Preparation and characterization of epigallocatechin-3-gallate loaded melanin nanocomposite (EGCG @MNPs) for improved thermal stability, antioxidant and antibacterial activity

Epigallocatechin gallate loaded melanin nanoparticles (EGCG@MNPs) have been prepared aiming for the development of an eco-friendly food preservation nanomaterials with good thermal stability, antioxidant and antibacterial activity. The EGCG@MNPs presents a uniform and well dispersed spherical structure with average diameter below 100 nm. The structure analysis results show that EGCG@MNPs exist in the form of macromolecular polymers rather than crystalline structure, and EGCG was loaded onto MNPs via hydrophobic interaction and Π-Π stacking. Moreover, EGCG@MNPs has superior thermal stability and antioxidant activity. After processing at 121 °C, the scavenging ratio of EGCG@MNPs on DPPH• and ABTS•+ were 67.14 ± 1.35% and 46.99 ± 1.12%, respectively, while the value of pure EGCG on DPPH• and ABTS•+ were only 38.37 ± 0.67% and 4.01 ± 0.93%. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EGCG@MNPs to Escherichia coli and Staphylococcus aureus were 0.8 mg/mL, 1.6 mg/mL and 0.2 mg/mL, 0.4 mg/mL respectively. In summary, the MNPs provided stable media to bind EGCG and the resulted EGCG@MNPs nanoparticles retained strong antioxidant and antibacterial properties after heat treated, which suggested the potential of EGCG@MNPs for the development of new food preservation nanomaterials and/or food active packaging fillers.