Prodrug Self-Assemblies Based on Plant Volatile Aldehydes with Improved Stability and Antimicrobial Activity Against Plant Pathogens

Abstract

Plant volatile aldehydes (PVAs) such as cinnamaldehyde (Cin), citral (Cit), citronellal (Citr), and perillaldehyde (Per) have broad-spectrum antimicrobial activity and show great potential in agricultural sustainable production. However, most PVAs not only have very high volatility but also are easily degradable in environment, which seriously restricts their wide application. To address the inherent problems with PVAs, four prodrugs based on PVAs are fabricated by conjugating individually Cin, Cit, Citr, and Per to sodium bisulfite (Sod) through a simple addition reaction and subsequently self-assembled into nanoparticles (prodrug self-assemblies) in aqueous solutions. The results showed that pH of 7 and temperature of 35 °C are the optimal conditions for the formation of the prodrug self-assemblies with the highest self-assembly rates. The prepared prodrug self-assemblies are spherical nanoparticles with average particle sizes of 100–200 nm, almost no volatilization, and high surface activity and stability, and can respond to acidic and redox microenvironments to release PVAs. The prodrug self-assemblies showed synergistic antimicrobial activities against Sclerotinia sclerotiorum and Penicillium digitatum, and good biological safety to plants. Therefore, these findings have important implications for the efficient utilization of PVAs in agriculture, ensuring the safety of the ecological environment and realizing the sustainable development of agriculture.