Data sheets | SPR Sensor chips

Azide–modified sensor chips

XanTec’s AZ sensor chips are coated with a bioinert polycarboxylate matrix (CMD or HC), pre-functionalized with low-molecular-weight azido groups grafted onto a hydrophilic adhesion promoter on a gold support. Ligands containing a compatible Click partner—such as dibenzocyclooctyne (DBCO)—can be covalently attached in a fast and selective manner via strain-promoted azide-alkyne cycloaddition (Click reaction).

Unlike classical EDC/NHS chemistry, DBCO/azide coupling is not time-critical; both reaction partners remain stable for weeks across pH 4—10. Their high selectivity minimizes side reactions and eliminates the need for quenching steps¹. Consequently, immobilization via Click coupling is reliable, convenient, and flexible. Owing to rapid reaction kinetics, coupling under physiological conditions is feasible, although maximum immobilization densities may be somewhat lower; thus, electrostatic preconcentration remains advantageous for achieving high ligand loading.

The AZ sensor chip portfolio spans electrostatic immobilization capacities from approximately 6000 μRIU (AZD50L) to 40,000 μRIU (AZHC1500M), covering analytes from large viruses to small organic fragments. The surface-bound azido groups are highly hydrophilic and possess a strong dipole moment, further enhancing the overall bioinertness of the coating.

Key features:

Versatile ligand coupling: Highly efficient and selective Click reaction enables covalent attachment of DBCO-functionalized ligands. Unlike classic amine coupling, ligand density can be iteratively increased after initial coupling, allowing fast optimization of immobilization levels and efficient sensor chip use.
Superior efficiency: The high efficiency of the Click reaction permits ligand immobilization even under physiological conditions.
DBCO functionalization: Ligands can be conveniently DBCO-modified using standard labeling protocols similar to biotinylation; site-specific conjugation via sortase-mediated ligation is also supported.
Wide immobilization range: From several thousand to ~40,000 μRIU, suitable for analytes from whole cells and viruses to fragments < 300 Da.
Bioinert nanoarchitecture: Combining a hydrophilic adhesion promoter, hydrated polycarboxylate matrix (CMD or HC), and surface azido groups minimizes nonspecific binding.
Application versatility: Suitable for kinetic, equilibrium, and concentration analyses, as well as diverse screening applications in drug discovery.

Schematic illustration of a 3D AZHC sensor chip. Short purple lines and red dots represent azido groups and negatively charged carboxyl groups distributed along the green polymer chains. The decaying red gradient represents the evanescent field. The magnified view shows a DBCO-modified antibody covalently immobilized via Click chemistry to azido functionalities.²

Product code³	AZD200M	AZHC30M	AZHC200M	AZHC1500M
Base coating	3D, 200 nm bioinert CM-dextran (medium density)	3D, 30 nm bioinert polycarboxylate (medium density)	3D, 200 nm bioinert polycarboxylate (medium density)	3D, 1500 nm bioinert polycarboxylate (medium density)
Covalent immobilization capacity [µRIU]⁴	≈ 13,000 (30,000)	≈ 10,000 (18,000)	≈ 13,000 (26,000)	≈ 20,000 (40,000)
Recommended ligands	proteins peptides nucleic acids carbohydrates
Recommended analytes	proteins peptides nucleic acids	proteins peptides nucleic acids small molecules carbohydrates	peptides nucleic acids small molecules carbohydrates	small molecules fragments nucleic acids carbohydrates
Intended purpose	immobilization of DBCO-functionalized ligands kinetics of small to large analytes equilibrium analysis concentration analysis immobilization of secondary antibodies and capture proteins	immobilization of DBCO-functionalized ligands kinetic analysis of small to large analytes especially suitable for weak binders with fast association and dissociation rates Suitable for assays requiring very low diffusion limitation immobilization of secondary antibodies and capture proteins	immobilization of DBCO-functionalized ligands kinetics of small and medium analytes equilibrium analysis concentration measurements immobilization of secondary antibodies and capture proteins	immobilization of DBCO-functionalized ligands kinetics of small analytes fragment-based drug discovery affinity and concentration analyses immobilization of capture proteins

¹ This is valid only when the analyte lacks its own Click-reactive functionality; otherwise, unintended covalent attachment may occur.

² All illustrations are schematic representations and are not drawn to scale; dimensions, densities, and spatial relationships do not reflect actual physical or chemical proportions.

³ Table includes a selection from XanTec’s full AZ sensor chip portfolio.

⁴ Covalent immobilization capacity was assessed by injecting 100 µg/mL DBCO-modified streptavidin in 5 mM sodium acetate buffer (pH 5.0), with 1 µRIU corresponding approximately to 1 RU. Electrostatic preconcentration capacity is shown in brackets.

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Azide–modified sensor chips