Facile synthesis of zinc chloride/formic acid based deep eutectic solvents for mild and efficient dissolution of collagen with high concentration

Abstract

The poor solubility and weak thermostability of collagen limit its processing and applications, and an ideal solvent for effectively dissolving collagen remains highly appealing yet lacking. Despite the emergence of synthesized ionic liquids and deep eutectic solvents (DESs), they are currently challenged by the requirement of high dissolving temperatures and the significant degradation of collagen during dissolution. Herein, the DES of zinc chloride (ZnCl2) and formic acid (FA) at a molar ration of 1:5 (ZnCl2:FA(1:5)) containing 40% (w/w) water that simultaneously enabled lower dissolution temperature (4 °C), high solubility (27.4 wt%) of collagen, and long-term (2 days) preservation of native collagen structure was rationally engineered. The solubility, structure, and properties of collagen were highly dependent on the chemical compositions of the ZnCl2:FA based DES. The remarkable dissolving capacity of the DES should be due to its powerful hydrogen bonding network and favorable interactions with collagen. The DES demonstrated as an alternative to traditional solvents in fabricating electrospun collagen nanofibers and cast collagen films. This work provides a promising solvent platform for preparing collagen based materials and the DES may be used as a potential media for collagen chemistry.