What are bioadhaesives

Mussels inspire the next generation of water-based wet adhesives. Mussel foot proteins (mfps) allow mussels to adhere to any surface and show remarkable properties, particularly caused by the amino acid derivative 3,4 dihydroxyphenylalanine (dopa). Since the influence of water is still a major challenge for adhesive applications and the production and cleaning of adhesive proteins requires a lot of time and money, easy access to biomimetic adhesives is of great interest. The present work investigates a novel mussel-inspired polymerization approach for the production of adhesive protein analogs from oligopeptides (unimers). The polymerization mechanism uses a reaction pathway that occurs in mussels and is based on the enzymatic oxidation of tyrosine to dopaquinone, which forms cysteinyldopa with free thiols from cysteine, thereby linking unimers and creating adhesive functionalities. Within a few minutes, high molecular weight polymers are created that demonstrate versatile adsorption and strong adhesion behavior. The protein analogs show significant multilayer adsorption on hydrophilic and hydrophobic surfaces and are resistant to rinsing steps with highly concentrated salt solutions. The observed adhesion energies are in the range of commercial mfp extracts and even exceed reported values ​​for isolated mfps. The thesis presents a simple synthesis of artificial mfp analogues that are able to mimic aspects of natural mfps and potentially contribute to the development of water-resistant universal adhesives. In order to improve the conditions for cost-effective, large-scale production, alternative synthetic routes for the enzyme-free production of mussel-inspired polymers based on the chemical oxidation of dopa-containing unimers are also being investigated.

 

Marine mussels provide inspiration for the next generation of water-based, wet adhesives. Mussel foot proteins (mfps) enable them to attach to any surface and exhibit remarkable properties, notably due to the amino acid derivative 3,4-dihydroxyphenylalanine (Dopa). Since the influence of water still constitutes a major challenge for gluing applications and large-scale production and purification of adhesive proteins is time-consuming and costly, an easy access route toward biomimetic adhesives is of high interest. This thesis investigates a novel mussel-inspired polymerization approach for the production of adhesive protein analogues from oligopeptides (unimers). The polymerization mechanism exploits a distinct reaction pathway, occurring in mussels and relies on enzyme-mediated oxidation of tyrosine to Dopaquinone in the unimers, which forms cysteinyldopa with free thiols from cysteine, thereby linking unimers and generating adhesive moieties. Within a few minutes high molecular weight polymers are obtained that show versatile adsorption and strong adhesion behavior. The protein analogues exhibit significant multilayer adsorption onto hydrophilic as well as hydrophobic surfaces and resist rinsing with highly saline solutions. Comparative adhesion studies on silica reveal adhesion energies that are in the same range as commercial mussel foot protein extracts and even exceed reported values ​​for isolated foot proteins that constitute the gluing interfaces. The approach offers facile access toward artificial mussel foot proteins that are capable of mimicking aspects of the natural ideal and potentially helps to develop next-generation universal water resistant glues. In order to further improve the conditions regarding cost-efficient and large-scale production in the future, alternative synthesis routes for the enzyme-free generation of mussel-inspired polymers based on chemical oxidation of Dopa containing unimers are additionally explored.