Synthesis of Carboxymethyl Cellulose and Agar-Based Multifunctional Films Reinforced with Cellulose Nanocrystals and Shikonin

Multifunctional carboxymethyl cellulose/agar-based smart films were fabricated combining cellulose nanocrystals (CNC) separated from onion peel and shikonin isolated from the roots of Lithospermum erythrorhizon. The CNC had a nanosized crystal structure with a length and width of 225.6 ± 42.4 and 10.2 ± 2.2 nm, respectively, having an aspect ratio of 22.1. The CNC and shikonin were consistently dispersed in the polymer matrix. The integration of CNC significantly improved physical properties, for instance, mechanical, water resistance, and optical properties. The addition of shikonin provided functional properties such as pH-responsive color change, antioxidant and antibacterial properties without significant change in the water vapor permeability, and thermal stability of the film. The films also exhibited high light transmittance with increased UV-light barrier properties. The composite film also showed potent antimicrobial and antioxidant activities. The composite film with enhanced physical and functional properties has high potential for quality detection in active food packaging applications.