I have been recently going through the literature involving poly lipoic acid based bioadhesive gels and have been trying to understand the mechanism behind the formation of these gels and how they are able to adhere to tissues.
But Why Poly lipoic acid?
Wet adhesion research started with the study of natural adhesives found in nature, such as those used by mussles where the adhesive proteins (MFPs) are secreted to form a strong bond with the substrate. The musself foot proteins (MFPs) contain catechol groups from DOPA that help them to stick to surfaces really well even under water. So people started grafting catechol onto polymers too mimic that.
After the field grew, researchers began to explore the use of poly lipoic acid for its unique properties and potential applications in bioadhesive systems.
Lipoic acid ring opens on its own without any external need of catalyst or a initiator into a disulfide backbone polymer. That backbone is dynamic and allows for self healing and even depolymerization back too monomer.
The Adhesion Mechanism
In simple terms: the long hydrophobic alkyl chain pushes the water off the tissue surface and clears the way for the adhesive interactions to occur. The terminal COOH (and the disulfide backbone) interacts with tissue surface by covalent and non covalent interactions.