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Products | SPR Sensor chips | Hydrogels


With a sufficiently sensitive detector, 2D surfaces are a good basis for many biomolecular interaction studies; however, numerous applications require a ligand density greater than one monolayer, either because the analyte is small (<2 kDa), or the optics are not sufficiently sensitive. In these cases, use of hydrogels can be advantageous.  A structurally flexible and strongly hydrated polymer brush is useful to shield the substrate and suppress non-specific interactions. Enhanced accessibility of the ligand’s binding sites and its increased mobility when immobilized through molecular spacers are further advantages of using hydrogels. Hydrogels can also help to solubilize hydrophobic ligands that would otherwise tend to form insoluble aggregates on the chip surface, and protect sensitive ligands against denaturation, especially in the dry state.

These advantages led to the development of surface-grafted, typically brush-structured, 3D hydrogels with thicknesses ranging from <10 nm to >1000 nm. These structures provide an increased density of attachment sites on the chip and, more importantly, use a higher volume fraction of the evanescent field for the specific interaction compared with 2D coatings. A welcome side effect of this approach is that the absolute influence of nonspecific factors such as bulk shifts decreases proportionally with increasing occupation of the evanescent field volume by the ligand–analyte pair.

In principle, surface-grafted hydrogels can be made from any water-soluble polymer; however, in practice, polycarboxylates, polyethers and polyols are preferred as they show significantly lower backgrounds than, for example, polyamines. In the early 1990s, the first commercial sensor chip coatings were derived from well-characterized, dextran-based solid phases for affinity chromatography. The most popular matrix material today is carboxymethylated dextran. Other carboxylated polysaccharides such as alginate, pectin, carboxymethylcellulose and hyaluronic acid can be used as well, but are less common. Because these polymers are of natural origin, their structures are often irregular; i.e., they can be more or less branched, or form hyperstructures such as helices or suprafibers. Furthermore, especially in the hydrated state, carbohydrates are relatively bulky molecules, occupying a considerable volume of the evanescent field that is then not available for the immobilization of ligand, and hindering the free diffusion of analyte.

For these and other reasons, efforts have been made to substitute polysaccharides with better defined synthetic polycarboxylates or zwitterionic polymers with lower background and smaller molecular footprints. In addition to reducing steric issues, coatings containing no hydroxyl groups have the advantage that they cannot form ester crosslinks upon EDC/NHS activation, a common side reaction occurring with carboxymethylated carbohydrates.

Hydrogel surfaces

3D immobilization matrices allow multilayer ligand immobilization which leads to significant signal amplification. They are employed for qualitative screening, concentration determinations and detection and kinetic analysis of low molecular weight compounds. As a rule of thumb, the smaller the analyte is, the thicker and denser the hydrogel structure should be.

The new hydrogel coatings of the HC family are currently available in four different thickness / porosity combinations: HC30M, HC200M, HC1000M and HC1500M. The HC type is based on a linear, synthetic polycarboxylate. Compared to the branched dextrans, it is better defined, shows a higher signal to noise ratio, has improved diffusion properties (better curve fits) and lower nonspecific interactions. Even more inert is the new HLC version which is available in the same thickness density combinations.

Hydrogel surfaces
Product codeChipsProduct description
AL1Alginate hydrogel. Approx. 50 nm
AZD xx1Azide derivatized carboxymethyldextran hydrogel.
AZD xx-55For click coupling. 50L, 200M
AZHC x1Azide derivatized linear polycarboxylate hydrogel.
AZHC x-55For click coupling. 30M, 200M, 1500M
BD xx1Biotin derivatized carboxymethyldextran hydrogel.
BD xx-5550L, 200M, 500L, 700M
BHC x1Biotin derivatized linear polycarboxylate hydrogel.
BHC x-5530M, 200M, 1500M
C x1Linear polycarboxylate hydrogel, high charge density.
C x-5530M, 80M, 150D
CMD xx1Carboxymethyldextran hydrogel.
CMD xx-5550L, 50M, 200L, 200M, 500L, 500M, 700L, 700M
CMPEG1Carboxymethylpolyethyleneglycol, 4 kDa.
D x1Dextran hydrogel.
D x-5550M, 200M, 500M, 700M
DCD xx1DBCO derivatized carboxymethyldextran hydrogel, medium density.
DCD xx-55For Click Coupling. 50L, 200M
HC x1Polycarboxylate hydrogel, medium charge density.
HC x-55Protein immobilization, standard. 30M, 200M, 1000M, 1500M
HEP1Heparin. Approx. 50 nm hydrogel.
HLC1Polycarboxylate hydrogel, low charge density.
HLC-55Extremely low level of non-specific interactions. 30M, 200M, 1000M, 1500M
HOD x 1Chloroalkane derivatized carboxymethyldextran hyrogel.
HOD x-55For coupling of HaloTag fusion proteins.200M
HOHC x1Chloroalkane derivatized linear polycarboxylate hydrogel, medium density
HOHC x-55For coupling of HaloTag fusion proteins.200M
LD1Carboxymethyldextran hydrogel, partially alkyl derivatized.
LD-55For immobilization of liposomes and vesicles.
NAHLC xx1Neutravidin derivatized linear polycarboxylate hydrogel, low charge density.
NAHLC xx-5530M, 200M, 1500M
NID xx1NTA derivatized carboxymethyldextran hydrogel.
NID xx-5550L, 200M, 500L, 700M
NIHC x1NTA derivatized linear polycarboxylate hydrogel, medium charge density.
NIHC x-5530M, 200M, 1000M, 1500M
PAD xx1Protein A derivatized carboxymethyldextran hydrogel.
PAD xx-5550L, 200L
PAHC x1Protein A derivatized linear polycarboxylate hydrogel.
PAHC x-5530M, 200M
PAGD xx1Protein A/G derivatized carboxymethyldextran hydrogel.
PAGD xx-5550L, 200L
PAGHC x1Protein A/G derivatized linear polycarboxylate hydrogel.
PAGHC x-5530M, 200M
PEG1Polyethyleneglycol, 4 kDa.
RGD x1Oligonucleotide derivatized carboxymethlydextran
RGD x-55For reversible immobilization of RG-oligo conjugates. 200M
SAD xx1Streptavidin derivatized carboxymethyldextran hydrogel.
SAD xx-5550L, 50M, 200L, 200M, 700L
SAHC x1Streptavidin derivatized linear polycarboxylate hydrogel.
SAHC x-5530M, 200M, 1500M
SPYD x 1Spycatcher derivatized carboxymethyldextran hydrogel, medium density
SPYD x-5 5For immobilization of SpyTag fusion proteins. 200M
SPYHC x1Spycatcher derivatized linear polycarboxylate hydrogel, medium density
SPYHC x-5 5For immobilization of SpyTag fusion proteins. 200M
STD x1Strep-Tactin XT derivatized carboxymethyldextran hydrogel.
STD x-55For reversible immobilization of Twin-Strep-tagged ligands. 200L
STHC x1Strep-Tactin XT derivatized linear polycarboxylate hydrogel.
STHC x-55For reversible immobilization of Twin-Strep-tagged ligands. 200M
UVD xx1UV photocrosslinker derivatized carboxymethyldextran hydrogel, λ: 365 nm (UV-C)
UVD xx-55200M
UVHC x1UV photocrosslinker derivatized polycarboxylate hydrogel, λ: 365 nm (UV-C)
UVHC x-55200M
ZC x1Zwitterionic polycarboxylate hydrogel, cationic after NHS activation.
ZC x-55Immobilization of anionic ligands. 80M, 150D
ZCC x1Zwitterionic polycarboxylate hydrogel, cationic, non-activated.
ZCC x-55Preconcentration scouting of anionic ligands. 150D

The above mentioned SPR substrates are mainly intended for biomolecular interaction analysis, but may also be used as intermediate platforms for further modifications. The 2D and 3D coatings are covalently coupled to a protective interlayer and resist non-oxidative aqueous solutions from pH 1 - 13 as well as most organic solvents.

Alternative formats and custom coatings available upon request.