The interaction between water soluble quinoline substituted phthalocyanines (Pcs) 1Q and 2Q and BSA (bovine serum albumin) was investigated. The binding modes of 1Q and 2Q to BSA was investigated by UV-vis and fluorescence titration experiments. The quenching effect of Pcs 1Q and 2Q on the fluorescence of Acridine Orange (AO)-BSA complex was determined. The results indicated that these water soluble phthalocyanines (Pcs) can bind to BSA and can be transported in circulatory system. Water soluble nature of both Pcs enhances cellular uptake and these dyes can be used in photodynamic theraphy (PDT). (C) 2013 Elsevier B.V. All rights reserved.