Black Goji Berry Extract as a Natural Photosensitizer for Photodynamic Inactivation of Microbial Strains: A Promising Approach

Antimicrobial resistance is a critical public health concern directly contributing to many deaths globally. Unearthing new protocols to tackle pathogenic microorganisms is vital. Photodynamic inactivation (PDI) is an efficient method for treating cancer and chronic microbial infections. PDI merges light with a photosensitizer to prompt the generation of reactive oxygen species and free radicals, not including O2. These molecules cause a phototoxic reaction and lead to the death of microorganisms. Recent advancements in photodynamic inactivation are focused on the exploration of natural photosensitizers.

In this study, Black Goji Berry Extract (BGBE) was utilized as a photosensitizer at 50 mg/mL concentration. The incubation periods for the extract were 10 and 15 minutes, respectively. Phototoxic reactions were induced using ultraviolet (UV) light, specifically within the 315-400 nm range at an intensity of 8W, for an illumination period of 5 min. This study utilized microbial strains of Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa, and Escherichia coli as test subjects. All the strains went through treatments under these specified conditions. Results were reported after comparing controls and treatments.

Incubating with BGBE for 10-15 min followed by a 5-min black UV illumination induced a phototoxic reaction in bacterial strains such as S. aureus, P. aeruginosa, and E. coli. This resulted in a decrease in bacterial viability by 0.75-0.92 log10 (CFU/mL). No significant difference was observed between the effects on Gram-positive and Gram-negative strains (P>0.05). Moreover, no phototoxic reaction was observed in Candida albicans under similar conditions.

While a sublethal photodynamic reaction was recorded in specific bacterial strains post-photodynamic inactivation utilizing BGBE, BGB exhibits potential as a natural source for innovative photosensitizers.