Natural versus synthetic curcuminoids as photosensitizers: Photobleaching and antimicrobial photodynamic therapy evaluation.

Antimicrobial photodynamic therapy (aPDT) has been studied as an alternative to combat bacterial resistance to the commonly used antibiotics. aPDT requires the use of a photosensitizer and curcumin is one of the more promising, though the usage of natural curcumin can be inconsistent in certain biomedical uses due to differences in soil condition and turmeric age, besides a large quantity of the plant is necessary to obtain useful amounts of the actual molecule. As such, a synthetic analogue is preferred as it is pure, and its components are better characterized. The present work studied photophysical differences in both natural and synthetic curcumin using photobleaching experiments and searched for whether differences existed in aPDT studies against Staphylococcus aureus. The results showed a faster O2 consumption and a singlet oxygen's generation rate lower by the synthetic curcumin, in comparison with the natural derivative. However, no statistical difference was observed when inactivating S. aureus and these results were following a concentration-based pattern. Thus, the use of synthetic curcumin is indicated, as it can be obtained in controlled amounts and with less environmental impact. Although there are small changes in a photophysical context comparing natural versus synthetic curcumins, we did not observe statistical differences in the photoinactivation of S.aureus bacteria, and reproducibility in biomedical contexts is better achieved with the synthetic analogue.

Melo NJ ，Tovar JSD ，Dovigo LN ，Dias LD ，Bagnato VS ，Inada NM ... -  《-》

Structural basis of antibacterial photodynamic action of curcumin against S. aureus.

Antimicrobial photodynamic therapy (aPDT) is an alternative tool to commercial antibiotics for the inactivation of pathogenic bacteria (e.g., S. aureus). However, there is still a lack of understanding of the molecular modeling of the photosensitizers and their mechanism of action through oxidative pathways. Herein, a combined experimental and computational evaluation of curcumin as a photosensitizer against S. aureus was performed. The radical forms of keto-enol tautomers and the energies of curcumin's frontier molecular orbitals were evaluated by density functional theory (DFT) to point out the photodynamic action as well as the photobleaching process. Furthermore, the electronic transitions of curcumin keto-enol tautomers were undertaken to predict the transitions as a photosensitizer during the antibacterial photodynamic process. Moreover, molecular docking was used to evaluate the binding affinity with the S. aureus tyrosyl-tRNA synthetase as the proposed a target for curcumin. In this regard, the molecular orbital energies show that the curcumin enol form has a character of 4.5% more basic than the keto form - the enol form is a more promising electron donor than its tautomer. Curcumin is a strong electrophile, with the enol form being 4.6% more electrophilic than its keto form. In addition, the regions susceptible to nucleophilic attack and photobleaching were evaluated by the Fukui function. Regarding the docking analysis, the model suggested that four hydrogen bonds contribute to the binding energy of curcumin's interaction with the ligand binding site of S. aureus tyrosyl-tRNA synthetase. Finally, residues Tyr36, Asp40, and Asp177 contact curcumin and may contribute to orienting the curcumin in the active area. Moreover, curcumin presented a photoinactivation of 4.5 log unit corroborating the necessity of the combined action of curcumin, light, and O2 to promote the photooxidation damage of S. aureus. These computational and experimental data suggest insights regarding the mechanism of action of curcumin as a photosensitizer to inactivate S. aureus bacteria.

Dias LD ，Aguiar ASN ，de Melo NJ ，Inada NM ，Borges LL ，de Aquino GLB ，Camargo AJ ，Bagnato VS ，Napolitano HB ... -  《-》

Antibacterial Efficacy and Mechanisms of Curcumin-Based Photodynamic Treatment against Staphylococcus aureus and Its Application in Juices.

Yuan Y ，Liu Q ，Huang Y ，Qi M ，Yan H ，Li W ，Zhuang H ... -  《-》

Curcumin derivatives as photosensitizers in photodynamic therapy: photophysical properties and in vitro studies with prostate cancer cells.

Kazantzis KT ，Koutsonikoli K ，Mavroidi B ，Zachariadis M ，Alexiou P ，Pelecanou M ，Politopoulos K ，Alexandratou E ，Sagnou M ... -  《-》

Antimicrobial photodynamic and wound healing activity of curcumin encapsulated in silica nanoparticles.

The multidrug resistance of pathogenic bacteria has become a serious problem to public health. Therefore finding novel approaches to combat multidrug resistant bacteria have therefore become increasingly important. One promising approach is antimicrobial photodynamic therapy (aPDT) which involves the use of photosensitizer (nontoxic dyes) that are excited by visible light and produce oxygen free radicals in the presence of oxygen. In this study, we investigated the antimicrobial photodynamic effect of free curcumin and curcumin silica nanoparticle as photosensitizer on planktonic and biofilm forms of Pseudomonas aeruginosa, Staphylococcus aureus. After performing MTT assay (to evaluate curcumin nano complex toxicity on human fibroblast cells), the effect of aPDT at 465 nm on bacteria in the planktonic and biofilm forms were investigated. The results showed that by using curcumin in the form of curcumin-silica nanoparticle as photosensitizer, there is a reduction in the number of bacteria in planktonic condition and bacterial biofilm production. Curcumin-silica nanoparticle not only did not show any significant cytotoxic effect against human normal fibroblast but also showed wound healing properties as confirmed with in vitro scratch assay. Therefore, aPDT based curcumin-silica nanoparticle could be suggested as novel approach in the treatment of multi drug resistant bacteria in chronic wound infection condition.

Mirzahosseinipour M ，Khorsandi K ，Hosseinzadeh R ，Ghazaeian M ，Shahidi FK ... -  《-》