Phthalocyanines Structure Versus Photodynamic Effectiveness towards Pathogenic Microorganisms: Our Recent Experience

The present review paper aims to summarize our recent experience in research and development of new phthalocyanine complexes and investigations of the main photophysical, photochemical and photobiological properties which are related to antimicrobial photodynamic therapy (aPDT) as alternative method for inactivation of the resistant pathogens. The effect of functionalization of Zn(II) phthalocyanine (ZnPc) with biologically-active natural substances such as amino acids, sugars and steroids was studied in comparison to the basic ZnPc ring molecule. The structural features of the substitution groups were chosen to facilitate the main properties responsible for PDT outcome. For example, the linkage groups of amino acids tyrosine, phenylalanine, lysine and arginine have positive charge in physiological media to the better attachment to bacterial wall and some of them have a good fluorescence for a contribution to the visualization of the infected area. Also, ZnPcs linked to sugars and steroids was expecting to possess receptor specific selectivity. The physicochemical properties of the novel functionalized ZnPcs are presented in respect to their efficiency for a number of pathogenic bacterial and fungal species. Additionally, the complexes of two heavy metal ions such as lutetium(III) (Lu(III)) and tin(IV) (Sn(IV)) were synthesized and evaluated for antimicrobial PDT. These complexes were designed with the same structural skeleton as our previous water-soluble methylpiridyloxy-substituted phthalocyanine complexes with zinc (II), silicon (IV), germanium (IV), indium (III) and gallium (III), all with relatively promising antibacterial efficiency.