High Antibacterial Activity of Spermine Functionalized Carbon Dots and Its Potential Application in Sausage Preservation

Carbon-based antibacterial materials have attracted considerable attention to preserve food and prolong the shelf life. In this study, four types of carbon dots (CDs) based on glucose and biogenic amines including spermine (Spe), putrescine (Put), spermidine (Spd) and histamine (His) were synthesized by microwave synthesis. The nanosized, amorphous and nearly spherical CDs had excellent water solubility. The four positive charge CDs containing carbon, nitrogen and oxygen elements could emit blue fluorescent. Among these CDs, Spe-CDs displayed the best antibacterial activity for S. aureus, and the values of minimum inhibitory concentration and minimum bactericidal concentration were 0.04 and 0.08 mg/mL, respectively. The exposure of Spe-CDs was able to disrupt the cell wall and membrane of S. aureus, which resulted in the shrinkage and disintegration of S. aureus observed in cell morphology. The excellent antibacterial activity of Spe-CDs was attributed to its smaller size, higher surface positive charge and higher ROS production, compared to Put-CDs, Spd-CDs and His-CDs. The preservation effect of Spe-CDs on sausage was explored during 4 °C storage, which could effectively inhibit the spoilage of sausage and prolong their shelf-life. The Spe-CDs might have the potential to be a food antibacterial preservation agent.