ε-Polylysine-mediated assembly regulating the band gap of natural polyphenols for boosted photodynamic antimicrobial effect

• ε-PL was introduced to improve the optical properties of quercetin . • The incorporation of ε-PL reduced the band gap, enhancing light harvesting. • Que/ε-PL NPs exhibited remarkable antibacterial activity under light irradiation. • Que/ε-PL NPs-based films extended cherry shelf life to 10 days, preserving quality. The photodynamic antibacterial activity of natural polyphenols as green photosensitizers possesses potential in food contamination control, but it is still limited by poor light harvesting activity and insufficient ROS generation. Herein, quercetin, a naturally occurring flavonoid, was integrated with cationic ε-Polylysine ( ε-PL) to synthesize Que/ε-PL nanoparticles (NPs) with enhanced photodynamic antimicrobial activity. According to the band gap calculation, the addition of ε-PL significantly reduced the band gap energy, thereby promoting light harvesting and ROS generation. By integrating boosted light-driven ROS generation, positive electrical properties and ε-PL intrinsic antimicrobial activity, Que/ε-PL NPs exhibited remarkable antimicrobial activity. Also, Que/ε-PL NPs possessed antioxidant activity. Subsequently, Que/ε-PL NPs were incorporated into agar (AG) matrix to form the composite packaging films for prolonging the storage period of cherries and maintaining the quality of goods. The study creates an innovative approach to improve the photodynamic antibacterial activity of natural polyphenols through the natural inter-molecular assembly, ensuring the safety of agricultural products practically.