title: Structural study on methacrylamide-grafted Tussah silk fibroin fibres.
abstract: Tussah silk fibroin fibres were modified by grafting with methacrylamide (MAA), with weight gains ranging between 2.6% and 71.4%. Raman and IR spectroscopic analyses showed that upon grafting the fibres underwent slight conformational changes towards a more unordered state, due to the covalent and hydrogen bonds interactions occurring between the polymer (polyMAA) and the amorphous domains of silk fibres. To test the stability towards alkaline hydrolysis, the untreated and MAA-grafted silk fibres (weight gain of 71.4%) were immersed in NaOH 5% at 50°C for different times; the IR and Raman spectroscopic techniques were utilized to elucidate the degradation mechanism as well as the rearrangements of the fibres induced by the treatment. Upon hydrolysis, both the untreated and grafted fibres underwent an enrichment in β-sheet conformation, due to the preferential removal of the unordered domains. As a result of the covalent interactions with silk fibroin, the polymer increased its stability towards alkaline hydrolysis, since its complete solubilization was avoided and the transformation of its CONH2 groups into COO(-) and COOH was delayed. Vibrational spectroscopy proved to be a valid technique to investigate the mechanism and the effects of the hydrolytic attack, which are both fundamental to design new-generation silk-based materials.
authors.affiliation: Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/2, 40126 Bologna, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Pavoni
authors.affiliation: Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/2, 40126 Bologna, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Tozzi
authors.affiliation: Division of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, Nagano, Japan.
authors.forename: Masuhiro
authors.initials: M
authors.lastname: Tsukada
authors.affiliation: Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/2, 40126 Bologna, Italy. Electronic address: paola.taddei@unibo.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Taddei
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D005349:Fibroins / Q000737:chemistry*; D006860:Hydrogen Bonding; D006868:Hydrolysis; D017433:Protein Structure, Secondary; D012972:Sodium Hydroxide / Q000737:chemistry
chemical_list: D000178:Acrylamides; D001672:Biocompatible Materials; D012972:Sodium Hydroxide; D005349:Fibroins; C045985:methacrylamide
keywords: Poly-methacrylamide; Tussah silk fibroin; Vibrational spectroscopy