UV/enzyme dual responsive photosensitizer‐loaded 4‐(Phenylazo)benzoic Acid‐mPEG nanosystem for enhanced photodynamic insecticide efficacy

To improve photostability and enhance utilization rate and reduce pest resistance, a new strategy based on the combination of photodynamic insecticide action and stimulus‐responsive polymer micelles is developed. 4‐(phenylazo)benzoic acid (PBA)‐modified poly(ethylene glycol) monomethyl ether (mPEG) conjugate is prepared by the esterification reaction of mPEG and PBA, and followed by self‐assembly in aqueous solution to obtain polymeric nanoparticles. TEM shows that the nanoparticles have a core‐shell structure and an average diameter of 78 nm. DLS shows that the nanoparticles are stability in water solution but can change their structure in response to UV light and/or esterase stimulation. The photodegradation of Protoporphyrin IX (PpIX) encapsulated in the nanoparticles can be effectively inhibited because of aggregation‐caused quenching effect, whose maximum photodegradation rate is about 20.54% after 8 h exposure to daylight compared with the complete photodegradation of free PpIX. UV light and/or esterase stimulus can trigger PpIX release and result in a high photodynamic activity. Compared with free PpIX, the PpIX‐loaded nanoparticles show a higher phototoxicity to insect cells and the daylight pretreatment has little influence on the phototoxicity. A noval drug delivery system based on poly(ethylene glycol) monomethyl ether (mPEG) and 4‐(Phenylazo)benzoic Acid (PBA) is designed to load Protoporphyrin IX (PpIX) and control its release in the presence of UV light or esterase. The system not only improves the photodegradation of PpIX but also enhances the insecticidal efficiency.