Silk fibroin is a naturally occurring biopolymer obtained by processing the cocoons of the domesticated silkworm Bombyx mori. Fibroin is a high molecular weight protein with charged hydrophilic terminal regions that endcap a blocky core, which consists of hydrophobic blocks containing the repeating amino acid sequence GAGAGS. The repetitive sequences can be triggered to organize into beta sheets to physically crosslink the protein, rendering it insoluble in water until reprocessed while imparting impressive mechanical properties. Fibroin is biocompatible and biodegradable, the rate of which is tunable by processing, and previous work in our lab has modified fibroin with various functional groups, including carboxylic acid. Taking inspiration from mussels that produce proteins rich in L-3,4-dihydroxyphenylalanine (DOPA) to adhere to a variety of organic and inorganic surfaces, this work focuses on fibroin functionalization with catechol groups. Conjugation of DOPA to various polymers, including poly(ethylene glycol) derivatives, was pioneered by Messersmith and colleagues, who have also studied adhesive and rheological properties. Our work adds to this knowledge by developing a new protein-based catechol conjugate. Fibroin was selected for its high molecular weight, tunable mechanical and degradation properties, wide availability, and aqueous processability. Considering fibroin's hydrophobic regions, these conjugates offer the potential for lower degrees of aqueous swelling and for higher strength (through the formation of beta sheets) than other water soluble catechol polymers, however this hydrophobicity must be balanced for aqueous processing of the final catechol-functionalized product. A series of fibroin polymers with varying amounts of hydrophilic side chains was synthesized and subsequently conjugated with catechol groups. Using a variety of characterization methods, we have determined that both the hydrophilic groups and catechols were successfully conjugated. Here, we discuss the synthesis and characterization of these new materials, which we envision to have applicability as biocompatible adhesives and sealants.

Structure and properties of catechol-functionalized silk fibroin

246th National Meeting (2013)

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