Low-dose blue light irradiation enhances the antimicrobial activities of curcumin against Propionibacterium acnes

Photodynamic activation of phytochemical-antibiotic combinations for combatting Staphylococcus aureus from acute wound infections

Staphylococcus aureus is characterized by its high resistance to conventional antibiotics, particularly methicillin-resistant (MRSA) strains, making it a predominant pathogen in acute and chronic wound infections. The persistence of acute S. aureus wound infections poses a threat by increasing the incidence of their chronicity. This study investigated the potential of photodynamic activation using phytochemical-antibiotic combinations to eliminate S. aureus under conditions representative of acute wound infections, aiming to mitigate the risk of chronicity. The strategy applied takes advantage of the promising antibacterial and photosensitising properties of phytochemicals, and their ability to act as antibiotic adjuvants. The antibacterial activity of selected phytochemicals (berberine, curcumin, farnesol, gallic acid, and quercetin; 6.25-1000 μg/mL) and antibiotics (ciprofloxacin, tetracycline, fusidic acid, oxacillin, gentamicin, mupirocin, methicillin, and tobramycin; 0.0625-1024 μg/mL) was screened individually and in combination against two S. aureus clinical strains (methicillin-resistant and -susceptible-MRSA and MSSA). The photodynamic activity of the phytochemicals was assessed using a light-emitting diode (LED) system with blue (420 nm) or UV-A (365 nm) variants, at 30 mW/cm2 (light doses of 9, 18, 27 J/cm2) and 5.5 mW/cm2 (light doses of 1.5, 3.3 and 5.0 J/cm2), respectively. Notably, all phytochemicals restored antibiotic activity, with 9 and 13 combinations exhibiting potentiating effects on MSSA and MRSA, respectively. Photodynamic activation with blue light (420 nm) resulted in an 8- to 80-fold reduction in the bactericidal concentration of berberine against MSSA and MRSA, while curcumin caused 80-fold reduction for both strains at the light dose of 18 J/cm2. Berberine and curcumin-antibiotic combinations when subjected to photodynamic activation (420 nm light, 10 min, 18 J/cm2) reduced S. aureus culturability by ≈9 log CFU/mL. These combinations lowered the bactericidal concentration of antibiotics, achieving a 2048-fold reduction for gentamicin and 512-fold reduction for tobramycin. Overall, the dual approach involving antimicrobial photodynamic inactivation and selected phytochemical-antibiotic combinations demonstrated a synergistic effect, drastically reducing the culturability of S. aureus and restoring the activity of gentamicin and tobramycin.

Membranes composed of poly(lactic acid)/poly(ethylene glycol) and Ora-pro-nóbis (Pereskia aculeata Miller) extract for dressing applications

Wounds are considered one of the most critical medical conditions that must be managed appropriately due to the psychological and physical stress they cause for patients, as well as creating a substantial financial burden on patients and global healthcare systems. Nowadays, there is a growing interest in developing nanofiber mats loaded with varying plant extracts to meet the urgent need for advanced wound ressings. This study investigated the development and characterization of poly(lactic acid) (PLA)/ poly(ethylene glycol) (PEG) nanofiber membranes incorporated with Ora-pro-nóbis (OPN; 12.5, 25, and 50 % w/w) by the solution-blow-spinning (SBS) technique. The PLA/PEG and PLA/PEG/OPN nanofiber membranes were characterized by scanning electron microscopy (SEM), thermal properties (TGA and DSC), Fourier transform infrared spectroscopy (FTIR), contact angle measurements and water vapor permeability (WVTR). In addition, the mats were analyzed for swelling properties in vitro cell viability, and fibroblast adhesion (L-929) tests. SEM images showed that smooth and continuous PLA/PEG and PLA/PEG/OPN nanofibers were obtained with a diameter distribution ranging from 171 to 1533 nm. The PLA/PEG and PLA/PEG/OPN nanofiber membranes showed moderate hydrophobicity (~109-120°), possibly preventing secondary injuries during dressing removal. Besides that, PLA/PEG/OPN nanofibers exhibited adequate WVTR, meeting wound healing requirements. Notably, the presence of OPN gave the PLA/PEG membranes better mechanical properties, increasing their tensile strength (TS) from 3.4 MPa (PLA/PEG) to 5.3 MPa (PLA/PEG/OPN), as well as excellent antioxidant properties (Antioxidant activity with approximately 45 % oxidation inhibition). Therefore, the nanofiber mats based on PLA/PEG, especially those incorporated with OPN, are promising options for use as antioxidant dressings to aid skin healing.

Curcumin-mediated photodynamic therapy for mild to moderate Acne: A self-controlled split-face randomized study

OBJECTIVE

To evaluate the effectiveness and safety of Curcumin-mediated Photodynamic Therapy (Curcumin-PDT) in the treatment of mild to moderate acne.

METHODS

In this randomized split-face controlled study, 11 patients with mild to moderate acne were randomly divided into two groups. One side received a single 445 nm LED light exposure of 36 J/cm2, while the other side received Curcumin-PDT. The process of Curcumin-PDT involves the application of a mask containing 1 % curcumin for 20 min, followed by exposure to 445 nm LED light at 36 J/cm². The treatment consists of sessions spaced every 3 days, with a total of 2 treatments per week, administered continuously for 2 weeks. Efficacy assessment and comparison were conducted on both groups of patients before treatment and 2 weeks after the last treatment, and adverse reactions were observed and recorded.

RESULTS

At the 2-week follow-up after the last treatment, the total lesion clearance rates for Curcumin-PDT and monotherapy light were 54.7 ± 21.5 % and 28.1 ± 19.9 %, respectively (P = 0.001). The clearance rates for non-inflammatory lesions were 32.3 ± 25.7 % and 21.9 ± 14.0 % for Curcumin-PDT and monotherapy light sides (P = 0.252), while for inflammatory lesions, the clearance rates were 59.3 ± 28.2 % and 36.5 ± 21.6 % (P = 0.013). Both groups experienced mild erythema after treatment, which subsided within 1-2 h. Two patients developed mild localized pigmentation, which self-resolved after 1 month of follow-up. Both groups did not exhibit edema, crust formation, scaling, pigment reduction, or scarring.

CONCLUSION

Curcumin-PDT can be considered a safe and effective method for the treatment of mild to moderate acne.

Utilizing the photodynamic properties of curcumin to disrupt biofilms in Cutibacterium acnes: A promising approach for treating acne

BACKGROUND

The treatment of acne vulgaris is often challenging due to the antibiotic resistance frequently observed in Cutibacterium acnes (C.acnes), a prevalent bacterium linked to this condition.

OBJECTIVE

The objective of this research was to examine the impact of curcumin photodynamic therapy (PDT) on the survival of C.acnes and activity of biofilms produced by this microorganism.

METHODS

Following the Clinical and Laboratory Standards Institute (CLSI) guidelines, we assessed the drug sensitivity of 25 clinical C.acnes strains to five antibiotics (erythromycin, clindamycin, tetracycline, doxycycline, minocycline) and curcumin by implementing the broth microdilution technique. In addition, we established C.acnes biofilms in a laboratory setting and subjected them to curcumin-PDT(curcumin combined with blue light of 180 J/cm2). Afterwards, we evaluated their viability using the XTT assay and observed them using confocal laser scanning microscopy.

RESULTS

The result revealed varying resistance rates among the tested antibiotics and curcumin, with erythromycin, clindamycin, tetracycline, doxycycline, minocycline, and curcumin exhibiting resistance rates of 72 %, 44 %, 36 %, 28 %, 0 %, and 100 %, respectively. In the curcumin-PDT inhibition tests against four representative antibiotic-resistant strains, it was found that the survival rate of all strains of planktonic C. acnes was reduced, and the higher the concentration of curcumin, the lower the survival rate. Furthermore, in the biofilm inhibition tests, the vitality and three-dimensional structure of the biofilms were disrupted, and the inhibitory effect became more significant with higher concentrations of curcumin.

CONCLUSION

The results emphasize the possibility of using curcumin PDT as an alternative approach for the treatment of C.acnes, especially in instances of antibiotic-resistant variations and infections related to biofilms.

A Systematic Evaluation of Curcumin Concentrations and Blue Light Parameters towards Antimicrobial Photodynamic Therapy against Cariogenic Microorganisms

Dental caries is a highly preventable and costly disease. Unfortunately, the current management strategies are inadequate at reducing the incidence and new minimally invasive strategies are needed. In this study, a systematic evaluation of specific light parameters and aqueous curcumin concentrations for antimicrobial photodynamic therapy (aPDT) was conducted. Aqueous solutions of curcumin were first prepared and evaluated for their light absorbance after applying different ~56 mW/cm2 blue light treatments in a continuous application mode. Next, these same light treatments as well as different application modes were applied to the curcumin solutions and the molar absorptivity coefficient, reactive oxygen species (ROS) release, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) for Streptococcus mutans and the MIC and minimum fungicidal concentration (MFC) for Candida albicans were measured. After up to 1 min of light treatment, the molar absorptivity of curcumin when added to culture media was lower than that for water only; however, at higher energy levels, this difference was not apparent. There was a noted dependence on both ROS type and cariogenic microorganism species on the sensitivity to both blue light treatment and application mode. In conclusion, this study provides new information towards improving the agonistic potential of aPDT associated with curcumin against cariogenic microorganisms.

Polyphenolic natural products as photosensitizers for antimicrobial photodynamic therapy: recent advances and future prospects

Antimicrobial photodynamic therapy (aPDT) has become a potent contender in the fight against microbial infections, especially in the context of the rising antibiotic resistance crisis. Recently, there has been significant interest in polyphenolic natural products as potential photosensitizers (PSs) in aPDT, given their unique chemical structures and inherent antimicrobial properties. Polyphenolic natural products, abundant and readily obtainable from natural sources, are generally regarded as safe and highly compatible with the human body. This comprehensive review focuses on the latest developments and future implications of using natural polyphenols as PSs in aPDT. Paramount polyphenolic compounds, including curcumin, hypericin, quercetin, hypocrellin, celastrol, riboflavin, resveratrol, gallic acid, and aloe emodin, are elaborated upon with respect to their structural characteristics, absorption properties, and antimicrobial effects. Furthermore, the aPDT mechanism, specifically its targeted action on microbial cells and biofilms, is also discussed. Polyphenolic natural products demonstrate immense potential as PSs in aPDT, representing a promising alternate approach to counteract antibiotic-resistant bacteria and biofilm-related infections.

Riboflavin and Its Derivates as Potential Photosensitizers in the Photodynamic Treatment of Skin Cancers

Riboflavin, a water-soluble vitamin B2, possesses unique biological and physicochemical properties. Its photosensitizing properties make it suitable for various biological applications, such as pathogen inactivation and photodynamic therapy. However, the effectiveness of riboflavin as a photosensitizer is hindered by its degradation upon exposure to light. The review aims to highlight the significance of riboflavin and its derivatives as potential photosensitizers for use in photodynamic therapy. Additionally, a concise overview of photodynamic therapy and utilization of blue light in dermatology is provided, as well as the photochemistry and photobiophysics of riboflavin and its derivatives. Particular emphasis is given to the latest findings on the use of acetylated 3-methyltetraacetyl-riboflavin derivative (3MeTARF) in photodynamic therapy.

Dual Action of Curcumin as an Anti- and Pro-Oxidant from a Biophysical Perspective

Curcumin, a natural polyphenol widely used as a spice, colorant and food additive, has been shown to have therapeutic effects against different disorders, mostly due to its anti-oxidant properties. Curcumin also reduces the efficiency of melanin synthesis and affects cell membranes. However, curcumin can act as a pro-oxidant when blue light is applied, since upon illumination it can generate singlet oxygen. Our review aims to describe this dual role of curcumin from a biophysical perspective, bearing in mind its concentration, bioavailability-enhancing modifications and membrane interactions, as well as environmental conditions such as light. In low concentrations and without irradiation, curcumin shows positive effects and can be recommended as a beneficial food supplement. On the other hand, when used in excess or irradiated, curcumin can be toxic. Therefore, numerous attempts have been undertaken to test curcumin as a potential photosensitizer in photodynamic therapy (PDT). At that point, we underline that curcumin-based PDT is limited to the treatment of superficial tumors or skin and oral infections due to the weak penetration of blue light. Additionally, we conclude that an increase in curcumin bioavailability through the using nanocarriers, and therefore its concentration, as well as its topical use if skin is exposed to light, may be dangerous.

In Vitro Evaluation of Photodynamic Activity of Plant Extracts from Senna Species against Microorganisms of Medical and Dental Interest

Background: Bacterial resistance requires new treatments for infections. In this context, antimicrobial photodynamic therapy (aPDT) is an effective and promising option. Objectives: Three plant extracts (Senna splendida, Senna alata, and Senna macranthera) were evaluated as photosensitizers for aPDT. Methods: Cutibacterium acnes (ATCC 6919), Streptococcus mutans (ATCC 35668), Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028) were evaluated. Reactive oxygen species production was also verified. Oral keratinocytes assessed cytotoxicity. LC-DAD-MS analysis identified the chemical components of the evaluated extracts. Results: Most species cultured in the planktonic phase showed total microbial reduction (>6 log10 CFU/mL/p < 0.0001) for all extracts. C. albicans cultured in biofilm showed total microbial reduction (7.68 log10 CFU/mL/p < 0.0001) for aPDT mediated by all extracts. Extracts from S. macranthera and S. alata produced the highest number of reactive oxygen species (p < 0.0001). The S. alata extract had the highest cell viability. The LC-DAD-MS analysis of active extracts showed one naphthopyrone and seven anthraquinones as potential candidates for photoactive compounds. Conclusion: This study showed that aPDT mediated by Senna spp. was efficient in microbial suspension and biofilm of microorganisms of medical and dental interest.

Photodynamic inactivation of Staphylococcus aureus by ecological antibacterial solutions associating LED (ʎ 450 ± 10 nm) with curcumin and olive leaf extracts

Antimicrobial resistance is a problem in contemporary society, with Staphylococcus aureus standing out as a threat due to its ability to colonize, its pathogenicity, and its expression of several virulence factors. In this context, antimicrobial photodynamic inactivation (aPDI) emerges as an alternative to conventional microbicidal or microbiostatic systems, enabling numerous and successive applications without developing side effects and microbial resistance. In this context, an aPDI system against cultures of S. aureus based on a water-in-oil (W/O) emulsion incorporating curcumin as the photosensitizer (PS), with and without olive leaf extract (OLE), was developed and the antibacterial efficacy evaluated under LED activation (ʎ450 ± 10 nm) by depositing an energy density of 14 J/cm². The produced emulsified systems showed no significant differences in the droplet size and morphology, remaining stable along the tested period of 30 days. The bacterial reduction achieved after the first aPDI application for the emulsions added with curcumin and curcumin combined with the OLE was 5 log10 CFU.mL^-1 and 6 log10 CFU.mL^-1, respectively, revealing a significant difference between the two groups (p < 0.0001). After the second aPDI application, an increased microbial reduction (7 log10 CFU.mL^-1) was observed for both studied groups even with a low significant difference (p < 0.05). The PS loading through an emulsified system for aPDI obtained a bactericidal action against S. aureus, increased by applying two aPDI, showing a significant synergy between photodynamic inactivation, OLE delivery and antibacterial activity. In addition, the developed solutions were produced using natural products by an ecologically correct process.

Low curcumin concentrations combined with blue light inhibits cutibacterium acnes biofilm-induced inflammatory response through suppressing MAPK and NF-κB in keratinocytes

BACKGROUND

Curcumin has been employed as a photosensitizer agent during photodynamic therapy (PDT). Cutibacterium acnes (C. acnes) can cause an inflammatory response in human keratinocytes; however, no research has been conducted to determine whether curcumin and its photodynamic properties can prevent this inflammatory reaction.

OBJECTIVE

We hypothesized that curcumin may control the C. acnes biofilm-induced inflammatory response in keratinocytes, either alone or in combination with blue light photodynamic therapy.

METHODS

Following C. acnes biofilm stimulation, human primary keratinocytes were treated with 20 μM curcumin solution alone or 5 μM curcumin with combined blue light irradiation. The amount of secreted protein was measured using an ELISA kit. The expression levels of Toll-like receptor 2 (TLR2) and its downstream proteins were determined using western blot.

RESULTS

Treatment with 20 μM curcumin, but not 5 μM curcumin, reduced the inflammatory response to C. acnes biofilms in keratinocytes by blocking the TLR2/MAPK/NF-κB pathway. Interestingly, 5 μM curcumin combined with blue light also reduced the C. acnes biofilm-induced inflammation indicated above by blocking the TLR2/MAPK/NF-κB pathway.

CONCLUSION

Curcumin alone, in sufficient concentrations, or low-concentration curcumin with blue light had anti-inflammatory activity on keratinocytes stimulated by C. acnes biofilms through inhibition of MAPK and NF-κB signaling pathways by downregulating TLR2 expression.

Methylene Blue-Mediated Antimicrobial ​Photodynamic Therapy Against Clinical Isolates of Extensively Drug Resistant ​Gram-Negative Bacteria Causing Nosocomial Infections in Thailand, An In Vitro Study

BACKGROUND/PURPOSE

Some multidrug-resistant gram-negative bacteria as a global threat have been recently prioritized for research and development of new treatments. We studied the efficacy of methylene blue-mediated antimicrobial photodynamic therapy (MB-aPDT) for the reduction of extensively drug-resistant Acinetobacter baumannii (XDR-AB) and Pseudomonas aeruginosa (XDR-PS) and multidrug-resistant Klebsiella pneumoniae (MDR-KP) isolated in a university hospital setting in Thailand.

METHOD

Two isolates of each selected bacterium were collected, XDR-AB1 and AB2, XDR- PS1 and PS2, and MDR-KP1 and KP2. Three triplicate experiments using various MB concentrations alone, various red light fluences alone, as well as the selected non-toxic doses of MB and fluences of red light combined as MB-aPDT were applied on each selected isolate. The colonies were counted [colony forming units (CFU)/ml]. Estimation of the lethal treatment dose defined as reduction of > 2 log₁₀ in CFU/ml compared with untreated bacteria.

RESULT

There were generally negligible changes in the viable counts of the bacterial suspensions treated with all the MB concentrations (p > 0.05). In the second experiment with the only red light treatments, at fluences higher than 2 J/cm, reduction trend in viable counts across all the isolates was observed. Only for MDR-KP1, however, the lethal dose was achieved with the highest fluence of red light (80 J/cm). With the concentration of MB, 50 and 150 mg/L in the third experiment (MB-aPDT), the greater bacterial reduction was observed in all clinical isolates leading to their lethal viable cell reduction when escalating the light fluence to 80 J/cm.

CONCLUSIONS

MB-aPDT evidently killed the selected XDR and MDR-gram negative bacteria. In highly drug-resistant crisis era, MB-aPDT could be a promising option, particularly for local infections and infection complicating chronic wounds.

Antimicrobial Effect of Phytochemicals from Edible Plants

Current strategies of combating bacterial infections are limited and involve the use of antibiotics and preservatives. Each of these agents has generally inadequate efficacy and a number of serious adverse effects. Thus, there is an urgent need for new antimicrobial drugs and food preservatives with higher efficacy and lower toxicity. Edible plants have been used in medicine since ancient times and are well known for their successful antimicrobial activity. Often photosensitizers are present in many edible plants; they could be a promising source for a new generation of drugs and food preservatives. The use of photodynamic therapy allows enhancement of antimicrobial properties in plant photosensitizers. The purpose of this review is to present the verified data on the antimicrobial activities of photodynamic phytochemicals in edible species of the world’s flora, including the various mechanisms of their actions.

Interplay of phosphate and carbonate ions with flavin photosensitizers in photodynamic inactivation of bacteria

Photodynamic inactivation (PDI) of pathogenic bacteria is a promising technology in different applications. Thereby, a photosensitizer (PS) absorbs visible light and transfers the energy to oxygen yielding reactive oxygen species (ROS). The produced ROS are then capable of killing microorganisms via oxidative damage of cellular constituents. Among other PS, some flavins are capable of producing ROS and cationic flavins are already successfully applied in PDI. When PDI is used for example on tap water, PS like flavins will encounter various ions and other small organic molecules which might hamper the efficacy of PDI. Thus, the impact of carbonate and phosphate ions on PDI using two different cationic flavins (FLASH-02a, FLASH-06a) was investigated using Staphylococcus aureus and Pseudomonas aeruginosa as model organisms. Both were inactivated in vitro at a low light exposure of 0.72 J cm-2. Upon irradiation, FLASH-02a reacts to single substances in the presence of carbonate or phosphate, whereas the photochemical reaction for FLASH-06a was more unspecific. DPBF-assays indicated that carbonate and phosphate ions decreased the generation of singlet oxygen of both flavins. Both microorganisms could be easily inactivated by at least one PS with up to 6 log10 steps of cell counts in low ion concentrations. Using the constant radiation exposure of 0.72 J cm-2, the inactivation efficacy decreased somewhat at medium ion concentrations but reached almost zero for high ion concentrations. Depending on the application of PDI, the presence of carbonate and phosphate ions is unavoidable. Only upon light irradiation such ions may attack the PS molecule and reduce the efficacy of PDI. Our results indicate concentrations for carbonate and phosphate, in which PDI can still lead to efficient reduction of bacterial cells when using flavin based PS.

Efficient Photodynamic Killing of Gram-Positive Bacteria by Synthetic Curcuminoids

In our previous study, we have demonstrated that curcumin can efficiently kill the anaerobic bacterium Propionibacterium acnes by irradiation with low-dose blue light. The curcuminoids present in natural plant turmeric mainly include curcumin, demethoxycurcumin, and bisdemethoxycurcumin. However, only curcumin is commercially available. Eighteen different curcumin analogs, including demethoxycurcumin and bisdemethoxycurcumin, were synthesized in this study. Their antibacterial activity against Gram-positive aerobic bacteria Staphylococcus aureus and Staphylococcus epidermidis was investigated using the photodynamic inactivation method. Among the three compounds in turmeric, curcumin activity is the weakest, and bisdemethoxycurcumin possesses the strongest activity. However, two synthetic compounds, (1E,6E)-1,7-bis(5-methylthiophen-2-yl)hepta-1,6-diene-3,5-dione and (1E,6E)-1,7-di(thiophen-2-yl)hepta-1,6-diene-3,5-dione, possess the best antibacterial activity among all compounds examined in this study. Their chemical stability is also better than that of bisdemethoxycurcumin, and thus has potential for future clinical applications.

Antimicrobial Photoinactivation Approach Based on Natural Agents for Control of Bacteria Biofilms in Spacecraft

A spacecraft is a confined system that is inhabited by a changing microbial consortium, mostly originating from life-supporting devices, equipment collected in pre-flight conditions, and crewmembers. Continuous monitoring of the spacecraft’s bioburden employing culture-based and molecular methods has shown the prevalence of various taxa, with human skin-associated microorganisms making a substantial contribution to the spacecraft microbiome. Microorganisms in spacecraft can prosper not only in planktonic growth mode but can also form more resilient biofilms that pose a higher risk to crewmembers’ health and the material integrity of the spacecraft’s equipment. Moreover, bacterial biofilms in space conditions are characterized by faster formation and acquisition of resistance to chemical and physical effects than under the same conditions on Earth, making most decontamination methods unsafe. There is currently no reported method available to combat biofilm formation in space effectively and safely. However, antibacterial photodynamic inactivation based on natural photosensitizers, which is reviewed in this work, seems to be a promising method.

Evidence of hypericin photoinactivation of E. faecalis: From planktonic culture to mammalian cells selectivity up to biofilm disruption

Antimicrobial Photodynamic Therapy (aPDT) is an alternative for microbiological inactivation. The aPDT is a method that uses a photosensitizer (PS) excited by visible light at the appropriate wavelength and the molecular oxygen present in the tissues resulting in the production of reactive oxygen species, which causes oxidative damage to biological molecules. This study aimed to perform an in vitro experimental sequence for photoinactivation of E. faecalis using Hypericin (HY) from planktonic culture to selectivity assays using mammalian cells up to biofilm. The results show that E. faecalis rapidly absorb HY. The levels of inactivation of E. faecalis reached up to 99% in planktonic culture. Transmission and Scanning Electron Microscopy demonstrate the remarkable morphological alterations resulting from photooxidation being the loss of membrane integrity assessed by fluorescence microscopy combined with a LIVE/DEAD™ kit. HY did not present cytotoxicity to the fibroblasts cell at the used conditions proving to be a selective molecule. Finally, 60% of photoinactivation was observed in the biofilm of E. faecalis when subject to HY-aPDT. These outcomes show the advantages of sequential in vitro experiments besides showing that HY is a potential PS for clinical trials due to its selectivity and photodynamic effect. This study also draws attention to the benefits of using methodologies that can evidence the antimicrobial effect beyond the typical constellation of cell death.

Inactivation of microbes on fruit surfaces using photodynamic therapy and its influence on the postharvest shelf-life of fruits

In this study, the disinfection effect of curcumin-mediated photodynamic therapy on the contact surfaces of fresh fruit was investigated. Our results showed that the optimum concentration of curcumin and the energy density required were 0.5 μM and 7.2 J/cm², respectively. Photodynamic therapy showed an excellent disinfection rate for the fresh fruits with a reduction of more than 80% in the total bacteria and coliform counts. The photodynamic therapy inhibited species that belonged to the categories of gram-negative and facultative anaerobic bacteria, except for two species of the Trichoderma fungus. Importantly, photodynamic therapy prolonged the shelf-life of grapes for two days at room temperature. Therefore, photodynamic therapy should be commercialized as a high efficiency and non-thermal sterilization technology for use in the food industry.

Identification of carbonylated proteins in a bactericidal process induced by curcumin with blue light irradiation on imipenem-resistant Acinetobacter baumannii

RATIONALE

Antimicrobial photodynamic treatment is potentially an alternative to antibiotics and is also effective against viruses, fungi and some cancers. Our previous studies have shown that blue light combined with curcumin, a chemical from the turmeric plant, exerted effective antimicrobial activity via photodynamic treatment. The study reported in this paper investigates which target proteins are affected after the treatment.

METHODS

We treated imipenem-resistant Acinetobacter baumannii with blue light and curcumin and used protein carbonylation as a marker for oxidative damage. After treatment, the bacterial proteins were extracted and the protein carbonyls marked using dinitrophenylhydrazide. After enzyme digestion, we used liquid chromatography/nano-electrospray ionization (LC/nano-ESI) ion trap mass spectrometry to identify bacterial peptides from a customized database. The functional enrichment analyses of the identified proteins were performed using gene ontology annotation and the STRING protein-protein interaction network.

RESULTS

The application of curcumin with blue light showed good antibacterial activity against imipenem-resistant A. baumannii. Using a shotgun proteomics approach, the carbonylated proteins in A. baumannii caused by the photolytic curcumin were identified. The results showed that the proteins related to membrane structures, translation and response to oxidative stress were preferentially modified.

CONCLUSIONS

The photolytic curcumin treatment could be a potential alternative to antibiotics for bacterial infection. In this study, the shotgun proteomics strategy allows us to explore the possible bactericidal mechanisms under this oxidative stress. The result provides a reference for future studies on the enhancement of the action of photolytic curcumin.

Acne Vulgaris: A Patient and Physician's Experience

In this article, the first coauthor, a young woman with acne vulgaris, shares her experience with the condition; she not only describes the clinical presentation and the eventual successful treatment of her acne, but also the emotional consequences that this skin disorder caused. The second coauthor, the patient's dermatologist, reviews some of the features of acne vulgaris: morphologic manifestations, pathogenesis, and treatment options. He also summarizes the patient's response to isotretinoin therapy. In addition, he reveals his subsequent enlightenment regarding the acne-related non-dermatologic effects that the patient experienced and the significant improvement of her self-image that occurred following the successful treatment of her acne.

Potential of Curcumin in Skin Disorders

Curcumin is a compound isolated from turmeric, a plant known for its medicinal use. Recently, there is a growing interest in the medical community in identifying novel, low-cost, safe molecules that may be used in the treatment of inflammatory and neoplastic diseases. An increasing amount of evidence suggests that curcumin may represent an effective agent in the treatment of several skin conditions. We examined the most relevant in vitro and in vivo studies published to date regarding the use of curcumin in inflammatory, neoplastic, and infectious skin diseases, providing information on its bioavailability and safety profile. Moreover, we performed a computational analysis about curcumin's interaction towards the major enzymatic targets identified in the literature. Our results suggest that curcumin may represent a low-cost, well-tolerated, effective agent in the treatment of skin diseases. However, bypass of limitations of its in vivo use (low oral bioavailability, metabolism) is essential in order to conduct larger clinical trials that could confirm these observations. The possible use of curcumin in combination with traditional drugs and the formulations of novel delivery systems represent a very promising field for future applicative research.

Antimicrobial Photodynamic Therapy Protocols on Streptococcus mutans with Different Combinations of Wavelengths and Photosensitizing Dyes

The aim of the study is to test the application of different laser wavelengths, with and without different photosensitizing dyes on different types of cultures. Laser irradiation was realized on Streptococcus mutans in both solid and liquid culture media in continuous mode at three different fluences (10, 20, and 30 J/cm2) with a red diode (650 nm) with toluidine blue dye, a blue-violet diode (405 nm) with curcumin dye, and a green diode (532 nm) with erythrosine dye. Without a photosensitizer, no growth inhibition was obtained with the red diode at any fluence value. Inhibition rates of 40.7% and 40.2% were obtained with the blue diode and green diode. The blue diode laser used with curcumin obtained results in terms of growth inhibition up to 99.26% at a fluence of 30 J/cm2. The red diode laser used with toluidine blue obtained results in terms of growth inhibition up to 100% at fluences of 20 and 30 J/cm2. The KTP (potassium-titanyl-phosphate) laser used with erythrosine was able to determine a complete growth inhibition (100%) at the different fluence values. The combination of a laser and its proper color may dramatically change the results in terms of bactericidal effect. It will be interesting to confirm these data by further in vivo studies.

Biological properties of metal complexes of curcumin

Curcumin, a naturally occurring phenolic compound isolated from Curcuma longa, has different pharmacological effects, including antiinflammatory, antimicrobial, antioxidant, and anticancer properties. However, curcumin has been found to have a limited bioavailability because of its hydrophobic nature, low-intestinal absorption, and rapid metabolism. Therefore, there is a need for enhancing the bioavailability and its solubility in water in order to increase the pharmacological effects of this bioactive compound. One strategy is curcumin complexation with transition metals to circumvent the abovementioned problems. Curcumin can undergo chelation with various metal ions to form metallo-complexes of curcumin, which may show greater effects as compared with curcumin alone. Promising results with metal curcumin complexes have been observed with regard to antioxidant, anticancer, and antimicrobial activity, as well as in treatment of Alzheimer's disease. The present review provides a concise summary of the characterization and biological properties of curcumin-metal complexes. © 2019 BioFactors, 45(3):304-317, 2019.