Amino acid decorated xanthan gum coatings: Molecular arrangement and cell adhesion

Abstract

In this work, citric acid molecules mediated simultaneously the crosslinking of xanthan gum (XG) chains and the grafting of glutamic acid (Glu), cysteine (Cys), histidine (His) or tryptophan (Trp) to XG chains, as evidenced by Fourier-transform infrared spectroscopy, elemental and thermogravimetric analyses, and high-resolution X-ray photoelectron spectroscopy. XG coatings (∼60 nm thick) presented total surface energy (γS) of 65 mJ/m². The attachment of amino acids to the XG chains decreased γS values to ∼ 48 mJ/m² because the surface energy polar (γpS) component decreased. Circular dichroism (CD) spectra revealed that the helix conformation of XG chains was retained in XG and XG-Glu-coatings, but it was lost in the XG-His, XG-Cys-and XG-Trp-coatings due to intermolecular interactions between the amino acid side groups (thiol, imidazole, and indole). XG-based coatings presented no cytotoxicity. After 3 h of incubation, the adhesion of SH-5YSY neural cells in comparison to the control (100%) was XG-His (18%), XG-Cys (21.4%), XG (29%), XG-Trp (28.6%) and XG-Glu (46.4%). The decrease of% cell adhesion tended to be favored by the decrease of γpS, except for XG-Glu-and XG-Trp, and by the loss of helix molecular conformation of chains in the coatings.

Keywords

• Xanthan gum
• Amino acids
• Coatings
• Circular dichroism
• Surface energy
• Cell adhesion