Treatment of microbiologically polluted aquaculture waters by a novel photochemical technique of potentially low environmental impact

Abstract

The applicability of a novel procedure for the disinfection of microbiologically polluted waters from fish-farming ponds, based on the combined action of visible light (including sunlight) and porphyrin-type photosensitising agents, has been investigated using (a) cell cultures of a Gram-positive bacterium (meticillin-resistant Staphylococcus aureus), a Gram-negative bacterium (Escherichia coli) and a fungal pathogen (Saprolegnia spp.); (b) pilot aquaculture plants involving either spontaneously or artificially Saprolegnia-infected rainbow trout (Oncorhynchus mykiss). The results obtained by using two cationic porphyrins, namely a tetra-substituted N-methyl-pyridyl-porphine (C1) and its analogue where one N-methyl group had been replaced by a N-tetradecyl chain (C14), and low intensity visible light irradiation showed an extensive (up to 6-7 log) decrease in the bacterial/fungal population after short incubation and irradiation times in the presence of micromolar photosensitiser concentrations. Moreover, C14 showed some toxic effect also in the absence of light. Extension of these studies to the pilot plants indicated that both C1 + light and C14 can prevent Saprolegnia infections or promote the cure of saprolegniasis in infected trout by treatments with submicromolar porphyrin doses. The procedure appears to be of low cost and to have a low environmental impact.

Potential applications of porphyrins in photodynamic inactivation beyond the medical scope

“…Experiments with Saprolegnia (≈10 8 zoospores mL −1 ), indicated that Tri-Py + -C 14 -Py + -Me caused a decrease of the survival of the fungal cells by about 6 logs, after phototreatment with 10 M [81]. The preventive protocol determined a reduction of the infected percentage to 10% and 13%, respectively, after one week, with irradiated Tetra-Py + -Me and unirradiated Tri-Py + -C 14 -Py + -Me, respectively.…”

“…No [47] No [50,52,69] On filter paper [82] On cotton fabric [86,108] On polysilsesquioxane plastic films [61] On cotton fabric [87] On azide-modified cellulose nanocrystals [43,75] On chloroacetyl cellulose ester chlorides [78] On cellulose laurate esters plastic films [79] No [71] No [93] No [49,71,93,110] and Tri-Py + -Me-PF on silica coated Fe3O4 nanoparticles [70] and also on CoFe2O4 nanoparticles [111] No [81] No [105] No [36,37,71,74,81,105]; Tetra-Py + -Me was entrapped into microporous silica gels [88] and into three alkylene-bridged polysilsesquioxanes [89] On optically transparent indium tin oxide electrodes [63] On chitosan membranes [72] Pd(II) TetraTPPCO2H On a polyurethane matrix [83] No [105] In hydrophilic polycaprolactone and polyurethane (TecophilicH) nanofibers [60]; on electrospun polymeric nanofiber materials polyurethane Larithane TM , polystyrene, polycaprolactone, and polyamide 6 [76]; into three alkylene-bridged polysilsesquioxanes [89]; and in a silica-gel supported antimony porphyrin complex SbTPP [97,98] No [44,…”

“…The photodynamic disinfection of water from fish farms as well as the prevention and treatment of localized fungal infections (saprolegniosis) in fish, with porphyrins as photosensitizing agents, was presented in 2006, demonstrating the inactivation in vitro of pathogenic fungi and bacteria, and the photo-treatment of spontaneously or artificially infected fish in a pilot aquaculture pond [81]. The PS chosen were Tetra-Py + -Me and Tri-Py + -C 14 -Py + -Me (0.05-10 M).…”

“…The incubation and irradiation treatment was repeated daily, for ten consecutive days, starting from the first day after the infection. In the curative protocol, infected fish were dark incubated with 0.44 M Tetra-Py + -Me for 10 min in an 80 L pool, irradiated for 1 h and moved to a 1000 L tank (treatment repeated daily for six consecutive days); or dark incubated with 0.4 M of Tri-Py + -C 14 -Py + -Me for 24 h in a 150 L tank, not irradiated and then moved to a 1000 L tank [81].…”

Effect of Molecular Characteristics on Cellular Uptake, Subcellular Localization, and Phototoxicity of Zn(II) N-Alkylpyridylporphyrins

“…Approved initially for the treatment of a small number of selected tumors (1), it has expanded to encompass a wide range of applications in dermatology (2,3), ophthalmology (4,5), dentistry (6,7), cardiology (8,9), cosmetics (10,11), blood purification (12), and water disinfection (13,14).…”