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<p>The poor photostability and lack of targeting capability of photosensitizers are the major challenge in the application of photodynamic inactivation (PDI) for food preservation. Based on the higher acidity at the fruit infection site, a pH-sensitive PDI nanosystem was prepared to address the issues and enhance the efficacy of PDI in food preservation. Protoporphyrin IX (PpIX) was grafted onto sodium diacetate alginate (DSA) through acylhydrazone bond, followed by ultrasonic dispersion, to obtain the pH-sensitive PDI nanosystem. The photostability of PpIX in the system was enhanced due to the singlet oxygen quenching induced by the self-aggregation of PpIX groups, but its photodynamic activity could be restored by releasing protoporphyrin hydrazide<b> (</b>PpIX-NH<sub>2</sub>) under acidic stimulation. Moreover, the antibacterial experiments confirmed the nanosystem exhibited strong antibacterial effects against <i>Escherichia coli</i> (<i>E. coli</i>) and <i>Staphylococcus aureus</i> (<i>S. aureus</i>) under weak acid stimulation with inhibition rates exceeding 99%, and the light exposure before acid stimulation had almost no effect on antibacterial activity. Additionally, the preservation experiment using cherry tomatoes as a model demonstrated that the nanosystem could delay fruit decay, reduce nutrient loss, and extend shelf life. The pH-responsive PpIX-NH<sub>2</sub>-DSA nanosystem effectively overcomes the limitations of poor photosensitizer stability and lack of targeting in PDI technology, providing a novel strategy for applying PDI technique in the field of food preservation.</p>

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pH-Sensitive Photodynamic Inactivation Nanosystem Based on Sodium Alginate-protoporphyrin IX for Fruit Preservation

  • 期刊论文

  • 发表日期：

    2026年5月30日

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  • Mengjie Li,
  • Ming Li,
  • Jiayu Li,
  • Jingli Zhang,
  • Weiquan Cai,
  • Yihua Yin,
  • Guanghua He,
  • Jiaying Wang

摘要

The poor photostability and lack of targeting capability of photosensitizers are the major challenge in the application of photodynamic inactivation (PDI) for food preservation. Based on the higher acidity at the fruit infection site, a pH-sensitive PDI nanosystem was prepared to address the issues and enhance the efficacy of PDI in food preservation. Protoporphyrin IX (PpIX) was grafted onto sodium diacetate alginate (DSA) through acylhydrazone bond, followed by ultrasonic dispersion, to obtain the pH-sensitive PDI nanosystem. The photostability of PpIX in the system was enhanced due to the singlet oxygen quenching induced by the self-aggregation of PpIX groups, but its photodynamic activity could be restored by releasing protoporphyrin hydrazide (PpIX-NH2) under acidic stimulation. Moreover, the antibacterial experiments confirmed the nanosystem exhibited strong antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under weak acid stimulation with inhibition rates exceeding 99%, and the light exposure before acid stimulation had almost no effect on antibacterial activity. Additionally, the preservation experiment using cherry tomatoes as a model demonstrated that the nanosystem could delay fruit decay, reduce nutrient loss, and extend shelf life. The pH-responsive PpIX-NH2-DSA nanosystem effectively overcomes the limitations of poor photosensitizer stability and lack of targeting in PDI technology, providing a novel strategy for applying PDI technique in the field of food preservation.