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Study of Layer-by-Layer Assemblies of Chitosan and Heparin by Dual polarization interferometry (DPI) (CAT#: STEM-MB-0460-WXH)

Introduction

The layer-by-layer technique, LbL, has been extensively used during the past decade to create polymer films on both planar and colloidal surfaces. The LbL technique enables the formation of complex multilayer films relatively simply through the sequential adsorption of oppositely charged polyelectrolytes. In recent years, there has been growing interest in the use of multilayers consisting of natural polyelectrolytes such as polysaccharides, polypeptides, and proteins because of their abundance, low toxicity, and biocompatibility. Therefore, the multilayers are promising systems for industrial applications in the biomedical field, for example, for the controlled release of drugs, in enzyme immobilization at biosensor surfaces, and for antibacterial coatings on medical implants.
Multilayer films can be formed with natural polysaccharides chitosan (CH) and heparin (HEP). This combination is of interest because the two polysaccharides have antibacterial and antiadhesive properties, respectively, and are therefore promising coatings for medical implants. In a recent study, it was found that the antibacterial performance of CH/HEP multilayers could be enhanced further by including silver nanoparticles in the multilayers.




Principle

Dual polarization interferometry (DPI) is an analytical technique that allows the simultaneous determination of thickness, density, and mass of a biological layer on a sensing waveguide surface in real time. DPI focuses laser light into two waveguides. One of these functions as the "sensing" waveguide having an exposed surface while the second one functions to maintain a reference beam. A two-dimensional interference pattern is formed in the far field by combining the light passing through the two waveguides. The DPI technique rotates the polarization of the laser, to alternately excite two polarization modes of the waveguides. Measurement of the interferogram for both polarizations allows both the refractive index and the thickness of the adsorbed layer to be calculated. These measurements can be used to infer conformational information about the molecular interactions taking place, as the molecule size (from the layer thickness) and the fold density (from the RI) change.

Applications

Study of Layer-by-Layer Assemblies of Chitosan and Heparin.
Development of antibacterial coatings on medical implants.

Procedure

1. Setting of dual polarization interferometry
2. Preparing the DPI sensor chip
3. Immobilization of target on DPI biosensor
4. Reagent was injected to react
5. Quantitative analysis

Materials

• DPI biosensor
• DPI sensor chip
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