Photodynamic efficacy of water-soluble Si(IV) and Ge(IV) phthalocyanines towards Candida albicans planktonic and biofilm cultures

Water-soluble phthalocyanine complexes of silicon (SiPc1) and germanium (GePc1) were synthesized. The absorbance of SiPc1 in water was with minor aggregation while GePc1 strongly aggregated in water. The fluorescence data in water showed low quantum yields of 0.073 (SiPc1) and 0.01 (GePc1) and similar lifetimes of 4.07 ns and 4.27 ns. The uptake of SiPc1 into Candida albicans cells was two orders of magnitude lower as compared to GePc1 and for both was dependent on the cell density. Fungal cells in suspension were completely inactivated after SiPc1 (1.8 μM) at soft light radiation (50 J cm−2, 60 mW cm−2). The fungal biofilm formed on denture acrylic resin was inactivated with 3 log after fractionated light irradiation.

Graphical abstractWater-soluble SiPc1 shows potential value for inactivation of 48 h fungal biofilm grown on denture acrylic resin only after fractioned light radiation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of methylpyridyloxy-substituted Si(IV)- and Ge(IV)-phthalocyanines. ► Quaternized Si(IV)-phthalocyanine has low aggregation in water and high PDT effect. ► Quaternized Ge(IV)-phthalocyanine aggregates strongly and has slight PDT effect. ► Diffusion of phthalocyanines into Candida albicans biofilm is ∼75% of full thickness. ► Inactivation of biofilm is possible (3 log) after fractioned light irradiation.