Three　zinc(II)　phthalocyanines　substituted　with　sulfonated　quinolineoxy　groups,　including　the　mono-α-substituted　1,　tetra-α-substituted　3,　and　tetra-β-substituted　4　were　synthesized　and　characterized.　These　compounds　(in　deprotonated　form)　were　water-soluble　and　could　be　formulated　with　Cremophor　EL　or　phosphate　buffered　saline.　When　formulated　with　phosphate　buffered　saline,　the　serum　albumin　exerted　an　important　effect　on　the　aggregation　tendency　and　spectroscopic　properties　of　these　compounds　in　biological　media.　In　the　case　of　phosphate　buffered　saline　formulation,　the　photocytotoxicity　followed　the　order　3　＞　4　＞＞　1　for　both　human　colon　carcinoma　HT29　and　human　hepatocarcinoma　HepG2　cell　lines　as　a　result　of　their　different　aggregation　tendency.　Interestingly,　when　formulated　with　Cremophor　EL,　1　showed　the　highest　photocytotoxicity　not　only　due　to　its　highest　cellular　uptake　but　also　due　to　the　reduced　aggregation.　In　both　of　these　formulated　systems,　the　tetra-α-substituted　compound　3　exhibited　a　higher　potency　than　the　tetra-β-substituted　analogue　4.　©　2016　Elsevier　Ltd.