Fish Scales for Wearable Patches: Tailoring Films Assembled From Fish Waste Gelatin, Carbon Dots and Chitin Nanocrystals

The properties of gelatin and collagen extracted from fishery wastes, specifically from mullet (Mugil Cephalus) scales, are modified with the aim to achieve biocompatible films with tunable characteristics to design sustainable UV protection solutions in the healthcare sector. Different additives are used to the scope including plasticizers, cross-linkers, surfactants and optical modifiers. Carbon dots (CDs) obtained from seabass (Dicentrarchus labrax) scales combined with polysorbate-20 (PS) as a dispersant agent, enable the fabrication of materials capable of blocking UV radiation almost completely, a crucial feature for dermal contact applications. The addition of hydrophobic surfactants and crosslinkers as citric acid, chitosan and surface deacetylated chitin nanocrystals (CsNCs) allowed to modulate the water adsorption of the films in the range 3–30% and to reach a twofold and 4.5-fold increase of tensile strength and elastic modulus, respectively, as compared to the neat gelatin film. Moreover, film thickness is shown to be another adjustable parameter to enhance optic, mechanical, and permeation properties: the higher the thickness, the greater the UV-blocking properties, elongation-at-break and water vapor permeability, leading to films with attractive characteristics as wearable patches.