Potential applications of porphyrins in photodynamic inactivation beyond the medical scope

Abstract

a b s t r a c tAlthough the discovery of light-activated antimicrobial agents had been reported in the 1900s, only more recently research work has been developed toward the use of photodynamic process as an alternative to more conventional methods of inactivation of micro(organisms). The photoprocess causes cell death through irreversible oxidative damage by reactive oxygen species produced by the interaction between a photosensitizing compound and a light source.With great emphasis on the environmental area, photodynamic inactivation (PDI) has been tested in insect eradication and in water disinfection. Lately, other studies have been carried out concerning its possible use in aquaculture waters or to the control of food-borne pathogens. Other potential applications of PDI in household, industrial and hospital settings have been considered.In the last decade, scientific research in this area has gained importance not only due to great developments in the field of materials chemistry but also because of the serious problem of the increasing number of bacterial species resistant to common antibiotics. In fact, the design of antimicrobial surfaces or selfcleaning materials is a very appealing idea from the economic, social and public health standpoints. Thus, PDI of micro(organisms) represents a promising alternative.In this review, the efforts made in the last decade in the investigation of PDI of (micro)organisms with potential applications beyond the medical field will be discussed, focusing on porphyrins, free or immobilized on solid supports, as photosensitizing agents.

Photodynamic inactivation of Escherichia coli with cationic meso-tetraarylporphyrins – The charge number and charge distribution effects

“…In this field a special attention is being given to metal-oxide materials like titanium dioxide (TiO 2 ), alone or doped with other noble metals such as silver, due to their chemical stability, photophysical properties and high efficiency to inactivate bacteria, moulds, and viruses [2][3][4][5][6][7]. Photoactive organic molecules, known as photosensitizers (PS), are also recognized to be effective against various microorganisms, including viruses, bacteria, yeasts, protozoa [8][9][10][11], and even drug-resistant strains [12][13][14][15][16][17], and microorganisms organized in biofilms [18,19]. This methodology, known as photodynamic inactivation of microorganisms (PDI), combines a non-toxic PS with visible light to generate singlet oxygen ( 1 O 2 ) and/or free radicals that kill the microorganisms.…”

Silica Gel–Supported P-, Ge-, and Sb-Porphyrins for Visible Light Inactivation of Bacteria

“…Recently, reviews on photoinactivation by water-soluble porphyrins have been published by Almeida at al. [20] and our group [32]. …”

“…Therefore, in our next study, we intended to inactivate bacteria using water-soluble porphyrins. Water-soluble porphyrins have received much attention in connection with photoinactivation [20] and photodynamic therapy (PDT) [21][22][23][24] ever since the first report on photoinactivation of E. coli by water-soluble meso-substituted cationic porphyrins appeared in 1996 [25]. For the biological application of porphyrins, water solubility is an important characteristic in the handling of porphyrins in an aqueous solution.…”

“…For the biological application of porphyrins, water solubility is an important characteristic in the handling of porphyrins in an aqueous solution. We modified the axial ligands of P and Sb porphyrins by installing alkyloxo (1) [26], alkylethylenedioxy (2) [27,28], and alkylpyridinium groups (3) [20,29] (Figure 14). The water solubility (C W in mM) is shown in Table 2.…”

Photodynamic Inactivation for Phatogenic Bacteria: Adding Chlorophyll and Oxygen

“…PDI therapy uses light and light-sensitive molecules that produce toxic molecules to reduce bacteria colony [4]. Light-sensitive molecules are termed as photosensitizer, the peak spectra of the photosensitizer must be in the range of the light sources.…”