Effect of Chitosan-Riboflavin Bioconjugate on Green Mold Caused by Penicillium digitatum in Lemon Fruit.

Penicillium digitatum is the causal agent of green mold, a primary postharvest disease of citrus fruits. This study evaluated the efficacy of a novel photoactive chitosan-riboflavin bioconjugate (CH-RF) to control green mold in vitro and in lemon fruit. The results showed total inhibition of P. digitatum growth on APDA supplemented with CH-RF at 0.5% (w/v) and a significant reduction of 84.8% at 0.25% (w/v). Lemons treated with CH-RF and kept under controlled conditions (20 °C and 90-95% relative humidity) exhibited a noteworthy reduction in green mold incidence four days post-inoculation. Notably, these effects persisted, with all treatments remaining significantly distinct from the control group until day 14. Furthermore, CH-RF showed high control of green mold in lemons after 20 days of cold storage (5 ± 1 °C). The disease incidence five days after cold storage indicated significant differences from the values observed in the control. Most CH-RF treatments showed enhanced control of green mold when riboflavin was activated by white-light exposure. These findings suggest that this novel fungicide could be a viable alternative to conventional synthetic fungicides, allowing more sustainable management of lemon fruit diseases.

Recent Photosensitizer Developments, Delivery Strategies and Combination-based Approaches for Photodynamic Therapy†.

Photodynamic therapy of cancer (PDT) is a therapeutic technique, minimally invasive, which is currently used to treat cancerous lesions and tumors that have been in the spotlight for its potential over the recent decades. Nonetheless, PDT still needs further development to become a first-option treatment for patients. This review compiles recent progress in several aspects of the current research in the constantly growing area of PDT to overcome the main challenges as an attempt to serve as a guide and reference for newcomers into this research area. This review has been prepared to highlight the use of chemical modifications on photosensitizers to improve their solubility, photostability, selectivity and phototoxicity. Additionally, the use of liposomes and cavitands as drug delivery systems to aid in the biodistribution and bioaccumulation of photosensitizers is presented. Also, the combination of PDT with chemotherapy or immunotherapy as an option to boost and improve treatment outcomes is discussed. Finally, the inhibition of antioxidant enzymes as a strategy for a synergistic effect to ameliorate the performance of the photosensitizers in PDT is presented as an alternative for future researchers.

Protoporphyrin IX-Chitosan Oligosaccharide Conjugate with Potent Antifungal Photodynamic Activity.

A new chemical conjugate between protoporphyrin IX (PPIX) and chitosan oligosaccharides (CH) was prepared and evaluated in vitro as an antifungal agent against Penicillium digitatum. Chemical characterization and photophysical/photochemical studies were conducted. The antifungal effect of the CH-PPIX conjugate was compared to its components (PPIX and CH) and a physical mixture of both, under dark and illuminated conditions. The CH-PPIX conjugate was photostable and inhibited fungal growth with 100% efficiency at a dose of 0.005% w/v under visible light irradiation, while no antifungal activity was observed in the dark. Under the same conditions, CH and PPIX did not display any fungicidal activity, demonstrating the improved properties of the conjugate. Insights into the mechanism of fungal inactivation revealed an efficient spore uptake and photoinduced membrane damage through singlet oxygen generation. This new bioconjugate, which is based on natural components, represents a promising agent for fungicidal formulations based on antimicrobial photodynamic therapy.

Novel Chitosan-Riboflavin Conjugate with Visible Light-Enhanced Antifungal Properties against Penicillium digitatum.

A novel chemical conjugate between chitosan (CH) and riboflavin (RF) has been synthesized and characterized via Fourier transform infrared, NMR, and other spectroscopic methods. Photophysical and photochemical properties such as absorption spectra, fluorescence emission, fluorescence anisotropy, and singlet oxygen generation were characterized as well. This new biopolymer-based conjugate was designed to have an antifungal effect enhanced through antimicrobial photodynamic therapy. The antifungal effect of this conjugate (CH-RF) was compared with CH and RF against Penicillium digitatum in vitro. The conjugate showed the highest fungal growth inhibition of all systems tested at a dose of 0.5% w/v. This new biopolymer-based compound could be a promising alternative to fungicides used in citrus fruits postharvest.