A photobleaching resistant polymer supported hexanuclear molybdenum iodide cluster for photocatalytic oxygenations and photodynamic inactivation of Staphylococcus aureus

Abstract

The ability of hexanuclear molybdenum cluster [Mo 6 I 8 (CH 3 COO) 6 ] 2to carry out, upon irradiation, singlet oxygen mediated photocatalytic oxygenation reactions has been tested. This complex has been also supported onto a solid polymeric matrix, yielding an immobilized photosensitizer with remarkable photostability and recyclability. Preliminary studies of antibacterial photoinactivation of Staphylococcus aureus have been conducted, with positive results.Photosensitization to produce reactive oxygen species (ROS) is widely used in a variety of fields, from photocatalysis to photodynamic therapy of cancer and photodynamic inactivation of microorganisms. In the first area, production of fine chemicals can be achieved by means of photocatalysed oxygenation reactions. 1 In the second realm, treatment of tumours or inactivation of bacteria can be done by the appropriate choice of photosensitizer and irradiation conditions. 2 For any application the requisite of photostability is of key importance and great effort is devoted to the development of photosensitizers resistant to the self-generated ROS species. 3 An outstanding library of photocatalytic and photodynamic agents has been developed so far. 4 Hexanuclear clusters of molybdenum [Mo 6 X 8 L 6 ] (X = Cl, Br, I; L is a ligand) are well known photochemical generators of singlet oxygen ( 1 O 2 ). 5

Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials

“…1@P mp is more effective for the eradication of S.aureus than 1@P gel as it can be seen in Figure 2. At a light dose of 110 J/cm 2 the decrease in S.aureus population photoinduced by macroporous 1@P mp was 8 log units 23 of colony forming units (CFU) (hence 99.999999% killing). At the same dose, the reduction caused by gel-type 1@P gel is only about 4 log units.…”

“…Supported photosensitizers (1@P gel and 1@P mp ) were prepared easily via chloride exchange by the dianionic complex 1 and isolated by filtration, as described earlier (final loading: 0.74 µmol of 1/g of polymer). 23 The visual appearance of 1@P gel is translucent whereas 1@P mp is opaque, suggesting a different interaction with light (much different refraction index; see Figure 1b). Diffuse reflectance spectra of both materials showed unequivocally the presence of 1 (signal at ca.…”

“…In our preliminary communication only one type of polymer (P mp ) and one strain of bacteria (S.aureus) were tested, and the objective of the research was to check the ability of supported 1 to generate cytotoxic 1 O 2 . 23 Here we focus our attention on deciphering the role of the organic polymeric matrix in the antimicrobial activity. As it will be shown in the following lines, the solid support is a variable that critically matters and hence must be taken into account in the development of effective photobactericidal materials.…”

“…21 Among those molecules, xanthenic dyes, phenothiazinium compounds, porphyrins and phthalocyanins have been studied. 22 Recently we have proposed a hexanuclear molybdenum cluster complex (1: [Mo 6 I 8 Ac 6 ] 2-, Ac is acetate; see structure in Figure 1) as photoactive agent for aPDI, 23 owing to its notable photochemical properties. [24][25][26][27][28][29][30][31][32][33][34][35] Regarding the supports for the photoactive agents, a variety of materials have been described in the literature, like polyurethane, cellulose, nylon, chitosan, silica and polystyrene.…”

Luminescent coordination polymers based on Ca2+ and octahedral cluster anions [{M6Cli8}Cla6]2− (M = Mo, W): synthesis and thermal stability studies

“…Indeed, depending on X and L, some members of this family demonstrate intensive luminescence in the red/near-infrared region with emission lifetimes of hundreds of microseconds and often with significant quantum yields. [11][12][13][14][15][16][17] Due to these properties, materials based on these clusters have been demonstrated to have potential in solar energy harvesting, 18,19 bioimaging, photodynamic therapy, [20][21][22] photo-catalysis, [23][24][25][26][27] oxygen sensing, [28][29][30][31] lighting, [32][33][34] etc.…”