A novel technique of antimicrobial photodynamic therapy - aPDT using 1,9-dimethyl-methylene blue zinc chloride double salt-DMMB and polarized light on Staphylococcus aureus.

Antimicrobial Photodynamic Therapy (aPDT) is an alternative to conventional treatments of local infections such as the use of antibiotics, which may lead to the development of resistance. aPDT besides requiring the use of a photosensitiser also needs a light source do be carried out. In the search for efficient and low-cost procedure the use of multispectral polarized light (λ400-2000 nm) emerges as a possibility for the execution of aPDT. The use of a highly effective photosensitizer is also of great importance. 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt - DMMB is a potent phenothiazine derivative that presents high photodynamic action due to its high lipophilicity as well as a greater quantum yield of Singlet oxygen and phototoxicity when compared to other Photosensitizers. The aim of this study was to assess, In Vitro, the efficacy of aPDT on Staphylococcus aureus (ATCC 25923) using different concentrations of DMMB associated to a Polarized light source (Bioptron®, 40 mW, ᴓ = 15.8 cm2) using different energy densities. Based on the IC50, 150 and 300 ng/mL of DMMB concentrations were chosen for this study. Twelve experimental groups were used: (Control, PLs, PSs and aPDTs). Serial dilutions (up to 10-8) of the bacterial inoculum were used and the DMMB was added using the two previously determined concentrations. After 5 min of preincubation the dilutions of the inoculum were illuminated by the polarized light source. Subsequently, 100 µL of each dilution, in triplicate, were inoculated into Petri dishes containing TSA medium and incubated in a bacteriological oven at 37 °C for 24-h and quantification of UFCs was done. The results showed significant exponential reduction (p < .0001) of 99.93% (150 ng/mL + LP 10 J/cm2) and 99.97% (300 ng/mL + LP 5 J/cm2) the CFU counts in comparison to non-illuminated control. The results of this study allow to conclude that aPDT carried out with 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt-DMMB and a PL souce was efficacious on the reduction (99.97%), in vitro, of the bacterial counts of S. aureus.

aPDT using nanoconcentration of 1,9-dimethylmethylene blue associated to red light is efficacious in killing Enterococcus faecalis ATCC 29212 in vitro.

The Enterococcus faecalis is a microorganism that causes multiple forms of resistance to a wide range of drugs used clinically. aPDT is a technique in which a visible light activates photosensitizer (PS), resulting in generation of reactive oxygen species that kill bacteria unselectively via an oxidative burst. aPDT is an alternative to antibiotics with the advantage of not causing resistance. The search for an alternative treatment of infections caused by E. faecalis, without using antibiotics, is off great clinical importance. The aim of present investigation was to assess the efficacy of using 3.32 ηg/mL of 1,9-dimethylmethylene blue (DMMB) as photosensitizer associated with the use of either Laser (λ660 nm) or LED (λ632 ±â€¯2 nm) using different energy densities (6, 12 and 18 J/cm2) to kill E. faecalis in vitro. Under different experimental conditions, 14 study groups, in triplicate, were used to compare the efficacy of the aPDT carried out with either the laser or LED lights using different energy densities associated to DMMB. The most probable number method (MPN) was used for quantitative analysis. Photodynamic antimicrobial effectiveness was directly proportional to the energy density used, reaching at 18 J/cm2, 99.999998% reduction of the counts of E. faecalis using both light sources. The results of this study showed that the use of 3.32 ηg/mL of DMMB associated with the use 18 J/cm2 of LED light (λ632 ±â€¯2 nm) reduced >7-log counts of planktonic culture of E. faecalis.

Effects of photostimulation on the catabolic process of xenobiotics.

Light biotechnology is a promising tool for enhancing recalcitrant compounds biodegradation. Xenobiotics can cause a significant impact on the quality of the results achieved by sewage treatment systems due to their recalcitrance and toxicity. The optimization of bioremediation and industrial processes, aiming to increase efficiency and income is of great value. The aim of this study was to accelerate and optimize the hydrolysis of Remazol Brilliant Blue R by photo stimulating a thermophilic bacterial consortium. Three experimental groups were studied: control group; LED Group and Laser Group. The control group was exposed to the same conditions as the irradiated groups, except exposure to light. The samples were irradiated in Petri dishes with either a Laser device (λ660 nm, CW, θ = 0.04 cm2, 40 mW, 325 s, 13 J/cm2) or by a LED prototype (λ632 ±â€¯2 nm, CW, θ = 0.5 cm2, 145 mW, 44 s, 13 J/cm2). We found that, within 48-h, statistically significant differences were observed between the irradiated and the control groups in the production of RNA, proteins, as well as in the degradation of the RBBR. It is concluded that, both Laser and LED light irradiation caused increased cellular proliferation, protein production and metabolic activity, anticipating and increasing the catabolism of the RBBR. Being the economic viability a predominant aspect for industrial propose our results indicates that photo stimulation is a low-cost booster of bioprocesses.