IMBIV   05474
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA VEGETAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
LIPID OXIDATION IN BACTERIA TREATED WITH PHOTODYNAMIC ANTIBACTERIAL CHEMOTHERAPY USING GOLD NANOPARTICLES
Autor/es:
M. JAZMÍN SILVERO; M. CECILIA BECERRA
Lugar:
TUCUMAN
Reunión:
Congreso; III GRAFOB 2016; 2016
Resumen:
Alternatives to fight antibiotic resistance bacteria are certainly a major concern of our days. Photodynamic Antibacterial Chemotherapy (PACT) has emerged in the last decades as a treatment with a lot of potential against these pathogens. Particularly, PACT employing gold nanoparticles (AuNP) as photosensitizers has proved to be very effective, achieving complete inhibition of bacterial growth thought an irreversible oxidative stress provoked by a photothermal effect when exciting AuNP Plasmon with 525 nm LED. It is known that oxidative stress takes place when reactive oxygen species (ROS) increases to a level that exceeds the cell?s defense capacity. The biological targets for ROS are DNA, RNA, proteins and specially lipids. Free radicals can attack directly polyunsaturated fatty acids in membranes and decrease its fluidity, which alters the normal structure properties and can disrupt membrane-bound proteins significantly. This effect acts as an amplifier, more radicals are formed, and polyunsaturated fatty acids are degraded to a variety of products. Some of them, such as aldehydes, are very reactive and can damage molecules such as proteins.1 In a previous work, ROS production and protein damage has been reported after PACT with gold nanoparticles (AuNP)..2 In the present one, lipid oxidation was quantified kinetically for 24 h in three bacterial strains (Staphyloccocus aureus ATCC 29213, Escherichia coli ATCC 25922 and a clinical isolate of Pseudomonas aeruginosa a clinical isolate N4) using the highly sensitive fluorescent probe 5(6)-Carboxy-2′,7′-dichlorofluorescein. All samples were conducted by triplicate and SD calculated was never above 5%. The ATCC strains treated with AuNP and irradiated presented a large amount of oxidized lipids after only 4 h of PACT (967x and 7458x respect to non irradiated samples) for S. aureus and E. coli, respectively) and the maximal levels at 8 h (11981x and 9971x), while the clinical P. aeruginosa took 8 h to showed an important lipid peroxidation o reached the maximal level of lipid peroxidation at 8 h (6577x respect to non irradiated samples).In summary, significant lipid peroxidation was detected both in Gram negative bacillus (E. coli and P. aeruginosa) and in a Gram positive coccus (S. aureus). However, not all three of them presented the same amount of oxidized lipids. As expected, the trend found was S. aureus ˃ E. coli ˃ P. aeruginosa. These results, in addition to the advanced oxidation protein products reported previously, support the proposed mechanism for PACT with AuNP. According to this experimental data, bacterial death is caused as the result of macromolecular damage by large amounts of ROS produced after plasmon excitation of AuNP, which (according to TEM images) are either inside the cell or in its membrane.