Comparative in Vitro Study on Anti-inflammatory Activity of Covalent Versus Layer-by-Layer-Bound Heparin and Hyaluronan Including Signal Transduction Through Transcription Factor NF-κB

Chronic inflammation and subsequent fibrotic encapsulation are the major factors that can hamper the function of biomaterials following implantation. Our work aimed to develop novel anti-inflammatory coatings to enhance biocompatibility of the biomaterials, but also to unravel the mechanism of their anti-inflammatory activity for guiding the design of more biocompatible materials. Here, we present two methods for immobilization of glycosaminoglycans (GAGs), namely hyaluronan (HA) and heparin (Hep) on model substrates either through chemical bonding of a GAG monolayer or through physical adsorption via the layer-by-layer (LBL) technique as GAG-chitosan (Chi) multilayers. We then show a comparative study of the covalent- vs. LBL-bound GAGs on physical properties, anti-inflammatory effects and the potential anti-inflammatory mechanism. It was found that both covalent- and LBL-bound GAG coatings can generate great anti-inflammatory effects regarding cellular responses of THP-1 macrophages. A higher inflammation-inhibiting potential of the LBL system was observed compared to covalent system with Hep-Chi multilayer showing the highest inhibitory activity. Furthermore, the mechanism investigations revealed that the anti-inflammatory activities of the GAG-immobilized coatings are not only related to increased hydrophilicity, but also caused by their active involvement in signal transduction on the NF-κB pathway at macrophage cellular level during inflammation.