APTES mediated modular modification of regenerated silk fibroin in a water solution†
Silk fibroin (SF) is a natural polymer of increasing interest for applications ranging from tissue engineering to optoelectronics. Here, we report a new mild and facile strategy targeted on hydroxylic pendants of serine and tyrosine residues, to functionalize SF in water, based on the use of amino(propyl)triethoxysilane (APTES), a common silylating agent. APTES is exploited as a bifunctional linker to bind SF through the triethoxysilane α-ends and to simultaneously graft species of interest, even hydrophobic ones, by means of the end γ-amino groups. By using a fluorescent oligothiophene bearing amino reacting end groups (T3) we monitor the process simply through fluorescence detection and we demonstrate the value of the proposed method to achieve chemically modified SF materials. Moreover, we show that the new SF based biocomposite retains silk filmability and transparency but also shows T3 fluorescence and markedly enhanced mechanical robustness.