Lactoferrin-Chitosan-TPP Nanoparticles: Antibacterial Action and Extension of Strawberry Shelf-Life

The aim of the present study was to produce lactoferrin (L) and chitosan (C) nanoparticles by ionic cross-linking with TPP and thereby increase the antimicrobial activity of biopolymers. The nanoparticles were synthesized in different proportions of biopolymers and TPP and characterized regarding their size, zeta potential, morphology, chemical interactions, structural characteristics, and antibacterial activity. They were also applied as coatings on strawberries with the aim of increasing fruit shelf-life. Circular dichroism spectra revealed that the addition of TPP altered the secondary structure of lactoferrin. The nanoparticles 3.5L:5.5C:1TPP and 4.5L:4.5C:1TPP showed higher zeta potential values and lower hydrodynamic diameters (+39.30 mV, 81.87 nm and +33.07 mV, 97.67 nm, respectively) and intense bacteriostatic action against S. aureus (0.0370 mg/ml and 0.0463 mg/ml, respectively). The minimum inhibitory concentration of these nanoparticles was three times lower than those of pure biopolymers. When applied to strawberries coating, the nanoparticles delayed the ripening and degradation of the fruit. These results confirm that it is possible to intensify the antimicrobial properties of lactoferrin and chitosan through ionic cross-linking with TPP and, thus, expand their use as natural food preservatives.