Fabrication, characterization, and performance of antimicrobial alginate-based films containing thymol-loaded lipid nanoparticles: Comparison of nanoemulsions and nanostructured lipid carriers.

Antimicrobial biopolymer films were prepared by incorporating thymol-loaded nanostructured lipid carriers (NLC) or nanoemulsions (NE) into Ca-alginate solutions. Thymol-loaded-NLCs with thymol/lipid mass ratios of 0.1 and 0.2 were prepared and then used to fabricate NLC/alginate films containing either 20% (NLC20 film) or 10% (NLC10 film) of NLCs. Consequently, these two films had the same total thymol mass fraction: R thymol/alginate = 0.02. A nanoemulsion-loaded film (NE film) containing the same amount of thymol and a neat alginate film (control) were also prepared. Incorporation of the NLCs increased the porosity and surface roughness, thickness, water vapor permeability, and yellowness of the films, but decreased their water contact angle, mechanical strength, and swelling ratio. The release of thymol into the air and into water-ethanol solutions was slower for NLC-loaded than NE-loaded films, moreover being slower for the NLC20 than NLC10 films. The antimicrobial activity of the active films was tested on ground beef samples. Their antimicrobial activity was correlated to their release rates, with the NLC20 film giving the longest protection against the enumerated microorganisms. Our results show that encapsulating antimicrobial essential oils within NLCs was more effective at creating antimicrobial films with sustained release properties than encapsulating them within NEs.

Fabrication and characterization of alginate-based films functionalized with nanostructured lipid carriers.

This study focuses on the fabrication and characterization of alginate-based films functionalized by incorporating nanostructured lipid carriers (NLCs). The effect of different NLC/alginate mass ratios (R = 0.05, 0.1, 0.2, and 0.35) on the physical, morphological, mechanical, and barrier properties of the calcium-alginate films was evaluated. The addition of the NLCs significantly improved the UV-absorbing properties, without greatly altering their transparent appearance. As the NLC concentration increased, the tensile strength, elastic modulus, and swelling ratio of the films decreased, while their thermal stability, water vapor permeability, and contact angle increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the films revealed that NLC incorporation led to a more porous internal structure and a rougher surface. Fourier Transform Infrared (FTIR) analysis indicated that there were no new interactions between the calcium-alginate and NLC constituents within the films. Overall, this study shows that NLCs can be successfully incorporated into calcium-alginate films and used to modulate their physicochemical properties. In future, it will be useful to examine the potential of these films to incorporate hydrophobic bioactives such as drugs, nutraceuticals, antimicrobials, antioxidants, and pigments for specific pharmaceutical or food applications.