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Protein Compatible Hydrogel Nanofilms


 

Protein Compatible Hydrogel Nanofilms



Proteins use to denature if they interact with surfaces. The so-called unspecific interactions between proteins and surfaces are usually responsible for the denaturation.

1. 3D-Functionalization

With the hydrogels these interaction are extremely small. Proteins can be immobilized inside the hydrogel in a 3D manner which results in a high coupling density.
Scheme of a 3D-hydrogel with functional groups (yellow), ligands for protein immobilization (red) and proteins (pink).
Zoom Scheme of a 3D-hydrogel with functional groups (yellow), ligands for protein immobilization (red) and proteins (pink).

These hydrogels provide proteins with their natural environment which keeps them in their functional state. Thus, such gels can be used to study the function of the immobilized proteins or to exploit the function in a diagnostic device. The layers prepared from the hydrogels are thin to allow a rapid diffusion into the gel and out of it. The technique for the preparation of hydrogel films is very versatile. Many parameters and properties of the hydrogel can be adjusted to the needs of a specific application:

There is an almost unlimited range of substrate materials to be coated with the hydrogel. For the immobilization of proteins, a variety of techniques can be utilized as for example the classic biotin–streptavidin way, the click chemistry, or the EDC/ NHS technique.

The concentration of coupling groups can be adjusted to the requirements in a wide range. Hydrogels with a varying carboxylic acid group concentration, for example, are prepared by adding different amounts of alanine to the reaction solution. The concentration of COOH groups can be determined by XPS and by fluorescence labelling.
XPS (left) and fluorescence spectra (right) of a PEG gel with an increased concentration of carboxylic acid groups. XPS: increasing COOH component at 289.2 eV. fluorescence labelling: quenching at high concentration (alanine concentration: 1: 0; 2: 0.05 mmol/l; 3: 0.2 mmol/l; 4: 0.3 mmol/l).
Zoom XPS (left) and fluorescence spectra (right) of a PEG gel with an increased concentration of carboxylic acid groups. XPS: increasing COOH component at 289.2 eV. fluorescence labelling: quenching at high concentration (alanine concentration: 1: 0; 2: 0.05 mmol/l; 3: 0.2 mmol/l; 4: 0.3 mmol/l).

A hydrogel that can be used for biotin–streptavidin based conjugation has bioton coupled to the network. The biotin can be detected and determined using a streptavidin which is conjugated with fluorescence labelled biotin.
Fluorescence spectra of streptavidin-FITC after a specific interaction with hydrogel bound biotin (red) and a hydrogel without biotin (blue).
Zoom Fluorescence spectra of streptavidin-FITC after a specific interaction with hydrogel bound biotin (red) and a hydrogel without biotin (blue).

2. Stage of development

The technology developed at the Fraunhofer IAP allows the efficient production of surface bound hydrogel nanofilms. A patent application was filed. Requests of a specific application can incorporated to detail the preparation procedure. In a next step, the prototype equipment for the production can be designed. 3D-Hydrogels coupled to a polymer surface will provide new opportunities for medical diagnostics and biological research. Beside the application in biological sensors and diagnosis devices there are many more fields of application. One could think of investigating the interaction with biological cells or of preparing protein resistant surfaces.

Further information:
Fraunhofer_IAP_Nanohydrogelfilms.pdf