exhibits distinct physicochemical properties.
PLY surfaces are permanently positively charged and support electrostatic preconcentration of anionic ligands. Despite their polycationic nature, nonspecific interactions in physiological buffers are typically moderate. Because the surface lacks carboxyl groups, standard EDC/NHS activation followed by amine coupling is not applicable. Covalent immobilization must rely on alternative chemistries, such as coupling of NHS-preactivated anionic ligands (e.g., COOH-modified oligonucleotides). Even under physiological conditions, electrostatic interactions with polyanionic species may occur. For these reasons, PLY sensor chips are not typically the first choice for routine SPR-based kinetic or affinity measurements.
Nevertheless, the PLY matrix provides a useful bioinert polycationic reference coating for evaluating nonspecific interactions and benchmarking newly developed biomedical or antifouling surface chemistries.
Key features:
- Immobilization of anionic ligands: The polycationic matrix supports preconcentration and immobilization of NHS-activated anionic ligands such as DNA oligonucleotides.
- Reference surface: Provides a relatively bioinert polycationic hydrogel suitable for assessing nonspecific binding and benchmarking novel biomedical coating materials.
| Product code | PLY |
|---|---|
| Base coating | 3D, medium-length bioinert polylysine (medium density) |
| Electrostatic preconcentration capacity [µRIU]2 | ≈ 40,000 |
| Recommended ligands | NHS-preactivated acidic ligands |
| Recommended analytes | — |
| Intended purpose |
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1 All illustrations are schematic representations and are not drawn to scale; dimensions, densities, and spatial relationships do not reflect actual physical or chemical proportions.
2 Preconcentration capacity determined by injecting 100 µg/mL bovine serum albumin (BSA) in 5 mM sodium acetate pH 5.0, with 1 µRIU corresponding to ≈ 1 RU.