Immobilization of Zinc Phthalocyanines in Silicate Matrices and Investigation of Their Photobactericidal Effect on E.coli

Abstract

The aim of the present investigation was to immobilize zinc phthalocyanines in a silicate matrix and to test the photobactericidal properties of the matrices so prepared toward Esherichia coli in model aqueous media. For the purpose, tetra tertiary butyl zinc phthalocyanine (TBZnPc) and zinc phthalocyanine tetrasulfonic acid (ZnPcTS) were used. The abilities of these two photosensitizers to generate singlet oxygen in solution were compared by following the rate of photobleaching of 1,3-diphenylisobenzofuran (DPBF) at 430 nm in dimethylformamide (DMF).The results of this study show clearly that, under the conditions used here, the TBZnPc is the more effective generator of singlet oxygen; with it the DPBF was virtually completely photobleached in 4 min, while with the ZnPcTS under the same conditions, it took 12 min to reach this point. Glass conjugates with the two phthalocyanines were obtained by the sol-gel technique and were characterized by a well-defined color due to the phthalocyanine incorporated in the silicate matrix. Glasses with an intense, but inhomogeneous, green color were obtained when the tetrasulfonic derivative of the zinc phthalocyanine was used, while blue glasses of evenly distributed coloration were formed from the tetra tertiary butyl derivative.The ZnPcTS conjugate demonstrates more effective singlet oxygen evolution than is the case with the TBZnPc conjugate. These results are the opposite of those obtained for the free phthalocyanines in solution. The structural formulae of the compounds show that TBZnPc has a more pronounced hydrophobic character than the sulfonic derivative. In our view, the relative reactivities of the conjugates can be explained by the tetrasulfonic derivative being situated mainly in the surface parts of the glass matrix where the hydrophilic character is prevailing, while the tertiary butyl derivative is mainly present in the internal parts of the matrix as a result of which it is less accessible and therefore less activeThe results obtained on the effect of zinc phthalocyanine conjugates on E. coli show a trend similar to that observed with singlet oxygen evolution shown. Thus, for the ZnPcTS conjugate, the log kill is 1.32 and for the TBZnPc conjugate, it is 0.98, in each case after 120 min. The results obtained show that phthalocyanines can be immobilized successfully in a silicate matrix and used for photodisinfection of microbially polluted waters. The silicate matrix has some advantages in comparison with other organic matrices. It is insoluble in water, resistant towards microorganisms, easy to fabricate, and might be developed successfully for the photodisinfection of water, e.g., in swimming pools and in other open water reservoirs.

Comparative study of singlet oxygen production by photosensitiser dyes encapsulated in silicone: towards rational design of anti-microbial surfaces

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Cationic dyes such as methylene blue or crystal violet are proven antimicrobial agents against both Gram-positive and Gram-negative bacteria. [8][9][10][11][12][13][14][15][16][17][18][19] Porphyrins and phthalocyanines are also used for photodynamic therapy (PDT) applications, however, although they have been successfully incorporated into polymers, [20][21][22] the procedure is non-trivial as compared to swell-encapsulation. Moreover, some porphyrins can be significantly more expensive than widely available dyes considered in the present study.…”

Phage Therapy and Photodynamic Therapy: Low Environmental Impact Approaches to Inactivate Microorganisms in Fish Farming Plants

“…As a consequence, some studies have developed PS immobilized on solid supports and the photodynamic inactivation (PI) against faecal bacteria was tested [232,275,277,281,282]. Bonnett et al used a phthalocyanine immobilized on a polymeric membrane of chitosan in a model reactor of water disinfection [281].…”

“…The extension of the photodynamic principle to a new environmentally-friendly technology can become economically viable if the PS is immobilized on a solid matrix in order to allow the photoinactivation process and subsequent retention of the PS, after photodynamic action, to avoid the release of the PS to the water output [ 277 , 281 ]. As a consequence, some studies have developed PS immobilized on solid supports and the photodynamic inactivation (PI) against faecal bacteria was tested [ 232 , 275 , 277 , 281 , 282 ]. Bonnett et al used a phthalocyanine immobilized on a polymeric membrane of chitosan in a model reactor of water disinfection [ 281 ].…”

“…The same group also immobilized zinc phthalocyanines in a silicate matrix to test their photobactericidal properties on E. coli in model aqueous media. Although they obtained moderate PI, they concluded that phthalocyanines can be immobilized successfully in a silicate matrix and also used for photodisinfection of microbially polluted waters [ 232 , 275 , 277 , 281 , 282 ]. Regenerated cellulose impregnated with 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra- p -tosylate showed photobactericidal activity against S. aureus , E. coli , Proteus vulgaris and Bacillus subtilis [ 275 ].…”