Photodynamic inactivation of foodborne bacteria by eosin Y.

AIMS: The aim of this study was evaluate the effect of photodynamic inactivation mediated by eosin Y in Salmonella enterica serotype Typhimurium ATCC 14028, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778. METHODS AND RESULTS: Bacteria (107 CFU per ml) were incubated with eosin Y at concentrations ranging from 0·1 to 10 µmol l-1 , irradiated by green LED (λmax 490-570 nm) for 5, 10 and 15 min and the cellular viability was determined. Pseudomonas aeruginosa was completely inactivated when treated with 10 µmol l-1 eosin Y for 10 min. Treatments reduced B. cereus and Salm. Typhimurium counts to 2·7 log CFU per ml and 1·7 log CFU per ml, respectively. Escherichia coli counts were slightly reduced. Staphylococcus aureus presented the highest sensitivity, being completely inactivated by eosin Y at 5 µmol l-1 and 5 min of illumination. The reduction of cellular viability of photoinactivated Staph. aureus was also demonstrated by flow cytometry and morphological changes were observed by scanning electron microscopy. CONCLUSIONS: Eosin Y in combination with LED produced bacterial inactivation, being a potential candidate for photodynamic inactivation. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evidenced the efficacy of photodynamic inactivation as a novel and promising alternative to bacterial control.

Phototoxic effect of aluminium-chlorine and aluminium-hydroxide phthalocyanines on Leishmania (l.) amazonensis.

This study investigated the activity of photosensitive phthalocyanines on promastigotes and amastigotes of Leishmania (L.) amazonensis. Aluminum phthalocyanine chloride (AlPcCl), Aluminum phthalocyanine hydroxide (AlPcOH) and zinc phthalocyanine (PcZn) were tested in the presence (matte red LED, potency of 2.5-2.3 µW for 30 min) and absence of light against L. amazonensis promastigotes and the parasite viability was evaluated after 24, 48 and 72 h. The amastigote forms were treated with AlPcCl and AlPcOH, following the same lighting protocols described for the promastigote forms, being evaluated after 24 h. Cytotoxicity to human erythrocytes and peritoneal macrophages was also evaluated. The results showed that AlPcCl and AlPcOH in the presence of light have antileishmania activity, with leishmanistatic effects on promastigotes and amastigotes of L. amazonensis, without causing cytotoxicity to peritoneal macrophages and erythrocytes. The concentrations that inhibited 50% of the promastigote forms after 24 h of light exposure were 0.21 ±â€¯0.08 µM for AlPcCl and 0.23 ±â€¯0.06 µM for AlPcOH. In 48 h and 72 h after the treatment, the IC50 of AlPcCl was 0.13 ±â€¯0.02 and 0.12 ±â€¯0.03 µM and for AlPcOH was 0.14 ±â€¯0.01 µM and 0.11 ±â€¯0.01 µM, respectively. PcZn showed no activity on promastigotes of L. amazonensis. This study showed a substantial photodynamic activity of the phthalocyanines AlPcCl and AlPcOH against intracellular amastigotes forms of L. amazonensis after irradiation, presenting IC50 values of 0.62 ±â€¯0.06 µM and 0.92 ±â€¯0.12 µM, respectively. These results support the possibility of using photodynamic therapy for the treatment of cutaneous leishmaniasis.

Rose Bengal incorporated in mesostructured silica nanoparticles: structural characterization, theoretical modeling and singlet oxygen delivery.

Rose Bengal (RB), a xanthene dye, incorporated into mesostructured silica nanoparticles (MSNs) exhibits efficient singlet oxygen ((1)O2) generation when illuminated with 540 nm green light which is particularly promising for PDT applications. Several systems with different RB loadings were synthesized and fully characterized by means of spectroscopic techniques in combination with a computational study, to optimize the amount of RB in order to avoid the formation of aggregates that is detrimental for a high (1)O2 delivery.