**Electrospinning of Fish Gelatin Solution Containing Citric Acid: An Environmentally Friendly Approach to Prepare Crosslinked Gelatin Fibers**

**Anna Liguori 1,**†**, Jone Uranga 2,**†**, Silvia Panzavolta 1, Pedro Guerrero 2, Koro de la Caba 2,\* and Maria Letizia Focarete 1,\***


Received: 31 July 2019; Accepted: 30 August 2019; Published: 1 September 2019

**Abstract:** The majority of the crosslinking approaches employed to confer water resistance properties to electrospun gelatin mats are based on the use of potential cytotoxic agents, turning out to be not suitable for biomedical applications. Environmentally friendly chemical strategies based on the use of non-toxic agents are, therefore, strongly demanded. In the present work, the possibility to produce crosslinked electrospun fish gelatin mats by electrospinning an aqueous solution, containing citric acid as a crosslinking agent, is reported. The effect of pH on solution rheological properties, as well as on the electrospun mat morphology, chemistry, and crosslinking degree, is assessed. The increase of solution pH from 1.8 to 3.7 allows for obtaining fibers that maintain the fibrous morphology also in the mat. Subsequent thermal treatment of the electrospun mat (80 ◦C for 30 min) turns out to increase the crosslinking degree and morphological stability of the mat.

**Keywords:** fish gelatin; citric acid; electrospinning; pH; thermal treatment; gelatin structure; crosslinking degree
