Biodegradable Protein Films Based on a Complex Coacervate of Gelatin and Sodium Caseinate for Dermal Application

Proteins offer specific functional properties for the development of biodegradable, biopolymer-based materials. Gelatin and sodium caseinate can electrostatically interact in solution and form a complex coacervate, which was used to produce films with enhanced properties intended for dermal application in the cosmetic industry. Complex coacervate based films showed improved physical, mechanical, and barrier properties owing to their intermolecular interactions. Their thermal properties and chemical composition remained unchanged due to the intermolecular interactions being predominantly electrostatic. As sufficient elasticity of films is necessary for their production and use in the cosmetic industry, the optimal type and concentration of plasticizers were determined. Films containing 30% glycerol exhibited the highest improvement in mechanical properties, with balanced barrier and physical properties. The presence of glycerol and its interaction with protein side groups was detected in the FTIR spectra of films. SEM micrographs revealed morphological improvements on the surface and in the cross-sections of films plasticized with glycerol. Overall, the produced films demonstrated satisfactory properties for cosmetic applications and represent a potential replacement for nonsustainable synthetic materials currently in use.