Are aqueous solutions of choline-based ionic liquid biocompatible cross-linkers for collagen?

Abstract Identification of biocompatible cross-linkers is extremely important in the field of biomaterials, as it aids in improving stability to protein but also elicits less immune response. Towards this, aqueous solution of choline-based ILs (CILs) has been keyed out as biocompatible cross-linkers with an aim to understand their impact and effect on stabilization of collagen. The changes in the hydration dynamics of collagen treated with aqueous solution of CILs has been probed using transverse NMR relaxation and impedance measurements. Upon treatment of aqueous solution of CILs with collagen, there is a reorientation in the surrounding water milieu suggesting compactness in the structure of collagen, which is indicative of crosslinking. Further, the conformational and thermal stability of collagen have been substantiated. It is ascertained that the helicity of collagen remains intact as witnessed through the Rpn values measured through circular dichroic measurements and shifts in frequencies of amide bands as measured through FT-IR measurements. A significant increase in the melting and denaturation temperature suggesting stability of collagen has been observed through DSC measurements. Aqueous solution of CILs treated collagen scaffolds have been further appraised for crosslinking efficiency, enzymatic stability, hemolytic and platelet attachment assays. The efficacy of aqueous solution of CILs treated scaffolds has been evaluated for biocompatibility with NIH-3T3 fibroblasts cells and further confirmed by the phase-contrast microscopic images of these cells. Interaction between the collagen and aqueous solution of choline-based ILs is typically anchored by non-covalent interactions like electrostatic, hydrogen, and van der Waals interactions. Therefore, the current study implies that the aqueous solution of CILs can be explored as biocompatible cross-linkers for collagen and thus can be employed for biomedical applications.